Inhibition of Notch is Directly Correlated with VPAC Repression in HT‐29 Colon Carcinoma Cells

Abstract

In 2005, 72,007 men and 69,398 women were diagnosed with colon cancer in the United States alone. Although the cause of cancer is not well defined, colon cancer can arise from upregulation of the Notch signaling pathway, which enhances intestinal stem cell and progenitor cell proliferation. A vital step in activating Notch signaling is its cleavage by gamma‐secretase. It has been shown that vasoactive intestinal peptide receptor 1 (VPAC1), a pro‐proliferative receptor in solid‐tumors like colon cancer, contains multiple putative binding sites for Notch in the gene locus. However, the effect of Notch on VPAC1 signaling is not yet determined. We hypothesized that Notch would activate VPAC1 expression. The gamma‐secretase inhibitor N‐[N‐(3,5‐difluorophenacetyl)‐L‐alanyl]‐S‐phenylglycinet‐butyl ester (DAPT) was added to cultures of HT‐29 colon cancer cells, followed by determination of VPAC1 steady state mRNA levels measured after 24 hours via SYBR green qPCR. The data showed a decrease in VPAC1 due to the addition of DAPT, supporting the idea that Notch is a transcriptional activator of VPAC1 expression in HT‐29 cells. These results positively impact human health by guiding the development for new colon cancer therapies directed at inhibiting VPAC1 signaling. Funding: NIH‐K011K01DK064828 & COBRE 2P20RR05566.