Monocarboxylate Transporters 1 and 4 and MTCO1 in Gastric Cancer

Simple Summary

The expression of monocarboxylate transporters (MCTs) are reported in a variety of cancers and suggested as a therapeutic target for cancer treatment. However, previous study results in gastric cancer are contradictory. In this study, we evaluated the expression of MCT1, MCT4, and Mitochondrial cytochrome c oxidase (MTCO1) and their association with clinicopathological parameters and prognostic significance in a cohort of 568 surgically treated gastric cancer patients. The results suggest that monocarboxylate transporters and MTCO1 are associated with gastric cancer progression but have no independent prognostic relevance.

Abstract

Background: Monocarboxylate transporters (MCTs) appear to play an important role in tumor development and aggressiveness. The present study aimed to evaluate associations between cytoplasmic MCT1, MCT4, and mitochondrial cytochrome c oxidase (MTCO1) expression and clinicopathological variables or survival in gastric cancer. Material and methods: A total of 568 gastric adenocarcinoma patients were included in this retrospective cohort study. Protein expressions were detected by immunohistochemical staining. The patients were divided into low expression and high expression groups by median value. The Chi-squared test was used to compare categorical variables. The T-test was used to compare continuous variables. Expressions were analyzed in relation to 5-year survival and overall survival. Cox regression provided HRs and 95% CIs, adjusted for confounders. Results: High cytoplasmic MCT1 expression was associated statistically significantly with higher T-class (p = 0.020). High cytoplasmic MCT4 expression was associated statistically significantly with positive lymph node status (p = 0.005) and was more common in Lauren’s intestinal type (p < 0.001). Low cytoplasmic MTCO1 expression was associated statistically significantly with positive distant metastases (p = 0.030), and high cytoplasmic MTCO1 expression was associated more often with intestinal type (p = 0.044). However, MCT1, MCT4, and MTCO1 were not associated with survival. Conclusions: Monocarboxylate receptors seem to be associated with gastric cancer progression but have no independent prognostic relevance.

Intratumoral lactate metabolism in Barrett's esophagus and adenocarcinoma

Background

Monocarboxylate transporters (MCTs) are cell membrane proteins which transport pyruvate, lactate and ketone bodies across the plasma membrane. MCTs are activated in various cancers, but their expression in esophageal adenocarcinoma is not known. The present study was conducted to elucidate the expression of MCTs in esophageal adenocarcinoma and its precursor lesions.

Results

Cytoplasmic MCT1, MCT4 and MTCO1 expression linearly increased from normal epithelium to Barrett's mucosa to dysplasia and cancer. Low cytoplasmic MCT1 expression associated with high T-class (P < 0.01), positive lymph node metastases (P < 0.05), positive distant metastases (P < 0.01) and high tumor stage (P < 0.01). High cytoplasmic MCT4 expression correlated significantly with positive distant metastases (P < 0.05). Both low MCT1 and high MCT4 histoscore predicted survival in univariate analysis (P < 0.01). MCT4 histoscore predicted survival in multivariate analysis (P = 0.043; HR 1.8 95%CI 1.0–3.1). MTCO1 expression was not correlated to clinicopathological variables or survival.

Materials and Methods

MCT1, MCT4 and mitochondrial cytochrome c oxidase (MTCO1) expression were determined with immunohistochemistry in esophageal specimens from 129 patients with columnar dysplasia or adenocarcinoma. Specimens including normal esophagus (n = 88), gastric (n = 67) or intestinal metaplasia (n = 51), low-grade (n = 42), high-grade dysplasia (n = 37) and esophageal adenocarcinoma (n = 99) were evaluated.

Conclusions

Major increase in markers of tumor metabolism occurs during carcinogenesis and progression of esophageal adenocarcinoma. MCT1 and MCT4 are prognostic factors in esophageal adenocarcinoma.

Effect of leptin treatment on mitochondrial function in obese leptin-deficient ob/ob mice

OBJECTIVE

Leptin stimulates peripheral lipid oxidation, but the influence on mitochondrial function is partly unknown. We investigated tissue-specific mitochondrial function in leptin-deficient obese C57BL/6J-ob/ob mice compared to lean littermates following leptin treatment.

MATERIALS AND METHODS

Lean and obese ob/ob mice were treated with saline or leptin for 5 days. At day six, liver, extensor digitorum longus (EDL) and soleus muscle were dissected and mitochondrial respiration analyzed in freshly dissected tissues. Expression of key proteins in the regulation of mitochondrial function was determined.

RESULTS

In liver, mitochondrial respiration was reduced in ob/ob mice compared to lean mice. Expression of mitochondrial transcription factor A (TFAM) was decreased in ob/ob mice, but increased with leptin treatment. In glycolytic EDL muscle, mitochondrial respiration was increased in ob/ob mice. Protein markers of complex II, IV and ATP synthase were increased in EDL muscle from both saline- and leptin-treated ob/ob mice. TFAM protein abundance was decreased, while dynamin-1-like protein was increased in EDL muscle from saline-treated ob/ob mice and restored by leptin treatment. In oxidative soleus muscle, mitochondrial respiration and electron transport system protein abundance were unchanged, while TFAM was reduced in ob/ob mice.

CONCLUSIONS

In conclusion, leptin-deficient ob/ob mice display tissue-specific mitochondrial adaptations under basal conditions and in response to leptin treatment. Mitochondrial respiration was decreased in liver, increased in glycolytic muscle and unaltered in oxidative muscle from ob/ob mice. Insight into the tissue-specific regulation of mitochondrial function in response to energy supply and demand may provide new opportunities for the treatment of insulin resistance.