Adjuvant radiotherapy and adjuvant endocrine therapy are commonly given to patients with invasive breast cancer or with ductal carcinoma in situ (DCIS). Although both therapies have been well established through a number of randomized studies, little is known about a possible interaction of both treatment modalities if they are given simultaneously. A number of in vitro studies have indicated that tamoxifen treatment might reduce the intrinsic radiosensitivity of MCF-7 breast cancer cells. Conversely, estradiol treatment increases the intrinsic radiosensitivity of MCF-7 cells. In one available animal study, an antagonistic effect of tamoxifen and ionizing radiation (XRT) could not be observed. Retrospective analyses of randomized clinical studies have not indicated an antagonistic effect of tamoxifen on the effectiveness of XRT, since local control has been consistently higher when XRT was combined with tamoxifen, compared with treatment with XRT alone, regardless of whether tamoxifen was started simultaneously with radiotherapy or after completion of radiotherapy. Currently there are no clinical data available that would suggest an adverse effect of adjuvant tamoxifen treatment started prior to or simultaneously with radiotherapy in breast cancer or DCIS. However, since an antagonistic effect of tamoxifen and simultaneous chemotherapy has been reported recently, the issue of simultaneous versus sequential radiation and tamoxifen treatment in breast cancer should be addressed in further studies.
H Schmidberger, R M Hermann, C F Hess and G Emons
Vanessa W Lim, Jun Li, Yinhan Gong, Aizhen Jin, Jian-Min Yuan, Eu Leong Yong and Woon-Puay Koh
The estrogen levels of Asian women are different from those of Western women, and this could affect estrogen receptor (ER) bioactivity and breast cancer risk. We conducted a case–control study in 169 postmenopausal breast cancer cases and 426 matched controls nested within a population-based prospective cohort study, the Singapore Chinese Health Study, to evaluate the serum levels of estrogens and their receptor (ERα and ERβ)-mediated estrogenic activities in relation to breast cancer risk. Breast cancer cases had higher levels of estrogens and ER-mediated bioactivities in baseline serum than the controls. Compared with those in the lowest quartile, women in the highest quartile for estrone (E1) or ERα-mediated bioactivity had increased breast cancer risk. After additional adjustment for ERβ bioactivity, free estradiol, and E1 levels, serum ERα-mediated bioactivity remained associated with increased breast cancer risk. Compared with those in the lowest quartile, women in the highest quartile for ERα-mediated bioactivity had an odds ratio of 2.39 (95% CI=1.17–4.88; P for trend=0.016). Conversely, the positive association between E1 and cancer risk became null after adjustment for ERα-mediated bioactivity, suggesting that the effect of E1 could be mediated through ERα. Factor(s) contributing to increased ERα-mediated estrogenic bioactivity in serum and its role as a predictor for breast cancer risk need to be validated in future studies.
Frauke Döll, Josef Pfeilschifter and Andrea Huwiler
Sphingosine kinases (SK) catalyze the formation of sphingosine-1-phosphate (S1P) which plays a crucial role in cell growth and survival. Here, we show that prolactin (PRL) biphasically activates the SK-1, but not the SK-2 subtype, in the breast adenocarcinoma cell-line MCF7. A first peak occurs after minutes of stimulation and is followed by a second delayed activation after hours of stimulation. A similar biphasic effect on SK-1 activity is seen for 17β-estradiol (E2). The delayed activation of SK-1 derives from an upregulated mRNA and protein expression and is due to increased SK-1 promoter activity and mechanistically involves STAT5 activation as well as protein kinase C and the classical mitogen-activated protein kinases. Furthermore, glucocorticoids also block both hormone-induced SK-1 expression and activity. Functionally, long-term stimulation of MCF7 cells with PRL or E2 is well known to trigger increased cell proliferation and migration. Both hormone-induced cell responses critically involve SK-1 activation since the depletion of SK-1, but not SK-2, by siRNA transfection abolishes the hormone-induced cell proliferation and migration. In summary, our data show that PRL and E2 cause a pronounced delayed SK-1 activation which is due to increased gene transcription, and critically determines the capability of cells to grow and move. Thus, the SK-1 may represent a novel attractive target for anti-tumor therapy.
