miR-124, miR-137 and miR-340 regulate colorectal cancer growth via inhibition of the Warburg effect.

Colorectal cancer represents one of the most challenging diseases. Increasing evidence indicates that aberrant expression of microRNAs (miRNAs) is related to pathogenesis of colorectal cancer. Cancer cells reprogram metabolic pathways to sustain higher proliferation rates. Whether mechanisms underlying the role of miRNA in colorectal cancer are involved in metabolic reprogramming and the mechanisms through which miRNAs alter cancer metabolism are as yet unknown. Herein, we show that miR-124, miR-137 and miR-340 are associated with poor prognosis of colorectal cancer. Expression of these miRNAs inhibits the growth of colorectal cancer cells. PKM (pyruvate kinase isozyme) alternative splicing proteins (PTB1/hnRNAPA1/hnRNAPA2), which control the inclusion of exon 9 (PKM1) or exon 10 (PKM2), are targeted by miR-124, miR-137 and miR-340. Consequently, miR-124, miR-137 and miR-340 switch PKM gene expression from PKM2 to PKM1. High ratios of PKM1/PKM2 inhibit the glycolysis rate, but elevate the glucose flux into oxidative phosphorylation. These results demonstrate that miRNAs (miR-124, miR-137 and miR-340) impair colorectal cancer growth by counteracting the Warburg effect due to regulating alternative splicing of the PKM gene.