Breast cancer cells respond differently to docetaxel depending on their phenotype and on survivin upregulation

SBFI-26 enhances apoptosis in docetaxel-treated triple-negative breast cancer cells by increasing ROS levels

Introduction

Fatty acid binding protein 5 (FABP5) exhibits heightened expression levels in triple-negative breast cancer. The inhibitor of FABP5, Stony Brook fatty acid-binding protein inhibitor 26 (SBFI-26), has demonstrated the capacity to suppress cell proliferation, migration, and invasion. This study delves into the functional mechanism and impact of combining SBFI-26 with docetaxel in treating MDA-MB-231 cells of triple-negative breast cancer.

Methods

Various concentrations of docetaxel and SBFI-26 were chosen for individual or combined treatments. The effects of SBFI-26, docetaxel, or their combination on cell cycle arrest and apoptosis were assessed using flow cytometry. Western blotting was utilised to detect the expression of apoptosis-related proteins, namely cysteinyl aspartate-specific proteases 3 (Caspase3), B cell leukemia/lymphoma 2 (Bcl-2), and Bcl-2 associated X (Bax), while intracellular reactive oxygen species (ROS) levels were determined using a fluorescence spectrophotometer.

Results

The IC50 values for SBFI-26 and docetaxel in inhibiting MDA-MB-231 cells were determined to be 106.1 μM and 86.14 nM, respectively. Significantly, the combination treatment augmented the proportion of G1 phase (apoptotic) cells by 3.67-fold compared to the control group (P < 0.0001). Furthermore, the apoptosis rate in the combination group was 2.59-fold higher than that in the docetaxel group (P < 0.0001) and demonstrated a significant increase of 1.82-fold compared with the SBFI-26 group (P < 0.001). Analyses revealed a decrease in the protein expression of Bcl-2, while Bax and Caspase3 exhibited an increase in the combination group for MDA-MB-231 cells. Moreover, the combined treatment group demonstrated a 2.97-fold increase (P < 0.0001) in ROS fluorescence intensity compared to the control group, a noteworthy 1.39-fold increase (P < 0.01) compared to the SBFI-26 treatment group, and a substantial 1.70-fold increase (P < 0.0001) compared to the docetaxel treatment group.

Conclusion

These findings suggest that the co-administration of SBFI-26 with docetaxel effectively enhances apoptosis in triple-negative breast cancer MDA-MB-231 cells by elevating intracellular ROS levels.

BAD sensitizes breast cancer cells to docetaxel with increased mitotic arrest and necroptosis

Breast cancer patients are commonly treated with taxane (e.g. docetaxel) chemotherapy, despite poor outcomes and eventual disease relapse. We previously identified the Bcl-2-associated death promoter (BAD) as a prognostic indicator of good outcome in taxane-treated breast cancer patients. We also demonstrated that BAD expression in human breast carcinoma cells generated larger tumors in mouse xenograft models. These paradoxical results suggest that BAD-expressing tumors are differentially sensitive to taxane treatment. We validated this here and show that docetaxel therapy preferentially reduced growth of BAD-expressing xenograft tumors. We next explored the cellular mechanism whereby BAD sensitizes cells to docetaxel. Taxanes are microtubule inhibiting agents that cause cell cycle arrest in mitosis whereupon the cells either die in mitosis or aberrantly exit (mitotic slippage) and survive as polyploid cells. In response to docetaxel, BAD-expressing cells had lengthened mitotic arrest with a higher proportion of cells undergoing death in mitosis with decreased mitotic slippage. Death in mitosis was non-apoptotic and not dependent on Bcl-XL interaction or caspase activation. Instead, cell death was necroptotic, and dependent on ROS. These results suggest that BAD is prognostic for favourable outcome in response to taxane chemotherapy by enhancing necroptotic cell death and inhibiting the production of potentially chemoresistant polyploid cells.

