Evaluation of two mitochondrial DNA biomarkers for prostate cancer detection

The Uprising of Mitochondrial DNA Biomarker in Cancer

Cancer is a heterogeneous group of diseases, the progression of which demands an accumulation of genetic mutations and epigenetic alterations of the human nuclear genome or possibly in the mitochondrial genome as well. Despite modern diagnostic and therapeutic approaches to battle cancer, there are still serious concerns about the increase in death from cancer globally. Recently, a growing number of researchers have extensively focused on the burgeoning area of biomarkers development research, especially in noninvasive early cancer detection. Intergenomic cross talk has triggered researchers to expand their studies from nuclear genome-based cancer researches, shifting into the mitochondria-mediated associations with carcinogenesis. Thus, it leads to the discoveries of established and potential mitochondrial biomarkers with high specificity and sensitivity. The research field of mitochondrial DNA (mtDNA) biomarkers has the great potential to confer vast benefits for cancer therapeutics and patients in the future. This review seeks to summarize the comprehensive insights of nuclear genome cancer biomarkers and their usage in clinical practices, the intergenomic cross talk researches that linked mitochondrial dysfunction to carcinogenesis, and the current progress of mitochondrial cancer biomarker studies and development.

Prostate Cancer Biomarker Development: National Cancer Institute's Early Detection Research Network Prostate Cancer Collaborative Group Review

Prostate cancer remains the most common non-skin cancer and second leading cause of death among men in the United States. Although progress has been made in diagnosis and risk assessment, many clinical questions remain regarding early identification of prostate cancer and management. The early detection of aggressive disease continues to provide high curative rates if diagnosed in a localized state. Unfortunately, prostate cancer displays significant heterogeneity within the prostate organ and between individual patients making detection and treatment strategies complex. Although prostate cancer is common among men, the majority will not die from prostate cancer, introducing the issue of overtreatment as a major concern in clinical management of the disease. The focus of the future is to identify those at highest risk for aggressive prostate cancer and to develop prevention and screening strategies, as well as discerning the difference in malignant potential of diagnosed tumors. The Prostate Cancer Research Group of the National Cancer Institute's Early Detection Research Network has contributed to the progress in addressing these concerns. This summary is an overview of the activities of the group.See all articles in this CEBP Focus section, "NCI Early Detection Research Network: Making Cancer Detection Possible."

Mitochondrial DNA copy number in peripheral blood leukocytes is associated with biochemical recurrence in prostate cancer patients in African Americans

Mitochondria play multiple important cellular functions. The purpose of this study was to evaluate whether leukocyte mitochondrial DNA copy number (mtDNAcn) is associated with aggressive prostate cancer (PCa) in African American (AA) men. We measured the mtDNAcn in peripheral blood leukocytes from 317 localized AA PCa patients and evaluated its associations with aggressive disease features at diagnosis and biochemical recurrence (BCR) after treatments. There was no significant difference in mtDNAcn among the clinical features at diagnosis, including age, prostate-specific antigen level, Gleason score and clinical stage under analysis of variance test. However, mtDNAcn was significantly associated with BCR in multivariate Cox analysis. Dichotomized into low and high mtDNAcn groups by the median value of mtDNAcn, patients with low mtDNAcn exhibited a significantly lower risk of BCR (hazard ratio = 0.32, 95% confidence interval: 0.13-0.79) compared to those with high mtDNAcn. There was a significant dose-response in tertile and quartile analyses (P for trend = 0.012 and 0.002, respectively). In Kaplan-Meier survival analyses, patients with higher mtDNAcn exhibited significantly shorter BCR-free survival time than those with lower mtDNAcn in dichotomous, tertile and quartile analyses, with long-rank P values of 0.017, 0.024 and 0.019, respectively. Our results showed for the first time that high leukocyte mtDNAcn was associated with worse prognosis in AA PCa patients.

