Cancer associated fibroblasts (CAFs) can help tumours evade immune-surveillance by affecting the immune cell infiltrate, mainly via secretion of cytokines and chemokines. CAFs phenotype and spatial relationship to cancer cells alter the kind of cytokines and chemokines they secrete. In Squamous cell carcinoma (SCC), cancer-associated fibroblasts can trigger a Type I Interferon when in direct cell-cell contact with cancer cells.
Bioinformatics: we used publicly available RNAseq data from The Cancer Genome Atlas (TCGA) for Head and Neck Squamous Cell Carcinoma (HNSCC 518 tumours. [http://firebrowse.org/]) . Using the RSEM normalized gene expression, we divided tumours according to the expression of CAF markers not expressed in cancer cells (FAP, Thy-1, s100a4and PDGFRb). We used CIBERSORT to estimate the abundance of immune cells in the tumours. In vitro assays: we used A431 (human SCC cell line) and CAFs extracted from a human tumour in our lab. We cultured them in either direct cell-to-cell contact or using a transwell. We treated the A431 with AZD6738 (ATR inhibitor), 5-aza-2′-deoxycytidine and cisplatin. We analysed mRNA expression of different interferon response genes by qRT-PCR.
To explore the relevance of CAF influence in the immune infiltrate we analysed RNA seq data from HNSCC in TCGA. Tumours with higher expression of FAP and PDGFRb showed a higher proportion of infiltrating M0 and M2 macrophages. Tumours with lower expression of FAP and PDGFRb had higher proportions of activated dendritic cells and CD8 positive lymphocytes. In an “in vitro” human SCC model, heterotypic cancer cell-CAF contact leads to transfer of double stranded DNA from the cancer cell to the fibroblasts. This interaction triggers cGAS-STING mediated production of Interferon b (IFNb) in the CAFs. We treated cancer cells with drugs that generate genomic damage i.e. AZD6738, 5-aza and cisplatin. Treatment with these drugs increased the signal initiated by IFNb.
CAF subtypes abundance correlates with an immunosuppressive tumour microenvironment in HNSCC. Drugs currently used for routine treatment or in clinical trials for HNSCC modulate cytokine and chemokine production by CAFs in an “in vitro” model.
Clinical trial identification
Legal entity responsible for the study
The Francis Crick Institute.
Cancer Research UK.
K. Harrington: Consultancy (Includes expert testimony): Amgen, AstraZeneca, BMS, Merck, MSD, Pfizer; Research funding: AstraZeneca, MSD; Honoraria: Amgen, AstraZeneca, BMS, Merck, MSD, Pfizer, Replimune; Speakers' bureau: Amgen, AstraZeneca, BMS, Merck, MSD, Pfizer; Membership on any entity’s Board of Directors or advisory committees: Amgen, AstraZeneca, BMS, Merck, MSD, Pfizer, Replimune (Scientific advisory board memberships). All other authors have declared no conflicts of interest.