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Alterations in steroid hormone receptors in the tamoxifen-treated endometrium

      Abstract

      OBJECTIVE: Our purpose was to evaluate whether tamoxifen has estrogenic endometrial effects as defined by histologic study or alterations in steroid hormone receptor expression. STUDY DESIGN: Nineteen postmenopausal tamoxifen-treated breast cancer patients who also had endometrial sampling were identified from files in the Department of Obstetrics and Gynecology. To examine the subgroup of 15 polyps, age-matched, non–hormonally treated patients with polyps (n = 8) or atrophic endometria (n = 5) served as comparison groups. Proliferative (n = 3) and secretory (n = 5) endometria served as procedural controls. Immunohistochemical studies for steroid receptors (estrogen, progesterone) were performed. RESULTS: Glandular cell progesterone receptor was significantly increased and stromal cell estrogen receptor was significantly decreased in tamoxifen-treated versus atrophic endometria. Progesterone receptor staining was not significantly different in tamoxifen-treated versus control polyps, although staining was high in both groups. Stromal cell estrogen receptor staining was significantly reduced in tamoxifen-treated versus control polyps, although there were no histologic differences. Reduced stromal cell estrogen receptor and increased glandular cell progesterone receptor staining was found in all tamoxifen-treated endometria regardless of the diagnosis. CONCLUSION: The tamoxifen-associated changes in endometrial steroid receptors support an estrogenic effect that is independent of histologic diagnosis and duration of use. This may contribute to the pathogenesis of tamoxifen-associated polyps and carcinomas. (Am J Obstet Gynecol 1997;176:129-37.)

      Keywords

      The use of postoperative adjuvant tamoxifen therapy for postmenopausal breast cancer patients has been clearly shown to produce a significant improvement in both recurrence-free and overall survival.
      • Early Breast Cancer Trials Collaborative Group
      Effects of tamoxifen and of cytotoxic therapy on mortality in early breast cancer: an overview of 61 randomized trials among 28,896 women.
      Because tamoxifen is a nonsteroidal triphenylethylene-derived antiestrogen that binds to the estrogen receptor, it displays both estrogen antagonistic and agonistic properties, varying with the tissue on which it is acting. Although antiestrogenic on the breast,
      • Early Breast Cancer Trials Collaborative Group
      Effects of tamoxifen and of cytotoxic therapy on mortality in early breast cancer: an overview of 61 randomized trials among 28,896 women.
      tamoxifen has estrogenic effects on the bone and lipid profile.
      • Daniel Y
      • Inbar M
      • Bar-Am A
      • Peyser MR
      • Lessing JB
      The effects of tamoxifen treatment on the endometrium.
      There have been several clinical reports of endometrial hyperplasia and cancer in women treated with tamoxifen.
      • Forlander T
      • Cedermark B
      • Mattsson A
      • Skoog L
      • Theve T
      • Askergren J
      Adjuvant tamoxifen in early breast cancer: occurrence of new primary cancers.
      The Stockholm randomized placebo-controlled trial
      • Rutqvist LE
      • Cedermark B
      • Glas U
      The Stockholm trial on adjuvant tamoxifen in early breast cancer.
      showed that, although the number of second breast cancers was significantly decreased in the tamoxifen-treated group, by 5 years of tamoxifen use the overall risk for development of endometrial cancer was 6.4 times increased. Results of in vitro endometrial cell culture experiments
      • Anzai Y
      • Holinka CF
      • Kuramoto H
      • Gurpide E
      Stimulatory effects of 4-hydroxytamoxifen on proliferation of human endometrial adenocarcinoma cells (Ishikawa line).
      and animal studies
      • Gottardis MM
      • Robinson SP
      • Satyaswaroop PG
      • Jordan VC
      Contrasting actions of tamoxifen on endometrial and breast tumor growth in the athymic mouse.
      support the in vivo data.
      Although the mechanism of tamoxifen-induced endometrial neoplasia is thought to be through an estrogenic effect of tamoxifen, there are few data confirming this. Because sex steroid hormones regulate endometrial growth by interaction with their receptors (estrogen receptor and progesterone receptor), the current study is a clinicopathologic evaluation of whether these seemingly estrogenic-like actions of tamoxifen on the endometrium are associated with alterations in the expression of steroid receptors.

      Material and methods

      Data were retrospectively collected from files of the Division of Obstetric and Gynecologic Pathology at New York University Medical Center/Bellevue Hospitals and comprised 32 postmenopausal and 8 premenopausal patients. During a 2-year period we identified 19 postmenopausal women with breast cancer treated postoperatively with tamoxifen (10 mg twice daily). Human experimentation has been approved by our institutional review board committee.