I H L Hamelers and P H Steenbergh
Estrogens and insulin-like growth factors (IGFs) act as mitogens promoting cell proliferation in normal breast tissue as well as in breast carcinomas. Both hormones have been shown to play a role in the development of breast cancer and were found to activate multiple signaling pathways leading to proliferation of human breast cancer cell lines in vitro. Originally, it was considered that these agents manifest their mitogenic actions through separate pathways, but a growing body of evidence suggests that the IGF- and estrogen-mediated signaling pathways are intertwined. 17beta-Estradiol (E2) has been shown to enhance IGF signaling at multiple levels. E2 treatment of breast cancer cells alters expression of nearly all of the IGF family members including IGF-I, IGF-II, IGF-binding proteins, IGF type I receptor (IGF-RI), and insulin receptor substrate 1. The ligand-bound estrogen receptor has been reported to bind to and to activate the IGF-RI directly. Vice versa, IGF signaling has been reported to enhance estrogen receptor activation in human breast cancer cells by inducing phosphorylation of the estrogen receptor. Finally, several groups have described synergistic effects of the combination of E2 and IGF-I on S phase entry in breast tumor cell lines. Here, we review recent, often contradictory, reports describing the effects of E2 and IGFs on the proliferation of breast tumor cells, with special emphasis on the synergistic effects of the two hormones.
R Kumar, R K Vadlamudi and L Adam
Homeostasis in normal tissue is regulated by a balance between proliferative activity and cell loss by apoptosis. Apoptosis is a physiological mechanism of cell loss that depends on both pre-existing proteins and de novo protein synthesis, and the process of apoptosis is integral to normal mammary gland development and in many diseases, including breast cancer. The mammary gland is one of the few organ systems in mammals that completes its morphologic development postnatally during two discrete physiologic states, puberty and pregnancy. The susceptibility of the mammary gland to tumorigenesis is influenced by its normal development, particularly during stages of puberty and pregnancy that are characterized by marked alterations in breast cell proliferation and differentiation. Numerous epidemiologic studies have suggested that specific details in the development of the mammary gland play a critical role in breast cancer risk. Mammary gland development is characterized by dynamic changes in the expression profiles of Bcl-2 family members. The expression of Bcl-2 family proteins in breast cancer is also influenced by estradiol and by progestin. Since the ratio of proapoptotic to antiapoptotic proteins determines apoptosis or cell survival, hormone levels may have important implications in the therapeutic prevention of breast cancer.
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.
Deborah J Thompson, Tracy A O'Mara, Dylan M Glubb, Jodie N Painter, Timothy Cheng, Elizabeth Folkerd, Deborah Doody, Joe Dennis, Penelope M Webb, for the Australian National Endometrial Cancer Study Group (ANECS), Maggie Gorman, Lynn Martin, Shirley Hodgson, for the National Study of Endometrial Cancer Genetics Group (NSECG), Kyriaki Michailidou, Jonathan P Tyrer, Mel J Maranian, Per Hall, Kamila Czene, Hatef Darabi, Jingmei Li, Peter A Fasching, Alexander Hein, Matthias W Beckmann, Arif B Ekici, Thilo Dörk, Peter Hillemanns, Matthias Dürst, Ingo Runnebaum, Hui Zhao, Jeroen Depreeuw, Stefanie Schrauwen, Frederic Amant, Ellen L Goode, Brooke L Fridley, Sean C Dowdy, Stacey J Winham, Helga B Salvesen, Jone Trovik, Tormund S Njolstad, Henrica M J Werner, Katie Ashton, Tony Proietto, Geoffrey Otton, Luis Carvajal-Carmona, Emma Tham, Tao Liu, Miriam Mints, for RENDOCAS, Rodney J Scott, Mark McEvoy, John Attia, Elizabeth G Holliday, Grant W Montgomery, Nicholas G Martin, Dale R Nyholt, Anjali K Henders, John L Hopper, Nadia Traficante, for the AOCS Group, Matthias Ruebner, Anthony J Swerdlow, Barbara Burwinkel, Hermann Brenner, Alfons Meindl, Hiltrud Brauch, Annika Lindblom, Diether Lambrechts, Jenny Chang-Claude, Fergus J Couch, Graham G Giles, Vessela N Kristensen, Angela Cox, Manjeet K Bolla, Qin Wang, Stig E Bojesen, Mitul Shah, Robert Luben, Kay-Tee Khaw, Paul D P Pharoah, Alison M Dunning, Ian Tomlinson, Mitch Dowsett, Douglas F Easton and Amanda B Spurdle
Candidate gene studies have reported CYP19A1 variants to be associated with endometrial cancer and with estradiol (E2) concentrations. We analyzed 2937 single nucleotide polymorphisms (SNPs) in 6608 endometrial cancer cases and 37 925 controls and report the first genome wide-significant association between endometrial cancer and a CYP19A1 SNP (rs727479 in intron 2, P=4.8×10−11). SNP rs727479 was also among those most strongly associated with circulating E2 concentrations in 2767 post-menopausal controls (P=7.4×10−8). The observed endometrial cancer odds ratio per rs727479 A-allele (1.15, CI=1.11–1.21) is compatible with that predicted by the observed effect on E2 concentrations (1.09, CI=1.03–1.21), consistent with the hypothesis that endometrial cancer risk is driven by E2. From 28 candidate-causal SNPs, 12 co-located with three putative gene-regulatory elements and their risk alleles associated with higher CYP19A1 expression in bioinformatical analyses. For both phenotypes, the associations with rs727479 were stronger among women with a higher BMI (P interaction=0.034 and 0.066 respectively), suggesting a biologically plausible gene-environment interaction.
