Complete sequencing of TP53 predicts poor response to systemic therapy of advanced breast cancer

TP53 has been implicated in regulation of the cell cycle, DNA repair, and apoptosis. We studied, in primary breast tumors through direct cDNA sequencing of exons 2-11, whether TP53 gene mutations can predict response in patients with advanced disease to either first-line tamoxifen therapy (202 patients, of whom 55% responded) or up-front (poly)chemotherapy (41 patients, of whom 46% responded). TP53 mutations were detected in 90 of 243 (37%) tumors, and one-fourth of these mutations resulted in a premature termination of the protein. The mutations were observed in 32% (65 of 202) of the primary tumors of tamoxifen-treated patients and in 61% (25 of 41) of the primary tumors of the chemotherapy patients. TP53 mutation was significantly associated with a poor response to tamoxifen [31% versus 66%; odds ratio (OR), 0.22; 95% confidence interval (CI), 0.12-0.42; P < 0.0001]. Patients with TP53 gene mutations in codons that directly contact DNA or with mutations in the zinc-binding domain loop L3 showed the lowest response to tamoxifen (18% and 15% response rates, respectively). TP53 mutations were related, although not significantly, to a poor response to up-front chemotherapy (36% versus 63%; OR, 0.34; 95% CI, 0.09-1.24). In multivariate analysis for response including the classical parameters age and menopausal status, disease-free interval, dominant site of relapse, and levels of estrogen receptor and progesterone receptor, TP53 mutation was a significant predictor of poor response in the tamoxifen-treated group (OR, 0.29; 95% CI, 0.13-0.63; P = 0.0014). TP53-mutated and estrogen receptor-negative (<10 fmol/mg protein) tumors appeared to be the most resistant phenotype. Interestingly, the response of patients with TP53 mutations to chemotherapy after tamoxifen was not worse than that of patients without these mutations (50% versus 42%; OR, 1.35, nonsignificant). The median progression-free survival after systemic treatment was shorter for patients with a TP53 mutation than for patients with wild-type TP53 (6.6 and 0.6 months less for tamoxifen and up-front chemotherapy, respectively). In conclusion, TP53 gene mutation of the primary tumor is helpful in predicting the response of patients with metastatic breast disease to tamoxifen therapy. The type of mutation and its biological function should be considered in the analyses of the predictive value of TP53.     

Raptor localization predicts prognosis and tamoxifen response in estrogen receptor-positive breast cancer

Purpose

Deregulated PI3K/mTOR signals can promote the growth of breast cancer and contribute to endocrine treatment resistance. This report aims to investigate raptor and its intracellular localization to further understand its role in ER-positive breast cancer.

Methods

Raptor protein expression was evaluated by immunohistochemistry in 756 primary breast tumors from postmenopausal patients randomized to tamoxifen or no tamoxifen. In vitro, the MCF7 breast cancer cell line and tamoxifen-resistant MCF7 cells were studied to track the raptor signaling changes upon resistance, and raptor localization in ERα-positive cell lines was compared with that in ERα-negative cell lines.

Results

Raptor protein expression in the nucleus was high in ER/PgR-positive and HER2-negative tumors with low grade, features associated with the luminal A subtype. Presence of raptor in the nucleus was connected with ERα signaling, here shown by a coupled increase of ERα phosphorylation at S167 and S305 with accumulation of nuclear raptor. In addition, the expression of ERα-activated gene products correlated with nuclear raptor. Similarly, in vitro we observed raptor in the nucleus of ERα-positive, but not of ER-negative cells. Interestingly, raptor localized to the nucleus could still be seen in tamoxifen-resistant MCF7 cells. The clinical benefit from tamoxifen was inversely associated with an increase of nuclear raptor. High cytoplasmic raptor expression indicated worse prognosis on long-term follow-up.

Conclusion

We present a connection between raptor localization to the nucleus and ERα-positive breast cancer, suggesting raptor as a player in stimulating the growth of the luminal A subtype and a possible target along with endocrine treatment.

     

High tumor levels of vascular endothelial growth factor predict poor response to systemic therapy in advanced breast cancer.

