Increased activity of tissue transglutaminase accompanied the increased resistance to trypsinization in murine sarcoma RIF-1 cells, HT29 human colonic carcinoma cells, and ECV304 human umbilical vein endothelial cells after photodynamic therapy using pyridinium zinc (II) phthalocyanine as sensitizer37. The gene discussed is TGM2; the disease is colon carcinoma.