Abstract 2673: Divergent therapeutic responses to CD40L blockade or CD40 activation in Ras-driven skin cancers determined by origin of tumor initiating cell
Authors: Glick Adam B. , Bailey Jacob T. , Gunderson Andrew , Breech Kyle , Podolsky Michael 
Published: July 2017

Abstract
Heterogeneity in tumor immune responses is a poorly understood yet critical parameter for successful immunotherapy. We used doxycycline-inducible epidermal squamous cancer models driven by oncogenic Ras to test whether the origin of the tumor-initiating cell influenced the tumor immune response. Threshold doxycycline induced expression of H-RasG12V in either the basal/stem cell layer with a Keratin14-rtTA transgene (K14Ras), or committed progenitor/suprabasal cells with an Involucrin-tTA transgene (InvRas), caused distinct immune responses despite similar levels of Ras, tumor latency, and tumor numbers. End stage K14Ras tumors had an immunosuppressed microenvironment with abundant Tregs and Bregs which evolved from an initially Th1 dominant environment in the earliest detectable lesions. In contrast InvRas tumors had a Th2 pro-inflammatory microenvironment, with significantly fewer Tregs or Bregs at any time point. This difference in immune microenvironment between the tumor models was also found in hyperplastic skin after 5 days of maximal Ras expression, indicating that it was not simply a property of the end stage tumor. Surprisingly, adaptive immunity had opposite roles in tumor development. InvRasRag1-/- mice developed fewer and smaller tumors that regressed while K14RasRag1-/- mice developed more tumors with shorter latency than Rag1+/+ controls. In both models adoptive transfer and depletion studies showed that cooperation between B and CD4 T cells drove the opposing tumor responses, lymphocyte polarization, and tumor immune phenotype. Co-culture of tumor-conditioned but not splenic B cells from each model with naive CD4 T cells showed that direct contact and CD40-CD40L ligation was required for opposite polarization towards either a Th2 or Treg phenotype. Importantly, we found that anti-CD40L mAb caused regression of preexisting InvRas tumors but enhanced growth of K14Ras tumors. In contrast, CD40 agonist mAb enhanced growth of preexisting InvRas tumors, and suppressed growth of K14Ras tumors. Thus in an in vivo setting the type of tumor immune microenvironment and opposing role of CD40-CD40L in tumor development generates distinct responses to therapeutic antibodies. Together these data show that the position of a tumor initiating cell within the stem cell hierarchy in a stratified squamous epithelia has important consequences for the type of tumor immune microenvironment and response to checkpoint therapy.
Citation Format: Adam B. Glick, Jacob T. Bailey, Andrew Gunderson, Kyle Breech, Michael Podolsky. Divergent therapeutic responses to CD40L blockade or CD40 activation in Ras-driven skin cancers determined by origin of tumor initiating cell [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 2673. doi:10.1158/1538-7445.AM2017-2673