Intracellular Delivery of siRNAs Targeting AKT and ERBB2 Genes Enhances Chemosensitization of Breast Cancer Cells in a Culture and Animal Model

: Pharmacotherapy as the mainstay in the management of breast cancer suffers from various drawbacks, including non-targeted biodistribution, narrow therapeutic and safety windows, and also resistance to treatment. Thus, alleviation of the constraints from the pharmacodynamic and pharmacokinetic profile of classical anti-cancer drugs could lead to improvements in efficacy and patient survival in malignancies. Moreover, modifications in the genetic pathophysiology of cancer via administration of small nucleic acids might pave the way towards higher response rates to chemotherapeutics. Inorganic pH-dependent carbonate apatite (CA) nanoparticles were utilized in this study to efficiently deliver various classes of therapeutics into cancer cells. Co-delivery of drugs and genetic materials was successfully attained through a carbonate apatite delivery device. On 4T1 cells, siRNAs against AKT and ERBB2 plus paclitaxel or docetaxel resulted in the largest increase in anti-cancer effects compared to CA/paclitaxel or CA/docetaxel. Therefore, these ingredients were selected for further in vivo investigations. Animals receiving injections of CA/paclitaxel or CA/docetaxel loaded with siRNAs against AKT and ERBB2 possessed significantly smaller tumors compared to CA/drug-treated mice. Interestingly, synergistic interactions in target protein knock down with combinations of CA/AKT/paclitaxel, CA/ERBB2/docetaxel were documented via western blotting.

The PI3K/AKT/mTOR and CDK4/6 Pathways in Endocrine Resistant HR+/HER2- Metastatic Breast Cancer: Biological Mechanisms and New Treatments

Endocrine-based treatments are the normal standard-of-care in women with hormone receptor-positive/Human Epidermal growth factor Receptor 2-negative metastatic breast cancer. Despite the well-known efficacy of these drugs as first-line therapies, about 50% of women develop endocrine resistance and disease progression. The treatment of these patients has represented one of the most important research fields in the last few years, with several multicenter phase II/III trials published or still ongoing. Novel therapies, such as cyclin-dependent kinase (CDK)4/6 and phosphatidylinositol 3-kinase (PI3K)/protein kinase B (AKT)/mammalian target of rapamycin (mTOR) inhibitors, have significantly changed the prognosis of patients progressing to a previous endocrine treatment, allowing a great benefit in terms of progression-free survival and, in some cases, of overall survival. However, identifying response predictors is essential for the rational use of these drugs to avoid unnecessary toxicity and costs, and to ensure the optimal therapeutic sequence is used. In this review, we analyze the PI3K/AKT/mTOR and CDK4/6 pathways and their roles in endocrine resistant metastatic breast cancer. We then focus on the new treatments developed and the roles of these drugs in overcoming endocrine resistance, describing the latest clinical trials that led to the approval of the drugs in clinical practice.

Cell subpopulation deconvolution reveals breast cancer heterogeneity based on DNA methylation signature

Tumour heterogeneity describes the coexistence of divergent tumour cell clones within tumours, which is often caused by underlying epigenetic changes. DNA methylation is commonly regarded as a significant regulator that differs across cells and tissues. In this study, we comprehensively reviewed research progress on estimating of tumour heterogeneity. Bioinformatics-based analysis of DNA methylation has revealed the evolutionary relationships between breast cancer cell lines and tissues. Further analysis of the DNA methylation profiles in 33 breast cancer-related cell lines identified cell line-specific methylation patterns. Next, we reviewed the computational methods in inferring clonal evolution of tumours from different perspectives and then proposed a deconvolution strategy for modelling cell subclonal populations dynamics in breast cancer tissues based on DNA methylation. Further analysis of simulated cancer tissues and real cell lines revealed that this approach exhibits satisfactory performance and relative stability in estimating the composition and proportions of cellular subpopulations. The application of this strategy to breast cancer individuals of the Cancer Genome Atlas's identified different cellular subpopulations with distinct molecular phenotypes. Moreover, the current and potential future applications of this deconvolution strategy to clinical breast cancer research are discussed, and emphasis was placed on the DNA methylation-based recognition of intra-tumour heterogeneity. The wide use of these methods for estimating heterogeneity to further clinical cohorts will improve our understanding of neoplastic progression and the design of therapeutic interventions for treating breast cancer and other malignancies.

