Mechanistic Studies of Cytotoxic Activity of the Mesoionic Compound MIH 2.4Bl in MCF-7 Breast Cancer Cells

Purpose: In this work, we examined the cytotoxic effect of a 1,3-thiazolium-5-thiolate derivative of a mesoionic compound (MIH 2.4Bl) on the MCF-7 breast cancer cell line. Methods: The cytotoxic effect of MIH 2.4Bl was determined using a crystal violet assay. The effect of MIH 2.4Bl on mitochondrial respiration was characterized by an oxygen consumption rate (OCR) analysis. Autophagy induction by MIH 2.4Bl was examined by measuring changes in protein markers. Microarray analysis was performed to assess changes in gene expression after MIH 2.4Bl treatment. Six genes were selected for expression verification by RT-qPCR, including ACRC, AMIGO2, ATF3, DKK1, HBEGF, and RGS2. Results: An IC50 value of 45.8 +/- 0.8 µM was determined for MIH 2.4Bl. Increasing concentrations of MIH 2.4Bl resulted in a reduction of all mitochondrial respiration parameters compared to control cells, indicative of an overall decrease in mitochondrial membrane potential. Western blot analysis showed the with MIH 2.4Bl resulted in increased protein expression of Beclin-1 and ATG5 and an increase in the in LC3B-II/LC3B-I ratio compared to control cells. We demonstrated 3644 genes with a fold-change ? 2 change with 775 up-regulated and 2869 down-regulated by MIH 2.4Bl compared with control cells. RT-qPCR analysis of RNA isolated from control and MIH-2.4Bl treated MCF-7 cells showed a correlation of altered expression levels with changes in expression identified by microarray analysis. Conclusion: These results suggest that MIH 2.4Bl is a promising candidate for treating breast cancer.