Tumor Metabolism in the Microenvironment of Nodal Metastasis in Oral Squamous Cell Carcinoma

Prognostic and predictive value of monocarboxylate transporter 4 in patients with breast cancer

The Warburg effect explains the large amount of lactic acid that tumour cells produce to establish and maintain the acidic characteristics of the tumour microenvironment, which contributes to the migration, invasion and angiogenesis of tumour cells. Monocarboxylate transporter 4 (MCT-4) is a key marker of tumour glycolysis and lactic acid production; however, the role of MCT-4 in breast cancer remains unclear. In the present study, immunohistochemistry (IHC) was used to detect the expression levels of MCT-4 in tissue microarrays of 145 patients diagnosed with invasive ductal breast cancer. The IHC score was used to assess the intensity of staining and the proportion of positive cells. Western blotting and reverse transcription-quantitative PCR were also performed to detect the expression levels of MCT-4 in 30 pairs of breast cancer tissues and adjacent normal tissues. In vitro experiments (EdU incoporation and Cell Counting Kit-8) were performed to examine the role of MCT-4 in the breast cancer MCF-7 cell line. The results of the present study indicated that high MCT-4 expression was associated with pT status (P=0.018), oestrogen receptor (ER) status (P=0.001), progesterone receptor (PR) status (P=0.024), Ki67 index (P=0.043) and androgen receptor (AR) status (P=0.033). In addition, an association between MCT-4 expression and pathological grade was observed (P=0.030). Furthermore, univariate (P=0.027) and multivariate (P=0.001) survival analysis revealed that MCT-4 expression and lymph node involvement were significant independent predictors of breast cancer prognosis. In addition, silencing MCT-4 expression attenuated breast cancer cell viability. Therefore, MCT-4 may be used as a potential predictor of invasive breast cancer.

Nuclear Magnetic Resonance Metabolomics Biomarkers for Identifying High Risk Patients with Extranodal Extension in Oral Squamous Cell Carcinoma

Extranodal extension (ENE) is an independent adverse prognostic factor in oral squamous cell carcinoma (OSCC), and is difficult to identify preoperatively. We aimed to discover biomarkers for high risk patients with ENE. Tandem tissue, plasma, and urine samples of 110 patients with OSCC were investigated through 600-MHz nuclear magnetic resonance (NMR) metabolomics analysis. We found that the levels of creatine, creatine phosphate, glycine, and tyramine in plasma significantly decreased in stage IV ENE positive OSCC compared with stage IV ENE negative OSCC. To understand the underlying mechanism behind the alteration of plasma metabolites, our tissue analysis revealed that the carnitine level significantly increased in tumors but significantly decreased in the adjacent normal tissue in advanced stage OSCC, in addition to decreased levels of alanine and pyruvate in tumor tissues. The global metabolomics analysis on tumor tissues also showed that stage IV tumors with an ENE positive status demonstrated higher levels of aspartate, butyrate, carnitine, glutamate, glutathione, glycine, glycolate, guanosine, and sucrose but lower levels of alanine, choline, glucose, isoleucine, lactate, leucine, myo-inositol, O-acetylcholine, oxypurinol, phenylalanine, pyruvate, succinate, tyrosine, valine, and xanthine than tumors with an ENE negative status. We concluded that metabolomics alterations in tumor tissues correspond to an increase in the tumor stage and are detectable in plasma samples. Metabolomic alterations of OSCC can serve as potential diagnostic markers and predictors of ENE in patients with stage IV OSCC.

Targeting Cellular Metabolism Modulates Head and Neck Oncogenesis

Considering the great energy and biomass demand for cell survival, cancer cells exhibit unique metabolic signatures compared to normal cells. Head and neck squamous cell carcinoma (HNSCC) is one of the most prevalent neoplasms worldwide. Recent findings have shown that environmental challenges, as well as intrinsic metabolic manipulations, could modulate HNSCC experimentally and serve as clinic prognostic indicators, suggesting that a better understanding of dynamic metabolic changes during HNSCC development could be of great benefit for developing adjuvant anti-cancer schemes other than conventional therapies. However, the following questions are still poorly understood: (i) how does metabolic reprogramming occur during HNSCC development? (ii) how does the tumorous milieu contribute to HNSCC tumourigenesis? and (iii) at the molecular level, how do various metabolic cues interact with each other to control the oncogenicity and therapeutic sensitivity of HNSCC? In this review article, the regulatory roles of different metabolic pathways in HNSCC and its microenvironment in controlling the malignancy are therefore discussed in the hope of providing a systemic overview regarding what we knew and how cancer metabolism could be translated for the development of anti-cancer therapeutic reagents.

