Addition of losartan to FOLFIRINOX and chemoradiation reduces immunosuppression-associated genes, Tregs and FOXP3+ cancer cells in locally advanced pancreatic cancer

Purpose: Adding losartan (LOS) to FOLFIRINOX (FFX) chemotherapy followed by chemoradiation (CRT) resulted in 61% R0 surgical resection in our phase II trial in patients with locally advanced pancreatic cancer (LAPC). Here we identify potential mechanisms of benefit by assessing the effects of neoadjuvant losartan on the stromal tumor microenvironment. Experimental Design: We performed a gene expression and immunofluorescence (IF) analysis using archived surgical samples from patients treated with LOS+FFX+CRT (NCT01821729), FFX+CRT (NCT01591733) or surgery upfront, without any neoadjuvant therapy. We also conducted a longitudinal analysis of multiple biomarkers in the plasma of treated patients. Results: In comparison to FFX+CRT, LOS+FFX+CRT downregulated immunosuppression and pro-invasion genes. Overall survival (OS) was associated with DC and antigen presentation genes for patients treated with FFX+CRT, and with immunosuppression and invasion genes or DC– and blood vessel-related genes for those treated with LOS+FFX+CRT. Furthermore, losartan induced specific changes in circulating levels of IL-8, sTie2 and TGF-. IF revealed significantly less residual disease in lesions treated with LOS+FFX+CRT. Lastly, patients with a complete/near complete pathological response in the LOS+FFX+CRT-treated group had reduced CD4+FOXP3+ regulatory T cells (Tregs), fewer immunosuppressive FOXP3+ cancer cells (C-FOXP3) and increased CD8+ T cells in PDAC lesions. Conclusions: Adding losartan to FFX+CRT reduced pro-invasion and immunosuppression related genes which were associated with improved survival in patients with LAPC. Lesions from responders in the LOS+FFX+CRT-treated group had reduced Tregs, decreased C-FOXP3 and increased CD8+ T cells. These findings suggest that losartan may potentiate the benefit of FFX+CRT by reducing immunosuppression. Analysis of gene expression in the immune TME in resected PDAC samples. To characterize the effects and identify potential molecular mechanisms of cytotoxic agents in combination with losartan on the immune TME, we used the nCounter PanCancer Immune Profiling Panel of 730 genes (NanoString) to analyze the RNA extracted from formalin-fixed paraffin embedded (FFPE) PDAC tissue sections.