Significance of integrin αvβ5 and erbB3 in enhanced cell migration and liver metastasis of colon carcinomas stimulated by hepatocyte‐derived heregulin

Abstract

To study the mechanisms of the highly liver-metastatic character of colon carcinoma cells, we studied the expression pattern of surface integrins on LS-LM6 (a highly liver-metastatic human colon cancer cell line) and the effects of hepatocyte-derived soluble factors on cell migration. LS-LM6 showed significantly higher expression of integrin avb5, a ligand for vitronectin (VN), as compared with its parental cell line (LS174T). A conditioned medium of cultured mouse hepatocytes enhanced VN-mediated cell migration of LS-LM6, which was blocked by neutralizing antibody against integrin avb5, while the medium did not affect cell adhesion to VN-coated plastic surfaces. The conditioned medium induced phosphorylation of erbB3 and its heterodimeric partner, erbB2. Heregulin (HRG), a ligand for erbB3, exerted similar effects on VN-mediated cell migration and phosphorylation of erbB3 and erbB2. The conditioned medium contained HRG, and depletion of HRG from the medium by pre-absorption with HRG antibody abolished its effects on cell migration. Heregulin (HRG) was expressed in some hepatocytes in the liver with carcinoma cell metastasis. Furthermore, knockdown of integrin av and erbB3 by smallinterfering RNAs significantly inhibited cell migration induced by HRG as well as liver metastasis in vivo. Finally, we found that HRGinduced cell migration was associated with marked phosphorylation of Akt and that cell migration was suppressed by treatment with specific inhibitors of phosphatidylinositol 3-kinase. Our study suggests that hepatocyte-derived HRG might participate in a highly liver-metastatic phenotype of LS-LM6 through enhancement of integrin avb5-mediated cell migration and erbB3 ⁄ erbB2 signaling. (Cancer Sci 2010; 101: 2011-2018 T he liver is one of the major target organs for tumor metastasis, including colorectal carcinomas. Since liver metastasis is an important prognostic factor for patients suffering from colorectal carcinoma, understanding of the molecular mechanisms underlying the metastatic process is important. To elucidate the mechanisms of organ-preferential metastasis, it should be important to consider complex interactions between tumor cells and the target organ's microenvironment, which consists of the extracellular matrix (ECM), cytokines, and growth factors derived from the resident cells.(1,2) It has been reported that cell adhesion and invasion (migration) play important roles in the development of liver metastasis of colorectal carcinoma cells in addition to angiogenesis and cell survival.(3) At the initial stage of metastasis, tumor cells need to adhere to the luminal surface of hepatic sinusoidal endothelial cells via various cell adhesion molecules, such as E-selectin, vascular cell adhesion molecule 1 (VCAM-1), and intercellular adhesion molecule 1 (ICAM-1) expressed on endothelial cell surfaces.(4-8) At the next stage of metastasis, the interaction between ECM in the space of Disse and integrins, which are expressed on tumor cell surfaces, is required for invasion and migration of tumor cell...

Isthmin targets cell-surface GRP78 and triggers apoptosis via induction of mitochondrial dysfunction

“…Notably, LS-LM6, a highly metastatic derivative of LS174T, expresses high-level cell-surface GRP78 and is susceptible to ISM-induced apoptosis (Supplementary Figure S4). 24 Overexpression of ISM's low-affinity receptor avb5 integrin also increased the sensitivity of LS174T cells to ISM-induced apoptosis (Supplementary Figure S5a). ISM is known to interact with avb5 integrin and trigger cell death through integrin-mediated activation of caspase-8.…”

“…It is noted that LS-LM6 cells also express a higher level of avb5 integrin, the low-affinity receptor of ISM. 24 ISM-avb5 integrin interaction may also contribute to its high sensitivity to ISM-induced apoptosis.…”

“…41 LS174T and LS-LM6 cells were cultured as described. 24 HEK293T, B16F10, 4T1, 786-O, NIH3T3 and SWISS3T3 cells were purchased from ATCC (Manassas, VA, USA) and cultured in DMEM with 10% FBS (SigmaAldrich, St. Louis, MO, USA). GFP and mouse ISM cDNA were cloned into pSecTag2B vector (Invitrogen, Carlsbad, CA, USA).…”

Imaging of HER3-expressing xenografts in mice using a 99mTc(CO)3-HEHEHE-ZHER3:08699 affibody molecule

“…Cells with documented expression of HER3, a colorectal carcinoma LS174T [32], and breast cancer BT474 [33] and MCF-7 [34] cell lines, were used to study specificity of 99m Tc(CO) 3 -HEHEHE-Z 08699 for binding in vitro. All cell lines were from American Type Tissue Culture Collection.…”

Identification of genes potentially involved in bone metastasis by genome-wide gene expression profile analysis of non-small cell lung cancer in mice

“…A latest report shows that small-molecule compounds that selectively target the hemopexin domain of MMP-9 can control tumor growth and inhibit lung metastasis in breast cancer xenograft model in mice (45). Moreover, VTN, an extracellular protein that interacts with many integrins, is also expressed highly in the liver, and was previously reported to be upregulated in primary hepatocellular carcinoma (46), or liver metastases from colorectal cancer (46,47) and neuroblastoma (48).…”