Chemoresistant Colorectal Cancer (CRC) Cells Show Increased Invasive Potential Which Is Part Is Mediated By VEGF-Signaling and Can be Attenuated By VEGF-Directed Agents

Introduction. Cancer mortality is principally associated with the presence of drug-resistant, invasive subpopulations of tumor cells. However, the functional and mechanistic interactions between the two phenotypes are incompletely understood. Colorectal cancer (CRC) cells produce the vast majority of VEGF in the cancer environment and display endogenous VEGFR1/VEGF signaling which is believed to promoted survival under stress.

Methods. Migration and invasion was determined by the transwell assay (Boyden Chamber). For the tube formation assay, CRC cells were seeded onto 3D matrigels and incubated at 37° for 24 hr monitored by videomicroscopy. Determination of VEGF ligands was carried out by ELISA.

Results. We here characterize a panel of 4 isogenic CRC cell lines comprised of the parental HCT-116 cells and three independently derived sublines resistant to 5-fluorouracil, oxaliplatin and SN-38. Resistant cells secreted 3-7 fold more VEGF, while the HCT-116/5-FU cells also secreted 2 times more PlGF, compared to the parental cells. VEGF signaling is known to promote CRC cell migration and invasion. In agreement, resistant cells showed 6-11 fold increased migration, whereas the invasive capacity had increased 6-15 fold. Aflibercept inhibits all three VEGFR1 ligands (VEGF-A, VEGF-B and PlGF) on CRC cells accordingly, addition of aflibercept resulted in a significant decrease in both migration and invasion. Two of the three resistant cell lines were able to do vascular/vasculogenic mimicry by forming capillary-like cellular networks which could be significantly attenuated by aflibercept.

Conclusions.Taken together, our results indicate that acquired resistance to genotoxic agents may be accompanied by an increased invasive potential mediated, in part, by VEGF signaling that can be attenuated by aflibercept.