Unlike prophylactic vaccines that are generally administered to healthy individuals, cancer vaccines are aiming at treating existing cancer or preventing the development of cancer in certain high-risk individuals. Vaccines that treat existing cancer are known as therapeutic cancer vaccines; therapeutic cancer vaccines are administered to cancer patients and are designed to eradicate cancer cells through strengthening the patient’s own immune responses. The various immune effector mechanisms mobilized by therapeutic vaccination specifically attack and destroy cancer cells and spare normal cells. Thus, therapeutic cancer vaccines, in principle, may be utilized to inhibit further growth of advanced cancers and/or relapsed tumors that are refractory to conventional therapies such as surgery, radiation therapy, and chemotherapy.
In a review of cancer vaccine, scientists mentioned the most of the cancer vaccines such DC vaccines. DCs(Dendritic cells) are the most potent professional antigen-presenting cells (APCs). They act as sentinels at peripheral tissues where they uptake, process, and present pathogen- or host-derived antigenic peptides to naive T lymphocytes at the lymphoid organs in the context of major histocompatibility (MHC). Scientists generated DCs vaccines ex vivo through loading tumor-associated antigen(TTA) to patients’ autologous DCs that are simultaneously treated with adjuvants. DC vaccines that may be used alone or in combination with conventional therapies such as radiotherapy.
TUMOR-INDUCED IMMUNE SUPPRESSION
Active immunization with therapeutic vaccines generally targets the host DCs for effective presentation of tumor-associated antigens and subsequent priming of CD8þ CTLs and CD4þ T helper cells. These tumor-specific T effector cells together with other innate immune cells can result in inhibition or destruction of cancer cells. In the tumor microenvironment, cancer cells produce immunosuppressive soluble factors (TGF- , IL-10, IDO, galectin, and VEGF) and expand or recruit immune regulatory cells (MDSCs, Tregs, and TAMs), which establish an immunosuppressive state at the tumor site. This complex molecular and cellular network attenuates vaccine-induced antitumor immune responses and promotes tumor escape from immune attack. To overcome the immune suppressive mechanisms, novel immune modulators (anti-CTLA-4 and anti-PD1 antibodies) may be used to enhance vaccine potency and restore durable antitumor immunity. Cancer vaccines can also be combined with conventional cancer treatments, such as radiotherapy and chemotherapy, to engage multivalent antitumor effects for optimized therapeutic efficacy.
Effective, safe, and enduring cancer treatments constitute major challenges of medical sciences, with therapeutic cancer vaccines emerging as attractive approaches for provoking long-lasting protective antitumor immunity. Strategically combining vaccine strategies with other agents or approaches that synergistically enhance antitumor immunity and/or engage complementary antitumor responses should also lead to further improved clinical outcomes.
Reference:
Therapeutic cancer vaccines: past, present, and future. Adv Cancer Res. 2013;119:421-75