Monocarboxylate transporters in cancer

Background

Tumors are highly plastic metabolic entities composed of cancer and host cells that can adopt different metabolic phenotypes. For energy production, cancer cells may use 4 main fuels that are shuttled in 5 different metabolic pathways. Glucose fuels glycolysis that can be coupled to the tricarboxylic acid (TCA) cycle and oxidative phosphorylation (OXPHOS) in oxidative cancer cells or to lactic fermentation in proliferating and in hypoxic cancer cells. Lipids fuel lipolysis, glutamine fuels glutaminolysis, and lactate fuels the oxidative pathway of lactate, all of which are coupled to the TCA cycle and OXPHOS for energy production. This review focuses on the latter metabolic pathway.

Scope of review

Lactate, which is prominently produced by glycolytic cells in tumors, was only recently recognized as a major fuel for oxidative cancer cells and as a signaling agent. Its exchanges across membranes are gated by monocarboxylate transporters MCT1-4. This review summarizes the current knowledge about MCT structure, regulation and functions in cancer, with a specific focus on lactate metabolism, lactate-induced angiogenesis and MCT-dependent cancer metastasis. It also describes lactate signaling via cell surface lactate receptor GPR81.

Major conclusions

Lactate and MCTs, especially MCT1 and MCT4, are important contributors to tumor aggressiveness. Analyses of MCT-deficient (MCT^+/- and MCT^−/-) animals and (MCT-mutated) humans indicate that they are druggable, with MCT1 inhibitors being in advanced development phase and MCT4 inhibitors still in the discovery phase. Imaging lactate fluxes non-invasively using a lactate tracer for positron emission tomography would further help to identify responders to the treatments.

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In cancer, hypoxia and cell proliferation are associated to lactic acid production.

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Lactate exchanges are at the core of tumor metabolism.

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Transmembrane lactate trafficking depends on monocarboxylate transporters (MCTs).

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MCTs are implicated in tumor development and aggressiveness.

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Targeting MCTs is a therapeutic option for cancer treatment.

Cigarette Smoke Induces Metabolic Reprogramming of the Tumor Stroma in Head and Neck Squamous Cell Carcinoma

Head and neck squamous cell carcinoma (HNSCC) is comprised of metabolically linked distinct compartments. Cancer-associated fibroblasts (CAF) and nonproliferative carcinoma cells display a glycolytic metabolism, while proliferative carcinoma cells rely on mitochondrial oxidative metabolism fueled by the catabolites provided by the adjacent CAFs. Metabolic coupling between these reprogrammed compartments contributes to HNSCC aggressiveness. In this study, we examined the effects of cigarette smoke-exposed CAFs on metabolic coupling and tumor aggressiveness of HNSCC. Cigarette smoke (CS) extract was generated by dissolving cigarette smoke in growth media. Fibroblasts were cultured in CS or control media. HNSCC cells were cocultured in vitro and coinjected in vivo with CS or control fibroblasts. We found that CS induced oxidative stress, glycolytic flux and MCT4 expression, and senescence in fibroblasts. MCT4 upregulation was critical for fibroblast viability under CS conditions. The effects of CS on fibroblasts were abrogated by antioxidant treatment. Coculture of carcinoma cells with CS fibroblasts induced metabolic coupling with upregulation of the marker of glycolysis MCT4 in fibroblasts and markers of mitochondrial metabolism MCT1 and TOMM20 in carcinoma cells. CS fibroblasts increased CCL2 expression and macrophage migration. Coculture with CS fibroblasts also increased two features of carcinoma cell aggressiveness: resistance to cell death and enhanced cell migration. Coinjection of carcinoma cells with CS fibroblasts generated larger tumors with reduced apoptosis than control coinjections, and upregulation of MCT4 by CS exposure was a driver of these effects. We demonstrate that a tumor microenvironment exposed to CS is sufficient to modulate metabolism and cancer aggressiveness in HNSCC. IMPLICATIONS: CS shifts cancer stroma toward glycolysis and induces head and neck cancer aggressiveness with a mitochondrial profile linked by catabolite transporters and oxidative stress. VISUAL OVERVIEW: http://mcr.aacrjournals.org/content/molcanres/17/9/1893/F1.large.jpg.

Loss of CD169+ Subcapsular Macrophages during Metastatic Spread of Head and Neck Squamous Cell Carcinoma

Objective

The purpose of this study is to assess CD169 expression in metastatic and nearby tumor-free lymph nodes of patients with head and neck squamous cell carcinoma (SCC).

Study Design

Retrospective analysis based on immunohistochemistry.

Setting

Tertiary care center.

Subjects and Methods

The abundance of CD169+ cells in the subcapsular sinuses (SCSs) of lymph nodes was assessed immunohistochemically in paraffin-embedded tissue samples derived from 22 patients with oral cavity and oropharyngeal SCC.

