Effects of all trans retinoic acid on apoptosis induction and notch1, hes1 genes expression in gastric cancer cell line MKN-45

Gastric cancer is one of the most common and lethal malignancies in the world. All-trans retinoic acid (ATRA) has been widely used to treat cancers, most notably for the acute promyelocytic leukemia (APL) - as a differentiation inducer. Notch signaling plays important roles in cell proliferation and apoptosis. Aberrant activation of notch signaling pathway has been stated in different malignancies including gastric cancer. The aim of this study was to assess the possible effects of ATRA on cellular viability, cell cycle shift and apoptosis induction of gastric MKN-45 cell line. Moreover, alterations of notch1 and hes1 gene expression profiles after ATRA treatment have been considered.
Human gastric carcinoma cells (MKN-45) were treated with increasing concentrations of ATRA (2.5, 5, 10, 15, 20, 25 µM). The viability of cells was determined with 3-(4, 5-dimethlthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. Caspase-Glo 3/7 assay kit was applied to measure the apoptosis. Flow-cytometry was employed to distinguish cells in different phases of cell cycle. Expression profiles for the notch1 and hes1 genes were evaluated by reverse transcriptase PCR (RT-PCR).
MTT assay showed that ATRA could diminish MKN-45 cell line viability rate; the most effective dose was 10 µM. Concentrations higher than 10 µM of ATRA had no significant effect on reducing cancerous cell viability. Furthermore, ATRA treatment significantly amplified caspase3/7activation. Flow-cytometry analyses showed significant accumulation of cells in G1 phase of cell cycle in ATRA treated group in compare to control. Following treatment with ATRA, showed a significant reduction in notch1and hes1 genes profile expression.
According to our findings, ATRA could exert its cytotoxic effects on gastric cancer MKN-45 cell line through reducing cellular viability and inducing apoptosis. Remaining at G1 phase of cell cycle and reducing notch1 and hes1 gene expressions suggest the antiproliferative activity of ATRA