Mitochondrial Respiration in KRAS and BRAF Mutated Colorectal Tumors and Polyps

Abstract

This study aimed to characterize the ATP-synthesis by oxidative phosphorylation in colorectal cancer (CRC) and premalignant colon polyps in relation to molecular biomarkers KRAS and BRAF. This prospective study included 48 patients. Resected colorectal polyps and postoperative CRC tissue with adjacent normal tissue (control) were collected. Patients with polyps and CRC were divided into three molecular groups: KRAS mutated, BRAF mutated and KRAS/BRAF wild-type. Mitochondrial respiration in permeabilized tissue samples was observed using high resolution respirometry. ADP-activated respiration rate (Vmax) and an apparent affinity of mitochondria to ADP, which is related to mitochondrial outer membrane (MOM) permeability, were determined. Clear differences were present between molecular groups. KRAS mutated CRC group had lower Vmax values compared to wild-type; however, the Vmax value was higher than in the control group, while MOM permeability did not change. This suggests that KRAS mutation status might be involved in acquiring oxidative phenotype. KRAS mutated polyps had higher Vmax values and elevated MOM permeability as compared to the control. BRAF mutated CRC and polyps had reduced respiration and altered MOM permeability, indicating a glycolytic phenotype. To conclude, prognostic biomarkers KRAS and BRAF are likely related to the metabolic phenotype in CRC and polyps. Assessment of the tumor mitochondrial ATP synthesis could be a potential component of patient risk stratification.

Energy Metabolic Plasticity of Colorectal Cancer Cells as a Determinant of Tumor Growth and Metastasis

“…Our recent studies revealed remarkable differences in the regulation of outer mitochondrial membrane (OMM) permeability between cultured tumor cells and clinical material from cancer patients ( 5 , 43 ). Comparative analysis of the biopsy or surgical cancer material and surrounding healthy tissue showed almost unchanged glycolytic activity and upregulation of OXPHOS in CRC, which is inconsistent with the data obtained by using cell culture ( 43 – 47 ). In addition, two widely used breast cancer cell lines MCF7 and MCF-MDA-231 failed to replicate mitochondrial function in respect to metabolic activity and OXPHOS as seen in respective human samples ( 43 , 46 ).…”

“…Determined in permeabilized cells and tissues, Km(ADP) is the affinity of the mitochondria for exogenous ADP and characterizes permeability of OMM for adenine nucleotides and, thus, VDAC permeability. Measured Km(ADP) values for human colon mucosa is ~110 µM ( 47 ), ~100 µM for CRC ( 5 , 44 , 47 ), ~60 µM for colon polyps ( 47 ), and ~40 µM for Caco2 CRC cell line ( 43 ), indicating the alteration of control mechanisms over VDAC permeability and OXPHOS during the progression of CRC. Thus, the regulation of OMM permeability to adenine nucleotides in cancer tissues is different from that in normal cells ( 5 , 67 , 68 ).…”

“…According to the model proposed by Saks V. et al, the proportion of mitochondria with low oxidative capacity in the tissue can be inferred from the Km(ADP) value ( 70 ). For example, the proportion of mitochondria with high oxidative capacity is 67% in CRC tumors and only 38% in colorectal polyps ( 47 ).…”

Targeting Altered Energy Metabolism in Colorectal Cancer: Oncogenic Reprogramming, the Central Role of the TCA Cycle and Therapeutic Opportunities

“…The mtDNA copy number was shown to be significantly lower in BRAF -mutated and microsatellite-instable (MSI) tumors and higher in KRAS -mutated tumors [ 37 ]. In accordance with this, the functional examination of the adenosine diphosphate (ADP)-activated respiration rate (Vmax) and the mitochondrial outer membrane (MOM) permeability in patient-derived KRAS -/ BRAF -mutated as well as wild-type tumor specimen indicates that KRAS mutations might be linked to an oxidative phenotype, while BRAF mutations to a glycolytic phenotype [ 38 ]. This observation may contradict the findings in another study that revealed the induction of glycolysis, the accumulation of lactic acid and the sensitivity to glycolytic inhibition in KRAS -mutated CRC cells, whereas BRAF -mutated CRC cells remained resistant towards the alterations of glucose supply or metabolic inhibitors [ 39 ].…”

Postdiagnostic metformin use and survival of patients with colorectal cancer: A Nationwide cohort study

“…Furthermore, the different subgroups of CRC by molecular types demonstrated distinct types of energy metabolism. In the BRAF or KRAS mutated tumors, metabolic reprogramming shifts from OXPHOS to a more glycolytic type [174].…”