Natural Hypoxia is Not a Limiting Factor in Evaluating the Novel Arylidene Derivative MLT-401 Against an In Vitro Colorectal Cancer Model.

BACKGROUND/AIMS: Cancer cells in vivo develop resistance to many anti-tumor drugs. One known factor to influence such drug resistance is hypoxia, which is an important component of the tumor microenvironment. Standard cancer lines mostly do not exhibit a cellular hypoxic microenvironment and there is a paucity of information on the efficacy of lead molecules in both cellular- and environment-induced hypoxic conditions. Therefore, in the present study, we have evaluated the efficacy of the arylidene derivative MLT-401, a lead molecule showing activity against colorectal cancer model using the HCT 116 cell line and CCD-80-C control cells in normoxic and natural (marginal) hypoxic conditions, which is usually observed in high-altitude regions.

METHODS: The efficacy of MLT-401 on HCT 116 and CCD-80-C cells were tested in both normoxia and marginal hypoxia conditions. MTT assay was used to evaluate cell proliferation, Annexin V binding assay for apoptotic cell quantification and PI staining for cell cycle were done by flow cytometry. Induction of pro-apoptotic marker BAX and anti-apoptotic Bcl-2 were assessed by western blot. Bcl-2/BAX ratio was calculated based on protein expression by western blotting and bands were quantified by Image J software.

RESULTS: Analysis of cell proliferation showed an average 10-fold reduction in the inhibition of HCT 116 cells in hypoxic conditions with approximately 500 nM MLT-401, while there was no significant change noted in marginal hypoxic conditions. A proportionate increase in the number of apoptotic cells and large M4 fraction of 10.5% and 26.7% of HCT116 against 6.3% of control cells in cell cycle assessment with MLT-401 concentrations ranging from 250 to 500 nM respectively clearly demonstrated anti-cancer activity. A Bcl-2/BAX ratio of < 1 showed that the induction of apoptosis was the gross mechanism underlying the inhibition of HCT 116 cells by MLT-401.

CONCLUSION: Collectively, these results show MLT-401 as an effective anti-colorectal cancer lead molecule irrespective of normoxia or natural hypoxia.