BRCA mutational status shapes the stromal microenvironment of pancreatic cancer linking CLU+ CAF expression with HSF1 signaling
2Department of Chemistry and Center for Molecular Discovery (BU-CMD), Boston University,, USA
3Children’s Cancer and Blood Foundation Laboratories, Departments of Pediatrics, and Cell and Developmental Biology, Drukier Institute for Children’s Health, Meyer Cancer Center, Weill Cornell Medicine, USA
4Hepatopancreatobiliary Service, Department of Surgery, Memorial Sloan Kettering Cancer Center, USA
5David M. Rubenstein Center for Pancreatic Cancer Research, Memorial Sloan Kettering Cancer Center, USA
6The Fuld Family Medical Genetics Institute, Faculty of Medicine, Shaare Zedek Medical Center, The Hebrew University of Jerusalem, Israel
7Human Oncology and Pathogenesis Program, Memorial Sloan Kettering Cancer Center, USA
8Oncology Institute, Sheba Medical Center at Tel-Hashomer, Tel Aviv University, Israel
9Cancer Center, Cold Spring Harbor Laboratory, Cold Spring Harbor, USA
10Gastrointestinal Oncology Service, Memorial Sloan Kettering Cancer Center, and Weill Cornell Medical College, USA
Tumors initiate by mutations in cancer cells, and progress through interactions of the mutated cancer cells with non-malignant cells of the tumor microenvironment (TME). Yet the extent to which the composition of the TME is dictated by specific mutations in the cancer cells is unknown. Major players in the TME are Cancer-associated fibroblasts (CAFs). CAFs give rise to desmoplastic stroma which supports tumor progression and metastasis, and comprises up to 90% of the tumor mass in pancreatic cancer. Work by us and others has shown that CAFs are transcriptionally rewired by adjacent cancer cells to form heterogeneous subtypes. Whether this rewiring is differentially affected by different driver mutations in cancer cells is largely unknown. Here we address this question by dissecting the stromal landscape of BRCA-mutated and BRCA Wild-type (WT) pancreatic ductal adenocarcinoma (PDAC). We comprehensively analyze PDAC samples from a cohort of 42 patients by laser-capture microdissection, RNA-sequencing, and multiplexed immunofluorescence, revealing different CAF subtype compositions in germline BRCA-mutated vs. BRCA-WT tumors. In particular, we detect an increase in a subset of Clusterin (CLU)-positive CAFs in BRCA-mutated tumors. Using cancer organoids, co-cultures, and in-vivo models we show that loss of BRCA function in cancer cells leads to a transcriptional shift of pancreatic stellate cells from myofibroblastic into immune-regulatory CLU+ CAFs. This process is mediated through the activation of heat-shock factor 1 (HSF1), the transcriptional regulator of Clu. Our findings unravel a new dimension of stromal heterogeneity, influenced by germline mutations in cancer cells, with direct translational implications for clinical research.