Alterations of Genetic Variants and Transcriptomic Features of Response to Tamoxifen in the Breast Cancer Cell Line

Background Breast cancer is one of the most important causes of mortality in the world, and Tamoxifen therapy is known as a medication strategy for estrogen receptor-positive breast cancer. In current study, two hypotheses of Tamoxifen consumption in breast cancer cell line (MCF7) were investigated. First, the effect of Tamoxifen on genes expression profile at transcriptome level was evaluated between the control and treated samples. Second, due to the fact that Tamoxifen is known as a mutagenic factor, there may be an association between the alterations of genetic variants and Tamoxifen treatment, which can impact on the drug response. Methods In current study, the whole-transcriptome (RNA-seq) dataset of four investigations (19 samples) were derived from European Bioinformatics Institute (EBI). At transcriptome level, the effect of Tamoxifen was investigated on gene expression profile between control and treatment samples. Moreover, Tamoxifen is known as a mutagenic factor, therefore, its contribution to alterations of genetic variants and drug response were examined. Results Results achieved from RNA-seq analysis indicated the contribution of several candidate genes to tumor suppression process and consequently, the achievement of an effective treatment. For instance, XIAP-associated factor 1 (XAF1) was reported as an up-regulated gene under Tamoxifen therapy. XAF1 is a tumor suppressor that contributes to the apoptosis induction and tumor growth inhibition along with TP53. Results of gene ontology enrichment analysis of differential gene expressions indicated that most of them could considerably lead to the cell death, apoptosis, and negative regulation of proteolysis process. Findings achieved from evaluating Tamoxifen mutagenicity effect on drug response was not confirmed perfectly. The most reported candidate genes, which were related to differential genetic variants between control and treated samples, played the oncogene and tumor suppressor dual roles and also their exact roles in breast cancer were not investigated precisely. Conclusion At transcriptome level, Tamoxifen consumption in MCF7 cell line could be associated with candidate genes and biological pathways that contribute to the apoptosis, proteolysis, and tumor suppression. The mutagenicity effect of Tamoxifen and its contribution to drug response was not confirmed perfectly.

Turning scientific serendipity into discoveries in breast cancer research and treatment: a tale of PhD students and a 50-year roaming tamoxifen team

Purpose This retrospective, about a single “mobile” laboratory in six locations on two continents, is intended as a case study in discovery for trainees and junior faculty in the medical sciences. Your knowledge of your topic is necessary to expect the unexpected. Historical method In 1972, there was no tamoxifen, only ICI 46, 474, a non-steroidal anti-estrogen with little chance of clinical development. No one would ever be foolish enough to predict that the medicine, 20 years later, would achieve legendary status as the first targeted treatment for breast cancer, and millions of women would benefit from long-term adjuvant tamoxifen therapy. The secret of tamoxifen’s success was a translational research strategy proposed in the mid 1970’s. This strategy was to treat only patients with estrogen receptor (ER)-positive breast cancer and deploy 5 or more years of adjuvant tamoxifen therapy to prevent recurrence. Additionally, tamoxifen prevented mammary cancer in animals. Could the medicine prevent breast cancer in women? Results Tamoxifen and the failed breast cancer drug raloxifene became the first selective estrogen receptor modulators (SERMs): a new drug group, discovered at the University of Wisconsin, Comprehensive Cancer Center. Serendipity can play a fundamental role in discovery, but there must be a rigorous preparation for the investigator to appreciate the possibility of a pending discovery. This article follows the unanticipated discoveries when PhD students “get the wrong answer.” The secret of success of my six Tamoxifen Teams was their technical excellence to create models, to decipher mechanisms, that drove the development of new medicines. Summary of advances Discoveries are listed that either changed women’s health or allowed an understanding of originally opaque mechanisms of action of potential therapies. These advances in women’s health were supported entirely by government-sponsored peer-reviewed funding and major philanthropy from the Lynn Sage Breast Cancer Foundation, the Avon Foundation, and the Susan G. Komen Breast Cancer Foundation. The resulting lives saved or extended, families aided in a time of crisis and the injection of billions of dollars into national economies by drug development, is proof of the value of Federal or philanthropic investment into unencumbered research aimed at saving millions of lives.

