294 Vitamin D enhances anticancer properties of cediranib, a VEGFR inhibitor, by modulation of VEGFR2 expression in human melanoma cells

Abstract

Melanoma, representing a minor fraction of all skin malignancies, is linked to vast majority of deaths from skin tumors. Regardless of the pathbreaking recent treatment options resistance inevitably develops in patients, emphasizing the need for novel therapeutic options. Recently we have shown, that vitamin D enhances the effectiveness of classical chemotherapeutics in human malignant melanoma A375 cell line. In the current study we are testing whether vitamin D analogs will enhance activity of the anti-angiogenic compound, cediranib (AZD-2171). Human A375 melanoma cells were pretreated with 1,25(OH)2D3 or with its low-calcemic analog, calcipotriol and subsequently were exposed to cediranib. Cell proliferation was established using SRB assay. Cell cycle and extracellular expression of VEGFR2 were analyzed by flow cytometry. The mobility of melanoma cells was assessed as a live imaging with Olympus cell Vivo IX 83. The protein level of VEGFR1-2 was established with immunoblotting and relative mRNA levels were determined by a Real-Time PCR. Simultaneous treatment with cediranib and 1,25(OH)2D3 or calcipotriol resulted in a profound decrease in the proliferation of melanoma cells (30% and 43% maximal inhibition of melanoma cells proliferation for cediranib and 1,25(OH)2D3 or calcipotriol vs 6% for cediranib alone). Preincubation of melanoma cells with 1,25(OH)2D3 or with calcipotriol prior to cediranib treatment resulted in an increase in the percentage of cells in the G2/M phase in comparison to cells without pretreatment, profoundly diminished cellular mobility and increased the expression of VEGFR2 at protein and mRNA levels. In conclusion, vitamin D pretreatment enhanced the cytotoxic efficacy of cediranib in A375 melanoma cells by modulation of VEGFR2 expression. Vitamin D analogs may be therefore considered as beneficial adjuvant agents in anti-melanoma therapy, especially in vitamin D deficient patients.