Abstract 3141: Toll-like receptor 4 knockout promotes cutaneous tumorigenesis in mice lack of Ikka heterozygous loss in keratinocytes

Abstract

Abstract Role of recognizing pathogen-associated molecular patterns in skin carcinogenesis has not been extensively studied. Toll-like receptor 4 (TLR4) recognizes gram-negative lipopolysaccharide. To explore the impact of interplay between TLR4-regulated microbiota and host epithelial cells on tumorigenesis, we adopted a mouse model that expresses hemizygous Ikkα gene induced by a keratin 5 Cre (K5.Cre, IkkααKC/+). IkkααKC mice die within 3 weeks after birth. Inducible Ikkα ablation mediated by K15.CrePR1 or K5.CreER results in spontaneous skin tumors. We found an increased incidence of spontaneous skin tumors in Tlr4-/-;IkkααKC/+ mice compared to Tlr4-/- or IkkααKC/+ mice. We detected markedly elevated bacteria numbers on the surface of skin tumors compared to the adjacent skin. Interestingly, the oral cavity of Tlr4-/-;IkkααKC/+ mice showed an elevated proportion of gram-negative bacteria compared to Tlr4-/- or IkkααKC/+ mice. To further determine the effect of bone marrow (BM)-derived hemopoietic cells on tumorigenesis, we performed BM transplant experiments. IkkααKC/+ mice with Tlr4-/- BM developed more cutaneous skin tumors than IkkααKC/+ mice with WT BM. Based on these findings, we hypothesized that Tlr4-/- hemopoietic cells regulate microbiota, which further results in altered skin carcinogenesis. We are revealing the detailed mechanism of how Tlr4-/- hemopoietic cells contribute to microbiota changes and tumorigenic promotion. Citation Format: Amit Kumar Singh. Toll-like receptor 4 knockout promotes cutaneous tumorigenesis in mice lack of Ikka heterozygous loss in keratinocytes [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 3141.