Genetic status of KRAS modulates the role of Neuropilin-1 in tumorigenesis.

Neuropilin-1 (NRP1), a non-tyrosine kinase receptor, is overexpressed in many cancers including pancreatic and lung cancers. Inhibition of NRP1 expression, however, has differing pro-tumor vs. anti-tumor effects, depending on the cancer types. To understand the differential role of NRP1 in tumorigenesis process, we utilized cells from two different cancer types, pancreatic and lung, each containing either wild type KRAS (KRAS (wt)) or mutant KRAS (KRAS (mt)). Inhibition of NRP1 expression by shRNA in both pancreatic and lung cancer cells containing dominant active KRAS (mt) caused increased cell viability and tumor growth. On the contrary, inhibition of NRP1, in the tumor cells containing KRAS (wt) showed decreased tumor growth. Importantly, concurrent inhibition of KRAS (mt) and NRP1 in the tumor cells reverses the increased viability and leads to tumor inhibition. We found that NRP1 shRNA expressing KRAS (mt) tumor cells caused increased cell viability by decreasing SMAD2 phosphorylation. Our findings demonstrate that the effects of NRP1 knockdown in cancer cells are dependent on the genetic status of KRAS.