Results

SCSs of lymph nodes harboring metastatic SCC contained significantly fewer CD169+ macrophages (106.5 ± 113.6 cells/mm2) compared to nearby tumor-free lymph nodes (321.3 ± 173.4 cells/mm2, P < .001). This observation extended to 21 of the 22 cases investigated. In addition, 6 patients who later developed recurrent disease contained lower numbers of CD169+ cells (268.6 ± 169.5 cells/mm2) in nearby tumor-free lymph nodes compared to 341.0 ± 176.1 cells/mm2 in those who remained disease free ( P = .399). Human papillomavirus (HPV)–positive patients (n = 4) had a 6-fold lower number of CD169+ cells in metastatic nodes (61.2 ± 85.5 cells/mm2) compared to nearby tumor-free lymph nodes (369.5 ± 175.5 cells/mm2, P = .028). In comparison, HPV-negative patients had only a 3-fold reduction (116.6 ± 118.5 cells/mm2 vs 310.6 ± 176.2 cells/mm2, P < .001).

Conclusion

Metastatic spread of SCC to regional lymph nodes is associated with lower abundance of CD169+ macrophages in the SCSs of draining lymph nodes. These results set the stage for an in-depth investigation into the mechanism(s) by which metastatic SCC controls CD169+ macrophage abundance and its significance as it relates to prognosis and treatment response.

Metformin Clinical Trial in HPV+ and HPV- Head and Neck Squamous Cell Carcinoma: Impact on Cancer Cell Apoptosis and Immune Infiltrate

Background: Metformin, an oral anti-hyperglycemic drug which inhibits mitochondrial complex I and oxidative phosphorylation has been reported to correlate with improved outcomes in head and neck squamous cell carcinoma (HNSCC) and other cancers. This effect is postulated to occur through disruption of tumor-driven metabolic and immune dysregulation in the tumor microenvironment (TME). We report new findings on the impact of metformin on the tumor and immune elements of the TME from a clinical trial of metformin in HNSCC.

Methods: Human papilloma virus—(HPV–) tobacco+ mucosal HNSCC samples (n = 12) were compared to HPV+ oropharyngeal squamous cell carcinoma (OPSCC) samples (n = 17) from patients enrolled in a clinical trial. Apoptosis in tumor samples pre- and post-treatment with metformin was compared by deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) assay. Metastatic lymph nodes with extra-capsular extension (ECE) in metformin-treated patients (n = 7) were compared to archival lymph node samples with ECE (n = 11) for differences in immune markers quantified by digital image analysis using co-localization and nuclear algorithms (PD-L1, FoxP3, CD163, CD8).

Results: HPV–, tobacco + HNSCC (mean Δ 13.7/high power field) specimens had a significantly higher increase in apoptosis compared to HPV+ OPSCC specimens (mean Δ 5.7/high power field) (p < 0.001). Analysis of the stroma at the invasive front in ECE nodal specimens from both HPV—HNSCC and HPV+ OPSCC metformin treated specimens showed increased CD8+ effector T cell infiltrate (mean 22.8%) compared to archival specimens (mean 10.7%) (p = 0.006). Similarly, metformin treated specimens showed an increased FoxP3+ regulatory T cell infiltrate (mean 9%) compared to non-treated archival specimens (mean 5%) (p = 0.019).

Conclusions: This study presents novel data demonstrating that metformin differentially impacts HNSCC subtypes with greater apoptosis in HPV—HNSCC compared to HPV+ OPSCC. Moreover, we present the first in vivo human evidence that metformin may also trigger increased CD8+ Teff and FoxP3+ Tregs in the TME, suggesting an immunomodulatory effect in HNSCC. Further research is necessary to assess the effect of metformin on the TME of HNSCC.

Downregulation of MCT4 for lactate exchange promotes the cytotoxicity of NK cells in breast carcinoma

Monocarboxylate transporter‐4 (MCT4), a monocarboxylic acid transporter, demonstrates significantly increased expression in the majority of malignancies. We performed an experiment using BALB/C mice, and our results showed that ShMCT4 transfection or the pharmaceutic inhibition of MCT4 with 7acc1 strengthens the activity of NK cells. The results of a calcein assay revealed that the cytotoxicity of NK cells was strengthened via inhibition of MCT4. In addition, ELISA testing showed that the content of perforin and CD107a was increased, and PCR amplification and immunoblotting revealed that the expression of NKG2D and H60 was upregulated after the inhibition of MCT4. Further, we observed an elevated pH value, decreased extracellular lactate flow, and attenuated tumor growth. Therefore, we concluded that the inhibition of MCT4 enhanced the cytotoxicity of NK cells by blocking lactate flux and reversing the acidified tumor microenvironment. In addition to these findings, we also discovered that MCT4 depletion may have a pronounced impact on autophagy, which was surmised by observing that the inhibition of autophagy (3MA) pulled the enhanced cytotoxicity of NK cells downwards. Together, these data suggest that the key effect of MCT4 depletion on NK cells probably utilizes inductive autophagy as a compensatory metabolic mechanism to minimize the acidic extracellular microenvironment associated with lactate export in tumors.