Mitochondria As A Target For Early Detection and Diagnosis of Cancer

Objective Detection of Oral Carcinoma with Multispectral Fluorescence Lifetime Imaging In Vivo

Successful early detection and demarcation of oral carcinoma can greatly impact the associated morbidity and mortality rates. Current methods for detection of oral cancer include comprehensive visual examination of the oral cavity, typically followed by tissue biopsy. A noninvasive means to guide the clinician in making a more objective and informed decision toward tissue biopsy can potentially improve the diagnostic yield of this process. To this end, we investigate the potential of fluorescence lifetime imaging (FLIM) for objective detection of oral carcinoma in the hamster cheek pouch model of oral carcinogenesis in vivo. We report that systematically selected FLIM features can differentiate between low-risk (normal, benign and low-grade dysplasia) and high-risk (high-grade dysplasia and cancer) oral lesions with sensitivity and specificity of 87.26% and 93.96%, respectively. We also show the ability of FLIM to generate "disease" maps of the tissue which can be used to evaluate relative risk of neoplasia. The results demonstrate the potential of multispectral FLIM with objective image analysis as a noninvasive tool to guide comprehensive oral examination.

Evaluation of expression of the PTEN gene, oestrogen and progesterone receptors as diagnostic and predictive factors in endometrial cancer

Endometrial cancer belongs to the commonest malignancy in females after breast cancer, malignant neoplasm of female genitals in Europe and North America but there is still not significant improvement as far as the curability of this neoplasm is concerned, especially its advanced forms. That is why there is need to define new factors that could be not only diagnostic but also predictve factors. In present study we analyzed the mRNA PTEN expression by quantitative real-time polymerase chain reaction (Q-PCR) in 123 women of endometrial carcinoma and 14 women of control group. Moreover we assessed oestrogen (ER) and progesterone receptors (PgR) in all cases. We defined the correlation between expression of PTEN gene and receptors and between PTEN expression and maturity grade of cancer. Neoplasm advancement grade G1 was diagnosed in 82.11 % of patients (n = 101), G2 in 9.76 % of patients (n = 12) and G3 in 8.13 % of patients (n = 10). Presence of ER and PgR and decreased expression of PTEN gene was found in majority of patients with endometrial cancer (79.12 % and 59.34 % respectively) and the most numerous group was with weak expression of ER and strong expression of PgR. There was no statistically significant difference in gene expression depending on receptors expression nor maturity grade of cancer (p > 0.05). Evaluation of expression of PTEN gene may turn out to be a very useful tool aimed at qualifying patients for different therapies of endometrial cancer and at searching of new diagnostic and therapeutic methods of this cancer independently on its receptor status nor maturity grade of cancer.

A matter of life, death and diseases: mitochondria from a proteomic perspective

Mitochondria are highly ordered, integrated organelles that energize cellular activities and contribute to programmed death by initiating disciplined apoptotic cascades. This review seeks to clarify our understanding of mitochondrial structural-functional integrity beyond the resolved nuclear genome by unraveling the dynamic mitochondrial proteome and elucidating proteome/genome interplay. The roles of mechanochemical coupling between mitoskeleton and cytoskeleton and crosstalk with other organelles in orchestrating cellular outcomes are explained. The authors also review the modulation of mitochondrial-related oxidative stress on apoptosis and cancer development and the context is applied to interpret pathogenetic events in neurodegenerative disorders and cardiovascular diseases. The accumulated proteomics evidence is used to describe the integral role that mitochondria play and how they influence other intracellular organelles. Possible mitochondrial-targeted therapeutic interventions are also discussed.

