Tumor resistance to anti-VEGF therapy through up-regulation of VEGF-C expression.

Increasing evidence has indicated that prolonged use of anti-VEGF (vascular endothelial growth factor) agents for cancer therapy promotes tumor resistance. To gain insight into the molecular mechanism underlying resistance to anti-VEGF therapy, we developed a mouse Lewis lung carcinoma (LLC) cell line that is resistant to treatment with a potent VEGF inhibitor, VEGF-Trap, through repeated in vivo selection. We compared the transcriptome profiles of resistant and non-resistant tumor cells using RNA-seq analysis. VEGF-C was significantly up-regulated in resistant tumor cells, as determined by quantitative real-time PCR and immunohistochemical analyses. Inhibition of VEGF-C in resistant cells suppressed endothelial cell migration in vitro and partially restored sensitivity to VEGF-Trap treatment in vivo. Our findings indicate that tumors may develop resistance to anti-VEGF therapy by activating the VEGF-C pathway.