      The mean number of years of tamoxifen use was 4.1 ± 0.7 (range 5 months to 9 years). The endometrial histologic diagnoses included 1 atrophic, 2 proliferative, 11 polyps, 4 polyps with adenocarcinoma, carcinoma in situ, hyperplasia, increased mitoses or atypia, and 1 adenocarcinoma. Because polyp formation was a common observation in tamoxifen-treated patients, we studied this group of 15 patients. Age-matched, non–hormonally treated patients with polyps (n = 8) and atrophic endometria (n = 5) served as comparison groups. Patients in these control groups did not have breast cancer. There were no significant differences in the mean age of patients with tamoxifen-treated (63.4 ± 2.0 years) versus control polyps (62.1 ± 2.7 years) or in the mean number of years after menopause (13.4 ± 2.0 vs 11.6 ± 2.9 years, respectively). There were no significant differences in mean age (p = 0.67) or number of years after menopause (p = 0.67) of the tamoxifen versus untreated atrophic endometrium groups (mean age 63.4 ± 2.0 vs 65.6 ± 5.7 years, and mean number of years after menopause 13.4 ± 2.0 vs 14.6 ± 5.7, respectively). Proliferative (n = 3) and secretory (n = 5) endometria served as positive procedural controls. The mean luteal phase endometrial dating was 23.4 ± 1.9 days.
      The indications for endometrial sampling for tamoxifen-treated patients included postmenopausal bleeding (8 patients), thickened endometrial echoes on transvaginal ultrasonography (10 patients), and one 71-year-old patient had an adnexal mass that was diagnosed as a fibrothecoma after she underwent a hysterectomy with bilateral oophorectomy. The presenting symptoms of the control polyp patients included “aborting” polyp (1 patient), postmenopausal bleeding (3 patients), prolapse (1 patient), adnexal mass (1 patient), pelvic pain (1 patient), and asymptomatic (1 patient). Two patients in the atrophic endometria group presented with uterine prolapse and 3 had benign adnexal masses. The types of procedures performed on the tamoxifen-treated group included a Pipelle endometrial biopsy for 3 patients, 13 had a hysteroscopy and curettage, 1 had a vaginal hysterectomy, and 2 had an abdominal hysterectomy. The control polyp patients underwent the following surgeries: hysteroscopy and curettage (6 patients), vaginal hysterectomy (1 patient), and abdominal hysterectomy (1 patient). For the atrophic endometria group 2 patients had vaginal hysterectomies and 3 had abdominal hysterectomies.
      Histologic features were compared between the polyps of tamoxifen-treated versus untreated patients by two investigators (including one pathologist, K.M.) blinded to treatment. The polyps were microscopically examined for classification (i.e., nonfunctional, proliferative, secretory), density of endometrial blood vessels (graded from 1+ to 3+), thickness of blood vessels (1+ to 3+, on the basis of the vessel with the largest diameter), presence of dilated cystic glands, type of metaplasia present, and stromal cellularity (1+ to 3+). Only one specimen had adjacent endometrium in addition to the polyp, and therefore that feature could not be assessed.
      Immunohistochemical examination was performed on all paraffin-embedded endometrial specimens for steroid receptor analysis, including estrogen (Daco) and progesterone receptors (Novocastra).
      • Mittal KR
      • Demopoulos RI
      • Goswami S
      Proliferating clee nuclear antigen (cyclin) expression in normal and abnormal cervical squamous epithelia.
      • Gold LI
      • Saxena B
      • Mittal KR
      • Goswami S
      • Nachtigall L
      • Kore M
      • et al.
      Increased expression of transforming growth factor B isoforms and basic fibroblast growth factor in complex hyperplasia and adenocarcinoma of the endometrium: evidence for paracrine and autocrine action.
      Both antibodies were diluted 1:50 and incubated overnight at 4° C. Indirect immunoperoxidase staining was performed by the avidin-biotin peroxidase technique
      • Mittal KR
      • Demopoulos RI
      • Goswami S
      Proliferating clee nuclear antigen (cyclin) expression in normal and abnormal cervical squamous epithelia.
      • Gold LI
      • Saxena B
      • Mittal KR
      • Goswami S
      • Nachtigall L
      • Kore M
      • et al.
      Increased expression of transforming growth factor B isoforms and basic fibroblast growth factor in complex hyperplasia and adenocarcinoma of the endometrium: evidence for paracrine and autocrine action.
      and counterstaining with hematoxylin. Endometria from eight premenopausal cycling patients (three proliferative and five luteal phase) were dated with the criteria of Noyes et al.
      • Noyes RW
      • Hertig DT
      • Rock J
      Dating the endometrial biopsy.
      Costaining of samples was performed to minimize staining variability. For negative controls, mouse ascitic fluid replaced estrogen and progesterone receptor antibodies.
      The percentage of glandular and stromal cells staining for estrogen or progesterone receptors was subjectively assessed to the nearest 5%. The intensity of staining was recorded on a scale of 0 to 4+, with 1+ as minimal and 4+ as intense staining. Quantitation was performed bymultiplying the percentage of positively stained cells by their staining intensity to generate a final immunohistochemical score.
      • Mittal KR
      • Demopoulos RI
      • Goswami S
      Proliferating clee nuclear antigen (cyclin) expression in normal and abnormal cervical squamous epithelia.
