Format

Send to

Choose Destination
J Proteome Res. 2020 Apr 3;19(4):1684-1695. doi: 10.1021/acs.jproteome.9b00846. Epub 2020 Mar 10.

Identification of ALDH6A1 as a Potential Molecular Signature in Hepatocellular Carcinoma via Quantitative Profiling of the Mitochondrial Proteome.

Author information

1
Yonsei Proteome Research Center, Yonsei University, Seoul 03722, Republic of Korea.
2
Interdisciplinary Program of Integrated OMICS for Biomedical Science, Graduate School, Yonsei University, Seoul 03722, Republic of Korea.
3
Department of Surgery and Department of Pathology, Yonsei University College of Medicine, Seoul 03722, Republic of Korea.
4
Department of Pathology, College of Medicine, Severance Hospital, Yonsei University, Seoul 03722, Republic of Korea.

Abstract

Various liver diseases, including hepatocellular carcinoma (HCC), have been linked to mitochondrial dysfunction, reduction of reactive oxygen species (ROS), and elevation of nitric oxide (NO). In this study, we subjected the human liver mitochondrial proteome to extensive quantitative proteomic profiling analysis and molecular characterization to identify potential signatures indicative of cancer cell growth and progression. Sequential proteomic analysis identified 2452 mitochondrial proteins, of which 1464 and 2010 were classified as nontumor and tumor (HCC) mitochondrial proteins, respectively, with 1022 overlaps. Further metabolic mapping of the HCC mitochondrial proteins narrowed our biological characterization to four proteins, namely, ALDH4A1, LRPPRC, ATP5C1, and ALDH6A1. The latter protein, a mitochondrial methylmalonate semialdehyde dehydrogenase (ALDH6A1), was most strongly suppressed in HCC tumor regions (∼10-fold decrease) in contrast to LRPPRC (∼6-fold increase) and was predicted to be present in plasma. Accordingly, we selected ALDH6A1 for functional analysis and engineered Hep3B cells to overexpress this protein, called ALDH6A1-O/E cells. Since ALDH6A1 is predicted to be involved in mitochondrial respiration, we assessed changes in the levels of NO and ROS in the overexpressed cell lines. Surprisingly, in ALDH6A1-O/E cells, NO was decreased nearly 50% but ROS was increased at a similar level, while the former was restored by treatment with S-nitroso-N-acetyl-penicillamine. The lactate levels were also decreased relative to control cells. Propidium iodide and Rhodamine-123 staining suggested that the decrease in NO and increase in ROS in ALDH6A1-O/E cells could be caused by depolarization of the mitochondrial membrane potential (ΔΨ). Taken together, our results suggest that hepatic neoplastic transformation appears to suppress the expression of ALDH6A1, which is accompanied by a respective increase and decrease in NO and ROS in cancer cells. Given the close link between ALDH6A1 suppression and abnormal cancer cell growth, this protein may serve as a potential molecular signature or biomarker of hepatocarcinogenesis and treatment responses.

KEYWORDS:

ALDH6A1; hepatocellular carcinoma; mitochondria; nitric oxide; reactive oxygen species

Supplemental Content

Full text links

Icon for American Chemical Society
Loading ...
Support Center