Type II diabetes increases mitochondrial DNA mutations in the left ventricle of the Goto-Kakizaki diabetic rat

Mitochondrial dysfunction has a significant role in the development of diabetic cardiomyopathy. Mitochondrial oxidant stress has been accepted as the singular cause of mitochondrial DNA (mtDNA) damage as an underlying cause of mitochondrial dysfunction. However, separate from a direct effect on mtDNA integrity, diabetic-induced increases in oxidant stress alter mitochondrial topoisomerase function to propagate mtDNA mutations as a contributor to mitochondrial dysfunction. Both glucose-challenged neonatal cardiomyocytes and the diabetic Goto-Kakizaki (GK) rat were studied. In both the GK left ventricle (LV) and in cardiomyocytes, chronically elevated glucose presentation induced a significant increase in mtDNA damage that was accompanied by decreased mitochondrial function. TTGE analysis revealed a number of base pair substitutions in the 3' end of COX3 from GK LV mtDNA that significantly altered the protein sequence. Mitochondrial topoisomerase DNA cleavage activity in isolated mitochondria was significantly increased in the GK LV compared with Wistar controls. Both hydroxycamptothecin, a topoisomerase type 1 inhibitor, and doxorubicin, a topoisomerase type 2 inhibitor, significantly exacerbated the DNA cleavage activity of isolated mitochondrial extracts indicating the presence of multiple functional topoisomerases in the mitochondria. Mitochondrial topoisomerase function was significantly altered in the presence of H2O2 suggesting that separate from a direct effect on mtDNA, oxidant stress mediated type II diabetes-induced alterations of mitochondrial topoisomerase function. These findings are significant in that the activation/inhibition state of the mitochondrial topoisomerases will have important consequences for mtDNA integrity and the well being of the diabetic myocardium.

Mitochondrial DNA mutations in pancreatic cancer

BACKGROUND

Somatic mutations of mitochondrial DNA (mtDNA) are increasingly being recognized in many human cancers, but automated sequencing of 16.5 kb of DNA poses an onerous task. We have recently described an oligonucleotide microarray (MitoChip) for rapid and accurate sequencing of the entire mitochondrial genome (Zhou et al., J Mol Diagnostics, 8: 9_14, 2006), greatly facilitating the analysis of mtDNA mutations in cancer. In this report, we perform a comprehensive cataloging of somatic mutations in the mitochondrial genome of human pancreatic cancers using our novel array-based approach.

MATERIALS AND METHODS

MitoChip analysis was performed on DNA isolated from 15 histologically confirmed resection specimens of pancreatic ductal adenocarcinomas. In all cases, matched nonneoplastic pancreatic tissue was obtained as germline control for mtDNA sequence. DNA was extracted from snap-frozen cryostat-embedded specimens and hybridized to the sequencing microarray after appropriate polymerase chain reaction amplification and labeling steps. The vast majority of somatic mutational analyses of mtDNA in human cancers utilize lymphocyte DNA as germline control, without excluding the potential for organ-specific polymorphisms. Therefore, we also examined a series of 15 paired samples of DNA obtained from nonneoplastic pancreata and corresponding EBV-immortalized lymphoblastoid cell lines to determine whether lymphocyte DNA provides an accurate surrogate for the mtDNA sequence of pancreatic tissue.

RESULTS

We sequenced 497,070 base pairs of mtDNA in the 15 matched samples of pancreatic cancer and nonneoplastic pancreatic tissue, and 467,269 base pairs (94.0%) were assigned by the automated genotyping software. All 15 pancreatic cancers demonstrated at least one somatic mtDNA mutation compared to the control germline DNA with a range of 1-14 alterations. Of the 71 somatic mutations observed in our series, 18 were nonsynonymous coding region alterations (i.e., resulting in an amino acid change), 22 were synonymous coding region alterations, and 31 involved noncoding mtDNA segments (including ribosomal and transfer RNAs). Overall, somatic mutations in the coding region most commonly involved the ND4, COI, and CYTB genes; of note, an A-G transition at nucleotide position 841 in the 12sRNA was observed in three independent samples. In the paired analysis of nonneoplastic pancreata and lymphoblastoid cell line DNA, 14 nucleotide discrepancies were observed out of 226,876 nucleotide sequences (a concordance rate of 99.99%), with 9 samples demonstrating a perfect match across all bases assigned.

CONCLUSIONS

Our findings confirm that somatic mtDNA mutations are common in pancreatic cancers, and therefore, have the potential to be a clinically useful biomarker for early detection. Further, our studies confirm that lymphocyte DNA is an excellent, albeit not perfect, surrogate for nonneoplastic pancreatic tissues in terms of being utilized as a germline control. Finally, our report confirms the utility of a high-throughput array-based platform for mtDNA mutational analyses of human cancers.

