The mechanism of HSV-TK/prodrug-mediated cell death can be variable involving necrotic and immunogenic cell death (ICD) in melanoma cells, but apoptotic and non-ICD in colorectal cancer cells.77 Glioma cells also undergo HSV-TK/prodrug-mediated cell death via apoptosis.78,79 The immunogenicity of apoptosis in general is controversial and not yet fully explored, in particular not in the context of SGT. The gene discussed is TKT; the disease is colorectal cancer.