Vascular endothelial growth factor (VEGF), a potent angiogenic factor, has been reported to be associated with a poor prognosis in primary breast cancer and in several other cancer types. In the present study, we have measured with ELISA the levels of VEGF in cytosolic extracts of 845 primary breast tumors of patients who developed a recurrence during follow-up. All of the patients received tamoxifen (n = 618) or cyclophosphamide, methotrexate, 5-fluorouracil (CMF) or 5-fluorouracil, Adriamycin, cyclophosphamide (FAC) chemotherapy (n = 227) as first-line systemic therapy after diagnosis of advanced disease. VEGF levels were not related to age or menopausal status but were negatively related to the cytosolic levels of estrogen receptor and progesterone receptor (P < 0.0001). In patients who relapsed within 1 year after primary surgery, tumor VEGF levels were higher than in patients who showed a longer disease-free interval (P = 0.0005). In patients with a first relapse in the viscera, VEGF levels were higher compared with those that relapsed to the bone or soft tissue (P = 0.0004). In univariate analysis for response to first-line tamoxifen therapy, patients with high or intermediate levels showed a poor rate of response, compared with patients with low tumor-VEGF levels (P = 0.0001). Similarly, in multivariate analysis for response to tamoxifen treatment, corrected for age, site of relapse, disease-free interval, and estrogen receptor and progesterone receptor status, VEGF status was an independent predictive factor (P = 0.009). In concordance, higher levels of VEGF were associated with a short progression-free survival and postrelapse overall survival (both, P < 0.0001). On first-line chemotherapy, the rate of response decreased with higher tumor levels of VEGF, both in univariate (P = 0.003) and in multivariate analysis (P = 0.004). Furthermore, higher VEGF levels were associated with a short progression-free survival (P = 0.003) and postrelapse overall survival (P = 0.001). In conclusion, the tumor VEGF level is an important independent marker that predicts a poor efficacy of both tamoxifen and chemotherapy in advanced breast cancer. Knowledge of the tumor level of VEGF might be helpful in selecting individual patients who may benefit from treatments with antiangiogenic agents combined with conventionally used drugs.     

Serum vascular endothelial growth factor in breast cancer: its relation with cancer type and estrogen receptor status.

PURPOSE: Angiogenesis is essential for tumor growth. Vascular endothelial growth factor (VEGF) is one of the most potent angiogenic cytokines. In breast cancer, tumor VEGF has been shown to have a good correlation with relapse-free survival. The aim of this study was to determine the relation of serum VEGF levels to the various indices of breast cancer and known tumor markers carcinoembryonic antigen and CA15.3. EXPERIMENTAL DESIGN: Preoperative serum VEGF levels were determined in 200 women with breast cancer and compared with serum VEGF levels in 88 healthy female controls. RESULTS: The serum VEGF levels of the cancer patients as a group were significantly elevated compared with those of the controls (P < 0.0005). VEGF levels were elevated in patients with invasive cancer of ductal/no specific type, ductal carcinoma in situ, and estrogen receptor (ER)-positive tumors. Patients with lobular carcinoma and ER-negative tumors had serum VEGF levels comparable with those in the controls. VEGF was more sensitive than CA15.3 and carcinoembryonic antigen in detecting breast cancer. CONCLUSIONS: Preoperative serum VEGF detects breast cancer with a sensitivity of 62.1%. The relationship to cancer type and ER status may have future therapeutic implications. Additional long-term studies are required to determine the prognostic significance of serum VEGF.     

Effect of estrogen, tamoxifen and epidermal growth factor on the transcriptional regulation of vascular endothelial growth factor in breast cancer cells

BACKGROUND: VEGF (Vascular Endothelial Growth Factor) is a key factor of angiogenesis and high tissue VEGF levels are related to a poor prognosis in breast cancer. MATERIALS AND METHODS: By semi-quantitative RT-PCR, we determined the relative expressions of VEGF mRNA in MCF-7 (both ER-alpha+ and ER-beta+ (mainly ER-alpha+), PR+, bcl-2+, EGFR-) and MB-MDA-231 (only ER-beta+, PR-, EGFR-) breast cancer cells which were treated with estrogen, tamoxifen and EGF (Epidermal Growth Factor). RESULTS: In MCF-7 cell lines, estrogen induced the expression of VEGF mRNA while tamoxifen reduced its expression. Estrogen and tamoxifen did not confer any significant effect on MB-MDA-231 cells and EGF showed no significant effect on MCF-7 or MB-MDA-231. CONCLUSION: Reduced VEGF mRNA expression of MCF-7 cells treated with tamoxifen may be related to the antagonistic effect of tamoxifen on ER-positive breast cancer, and this antagonistic effect may be related to ER-alpha.     

