FIGURE 7 from Cancer-associated Fibroblast–specific Expression of the Matricellular Protein CCN1 Coordinates Neovascularization and Stroma Deposition in Melanoma Metastasis

CCN1 expression by fibroblasts is associated with increased tumor penetration of CD4⁺ T cells and resistance to anti-PD1 checkpoint inhibitors. A, Tumors were subjected to flow cytometry with anti-CD4 anti-CD8 antibodies. Percentage of positive CD45-staining cells are indicated wild type (n = 3, CCN1f/f) and CCN1-deficient (n = 3, CCN1−/−) tumors (Student t test). Primary flow data of the median value is presented Tissue was examined after 14 days of tumor growth. B, Boxplot shows higher levels of CAF-specific CCN1 scores in patients on checkpoint inhibitors with progressive disease (GSE78220). A six-gene set of CAF-specific genes correlating with CCN1 (PDGFRA, COL1A1, DCN, TAGLN, COL6A3, and LPAR1), as described in Materials and Methods, was analyzed. P value (unpaired t test) displayed in top left corner. n = 14 in the responders and n = 12 in the progressive disease. C and D, Loss of CCN1 expression results in reduced MMP-9 expression in CCN1-deficient mice. Real-time PCR analysis of RNAs isolated from Ccn1+/+ and Ccn1⁻/⁻ dermal fibroblasts from 3 different mice (N = 3; C) or skin (N = 4 Ccn1+/+, N = 8, Ccn1⁻/⁻; D) reveal that CCN1-deficient fibroblasts have reduced expression of the anti-PD1 resistance marker/effector MMP-9 (Student unpaired t test; *, P < 0.05). Please note that D was conducted on identical skin samples to those published previously (29).