MCT4 blockade increases the efficacy of immune checkpoint blockade

The Solute Carrier (SLC) Transporter Superfamily as Therapeutic Targets for the Treatment of Head and Neck Squamous Cell Carcinoma

Background: Head and neck squamous cell carcinoma (HNSC) is the most prevalent cancer in the head and neck region, originating from the mucosal epithelium of the oral cavity, pharynx, and larynx. The solute carrier (SLC) transporter superfamily, consisting of over 400 proteins across 65 families, plays a crucial role in cellular functions and presents promising targets in precision oncology. This study aims to analyze the expression of SLC transporters in HNSC and their potential as biomarkers and therapeutic targets. Methods: We leveraged mRNA and protein expression data from The Cancer Genome Atlas (TCGA) and The Human Protein Atlas (HPA) to examine SLC transporter expression in HNSC. Gene Set Enrichment Analysis (GSEA) was conducted to assess the involvement of SLC transporters in various oncogenic pathways. Results: Significant upregulation of SLC transporters was observed in tumor tissues compared to normal tissues, with notable increases in SLC16A3, SLC53A1, SLC25A32, and SLC2A3. This upregulation correlated with poorer overall survival (OS) and disease-specific survival (DSS). GSEA revealed that these transporters are significantly involved in critical oncogenic pathways, including epithelial-mesenchymal transition (EMT), angiogenesis, and hypoxia, which are vital for cancer progression and metastasis. Conclusions: The study identifies SLC transporters as potential biomarkers and therapeutic targets in HNSC. Targeting these transporters with small molecule inhibitors could disrupt essential supply routes for cancer cells, enhancing treatment efficacy and improving patient outcomes. This study paves the way for developing SLC-based target therapies in precision oncology, with the goal of improving survival rates for patients with HNSC.

MCT4 is an independent prognostic factor and affects immune cell infiltration in patients with colorectal liver oligometastases

BACKGROUND

Monocarboxylate transporter 4 (MCT4) is a novel biomarker related to the level of immune cell infiltration, but its impact on tumor immune microenvironment (TIME) of colorectal liver oligometastases (CLO) remains unclear. The aim of this study was to assess MCT4 expression in primary tumor and liver oligometastases, investigate its impact on immune cell infiltration and its prognostic value for CLO patients undergoing liver resection.

METHODS

We retrospectively selected 135 CLO patients who underwent curative liver resection between June 1999 and December 2016, and samples included 74 primary tumor tissues and 122 liver metastases. Immunohistochemistry (IHC) was performed to detect MCT4 expression in paraffin-embedded specimens and tyramine signal amplification (TSA) was used to detect the density of tumor-infiltrating lymphocytes, including CD3 + , CD8 + and Foxp3 + . Recurrence-free survival (RFS) and overall survival (OS) were analyzed using the Kaplan-Meier method and log-rank test, and independent prognostic factors were identified with Cox regression modeling.

RESULTS

Survival analysis indicated that CLO patients with low MCT4 expression had better 3-year RFS and 3-year OS rates than those with high MCT4 expression. Multivariate analysis indicated that high MCT4 expression was independently associated with poor RFS and OS. High MCT4 expression was associated with a lower number of intratumoral CD3 + /CD8 + T cells and was associated with higher Foxp3 + T cells infiltration. Patients with low MCT4 expression and high levels of differential immune infiltration had longer survival.

CONCLUSIONS

MCT4 overexpression was associated with an unfavorable prognosis in patients with CLO and MCT4 expression level had an impact on intratumoral immune infiltration degree. A novel parameter that combined MCT4 expression level and differential immune infiltration level was constructed to stratify patients with CLO into different risk groups.

Cancer cell metabolism and antitumour immunity

Accumulating evidence suggests that metabolic rewiring in malignant cells supports tumour progression not only by providing cancer cells with increased proliferative potential and an improved ability to adapt to adverse microenvironmental conditions but also by favouring the evasion of natural and therapy-driven antitumour immune responses. Here, we review cancer cell-intrinsic and cancer cell-extrinsic mechanisms through which alterations of metabolism in malignant cells interfere with innate and adaptive immune functions in support of accelerated disease progression. Further, we discuss the potential of targeting such alterations to enhance anticancer immunity for therapeutic purposes.