Breast Cancer Cell Line Classification and Its Relevance with Breast Tumor Subtyping

Breast cancer cell lines have been widely used for breast cancer modelling which encompasses a panel of diseases with distinct phenotypical associations. Though cell lines provide unlimited homogenous materials for tumor studies and are relatively easy to culture, they are known to accumulate mutations duringthe initial establishment and subsequent series of cultivations. Thus, whether breast cancer cell line heterogeneity reflects that of carcinoma remains an important issue to resolve before drawing any reliable conclusion at the tumor level using cell lines. Inconsistent nomenclatures used for breast cancer cell line subtyping and the different number of subtypes grouped for cell lines and tumors make their direct matching elusive. By analyzing the molecular features of 92 breast cancer cell lines as documented by different literatures, we categorize 84 cell lines into 5 groups to be consistent with breast tumor classification. After combing through these cell lines, we summarized the molecular features, genetically and epigenetically, of each subtype, and manually documented 10 cell lines lacking explicit information on subtyping. Nine cell lines, either found inconsistent on their primary molecular features from different studies or being contaminated at the origin, are not suggested as the first choice for experimental use. We conclude that breast tumor cell lines, though having a high mutational frequency with many uncertainties and could not fully capture breast cancer heterogeneity, are feasible but crude models for tumors of the same subtype. New cell lines with enriched interferon regulated genes need to be established to enlarge the coverage of cell lines on tumor heterogeneity.

Resistance to the mTOR inhibitor everolimus is reversed by the downregulation of survivin in breast cancer cells

Everolimus (RAD001) is an inhibitor of mammalian target of rapamycin used in combination with exemestane to treat hormone receptor-positive advanced breast cancer. However, not all patients are equally sensitive to RAD001 and certain patients develop resistance. Therefore, the present study analyzed the mechanisms involved in the resistance of breast cancer cells to RAD001 in order to identify a potential tool to overcome it. The effects of RAD001 on the inhibition of cell viability, on the induction of apoptosis and autophagy and on the regulation of survivin, an anti-apoptotic protein, were evaluated in two breast cancer cell lines: BT474 (luminal B) and MCF7 (luminal A). RAD001 was demonstrated to induce autophagy in the two cell lines at following a short period of treatment (4 h) and to induce apoptosis exclusively in BT474 cells following longer periods of treatment (48 h). RAD001 induced the downregulation of survivin in BT474 cells and its upregulation in MCF7 cells. Consequently, inhibiting survivin with YM155 resulted in the acquired resistance of MCF7 cells to RAD001 being reverted, restoring RAD001-induced apoptosis. These data demonstrated that RAD001 exerted anti-proliferative and pro-apoptotic effects on breast cancer cells, but that these effects were repressed by the simultaneous up-regulation of survivin. Finally, the results demonstrated that inhibiting the expression of survivin resulted in the restoration of the anti-neoplastic activity of RAD001.

The kinesin Eg5 inhibitor K858 induces apoptosis but also survivin-related chemoresistance in breast cancer cells

Inhibitors of kinesin spindle protein Eg5 are characterized by pronounced antitumor activity. Our group has recently synthesized and screened a library of 1,3,4-thiadiazoline analogues with the pharmacophoric structure of K858, an Eg5 inhibitor. We herein report the effects of K858 on four different breast cancer cell lines: MCF7 (luminal A), BT474 (luminal B), SKBR3 (HER2 like) and MDA-MB231 (basal like). We demonstrated that K858 displayed anti-proliferative activity on every analyzed breast cancer cell line by inducing apoptosis. However, at the same time, we showed that K858 up-regulated survivin, an anti-apoptotic molecule. We then performed a negative regulation of survivin expression, with the utilization of wortmannin, an AKT inhibitor, and obtained a significant increase of K858-dependent apoptosis. These data demonstrate that K858 is a potent inhibitor of replication and induces apoptosis in breast tumor cells, independently from the tumor phenotype. This anti-proliferative response of tumor cells to K858 can be limited by the contemporaneous over-expression of survivin; consequently, the reduction of survivin levels, obtained with AKT inhibitors, can sensitize tumor cells to K858-induced apoptosis.