Effect of mtDNA mutation on tumor malignant degree in patients with prostate cancer

Racial differences in circulating mitochondria-derived peptides may contribute to prostate cancer health disparities

INTRODUCTION

The mitochondrial genome has small open reading frames (sORF) which produce measurable mitochondrial-derived peptides (MDPs), including humanin, SHLP2, and MOTS-c. Previously, among men undergoing prostate biopsy, we found higher serum SHLP2 was linked with lower prostate cancer (PC) risk in European American men (EAM), while null associations were found in African American men (AAM). Here, in different patients undergoing prostate biopsy, we tested the link between SHLP2, humanin and MOTS-c and PC risk by race.

METHODS

Plasma SHLP2, humanin, and MOTS-c were measured in 198 men (50/49 EAM/AAM cases; 50/49 EAM/AAM controls) undergoing biopsy. Logistic and multinomial regression models tested associations between each MDP and PC diagnosis, low-grade (grade group, GG1) and high-grade (GG2-5). Models were adjusted for age, body mass index, digital rectal examination, and prostate specific antigen (PSA). We tested interactions between MDPs and race.

RESULTS

Among controls, humanin was similar by race (p = 0.60), but both SHLP2 (p = 0.007) and MOTS-c (p = 0.026) were lower in AAM controls versus EAM controls. Among EAM, higher MDP values were associated with lower PC risk (all p ≤ 0.001), with null associations in AAM (all p-interactions ≤ 0.01). Similarly, higher MDP expression was associated with decreased risk of low- and high-grade PC in EAM (all p ≤ 0.005) with null associations in AAM.

CONCLUSIONS

Higher MDP levels were associated with lower PC risk in EAM but not AAM. Generally, AAM controls had lower MDP levels. These data support MDPs and mitochondrial dysfunction in PC, suggesting greater dysfunction in AAM may contribute to excess PC risk. Future larger studies are needed to confirm these results.

Hematologic parameters are not predictors of upgrading or treatment in a racially diverse prospective study of men with prostate cancer on active surveillance

INTRODUCTION

Neutrophil-to-lymphocyte (NLR) and platelet-to-lymphocyte ratios (PLR) are useful clinical biomarkers for prognosis in several malignancies. Their predictive value has been less clearly demonstrated with prostate cancer (PCa), particularly, their utility within active surveillance (AS) protocols. We aim to evaluate NLR and PLR in AS patients.

METHODS

We identified 98 patients who met inclusion criteria in our cohort of 274 men diagnosed with PCa on AS. Patients were then categorized into high and low NLR and PLR groups.

RESULTS

The 2.5 and 5-year Gleason upgrading free probability for our high NLR cohort was 73.9%(CI 56.3% to 97.0%) and 46.2%(CI 22.4% to 95.1%) compared to 76.3%(CI 65.7% to 88.7%) and 61.7%(CI 47.7% to 80.0%) in the low NLR cohort(p = .73). The 2.5 and 5-year Gleason upgrading free probability for our High PLR cohort was 73.5%(CI 57.3% to 94.2%) and 60.1(CI 41.4% to 87.4%) compared to 76.8%(CI 65.8% to 89.65) and 58.1%(CI 42.2% to 80.1%) in our low PLR group(p = .41). A multivariant analysis demonstrated these groups were not significant predictors of upgrading or treatment.

CONCLUSION

Despite their usefulness in many types of malignancy, NLR and PLR were not predictors of upgrading or treatment in men on AS for localized PCa in our cohort.

Mangosteen pericarp components alleviate progression of prostatic hyperplasia and mitochondrial dysfunction in rats

Prostatic hyperplasia, characterized by progressive hyperplasia of glandular and stromal tissues, is the most common proliferative abnormality of the prostate in aging men. A high-fat diet (HFD) usually is a major factor inducing oxidative stress, inflammation, and an abnormal state of the prostate. Mangosteen pericarp powder (MPP) has abundant xanthones which can be antioxidant, anti-inflammatory, and antiproliferative agents. Therefore, the purpose of this study was to research whether MPP supplementation can affect the progression of prostatic hyperplasia. Twenty-four male F344 rats were randomly divided into four groups, including a control group (C), prostatic hyperplasia-induced group (P), prostatic hyperplasia-induced with low-dose MPP group (PL), and induced with high-dose MPP group (PH). The P, PL, and PH groups were given weekly intraperitoneal injections of 3,2′-dimethyl-4-aminobiphenyl (DMAB) at 25 mg/kg body weight for 10 weeks, and simultaneously fed an HFD for 24 weeks. Our findings first demonstrated that MPP consumption significantly decreased the prostate weight, serum testosterone and dihydrotestosterone concentrations, protein expression of proliferating cell nuclear antigen, and malondialdehyde levels and ameliorated mitochondrial function in prostatic tissues. These results suggest that MPP supplementation could be used to attenuate the progression of prostatic hyperplasia.