雌激素及其拮抗剂对乳腺癌血管内皮生长因子的转录调节

背景与目的：肿瘤血管生成在乳腺癌的生长和转移中占有重要地位，内分泌治疗是否影响乳腺癌的肿瘤血管生成是临床关注的重要课题。本研究探讨雌激素及其拈抗剂对人乳腺癌细胞中血管内皮生长因子（VEGF）的转录调节作用及其机制。方法：应用半定量RT—PCR法检测不同浓度和作用时间下雌二醇（E2）对MCF-7乳腺癌细胞VEGF mRNA表达影响，并检测他莫昔芬（三苯氧胺，TAM）和ICI182780是否可抑制雌激素对VEGF转录的影响。结果：剂量依赖性实验显示E2浓度为1～10nmol／L时，VEGFmRNA表达水平最高，为0．125&#177;0．006-0．112&#177;0．014；时间依赖性实验中E2培养2h内VEGF转录水平明显升高（0．105&#177;0．009），6h达到最大值（0．140&#177;0．024），较未治疗组高1．5倍（P〈0．05）。TAM在浓度为1nmol／L时可轻微促进VEGFmRNA表达（0．061&#177;0．010），但该浓度下与E2共同培养时可抑制E2诱导VEGF产生（0．070&#177;0．001）；ICI182780同样可抑制E2诱导VEGF产生（0．068&#177;0．001）。结论：雌激素可促进VEGFmRNA生成，其生成量依赖于雌激素的浓度和作用时间；TAM和ICI182780对雌激素诱导VEGFmRNA生成具有抑制作用，提示雌激素及其拮抗剂在转录水平调节VEOF表达，TAM通过阻遏雌激素诱导VEGF表达抑制乳腺癌肿瘤血管生成。     

High expression of steroid sulfatase mRNA predicts poor prognosis in patients with estrogen receptor-positive breast cancer.

PURPOSE: Prognostic significance of the intratumoral mRNA expression of three enzymes related to in situ estrogen biosynthesis, i.e., aromatase, sulfatase, and 17beta-hydroxysteroid dehydrogenase type 1 (17beta-HSD1), was evaluated in patients with invasive breast cancer. EXPERIMENTAL DESIGN: Aromatase, sulfatase, and 17beta-HSD1 mRNA levels in tumor tissues (n = 181) and normal breast tissues (n = 34) were examined by a quantitative, real-time PCR assay and compared with various clinicopathological factors as well as prognosis. RESULTS: The sulfatase mRNA levels, but not the aromataseor 17beta-HSD1 mRNA levels, were significantly associated with lymph node metastases (P < 0.005), histological grade III (P < 0.001), and poor prognosis (P < 0.005). The association between the sulfatase mRNA and poor prognosis was found to be significant (P < 0.001) only in patients with estrogen receptor (ER)-positive tumors but not in ER negative tumors. In ER-positive tumors, the sulfatase mRNA levels was a significant prognostic factor independent of the lymph node status and histological grade by multivariate analysis. CONCLUSIONS: The sulfatase mRNA levels can serve as a significant, independent prognostic factor only in ER-positive tumors. It is speculated that the up-regulation of sulfatase mRNA levels leads to a high intratumoral estrogen concentration and, thus, an enhanced stimulation of tumor growth through ERs.     

The effects of neoadjuvant anastrozole and tamoxifen on circulating vascular endothelial growth factor and soluble vascular endothelial growth factor receptor 1 in breast cancer.

PURPOSE: Vascular endothelial growth factor (VEGF) is a key angiogenic factor mediating neovascularization. Soluble VEGF receptor 1 (sVEGFR-1) is an intrinsic negative counterpart of VEGF signaling and the ratio of sVEGFR-1 to VEGF has been shown to be a prognostic factor. Estrogen-bound estrogen receptor enhances VEGF expression, providing a common link between these signaling pathways that may be targeted by endocrine therapy. We investigated the effects of anastrozole and tamoxifen over time on serum VEGF and sVEGFR-1. EXPERIMENTAL DESIGN: The Immediate Preoperative Anastrozole, Tamoxifen, or Combined with Tamoxifen (IMPACT) trial compared the preoperative use of anastrozole with tamoxifen in postmenopausal women with estrogen receptor-positive primary operable breast cancer over 12 weeks. Circulating VEGF and sVEGFR-1 were measured by ELISA in 106 patients treated with anastrozole or tamoxifen alone at baseline and after 2 and 12 weeks of treatment. RESULTS: The increase in serum VEGF from baseline to 12 weeks was significantly different between anastrozole and tamoxifen (anastrozole versus tamoxifen, 6% versus 38%; P = 0.047). There was a significant increase in sVEGFR-1 levels after 12 weeks of anastrozole (P = 0.037). The sVEGFR-1/VEGF ratio significantly decreased in the tamoxifen arm (P = 0.013) and the change in sVEGFR-1/VEGF ratio from baseline to 12 weeks was significantly different between anastrozole and tamoxifen (anastrozole versus tamoxifen, 24% increase versus 34% decrease; P = 0.013). CONCLUSIONS: Treatment with anastrozole and tamoxifen resulted in differential effects on serum angiogenic markers. This may be related to the relative effectiveness of the treatments. These data provide further support for cross talk between estrogen receptor and VEGF.     