      • Gold LI
      • Saxena B
      • Mittal KR
      • Goswami S
      • Nachtigall L
      • Kore M
      • et al.
      Increased expression of transforming growth factor B isoforms and basic fibroblast growth factor in complex hyperplasia and adenocarcinoma of the endometrium: evidence for paracrine and autocrine action.
      Separate scores were generated for endometrial glands and stroma and also for endometrial vessels. Scoring was performed by four investigators blinded to treatment, including two pathologists (R.D. and K.M.). Data are expressed as means ± SEM and are statistically compared with the Student t test, with a level of significance at p < 0.05.

      Results

      Proliferative endometria had significantly higher glandular (p = 0.0034) and stromal (p = 0.0158) cell estrogen receptor immunohistochemical scores and significantly higher glandular (p = 0.0001) and stromal (p = 0.0158) cell progesterone receptor immunohistochemical scores compared with luteal phase endometria (Table I). This is consistent with elevated proliferative phase estradiol up-regulating its own estrogen and progesterone receptors and elevated luteal phase progesterone down-regulating levels of its own receptor. These findings are consistent with other publications
      • Lessey BA
      • Killam AP
      • Metzger DA
      • Haney AF
      • Greene GL
      • McCarty KS
      Immunohistochemical analysis of human uterine estrogen and progesterone receptors throughout the menstrual cycle.
      and serve as a positive procedural control.
      Table ISteroid hormone receptor immunohistochemical scores of premenopausal proliferative versus secretory endometria procedural controls
      Immunohistochemical examinationProliferative endometria*Luteal phase endometria*Significance†
      PR glands366.7 ± 33.333.4 ± 22.2p = 0.001 (VS)
      PR stroma323.3 ± 39.3142.0 ± 34.7p = 0.0158 (S)
      ER glands236.7 ± 37.645.0 ± 22.7p = 0.0034 (VS)
      ER stroma180.0 ± 45.856.0 ± 25p = 0.0392 (S)
      *Immunohistochemical scoring: Percent positively stained cells × Intensity of staining. †Unpaired two-tailed Student t test.
      PR, Progesterone receptor;VS, very significant; S, significant;ER, estrogen receptor.
      There was a significant increase in glandular cell progesterone receptors (p = 0.0046) and a nonsignificant increase in stromal cell progesterone receptor immunohistochemical score in tamoxifen-treated versus atrophic non–hormonally treated endometria (Fig. 1, Table II).
      Figure thumbnail gr1a
      Fig. 1Progesterone receptor staining in control atrophic endometria (A) and in endometrial polyp from tamoxifen-treated patient (B). Note increased expression of progesterone receptor in glands in tamoxifen-treated patient.
      Figure thumbnail gr1b
      Fig. 1Progesterone receptor staining in control atrophic endometria (A) and in endometrial polyp from tamoxifen-treated patient (B). Note increased expression of progesterone receptor in glands in tamoxifen-treated patient.
      Stromal cell estrogen receptor was significantly reduced (49.8 ± 11.0 vs 156.0 ± 43.9, respectively, p = 0.0019) and glandular cell estrogen receptor was nonsignificantly reduced in the tamoxifen-treated versus atrophic group (Table II).
      Table IIEstrogen and progesterone receptor immunohistochemical scores in control group of atrophic endometria compared with endometria from all tamoxifen-treated patients
      Immunohistochemical examinationEndometria from all tamoxifen-treated patientsAtrophic endometriaSignificance†
      PR glands285.1 ± 23.5114.8 ± 52.9p = 0.0046 (VS)
      PR stroma143.7 ± 23.498.0 ± 32p = 0.3721 (NS)
      ER glands83.3 ± 19.2132.0 ± 59.9p = 0.3252 (NS)
      ER stroma49.8 ± 11.0156.0 ± 43.9p = 0.019 (VS)
      †Unpaired two-tailed Student t test.
      Values are mean ± SEM. PR, Progesterone receptor; VS, very significant; NS, not significant; ER, estrogen receptor.
      *Immunohistochemical scoring: Percent positively stained cells × Intensity of staining.
      There were no significant differences between tamoxifen-treated patients with benign versus malignant or premalignant endometrial disorders in either the mean number of years of tamoxifen use (4.3 ± 0.8 vs 3.8 ± 1.4 years, respectively, p = 0.71) or endometrial steroid receptor status. There was no significant difference in the mean number of years of tamoxifen use in women with postmenopausal bleeding (3.5 ± 1.1 years) versus those without bleeding (4.6 ± 0.9 years) (p = 0.42). There were significantly increased levels of glandular cell progesterone receptor staining in tamoxifen-treated patients without abnormal bleeding (334.0 ± 16.5) compared with those with postmenopausal bleeding (205.6 ± 44.0) (p = 0.0047). A similar finding was observed in the stromal cells, but it was not significant (179.6 ± 30.8 vs 98.8 ± 30.7, respectively, p = 0.097). There were no differences in glandular or stromal cell estrogen receptor immunohistochemical scores in tamoxifen-treated patients with postmenopausal bleeding versus those without bleeding (not significant). Those without bleeding in the control polyp group had nonsignificant increases in stromal cell progesterone receptor immunohistochemical scores compared with those with bleeding (207.0 ± 49.3 vs 51.7 ± 44.2, respectively, p = 0.078), and there were no significant differences in glandular cell progesterone receptor or glandular and stromal cell estrogen receptor staining between these two subgroups.
