Mitochondrial genome microsatellite instability and copy number alteration in lung carcinomas

The role of mitochondria in tumor metastasis and advances in mitochondria-targeted cancer therapy

Mitochondria are central actors in diverse physiological phenomena ranging from energy metabolism to stress signaling and immune modulation. Accumulating scientific evidence points to the critical involvement of specific mitochondrial-associated events, including mitochondrial quality control, intercellular mitochondrial transfer, and mitochondrial genetics, in potentiating the metastatic cascade of neoplastic cells. Furthermore, numerous recent studies have consistently emphasized the highly significant role mitochondria play in coordinating the regulation of tumor-infiltrating immune cells and immunotherapeutic interventions. This review provides a comprehensive and rigorous scholarly investigation of this subject matter, exploring the intricate mechanisms by which mitochondria contribute to tumor metastasis and examining the progress of mitochondria-targeted cancer therapies.

The Evaluation of Mass/DNA Copy Number of Mitochondria in Umbilical Cord Blood-derived Hematopoietic Stem Cells Cocultured with MSCs

Over recent decades, UCB has been widely used as an excellent alternative source of HSCs for treating many hematologic disorders. Recent studies suggest using mesenchymal stroma cell co-cultures to increase the number of HSCs prior to transplantation. Considering the critical role of mitochondria in the cell's fate and the importance of the self-renewal capacity of HSCs in HSCT, we decided to investigate the mass/DNA copy number of mitochondria in HSCs while co-cultured with MSCs and alone after seven days. UCB units were collected from full-term deliveries. MSCs and HSCs were isolated from UCB and the purity of cells was confirmed by flow cytometry. The mtDNA-Copy Number of HSCs was calculated using prob-based real-time PCR. Furthermore, Mito Tracker Green dye measured the mass of mitochondria of HSCs. HSCs from MSC co-culture group showed significantly fewer mtDNA-CN compared to HSCs alone after seven days (p < 0.001). Besides, by comparing the two groups on day seven to HSCs on day zero, we observed a mild increase in the mitochondrial mass of HSCs alone compared to the MSC-HSC co-culture group (p < 0.05). Concerning previous studies that have proved the association between lower mass/DNA-copy number of mitochondria in CD34 + HSCs and lower metabolic activity along with higher quiescence maintenance, and by considering the results of this experiment, it seems that the MSC-HSC co-cultures might be associated with a higher expansion of HSCs as well as stemness maintenance leading to the improvement in engraftment. Nevertheless, further investigations are required to clarify the exact connection between lower mass/DNA-copy number of mitochondria and stemness maintenance in HSCs.

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.

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.

Clinical application of plasma mitochondrial DNA content in patients with lung cancer

Alterations of mitochondrial DNA (mtDNA) have been identified in several types of solid tumor. However, to the best of our knowledge, the clinical significance of plasma mtDNA content in lung cancer remains unknown. Thus, the current study explored the diagnostic and prognostic value of plasma mtDNA quantification in patients with lung cancer. Plasma mtDNA copy numbers of patients with lung cancer (n=128) and healthy individuals (n=107) were quantified by quantitative polymerase chain reaction. Plasma mtDNA copy numbers in patients and healthy controls were 0.89×10⁴ and 1.37×10⁴ copies/µl, respectively (P<0.0001). Furthermore, lower plasma mtDNA content was associated with tumor size, lymph node metastases, distant metastases and serum carcinoembryonic antigen levels (P<0.05), but was not associated with pathological type, age, sex or main driver gene mutation status (P>0.05). Plasma mtDNA facilitated the detection of lung cancer at a threshold of 1.19×10⁴ copies/µl with a sensitivity of 71.1% and specificity of 70.1%, as determined by receiver operating characteristic curve analysis. Advanced stage (III and IV) patients with a lower mtDNA copy number (cutoff: 1.02×10⁴ copies/µl) tended to exhibit poorer prognosis (P<0.05). These results indicated that plasma mtDNA content is a promising and complementary candidate with tissue mtDNA for diagnosis and prognostic prediction for lung cancer.

