Abstract 530: Location of oncogene expression within a stratified squamous epithelium drives distinct B and CD4 T-cell crosstalk to dictate the tumor immune response

Tumors from stratified epithelium contain proliferating and differentiating compartments, but it is not clear how tumor cells in different layers alternatively engage the immune system. We have established two doxycycline inducible Ras models in which oncogenic RasV12G is targeted to either the epidermal basal/stem cell layer with a Keratin14-rtTA transgene (K14Ras), or suprabasal differentiating cells with an Involucrin-tTA transgene (InvRas). On threshold doxycycline levels yielding similar tumor numbers and Ras expression over 30 days, mice with basal cell targeted Ras developed focal squamous cell carcinoma while suprabasal targeting caused benign squamous papilloma formation. On a Rag1-/- background InvRas mice developed fewer tumors that regressed over time while K14Ras mice developed more tumors with shorter latency than Rag1+/+ controls. Depletion and adoptive transfer studies revealed that naive B and CD4 T cells together, but not alone, suppressed tumor formation in K14Ras mice but restored tumor numbers in InvRas mice. Tumors developing in K14Ras mice showed a loss of proinflammatory CD4 T and B cells and increased percentages of regulatory cells infiltrating the tumor tissue. In vivo cotransfers show that B and CD4 T cells reciprocally prime each other towards a regulatory phenotype in the K14Ras tumor microenvironment, but in the InvRas tumor microenvironment proinflammatory CD4 T and B cell phenotypes result. Coculture of tumor-conditioned B cells with stimulated naive CD4 T cells showed an importance of direct contact and CD40/CD40L interactions for the generation of regulatory T cells (Tregs) by B cells in K14Ras mice. In contrast, tumor-conditioned B cells from InvRas mice support generation of proinflammatory CD4 T cells, and antagonize Treg development. This function is restricted to tumor-conditioned B cells, as splenic B cells from tumor-bearing mice had no effect on CD4 T cell phenotype. In vivo blockade of CD40L in K14Ras mice resulted in significantly increased tumor counts as well as reduced B and Treg prevalence. Blockade of CD40L in InvRas mice significantly reduced tumor number, increasing Treg cell count and decreasing neutrophil infiltration into the tumor tissue. Time-course experiments suggest a protective role of Tregs in late stages of K14Ras tumors, and a tumor-promoting role of proinflammatory CD4 T cells in InvRas tumors. Thus, basal/stem cell expression of Ras provokes a regulatory cell inducing microenvironment, suppressing tumor-promoting inflammation in late-stage tumors. Ras expression in differentiating cells activates a tumor promoting proinflammatory phenotype in B and CD4 T cells without provoking immunosurveillance. Taken together, these data show that tumor cell position within a stratified epithelium differentiation hierarchy provokes distinct B and CD4 T cell interactions with opposing effects on tumor development. Citation Format: Michael A. Podolsky, Carrie J. Oakes, Andrew Gunderson, Kyle Breech, Jacob Bailey, Adam B. Glick. Location of oncogene expression within a stratified squamous epithelium drives distinct B and CD4 T-cell crosstalk to dictate the tumor immune response. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 530.