DOES THE GERMLINE DEfiCIENCY IN TOLL-LIKE RECEPTOR (TLR)2 AFFECT THE 4-NITROQUINOLONE N-OXIDE (4-NQO)-INDUCED CARCINOGENESIS IN THE UPPER AERODIGESTIVE TRACT?

TLR2 is implicated in the development and/or progression of several cancer types. We showed recently that activated TLR2 in human TLR2-high oral squamous carcinoma cells (OSCC) directly promote their growth and survival via the extracellular regulated kinases (ERK)1/2 signaling, among other functions (Palani et al, Oncotarget 2018;9:6814-29). However, most of the mechanisms of TLR2 function in squamous carcinogenesis remain unknown. Objectives & Approach To develop protocols and cell lines for targeted studies of squamous carcinogenesis in upper aerodigestive tract (UADT), we used an established (Protocol #1) and a modified (Protocol #2) 4-NQO carcinogenesis models in wild-type, TLR2-/- and TLR4-/- mice. Protocol #1 included carcinogen alone x 10 weeks, followed by 10% ethanol for 26 wks total. Protocol #2 included carcinogen and 5% ethanol x 19 weeks total. The study was approved by AU IACUC. Results Both protocols produced epithelial dysplasia and SCC in the oral and esophageal mucosae. In Protocol #1, fewer SCC developed in the absence of TLR2 than in the WT hosts (p=0.03). In contrast, Protocol #2 produced somewhat fewer SCC in WT hosts than in either TLR2-/- or TLR4-/- hosts (difference not significant). Moreover, there was marked intraepithelial exocytosis of leukocytes throughout the UADT in Protocol #2, irrespective of TLR expression. This contrasted with minimal exocytosis induced by Protocol #1. The characterization of the mucosal inflammation is ongoing. In addition, two OSCC cell lines were established for use in orthotopic models. Conclusions 1) The two protocols induced UADT SCC, but differed in the levels of mucosal inflammation. 2) TLR2 may have contributed to carcinogenesis in Protocol #1, but not in Protocol #2. 3) The specific roles of TLR in mucosal squamous carcinogenesis may depend upon additional factors, such as inflammation.