Table 1.

Common immunotherapy approaches.

Common Immunotherapy Approaches	Principle	Current Clinical Applications
Immune checkpoint blockade therapy	This is a type of therapy that blocks the action of immune checkpoints by artificially administering inhibitors of immune checkpoints or their ligands, thereby upregulating T cells activity and improving the body’s anti-tumor immune response. The most commonly used inhibitors are monoclonal antibodies to the corresponding molecules, such as PD-1/PD-L1 monoclonal antibodies and CTLA-4 monoclonal antibodies.	breast cancer, lung cancer, hepatocellular carcinoma, prostate cancer, melanoma, MSI-H/dMMR colorectal cancer RCC, lymphoma, MCC, urothelial cancer [18].
Therapeutic antibodies	Laboratory-designed antibodies destroy tumor cells by inducing direct apoptosis, antibody-dependent cytotoxicity, and complement-dependent cytotoxicity. Common therapeutic antibodies include rituximab and panitumumab.	breast cancer, colorectal cancer, lymphoma, melanoma, head and neck cancer, NSCLC, RCC, cervical cancer [19].
Cancer vaccine	Tumor antigens are introduced into patients in the form of tumor cells, tumor-related proteins or peptides, and genes that express tumor antigens, so as to activate patients′ own immune responses and reduce immune suppression caused by tumors, thus achieving control or clearance of the tumor. They can be divided into prophylactic and therapeutic vaccines, such as the cervical cancer vaccine and the Sipuleucel-T vaccine.	pancreatic cancer, lymphoma, breast cancer, NSCLC, gastric cancer, glioblastoma, cervical cancer, prostate cancer [20].
Adoptive cellular immunotherapy	Immune cells are collected from the patient’s blood, and the collected immune cells are then genetically edited to change ordinary immune cells into immune cells that can recognize tumor cells, expanded and cultured, and then infused back into the patient with such immune cells that can trigger the killing effect of tumor cells, thus playing the role of anti-tumor immunity. The available immune cells are autologous lymphokine-activated killer cells, natural killer cells, cytokine-induced killer cells, cytotoxic T cells, and genetically modified T cells, etc.	melanoma, renal cell carcinoma, breast cancer, cervical cancer, gastrointestinal cancers, cholangiocarcinoma, pancreatic cancer, head and neck cancer, ovarian cancer, NSCLC [21].
Small-molecule inhibitors	There are many small-molecule proteins in tumor cells and in the tumor microenvironment, which can promote the occurrence and development of tumors by inhibiting the anti-tumor immunity, and promoting the accumulation of abnormal mutations and the abnormal proliferation of tumor cells. By artificially providing inhibitors of these small-molecule proteins, the above abnormal responses can be cut off and tumor progression can be inhibited. Common small-molecule inhibitors include IDO inhibitors, PARP inhibitors, MEK inhibitors, VEGFR inhibitors, etc.	breast cancer, ovarian cancer, thyroid cancer, soft tissue sarcoma, colorectal cancer, melanoma, pancreatic cancer, renal cell carcinoma, NSCLC, leukemia [22].

Abbreviations: CTLA-4, cytotoxic T lymphocyte-associated antigen-4; IDO, indoleamine 2,3-dioxygenase; PARP, poly ADP-ribose polymerase; VEGFR, vascular endothelial growth factor receptor; NSCLC, non-small lung cancer; MSI-H, high levels of Microsatellite Instability; dMMR, different mismatch repair; HCC, hepatocellular carcinoma; RCC, renal cell carcinoma; MCC, Merkel cell carcinoma.