Abstract 4052: Location of oncogene expression within a stratified squamous epithelium drives distinct B and CD4 T cell crosstalk to dictate the tumor immune response
Authors: Podolsky Michael A. , Oakes Carrie J. , Gunderson Andrew , Breech Kyle , Glick Adam B. 
Published: August 2015

Abstract
Tumors from stratified epithelium contain both proliferating and differentiating compartments, but it is not clear if tumor cells in different layers engage the immune system in a similar fashion. 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). As expected, on threshold doxycycline levels yielding similar numbers of tumors over 30 days and similar Ras expression, mice with basal cell targeted Ras developed focal squamous cell carcinoma while suprabasal targeting caused benign squamous papilloma formation. However, 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 naïve 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 progressive loss of proinflammatory CD4 T cells 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, while in the InvRas tumor microenvironment there was reciprocal priming of proinflammatory CD4 T and B cell phenotypes. Coculture of tumor-conditioned B cells with stimulated naïve CD4 T cells showed an importance of direct contact for the generation of regulatory T cells by B cells. Surprisingly, tumor conditioned InvRas splenocytes transferred into K14RasRag1-/- mice prior to Ras induction slightly enhanced tumor numbers while tumor conditioned K14Ras splenocytes blocked tumor formation in InvRasRag1-/- mice. Thus, basal/stem cell expression of Ras provokes a regulatory cell inducing microenvironment, which suppresses 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, 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 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 4052. doi:10.1158/1538-7445.AM2015-4052