Curtis, Marion

Abstract Adoptive Cell Transfer (ACT) therapies have recently fostered excitement for the treatment of hematogenous cancers. However, efficacy has largely been stunted in the treatment of solid tumors, especially for ovarian cancer, in part due to nutrient restriction within the tumor microenvironment. We recently demonstrated that intracellular delivery of biodegradable microparticles (MPs) made from polymers of alpha-ketoglutarate modulated dendritic cell energy metabolism and immunophenotype, altering regulatory and helper T cell frequencies. To determine if continuous metabolite release from MPs would rescue T cell dysfunction in nutrient-poor, immunosuppressive conditions, we generated MPs of polymerized glycolytic and tricarboxylic acid cycle central-carbon metabolites. Flow cytometric analysis and confocal microscopy indicated that FITC-conjugated MPs were efficiently loaded into the cytoplasm of activated primary murine T cells via membrane adsorption or electroporation. The MPs were retained intracellularly and sustained proliferation of mouse T cells for over five days in vitro. Glycolysis and mitochondrial respiration stress tests using an Agilent Seahorse XFe96 Analyzer demonstrated that primary mouse CD8 T cells utilized the MPs as a metabolic substrate. In particular, MPs increased metabolic function, as indicated by increased spare respiratory capacity, glycolysis, and glycolytic capacity. The results of this study provide preliminary evidence in support of utilizing sustained-releasing particles of metabolic substrates for the metabolic reprogramming of immune cells used in ACT therapies. This strategy has potential to improve or expand the efficacy of existing ACT therapies for solid tumors.

Background Increased infiltration of T cells into ovarian tumors has been repeatedly shown to be predictive of enhanced patient survival. However, despite the evidence of an active immune response in ovarian cancer (OC), the frequency of responses to immune checkpoint blockade (ICB) therapy in OC is much lower than other cancer types. Recent studies have highlighted that deficiencies in the DNA damage response (DDR) can drive increased genomic instability and tumor immunogenicity, which leads to enhanced responses to ICB. Protein phosphatase 4 (PP4) is a critical regulator of the DDR; however, its potential role in antitumor immunity is currently unknown. Results Our results show that the PP4 inhibitor, fostriecin, combined with carboplatin leads to increased carboplatin sensitivity, DNA damage, and micronuclei formation. Using multiple OC cell lines, we show that PP4 inhibition or PPP4C knockdown combined with carboplatin triggers inflammatory signaling via Nuclear factor kappa B (NF-κB) and signal transducer and activator of transcription 1 (STAT1) activation. This resulted in increased expression of the pro-inflammatory cytokines and chemokines: CCL5 , CXCL10 , and IL-6 . In addition, IFNB1 expression was increased suggesting activation of the type I interferon response. Conditioned media from OC cells treated with the combination of PP4 inhibitor and carboplatin significantly increased migration of both CD8 T cell and natural killer (NK) cells over carboplatin treatment alone. Knockdown of stimulator of interferon genes (STING) in OC cells significantly abrogated the increase in CD8 T-cell migration induced by PP4 inhibition. Co-culture of NK-92 cells and OC cells with PPP4C or PPP4R3B knockdown resulted in strong induction of NK cell interferon-γ, increased degranulation, and increased NK cell-mediated cytotoxicity against OC cells. Stable knockdown of PP4C in a syngeneic, immunocompetent mouse model of OC resulted in significantly reduced tumor growth in vivo . Tumors with PP4C knockdown had increased infiltration of NK cells, NK T cells, and CD4 + T cells. Addition of low dose carboplatin treatment led to increased CD8 + T-cell infiltration in PP4C knockdown tumors as compared with the untreated PP4C knockdown tumors. Conclusions Our work has identified a role for PP4 inhibition in promoting inflammatory signaling and enhanced immune cell effector function. These findings support the further investigation of PP4 inhibitors to enhance chemo-immunotherapy for OC treatment.

Disruption of metabolic homeostasis at the organismal level can cause metabolic syndrome associated with obesity. The role of adipose tissue in cancer has been investigated over the last several decades with many studies implicating obesity as a risk factor for the development of cancer. Adipose tissue contains a diverse array of immune cell populations that promote metabolic homeostasis through a tightly controlled balance of pro- and anti-inflammatory signals. During obesity, pro-inflammatory cell types infiltrate and expand within the adipose tissue, exacerbating metabolic dysfunction. Some studies have now shown that the intracellular metabolism of immune cells is also deregulated by the lipid-rich environment in obesity. What is not fully understood, is how this may influence cancer progression, metastasis, and anti-tumor immunity. This review seeks to highlight our current understanding of the effect of adipose tissue on immune cell function and discuss how recent results offer new insight into the role that adipose tissue plays in cancer progression and anti-tumor immunity.

Metabolites control immune cell functions, and delivery of these metabolites in a sustained manner modulate the function of the immune cells.