A comprehensive overview of mitochondrial DNA 4977-bp deletion in cancer studies

Mitochondria are cellular machines essential for energy production. The biogenesis of mitochondria is a highly complex and it depends on the coordination of the nuclear and mitochondrial genome. Mitochondrial DNA (mtDNA) mutations and deletions are suspected to be associated with carcinogenesis. The most described mtDNA deletion in various human cancers is called the 4977-bp common deletion (mDNA⁴⁹⁷⁷) and it has been explored since two decades. In spite of that, its implication in carcinogenesis still unknown and its predictive and prognostic impact remains controversial. This review article provides an overview of some of the cellular and molecular mechanisms underlying mDNA⁴⁹⁷⁷ formation and a detailed summary about mDNA⁴⁹⁷⁷ reported in various types of cancers. The current knowledges of mDNA⁴⁹⁷⁷ as a prognostic and predictive marker are also discussed.

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.

A mitochondrial DNA mutation influences the apoptotic effect of statins on prostate cancer

BACKGROUND

Statins, 3-hydroxy-3 methylglutaryl coenzyme A (HMG-CoA) reductase inhibitors, are currently the most widely used cholesterol-lowering drugs. Previous epidemiological studies have suggested that there may be be an association between statin use and decreased risk of prostate cancer progression. Both inherited and somatic mutations of the mitochondrial genome are linked to prostate cancer. The purpose of this study was to determine if mitochondrial DNA (mtDNA) background and hence mitochondrial biochemistry can modulate the efficiency of statin as an anti-prostate cancer agent.

METHODS

Cytoplasmic hybrid (cybrid) cell lines were constructed that contained a prostate cancer nucleus and either wild type or mutant mtDNA derived from a prostate cancer patient with the cytochrome oxidase subunit 1 gene mutation T6124C (Met74Thr). Multiple clones for each genotype were tested. After treating both wild type and mutant cells with increasing concentrations of simvastatin for 72 hr, cell proliferation and apoptosis were analyzed.

RESULTS

Simvastatin inhibited both wild type and mutant cell proliferation. However, cells with the T6124C mtDNA mutation were more resistant to drug treatment than the wild type cells. In addition, analysis of caspase 3 assays and multiple proteins involved in cellular apoptosis demonstrated that mutant cells were more resistant to simvastatin treatment-induced apoptosis than wild type control cells.

CONCLUSIONS

Simvastatin treatment induced apoptosis in human cybrid prostate cancer cells. The response to drug treatments was different depending on mitochondrial genotype. Therefore, the degree to which statins may affect prostate cancer progression may vary based on an individual's mtDNA background.

High Mobility Group B Proteins, Their Partners, and Other Redox Sensors in Ovarian and Prostate Cancer

Cancer cells try to avoid the overproduction of reactive oxygen species by metabolic rearrangements. These cells also develop specific strategies to increase ROS resistance and to express the enzymatic activities necessary for ROS detoxification. Oxidative stress produces DNA damage and also induces responses, which could help the cell to restore the initial equilibrium. But if this is not possible, oxidative stress finally activates signals that will lead to cell death. High mobility group B (HMGB) proteins have been previously related to the onset and progressions of cancers of different origins. The protein HMGB1 behaves as a redox sensor and its structural changes, which are conditioned by the oxidative environment, are associated with different functions of the protein. This review describes recent advances in the role of human HMGB proteins and other proteins interacting with them, in cancerous processes related to oxidative stress, with special reference to ovarian and prostate cancer. Their participation in the molecular mechanisms of resistance to cisplatin, a drug commonly used in chemotherapy, is also revised.

High mitochondria content is associated with prostate cancer disease progression

Background

Mitochondria are suggested to be important organelles for cancer initiation and promotion. This study was designed to evaluate the prognostic value of MTC02, a marker for mitochondrial content, in prostate cancer.

Methods

Immunohistochemistry of using an antibody against MTC02 was performed on a tissue microarray (TMA) containing 11,152 prostate cancer specimens. Results were compared to histological phenotype, biochemical recurrence, ERG status and other genomic deletions by using our TMA attached molecular information.

Results

Tumor cells showed stronger MTC02 expression than normal prostate epithelium. MTC02 immunostaining was found in 96.5% of 8,412 analyzable prostate cancers, including 15.4% tumors with weak, 34.6% with moderate, and 46.5% with strong expression. MTC02 expression was associated with advanced pathological tumor stage, high Gleason score, nodal metastases (p < 0.0001 each), positive surgical margins (p = 0.0005), and early PSA recurrence (p < 0.0001) if all cancers were jointly analyzed. Tumors harboring ERG fusion showed higher expression levels than those without (p < 0.0001). In ERG negative prostate cancers, strong MTC02 immunostaining was linked to deletions of PTEN, 6q15, 5q21, and early biochemical recurrence (p < 0.0001 each). Moreover, multiple scenarios of multivariate analyses suggested an independent association of MTC02 with prognosis in preoperative settings.

Conclusions

Our study demonstrates high-level MTC02 expression in ERG negative prostate cancers harboring deletions of PTEN, 6q15, and 5q21. Additionally, increased MTC02 expression is a strong predictor of poor clinical outcome in ERG negative cancers, highlighting a potentially important role of elevated mitochondrial content for prostate cancer cell biology.

