Establishment of A Novel Paclitaxel-Resistant Triple-Negative Breast Cancer Cell Line

Objective: Triple-negative breast cancer (TNBC) is one of the most aggressive subtypes of breast cancer, and is associated with poor prognosis. Paclitaxel, a microtubule-binding agent, and chemotherapeutic agent, has been widely used in the management of TNBC. However, acquired chemoresistance is one of the main obstacles leading to ineffective TNBC treatment. Therefore, this study aimed to establish and characterize paclitaxel-resistant triple-negative breast cancer cell lines for investigating the molecular mechanisms of drug resistance.  Material and Methods: Hs578T cancer cell lines were used to develop paclitaxel-resistant (Hs578T-PR) cells, via repeated exposure to increasing concentrations of paclitaxel in a stepwise manner. Drug response and growth curves were then measured by Sulforhodamine B assay. Changes in cell morphology were examined by microscopy. Furthermore, expression of mRNA, related to molecular mechanisms in drug-resistant cells, was identified by using real-time polymerase chain reaction (qPCR).  Results: The Hs578T-PR cell lines were successfully established in just 4 months. They were highly resistant to paclitaxel, with their IC50 and resistance index at 72.8±3.08 nM and 7.4-folds, respectively, compared to the parental cells. For identifying molecular mechanisms underlining paclitaxel resistance, using the RT-qPCR analysis, it was found that Hs578T-PR cells exhibited kinesin family member 3C overexpression. Furthermore, the pro-apoptotic protein BAX was down-regulated; whereas the anti-apoptotic Bcl-2 was up-regulated in Hs578T-PR cells.  Conclusion: Novel, highly paclitaxel-resistant (Hs578T-PR) cell lines established in this study could represent a useful model for identifying the molecular mechanisms of chemoresistance, and for evaluating the efficacy of novel anti-cancer drugs to overcome chemoresistance in TNBC.­­