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

Genetic and biological drivers of prostate cancer disparities in Black men

Black men with prostate cancer have historically had worse outcomes than white men with prostate cancer. The causes of this disparity in outcomes are multi-factorial, but a potential basis is that prostate cancers in Black men are biologically distinct from prostate cancers in white men. Evidence suggests that genetic and ancestral factors, molecular pathways involving androgen and non-androgen receptor signalling, inflammation, epigenetics, the tumour microenvironment and tumour metabolism are contributing factors to the racial disparities observed. Key genetic and molecular pathways linked to prostate cancer risk and aggressiveness have potential clinical relevance. Describing biological drivers of prostate cancer disparities could inform efforts to improve outcomes for Black men with prostate cancer.

High leukocyte mitochondrial DNA copy number contributes to poor prognosis in breast cancer patients

BACKGROUND

Compelling evidence has indicated a significant association between leukocyte mitochondrial DNA copy number (mtDNAcn) and prognosis of several malignancies in a cancer-specific manner. However, whether leukocyte mtDNAcn can predict the clinical outcome of breast cancer (BC) patients has not been well investigated.

METHODS

The mtDNA copy number of peripheral blood leukocytes from 661 BC patients was measured using a Multiplex AccuCopy™Kit based on a multiplex fluorescence competitive PCR principle. Kaplan-Meier curves and Cox proportional hazards regression model were applied to investigate the association of mtDNAcn with invasive disease-free survival (iDFS), distant disease-free survival (DDFS), breast cancer special survival (BCSS), and overall survival (OS) of patients. The possible mtDNAcn-environment interactions were also evaluated by the Cox proportional hazard regression models.

RESULTS

BC patients with higher leukocyte mtDNA-CN exhibited a significantly worse iDFS than those with lower leukocyte mtDNAcn (5-year iDFS: fully-adjusted model: HR = 1.433[95%CI 1.038-1.978], P = 0.028). Interaction analyses showed that mtDNAcn was significantly associated with hormone receptor status (adjusted p for interaction: 5-year BCSS: 0.028, 5-year OS: 0.022), so further analysis was mainly in the HR subgroup. Multivariate Cox regression analysis demonstrated that mtDNAcn was an independent prognostic factor for both BCSS and OS in HR-positive patients (HR+: 5-year BCSS: adjusted HR (aHR) = 2.340[95% CI 1.163-4.708], P = 0.017 and 5-year OS: aHR = 2.446 [95% CI 1.218-4.913], P = 0.011).

CONCLUSIONS

For the first time, our study demonstrated that leukocyte mtDNA copy number might influence the outcome of early-stage breast cancer patients depending on intrinsic tumor subtypes in Chinese women.

Mitochondrial Alterations in Prostate Cancer: Roles in Pathobiology and Racial Disparities

Prostate cancer (PCa) affects millions of men worldwide and is a major cause of cancer-related mortality. Race-associated PCa health disparities are also common and are of both social and clinical concern. Most PCa is diagnosed early due to PSA-based screening, but it fails to discern between indolent and aggressive PCa. Androgen or androgen receptor-targeted therapies are standard care of treatment for locally advanced and metastatic disease, but therapy resistance is common. Mitochondria, the powerhouse of cells, are unique subcellular organelles that have their own genome. A large majority of mitochondrial proteins are, however, nuclear-encoded and imported after cytoplasmic translation. Mitochondrial alterations are common in cancer, including PCa, leading to their altered functions. Aberrant mitochondrial function affects nuclear gene expression in retrograde signaling and promotes tumor-supportive stromal remodeling. In this article, we discuss mitochondrial alterations that have been reported in PCa and review the literature related to their roles in PCa pathobiology, therapy resistance, and racial disparities. We also discuss the translational potential of mitochondrial alterations as prognostic biomarkers and as effective targets for PCa therapy.

Associations of mitochondrial DNA copy number with incident risks of gastrointestinal cancers: A prospective case-cohort study

