The article focuses on the effect of proinsulin C-peptide on the proliferation of human breast cancer MCF7 cells. It states that C-peptide can activate the glycolytic enzyme alpha-enolase and the alpfa-enolase gene ENO1 encodes c-Myc promoter-binding protein-1 (MBP1). The study reveals that C-peptide induces a cytostaic effect on human breast cancer MCF7 cells and also increases the expression of c-MYC protooncogene.