Randomized trial of estrogen vs. tamoxifen therapy for advanced breast cancer

Forty-three postmenopausal females with advanced breast cancer were studied in a prospective comparative trial of estrogen vs. an anti-estrogen (tamoxifen) therapy with a crossover to the alternative hormone with progressive disease. Ten of 19 patients (53%) responded to primary tamoxifen therapy and six of 24 (25%) responded to primary estrogen therapy. Crossover responses were observed in seven of 19 (37%) on the secondary tamoxifen therapy and in two of 10 (20%) on secondary estrogen therapy, and were not related to the response to the primary hormonal maneuver. Responses were related to the presence of estrogen receptor protein (ERP), particularly for tamoxifen therapy, although responses were observed in three of six ERP negative patients receiving estrogen and in seven of 25 (28%) of patients with an unknown ERP status. Complications were observed in 35 instances with estrogen therapy and in only five instances with tamoxifen therapy. Initial hormonal therapy with tamoxifen in postmenopausal patients with advanced breast cancer and ERP status positive or unknown is superior to primary estrogen treatment. Secondary therapy and response to estrogen or tamoxifen is not necessarily predicted by the initial hormone response, and crossover to the alternative therapy is generally indicated.     

Her-2/neu overexpression and response to oophorectomy plus tamoxifen adjuvant therapy in estrogen receptor-positive premenopausal women with operable breast cancer.

PURPOSE: Studies evaluating the relationship of HER-2/neu breast tumor status and response to adjuvant endocrine therapy have reached conflicting conclusions about resistance of HER-2/neu-positive tumors to this treatment. We studied 282 patients participating in a randomized controlled trial of adjuvant oophorectomy and tamoxifen or observation who had estrogen receptor-positive tumors and whose tumors were evaluated for HER-2/neu overexpression by immunohistochemistry. PATIENTS AND METHODS: Univariate and multivariate Cox proportional hazards regression models and Kaplan-Meier disease-free and overall survival estimate methods were used. RESULTS: HER-2/neu overexpression was a negative prognostic factor for overall survival. In univariate analyses, in HER-2/neu-positive patients, the hazard ratio (HR) for disease-free survival (DFS) with adjuvant endocrine therapy was 0.37 (95% confidence interval [CI], 0.26 to 0.89); for HER-2/neu-negative patients, the corresponding HR for DFS was 0.48 (95% CI, 0.31 to 0.71). The overall survival (OS) data were HR=0.26 (95% CI, 0.07 to 0.92) and HR=0.68 (95% CI, 0.32 to 1.42) for HER-2/neu-positive and HER-2/neu-negative patients, respectively. In multivariate models, the P values for tests of interaction of HER-2/neu status and response to adjuvant endocrine therapy were 0.18 and 0.07 for DFS and OS, respectively. Kaplan-Meier DFS and OS curves and 3-year DFS estimates were consistent in showing greater benefit to the HER-2/neu-positive subgroup given adjuvant treatment. CONCLUSION: HER-2/neu overexpression does not adversely and may favorably influence response to adjuvant oophorectomy and tamoxifen treatment in patients with estrogen receptor-positive tumors.     

