Elevated lactate dehydrogenase A (LDHA) expression is associated with poor outcome in tumor patients. Here we show that LDHA-associated lactic acid accumulation in melanomas inhibits tumor surveillance by T and NK cells. In immunocompetent C57BL/6 mice, tumors with reduced lactic acid production (Ldha) developed significantly slower than control tumors and showed increased infiltration with IFN-γ-producing T and NK cells. However, in Rag2γc mice, lacking lymphocytes and NK cells, and in Ifng mice, Ldha and control cells formed tumors at similar rates. Pathophysiological concentrations of lactic acid prevented upregulation of nuclear factor of activated T cells (NFAT) in T and NK cells, resulting in diminished IFN-γ production. Database analyses revealed negative correlations between LDHA expression and T cell activation markers in human melanoma patients. Our results demonstrate that lactic acid is a potent inhibitor of function and survival of T and NK cells leading to tumor immune escape.

Cytotoxic T lymphocytes and NK cells play an important role in eliminating malignant tumor cells and the number and activity of tumor-infiltrating T cells represent a good marker for tumor prognosis. Based on these findings, immunotherapy, e.g., checkpoint blockade, has received considerable attention during the last couple of years. However, for the majority of patients, immune control of their tumors is gray theory as malignant cells use effective mechanisms to outsmart the immune system. Increasing evidence suggests that changes in tumor metabolism not only ensure an effective energy supply and generation of building blocks for tumor growth but also contribute to inhibition of the antitumor response. Immunosuppression in the tumor microenvironment is often based on the mutual metabolic requirements of immune cells and tumor cells. Cytotoxic T and NK cell activation leads to an increased demand for glucose and amino acids, a well-known feature shown by tumor cells. These close metabolic interdependencies result in metabolic competition, limiting the proliferation, and effector functions of tumor-specific immune cells. Moreover, not only nutrient restriction but also tumor-driven shifts in metabolite abundance and accumulation of metabolic waste products (e.g., lactate) lead to local immunosuppression, thereby facilitating tumor progression and metastasis. In this review, we describe the metabolic interplay between immune cells and tumor cells and discuss tumor cell metabolism as a target structure for cancer therapy. Metabolic (re)education of tumor cells is not only an approach to kill tumor cells directly but could overcome metabolic immunosuppression in the tumor microenvironment and thereby facilitate immunotherapy.

ABSTRACT:Macrolides may cause severe drug interactions due to the inhibition of metabolizing enzymes. Transporter-mediated uptake of drugs into cells [e.g., by members of the human organic anion transporting polypeptide (OATP) family] is a determinant of drug disposition and a prerequisite for subsequent metabolism. However whether macrolides are also inhibitors of uptake transporters, thereby providing an additional mechanism of drug interactions, has not been systematically studied. The human OATP family members OATP1B1 and OATP1B3 mediate the uptake of endogenous substances and drugs such as antibiotics and HMG-CoA reductase inhibitors (statins) into hepatocytes. In this study we investigated the potential role of these uptake transporters on macrolide-induced drug interactions. By using sulfobromophthalein (BSP) and the HMG-CoA reductase inhibitor pravastatin as substrates, the effects of the macrolides azithromycin, clarithromycin, erythromycin, and roxithromycin and of the ketolide telithromycin on the OATP1B1-and OATP1B3-mediated uptake were analyzed. These experiments demonstrated that the OATP1B1-and OATP1B3-mediated uptake of BSP and pravastatin can be inhibited by increasing concentrations of all macrolides except azithromycin. The IC 50 values for the inhibition of OATP1B3-mediated BSP uptake were 11 M for telithromycin, 32 M for clarithromycin, 34 M for erythromycin, and 37 M for roxithromycin. These IC 50 values were lower than the IC 50 values for inhibition of OATP1B1-mediated BSP uptake (96-217 M). These macrolides also inhibited in a concentration-dependent manner the OATP1B1-and OATP1B3-mediated uptake of pravastatin. In summary, these results indicate that alterations of uptake transporter function by certain macrolides/ketolides have to be considered as a potential additional mechanism underlying drug-drug interactions.Macrolide antibiotics (e.g., erythromycin and clarithromycin) can cause severe drug interactions by increasing plasma concentrations of simultaneously administered compounds. The major mechanism underlying these drug interactions is believed to be inhibition of the major drug metabolizing enzyme CYP3A4 in small intestine and liver (Wrington and Thummel, 2000;Ito et al., 2003;Polasek and Miners, 2006).Published data indicate that certain macrolides are also inhibitors of the apically/luminally localized drug efflux pump P-glycoprotein (Kim et al., 1999;Marzolini et al., 2004;Eberl et al., 2005). By inhibition of P-glycoprotein function they increase drug absorption from the gut lumen and decrease biliary elimination and renal secretion of concomitantly administered drugs such as the cardiac glycoside digoxin (Rengelshausen et al., 2003). This in turn leads to increased drug concentrations and drug toxicity.Newly recognized, additional determinants of drug disposition are uptake transporters of the OATP (SLCO) family (Hagenbuch and Meier, 2004;König et al., 2006). Members of the OATP family transport a wide range of drugs including HMG-CoA reductase inhibitors (cerivastatin, flu...