      Postmenopausal bleeding occurred in 8 of 19 (42.1%) tamoxifen-treated patients, 3 of 8 (37.5%) women with nontreated polyps, and none of the patients in the atrophic group. Of the patients with tamoxifen-associated postmenopausal bleeding, the histologic diagnoses included proliferative endometrium (1 patient), polyp (4 patients), and polyp with carcinoma in situ, hyperplasia, increased mitoses, or atypia (3 patients). The diagnoses in the women without bleeding treated with tamoxifen included atrophic endometrium (1 patient), proliferative endometrium (1 patient), polyp (7 patients), polyp with associated premalignant changes (1 patient), and adenocarcinoma (1 patient). The tamoxifen-treated patient with adenocarcinoma without postmenopausal bleeding had transvaginal ultrasonography showing an endometrial fluid collection and a 1 cm mass at the inferior endometrial wall. The remainder of the endometrial echo was <2.3 mm. It is likely that this patient had cervical stenosis that prevented outflow of the endometrial fluid. In the control polyp group, 2 women with postmenopausal bleeding had polyps (1 contained focal glandular crowding).
      All control polyps were histologically classified as nonfunctional; one was also focally proliferative, corresponding to the control polyp with focal glandular crowding. The polyps were also nonfunctional in 11 of the tamoxifen-treated patients. Three polyps were focally proliferative; these included the tamoxifen-treated polyps containing either increased mitoses, atypia, hyperplasia, or carcinoma in situ. One nonfunctional polyp contained focal proliferation and cancer, corresponding with the tamoxifen-treated polyp with carcinoma in situ and adenocarcinoma. There were no significant differences in the histologic features of polyps from tamoxifen-treated versus non–hormonally treated patients, including the mean number (p = 0.87) and thickness (p = 0.87) of blood vessels and the mean stromal cellularity (p = 0.39)(Table III). Every polyp in both the tamoxifen-treated and untreated groups contained dilated, cystic glands, and secretions within the glands. There were similar distributions of metaplasias in the untreated versus tamoxifen-treated polyps (Table IV). A combination of metaplasias was present in one untreated and three tamoxifen-treated polyps. The polyps in each group exhibited other similar typical histologic features, including variations of glands and spindle-shaped stroma. The tamoxifen-associated polyps did not display any unusual histologic features, except for one polyp that contained adenocarcinoma in which there were focal adipose cells within the stroma.
      Table IIIHistologic features of polyps in tamoxifen-treated versus untreated patients
      Histologic featuresControl untreated polypsTamoxifen-treated polypsSignificance
      Mean No. of blood vessels1.50 ± 0.191.60 ± 0.16p = 0.87 (NS)
      Mean blood vessel thickness1.50 ± 0.191.56 ± 0.16p = 0.87 (NS)
      Mean stromal cellularity2.25 ± 0.252.00 ± 0.16p = 0.39 (NS)
      Values are mean ± SEM. NS, Not significant.
      Table IVTypes of metaplasia found in polyps from tamoxifen-treated versus untreated patients
      Type of metaplasiaControl untreated polypsTamoxifentreated polyps
      Tubal613
      Mucinous14
      Squamous00
      Eosinophilic01
      None21
      There were no significant differences in glandular or stromal cell progesterone receptor staining in tamoxifen-treated (269.8 ± 29.0 and 132.5 ± 27.5, respectively) versus control polyps (300.6 ± 34.6 and 148.8 ± 43.4, respectively), although expression was high in both groups (not significant). Stromal cell estrogen receptor staining was significantly reduced in tamoxifen-treated versus non–hormonally treated polyps (48.4 ± 13.5 vs 133.8 ± 40.3, respectively, p = 0.0195) (Fig. 2).
      Figure thumbnail gr2a
      Fig. 2Estrogen receptor staining in endometrial polyp from control patient (A) and in endometrial polyp from tamoxifen-treated patient (B). Higher estrogen receptor staining is present in control versus tamoxifen-treated polyp.
      Figure thumbnail gr2b
      Fig. 2Estrogen receptor staining in endometrial polyp from control patient (A) and in endometrial polyp from tamoxifen-treated patient (B). Higher estrogen receptor staining is present in control versus tamoxifen-treated polyp.
