MITOCHONDRIAL DNA 4977 bp DELETION IN CHRONIC CERVICITIS AND CERVIX CANCERS
Kara M, Tatar A, Borekci B, Dagli F, Oztas S
*Corresponding Author: Murat Kara M.D., Department of Genetics, School of Medicine, Firat University, Universite cad. No. 2, 23119 Elazig, Turkey; Tel: +90-424-233-35-55/1938; Fax: +90-424-238-80-96; E-mail: drmuratkara@hotmail.com
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DISCUSSION

Mutations in mitochondrial protein genes are the reason of not only neurodegenerative diseases but also ophthalmological and hematological diseases [12]. Studies demonstrating the relationship of mtDNA mutations with cancer and infections were conducted in many different patient groups [10,18]. Accumulation of mtDNA mutations is directly related to ageing and the development of degenerative diseases. It has been shown that the 4977 bp deletion accumulated in tissues such as brain, skeletal and cardiac muscle increases with age [19]. In this study, we demonstrated the relationship of 4977 bp mtDNA deletions with chronic cervicitis and cervix cancer. Liu et al. [20] determined 60.0% mtDNA mutations in malignant ovarian tissues. The rate of mtDNA mutations were 68.8 and 25.0%, respectively, for malignant tumors and benign tumors. Wu et al. [17] in their study on 31 gastric cancer patients, found the 4977 bp deletion in normal gastric tissues in 17 (55.0%) of 31 patients. They also found that only three (10.0%) of all gastric cancer samples carried mtDNA deletions. These fi ndings suggest that the 4977 bp deletions accumulated in less frequency in gastric cancer tissues [17]. Cervical cancer is the second most common cause of cancer deaths after breast cancer in women and it comprises 10.0% of all cancer deaths [21]. There are few studies investigating the relationship between mtDNA mutations and cervix cancer [2,22]. In our study, 9.5% heteroplasmic and homoplasmic mtDNA 4977 bp deletions were observed in cervix cancer. In addition, the ages of two patients with mtDNA 4977 bp homoplasmic deletion were 73 and 79 years. These older ages suggest that the age-dependent accumulation of mtDNA deletions is one of the reasons of the frequent homoplasmy in cervical cancer. Secondly, these patients might be exposed to more infections because of their advanced age, and mitochondrial ROS production might be increased. Thus, chronic infl ammation via ROS production may lead to mtDNA mutations and accumulation of mutant mtDNA in cell. The reason for the lack of deletions in other patients might be that cells undergo apoptosis when mitochondrial mutations exceed threshold value [17]. The evidence suggests that the effects of ROS on the pathogenesis of chronic diseases including cancer vary [23]. Although cells have antioxidant systems against ROS-dependent oxidative damage, oxidative damages accumulate during life and this accumulation leads to damage in DNA, proteins and lipids. Therefore, it is suggested that oxidative stress has an important role in the development of age-dependent diseases such as neurodegenerative disorders, arthritis, arteriosclerosis and cancer [24]. A study by Canakci et al. [25] found that 24 (80.0%) of 30 chronic periodontitis patients had the 4881 bp mtDNA deletion. They suggested that increased ROS production due to infection in chronic periodontitis may be related to 4881 bp mtDNA deletion [25]. In our study, patients with chronic cervicitis had a higher frequent heteroplasmic mtDNA 4977 bp deletions. This fi nding supports the hypothesis that increased ROS production during chronic infl ammation in cervix tissues leads to mtDNA mutations. However, the minimum threshold effect should be exceeded by the emergence of clinical fi ndings and dysfunction in tissues [6,26]. This idea may show that mutation rate is important in disease expression and in defi ning mitochondrial diseases. This is the fi rst study that uses the mtDNA 4977 bp deletion in understanding of pathogenesis in patients with chronic cervicitis and cervix cancer. Investigating other mtDNA mutations in these patient groups may gain insight for clinical approaches. Declaration of Interest. The authors report no confl icts of interest. The authors alone are responsible for the content and writing of this article.



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