Immunotherapeutic Approaches to Target Cancer Stem Cell: Progress and Challenges

The success of immunotherapeutic approaches for melanoma and non-small cell lung cancer raised hope for the treatment of other malignancies as well. However, resistance to the cancer therapies developed by tumor cells is the biggest challenge in the cancer treatment. Due to the heterogeneous nature of cancer, the bulk tumor consists of diverse cells having distinct molecular, morphological and phenotypic signatures with differential levels of sensitivity to treatment [1,2]. The cancer stem cells (CSCs) that are rare immortal cells of bulk tumor have the capability to self-renew by dividing and give rise to many cell types that constitute the tumor. CSCs are increasingly identified as the source of tumor progression, metastasis, and cancer therapy resistance and relapse [2,3]. Treatment strategies that can eliminate CSCs and nonCSCs suggested improving the long-term clinical outcome for cancer patients. Since immunotherapy directly utilizes the immune cells and works in the distinct principle from chemotherapy or small molecule therapy, it can be an alternative therapeutic approach to target CSCs.