Immunotherapy for colorectal cancer: Rational strategies and novel therapeutic progress

There are increasing incidences and mortality rates for colorectal cancer in the world. It is common for chemotherapy and radiation given to patients with colorectal cancer to cause toxicities that limit their effectiveness and cause cancer cells to become resistant to these treatments. Additional targeted treatments are needed to improve patient's quality of life and outcomes. Immunotherapy has rapidly emerged as an incredibly exciting and promising avenue for cancer treatment in recent years. This innovative approach provides novel options for tackling solid tumors, effectively establishing itself as a new cornerstone in cancer treatment. Specifically, in the realm of colorectal cancer (CRC), there is great promise in developing new drugs that target immune checkpoints, offering a hopeful and potentially transformative solution. While immunotherapy of CRC has made significant advances, there are still obstacles and limitations. CRC patients have a poor response to treatment because of the immune-suppressing function of their tumor microenvironment (TME). In addition to blocking inhibitory immune checkpoints, checkpoint-blocking antibodies may also boost immune responses against tumors. The review summarizes recent advances in immune checkpoint inhibitors (ICIs) for CRC, including CTLA-4, PD-1, PD-L1, LAG-3, and TIM-3.

Evolution of heat shock protein and immunity

Heat shock proteins (hsps) are among the most abundant intracellular proteins. Their synthesis is rapidly up-regulated by various 'stressors' including temperature, glucose deprivation, infection and cancer. Certain hsps are able to: (i). associate and chaperone a large variety of cellular peptides; (ii). be efficiently internalized by antigen presenting cells (APC) through receptor-mediated endocytosis; (iii). channel antigenic peptides they chaperone in the APC's MHC class I presentation pathway; (iv). and stimulate inflammatory cytokines, chemokines and co-stimulatory molecules through the NFkappab signaling pathway. Extracellular release of hsps upon necrotic cell death and their modulated access at the surface of some cells, can be considered as a putative 'danger' signal. Based on the ancient origins and structural conservation of hsps, it has been proposed that, the role of hsps in immunity emerged early in evolution and to be widespread in extant organisms. Data from studies with the frog Xenopus support this proposition.

Down-Regulation of Tumoricidal NK and NK T Cell Activities by MHC Kb Molecules Expressed on Th2-Type γδ T and αβ T Cells Coinfiltrating in Early B16 Melanoma Lesions

We examined whether γδ T and αβ T cells accumulating in early B16 melanoma lesions regulate NK and NK T cells that attack tumor cells. Freshly isolated and cultured tumor-infiltrating lymphocyte (TIL) populations of NK and NK T cells lysed B16 and produced IFN-γ, whereas γδ T and a large part of αβ T cell populations had no substantial cytotoxicity against B16 and secreted Th2 cytokines. Furthermore, the freshly isolated NK1.1+ TIL population exhibited a higher anti-B16 effect than did splenocytes. γδ T and αβ T cell populations dramatically inhibited the cytotoxicity of NK and NK T cells in an MHC Kb-dependent manner. Culture supernatant from γδ T and αβ T cell populations inhibited the proliferation of NK and NK T cell populations but did not affect their cytotoxicity, suggesting that the released Th2 cytokines are merely partly involved in the down-modulation of NK-lineage cells. NK1.1+ cells obtained from TIL of γδ T cell-depleted mice significantly lysed B16 cells compared with those from control mice. Finally, anti-Kb Fab mAb injected intralesionally at an early, but not at a late, stage of development of B16 melanoma inhibited tumor growth. These findings suggest that Th2-type γδ T and αβ T cells infiltrating in early B16 development inhibit the tumoricidal activity of NK-lineage cells using their class I molecules and partly their suppressive cytokines.