Prognostic impact of co-expression of LLCL2 and SLC7A5 in ERα-positive breast cancer patients

Background Lethal giant larvae homolog 2 (LLGL2) functions as a promoter of tumor growth and localizes at cell junctions and membranes with solute carrier family 7 member 5 (SLC7A5) in estrogen receptor α (ERα)-positive breast cancer. LLGL2 and SLC7A5 have been reported to be involved in resistance to endocrine therapy. This study aimed to assess the effects of LLGL2/SLC7A5 co-expression in predicting prognosis and response to endocrine therapy in ERα-positive breast cancer patients. Methods The associations of clinicopathological factors with LLGL2 and SLC7A5 expression or LLGL2/SLC7A5 co-expression at the mRNA and protein level were assessed in invasive breast cancer patients with long-term follow-up. The median follow-up period was approximately10 years. Survival curves were analyzed using the Kaplan–Meier method and verified by the log-rank test. A Cox proportional hazards regression analysis was used for univariate and multivariate analyses of prognostic values using stepwise linear regression. Results We identified a positive association between low mRNA expression of LLGL2 or SLC7A5 alone and longer disease-free survival (DFS) and overall survival (OS) in ERα-positive breast cancer patients, but not in ERα-negative patients. We also identified that low LLGL2/SLC7A5 mRNA co-expression (LLGL2low/SLC7A5low) was associated with longer survival compared with other combination groups in all breast cancer patients. In ERα-positive breast cancer patients, LLGL2low/SLC7A5low showed longer survival compared with LLGL2high/SLC7A5high and a positive trend of longer survival compared with other combination groups. We also observed that LLGL2low/SLC7A5low showed longer survival compared with LLGL2high/SLC7A5high in ERα-positive breast cancer patients receiving adjuvant tamoxifen therapy. Multivariate analysis demonstrated that LLGL2low/SLC7A5low was an independent favorable prognostic factor of both DFS and OS in ERα-positive breast cancer patients. High co-expression of LLGL2 and SLC7A5 protein showed a positive trend of shorter survival. Conclusions Our study showed that co-expression of LLGL2 and SLC7A5 mRNA is a promising candidate biomarker and suggested that the LLGL2–SLC7A5 axis may be a therapeutic target in early breast cancer patients, especially in those receiving adjuvant tamoxifen therapy.

CYP2D6 Genotyping for Personalized Therapy of Tamoxifen in Indonesian Women with ER+ Breast Cancer

Tamoxifen is a Selective Estrogen-Receptor Modulator (SERM) commonly prescribed for standard of care in estrogen receptor positive (ER+) breast cancer as an adjuvant therapy. Tamoxifen is metabolized by CYP2D6 into its active metabolite, endoxifen, which has been known to play an important role in reducing risk of ER+ breast cancer recurrence. CYP2D6 is a highly polymorphic gene with more than 100 alleles. The phenotype of this gene is categorized into ultrarapid metabolizer (UM), normal metabolizer (NM), intermediate metabolizer (IM), and poor metabolizer (PM). Certain CYP2D6 polymorphisms may cause reduced activity of this enzyme. Studies have found that reduced CYP2D6 activity in IM and PM patients causes low efficacy of standard tamoxifen therapy. This study aims to observe the distribution of CYP2D6 alleles and its correlation with endoxifen levels in Indonesian ER+ breast cancer patients. 151 patients who have received tamoxifen therapy for at least eight weeks were recruited prospectively. DNA and blood samples were collected with buccal swab and finger-prick methods, respectively. Genotyping was performed using the qPCR method while metabolite level measurement was performed using high performance liquid chromatography tandem mass spectrometry. We found that 40.67% of ER+ breast cancer patients recruited were IM. CYP2D6*10 was the most abundant allele (0.288) in this population, and *10/*36 was the most frequently observed diplotype (0.236). Endoxifen levels between the NM-PM, NM-IM, and IM-PM were statistically significant (p-value = 6.26 x 10-5, 9.12 x 10-5, and 4.714 x 10-3, respectively), and dose increase of tamoxifen to 40 mg daily successfully increased endoxifen levels in IMs to a similar level with NMs at baseline. Given these findings, implementing pharmacogenomic testing of CYP2D6 on ER+ breast cancer women who are about to undergo tamoxifen therapy may be beneficial to increase the likelihood of achieving expected endoxifen levels, thus better treatment efficacy.