      Estrogen receptor glandular cell staining was nonsignificantly reduced in tamoxifen-treated versus control polyps (90 ± 24.7 vs 199.4 ± 60.8, respectively, p = 0.059) (Table V). There was a significant increase in the glandular cell progesterone receptor immunohistochemical score in the control polyp versus atrophic endometria groups (295.0 ± 33.7 vs 122.0 ± 49.5, respectively, p = 0.012), but no significant differences were found in glandular cell estrogen receptor or stromal cell progesterone and estrogen receptor immunohistochemical scores.
      Table VEstrogen and progesterone receptor immunohistochemical scores in control group of untreated endometrial polyps compared with tamoxifen-associated endometrial polyps
      Immunohistochemical examination*Tamoxifen polypsControl polypsSignificance†
      PR glands269.8 ± 29.0300.6 ± 34.6p = 0.53 (NS)
      PR stroma132.5 ± 27.5148.8 ± 43.4p = 0.78 (NS)
      ER glands90.0 ± 24.7199.4 ± 60.8p = 0.059 (MS)
      ER stroma48.4 ± 13.5133.8 ± 40.3p = 0.0195 (S)
      *Immunohistochemical scoring: Percent positively stained cells × Intensity of staining. †Unpaired two-tailed Student t test.
      Values are mean ± SEM.PR, Progesterone receptor;NS, not significant;ER, estrogen receptor;MS, marginally significant;S, significant.
      The two adenocarcinomas in tamoxifen-treated patients were high for progesterone receptors and low for estrogen receptors in glands (Fig. 3).
      Figure thumbnail gr3a
      Fig. 3Progesterone (A) and estrogen (B) receptor staining in endometrial adenocarcinoma in tamoxifen-treated patient.
      Figure thumbnail gr3b
      Fig. 3Progesterone (A) and estrogen (B) receptor staining in endometrial adenocarcinoma in tamoxifen-treated patient.
      The pattern of reduced stromal cell estrogen receptor immunohistochemical scores and increased glandular cell progesterone receptor immunohistochemical scores was consistently found in all tamoxifen-treated patients regardless of the endometrial diagnosis.

      Comment

      Estradiol up-regulates endometrial progesterone and estrogen receptors, whereas progesterone down-regulates both receptors.
      • Lessey BA
      • Killam AP
      • Metzger DA
      • Haney AF
      • Greene GL
      • McCarty KS
      Immunohistochemical analysis of human uterine estrogen and progesterone receptors throughout the menstrual cycle.
      Estrogen receptor reaches a maximum in the late proliferative phase in all uterine cell types, and levels decline during the luteal phase.
      • Snijders MPML
      • de Goeij AFPM
      • Debets-Te Baerts MJC
      • Rousch MJM
      • Koudstaal J
      • Bosman FT
      Immunocytochemical analysis of oestrogen receptors and progesterone receptors in the human uterus throughout the menstrual cycle and after the menopause.
      Glandular cell progesterone receptor expression is strong during the proliferative phase, reaching a maximum in the late proliferative and early secretory phases with declining levels thereafter.
      • Snijders MPML
      • de Goeij AFPM
      • Debets-Te Baerts MJC
      • Rousch MJM
      • Koudstaal J
      • Bosman FT
      Immunocytochemical analysis of oestrogen receptors and progesterone receptors in the human uterus throughout the menstrual cycle and after the menopause.
      Stromal cell progesterone receptor levels have shown only minor fluctuations during the menstrual cycle.
      • Snijders MPML
      • de Goeij AFPM
      • Debets-Te Baerts MJC
      • Rousch MJM
      • Koudstaal J
      • Bosman FT
      Immunocytochemical analysis of oestrogen receptors and progesterone receptors in the human uterus throughout the menstrual cycle and after the menopause.
      The results of our immunohistochemical experiments on cycling endometria reflect this. Endometrial estrogen and progesterone receptors were down-regulated during the luteal phase, when progesterone levels are high, and up-regulated during the proliferative phase, when estradiol levels are the highest and progesterone levels are low. Our finding that endometrial vascular tissues do not bind antibodies to estrogen or progesterone receptors has been previously reported.
      • Lessey BA
      • Killam AP
      • Metzger DA
      • Haney AF
      • Greene GL
      • McCarty KS
      Immunohistochemical analysis of human uterine estrogen and progesterone receptors throughout the menstrual cycle.
      The distribution of estrogen and progesterone receptors in glandular and stromal cells of postmenopausal atrophic endometria has been somewhat understudied. Estrogen receptor expression is pronounced in glandular and stromal cells of the untreated postmenopausal atrophic endometrium compared with premenopausal cycling endometria.
      • Snijders MPML
      • de Goeij AFPM
      • Debets-Te Baerts MJC
      • Rousch MJM
      • Koudstaal J
      • Bosman FT
      Immunocytochemical analysis of oestrogen receptors and progesterone receptors in the human uterus throughout the menstrual cycle and after the menopause.
      Progesterone receptor expression in the postmenopausal untreated endometrium is characterized by moderate staining of glandular cells but only weak staining of stromal cells.
