Semaphorin3A induces fibroblast polarization towards an antitumor phenotype in pancreatic ductal adenocarcinoma

Background and Aims Pancreatic Ductal Adenocarcinoma (PDAC) is a deadly and challenging disease due to its hostile, fibrotic and immunosuppressed tumor microenvironment (TME) that lessens the efficacy of current treatment options. Therefore, there is a strong need to develop novel therapeutic strategies that efficiently target the TME to hamper PDAC progression. Methods Single cell RNA-sequencing analysis was performed after purifying the TME from PDAC mouse models treated with a mutated form of the Sema3A (mut-Sema3A) able to bind PlexinA4 with higher affinity. PDAC patient single cells datasets were assessed for the Semaphorin-Associated Fibroblasts signature. Results It has been shown that the treatment with mut-Sema3A, by efficiently normalizing the vessel network, could impair tumor growth and synergized with chemotherapeutic drugs in PDAC mice (1). Single cell analysis of the TME of PDAC treated with mut-Sema3A unveiled a profound change: the re-population and gene re-programming of an unconventional Cancer Associated Fibroblast (CAF) subclass, which exhibited cancer restraining features. We established a novel gene signature defining these anti-tumor CAFs, called Semaphorin-Associated Fibroblasts (SemAFs), enriched for genes such as PDGFRA, ISLR, MMP2, CYGB, THBS2, CDH11. Among them, ISLR, coding for the Meflin protein, has been correlated with improved survival and prognosis of PDAC patients and anti-tumor properties (2). Interestingly, mut-Sema3A directly enhanced the expression of SemAF genes and inhibited the chemo-invasion potential in an ex-vivo activated fibroblast model. Mut-Sema3A significantly enhanced PlexinA4 expression in CAFs, suggesting an autocrine loop of mut-Sema3A treatment that upregulates its own receptor. Remarkably, the SemAF signature was found and correlated with good overall survival in chemotherapy-treated PDAC patients. Conclusion These findings unveiled a novel role of mut-Sema3A in re-programming CAFs in an anti-tumor phenotype and demonstrated its suitability at being coupled with pre-existing therapies to more efficiently hamper PDAC progression. References 1. Gioelli N, Maione F, Camillo C, Ghitti M, Valdembri D, Morello N, et al. A rationally designed NRP1-independent superagonist SEMA3A mutant is an effective anticancer agent. Science Translational Medicine. 2018;10:eaah4807. 2. Mizutani Y, Kobayashi H, Iida T, Asai N, Masamune A, Hara A, et al. Meflin-Positive Cancer-Associated Fibroblasts Inhibit Pancreatic Carcinogenesis. Cancer Res. United States; 2019;79:5367–81. Funding 5X1000 Ministry of Health AIRC PRIN 2022 PNNR