When mouse models of immune-excluded breast or metastatic CRC were co-treated with TGF-β and PD-L1 inhibitors, the expression of matrix-remodelling factors in CAFs was reduced and T cells were then able to penetrate both primary and metastatic tumour masses to cause regression.17,18 However, the consequences of attempts to manipulate the immune system for cancer treatment are not always predictable due to the complex interplay between different cell types in the tumour microenvironment, including fibroblasts. This evidence concerns the gene TGFB1 and neoplasm.