      • Snijders MPML
      • de Goeij AFPM
      • Debets-Te Baerts MJC
      • Rousch MJM
      • Koudstaal J
      • Bosman FT
      Immunocytochemical analysis of oestrogen receptors and progesterone receptors in the human uterus throughout the menstrual cycle and after the menopause.
      The atrophic endometria of postmenopausal women treated with exogenous estrogen and progesterone is negative for estrogen receptor and progesterone receptor immunohistochemical staining compared with proliferative and hyperplastic endometria.
      • De Cecco L
      • Leone M
      • Gerbaldo D
      • Venturini PL
      • Rissone R
      • Messeni
      • et al.
      Steroid therapy and the endometrium: biological and clinical implications.
      Our finding of significantly increased glandular cell progesterone receptors and decreased stromal cell estrogen receptors in tamoxifen-treated versus atrophic endometria has not been reported previously.
      The high levels of endometrial progesterone receptor are consistent with an estrogenic tamoxifen effect. Two responses of the endometrium to estradiol are increased progesterone receptor levels and tissue growth.
      • Satyaswaroop PG
      • Zaino RYJ
      • Mortel R
      Estrogen-like effects of tamoxifen in human endometrial carcinoma transplanted into nude mice.
      Also consistent with an estrogenic effect is the histologic finding of metaplasia in most of the tamoxifen-treated endometria. The down-regulation of stromal cell estrogen receptor and, to a lesser extent, glandular cell estrogen receptor in tamoxifen-treated versus untreated polyps may be a unique effect of tamoxifen, distinct from that of estradiol. This tamoxifen effect on endometrial stroma may play a role in the development of uterine sarcomas that are reported in some tamoxifen users.
      • Ismail SM
      Pathology of endometrium treated with tamoxifen.
      The inability to demonstrate an increase in progesterone receptors in glandular cells of polyps from tamoxifen-treated versus untreated patients may be a consequence of the high progesterone receptor levels already present in control polyps, so no further increases are seen in the tamoxifen group.
      Although literature on the effects of tamoxifen on endometrial steroid receptors is scarce, there are a few case reports and experimental models that show similar tamoxifen-associated alterations in steroid receptors. 4-Hydroxy-tamoxifen significantly increases progesterone receptors in Ishikawa cells.
      • Jamil A
      • Croxtall JD
      • White JO
      The effect of anti-oestrogens on cell growth and progesterone receptor concentration in human endometrial cancer cells (Ishikawa).
      Tamoxifen-treated endometrial tumor–xenotransplanted nude mice express low estrogen receptors.
      • Vering A
      • Vockel A
      • Stegmuller M
      • Bender HG
      Immuno-biochemical assay for determination of nuclear steroid receptors during tamoxifen therapy.
      A case report
      • Schwartz PE
      • MacLusky N
      • Naftolin F
      • Eisenfeld A
      Tamoxifen-induced increase in cytosol progesterone receptor levels in a case of metastatic endometrial cancer.
      of a postmenopausal woman with well-differentiated endometrial adenocarcinoma showed increased progesterone receptor levels in groin metastases during tamoxifen therapy. In 11 premenopausal patients treated with tamoxifen (20 mg/day for 3 weeks) for fibrocystic breast disease, there was a significant decrease in endometrial estrogen receptors compared with the control luteal phase, whereas progesterone receptors remained unchanged.
      • Perez-Lopez FR
      • Blasco Comenge C
      Effects of tamoxifen on endometrial estrogen and progesterone receptor concentrations in women with fibrocystic disease of the breast.
      Tamoxifen's effects on target tissues may be expressed by a variety of intracellular pathways in addition to that of the classic estrogen receptor.
      • Ince BA
      • Schodin DJ
      • Shapiro DJ
      • Katzenellenbogen BS
      Repression of endogenous estrogen receptor activity in MCF-7 human breast cancer cells by dominant negative estrogen receptors.
      • Webb P
      • Lopez GN
      • Uht RM
      • Kushner PJ
      Tamoxifen activation of the estrogen receptor/AP-1 pathway: potential origin of the cell-specific estrogen-like effects of antiestrogens.
      Sets of receptor subtypes may be involved
      • Ince BA
      • Schodin DJ
      • Shapiro DJ
      • Katzenellenbogen BS
      Repression of endogenous estrogen receptor activity in MCF-7 human breast cancer cells by dominant negative estrogen receptors.
      as well as cyclic adenosine monophosphate–mediated systems.
      • Webb P
      • Lopez GN
      • Uht RM
      • Kushner PJ
      Tamoxifen activation of the estrogen receptor/AP-1 pathway: potential origin of the cell-specific estrogen-like effects of antiestrogens.
      Each of these systems could be differentially expressed, depending on the end organ. This variety of second-messenger system may explain in large part our observations of agonistic endometrial effects of tamoxifen in spite of decreased glandular and stromal cell estrogen receptors.
