B16 and CLS91 mouse melanoma cells susceptibility to apoptosis after vincristin treatment in vitro

Tumor cells' chemoresistance is related to the occurrence or lack of apoptosis. Considering the individual choice of cytostatic drugs for cancer patients and tumor cell resistance the research was undertaken. The viability of mouse melanoma B16 and ClS91 cells and apoptosis induction in vitro after treatment with vincristin was examined. In the future, this kind of study may play an important role in the efficient choice of drug dose and in limiting the side-effects in patients treated with vincristin. Determination of vincristin's influence on cell proliferation kinetics, cell cycle progression based on DNA content and percentage of apoptosis and necrosis in B16 and ClS91 cells, was the object of the present study. The number of viable B16 and ClS91 cells was estimated by flow cytometry analysis. Apoptotic cells were detected using the annexin V-FITC test. Flow cytometric measurement allowed for simultaneous quantitation analysis of four cell subpopulations in the investigated probes. The subpopulations were viable, apoptotic, secondary necrotic and necrotic cells. After adding vincristin into B16 and ClS91 cultures, it was revealed that about 94% ClS91 cells and 45% B16 cells died in the apoptotic way. ClS91 melanoma cells were more sensitive to vincristin treatment than the B16 cell line. The EC50 value for the B16 line was 39.8 microM and for ClS91 was 16.7 microM. Cell cycle was established on the basis of DNA cell content after staining cells with propidium iodide and analysed by flow cytometry. Vincristin induced both B16 and ClS91 cell lines arrest in G2/M cell cycle phase. It was found a correlation between apoptosis occurrence in the melanoma cells and vincristin resistance.