Monocarboxylate transporter 4 expression is a prognostic factor for radiotherapy outcome in squamous cell carcinoma of the head and neck.

Abstract Background: Hypoxia contributes significantly to tumor progression and resistance to radiotherapy, decreasing local tumor control and lowering the rates of disease-free and overall survival. Hypoxic tumor cells utilize the glycolytic pathway for survival, producing vast quantities of lactate. Monocarboxylate Transporters (MCTs) 1 and 4 are key transporters of lactate, enabling sustained high glycolytic rates and maintenance of intra-cellular pH. Aim: To carry out the first study evaluating tumor MCT1 and 4 expression as potential biomarkers of prognosis in patients with head and neck squamous cell carcinoma (HNSCC) undergoing radiotherapy, and to determine the impact of MCT expression on radiation resistance. Methods: 125 histologically confirmed SCC pre-treatment diagnostic oropharyngeal cancer biopsies (tonsil or posterior third of the tongue) were collected retrospectively from diagnostic archives. The biopsies were analyzed immunohistochemically to evaluate MCT1 and 4 membrane expression. MCT expression was assessed in a double blind manner using a semi-quantitative scoring system. Scores were analyzed for possible correlations with clinicopathological data relating to outcome 5 years post diagnosis, where all patients had received radiotherapy to the primary site. FaDu HNSCC cells expressing doxycycline inducible shRNA targeting MCT4 were used to evaluate radiosensitivity of wild-type and MCT4-knockdown cells. Results: A univariate analysis comparing high (top 25% of scores) vs low MCT expression (lower 75%) showed that MCT4, but not MCT1, is a significant adverse prognostic factor for radiotherapy outcome. High MCT4 expression correlates with poor loco-regional control (p = 0.017), reduced cancer-specific survival (p = 0.02) and reduced overall survival (p = 0.055). In a multivariate analysis high MCT4 expression retained prognostic significance for poor loco-regional control (p = 0.007). Confirmation of MCT4 as a novel target for increasing hypoxic radiosensitivity was carried out by clonogenic assay in FaDu wild-type and shMCT4 cell lines, MCT4-knockdown cells showed a marked increase in hypoxic radiosensitivity compared to wild-type cells. Conclusions: The increase in significance from overall survival to loco-regional control is consistent with a hypoxia-regulated marker of radiotherapy resistance. The functional role of MCT4 as a lactate transporter in hypoxia may be of key underlying biological importance to this finding, maintaining intracellular pH in a hypoxic microenvironment. These findings suggest that inhibition of MCT4 may modify hypoxic tumor regions and sensitize tumor cells to radiation treatment. Therefore, MCT4 should be explored further as a novel target and biomarker for prognosis and prediction of benefit from hypoxia-modifying therapy in patients undergoing radiotherapy. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 4123. doi:10.1158/1538-7445.AM2011-4123</jats:p

Rational identification of a colorectal cancer targeting peptide through phage display

Colorectal cancer is frequently diagnosed at an advanced stage due to the absence of early clinical indicators. Hence, the identification of new targeting molecules is crucial for an early detection and development of targeted therapies. This study aimed to identify and characterize novel peptides specific for the colorectal cancer cell line RKO using a phage-displayed peptide library. After four rounds of selection plus a negative step with normal colorectal cells, CCD-841-CoN, there was an obvious phage enrichment that specifically bound to RKO cells. Cell-based enzyme-linked immunosorbent assay (ELISA) was performed to assess the most specific peptides leading to the selection of the peptide sequence CPKSNNGVC. Through fluorescence microscopy and cytometry, the synthetic peptide RKOpep was shown to specifically bind to RKO cells, as well as to other human colorectal cancer cells including Caco-2, HCT 116 and HCT-15, but not to the normal non-cancer cells. Moreover, it was shown that RKOpep specifically targeted human colorectal cancer cell tissues. A bioinformatics analysis suggested that the RKOpep targets the monocarboxylate transporter 1, which has been implicated in colorectal cancer progression and prognosis, proven through gene knockdown approaches and shown by immunocytochemistry co-localization studies. The peptide herein identified can be a potential candidate for targeted therapies for colorectal cancer.Portuguese Foundation for Science and Technology (FCT) under the scope of the strategic funding of UID/BIO/04469/2019 unit and BioTecNorte operation (NORTE-01-0145-FEDER-000004) funded by the European Regional Development Fund under the scope of Norte2020 - Programa Operacional Regional do Norte and the Project FCOMP-01–0124-FEDER-021053 (PTDC/SAU-BMA/121028/2010). Débora Ferreira is recipient of a fellowship supported by a doctoral advanced training (call NORTE-69-2015-15) funded by the European Social Fund under the scope of Norte2020 - Programa Operacional Regional do Norte. Franklin L. Nobrega, Sara Granja and Ligia R Rodrigues acknowledge FCT for the grants SFRH/BD/86462/2012, SFRH/BPD/117858/2016 and SFRH/BSAB/142991/2018, respectively. Catarina Barbosa-Matos also acknowledge her research grant UMINHO/BI/395/2018info:eu-repo/semantics/publishedVersio

The metabolic fate of acetate in cancer

Recent high-profile reports have reignited an interest in acetate metabolism in cancer. Acetyl-CoA synthetases that catalyse the conversion of acetate to acetyl-CoA have now been implicated in the growth of hepatocellular carcinoma, glioblastoma, breast cancer and prostate cancer. In this Review, we discuss how acetate functions as a nutritional source for tumours and as a regulator of cancer cell stress, and how preventing its (re)capture by cancer cells may provide an opportunity for therapeutic intervention

Tumour acidosis: from the passenger to the driver's seat.

The high metabolic demand of cancer cells leads to an accumulation of H(+) ions in the tumour microenvironment. The disorganized tumour vasculature prevents an efficient wash-out of H(+) ions released into the extracellular medium but also favours the development of tumour hypoxic regions associated with a shift towards glycolytic metabolism. Under hypoxia, the final balance of glycolysis, including breakdown of generated ATP, is the production of lactate and a stoichiometric amount of H(+) ions. Another major source of H(+) ions results from hydration of CO2 produced in the more oxidative tumour areas. All of these events occur at high rates in tumours to fulfil bioenergetic and biosynthetic needs. This Review summarizes the current understanding of how H(+)-generating metabolic processes segregate within tumours according to the distance from blood vessels and inversely how ambient acidosis influences tumour metabolism, reducing glycolysis while promoting mitochondrial activity. The Review also presents novel insights supporting the participation of acidosis in cancer progression via stimulation of autophagy and immunosuppression. Finally, recent advances in the different therapeutic modalities aiming to either block pH-regulatory systems or exploit acidosis will be discussed