Epidemiological investigations implied that mitochondrial DNA copy number (mtDNAcn) variations could trigger predisposition to multiple cancers, but evidence regarding gastrointestinal cancers (GICs) was still uncertain. We conducted a case-cohort study within the prospective Dongfeng-Tongji cohort, including incident cases of colorectal cancer (CRC, n = 278), gastric cancer (GC, n = 138), and esophageal cancer (EC, n = 72) as well as a random subcohort (n = 1173), who were followed up from baseline to the end of 2018. We determined baseline blood mtDNAcn and associations of mtDNAcn with the GICs risks were estimated by using weighted Cox proportional hazards models. Significant U-shaped associations were observed between mtDNAcn and GICs risks. Compared to subjects within the second quartile (Q2) mtDNAcn subgroup, those within the 1st (Q1), 3rd (Q3), and 4th (Q4) quartile subgroups showed increased risks of CRC (hazard ratio [HR] [95% confidence interval, CI] = 2.27 [1.47-3.52], 1.65 [1.04-2.62], and 2.81 [1.85-4.28], respectively) and total GICs (HR [95%CI] = 1.84 [1.30-2.60], 1.47 [1.03-2.10], and 2.51 [1.82-3.47], respectively], and those within Q4 subgroup presented elevated GC and EC risks (HR [95% CI] = 2.16 [1.31-3.54] and 2.38 [1.13-5.02], respectively). Similar associations of mtDNAcn with CRC and total GICs risks remained in stratified analyzes by age, gender, smoking, and drinking status. This prospective case-cohort study showed U-shaped associations between mtDNAcn and GICs risks, but further research works are needed to uncover underlying biological mechanisms.

Insights regarding mitochondrial DNA copy number alterations in human cancer (Review)

Mitochondria are the critical organelles involved in various cellular functions. Mitochondrial biogenesis is activated by multiple cellular mechanisms which require a synchronous regulation between mitochondrial DNA (mtDNA) and nuclear DNA (nDNA). The mitochondrial DNA copy number (mtDNA-CN) is a proxy indicator for mitochondrial activity, and its alteration reflects mitochondrial biogenesis and function. Despite the precise mechanisms that modulate the amount and composition of mtDNA, which have not been fully elucidated, mtDNA-CN is known to influence numerous cellular pathways that are associated with cancer and as well as multiple other diseases. In addition, the utility of current technology in measuring mtDNA-CN contributes to its extensive assessment of diverse traits and tumorigenesis. The present review provides an overview of mtDNA-CN variations across human cancers and an extensive summary of the existing knowledge on the regulation and machinery of mtDNA-CN. The current information on the advanced methods used for mtDNA-CN assessment is also presented.

Systemic Effects Reflected in Specific Biomarker Patterns Are Instrumental for the Paradigm Change in Prostate Cancer Management: A Strategic Paper

Prostate cancer (PCa) is reported as the most common malignancy and second leading cause of death in America. In Europe, PCa is considered the leading type of tumour in 28 European countries. The costs of treating PCa are currently increasing more rapidly than those of any other cancer. Corresponding economic burden is enormous, due to an overtreatment of slowly developing disease on one hand and underestimation/therapy resistance of particularly aggressive PCa subtypes on the other hand. The incidence of metastatic PCa is rapidly increasing that is particularly characteristic for young adults. PCa is a systemic multi-factorial disease resulting from an imbalanced interplay between risks and protective factors. Sub-optimal behavioural patterns, abnormal stress reactions, imbalanced antioxidant defence, systemic ischemia and inflammation, mitochondriopathies, aberrant metabolic pathways, gene methylation and damage to DNA, amongst others, are synergistically involved in pathomechanisms of PCa development and progression. To this end, PCa-relevant systemic effects are reflected in liquid biopsies such as blood patterns which are instrumental for predictive diagnostics, targeted prevention and personalisation of medical services (PPPM/3P medicine) as a new paradigm in the overall PCa management. This strategic review article highlights systemic effects in prostate cancer development and progression, demonstrates evident challenges in PCa management and provides expert recommendations in the framework of 3P medicine.

Identification of a Transcriptomic Prognostic Signature by Machine Learning Using a Combination of Small Cohorts of Prostate Cancer

Determining which treatment to provide to men with prostate cancer (PCa) is a major challenge for clinicians. Currently, the clinical risk-stratification for PCa is based on clinico-pathological variables such as Gleason grade, stage and prostate specific antigen (PSA) levels. But transcriptomic data have the potential to enable the development of more precise approaches to predict evolution of the disease. However, high quality RNA sequencing (RNA-seq) datasets along with clinical data with long follow-up allowing discovery of biochemical recurrence (BCR) biomarkers are small and rare. In this study, we propose a machine learning approach that is robust to batch effect and enables the discovery of highly predictive signatures despite using small datasets. Gene expression data were extracted from three RNA-Seq datasets cumulating a total of 171 PCa patients. Data were re-analyzed using a unique pipeline to ensure uniformity. Using a machine learning approach, a total of 14 classifiers were tested with various parameters to identify the best model and gene signature to predict BCR. Using a random forest model, we have identified a signature composed of only three genes (JUN, HES4, PPDPF) predicting BCR with better accuracy [74.2%, balanced error rate (BER) = 27%] than the clinico-pathological variables (69.2%, BER = 32%) currently in use to predict PCa evolution. This score is in the range of the studies that predicted BCR in single-cohort with a higher number of patients. We showed that it is possible to merge and analyze different small and heterogeneous datasets altogether to obtain a better signature than if they were analyzed individually, thus reducing the need for very large cohorts. This study demonstrates the feasibility to regroup different small datasets in one larger to identify a predictive genomic signature that would benefit PCa patients.

