Knockdown of Ron Kinase Inhibits Mutant Phosphatidylinositol 3-Kinase and Reduces Metastasis in Human Colon Carcinoma

Abstract

Abnormal accumulation and activation of receptor tyrosine kinase Ron (recepteur d'origine nantais) has been demonstrated in a variety of primary human cancers. We show that RNA interference-mediated knockdown of Ron kinase in a highly tumorigenic colon cancer cell line led to reduced proliferation as compared with the control cells. Decreased Ron expression sensitized HCT116 cells to growth factor deprivation stress-induced apoptosis as reflected by increased DNA fragmentation and caspase 3 activation. In addition, cell motility was decreased in Ron knockdown cells as measured by wound healing assays and transwell assays. HCT116 cells are heterozygous for gain of function mutant PIK3CA H1047R. Analysis of signaling proteins that are affected by Ron knockdown revealed that phosphatidylinositol 3-kinase (PI3K) activity of the mutant PI3K as well as AKT phosphorylation was substantially reduced in the Ron knockdown cells compared with the control cells. Moreover, we demonstrated in vivo that knockdown of Ron expression significantly reduced lung metastasis as compared with the control cells in the orthotopic models. In summary, our results demonstrate that Ron plays an essential role in maintaining malignant phenotypes of colon cancer cells through regulating mutant PI3K activity. Therefore, targeting Ron kinase could be a potential strategy for colon cancer treatment, especially in patients bearing gain of function mutant PI3K activity.The receptor tyrosine kinase Ron (recepteur d'origine nantais) belongs to the Met proto-oncogene family (1, 2). Mature Ron is a 180-kDa heterodimer composed of a 40-kDa extracellular ␣-chain and a 150-kDa transmembrane ␤-chain with tyrosine kinase activity (2). Macrophage-stimulating protein is the only ligand that has been identified for Ron (3, 4). Upon ligand binding, Ron dimerizes, becomes autophosphorylated, and transduces a variety of signals that regulate different downstream pathways including Ras/mitogen-activated protein kinase (MAPK), phosphatidylinositol 3-kinase (PI3K), 3 c-Jun N-terminal kinase (JNK), ␤-catenin, and nuclear factor-B (5-12). Ron can be activated through ligand-dependent or -independent mechanisms (3,13,14), which lead to responses important for tumorigenesis and metastasis, including cell scattering, proliferation, motility, and survival (15,16).Ron is normally expressed at relatively low levels in cells of epithelial origin (4). Recent studies have shown that Ron is overexpressed in 47% of breast tumor tissues as compared with benign epithelium and that elevated Ron expression was strongly associated with invasive activity by tumors (17). In addition, Ron is moderately expressed in normal colorectal mucosa, but is significantly increased in the majority of primary human colorectal adenocarcinoma samples (18). Ron overexpression has also been demonstrated in head and neck tumors (19). Furthermore, splice variants of Ron have been identified in human colon cancer. These variants were found to confer constitutive Ron activity, transformation, and tumorige...

Synergistic Activities of MET/RON Inhibitor BMS-777607 and mTOR Inhibitor AZD8055 to Polyploid Cells Derived from Pancreatic Cancer and Cancer Stem Cells

“…Inhibition of RON has implicated its signaling for PDAC cell growth and survival in preclinical studies (2)(3)(4)(5)(6)10). Various studies have shown that therapeutic antibodies and TKIs specific to RON inhibit tumor growth mediated by pancreatic, colon, and breast cancer cells in mouse tumor xenograft models (7,12,13,31).…”

“…Previous studies have shown that RON is overexpressed and activated in primary PDAC samples and established cell lines (1)(2)(3)(4)(5)(6). Here, we determined the therapeutic effect of BMS-777607 on RON signaling in L3.6pl cells and CSCs þ24/44/ESA .…”

“…Overexpression of the recepteur d'origine nantais (RON) receptor tyrosine kinase (RTK) in cancer cells has been implicated in tumorigenic activities and malignant progression (1)(2)(3)(4). Aberrant RON expression also has been molecularly targeted in mouse xenograph models of pancreatic ductal adenocarcinoma (PDAC; refs.…”

RON - The Con in Colorectal Carcinoma

“…Mutations in PIK3CA which encodes the p110α catalytic subunit of PI3K are observed in a large number of CRC patients and HCT116 which has H1076R gain of function mutation. It was observed that knockdown of RON kinases inhibits the activation of mutant PI3K and thereby the metastatic potential of orthotropically injected colon cancer cells [24]. RON siRNA inhibited signaling by β-catenin suggesting the regulation of this pathway by RON kinase [49,50].…”

“…Studies from our own laboratory and others have shown that RON contributes to the malignant and invasive phenotype of CRC [24]. RON has been shown to regulate several key processes in colon tumor progression and also plays active role in EMT which is analogous its role in embryonic development [25].…”