LPS-Induced TLR4 Signaling in Human Colorectal Cancer Cells Increases β1 Integrin-Mediated Cell Adhesion and Liver Metastasis

Abstract

Infectious complications resulting from resection of colorectal cancer (CRC) elevates the risk of cancer recurrence and metastasis, but the reason for this risk relationship is unknown. Defining the mechanisms responsible may offer opportunities to improve outcomes in a majority of patients whose tumors are resected as part of their therapy. The complex formed between Toll receptor TLR4 and myeloid differentiation factor MD2 defines a major cell surface receptor for lipopolysaccharide (LPS), a gram-negative bacterial antigen that has been implicated in infectious complications after CRC resection. As the TLR4/MD2 complex is expressed on CRC cells, we hypothesized that LPS may promote liver metastasis in CRC by stimulating TLR4 signaling. In support of this hypothesis, we report here that LPS enhances liver metastasis of human CRC cells that express TLR4/MD2 after intrasplenic graft of immunocompromised nude mice. Compared with TLR4 nonexpressing, nonmetastatic CRC cells, we observed increased in vitro adherence to different extracellular matrices and human umbilical vein endothelial cells (HUVEC). Furthermore, we observed an increased likelihood of in vivo capture within hepatic sinusoids after LPS treatment. No differences were apparent in phosphorylation of p38 and MAPK isoforms, but in metastatic CRC cells expressing surface TLR4 treatment with LPS increased Ser473 phosphorylation of AKT kinase. We showed that enhanced adherence elicited by LPS in these cells could be blocked at three different levels, using Eritoran (TLR4 small molecule antagonist), PI-103 (PI3K inhibitor), or anti-b1 integrin blocking antibodies. Taken together, the results indicate that stimulation of the TLR4/MD2 complex by LPS activates PI3K/AKT signaling and promotes downstream b1 integrin function, thereby increasing the adhesiveness and metastatic capacity of CRC cells. Our findings suggest that inhibiting LPS-induced TLR4 signaling could improve therapeutic outcomes by preventing cancer metastasis during the perioperative period of CRC resection. Cancer Res; 71(5); 1989-98. Ó2011 AACR.

STIM1/ORAI1-mediated Ca2+ Influx Regulates Enolase-1 Exteriorization

“…LPS was shown to increase the invasion of hepatic cancer cells in mice (23) and to potentiate lung metastasis upon intravenous injection of mouse mammary carcinoma cells into animals (24). LPS may contribute to tumor progression by activation of TLR-4 signaling pathway in cancer cells (25) and by the recruitment of inflammatory cells into the tumor microenvironment (26). LPS-induced migration and invasion of inflammatory cells is accompanied by increased production and release of proinflammatory cytokines (27), which display protumorigenic activities (26,28).…”

LPS-induced CXCR4-dependent migratory properties and a mesenchymal-like phenotype of colorectal cancer cells

“…35 Previous study has shown that LPS could increase b1 integrin-mediated cell adhesion and liver metastasis, which was an important marker of EMT. 13 In this study, we treated the colon cancer cells with LPS in vitro to observe the occurrence of EMT, with encouraging results. Stimulation by LPS caused E-cadherin (the epithelial marker) to disappear, Vimentin and Snail (the mesenchymal marker) to increase.…”

“…[9][10][11][12] And it could significantly augment the cell adhesion and liver metastasis of human CRC cells. 13,14 Recently, several studies have placed chemokines and their receptors at the center of not only physiological cell migration, but also pathological processes, such as metastasis in cancer. 15 Stromal cell-derived factor 1a (SDF1a)/CXCR4 axis is one of the few chemotactic systems that characterizes one-to-one correspondence reciprocally between the ligand and receptor.…”

Spillage of bacterial products during colon surgery increases the risk of liver metastases development in a rat colon carcinoma model.

“…It has been demonstrated that injection of endotoxin in an experimental model enhanced colon carcinoma cell adhesion in the liver. 51, 52 Importantly, a recent study demonstrated that bowel mobilization already led to bacterial translocation in patients. 40 Furthermore, patients with anastomotic leakage or who encountered bacterial translocation after a colectomy had poor disease-free survival, 41 indicating that bacterial contamination had a negative impact on long-term patient outcome.…”