CAR T cell therapy: A new era for cancer treatment

Cancer has recently been identified as the leading cause of mortality worldwide. Several conventional treatments and cytotoxic immunotherapies have been developed and made available to the market. Considering the complex behavior of tumors and the involvement of numerous genetic and cellular factors involved in tumorigenesis and metastasis, there is a need to develop a promising immunotherapy that targets tumors at both the cellular and genetic levels. Chimeric antigen receptor (CAR) T cell therapy has emerged as a novel therapeutic T cell engineering practice, in which T cells derived from patient blood are engineered in vitro to express artificial receptors targeted to a specific tumor antigen. These directly identify the tumor antigen without the involvement of the major histocompatibility complex. The use of this therapy in the last few years has been successful, with a reduction in remission rates of up to 80% for hematologic cancer, particularly for acute lymphoblastic leukemia (ALL) and non-Hodgkin lymphomas, such as large B cell lymphoma. Recently, anti-CD19 CAR therapy, or UCART19, has been shown to be efficacious in treating relapsed/refractory hematologic cancer. Several other cell surface tumor antigens, such as CD20 and CD22, found in the majority of leukemias and lymphomas are considered potential targets by pharmaceutical companies and research organizations, and trials have been ongoing in this direction. Although this therapeutic regimen is currently confined to treating hematologic cancer, the increasing involvement of several auxiliary techniques, such as bispecific CAR, Tan-CAR, inhibitory-CAR, combined antigens, the clustered regularly interspaced short palindromic repeats gene-editing tool and nanoparticle delivery, may substantially improve its overall anticancer effects. CAR therapy has the potential to offer a rapid and safer treatment regime to treat non-solid and solid tumors. The present review presents an insight into the advantages and the advances of CAR immunotherapy and presents the emerging discrepancy of CAR therapy over usual forms of therapy, such as chemotherapy and radiotherapy.