Lactate is a key metabolite produced from glycolytic metabolism of glucose molecules, yet it also serves as a primary carbon fuel source for many cell types. In the tumor-immune microenvironment, effect of lactate on cancer and immune cells can be highly complex and hard to decipher, which is further confounded by acidic protons, a co-product of glycolysis. Here we show that lactate is able to increase stemness of CD8⁺ T cells and augments anti-tumor immunity. Subcutaneous administration of sodium lactate but not glucose to mice bearing transplanted MC38 tumors results in CD8⁺ T cell-dependent tumor growth inhibition. Single cell transcriptomics analysis reveals increased proportion of stem-like TCF-1-expressing CD8⁺ T cells among intra-tumoral CD3⁺ cells, a phenotype validated by in vitro lactate treatment of T cells. Mechanistically, lactate inhibits histone deacetylase activity, which results in increased acetylation at H3K27 of the Tcf7 super enhancer locus, leading to increased Tcf7 gene expression. CD8⁺ T cells in vitro pre-treated with lactate efficiently inhibit tumor growth upon adoptive transfer to tumor-bearing mice. Our results provide evidence for an intrinsic role of lactate in anti-tumor immunity independent of the pH-dependent effect of lactic acid, and might advance cancer immune therapy.

Stimulator of interferon genes (STING) is an immune adaptor protein that senses cyclic GMP-AMP in response to self or microbial cytosolic DNA as a danger signal. STING is ubiquitously expressed in diverse cell populations, including cancer cells, with distinct cellular functions, such as activation of type I interferons, autophagy induction, or triggering apoptosis. It is not well understood whether and which subsets of immune cells, stromal cells, or cancer cells are particularly important for STING-mediated antitumor immunity. Here, using a polymeric STING-activating nanoparticle (PolySTING) with a shock-and-lock dual activation mechanism, we show that conventional type 1 dendritic cells (cDC1s) are essential for STING-mediated rejection of multiple established and metastatic murine tumors. STING status in the host but not in the cancer cells ( Tmem173 ^−/− ) is important for antitumor efficacy. Specific depletion of cDC1 ( Batf3 ^−/− ) or STING deficiency in cDC1 ( XCR1 ^cre STING ^fl/fl ) abolished PolySTING efficacy, whereas depletion of other myeloid cells had little effect. Adoptive transfer of wild-type cDC1 in Batf3 ^−/− mice restored antitumor efficacy, whereas transfer of cDC1 with STING or IRF3 deficiency failed to rescue. PolySTING induced a specific chemokine signature in wild-type but not Batf3 ^−/− mice. Multiplexed immunohistochemistry analysis of STING-activating cDC1s in resected tumors correlates with patient survival. Furthermore, STING-cDC1 signature was increased after neoadjuvant pembrolizumab therapy in patients with non–small cell lung cancer. Therefore, we have defined that a subset of myeloid cells is essential for STING-mediated antitumor immunity with associated biomarkers for prognosis.

Monoclonal antibodies (mAbs) are extensively employed for disease diagnosis and treatment because of their high homogeneity and antigen specificity. In recent years, important outcomes have been achieved with mAbs due to their admirable therapeutic efficacy and relatively rare side effects. In clinical practice, several mAb products have been approved by regulatory entities, but their formulations have been highly specific given the complex structure and proteinaceous nature of mAbs. Thus, more attention has been given on formulations. An increasing number of novel delivery systems have been exploited to optimize the application of mAbs. In this article, the formulations, dosages, origins and administration routes of available mAbs approved by the Food and Drug Administration (FDA) are summarized and categorized. Key issues involved in formulation, processing and storage are addressed as well as other challenges in achieving effective mAb delivery. Finally, recent advances in delivering mAbs in their most bioavailable forms are also briefly reviewed.