Hematopoietic Pbx-Interaction Protein Promotes Breast Cancer Sensitivity To Paclitaxel Through A Microtubule-Dependent Mechanism

Aims: Recently, microtubule-binding proteins (MBPs) have been implicated in modulation of paclitaxel sensitivity in many cancers, highlighting their potential as biomarkers predictive of treatment outcomes and as therapeutic targets that can be pharmacologically manipulated. This study is aimed to determine the impact of the MBP hematopoietic PBX-interaction protein (HPIP) on breast cancer cell sensitivity to paclitaxel. Results: In this study, we show that breast cancer cells (MCF-7 and MDA-MB-231) overexpressing HPIP were more sensitive to paclitaxel treatment as evaluated by MTT assay, exhibiting a significant reduction in IC50 of paclitaxel compared with the control. In transwell assay, breast cancer cells overexpressing HPIP, but not the cells transfected with empty vector, showed significant migration inhibition in response to paclitaxel. Furthermore, in vitro assays show that combined HPIP and paclitaxel enabled a more rapid and more complete microtubule assembly than paclitaxel alone, and accordingly HPIP plus paclitaxel-stabilized microtubule displayed slower dissociation dynamics upon dilution and cooling. Notably, overexpression of HPIP decreased the cellular level of HDAC6, leading to increased acetylation of tubulin as shown by Western blot and immunofluorescence imaging analysis. Conclusions: Collectively, HPIP sensitized breast cancer cells to paclitaxel through a microtubule-dependent mechanism. Our finding hints at a clinical value of HPIP in breast cancer patient selection for paclitaxel-based regimens in the context of precision medicine.