PTHrP increases xenograft growth and promotes integrin α6β4 expression and Akt activation in colon cancer

Parathyroid hormone-related protein (PTHrP) is expressed by human colon cancer tissue and cell lines. Expression of PTHrP and phosphatidylinositol 3-kinase (PI3-K) pathway components correlates with the severity of colon carcinoma. Here we observed a positive effect of endogenous PTHrP on LoVo (human colon cancer) cell proliferation, migration, invasion, integrin α6 and β4 expression, and p-Akt levels. There was a direct correlation between PTHrP expression and anchorage-independent cell growth. PTHrP significantly increased xenograft growth; tumors from PTHrP-overexpressing cells showed increased expression of integrins α6 and β4, and PI3-K pathway components. The higher expression of PTHrP in human colon cancer adenocarcinoma vs. normal colonic mucosa was accompanied by increased integrin α6 and β4 levels. Elevated PTHrP expression in colon cancer may thus upregulate integrin α6β4 expression, with consequent PI3-K activation. Targeting PTHrP might result in effective inhibition of tumor growth, migration, and invasion.