      The higher levels of endometrial progesterone receptor observed in tamoxifen-treated women without versus those with bleeding may provide increased receptor availability for binding of low levels of endogenous progesterone, resulting in endometrial stabilization. The reduction in stromal cell estrogen receptor and the increase in glandular cell progesterone receptor immunohistochemical scores are independent of the duration of tamoxifen use and the type of endometrial histologic and pathologic diagnosis. Our finding that endometrial histologic diagnosis, steroid receptor status, and postmenopausal bleeding symptoms are independent of the number of years of tamoxifen use may be explained by the <5-year mean duration of tamoxifen use in our patients. The frequency of endometrial carcinoma increases with the duration of tamoxifen therapy and is highest after 5 years of treatment (6.4%).
      • Forlander T
      • Cedermark B
      • Mattsson A
      • Skoog L
      • Theve T
      • Askergren J
      Adjuvant tamoxifen in early breast cancer: occurrence of new primary cancers.
      There is a dose-dependent effect, with higher cancer rates after a daily dose of 40 mg (0.5%) versus 20 mg (0.1%).
      • DeMuylder X
      • Neven P
      • Sesomer M
      • van Belle Y
      • Vanderick G
      • DeMuylder E
      Endometrial lesions in patients undergoing tamoxifen therapy.
      Women who have received cumulative tamoxifen doses of >35 gm may be at increased risk of endometrial cancer.
      • Ismail SM
      Pathology of endometrium treated with tamoxifen.
      We were not able to confirm previous reports of unusual histologic features distinguishing tamoxifen-treated from nontreated polyps.
      • Ismail SM
      Pathology of endometrium treated with tamoxifen.
      We found increased mitoses, hyperplasia, or carcinoma in situ in 4 of 15 (26.7%) of the tamoxifen-associated polyps, consistent with previous reports.
      • Corley D
      • Rowe J
      • Curtis MT
      • Hogan M
      • Noumoff JS
      • Livolsi VA
      Postmenopausal bleeding from unusual endometrial polyps in women on chronic tamoxifen therapy.
      Progestins have been shown to be effective in the treatment of endometrial carcinoma
      • Kelley RM
      • Baker WH
      Progestational agents in the treatment of carcinoma of the endometrium.
      and also serve as a second-line treatment for recurrent breast cancer.
      • Gill PG
      • Gebski V
      • Snyder R
      • Burns I
      • Levi J
      • Byrne M
      • et al.
      Randomized comparison of the effects of tamoxifen, megestrol acetate, or tamoxifen plus megestrol acetate on treatment responses and survival in patients with metastatic breast cancer.
      Because progestins also lower progesterone receptor levels, essentially reducing their own effectiveness, an agent such as tamoxifen that augments progesterone receptor levels within the tumor may be expected to either potentiate or replace progestin therapy.
      • Satyaswaroop PG
      • Clarke CL
      • Zaino RJ
      • Mortel R
      Apparent resistance in human endometrial carcinoma during combination treatment with tamoxifen and progestin may result from desensitization following downregulation of tumor progesterone receptor.
      The addition of progestins as a form of endometrial protection from the stimulatory side effects of tamoxifen when used as adjuvant postoperative therapy for breast cancer is controversial because of concern over potential progestin-induced proliferative effects on the breasts. More work is needed to clarify these clinical issues.
      The tamoxifen-associated changes in endometrial steroid receptors and their persistent distinct pattern compared with all the other study groups supports an estrogenic uterine effect. This effect is independent of the type of endometrial pathologic diagnosis and the duration of tamoxifen use. This estrogen-like action of tamoxifen at the endometrial steroid receptor level may contribute to the pathogenesis or growth of endometrial polyps and carcinomas in these patients.

      References

        • Early Breast Cancer Trials Collaborative Group
        Effects of tamoxifen and of cytotoxic therapy on mortality in early breast cancer: an overview of 61 randomized trials among 28,896 women.
        N Engl J Med. 1988; 319: 1681-1692
        • Daniel Y
        • Inbar M
        • Bar-Am A
        • Peyser MR
        • Lessing JB
        The effects of tamoxifen treatment on the endometrium.
        Fertil Steril. 1996; 65: 1083-1089
        • Forlander T
        • Cedermark B
        • Mattsson A
        • Skoog L
        • Theve T
        • Askergren J
        Adjuvant tamoxifen in early breast cancer: occurrence of new primary cancers.
        Lancet. 1989; 1: 117-120
        • Rutqvist LE
        • Cedermark B
        • Glas U
        The Stockholm trial on adjuvant tamoxifen in early breast cancer.
        Breast Cancer Res Treat. 1987; 10: 255-266
        • Anzai Y
        • Holinka CF
        • Kuramoto H
        • Gurpide E
        Stimulatory effects of 4-hydroxytamoxifen on proliferation of human endometrial adenocarcinoma cells (Ishikawa line).
        Cancer Res. 1989; 49: 2362-2365
        • Gottardis MM
        • Robinson SP
        • Satyaswaroop PG
        • Jordan VC
        Contrasting actions of tamoxifen on endometrial and breast tumor growth in the athymic mouse.