Methods for simultaneous and quantitative isolation of mitochondrial DNA, nuclear DNA and RNA from mammalian cells

The aim of this study was to assess two protocols for their capacities to simultaneously isolate RNA, mtDNA and ncDNA from mammalian cells. We compared the Invitrogen TRIzol-based method and Qiagen DNeasy columns, using the HepG2 cell line and human primary glioblastoma stem cells. Both methods allowed the isolation of all three types of nucleic acids and provided similar yields in mtDNA. However, the yield in ncDNA was more than tenfold higher on columns, as observed for both cell types. Conversely, the TRIzol method proved more reproducible and was the method of choice for isolating RNA from glioblastoma cells, as demonstrated for the housekeeping genes RPLP0 and RPS9.

Association between pre-diagnostic leukocyte mitochondrial DNA copy number and survival among colorectal cancer patients

BACKGROUND

Mitochondrial DNA copy number (mtDNAcn) is considered a biomarker for mitochondrial function and oxidative stress. Although previous studies have suggested a potential relationship between mtDNAcn at the time of colorectal cancer (CRC) diagnosis and CRC prognosis, findings have been inconsistent, and no study has specifically investigated the association of pre-diagnostic mtDNAcn with CRC survival.

METHODS

We examined the association of pre-diagnostic leukocyte mtDNAcn (measured by qPCR) with overall and CRC-specific survival among 587 patients in Nurses' Health Study and Health Professionals Follow-Up Study. Cox models were constructed to estimate hazard ratios (HRs) and 95 % confidence intervals (95 % CIs).

RESULTS

During a mean follow-up of 10.5 years, 395 deaths were identified; 180 were due to CRC. Overall, we did not observe significant associations between mtDNAcn and either overall or CRC-specific survival among all cases or by cancer location, grade, or stage. In an exploratory stratified analysis, a suggestive inverse association of mtDNAcn and overall death risk appeared among current smokers [HR (95 % CI) for 1 SD decrease in mtDNAcn = 1.50 (0.98, 2.32), P-trend = 0.06]. Reduced mtDNAcn and lower CRC-specific death risk was observed among patients aged ≤ 70.5 at diagnosis [HR (95 % CI) for 1 SD decrease of mtDNAcn = 0.71 (0.52, 0.97), P-trend = 0.03], ≤ 5 years from blood collection to diagnosis [HR (95 % CI) for 1 SD decrease in mtDNAcn = 0.65 (0.44, 0.96), P-trend = 0.03] and those consuming a low-inflammatory diet [HR (95 % CI) for 1 SD decrease in mtDNAcn = 0.61 (0.42, 0.88), P-trend = 0.009].

CONCLUSION

no significant associations between pre-diagnostic leukocyte mtDNAcn and either overall or CRC-specific survival appeared but exploratory analysis identified potential sub-group associations.

Deregulated Mitochondrial DNA in Diseases

Mitochondria play various important roles in energy production, metabolism, and apoptosis. Mitochondrial dysfunction caused by alterations in mitochondrial DNA (mtDNA) can lead to the initiation and progression of cancers and other diseases. These alterations include mutations and copy number variations. Especially, the mutations in D-loop, MT-ND1, and MT-ND5 affect mitochondrial functions and are widely detected in various cancers. Meanwhile, several other mutations have been correlated with muscular and neuronal diseases, especially MT-TL1 is deeply related. These pieces of evidence indicated mtDNA alterations in diseases show potential as a novel therapeutic target. mtDNA repair enzymes are the target for delaying or stalling the mtDNA damage-induced cancer progression and metastasis. Moreover, some mutations reveal a prognosis ability of the drug resistance. Current efforts aim to develop mitochondrial transplantation technique as a direct cure for deregulated mitochondria-associated diseases. This review summarizes the implications of mitochondrial dysfunction in cancers and other pathologies; and discusses the relevance of mitochondria-targeted therapies, along with their contribution as potential biomarkers.