Vitamin D enhances the sensitivity of breast cancer cells to the combination therapy of photodynamic therapy and paclitaxel

VD could enhance the therapeutic effects of ALA-PDT combined with PTX on tumor growth and cell apoptosis.

Thiazolyl blue tetrazolium bromide assay was conducted to gauge the viability of breast cancer cells treated with ALA-PDT and PTX alone or in combination. The cell migration, invasion and apoptosis were measured by wound healing, transwell and flow cytometry assays, respectively. Xenograft tumor models were established and tumor volume and weight were recorded. The expression of Bcl-2, Bax and cleaved caspase-3 in cells and tumor tissues was determined by western blot assay.

Given that Vitamin D (VD) has been confirmed to reinforce the toxic effects of 5-aminolevulinic acid-based photodynamic therapy (ALA-PDT) towards breast cancer, this study was designed to decipher the combined effects of VD, ALA-PDT and paclitaxel (PTX).

Both ALA-PDT and PTX alone inhibited viability in a dose-dependent manner, blocked migration and invasion, boosted apoptosis, down-regulated Bcl-2 expression and upregulated the expression of Bax and cleaved caspase-3 in breast cancer cells. More significant effects on the above-mentioned factors were induced by ALA-PDT and PTX in combination. Moreover, ALA-PDT and PTX in combination also suppressed the growth of xenograft tumors and Bcl-2 expression while promoting the expression of Bax and cleaved caspase-3 in tumors. In contrast, VD had no effect on tumor growth and the expression of Bcl-2, Bax and cleavedcaspase-3, but intensified the combined effects of ALA-PDT and PTX.