Detection of mitochondrial biomarkers in eutopic endometria of endometriosis using surface-enhanced laser desorption/ionization time-of-flight mass spectrometry

OBJECTIVES

To detect specific mitochondrial proteins in eutopic endometrial samples from women with and without endometriosis and to build diagnostic models.

DESIGN

Eutopic endometrial samples from women with endometriosis (excluding adenomyosis) and women with benign indications as control were studied by using surface-enhanced laser desorption/ionization time-of-flight mass spectrometry protein-chip technology. After finding the biomarkers, the diagnostic model was evaluated and validated by leave-one cross-validation.

SETTING

Collaborative investigation in an academic research environment.

PATIENT(S)

Twenty-four patients with endometriosis (excluding adenomyosis) and 29 patients with benign indications as control.

INTERVENTION(S)

Surgical excision of eutopic endometrial biopsy of patients with endometriosis and controls.

MAIN OUTCOME MEASURE(S)

Mitochondrial protein expression.

RESULT(S)

Seventy-eight qualified mitochondrial protein peaks were detected, ten of them had a significant difference. Three combined potential biomarkers, with mass-to-charge ratios (m/z) of 15,334, 15,128, and 16,069, were found, and the diagnostic system distinguished endometriosis from control samples with a specificity of 86.2% and a sensitivity of 87.5%.

CONCLUSION(S)

We discovered potential mitochondrial biomarkers of eutopic endometrium in endometriosis and set up a diagnostic model. Further identification of the proteins we found will help to explain pathology, new diagnoses, and therapeutic approaches for endometriosis.

Differences in mitochondrial proteins in the eutopic endometrium of patients with adenomyosis and endometriosis identified using surface-enhanced laser desorption/ionization time-of-flight mass spectrometry

Adenomyosis and endometriosis have a similar pathogenesis; indeed, adenomyosis has been considered by some as a variant of endometriosis ('internal endometriosis'). This study aimed to detect differences in mitochondrial proteins in eutopic endometrial samples from women with adenomyosis (n = 13) and endometriosis (n = 24), and from control patients (n = 29) using surface-enhanced laser desorption/ionization time-of-flight mass spectrometry (SELDI-TOF-MS) protein chip technology. A total of 82 and 78 mitochondrial protein peaks were found in adenomyosis and endometriosis individuals, respectively. Of these, 14 were common to women with adenomyosis and women with endometriosis, although only one of these (mass-to-charge [m/z] ratio 3499) was significantly different between the adenomyosis and endometriosis groups. It is concluded that, compared with control patients, there are differences in the mitochondrial proteins isolated from the eutopic endometrium of patients with adenomyosis and those with endometriosis. Although the changes in mitochondrial proteins in eutopic endometrium from patients with adenomyosis and endometriosis were largely similar, significant differences were also detected. Further identification of these proteins and elucidation of the differences will help towards the differential diagnosis of adenomyosis and endometriosis and new therapeutic approaches.

Pathogenesis of lung cancer signalling pathways: roadmap for therapies

Lung cancer is the major cancer killer worldwide, and 5-yr survival is extremely poor (<or=15%), accentuating the need for more effective therapeutic strategies. Significant advances in lung cancer biology may lead to customised therapy based on targeting specific genes and pathways. The main signalling pathways that could provide roadmaps for therapy include the following: growth promoting pathways (Epidermal Growth Factor Receptor/Ras/PhosphatidylInositol 3-Kinase), growth inhibitory pathways (p53/Rb/P14(ARF), STK11), apoptotic pathways (Bcl-2/Bax/Fas/FasL), DNA repair and immortalisation genes. Epigenetic changes in lung cancer contribute strongly to cell transformation by modifying chromatin structures and the specific expression of genes; these include DNA methylation, histone and chromatin protein modification, and micro-RNA, all of which are responsible for the silencing of tumour suppressor genes while enhancing expression of oncogenes. The genetic and epigenetic pathways involved in lung tumorigenesis differ between smokers and nonsmokers, and are tools for cancer diagnosis, prognosis, clinical follow-up and targeted therapies.