The expression of vascular endothelial growth factor correlates with mutant p53 and poor prognosis in human breast cancer

Wild-type p53 protein has been shown to inhibit angiogenesis through thrombospondin in the preclinical setting. Here, we determined the associations between the expression of the angiogenic factor vascular endothelial growth factor (VEGF) and the p53 status, including different mutation sites and types, in primary breast cancer. Cytosols from 224 primary breast cancer patients were analyzed with an enzyme immunoassay for determination of human VEGF165 protein content. p53 status was determined by cDNA-based sequencing of the entire coding region, by immunohistochemistry (IHC), and by a p53 luminometric immunoassay (LIA) method. Statistically significant associations was found between higher VEGF content and non-wild-type p53 status for all methods; sequence-based data (P = 0.0019), IHC data (P = 0.0068), and the LIA method (r = 0.427; P > 0.001). Highest VEGF values were detected in tumors with p53 insertions, deletions, and stop codon mutations (P = 0.0043). Combining p53 status and VEGF content resulted in additional prognostic information, relapse-free survival (RFS; P = 0.0377), overall survival (OS; P = 0.0319), and breast cancer corrected survival (BCCS; P = 0.0292). In multivariate analysis, the relative hazard increased when the VEGF data were added to the p53 status, with a relative hazard of 1.7 for RFS and 3.0 for BCCS, compared with 1.1 for RFS and 1.4 for BCCS among the patients with either high VEGF content or p53 mutation. Higher VEGF content was statistically significantly correlated with a worse outcome for patients with estrogen receptor-positive tumors receiving adjuvant tamoxifen: RFS (P = 0.0471), OS (P = 0.0134), BCCS (P = 0.0064), as well as in multivariate analysis with point estimates of 3.4 and 2.1 for BCCS and RFS, respectively. VEGF expression is related to p53 status in human breast cancer patients. Combining VEGF with p53 status resulted in better prognostic prediction.     

HER-2/neu and p53 expression versus tamoxifen resistance in estrogen receptor-positive, node-positive breast cancer.

PURPOSE: An association between the overexpression of proto-oncogene HER-2/neu and resistance to tamoxifen in estrogen receptor (ER)-positive primary and metastatic breast cancer has been suggested. We examine a possible interaction between HER-2/neu or p53 expression and tamoxifen effectiveness in patients with ER-positive, node-positive disease treated with cyclophosphamide, doxorubicin, and fluorouracil in a large adjuvant chemotherapy trial (Cancer and Leukemia Group B [CALGB] 8541). Tamoxifen assignment was not randomized-physician discretion was used for premenopausal and postmenopausal women. Trial protocol then specified assignment to postmenopausal women with ER-positive tumors, although not all took tamoxifen. PATIENTS AND METHODS: CALGB 8541 assessed HER-2/neu expression in patients with ER-positive disease by immunohistochemistry (IHC) and fluorescent in situ hybridization (FISH) and amplification by differential polymerase chain reaction (PCR). IHC assessed expression of p53. Univariate and multivariate proportional hazards models assessed tamoxifen-HER-2/neu status interactions and tamoxifen-p53 status interactions. RESULTS: HER-2/neu status was available for 651 patients with ER-positive disease; 650, 608, and 353 patients were assessed by IHC, PCR, and FISH, respectively. Approximately one half received tamoxifen. Reduction in risk of disease recurrence or death resulting from tamoxifen was approximately 37% (32% with overexpression and 39% with normal expression of HER-2/neu; n = 155 by IHC). The tamoxifen-HER-2/neu status interaction was not significant in multivariate analysis of all three HER-2/neu assessment methods. Tamoxifen-p53 interaction did not significantly predict outcome. CONCLUSION: Disease-free and overall survival benefit of tamoxifen in patients with ER-positive, node-positive breast cancer does not depend on HER-2/neu or p53 status. Our data suggest that neither HER-2/neu nor p53 expression should be used to determine assignment of tamoxifen.     

Tumor-specific expression of vascular endothelial growth factor receptor 2 but not vascular endothelial growth factor or human epidermal growth factor receptor 2 is associated with impaired response to adjuvant tamoxifen in premenopausal breast cancer.