Prevalence of somatic mitochondrial mutations and spatial distribution of mitochondria in non-small cell lung cancer

BACKGROUND

Mitochondria are considered relevant players in many tumour entities and first data indicate beneficial effects of mitochondria-targeted antioxidants in both cancer prevention and anticancer therapies. To further dissect the potential roles of mitochondria in NSCLC we comprehensively analysed somatic mitochondrial mutations, determined the spatial distribution of mitochondrial DNA within complete tumour sections and investigated the mitochondrial load in a large-scale approach.

METHODS

Whole mitochondrial genome sequencing of 26 matched tumour and non-neoplastic tissue samples extended by reviewing published data of 326 cases. Systematical stepwise real-time PCR quantification of mitochondrial DNA covering 16 whole surgical tumour sections. Immunohistochemical determination of the mitochondrial load in 171 adenocarcinoma and 145 squamous cell carcinoma.

RESULTS

Our results demonstrate very low recurrences (max. 1.7%) and a broad distribution of 456 different somatic mitochondrial mutations. Large inter- and intra-tumour heterogeneity were seen for mitochondrial DNA copy numbers in conjunction with a correlation to the predominant histological growth pattern. Furthermore, tumour cells had significantly higher mitochondrial level compared to adjacent stroma, whereas differences between tumour entities were negligible.

CONCLUSIONS

Non-evident somatic mitochondrial mutations and highly varying mitochondrial DNA level delineate challenges for the approach of mitochondria-targeted anticancer therapies in NSCLC.

Nuclear and mitochondrial DNAs microsatellite instability and mitochondrial DNA copy number in adenocarcinoma and squamous cell carcinoma of lung: a pilot study

Mitochondrial genetic changes are considered as a key molecular step of mutations in various cancers. To clarify the role of genetic instability in lung cancer, we analyzed clinicopathological characteristics and frequencies of nuclear and mitochondrial microsatellite instability (nMSI and mtMSI), and alteration of mitochondrial DNA copy number (mtCN) in adenocarcinoma (ADC) and squamous cell carcinoma (SCC) of lung. DNA was isolated from 48 patients with ADC and 42 with SCC. Markers for nMSI, BAT 25 and 26, and markers for mtMSI, (C)n and (CA)n in mitochondrial D-loop region, were utilized. The mtCN were measured by real-time polymerase chain reaction. The nMSI was found in two patients (4.2%) of ADC and 6 (14.3%) of SCC. The mtMSI was detected in 10 patients (20.8%) of ADC and 8 (19.0%) of SCC. Mean mtCN was 5.05 ± 8.17 and 3.34 ± 5.14 in ADC and SCC respectively. The mtCN was increased in 35 patients (72.9%) of ADC and 30 (71.4%) of SCC. The mtMSI more frequently appeared in more advanced pathologic T stage in ADC (p = 0.003). Alterations of mtCN and a high frequency of mtMSI in our patient samples indicate that mitochondrial DNA is a potential molecular marker in lung cancers (ADC and SCC) correlating with their histological classification.

17β-Hydroxysteroid dehydrogenase type 10 predicts survival of patients with colorectal cancer and affects mitochondrial DNA content

Mitochondrial energy production is reduced in tumor cells, and altered mitochondrial respiration contributes to tumor progression. Synthesis of proteins coded by mitochondrial DNA (mtDNA) requires the correct processing of long polycistronic precursor RNA molecules. Mitochondrial RNase P, composed of three different proteins (MRPP1, HSD10, and MRPP3), is necessary for correct RNA processing. Here we analyzed the role of RNase P proteins in colorectal cancer. High HSD10 expression was found in 28%; high MRPP1 expression in 40% of colorectal cancers, respectively. Expression of both proteins was not significantly associated with clinicopathological parameters. Survival analysis revealed that loss of HSD10 expression is associated with poor prognosis. Cox regression demonstrated that patients with high HSD10 tumors are at lower risk. High HSD10 expression was significantly associated with high mtDNA content in tumor tissue. A causal effect of HSD10 overexpression or knock down with increased or reduced mtDNA levels, respectively, was confirmed in tumor cell lines. Our data suggest that HSD10 plays a role in alterations of energy metabolism by regulating mtDNA content in colorectal carcinomas, and HSD10 protein analysis may be of prognostic value.