High rate of mutation in mitochondrial DNA displacement loop region in human colorectal cancer

PURPOSE

Mitochondrial DNA mutations are found in many kinds of human cancer and the 1.1 kb displacement loop region has been identified as a "hot spot" for mutation in mitochondrial DNA of tumors. This study evaluated the mutation frequencies in hypervariable regions of mitochondrial displacement loop in patients with colorectal cancer.

METHODS

We examined the frequency of mutations in the mitochondrial DNA displacement loop region of 40 colorectal cancer samples in comparison to 150 samples from people without any type of familial cancer history, by automated DNA sequencing. Alignment was made with the revised Cambridge Reference Sequence and any differences recorded as single base substitution, insertions, and deletions.

RESULTS

Our results showed that the rate of displacement loop variations was higher in colorectal cancer patients than controls. Nineteen single nucleotide polymorphisms were found; among them eighteen occurred in the displacement loop region.

CONCLUSIONS

Mutations in mtDNA D-loop region probably do not cause colorectal cancer but are more likely to be epiphenomena; patients with the high mtDNA variants are at a higher risk of colorectal cancer.

Quantification of mitochondrial DNA (mtDNA) damage and error rates by real-time QPCR

Mitochondrial dysfunction has reported in several diseases including diabetes, cancer, skeletal muscle disorders and neurodegenerative diseases such as Wolfram syndrome. Several different methods have evolved to study mtDNA damage including Southern blotting, 8-oxoG damage, or a comprehensive scanning of the mitochondrial genome by RFLP or TTGE analyses. However these approaches require large amounts of DNA or are labor intensive. The use of polymerase amplification of long DNA products (LRPCR) has been described by several groups and more recently summarized by Van Houten's group. The underlying basis use of DNA polymerases capable of generating long DNA products and the rationale is that any lesion (strand breaks, base modifications, apurinic sites) will stop a thermostable DNA polymerase. In this method, band density of the PCR product is quantified either by Southern blotting or binding of a fluorescent dye. Although the latter approach still has some limited use in the study gene expression, it is semi-quantitative and realtime PCR analysis has largely supplanted it. Direct application of real-time PCR to LRPCR has been made difficult because of low processivity and polymerization rates of the DNA polymerases used and SYBR green inhibition of DNA amplification. We have modified the LRPCR protocol to use the commercially available PfuUltra() II Fusion HS DNA Polymerase for real-time determination of mitochondrial DNA amplification as a means to simplify and improve of the accuracy for quantification of mtDNA damage.

Altered expression of 12S/MT-RNR1, MT-CO2/COX2, and MT-ATP6 mitochondrial genes in prostate cancer

BACKGROUND

Prostate cancer is one of the commonest cancers worldwide and is responsible for nearly 6% of all male cancer deaths. Despite this relevance, the mechanisms involved in the development and progression of this malignancy remain unknown. The involvement of polypeptides of the mitochondrial respiratory chain, the Krebs cycle and the glutathione antioxidant system in this type of cancer has been previously described, although no publication has focused on the expression of mitochondrial genes in the prostate of PCa patients.

METHODS

We have determined by reverse transcription-quantitative PCR (RT-qPCR) the relative amount of the transcripts of eight mitochondrial genes (MT-ND2, MT-ND4, MT-ND6, MT-CYB, 12S/MT-RNR1, 16S/MT-RNR2, MT-CO2/COX2, MT-ATP6), and four nuclear genes (COX11, GSR, CS, ACO2), all of them key players in the normal metabolism of mitochondria. Additionally we analyzed the expression of Cyclophilin A (PPIA).

RESULTS

We observed differential expression of mitochondrial 12S/MT-RNR1, MT-CO2/COX2, and MT-ATP6 transcripts in tumor samples when compared to their paired normal samples.

CONCLUSIONS

The amount of mitochondrial 12S/MT-RNR1, MT-CO2/COX2, and MT-ATP6 transcripts is significantly decreased in tumor samples when compared to their paired normal sample, suggesting that mitochondrial gene expression is altered in PCa.