Targeting metabolic pathways to counter cancer immunotherapy resistance

Immunotherapies have revolutionized the treatment of certain cancers, but challenges remain in overcoming immunotherapy resistance. Research shows that metabolic modulation of the tumor microenvironment can enhance antitumor immunity. Here, we discuss recent preclinical and clinical evidence for the efficacy of combining metabolic modifiers with immunotherapies. While this combination holds great promise, a few key areas must be addressed, which include identifying the effects of metabolic modifiers on immune cell metabolism, the putative biomarkers of therapeutic efficacy, the efficacy of modifiers on tumors harboring metabolic heterogeneity, and the potential development of resistance due to tumor reliance on alternative metabolic pathways. We propose solutions to these problems and posit that assessing these parameters is crucial for considering the potential of metabolic modifiers in sensitizing tumors to immunotherapies.

A review of lactate-lactylation in malignancy: its potential in immunotherapy

Lactic acid was formerly regarded as a byproduct of metabolism. However, extensive investigations into the intricacies of cancer development have revealed its significant contributions to tumor growth, migration, and invasion. Post-translational modifications involving lactate have been widely observed in histone and non-histone proteins, and these modifications play a crucial role in regulating gene expression by covalently attaching lactoyl groups to lysine residues in proteins. This discovery has greatly enhanced our comprehension of lactic acid's involvement in disease pathogenesis. In this article, we provide a comprehensive review of the intricate relationship between lactate and tumor immunity, the occurrence of lactylation in malignant tumors, and the exploitation of targeted lactate-lactylation in tumor immunotherapy. Additionally, we discuss future research directions, aiming to offer novel insights that could inform the investigation, diagnosis, and treatment of related diseases.

Targeting tumor-intrinsic SLC16A3 to enhance anti-PD-1 efficacy via tumor immune microenvironment reprogramming

Immunotherapy, especially immune checkpoint inhibitors, has revolutionized clinical practice within the last decade. However, primary and secondary resistance to immunotherapy is common in patients with diverse types of cancer. It is well-acknowledged that tumor cells can facilitate the formation of immunosuppressive microenvironments via metabolism reprogramming, and lactic acid, the metabolite of glycolysis, is a significant contributor. SLC16A3 (also named as MCT4) is a transporter mediating lactic acid efflux. In this study, we investigated the role of glycolysis in immunotherapy resistance and aimed to improve the immunotherapy effects via Slc16a3 inhibition. Bioinformatical analysis revealed that the expression of glycolysis-related genes correlated with less CD8+ T cell infiltration and increased myeloid-derived suppressor cells (MDSC) enrichment. We found that high glycolytic activity in tumor cells adversely affected the antitumor immune responses and efficacy of immunotherapy and radiotherapy. As the transporter of lactic acid, SLC16A3 is highly expressed in glycolytic B16-F10 (RRID: CVCL_0159) cells, as well as human non-small cell lung carcinoma. We validated that Slc16a3 expression in tumor cells negatively correlated with anti-PD-1 efficiency. Overexpression of Slc16a3 in tumor cells promoted lactic acid production and efflux, and reduced tumor response to anti-PD-1 inhibitors by inhibiting CD8+ T cell function. Genetic and pharmacological inhibition of Slc16a3 dramatically reduced the glycolytic activity and lactic acid production in tumor cells, and ameliorated the immunosuppressive tumor microenvironments (TMEs), leading to boosted antitumor effects via anti-PD-1 blockade. Our study therefore demonstrates that tumor cell-intrinsic SLC16A3 may be a potential target to reverse tumor resistance to immunotherapy.

Effect of metabolic reprogramming on the immune microenvironment in gastric cancer

Gastric cancer (GC) is a malignant tumor of the gastrointestinal tract with a high mortality rate worldwide, a low early detection rate and a poor prognosis. The rise of metabolomics has facilitated the early detection and treatment of GC. Metabolism in the GC tumor microenvironment (TME) mainly includes glucose metabolism, lipid metabolism and amino acid metabolism, which provide energy and nutrients for GC cell proliferation and migration. Abnormal tumor metabolism can influence tumor progression by regulating the functions of immune cells and immune molecules in the TME, thereby contributing to tumor immune escape. Thus, in this review, we summarize the impact of metabolism on the TME during GC progression. We also propose novel strategies to modulate antitumor immune responses by targeting metabolism.