Identification of differentially expressed genes associated with clinical response after treatment of breast cancer skin metastases with imiquimod.

Abstract

e12541 Background: Imiquimod, a Toll-like receptor 7 agonist, activates innate immunity and has a response rate of 20% in breast cancer skin metastases. Tumor regression is associated with increased tumor infiltrating lymphocytes and increased Th1 cytokines in tumor supernatant, however gene expression changes are unknown. This is the first report of gene expression changes induced by imiquimod treatment in breast cancer skin metastases. Methods: FFPE-extracted mRNA from 8 patients pre and post 8 weeks of imiquimod treatment was analyzed using Nanostring PanCancer Immune Profiling Panel. Gene expression and pathway analysis was conducted with nSolver 3.0 with clinical response as outcome, controlling for HER2 ER/PR status, with 5% significance level used. Results: In all patients, imiquimod was associated with upregulation of genes in innate immunity such as TLR7, IL-1, T-cell, B-cell, and NK related genes. Three patients had a clinical response after imiquimod. Forty-two differentially expressed genes were identified in responders vs. non-responders after imiquimod. Reponders had up-regulation of T cell (CD2, SPN), NK cell (KLRC2), B cell (CD48), lymphocyte (LY96), and IL-2 (IL2RG) related genes. The top upregulated pathways were cytotoxicity, NK cell function, and antigen processing. Pre-treatment, the responders had upregulation of TNF and IL-17 related genes (TNFRSF10B, IL17RA) compared to non-responders. Comparing pre-treatment to post-treatment, Imiquimod was associated with mRNA expression changes in 72 genes in responders vs non responders. The top upregulated genes involved activation of lymphocytes (SH2D1A), NK cells (KLRC2), DCs (CLEC4C), several chemokines, IL7R and immune regulators PLD1 and IRF5. Conclusions: Clinical response to Imiquimod treatment of breast cancer skin metastases is associated with upregulation of genes in innate immunity suggestive of an anti-tumor immune response. Inhibition of negative feedback by addition of PLD1 inhibitors may enhance treatment response. Understanding the genetic signature of imiquimod can enhance prediction of response and inform possible combination therapies in the future.