129 - The Role of Stressors on the Expression and Function of Porcupine and Wntless in Human Colorectal Carcinoma Cells

Abstract

Gastric cancer is the third most common cancer and the fourth most common cause of death due to cancer worldwide. There is a large potential for reducing the burden of this disease by early detection. We examined the protein factors involved in the early stages of gastric cancer development; Porcupine (Porc), Wntless (Wls) and Wnt. The Wnt proteins have important functions in stem cell biology, cardiac development and differentiation, angiogenesis, cardiac hypertrophy, cardiac failure, cancer, and aging. This study aimed to understand how modifications Porc and Wls control Wnt secretion from cells under physiological and chemical stresses (hypoxia, oxidative stress and endoplasmic reticulum (ER) stress (or the unfolded protein response)). Porc glycosylates and palmitoylates Wnt proteins in the ER, while Wntless transfers the modified Wnts from the Golgi to secretory vesicles for extracellular secretion. We found that both porc and wls mRNA expressions were significantly increased with antimycin A treatment and proteasome inhibition in Human Colon Cancer (HCT116) cells. Treatment with ER stressors (thapsigargin, tunicamycin, dithiolthreitol) significantly increased porc expression. With the exception of tunicamycin, the same treatments significantly increased wls expression. Porc and Wls protein expression increased with ER stressor and hypoxic mimetic treatment in both HCT116 and Human Embryonic Kidney (HEK293T) cells. From immunoblotting results, HIF was found to potentially play a role in porc and wls expression. We hypothesize that these stressors can alter Porc and Wls expression and function, leading to altered Wnt secretion and the development of gastric cancer.