Comparison of Pre- and Post-translational Expressions of COXIV-1 and MT-ATPase 6 Genes in Colorectal Adenoma-Carcinoma Tissues [NIH-NIGMS]

Abstract

Objective: Colorectal cancer (CRC) develops from precancerous adenomatous polyps to malignant lesions of adenocarcinoma. Elucidating inhibition mechanisms for this route in patients with a risk of developing CRC is highly important for a potential diagnostic or prognostic marker. Differential expression of nuclear-encoded cytochrome c oxidase subunit 4 (COXIV) seems to contribute to a more unregulated respiration due to loss of ATP inhibition. Majority of energy for tumor transformations are mitochondrial origin. Differences in mitochondrial efficiency may be reflected in the progression of colorectal adenomatous polyps to adenocarcinomas. Here, we evaluate expression levels of COXIV isoform 1 (COXIV-1) and Mitochondrial (MT)-ATP synthase Subunit 6 (ATPase6) in adenomas of tubular, tubulovillous and villous tissues as compared to adenocarcinoma tissues. Method: Both RT-qPCR and western blot techniques were used to assess COXIV-1 and ATPase6 expression levels in 42 pairs of patients’ tissue samples. Protein carbonyl assay was performed to determine levels of oxidized proteins, as a measurement of ROS productions, in the tissue samples. Results: Differential RNA expression levels of COXIV-1 and ATPase6 from whole tissues were observed. Interestingly, RNA expression levels obtained from mitochondrial for COXIV-1 were significantly decreased in tubulovillous, villous adenomas and adenocarcinoma, but not in the tubular-polyps. Moreover, mitochondrial ATPase6 RNA expression levels decreased progressively from adenopolyps to adenocarcinoma. In mitochondrial protein, expression levels of both genes progressively decreased with a three folds from adenomatous polyps to adenocarcinoma. Whilst the ATPase6 protein expression significantly decreased in adenocarcinoma compared to villous, conversely, the levels of oxidized carbonyl proteins were considerably increased from adenomatous polyps to adenocarcinoma. Conclusion: Our findings provide evidence that decreased mitochondrial protein expression of COXIV-1 and ATPase6 correlates with increased ROS production during colorectal adenomatous polyps’ progression, suggesting the pivotal role of COXIV-1 in energy metabolism of colorectal cells as they progress from polyps to carcinoma.

Differential Expression Profiles of Mitogenome Associated MicroRNAs Among Colorectal Adenomatous Polyps

“…Hence, elucidating the crosstalk mechanism between the nuclear and mitochondrial genome regarding the functional impacts of miRNAs in tumor progressive stages and possible ROS productions, (as shown in Figure 6), will pivotally aid in the clinicopathological characteristics of CRC. Our lab had reported a decreased in mitochondrial isolated COXIV-1 a nuclear encoded subunit of complex IV with the progressive stages of CRC adenomas [43]. This finding was strikingly important given the role of COXIV-1 in regulating of the mitochondrial encoded subunits of complexes IV and V, as well as regulation of oxidative phosphorylation.…”

The Role of Mitochondria Dysfunction in Inflammatory Bowel Diseases and Colorectal Cancer

“…In particular, higher levels of TFAM, COX-II, ND6 (NADH dehydrogenase subunit 6), and COX IV were detected in cancer in comparison to primary colon cells [ 62 ]. Similarly, a comparison of the mRNA levels of COX IV-1 and ATPase6 from patients with different stages of CRC have found that the decreased expression of COX IV-1 and ATPase6 correlates with increased ROS production during colorectal adenomatous polyp progression, thus pointing to the central role of COX IV-1 in the colorectal cell’s mitochondria energy production as they progress from polyps to carcinoma [ 63 ]. Other research has also confirmed higher and gender-specific expression of COX-II [ 64 ] and tumour grade-dependent of COX I [ 65 ].…”

Research Into the Functions of Mitochondria in Experiment

“…COX IV (Cytochrome c oxidase subunit 4)белок, который является одной из полипептидных цепей цитохромоксидазы, участвует в переносе электронов в митохондриях. Принадлежит к семейству оксидазы IV цитохрома c. Характеризует эффективность цепи тканевого дыхания [19,31].…”