Adverse effects of adjuvant tamoxifen treatment on bone mineral density in premenopausal breast cancer patients: A systematic review and meta-analysis.

e12500 Background: It is well known that adjuvant tamoxifen treatment for breast cancer in postmenopausal women decreases bone loss. However, the adverse effect of adjuvant tamoxifen therapy for bone mineral density (BMD) in premenopausal breast cancer patients remains uncertain. This meta-analysis aimed to assess the effects of adjuvant tamoxifen therapy on BMD changes in premenopausal women with primary breast cancer. Methods: Through April 2020, studies reporting BMD changes of lumbar spine or hip in premenopausal women with primary breast cancer treated with adjuvant tamoxifen were collected from EMBASE and PubMed. The pooled analysis was performed using random effects model of the standardized mean difference (SMD) of BMD in patients. Results: A total of 1,432 premenopausal patients from eight studies were included in the pooled analysis. After 3 years of median follow up, adjuvant tamoxifen therapy decreased BMD by as much as SMD of -0.79 [95% confidence interval (CI); -1.25 to -0.33, P < 0.01] at lumbar spines and -0.38 at hip (95%CI; -0.88 to 0.12, P > 0.05). Compared with patients received tamoxifen alone, patients who received combination therapy with chemotherapy or ovarian function suppression (OFS) showed decreased bone loss at lumbar spine (SMD -1.17 with 95%CI -1.59 to -0.75, -0.43 with 95%CI -2.26 to 1.40, and -0.75 with 95%CI -1.38 to -0.13, respectively). Conclusions: Our meta-analysis revealed that premenopausal women who received adjuvant tamoxifen treatment showed significant bone loss over a period of time, especially at lumbar spine. However, tamoxifen attenuated bone loss in those who received tamoxifen after chemotherapy or along with OFS.[Table: see text]

persevERA Breast Cancer (BC): Phase III study evaluating the efficacy and safety of giredestrant (GDC-9545) + palbociclib versus letrozole + palbociclib in patients (pts) with estrogen-receptor-positive, HER2-negative locally advanced or metastatic BC (ER+/HER2– LA/mBC).

TPS1103 Background: Modulating estrogen synthesis and/or ER activity is the mainstay of treatment for pts with ER+ BC. Despite substantial progress, many pts experience relapse during/after adjuvant endocrine therapy. However, even though resistant to aromatase inhibitors (AIs) or tamoxifen, growth and survival of the majority of tumors are thought to remain dependent on ER signaling. Therefore, pts with ER+ BC can still respond to second- or third-line endocrine treatment after progression on prior therapy (Di Leo 2010; Baselga 2012). Therapeutic resistance can arise from mutations in ESR1, which can drive estrogen-independent transcription and proliferation. The highly potent, non-steroidal oral selective ER degrader giredestrant achieves robust ER occupancy and is active regardless of ESR1 mutation status. Phase I data indicate that giredestrant is well tolerated, with encouraging activity as a single agent and in combination with the CDK4/6 inhibitor palbociclib (Lim 2020). Single-agent activity was observed after prior treatment with fulvestrant and/or a CDK4/6 inhibitor (Jhaveri 2019). Methods: persevERA BC (NCT04546009) is a double-blind, placebo-controlled, randomized, multicenter phase III study designed to evaluate the efficacy and safety of first-line giredestrant + palbociclib in pts with ER+/HER2– LA/mBC. Randomization: 1:1 to either giredestrant (30 mg PO) plus letrozole placebo QD or letrozole (2.5 mg PO) plus giredestrant placebo QD on Days 1–28 of each 28-day cycle, with palbociclib (125 mg PO QD) on Days 1–21 of each 28-day cycle. Men and premenopausal women will receive an LHRH agonist. Eligibility: females or males ≥18 years old with measurable disease or evaluable bone disease and no prior treatment for advanced disease. Pts who received prior fulvestrant or who have relapsed within 12 months of completion of (neo)adjuvant therapy with an AI and/or prior therapy with CDK4/6 inhibitor are not eligible; relapse during tamoxifen therapy but > 24 months after the start of tamoxifen therapy is allowed. Stratification: site of disease, disease-free interval since the end of (neo)adjuvant therapy, menopausal status, and geographic region. Primary efficacy endpoint: progression-free survival (determined locally by the investigator per RECIST v1.1). Secondary endpoints include overall survival, objective response rate, duration of response, clinical benefit rate, QoL, and safety. Enrollment is open (first patient in: Oct 9, 2020); target recruitment is 978 pts across all sites in a global enrollment phase. After completion of the global enrollment, additional pts may be enrolled in China. Clinical trial information: NCT04546009 .