Western blot analysis revealed that KR treatment of MCF7 and MDA-MB-231 cancer cell lines increased HIF-1α accumulation and autophagy compared to the control, while the mTOR inhibitor rapamycin dramatically attenuated DPP-4 deficiency-induced HIF-1α accumulation and autophagic activation, evaluated by LC3II/I ratio and p62 levels (Figure 3A). This evidence concerns the gene DPP4 and cancer.