Heavily pretreated CRC patients were administered the oncolytic vaccinia virus Pexa-Vec [JX-594] engineered to express GM-CSF, a hematopoietic growth factor that increases dendritic cell differentiation, maturation and function and induced tumor reactive T cells and reached stable disease in 67% (n = 10) of patients (40, 41). The gene discussed is CSF2; the disease is colorectal carcinoma.