Analysis of mitochondrial DNA alteration in new phenotype ACOS

BACKGROUND

Mitochondria contain their own DNA (MtDNA) that is very sensitive to oxidative stress and as a consequence could be damaged in quantity. Oxidative stress is largely recognized to play a key role in the pathogenesis of asthma and COPD and might have a role in the new intermediate phenotype ACOS (asthma-COPD overlap syndrome). The aim of this study was to investigate MtDNA alterations, as an expression of mitochondrial dysfunction, in ACOS and to verify whether they might help in the identification of this new phenotype and in its differentiation from asthma and COPD.

METHODS

Ten (10) ACOS according to Spanish guidelines, 13 ACOS according to GINA guidelines, 13 COPD, 14 asthmatic patients and ten normal subjects were enrolled. They further underwent a blood, induced sputum and exhaled nitric oxide collection. Content of MtDNA and nuclear DNA (nDNA) were measured in the blood cells of patients by Real Time PCR.

RESULTS

ACOS patients showed an increase of MtDNA/nDNA ratio. Dividing ACOS according to guidelines, those from the Spanish showed a higher value of MtDNA/nDNA compared to those from GINA/GOLD (92.69 ± 7.31 vs 80.68 ± 4.16). Spanish ACOS presented MtDNA/nDNA ratio closer to COPD than asthma. MtDNA was higher in asthmatic, COPD, GINA and Spanish ACOS patients compared to healthy subjects (73.30 ± 4.47-137.0 ± 19.45-80.68 ± 4.16-92.69 ± 7.31 vs 65.97 ± 20.56).

CONCLUSION

We found an increase of MtDNA/nDNA ratio in ACOS subjects that led us to conclude that there is presence of mitochondrial dysfunction in this disease, that makes it closer to COPD than to asthma. Although the MtDNA/nDNA ratio results are a useful marker for differential diagnosis from asthma, COPD and ACOS, further studies are needed to confirm the potentiality of MtDNA/nDNA ratio and to a better characterization of ACOS.

Mitochondrial DNA levels in blood and tissue samples from breast cancer patients of different stages

AIMS

Alterations in mitochondrial DNA (mtDNA) have been implicated in carcinogenesis and tumor progression. We here evaluated the diagnostic and prognostic potential of mtDNA as a biomarker for breast cancer.

METHODS

Using multiplex real-time polymerase chain reaction, nuclear DNA (nDNA) and mtDNA levels in serum, buffy coat, tumor, and tumor-adjacent tissue samples from 50 breast cancer patients were determined and assessed for associations with clinicopathological features. To evaluate mtDNA as a biomarker for distinguishing between the four sample types, we created receiver operating characteristic (ROC) curves.

RESULTS

The mtDNA levels in buffy coat were significantly lower than in other sample types. Relative to tumor-adjacent tissue, reduced levels of mtDNA were identified in buffy coat and tumor tissue but not in serum. According to ROC curve analysis, mtDNA levels could be used to distinguish between buffy coat and tumor-adjacent tissue samples with good sensitivity (77%) and specificity (83%). Moreover, mtDNA levels in serum and tumor tissue were positively associated with cancer TMN stage.

CONCLUSIONS

The mtDNA levels in blood samples may represent a promising, non-invasive biomarker in breast cancer patients. Additional, large-scale validation studies are required to establish the potential use of mtDNA levels in the early diagnosis and monitoring of breast cancer.