Abstract 1611: Transcriptome analyses of the tumor cell line resistant to anti-VEGF therapy.

Abstract

Abstract Despite overt clinical success of anti-VEGF (vascular endothelial growth factor) agents, such as Avastin, for cancer patients, increasing evidence shows that prolonged treatment of anti-VEGF therapy results in tumor resistance. In order to understand how tumor cells become resistant to anti-VEGF therapy, we developed a mouse Lewis lung carcinoma (LLC) cell line, which was resistant to a potent VEGF blocker, VEGF-Trap. The cell line was established through five rounds of VEGF-Trap treatment and selection in vivo. In each round, C57BL/6 mice were inoculated with LLC cells and subjected to VEGF-Trap or PBS treatment. Tumors grown from treated mice were harvested and the isolated cells were injected to a new batch of mice for the next round of treatment. It was found that tumor cells became insensitive to VEGF-Trap in vivo after five rounds of VEGF-Trap treatment, i.e., VEGF-Trap no longer inhibited tumor growth. In contrast, VEGF-Trap remained efficacious to the LLC cells which underwent five passages in mice but treated with PBS. The resistance phenotype was maintained in LLC cells after the tumor cells were expanded for a number of passages in vitro, indicating that the resistance was due to inherited alterations in tumor cells. To gain insights into the molecular mechanism underlying the resistance to anti-VEGF therapy, we compared transcriptome profiles of the resistant and non-resistant tumor cells using mRNA-seq. The next generation sequencing reads were aligned to mouse genome; gene transcripts were assembled and calculated for relative abundance for individual gene. Results showed that 644 genes were differentially expressed with statistically significances, 317 up-regulated and 327 down-regulated in the resistant tumor cells. Interestingly, VEGF-C was significantly up-regulated in the resistant tumor cells (fold change = 4.91), which was further verified by real-time PCR analysis. Given the stimulatory effects of VEGF-C on both angiogenesis and lymphatic angiogenesis, it is possible that VEGF-C over-expression plays a role in the development of LLC tumor resistance to anti-VEGF therapy. Citation Format: Dong Li, Kun Xie, Guitao Ding, Hongwen Li, Xuejing Yao, Cizhong Jiang, Jianmin Fang. Transcriptome analyses of the tumor cell line resistant to anti-VEGF therapy. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 1611. doi:10.1158/1538-7445.AM2013-1611