Molecular biomarkers for cancer detection in blood and bodily fluids

Cancer is a major and increasing public health problem worldwide. Traditionally, the diagnosis and staging of cancer, as well as the evaluation of response to therapy have been primarily based on morphology, with relatively few cancer biomarkers currently in use. Conventional biomarker studies have been focused on single genes or discrete pathways, but this approach has had limited success because of the complex and heterogeneous nature of many cancers. The completion of the human genome project and the development of new technologies have greatly facilitated the identification of biomarkers for assessment of cancer risk, early detection of primary cancers, monitoring cancer treatment, and detection of recurrence. This article reviews the various approaches used for development of such markers and describes markers of potential clinical interest in major types of cancer. Finally, we discuss the reasons why so few cancer biomarkers are currently available for clinical use.

Mitochondrial DNA mutations in preneoplastic lesions of the gastrointestinal tract: a biomarker for the early detection of cancer

Background

Somatic mutations of mitochondrial DNA (mtDNA) are common in many human cancers. We have described an oligonucleotide microarray ("MitoChip") for rapid sequencing of the entire mitochondrial genome (Zhou et al, J Mol Diagn 2006), facilitating the analysis of mtDNA mutations in preneoplastic lesions. We examined 14 precancerous lesions, including seven Barrett esophagus biopsies, with or without associated dysplasia; four colorectal adenomas; and three inflammatory colitis-associated dysplasia specimens. In all cases, matched normal tissues from the corresponding site were obtained as germline control. MitoChip analysis was performed on DNA obtained from cryostat-embedded specimens.

Results

A total of 513,639 bases of mtDNA were sequenced in the 14 samples, with 490,224 bases (95.4%) bases assigned by the automated genotyping software. All preneoplastic lesions examined demonstrated at least one somatic mtDNA sequence alteration. Of the 100 somatic mtDNA alterations observed in the 14 cases, 27 were non-synonymous coding region mutations (i.e., resulting in an amino acid change), 36 were synonymous, and 37 involved non-coding mtDNA. Overall, somatic alterations most commonly involved the COI, ND4 and ND5 genes. Notably, somatic mtDNA alterations were observed in preneoplastic lesions of the gastrointestinal tract even in the absence of histopathologic evidence of dysplasia, suggesting that the mitochondrial genome is susceptible at the earliest stages of multistep cancer progression.

Conclusion

Our findings further substantiate the rationale for exploring the mitochondrial genome as a biomarker for the early diagnosis of cancer, and confirm the utility of a high-throughput array-based platform for this purpose from a clinical applicability standpoint.

Building the power house: recent advances in mitochondrial studies through proteomics and systems biology

The emerging field of systems biology seeks to develop novel approaches to integrate heterogeneous data sources for effective analysis of complex living systems. Systemic studies of mitochondria have generated a large number of proteomic data sets in numerous species, including yeast, plant, mouse, rat, and human. Beyond component identification, mitochondrial proteomics is recognized as a powerful tool for diagnosing and characterizing complex diseases associated with these organelles. Various proteomic techniques for isolation and purification of proteins have been developed; each tailored to preserve protein properties relevant to study of a particular disease type. Examples of such techniques include immunocapture, which minimizes loss of posttranslational modification, 4-iodobutyltriphenylphosphonium labeling, which quantifies protein redox states, and surface-enhanced laser desorption ionization-time-of-flight mass spectrometry, which allows sequence-specific binding. With the rapidly increasing number of discovered molecular components, computational models are also being developed to facilitate the organization and analysis of such data. Computational models of mitochondria have been accomplished with top-down and bottom-up approaches and have been steadily improved in size and scope. Results from top-down methods tend to be more qualitative but are unbiased by prior knowledge about the system. Bottom-up methods often require the incorporation of a large amount of existing data but provide more rigorous and quantitative information, which can be used as hypotheses for subsequent experimental studies. Successes and limitations of the studies reviewed here provide opportunities and challenges that must be addressed to facilitate the application of systems biology to larger systems.