Effect of low doses of estradiol and tamoxifen on breast cancer cell karyotypes

The Complexity of Response to the Proliferation Agonist and Antagonist Agents, in the Breast Cancer Cell Lines with Various Receptors

Breast cancer is a heterogeneous disease in which many factors and receptors are effective in the disease process and response to treatment. Currently, estrogen, progesterone, and HER2 receptors are among the most important factors in choosing a treatment regimen. Other metabolic factors that may affect the treatment outcome include diabetes and hyperinsulinemia. In order to evaluate the role and complexity of cross-talk between different pathways initiating from various receptors, value the most common drugs in the treatment of breast cancer are investigated on different cell lines in this manuscript at the cell culture level. The result of different doses of Tamoxifen and estradiol on the cells with various levels of the estrogenic, progesterone, and HER2 receptors is examined alone, or in combinations, and the presence or absence of insulin. The effects of these variables on the cells' growth pattern and survival in various breast cancer cells are investigated using cell counting, colony counting, and MTT assays. Our results have further confirmed the complexity of deciding on the outcome of treatment for breast cancer with such a wide variability in the kind of receptors and biochemical agents present in the body of a cancer patient.

17β-estradiol at low concentrations attenuates the efficacy of tamoxifen in breast cancer therapy

Tamoxifen has been applied widely in the treatment of estrogen receptor (ER)-positive breast cancer. The impact of low concentrations of 17β-estradiol (E2) (a pervasive environmental pollutant) on its effectiveness was studied in vitro using an MCF-7 cell line. Cell proliferation, migration, invasion, and apoptosis were studied along with cell cycle progression, reactive oxygen species generation and mitochondrial membrane potentials repression. The signaling pathways involved were identified. Typical concentrations of E2 in the environment (10^-10 to 10^-8 M) were observed to promote cell growth and protect MCF-7 cells from tamoxifen's cytotoxicity. Cell migration, invasion, cell cycle progression and apoptosis all involved in reducing tamoxifen's cytotoxicity. E2 at environmental concentrations induced PI3K/Akt and MAPK/ERK signal transduction through the estrogen receptor pathways to affect cell proliferation. Taken together, the results explain how E2 in the environment may attenuate the efficacy of tamoxifen in ER-positive breast cancer therapy. They provide considerable support for E2's adverse effects on human health and cancer management.

A genome-wide association study identifies three novel genetic markers for response to tamoxifen: A prospective multicenter study

Purpose

Although association studies of genetic variations with the clinical outcomes of breast cancer patients treated with tamoxifen have been reported, genetic factors which could determine individual response to tamoxifen are not fully clarified. We performed a genome-wide association study (GWAS) to identify novel genetic markers for response to tamoxifen.

Experimental design

We prospectively collected 347 blood samples from patients with hormone receptor-positive and human epidermal growth factor receptor 2-negative, invasive breast cancer receiving preoperative tamoxifen monotherapy for 14 to 28 days. We used Ki-67 response in breast cancer tissues after preoperative short-term tamoxifen therapy as a surrogate marker for response to tamoxifen. We performed GWAS and genotype imputation using 275 patients, and an independent set of 72 patients was used for replication study.

Results

The combined result of GWAS and the replication study, and subsequent imputation analysis indicated possible association of three loci with Ki-67 response after tamoxifen therapy (rs17198973 on chromosome 4q34.3, rs4577773 on 6q12, and rs7087428 on 10p13, P_combined = 5.69 x 10⁻⁶, 1.64 x 10⁻⁵, and 9.77 x 10⁻⁶, respectively). When patients were classified into three groups by the scoring system based on the genotypes of the three SNPs, patients with higher scores showed significantly higher after/before ratio of Ki-67 compared to those with lower scores (P = 1.8 x 10⁻¹²), suggesting the cumulative effect of the three SNPs.

Conclusion

We identified three novel loci, which could be associated with clinical response to tamoxifen. These findings provide new insights into personalized hormonal therapy for the patients with breast cancer.

