TBX1 and cancer: Finally, to further validate the functional importance of Collagen XII expression in metastatic dissemination, we orthotopically co-implanted cancer cells with CAFs overexpressing collagen XII (ColXII-VPR1, ColXII-VPR2) or control CAFs (eGFP-VPR), into the fourth mammary fatpad (1:3 ratio cancer cells to CAFs) similar to the knockdown experiments.