Mitochondrial inheritance and cancer

Mitochondria are essential intracellular organelles that are responsible for energy metabolism, cell growth, and differentiation, redox homeostasis, oncogenic signaling, and apoptosis. These multifunctional organelles have been implicated in cancer initiation, progression, and metastasis, relapse, and acquired drug resistance due to metabolic alterations in transformed cells. Maternally inherited mitochondrial DNA (mtDNA) is thought to contribute to cancer development and prognosis and proposed as a therapeutic target for cancer treatment. In this review, we summarize the current knowledge of mtDNA alterations, with a specific focus on somatic changes, germline variants, haplogroups, large deletions, and mtDNA content changes associated with cancer susceptibility and prognosis. We also discuss the potential of mtDNA as biomarkers of cancer detection and targets of cancer treatment. Deeper understanding of the mechanisms underlying these associations requires further investigation.

A single mitochondrial DNA deletion accurately detects significant prostate cancer in men in the PSA 'grey zone'

Purpose

To determine the clinical performance of a blood-based test for clinically significant (CS) prostate cancer (PCa) (grade group ≥ 2) intended for use in men with prostate serum antigen levels in the ‘grey zone’ (PSA < 10 ng/ml). The test quantifies a previously described 3.4 kb mitochondrial DNA (mtDNA) deletion.

Methods

In a first prospective study of an MRI-guided re-biopsy population (n = 126), the 3.4 kb deletion and 18S rRNA gene were amplified from plasma. A diagnostic threshold was selected from the coordinates of the receiver operating characteristic curve and tested in a second population of men who were (n = 92) biopsy naïve when the mtDNA deletion was assayed and for whom those diagnosed with cancer on initial biopsy were treated with radical prostatectomy.

Results

The 3.4 kb deletion was a good predictor of CS PCa in the image-guided re-biopsy population [AUC 0.84, (95% CI 0.73–0.95)] and the selected threshold corresponded to a sensitivity of 87% [95% CI, 70–96%], specificity of 68% [95% CI, 47–85%] and negative predictive value (NPV) of 97%. Applying this threshold to the second population showed this deletion to be a strong predictor of CS cancer [AUC 0.98, (95% CI 0.94–1.02)], independent of PSA or age [sensitivity 100% (95% CI, 93–100%), specificity 90% (95%CI 73–98%) and NPV 100%].

Conclusion

The 3.4 kb deletion in plasma is an accurate predictor of CS cancer for men in the PSA ‘grey zone’. Used in advance of biopsy for improved patient selection, this deletion may reduce the number of biopsies needed to diagnose CS prostate cancers.

Electronic supplementary material

The online version of this article (10.1007/s00345-017-2152-z) contains supplementary material, which is available to authorized users.

Somatic Mutation Analyses in Studies of the Clonal Evolution and Diagnostic Targets of Prostate Cancer

Prostate cancer (PC) is the most common uro-oncological disease in the global population and still requires a more efficient laboratory diagnosis. Point mutations of oncogenes and tumor sup-pressor genes are the most frequent molecular genetic events in carcinogenesis. The mutations are re-sponsible, to a great extent, for the clonal evolution of cancer and can be considered as primary candi-date molecular markers of PC. Using next-generation sequencing to analyze the mutations in PC, the main molecular PC subtypes were identified, which depended on the presence of fusion genes and FOXA1, CHD1, and SPOP point mutations; other driver mutations responsible for the progression of PC subclones were also characterized. This review summarizes the data on early PC genetic markers (an mtDNA deletion, and TMPRSS2:ERG expression), as well as these somatic mutations at later stages of PC. Emphasis is placed on a switch in AR synthesis to a constitutively active variant and the point muta-tions that facilitate PC transition to a castration-refractory state that is resistant to new AR inhibitors. Based on the current whole-exome sequencing data, the frequencies and localizations of the somatic mu-tations that may provide new genetic diagnostic markers and drug targets are described.