Mitochondrial common deletion, a potential biomarker for cancer occurrence, is selected against in cancer background: a meta-analysis of 38 studies

Mitochondrial dysfunction has been long proposed to play a major role in tumorigenesis. Mitochondrial DNA (mtDNA) mutations, especially the mtDNA 4,977 bp deletion has been found in patients of various types of cancer. In order to comprehend the mtDNA 4,977 bp deletion status in various cancer types, we performed a meta-analysis composed of 33 publications, in which a total of 1613 cancer cases, 1516 adjacent normals and 638 healthy controls were included. When all studies were pooled, we found that cancerous tissue carried a lower mtDNA 4,977 bp deletion frequency than adjacent non-cancerous tissue (OR = 0.43, 95% CI = 0.20-0.92, P = 0.03 for heterogeneity test, I(2) = 91.5%) among various types of cancer. In the stratified analysis by cancer type the deletion frequency was even lower in tumor tissue than in adjacent normal tissue of breast cancer (OR = 0.19, 95% CI = 0.06-0.61, P = 0.005 for heterogeneity test, I(2)= 82.7%). Interestingly, this observation became more significant in the stratified studies with larger sample sizes (OR = 0.70, 95% CI = 0.58-0.86, P = 0.0005 for heterogeneity test, I(2) = 95.1%). Furthermore, when compared with the normal tissue from the matched healthy controls, increased deletion frequencies were observed in both adjacent non-cancerous tissue (OR = 3.02, 95% CI = 2.13-4.28, P<0.00001 for heterogeneity test, I(2)= 53.7%), and cancerous tissue (OR = 1.36, 95% CI = 1.04-1.77, P = 0.02 for heterogeneity test, I(2)= 83.5%). This meta-analysis suggests that the mtDNA 4,977 bp deletion is often found in cancerous tissue and thus has the potential to be a biomarker for cancer occurrence in the tissue, but at the same time being selected against in various types of carcinoma tissues. Larger and better-designed studies are still warranted to confirm these findings.

Mitochondrial haplogroups and polymorphisms reveal no association with sporadic prostate cancer in a southern European population

BACKGROUND

It is known that mitochondria play an important role in certain cancers (prostate, renal, breast, or colorectal) and coronary disease. These organelles play an essential role in apoptosis and the production of reactive oxygen species; in addition, mtDNA also reveals the history of populations and ancient human migration. All these events and variations in the mitochondrial genome are thought to cause some cancers, including prostate cancer, and also help us to group individuals into common origin groups. The aim of the present study is to analyze the different haplogroups and variations in the sequence in the mitochondrial genome of a southern European population consisting of subjects affected (n = 239) and non-affected (n = 150) by sporadic prostate cancer.

METHODOLOGY AND PRINCIPAL FINDINGS

Using primer extension analysis and DNA sequencing, we identified the nine major European haplogroups and CR polymorphisms. The frequencies of the haplogroups did not differ between patients and control cohorts, whereas the CR polymorphism T16356C was significantly higher in patients with PC compared to the controls (p = 0.029). PSA, staging, and Gleason score were associated with none of the nine major European haplogroups. The CR polymorphisms G16129A (p = 0.007) and T16224C (p = 0.022) were significantly associated with Gleason score, whereas T16311C (p = 0.046) was linked with T-stage.

CONCLUSIONS AND SIGNIFICANCE

Our results do not suggest that mtDNA haplogroups could be involved in sporadic prostate cancer etiology and pathogenesis as previous studies performed in middle Europe population. Although some significant associations have been obtained in studying CR polymorphisms, further studies should be performed to validate these results.

Somatic mitochondrial DNA mutations in human cancers

Mitochondria are ubiquitous organelles in eukaryotic cells principally responsible for regulating cellular energy metabolism, free radical production, and the execution of apoptotic pathways. Abnormal oxidative phosphorylation (OXPHOS) and aerobic metabolism as a result of mitochondrial dysfunction have long been hypothesized to be involved in tumorigenesis. In the past decades, numerous somatic mutations in both the coding and control regions of mitochondrial DNA (mtDNA) have been extensively examined in a broad range of primary human cancers, underscoring that accumulation of mtDNA alterations may be a critical factor in eliciting persistent mitochondrial defects and consequently contributing to cancer initiation and progression. However, the roles of these mtDNA mutations in the carcinogenic process remain largely unknown. This review outlines a wide variety of somatic mtDNA mutations identified in common human malignancies and highlights recent advances in understanding the causal roles of mtDNA variations in neoplastic transformation and tumor progression. In addition, it briefly illustrates how mtDNA alterations activate mitochondria-to-nucleus retrograde signaling so as to modulate the expression of relevant nuclear genes or induce epigenetic changes and promote malignant phenotypes in cancer cells. The present state of our knowledge regarding how mutational changes in the mitochondrial genome could be used as a diagnostic biomarker for early detection of cancer and as a potential target in the development of new therapeutic approaches is also discussed. These findings strongly indicate that mtDNA mutations exert a crucial role in the pathogenic mechanisms of tumor development, but continued investigations are definitely required to further elucidate the functional significance of specific mtDNA mutations in the etiology of human cancers.