Highlights d Glycolytic index in melanoma negatively correlates with response to anti-PD1 therapy d Blocking lactate transport or knock out of glycolytic genes improves checkpoint therapy d Diclofenac blocks the lactate transporters MCT1 and MCT4 in a COX-independent manner d Inhibition of glycolysis by MCT blockade does not impede T cell function SUMMARY Tumor-derived lactic acid inhibits T and natural killer (NK) cell function and, thereby, tumor immunosurveillance.Here, we report that melanoma patients with high expression of glycolysis-related genes show a worse progression free survival upon anti-PD1 treatment. The non-steroidal anti-inflammatory drug (NSAID) diclofenac lowers lactate secretion of tumor cells and improves anti-PD1-induced T cell killing in vitro. Surprisingly, diclofenac, but not other NSAIDs, turns out to be a potent inhibitor of the lactate transporters monocarboxylate transporter 1 and 4 and diminishes lactate efflux. Notably, T cell activation, viability, and effector functions are preserved under diclofenac treatment and in a low glucose environment in vitro. Diclofenac, but not aspirin, delays tumor growth and improves the efficacy of checkpoint therapy in vivo. Moreover, genetic suppression of glycolysis in tumor cells strongly improves checkpoint therapy. These findings support the rationale for targeting glycolysis in patients with high glycolytic tumors together with checkpoint inhibitors in clinical trials.

Increased glucose consumption distinguishes cancer cells from normal cells and is known as the "Warburg effect" because of increased glycolysis. Lactate dehydrogenase A (LDHA) is a key glycolytic enzyme, a hallmark of aggressive cancers, and believed to be the major enzyme responsible for pyruvate-to-lactate conversion. To elucidate its role in tumor growth, we disrupted both the and genes in two cancer cell lines (human colon adenocarcinoma and murine melanoma cells). Surprisingly, neither nor knockout strongly reduced lactate secretion. In contrast, double knockout (-DKO) fully suppressed LDH activity and lactate secretion. Furthermore, under normoxia, -DKO cells survived the genetic block by shifting their metabolism to oxidative phosphorylation (OXPHOS), entailing a 2-fold reduction in proliferation rates and compared with their WT counterparts. Under hypoxia (1% oxygen), however, suppression completely abolished growth, consistent with the reliance on OXPHOS. Interestingly, activation of the respiratory capacity operated by the-DKO genetic block as well as the resilient growth were not consequences of long-term adaptation. They could be reproduced pharmacologically by treating WT cells with an LDHA/B-specific inhibitor (GNE-140). These findings demonstrate that the Warburg effect is not only based on high LDHA expression, as both and need to be deleted to suppress fermentative glycolysis. Finally, we demonstrate that the Warburg effect is dispensable even in aggressive tumors and that the metabolic shift to OXPHOS caused by / genetic disruptions is responsible for the tumors' escape and growth.

