The estrogen dependency of human breast cancer has been successfully exploited in the treatment of early and advanced diseases and provides a unique opportunity for chemoprevention of this common malignancy. Preliminary results with the antiestrogens Tamoxifen and Raloxifene show an encouraging reduction in the incidence of breast cancer. Alternative approaches include the use of highly selective and non-toxic aromatase inhibitors and, in premenopausal women, the use of LHRH agonists in conjunction with the administration of small doses of estrogen and progesterone. The rationale for these chemopreventive strategies and their possible limitations are briefly discussed.
There is definitely a need for the development of new drugs for the treatment and cure of endometrial cancer. In addition there are various new drugs or phyto-remedies under development which are intended for use in the treatment and prevention of breast cancer, for the treatment of menopausal symptoms and for hormone replacement therapy. The efficacy of novel drugs targeting steroid receptors in endometrial cancers has to be evaluated and the safety of other endocrine measures on endometrial cancers or on endometrial carcinogenesis has to be assessed. For these experimental purposes five main classes of experimental models are available: spontaneous endometrial tumorigenesis models in inbred animals (Donryu rats, DA/Han rats, BDII/Han rats), inoculation tumors from chunks of tumors (rat EnDA-tumor, human EnCa 101 tumor) or from inoculated tumor cell lines (rat RUCA-I cells, human Ishikawa and ECC-1 cells), developmental estrogenic exposure or chemical carcinogen exposure of CD-1 and ICR mice, transgenic approaches such as mice heterozygous regarding the tumor suppressor gene PTEN (pten(+/-)-mice) and endometrial tumor cell lines cultured under conditions promoting in vivo-like morphology and functions e.g. cell culture on reconstituted basement membrane. Although the number of models is comparatively small, most aspects related to functions of estrogenic or gestagenic substances are assessable, particularly if various experimental models are combined. Whereas models based on human endometrial adenocarcinoma cells are widely used, the properties and advantages of animal-derived models have mainly been ignored so far.
Rosalinda M Savoy and Paramita M Ghosh
Estrogens were once used for the treatment of prostate cancer (PC). They may still be used in various parts of the world to that effect. Recent developments in the understanding of a role for estrogen receptor β (ERβ) in the development and progression of this disease resurrect the discussion on the intertwined roles of ERβ and the androgen receptor (AR) in promoting PC. A new article by Zellweger et al. in Endocrine-Related Cancer investigates the expression and assesses the activity of ERα and ERβ as well as the AR, in addition to a phosphorylated form of AR in hormone-naïve and castration-resistant PC.
M Fuertes, M Sapochnik, L Tedesco, S Senin, A Attorresi, P Ajler, G Carrizo, A Cervio, G Sevlever, J J Bonfiglio, G K Stalla, and E Arzt
Increased levels of the proto-oncogene pituitary tumor-transforming gene 1 (PTTG) have been repeatedly reported in several human solid tumors, especially in endocrine-related tumors such as pituitary adenomas. Securin PTTG has a critical role in pituitary tumorigenesis. However, the cause of upregulation has not been found yet, despite analyses made at the gene, promoter and mRNA level that show that no mutations, epigenetic modifications or other mechanisms that deregulate its expression may explain its overexpression and action as an oncogene. We describe that high PTTG protein levels are induced by the RWD-containing sumoylation enhancer (RWDD3 or RSUME), a protein originally identified in the same pituitary tumor cell line in which PTTG was also cloned. We demonstrate that PTTG and RSUME have a positive expression correlation in human pituitary adenomas. RSUME increases PTTG protein in pituitary tumor cell lines, prolongs the half-life of PTTG protein and regulates the PTTG induction by estradiol. As a consequence, RSUME enhances PTTG transcription factor and securin activities. PTTG hyperactivity on the cell cycle resulted in recurrent and unequal divisions without cytokinesis, and the consequential appearance of aneuploidies and multinucleated cells in the tumor. RSUME knockdown diminishes securin PTTG and reduces its tumorigenic potential in a xenograft mouse model. Taken together, our findings show that PTTG high protein steady state levels account for PTTG tumor abundance and demonstrate a critical role of RSUME in this process in pituitary tumor cells.
