ABSTRACT
Previously we reported that Myd88 contributed to tumor progression. To begin to decipher what may be inducing Myd88 dependent signaling we focused on proteins that could function as damage associated molecular pattern molecules (DAMPs) since DAMPs have been reported to be secreted by tumors, and certain DAMPs mediate effects through toll-like receptors. A screen of mammary carcinoma for DAMP expression showed HMGB1 and HSP60 were significantly elevated relative to normal mammary epithelium, and targeting these DAMPs, or receptors for these DAMPs influenced growth of tumor cells. Moreover, analysis using a Myd88 inhibitory peptide suggested that HMGB1 mediated its effects in a Myd88 dependent manner, and inhibiting Myd88 function decreased HMGB1 and HSP60 gene expression. Collectively, these data suggest that HMGB1 and HSP60 contribute to growth of mammary carcinoma cells, HMGB1 accomplishes this, at least in part, through Myd88 dependent signaling, and these DAMPs are expressed in a Myd88 dependent manner.
Subject(s)
Cell Proliferation , Chaperonin 60/genetics , HMGB1 Protein/genetics , Myeloid Differentiation Factor 88/genetics , Animals , Antibodies, Neutralizing/immunology , Antibodies, Neutralizing/pharmacology , Apoptosis/drug effects , Apoptosis/genetics , Blotting, Western , Cell Cycle/drug effects , Cell Cycle/genetics , Cell Line, Tumor , Chaperonin 60/immunology , Chaperonin 60/metabolism , Chemokine CCL2/genetics , Chemokine CCL2/metabolism , Gene Expression Regulation, Neoplastic/drug effects , HMGB1 Protein/immunology , HMGB1 Protein/metabolism , Mammary Neoplasms, Animal/genetics , Mammary Neoplasms, Animal/metabolism , Mammary Neoplasms, Animal/pathology , Matrix Metalloproteinase 9/genetics , Matrix Metalloproteinase 9/metabolism , Mice , Myeloid Differentiation Factor 88/antagonists & inhibitors , Myeloid Differentiation Factor 88/metabolism , Peptides/pharmacology , RNA Interference , Receptor for Advanced Glycation End Products , Receptors, Immunologic/genetics , Receptors, Immunologic/immunology , Receptors, Immunologic/metabolism , Reverse Transcriptase Polymerase Chain Reaction , Toll-Like Receptor 2/genetics , Toll-Like Receptor 2/immunology , Toll-Like Receptor 2/metabolism , Toll-Like Receptor 4/genetics , Toll-Like Receptor 4/immunology , Toll-Like Receptor 4/metabolismABSTRACT
Previously we reported that lipopolysaccharide (LPS) treatment of murine mammary carcinomas resulted in decreased growth of the tumors. Here we show the decreased growth following LPS treatment was mediated through effects downstream of TLR4 and Myd88. Perhaps more notably, simply reducing TLR4 or Myd88 levels was sufficient to slow tumor growth rates. Moreover, reduced levels of Myd88 correlated with a significant reduction in lung metastasis as well as decreased CCL2 and CCL5 expression. To determine whether inhibiting Myd88 function could also alter tumor growth and chemokine expression we used a Myd88 homodimerization inhibitory peptide. Indeed, inhibiting Myd88 function in four different murine mammary carcinomas as well as the human breast cancer cell line MDA-MB-231 led to decreased growth as well as CCL2 and CCL5 expression. These data imply that Myd88 is important for growth and metastasis of breast cancer, and expression of at least two proinflammatory chemokines.