Improving the in vivo persistence, distribution and function of cytotoxic T lymphocytes by inhibiting the tumor immunosuppressive microenvironment

Upregulation of CD3ζ and L-selectin in antigen-specific cytotoxic T lymphocytes by eliminating myeloid-derived suppressor cells with doxorubicin to improve killing efficacy of neuroblastoma cells in vitro

Background

Agglomeration of myeloid‐derived suppressor cells (MDSCs) in tumors impedes immunotherapeutic effects. Doxorubicin (DOX) is currently the most specific drug used for the selective removal of MDSCs. Here, we study the feasibility and mechanism of eliminating MDSCs by DOX to improve antigen‐specific cytotoxic T lymphocyte (CTL)‐killing neuroblastoma (NB) cells in vitro.

Methods

CTL and MDSC were prepared; then, CTLs, NB cells, MDSCs, and DOX were mixed and cultivated in different collocation patterns and divided into different groups. The levels of cluster of differentiation 3ζ chain (CD3ζ) and L‐selectin in CTL in different groups were detected. Thereafter, the killing rate of NB cells and secretion of interleukin‐2 and interferon‐γ were measured and compared.

Results

By real‐time polymerase chain reaction (PCR) and Western blot test respectively, the proliferation and killing effect of CTLs on NB cells were all inhibited by MDSC through downregulating CD3ζ (p = 0.002; p = 0.001) and L‐selectin (p = 0.006; p < 0.001). However, this inhibitory effect was reversed by DOX. Significant differences were observed in the levels of interleukin‐2 (p < 0.001), interferon‐γ (p < 0.001), and the killing rate (p < 0.001) among the groups, except between the CTL +SK‐N‐SH and CTL +SK‐N‐SH +DOX groups (p > 0.05).

Conclusions

Targeted elimination of MDSCs by DOX can improve Ag‐specific CTL killing of NB cells in vitro by upregulating CD3ζ and L‐selectin. This study provides a novel method to enhance the immunotherapeutic effects of NB.

Nanoparticles: augmenting tumor antigen presentation for vaccine and immunotherapy treatments of cancer

The major goal of immunity is maintaining host survival. Toward this, immune cells recognize and eliminate targets that pose a danger. Primarily, these are external invaders (pathogens) and internal invaders (cancers). Their recognition relies on distinguishing foreign components (antigens) from self-antigens. Since cancer cells are the host's own cells that are harmfully altered, they are difficult to distinguish from normal self. Furthermore, the antigens least resembling the host are often sequestered in parts of the tumor least accessible to immune responses. Therefore, to sufficiently boost immunity, these tumor antigens must be exposed to the immune system. Toward this, nanoparticles provide an innovating means of tumor antigen presentation and are destined to become an integral part of cancer immunotherapy.

Relevance of tumor-infiltrating lymphocytes in breast cancer

While breast cancer has not been considered a cancer amenable to immunotherapeutic approaches, recent studies have demonstrated evidence of significant immune cell infiltration via tumor-infiltrating lymphocytes in a subset of patient tumors. In this review we present the current evidence highlighting the clinical relevance and utility of tumor-infiltrating lymphocytes in breast cancer. Retrospective and prospective studies have shown that the presence of tumor-infiltrating lymphocytes is a prognostic marker for higher responses to neoadjuvant chemotherapy and better survival, particularly in triple negative and HER2-positive early breast cancer. Further work is required to determine the immune subsets important in this response and to discover ways of encouraging immune infiltrate in tumor-infiltrating lymphocytes-negative patients.

Enhancing the efficacy of adoptive cellular therapy by targeting tumor-induced immunosuppression

Strategies aimed at stimulating the immune system against cancer have signaled a new era for designing new effective therapies for patients. Recent breakthroughs in adoptive cellular therapy and in using checkpoint inhibitors for some patients have renewed much enthusiasm in this field. However, it has become apparent that tumors can use a multitude of inhibitory networks to effectively reduce antitumor immunity. This review discusses our current knowledge of these immune suppressive mechanisms used by tumors and describes potential new strategies that may counteract this problem resulting in significantly increasing therapeutic outcomes of adoptive immunotherapy in a higher proportion of patients.