The differential effect of AICAR on c-Myc expression and proliferation in specific tumor cell lines / 中国药理学通报

ABSTRACT

Aim To investigate the effect of AICAR on the expression of the proto-oncogene c-Myc and cell proliferation rates in specific cancer cell lines. Methods The mRNA levels of c-Myc were evaluated using fluorescence-based qRT-PCR to examine the effect of AICAR treatment on c-Myc mRNA expression levels. Western blot was used to evaluate the protein levels of c-Myc following AICAR treatment. RNA interference was employed to determine whether the regulatory effect of AICAR on c-Myc was dependent on AMPK and the downstream metabolic enzymes relating to AICAR. Actinomycin D and cycloheximide were used to assess the effect of AICAR on the stability of cMyc mR-NA and protein. Western blot was used to examine the regulatory effect of AICAR on c-Myc in various cancer cell lines. The MTT assay was used to determine the effect of AICAR on cell viability in these cell lines. Results AICAR significantly up-regulated c-Myc at both mRNA and protein levels. The protein level of c-Myc reached a plateau 12 h after the AICAR treatment. The up-regulatory effect of c-Myc induced by AICAR was not dependent on either the AMPK signaling pathway or the downstream metabolites of AICAR. AICAR could significantly enhance the mRNA stability of c-Myc but did not affect the protein stability. The up-regulation of c-Myc induced by AICAR was cell-type specific. AICAR up-regulated c-Myc in SW1990, 786-0, and A549, while down-regulated c-Myc in HepG2, MCF7, and U20S. In HepG2 cells, AICAR treatment decreased cell viability. However, in SW1990 and A549 cells, AICAR treatment did not lead to any significant difference in cell viability. AICAR decreased the cell viability only when c-Myc was knocked down in SW1990 and A549 cells. Conclusions AICAR directly up-regulates c-Myc expression in an AMPK-independent manner. The up-regulation effect is cell-type dependent. The regulation of c-Myc expression by AICAR is linked to the inhibitory effect of AICAR on tumor cell proliferation.