A role for HMGB1, HSP60 and Myd88 in growth of murine mammary carcinoma in vitro

• This is the first report HMGB1 and HSP60 are expressed in a Myd88 dependent manner.
• The manuscript shows mammary carcinoma overexpress HMGB1 and HSP60.
• The manuscript shows HMGB1 and HSP60 expression influences tumor cell growth.
• Results contribute to a better understanding of DAMPs and PAMPs in a tumor setting.

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.