Figure 3.

(A) Many nonreplicating viral vectors namely Adenovirus, Adeno-associated virus, HSV, Lentivirus, Retrovirus, Baculovirus, and Paravirus are being used to deliver suicide genes and immunostimulatory genes in the ongoing clinical studies to treat glioblastoma. The suicide gene converts nontoxic prodrugs into toxic products in tumor cells, causing tumor cell killing. (B) Oncolytic viruses can occur naturally or be genetically engineered by modifying natural viruses. These viruses can selectively infect and kill tumor cells without damaging the healthy cells. (C) CAR T-cell therapy involves genetic modification of a patient’s T-cells to produce CAR, which helps the T cells to recognize and target cancer cells. So once the modified CAR T-cells are reinfused into the patient, the new receptor will enable them to target and kill cancer cells. (D) Checkpoint inhibitors are monoclonal antibodies that target proteins on the surface of cancer cells or immune cells which are involved in the regulation of T and NK cell activation, key examples of which include CTLA-4 and PD-1 pathways.