Haojun Luo, Guanglun Yang, Tenghua Yu, Shujuan Luo, Chengyi Wu, Yan Sun, Manran Liu, and Gang Tu
Cancer-associated fibroblasts (CAFs) are crucial co-mediators of breast cancer progression. Estrogen is the predominant driving force in the cyclic regulation of the mammary extracellular matrix, thus potentially affecting the tumor-associated stroma. Recently, a third estrogen receptor, estrogen (G-protein-coupled) receptor (GPER), has been reported to be expressed in breast CAFs. In this study, GPER was detected by immunohistochemical analysis in stromal fibroblasts of 41.8% (59/141) of the primary breast cancer samples. GPER expression in CAFs isolated from primary breast cancer tissues was confirmed by immunostaining and RT-PCR analyses. Tamoxifen (TAM) in addition to 17β-estradiol (E2) and the GPER agonist G1 activated GPER, resulting in transient increases in cell index, intracellular calcium, and ERK1/2 phosphorylation. Furthermore, TAM, E2, and G1 promoted CAF proliferation and cell-cycle progression, both of which were blocked by GPER interference, the selective GPER antagonist G15, the epidermal growth factor receptor (EGFR) inhibitor AG1478, and the ERK1/2 inhibitor U0126. Importantly, TAM as well as G1 increased E2 production in breast CAFs via GPER/EGFR/ERK signaling when the substrate of E2, testosterone, was added to the medium. GPER-induced aromatase upregulation was probably responsible for this phenomenon, as TAM- and G1-induced CYP19A1 gene expression was reduced by GPER knockdown and G15, AG1478, and U0126 administration. Accordingly, GPER-mediated CAF-dependent estrogenic effects on the tumor-associated stroma are conceivable, and CAF is likely to contribute to breast cancer progression, especially TAM resistance, via a positive feedback loop involving GPER/EGFR/ERK signaling and E2 production.
Srilatha Swami, Aruna V Krishnan, Lihong Peng, Johan Lundqvist, and David Feldman
Calcitriol (1,25-dihydroxyvitamin D3), the hormonally active metabolite of vitamin D, exerts its anti-proliferative activity in breast cancer (BCa) cells by multiple mechanisms including the downregulation of the expression of estrogen receptor α (ER). We analyzed an ∼3.5 kb ER promoter sequence and demonstrated the presence of two potential negative vitamin D response elements (nVDREs), a newly identified putative nVDRE upstream at −2488 to −2473 bp (distal nVDRE) and a previously published sequence (proximal nVDRE) at −94 to −70 bp proximal to the P1 start site. Transactivation analysis using ER promoter deletion constructs and heterologous promoter–reporter constructs revealed that both nVDREs functioned to mediate calcitriol transrepression. In the electrophoretic mobility shift assay, the vitamin D receptor (VDR) showed strong binding to both nVDREs in the presence of calcitriol, and the chromatin immunoprecipitation assay demonstrated the recruitment of the VDR to the distal nVDRE site. Mutations in the 5′ hexameric DNA sequence of the distal nVDRE resulted in the loss of calcitriol-mediated transrepression and the inhibition of protein–DNA complex formation, demonstrating the importance of these nucleotides in VDR DNA binding and transrepression. A putative nuclear factor-Y (NFY) binding site, identified within the distal nVDRE, led to the findings that NFY bound to the distal nVDRE site interfered with the binding of the VDR at the site and reduced calcitriol-mediated transrepression. In conclusion, the ER promoter region contains two negative VDREs that act in concert to bind to the VDR and both nVDREs are required for the maximal inhibition of ER expression by calcitriol. The suppression of ER expression and estrogen-mediated signaling by calcitriol in BCa cells suggests that vitamin D may be useful in the treatment of ER+ BCa.
R A Janknegt and T A Boon
Hormonal therapy alone for metastatic prostate cancer is effective in reducing tumour growth for a limited period of time. Progression of the tumour after an initial good response is due to the development of hormone-resistant cells. It is not known whether hormone-resistant cells develop as a mutation of the original hormone-sensitive cell later on in the progress of the disease or from early on as a separate entity. Chemotherapy has been used as second-line treatment with an average gain of only a few weeks over hormonal palliation. No studies of primary treatment with chemotherapy alone have been done. Some combined hormo-chemotherapy studies have shown some improvement in time to progression but not in survival
We have performed a multicentre randomized study comparing hormonal treatment (orchiectomy) versus hormo-chemotherapy (orchiectomy plus a high dosage of estramustin). This included 419 patients over 2 years: 281 M+ patients and 108 MO N+. The dosage of estramustin (Estracyt) was 840 mg/day (first month) and 560 mg/day thereafter.
