Carcinomas assemble a filamentous CXCL12–keratin-19 coating that suppresses T cell–mediated immune attack

Abstract

Cancer immunotherapy frequently fails because most carcinomas have few T cells, suggesting that cancers can suppress T cell infiltration. Here, we show that cancer cells of human pancreatic ductal adenocarcinoma (PDA), colorectal cancer, and breast cancer are coated with transglutaminase-2 (TGM2)–dependent covalent CXCL12–keratin-19 (KRT19) heterodimers that are organized as filamentous networks. Since a dimeric form of CXCL12 suppresses the motility of human T cells, we determined whether this polymeric CXCL12–KRT19 coating mediated T cell exclusion. Mouse tumors containing control PDA cells exhibited the CXCL12–KRT19 coating, excluded T cells, and did not respond to treatment with anti–PD-1 antibody. Tumors containing PDA cells not expressing either KRT19 or TGM2 lacked the CXCL12–KRT19 coating, were infiltrated with activated CD8+ T cells, and growth was suppressed with anti–PD-1 antibody treatment. Thus, carcinomas assemble a CXCL12–KRT19 coating to evade cancer immune attack.

T cell-mediated development of stromal fibroblasts with an immune-enhancing chemokine profile

“…We recently reported that a CXCL12/KRT19-coat on mouse pancreatic ductal adenocarcinoma (PDA) cells impairs the accumulation of T cells in nests of cancer cells. CRISPR/Cas9-editing of the Krt19 gene in mouse PDA cells abolishes formation of the CXCL12/KRT19-coat and allows T cell infiltration in tumors formed with these edited cancer cells (Wang et al, 2022). This circumstance, enabled us to examine the effect of the presence of activated T cells in the tumor microenvironment (TME) on CAFs without perturbing other components of the TME that could alter the CAF phenotype, such as TGFβ (Mariathasan et al, 2018).…”

“…Orthotopic tumors formed with mouse PDA cells differing only in their expression of Krt19 , which is required for assembly of the CXCL12/KRT19-coat, had contrasting TMEs that are immune-quiescent and immune-activated (Wang et al, 2022). We use this model to demonstrate two immunological principles.…”

“…First, stromal fibroblasts have the capacity to sense the presence of activated T cells, independently of other variables, such as TGFβ neutralization (Grauel et al, 2020), and develop a subset that has the potential to promote the T cell reaction. This CAF subset, termed T-CAF, has a chemokine profile that would mediate the accumulation of CXCR3-expressing immune cells, such as NK cells, Th1 cells, CD8 + T cells, and dendritic cells (Chow et al, 2019; Groom et al, 2012; Wendel et al, 2008), by coupling the up-regulation of CXCL9 with down-regulation of CXCL12, which otherwise would coat the cancer cells and suppress T cell accumulation (Biasci et al, 2020; Feig et al, 2013; Wang et al, 2022). Interestingly, given its role in auto-immune tissue damage (Feldmann and Maini, 2001; Kalliolias and Ivashkiv, 2016), TNFα is critical in this immunologically cooperative response in that it amplifies the ability of IFNγ to induce the expression of CXCL9 by fibroblasts, including PSCs and CAFs, while suppressing their expression of CXCL12.…”

“…The clonal PDA cancer cell lines were generated as previously described (Wang et al, 2022). Viral dosages for transduction were reduced 10-fold to obtain low OVA expression lines.…”

“…The resistance of many human and mouse carcinomas to inhibition of the PD-1/PD-L1 checkpoint correlates with a relative absence of T cells in cancer cell nests (Fearon, 2017; Joyce and Fearon, 2015). This immune suppressive T cell exclusion phenomenon is mediated, at least in part, by CAF-derived CXCL12 in the form of covalent heterodimers with keratin-19 (KRT19) on the surface of cancer cells (Wang et al, 2022). However, in tissue microenvironments in which T cells accumulate, we hypothesize that CAFs may adopt a contrasting immune-activating phenotype by expressing T cell-attracting chemokines.…”