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.

While IL-2 can potently activate both NK and T cells, its short in vivo half-life, severe toxicity, and propensity to amplify Treg cells are major barriers that prevent IL-2 from being widely used for cancer therapy. In this study, we construct a recombinant IL-2 immunocytokine comprising a tumor-targeting antibody (Ab) and a super mutant IL-2 (sumIL-2) with decreased CD25 binding and increased CD122 binding. The Ab-sumIL2 significantly enhances antitumor activity through tumor targeting and specific binding to cytotoxic T lymphocytes (CTLs). We also observe that pre-existing CTLs within the tumor are sufficient and essential for sumIL-2 therapy. This next-generation IL-2 can also overcome targeted therapy-associated resistance. In addition, preoperative sumIL-2 treatment extends survival much longer than standard adjuvant therapy. Finally, Ab-sumIL2 overcomes resistance to immune checkpoint blockade through concurrent immunotherapies. Therefore, this next-generation IL-2 reduces toxicity while increasing TILs that potentiate combined cancer therapies.

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.

As a potent lymphocyte activator, interleukin-2 (IL-2) is an FDA-approved treatment for multiple metastatic cancers. However, its clinical use is limited by short half-life, low potency, and severe in vivo toxicity. Current IL-2 engineering strategies exhibit evidence of peripheral cytotoxicity. Here, we address these issues by engineering an IL-2 prodrug (ProIL2). We mask the activity of a CD8 T cell-preferential IL-2 mutein/Fc fusion protein with IL2 receptor beta linked to a tumor-associated protease substrate. ProIL2 restores activity after cleavage by tumor-associated enzymes, and preferentially activates inside tumors, where it expands antigen-specific CD8 T cells. This significantly reduces IL-2 toxicity and mortality without compromising antitumor efficacy. ProIL2 also overcomes resistance of cancers to immune checkpoint blockade. Lastly, neoadjuvant ProIL2 treatment can eliminate metastatic cancer through an abscopal effect. Taken together, our approach presents an effective tumor targeting therapy with reduced toxicity.

Export of lactic acid from glycolytic cancer cells to the extracellular tumor milieu has been reported to enhance tumor growth and suppress antitumor immunity. In this study, a pH‐activatable nanodrug is reported for tumor‐targeted inhibition of monocarboxylate transporter‐1 (MCT1) that reverses lactic acid‐induced tumor immunosuppression. The nanodrug is composed of an MCT1 inhibitor (AZD3965) loaded inside the ultra‐pH‐sensitive nanoparticles (AZD‐UPS NPs). AZD‐UPS NP is produced by a microfluidics method with improved drug loading efficiency and optimal nanoparticle size over sonication methods. The nanodrug remains as intact micelles at pH 7.4 but rapidly disassembles and releases payload upon exposure to acidic pH. When combined with anti‐PD‐1 therapy, AZD‐UPS NP leads to potent tumor growth inhibition and increases survival in two tumor models over oral administration of AZD3965 at dramatically reduced dose (>200‐fold). Safety evaluations demonstrate reduced drug distribution in heart and liver tissues with decrease in toxic biomarkers such as cardiac troponin by the nanodrug. Increased T‐cell infiltration and reduced exhaustive PD1⁺Tim3⁺ T cells are found in tumors. These data illustrate that tumor‐targeted inhibition of MCT1 can reverse the immune suppressive microenvironment of solid tumors for increased safety and antitumor efficacy of cancer immunotherapy.

PD-1 signaling on T cells is the major pathway that limits T cell immunity, but the efficacy of anti–PD-1 therapy has been limited to a small proportion of patients with advanced cancers. We fortuitously observed that anti–PD-1 therapy depends on IL-2 signaling, which raises the possibility that a lack of IL-2 limits anti–PD-1–induced effector T cell expansion. To selectively deliver IL-2 to PD-1⁺CD8⁺ tumor-infiltrating lymphocytes (TILs), we engineered a low-affinity IL-2 paired with anti–PD-1 (PD-1–laIL-2), which reduced affinity to peripheral Treg cells but enhanced avidity to PD-1⁺CD8⁺ TILs. PD-1–laIL-2 exerted better tumor control and lower toxicity than single or mixed treatments. Mechanistically, PD-1–laIL-2 could effectively expand dysfunctional and tumor-specific CD8⁺ T cells. Furthermore, we discovered that presumably dysfunctional PD-1⁺TIM3⁺ TILs are the dominant tumor-specific T cells responding to PD-1–laIL-2. Collectively, these results highlight that PD-1–laIL-2 can target and reactivate tumor-specific TILs for tumor regression as a unique strategy with stronger efficacy and lower toxicity.