The results showed that, in the M+ patients, median time to progression differed by 6 months for the hormo-chemotherapy-treated group (P=0.02). Median time to survival was not different in both groups, but multivariate analysis showed a 3-month difference in the group younger than 70 years in favour of the estramustin-treated group (P=0.0007). In the MO N+ patients, growth was slower. In both groups median time to progression and survival had not been reached after 35 months. Toxicity in the orchiectomy plus estramustin-treated group was low: there were no cardiovascular side-effects. Nausea was a problem during the first 4 weeks.
In our series pain and alkaline phosphatase were the main prognostic factors.
In conclusion, primary hormo-chemotherapy combined with estramustin showed a significant difference in time to progression (quality of life) but a limited survival benefit for a specific age group. In a future study we shall study patients with poor prognostic factors only.
Endocrine-Related Cancer (1996) 3 285-292
R I Nicholson, C Staka, F Boyns, I R Hutcheson, and J M W Gee
There is an increasing body of evidence demonstrating that elevated growth signaling in breast cancer cells can promote forms of endocrine resistance in either an estrogen receptor-dependent or -independent manner. The current article reviews what is known about such growth factor signaling networks and resistance to estrogen withdrawal and considers the many novel therapeutic opportunities that stem from this knowledge.
Cameron M Armstrong, Autumn R Billimek, Kimberly F Allred, Joseph M Sturino, Brad R Weeks, and Clinton D Allred
Postmenopausal women on estrogen replacement therapy (ERT) have a reduced risk of developing colon cancer compared with postmenopausal women not on ERT, suggesting a role for estradiol (E2) in protection against this disease. To determine whether E2 protects against inflammation-associated colon cancer when administered following the initiation of colonic DNA damage, in this study, we implanted E2-containing pellets into mice after co-treatment with azoxymethane and two rounds of dextran sulfate sodium (DSS). Wild-type (WT) E2-treated mice had reduced numbers and average area of adenocarcinomas compared with the control mice. These effects were lost in estrogen receptor-β (Er β (Esr2)) knockout mice. Surprisingly, apoptosis was reduced and cell proliferation was increased in sections from tumors of the WT E2 mice compared with the WT control mice. These findings are probably due, in part, to a reduction in ERβ expression in colonic epithelial cells as the cells progressed from a non-malignant to a cancerous state as enhanced apoptosis was observed in normal colonocytes expressing higher levels of ERβ. Furthermore, epithelial cells within the tumors had dramatically increased ERα mRNA and protein expression compared with the non-diseased mice. We conclude that while E2 treatment resulted in an overall suppression of colonic adenocarcinoma formation, reduced ERβ expression accompanied by enhanced ERα expression caused an altered colonocyte response to E2 treatment compared with the earlier stages of colon cancer development. These data are the first examples of decreased ERβ expression concurrent with increased ERα expression as a disease develops and highlight the importance of understanding the timing of E2 exposure with regard to the prevention of inflammation-associated colon cancer.
A Bottini, A Berruti, M P Brizzi, A Bersiga, D Generali, G Allevi, S Aguggini, G Bolsi, S Bonardi, B Tondelli, F Vana, M Tampellini, P Alquati, and L Dogliotti
This study was designed to address whether simultaneous primary chemo-hormonal therapy provides additional activity compared with chemotherapy alone in breast cancer patients with operable or locally advanced disease. Between January 1997 and January 2002, 211 consecutive patients with T2–4, N0–1, M0 breast cancer were randomized to receive either epirubicin alone (EPI) or epirubicin plus tamoxifen (EPI-TAM). Ki67 expression was evaluated immunohistochemically in tumor specimens obtained before chemotherapy by incision biopsy and at definitive surgery. Tumor shrinkage of >50% was obtained in 76% of patients randomized in the EPI arm and 81.9% of patients randomized in the EPI-TAM arm (not significant). The corresponding rates of clinical and pathological complete response were 20.2 and 21.9% (not significant), and 4.8 and 6.7% (not significant), respectively. Pathologically complete response was more frequently observed in estrogen receptor (ER)-negative (ER−) tumors (P=0.04) and correlated with elevated baseline Ki67 expression (P<0.01). Both EPI and EPI-TAM treatments resulted in a significant reduction in Ki67 expression, either in overall patients (P=0.000) or in patients with ER+ breast cancer (P=0.000). The reduction in Ki67 immunostaining in the EPI-TAM arm was greater than in the EPI arm, leading to a lower Ki67 expression at post-operative residual histology (P=0.0041). The addition of tamoxifen to epirubicin chemotherapy did not improve the response rate but led to a significantly higher reduction in the Ki67 expression. Baseline elevated Ki67 expression and the ER− status were both associated with a greater chance of obtaining a pathological complete response at residual histology.