Establishment of Synergistic Chemoimmunotherapy for Head and Neck Cancer Using Peritumoral Immature Dendritic Cell Injections and Low-Dose Chemotherapies

Repurposing Food and Drug Administration-Approved Drugs to Promote Antitumor Immunity

There has been a major resurgence of interest in immune-based approaches to treat cancer, based largely on the success of checkpoint inhibitors (anti-cytotoxic T-lymphocyte-associated antigen 4, anti-programmed cell death 1, and anti-programmed cell death ligand 1 antibodies) in several malignancies. However, not all tumors respond to checkpoint therapy, and there is clearly a need for additional approaches for enhancing tumor immunity. We summarize the critical elements necessary for mounting an efficacious T-cell response to a tumor. We cite drugs approved by the Food and Drug Administration for no-cancer indications that could be repurposed and used as part of an antitumor immune cocktail. We also list cancer drugs not initially intended to impact tumor immunity (soft repurposing) but that have been found to modulate the immune system. We highlight those drugs that might be used in combination with checkpoint inhibitors to increase response rates and survival of cancer patients. Our focus will be on drugs for which there are limited but existing human data. We cite supporting mechanistic mouse data as well. Repurposing drugs to modulate antitumor immunity is an opportunity to rapidly bring new, effective, and affordable treatments to cancer patients.

Myeloid-derived suppressor cells impede T cell functionality and promote Th17 differentiation in oral squamous cell carcinoma

Oral tumor microenvironment is characterized by chronic inflammation signified with infiltrating leukocytes and soluble mediators which cause immune suppression. However, how immunosuppressive cells like myeloid-derived suppressor cells (MDSCs) maintain the immunosuppressive tumor microenvironment and influence T cell function in oral squamous cell carcinoma (OSCC) patients remains poorly understood. In the present study, we found that percentages of MDSCs were higher in oral cancer patients compared to healthy individuals and correlated with cancer stage. Monocytic MDSCs (M-MDSCs) were prevalent in the periphery, while granulocytic/polymorphonuclear subset dominated the tumor compartment. M-MDSCs suppressed the lymphocyte proliferation and decreased the CD3-ζ (zeta) chain expression and interferon gamma production. The percentage of M-MDSCs in peripheral blood correlated inversely with CD3-ζ chain expression in T cells of these patients. Interleukin 6 (IL-6)-induced phosphorylated STAT3-regulated programmed cell death ligand 1, CCAAT/enhancer-binding proteins alpha and beta and Interleukin 10 expression in MDSCs. MDSCs inhibited TGF-β-driven generation of induced regulatory T cells in vitro. M-MDSCs secreted interleukins IL-6, IL-1β, IL-23 and PGE2 and facilitated T-helper 17 (Th17) cell differentiation which utilizes nitric oxide synthase and cyclooxygenase 2 enzyme activity. Interestingly, OSCC patients showed increased levels of Th17 cells in peripheral blood and tumor tissue. Thus, increased frequency of MDSCs, Th17 cells and decreased expression of CD3-ζ chain portray T cell tolerance and chronic inflammatory state facilitating tumor growth.

High-Density Lipoprotein-Mimicking Nanodiscs for Chemo-immunotherapy against Glioblastoma Multiforme

Glioblastoma multiforme (GBM) is an aggressive primary brain tumor, for which there is no cure. Treatment effectiveness for GBM has been limited due to tumor heterogeneity, an immunosuppressive tumor microenvironment (TME), and the presence of the blood-brain barrier, which hampers the transport of chemotherapeutic compounds to the central nervous system (CNS). High-density lipoprotein (HDL)-mimicking nanodiscs hold considerable promise to achieve delivery of bioactive compounds into tumors. Herein, we tested the ability of synthetic HDL nanodiscs to deliver chemotherapeutic agents to the GBM microenvironment and elicit tumor regression. To this end, we developed chemo-immunotherapy delivery vehicles based on sHDL nanodiscs loaded with CpG, a Toll-like receptor 9 (TLR9) agonist, together with docetaxel (DTX), a chemotherapeutic agent, for targeting GBM. Our data show that delivery of DTX-sHDL-CpG nanodiscs into the tumor mass elicited tumor regression and antitumor CD8+ T cell responses in the brain TME. We did not observe any overt off-target side effects. Furthermore, the combination of DTX-sHDL-CpG treatment with radiation (IR), which is the standard of care for GBM, resulted in tumor regression and long-term survival in 80% of GBM-bearing animals. Mice remained tumor-free upon tumor cell rechallenge in the contralateral hemisphere, indicating the development of anti-GBM immunological memory. Collectively, these data indicate that sHDL nanodiscs constitute an effective drug delivery platform for the treatment of GBM, resulting in tumor regression, long-term survival, and immunological memory when used in combination with IR. The proposed delivery platform has significant potential for clinical translation.

Diamonds in the Rough: Harnessing Tumor-Associated Myeloid Cells for Cancer Therapy

Therapeutic approaches that engage immune cells to treat cancer are becoming increasingly utilized in the clinics and demonstrated durable clinical benefit in several solid tumor types. Most of the current immunotherapies focus on manipulating T cells, however, the tumor microenvironment (TME) is abundantly infiltrated by a heterogeneous population of tumor-associated myeloid cells, including tumor-associated macrophages (TAMs), tumor-associated dendritic cells (TADCs), tumor-associated neutrophils (TANs), and myeloid-derived suppressor cells (MDSCs). Educated by signals perceived in the TME, these cells often acquire tumor-promoting properties ultimately favoring disease progression. Upon appropriate stimuli, myeloid cells can exhibit cytoxic, phagocytic, and antigen-presenting activities thereby bolstering antitumor immune responses. Thus, depletion, reprogramming or reactivation of myeloid cells to either directly eradicate malignant cells or promote antitumor T-cell responses is an emerging field of interest. In this review, we briefly discuss the tumor-promoting and tumor-suppressive roles of myeloid cells in the TME, and describe potential therapeutic strategies in preclinical and clinical development that aim to target them to further expand the range of current treatment options.