Many tumor cells are characterized by a dysregulated glucose metabolism associated with increased glycolysis in the presence of oxygen (''Warburg Effect''). Here, we analyzed for the first time a possible link between glucose metabolism and immune cell infiltration in renal cell carcinoma (RCC). RCC specimens revealed a highly significant increase in the expression of lactate dehydrogenase A (LDHA) and glucose-transporter 1 (GLUT-1) compared to the corresponding normal kidney tissue on mRNA level. Accordingly, tumor cell lines of different origin such as RCC, melanoma and hepatocellular carcinoma strongly expressed LDHA and GLUT-1 compared to their nonmalignant counterparts. In line with this finding, tumor cells secreted high amounts of lactate. High expression of GLUT-1 and LDH5, a tetramer of 4 LDHA subunits, was confirmed by tissue microarray analysis of 249 RCC specimens. Overall, 55/79 (69.6%) and 46/71 (64.7%) cases of clear cell carcinoma showed a constitutive, but heterogeneous expression of GLUT-1 and LDH5, respectively. The number of CD3 1 , CD8 1 and FOXP3 1 T cells was significantly elevated in RCC lesions compared to normal kidney epithelium, but effector molecules such as granzyme B and perforin were decreased in tumor infiltrating T cells. Of interest, further analysis revealed an inverse correlation between GLUT-1 expression and the number of CD8 1 T cells in RCC lesions. Together, our data suggest that an accelerated glucose metabolism in RCC tissue is associated with a low infiltration of CD8 1 effector T cells. Targeting the glucose metabolism may represent an interesting tool to improve the efficacy of specific immunotherapeutic approaches in RCC.Renal cell carcinoma (RCC) constitutes 2-3% of all malignant tumors in adults. It is a very heterogeneous malignancy, which is subdivided in different histological subtypes. The most common type of RCC is clear cell carcinoma with an incidence of 75% whereas the papillary (10-15%) and the chromophobe subtypes (5%) are less frequent. 1,2 Clear cell carcinoma arises from cells of the proximal tubule and is characterized by a clear cytoplasm, which stores glycogen. It is associated with a large number of gene mutations most notably in the von Hippel Lindau (VHL) gene. 3,4 The VHL protein is crucially involved in the regulation of the hypoxia inducible transcription factor HIF1. In the absence of VHL, HIF is stabilized and induces the expression of proteins that are involved in angiogenesis and glucose metabolism, e.g., vascular endothelial growth factor (VEGF), erythropoietin and glucose-transporter 1 (GLUT-1). 5,6 Overexpression of GLUT-1 has been described in different malignancies 7-9 and polymorphisms of GLUT-1 seems to be associated with clear cell carcinoma. 10 Beside HIF stabilization through loss of the tumor suppressor gene VHL or hypoxia, oncogenic transformation, caused by loss of p53, 11,12 mutation of KRAS/BRAF 13 or c-myc overexpression 14 reduces respiration accompanied by an upregulation of glycolytic enzymes such as lactate dehydrogena...

The strong link between T-cell metabolism and effector functions is well characterized in the murine system but hardly investigated in human T cells. Therefore, we analyzed glycolytic and mitochondrial activity in correlation to function in activated human CD4 and CD8 T cells. Glycolysis was barely detectable upon stimulation but accelerated beyond 24 h, whereas mitochondrial activity was elevated immediately in both T-cell populations. Glucose deprivation or mitochondrial restriction reduced proliferation, had only a transient impact on "on-blast formation" and no impact on viability, IFN-γ, IL-2, IL-4, and IL-10 production, whereas TNF was reduced. Similar results were obtained in bulk T cells and T-cell subsets. Elevated respiration under glucose restriction demonstrated metabolic flexibility. Administration of the glycolytic inhibitor 2-deoxy-glucose suppressed both glycolysis and respiration and exerted a strong impact on cytokine production that persisted for IFN-γ after removal of 2-deoxy-glucose. Taken together, glycolytic or mitochondrial restriction alone compromised proliferation of human T cells, but barely affected their effector functions. In contrast, effector functions were severely affected by 2-deoxy-glucose treatment.Keywords: 2-deoxy-glucose r ATP r Cytokines r Glucose deprivation r Human CD4 T cells r Human CD8 T cells r Metabolism r Mitochondrial inhibition See accompanying Commentary by FinlayAdditional supporting information may be found in the online version of this article at the publisher's web-site

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