        Cancer Res. 1988; 48: 812-815
        • Mittal KR
        • Demopoulos RI
        • Goswami S
        Proliferating clee nuclear antigen (cyclin) expression in normal and abnormal cervical squamous epithelia.
        Am J Surg Pathol. 1993; 17: 117-122
        • Gold LI
        • Saxena B
        • Mittal KR
        • Goswami S
        • Nachtigall L
        • Kore M
        • et al.
        Increased expression of transforming growth factor B isoforms and basic fibroblast growth factor in complex hyperplasia and adenocarcinoma of the endometrium: evidence for paracrine and autocrine action.
        Cancer Res. 1994; 54: 2347-2358
        • Noyes RW
        • Hertig DT
        • Rock J
        Dating the endometrial biopsy.
        Fertil Steril. 1950; 1: 3-25
        • Lessey BA
        • Killam AP
        • Metzger DA
        • Haney AF
        • Greene GL
        • McCarty KS
        Immunohistochemical analysis of human uterine estrogen and progesterone receptors throughout the menstrual cycle.
        J Clin Endocrinol Metab. 1988; 67: 334-340
        • Snijders MPML
        • de Goeij AFPM
        • Debets-Te Baerts MJC
        • Rousch MJM
        • Koudstaal J
        • Bosman FT
        Immunocytochemical analysis of oestrogen receptors and progesterone receptors in the human uterus throughout the menstrual cycle and after the menopause.
        J Reprod Fertil. 1992; 94: 363-371
        • De Cecco L
        • Leone M
        • Gerbaldo D
        • Venturini PL
        • Rissone R
        • Messeni
        • et al.
        Steroid therapy and the endometrium: biological and clinical implications.
        Ann N Y Acad Sci. 1991; 622: 296-301
        • Satyaswaroop PG
        • Zaino RYJ
        • Mortel R
        Estrogen-like effects of tamoxifen in human endometrial carcinoma transplanted into nude mice.
        Cancer Res. 1984; 44: 4006-4010
        • Ismail SM
        Pathology of endometrium treated with tamoxifen.
        J Clin Pathol. 1994; 47: 827-833
        • Jamil A
        • Croxtall JD
        • White JO
        The effect of anti-oestrogens on cell growth and progesterone receptor concentration in human endometrial cancer cells (Ishikawa).
        J Mol Endocrinol. 1991; 6: 215-221
        • Vering A
        • Vockel A
        • Stegmuller M
        • Bender HG
        Immuno-biochemical assay for determination of nuclear steroid receptors during tamoxifen therapy.
        J Cancer Res Clin Oncol. 1993; 119: 415-420
        • Schwartz PE
        • MacLusky N
        • Naftolin F
        • Eisenfeld A
        Tamoxifen-induced increase in cytosol progesterone receptor levels in a case of metastatic endometrial cancer.
        Gynecol Oncol. 1983; 16: 41-48
        • Perez-Lopez FR
        • Blasco Comenge C
        Effects of tamoxifen on endometrial estrogen and progesterone receptor concentrations in women with fibrocystic disease of the breast.
        Gynecol Endocrinol. 1993; 7: 185-189
        • Ince BA
        • Schodin DJ
        • Shapiro DJ
        • Katzenellenbogen BS
        Repression of endogenous estrogen receptor activity in MCF-7 human breast cancer cells by dominant negative estrogen receptors.
        Endocrinology. 1995; 136: 3194-3199
        • Webb P
        • Lopez GN
        • Uht RM
        • Kushner PJ
        Tamoxifen activation of the estrogen receptor/AP-1 pathway: potential origin of the cell-specific estrogen-like effects of antiestrogens.
        Mol Endocrinol. 1995; 9: 443-456
        • DeMuylder X
        • Neven P
        • Sesomer M
        • van Belle Y
        • Vanderick G
        • DeMuylder E
        Endometrial lesions in patients undergoing tamoxifen therapy.
        Int J Gynecol Obstet. 1991; 36: 127-130
        • Corley D
        • Rowe J
        • Curtis MT
        • Hogan M
        • Noumoff JS
        • Livolsi VA
        Postmenopausal bleeding from unusual endometrial polyps in women on chronic tamoxifen therapy.
        Obstet Gynecol. 1992; 79: 111-116
        • Kelley RM
        • Baker WH
        Progestational agents in the treatment of carcinoma of the endometrium.
        N Engl J Med. 1961; 264: 216-222
        • Gill PG
        • Gebski V
        • Snyder R
        • Burns I
        • Levi J
        • Byrne M
        • et al.
        Randomized comparison of the effects of tamoxifen, megestrol acetate, or tamoxifen plus megestrol acetate on treatment responses and survival in patients with metastatic breast cancer.
        Ann Oncol. 1993; 4: 741-744
        • Satyaswaroop PG
        • Clarke CL
        • Zaino RJ
        • Mortel R
        Apparent resistance in human endometrial carcinoma during combination treatment with tamoxifen and progestin may result from desensitization following downregulation of tumor progesterone receptor.
        Cancer Lett. 1992; 62: 107-114