Single-cell RNA sequencing reveals stromal evolution into LRRC15+ myofibroblasts as a determinant of patient response to cancer immunotherapy
With only a fraction of patients responding to cancer immunotherapy, a better understanding of the entire tumor microenvironment is needed. Using single-cell transcriptomics we chart the fibroblastic landscape during pancreatic ductal adenocarcinoma (PDAC) progression in animal models. We identify a population of carcinoma-associated fibroblasts (CAFs) programmed by transforming growth factor beta and expressing the leucine-rich repeat containing 15 (LRRC15) protein. These LRRC15+ CAFs surround tumor islets and are absent from normal pancreatic tissue. The presence of LRRC15+ CAFs in human patients was confirmed in >80,000 single-cells from 22 PDAC patients as well as immunohistochemistry on samples from 70 patients. Furthermore, immunotherapy clinical trials comprising over 600 patients across 6 cancer types revealed elevated levels of the LRRC15+ CAF signature correlated with poor response to anti-PD-L1 therapy. This work has important implications for targeting non-immune elements of the tumor microenvironment to boost responses of cancer patients to immune checkpoint blockade therapy.