Chemoprevention of LA7-Induced Mammary Tumor Growth by SM6Met, a Well-Characterized Cyclopia Extract

Breast cancer (BC) is the leading cause of cancer-related deaths in women. Chemoprevention of BC by using plant extracts is gaining attention. SM6Met, a well-characterized extract of Cyclopia subternata with reported selective estrogen receptor subtype activity, has shown tumor suppressive effects in a chemically induced BC model in rats, which is known to be estrogen responsive. However, there is no information on the estrogen sensitivity of the relatively new orthotopic model of LA7 cell-induced mammary tumors. In the present study, the potential chemopreventative and side-effect profile of SM6Met on LA7 cell-induced tumor growth was evaluated, as was the effects of 17β-estradiol and standard-of-care (SOC) endocrine therapies, such as tamoxifen (TAM), letrozole (LET), and fulvestrant (FUL). Tumor growth was observed in the tumor-vehicle control group until day 10 post tumor induction, which declined afterward on days 12-14. SM6Met suppressed tumor growth to the same extent as TAM, while LET, but not FUL, also showed substantial anti-tumor effects. Short-term 17β-estradiol treatment reduced tumor volume on days prior to day 10, whereas tumor promoting effects were observed during long-term treatment, which was especially evident at later time points. Marked elevation in serum markers of liver injury, which was further supported by histological evaluation, was observed in the vehicle-treated tumor control, TAM, LET, and long-term 17β-estradiol treatment groups. Alterations in the lipid profiles were also observed in the 17β-estradiol treatment groups. In contrast, SM6Met did not augment the increase in serum levels of liver injury biomarkers caused by tumor induction and no effect was observed on lipid profiles. In summary, the results from the current study demonstrate the chemopreventative effect of SM6Met on mammary tumor growth, which was comparable to that of TAM, without eliciting the negative side-effects observed with this SOC endocrine therapy. Furthermore, the results of this study also showed some responsiveness of LA7-induced tumors to estrogen and SOC endocrine therapies. Thus, this model may be useful in evaluating potential endocrine therapies for hormone responsive BC.

ADA3 regulates normal and tumor mammary epithelial cell proliferation through c-MYC

Background

We have established the critical role of ADA3 as a coactivator of estrogen receptor (ER), as well as its role in cell cycle progression. Furthermore, we showed that ADA3 is predominantly nuclear in mammary epithelium, and in ER+, but is cytoplasmic in ER- breast cancers, the latter correlating with poor survival. However, the role of nuclear ADA3 in human mammary epithelial cells (hMECs), and in ER+ breast cancer cells, as well as the importance of ADA3 expression in relation to patient prognosis and survival in ER+ breast cancer have remained uncharacterized.

Methods

We overexpressed ADA3 in hMECs or in ER+ breast cancer cells and assessed the effect on cell proliferation. The expression of ADA3 was analyzed then correlated with the expression of various prognostic markers, as well as survival of breast cancer patients.

Results

Overexpression of ADA3 in ER- hMECs as well as in ER+ breast cancer cell lines enhanced cell proliferation. These cells showed increased cyclin B and c-MYC, decreased p27 and increased SKP2 levels. This was accompanied by increased mRNA levels of early response genes c-FOS, EGR1, and c-MYC. Analysis of breast cancer tissue specimens showed a significant correlation of ADA3 nuclear expression with c-MYC expression. Furthermore, nuclear ADA3 and c-MYC expression together showed significant correlation with tumor grade, mitosis, pleomorphism, NPI, ER/PR status, Ki67 and p27 expression. Importantly, within ER+ cases, expression of nuclear ADA3 and c-MYC also significantly correlated with Ki67 and p27 expression. Univariate Kaplan Meier analysis of four groups in the whole, as well as the ER+ patients showed that c-MYC and ADA3 combinatorial phenotypes showed significantly different breast cancer specific survival with c-MYC-high and ADA3-Low subgroup had the worst outcome. Using multivariate analyses within the whole cohort and the ER+ subgroups, the significant association of ADA3 and c-MYC expression with patients’ outcome was independent of tumor grade, stage and size, and ER status.

Conclusion

ADA3 overexpression enhances cell proliferation that is associated with increased expression of c-MYC. Expression patterns with respect to ADA3/c-MYC can divide patients into four significantly different subgroups, with c-MYC High and ADA3 Low status independently predicting poor survival in patients.

Electronic supplementary material

The online version of this article (doi:10.1186/s13058-016-0770-9) contains supplementary material, which is available to authorized users.