PURPOSE: Vascular endothelial growth factor A (VEGF-A) and vascular endothelial growth factor receptor 2 (VEGFR2) are often coexpressed in breast cancer, and potentially affect cellular pathways and key proteins such as the estrogen receptor (ER) targeted by endocrine treatment. We therefore explored the association between adjuvant tamoxifen treatment in breast cancer and expression of VEGF-A and VEGFR2, as well as human epidermal growth factor receptor 2 (HER2), which represents a candidate gene product involved in tamoxifen resistance. PATIENTS AND METHODS: Immunohistochemical expression of tumor-specific VEGF-A, VEGFR2, and HER2 was evaluated in tumor specimens from premenopausal breast cancer patients randomly assigned to 2 years of tamoxifen or no treatment (n = 564), with 14 years of follow-up. Hormone receptor status was determined in 96% of the tumors. RESULTS: VEGF-A, VEGFR2, and HER2 were assessable in 460, 472, and 428 of the tumors, respectively. In patients with ER-positive and VEGFR2-low tumors, adjuvant tamoxifen significantly increased recurrence-free survival (RFS; [HR] hazard ratio for RFS, 0.53; P = .001). In contrast, tamoxifen treatment had no effect in patients with VEGFR2-high tumors (HR for RFS, 2.44; P = .2). When multivariate interaction analyses were used, this difference in treatment efficacy relative to VEGFR2 expression status was statistically significant for both ER-positive (P = .04) plus ER-positive and progesterone receptor-positive tumors. We found no significant difference in tamoxifen treatment effects in relation to VEGF-A or HER2 status. CONCLUSION: Tumor-specific expression of VEGFR2 was associated with an impaired tamoxifen effect in hormone receptor-positive premenopausal breast cancer. Tamoxifen in combination with VEGFR2 inhibitors might be a novel treatment approach for VEGFR2-expressing breast cancer, and such a treatment might restore the tamoxifen response.     

High survivin predicts a poor response to endocrine therapy, but a good response to chemotherapy in advanced breast cancer

Summary Variants of survivin with differing subcellular localizations might mediate the different functions of survivin, i.e. cell-cycle regulation and apoptosis inhibition. Highly proliferative tumors are more sensitive to chemotherapy, whereas apoptosis resistant cells would be refractory to endocrine therapy. Possibly, this explains incongruent data on the association of survivin with prognosis in breast cancer. Survivin levels were measured using ELISA in 800 × g pellets and 100,000 × g supernatants of breast cancer tissues from patients that were treated with either chemotherapy or endocrine therapy for advanced disease. These fractions might be enriched with nuclear or cytoplasmatic located survivin variants. Survivin levels were associated with tumors with poor prognostic clinical characteristics. For the patients treated with endocrine therapy, the patients with high survivin levels exhibited a significantly shorter progression free survival (PFS) than those who had low levels (pellet survivin Hazard Ratio (HR)=2.74, 95% Confidence Interval (CI)=1.31–5.72, p=0.008 and median PFS 5.8 versus 8.6 months, p=0.006, log-rank; cytosolic survivin HR=3.03, 95% CI=1.45–6.35, p=0.003). In contrast, for patients treated with chemotherapy, those with high cytosolic survivin had a significantly longer PFS than those with low levels (median PFS of 6.2 months, versus 4.7 months for patients with low cytosolic concentrations, p=0.024, log-rank). Thus, high levels of survivin are mainly related with a poor response to endocrine therapy, but a good response to chemotherapy. This phenomenon might be related to the different functions of survivin.     

晚期雌激素受体阳性乳腺癌的治疗进展

针对晚期雌激素受体阳性乳腺癌虽然主要使用内分泌、靶向等治疗方法,但内分泌治疗的耐药问题在临床上较常见。随着对CDK4/6、PI3K-Akt1-mTOR通路等治疗靶点和耐药机制的研究,晚期雌激素受体阳性乳腺癌的靶向治疗已成为研究热点,利用基因靶向治疗等也可能成为新的突破点,同时在如何针对不同患者选择最佳治疗方案、最佳治疗时间等问题上仍存在挑战。本文将就晚期雌激素受体阳性乳腺癌的治疗进展进行综述。      

Variation of estrogen and progesterone receptor status in breast cancer after tamoxifen therapy

In the present paper we have studied the quantitative variations in estrogen (ER) and progesterone receptor (PR) content of breast cancer induced by tamoxifen. In addition to receptors, hormonal levels of estradiol, progesterone, prolactin, FSH, LH and testosterone were also measured. The cases included in our study were consecutively selected among those breast cancers in which an aliquot of the tissue sample sent for analysis of the steroid receptors was positive for cancer and also found to have at least one of the steroid receptors positive, not only in the biopsy but also in the surgical specimen. Following this criterion, we finally collected 14 cases of breast cancer treated daily with 30 mg of tamoxifen during an interval of 3 weeks from the initial biopsy to the final surgery. From our results we can conclude that tamoxifen reduced significantly the ER concentration while no changes were observed in PR values. Concerning hormones, while in premenopausal patients tamoxifen induced a rise in plasma estradiol, in postmenopausal women the only modification observed was a decrease in plasma FSH. The variation in steroid receptor content under tamoxifen therapy may also contribute to the evaluation of the hormone dependency of gynecologic malignancies.