M Marino, P Galluzzo, S Leone, F Acconcia and P Ascenzi
Nitric oxide (NO) and 17β-estradiol (E2) are both important in gastrointestinal health and disease. NO contributes to gastrointestinal motility as well as to inflammation and carcinogenic processes. By contrast, E2 reduces the incidence of colon adenoma and carcinoma by about 30%. We report the genomic and non-genomic E2–estrogen receptor (ER) β-induced effects in human colon adenocarcinoma. The effect of NO on ERβ activities was also assessed. The E2-ERβ-dependent gene transcription was inhibited by exogenous NO, whereas some non-genomic E2-dependent effects (e.g. p38/MAP kinase), important for the activation of the apoptotic cascade, were unaffected by NO. However, NO impaired the E2-induced pro-apoptotic cascade in human colon adenocarcinoma cells by inhibiting caspase-3. The effects of NO may reflect chemical modification(s) of Cys residues present in the DNA recognition domain of ERβ as well as in the caspase-3 active site. On the whole, high NO concentrations suppressed the E2 protective effects in the gastrointestinal tract, suggesting that the caspase-dependent apoptotic cascade may become critical under conditions of high redox stress such as occur under specific activation of the immune system by chronic infections or pathogen challenge.
Shelby M King, Tyvette S Hilliard, Lucia Y Wu, Randal C Jaffe, Asgerally T Fazleabas and Joanna E Burdette
Ovarian cancer is the most lethal gynecological malignancy affecting American women. Current hypotheses concerning the etiology of ovarian cancer propose that a reduction in the lifetime number of ovulations decreases ovarian cancer risk. Advanced serous carcinoma shares several biomarkers with fallopian tube epithelial cells, suggesting that some forms of ovarian carcinoma may originate in the fallopian tube. Currently, the impact of ovulation on the tubal epithelium is unknown. In CD1 mice, ovulation did not increase tubal epithelial cell (TEC) proliferation as measured by bromodeoxyuridine incorporation and proliferating cell nuclear antigen staining as compared to unstimulated animals. In superovulated mice, an increase in the number of pro-inflammatory macrophages was detected in the oviduct. Ovulation also increased levels of phospho-γH2A.X in TEC, indicating that these cells were susceptible to double-strand DNA breakage following ovulation. To determine which components of ovulation contributed to DNA damage in the fallopian tube, an immortalized baboon TEC cell line and a three-dimensional organ culture system for mouse oviduct and baboon fallopian tubes were developed. TEC did not proliferate or display increased DNA damage in response to the gonadotropins or estradiol alone in vitro. Oxidative stress generated by treatment with hydrogen peroxide or macrophage-conditioned medium increased DNA damage in TEC in culture. Ovulation may impact the fallopian tube epithelium by generating DNA damage and stimulating macrophage infiltration but does not increase proliferation through gonadotropin signaling.
David Vindrieux, Ludovic Le Corre, Jer-Tsong Hsieh, Raphaël Métivier, Pauline Escobar, Andrès Caicedo, Madly Brigitte and Gwendal Lazennec
The involvement of the coxsackie and adenovirus receptor (CAR), an adhesion molecule known to be the main determinant of adenovirus transduction of the cells, in cancer is currently under investigation. Recent reports suggest that CAR levels are elevated in breast cancer, and this may have an impact on its use as means of delivery for gene therapy. In this study, we show that estradiol (E2) treatment of the estrogen receptor (ER)-positive breast cancer cell MCF-7 increases CAR levels and, in turn, enhances adenoviral transduction. Employing the transfection of CAR promoters in breast cancer cells, we show that this regulation of CAR expression occurs at the transcriptional level. In addition, and by chromatin immunoprecipitation, we have identified a crucial region of CAR promoter that controls E2 responsiveness of CAR gene through the recruitment of ER. Moreover, utilizing CAR antibodies or CAR silencing by RNA interference repressed the estrogen-dependent growth of breast cancer cells, whereas the stable expression of CAR in MCF-7 or MDA-MB-231 cells led to an increased proliferation. Altogether, our data suggest that CAR is a novel estrogen-responsive gene, which is involved in the E2-dependent proliferation of breast cancer cells.