Combination therapy of Paclitaxel and UVB1 in HNSCC and TNBC cells

Abstract

Head and Neck Squamous Cell Carcinoma (HNSCC) and Triple Negative Breast Cancer (TNBC) are heterogeneous and aggres- sive tumors with high mortality and difficult clinical management. Conventional chemotherapy remains as the main clinical manage- ment with the concomitant undesirable side effects for patients and time-limited positive responses. Further research is needed to find novel therapeutic strategies that prolong the patient survival and ensure a better quality of life. The aim of the present study was to evaluate the antitumor potential of the combination of the conven- tional chemotherapeutic agent Paclitaxel (PTX) with the non-hyper- calcemic Calcitriol analog UVB1 in HNSCC and TNBC cells. Cell viability was evaluated by crystal violet assays in human HN13 and HN12 HNSCC and murine 4T1 TNBC cell lines treated with vehicle, UVB1, PTX or combination of drugs. The results show that UVB1 (1μM) with low concentrations of PTX displayed a greater reduc- tion in viability with respect to control and monotherapies in all cell lines tested (120h of treatment, p<0.001). Apoptosis analyses were performed in 4T1 cells by flow cytometry with Propidium Iodide and Annexin V-FITC staining. The percentage of cells in early apopto- sis was higher in cells treated with UVB1 or UVB1 (1μM) + PTX (1nM) compared to PTX alone or vehicle (p<0.001). In order to eval- uate the Vitamin D Receptor (VDR) role in these antitumor effects, VDR was overexpressed in 4T1 cells with a pcDNA3-VDR plasmid. Transfected cells were selected and the overexpressed of VDR was checked by RT-qPCR, WB and IFI. The viability studies carried out with these cells showed that PTX displayed a higher antitumor ef- fect in 4T1-pcDNA3-VDR cells compared to 4T1-pcDNA3-CTL cells (p<0.001). These results encourage us to continue evaluating this combination therapy in HNSCC and TNBC cells, as well as VDR role in the antineoplastic effects of these chemotherapeutic drugs.