title: Association between mitochondrial C-tract alteration and tobacco exposure in oral precancer cases.
abstract: BACKGROUND
  Tobacco exposure is a known risk factor for oral cancer. India is home to oral cancer epidemic chiefly due to the prevalent use of both smoke and smokeless tobacco. To reduce the related morbidity early detection is required. The key to this is detailing molecular events during early precancer stage. Mitochondrion is an important cellular organelle involved in cell metabolism and apoptosis. Mitochondrial dysfunction is thought to be the key event in oncogenesis. Last decade has seen a spurt of reports implicating mitochondrial mutations in oral carcinogenesis. However, there are few reports that study mitochondrial deoxyribonucleic acid (mtDNA) changes in oral precancer. This study aims to understand and link effect of tobacco exposure on mtDNA in oral precancer cases.
  
  
  METHODS
  A total of 100 oral precancer cases of which 50 oral leukoplakia and 50 oral submucous fibrosis were recruited in the study and a detailed questionnaire were filled about the tobacco habits. Their tissue and blood samples were collected. Total genomic DNA was isolated from both sources. Mitochondrial C-tract was amplified and bidirectional sequencing was carried out. Mutations were scored over matched blood DNA.
  
  
  RESULTS
  There was a significant association between the presence of mitochondrial C-tract alteration and duration of tobacco exposure. The probability increased with increasing duration of tobacco consumption. The risk of having this alteration was more in chewers than in smokers.
  
  
  CONCLUSIONS
  Tobacco in both form, chewable and smoke, is oncogenic and causes early changes in mitochondrial genome and chances increases with increasing duration of tobacco consumption.
authors.affiliation: Department of Oral and Maxillofacial Surgery, King George's Medical University, Lucknow, Uttar Pradesh, India.
authors.forename: Rahul
authors.initials: R
authors.lastname: Pandey
authors.affiliation: Department of Oral and Maxillofacial Surgery, King George's Medical University, Lucknow, Uttar Pradesh, India.
authors.forename: Divya
authors.initials: D
authors.lastname: Mehrotra
authors.affiliation: Department of Biochemistry, King George's Medical University, Lucknow, Uttar Pradesh, India.
authors.forename: Abbas Ali
authors.initials: AA
authors.lastname: Mahdi
authors.affiliation: Cancer Research Institute, ACTREC, Tata Memorail Centre, Mumbai, Maharashtra, India.
authors.forename: Rajiv
authors.initials: R
authors.lastname: Sarin
authors.affiliation: Cancer Research Institute, ACTREC, Tata Memorail Centre, Mumbai, Maharashtra, India.
authors.forename: Pradnya
authors.initials: P
authors.lastname: Kowtal
authors.affiliation: Developmental Toxicity, IITR, Lucknow, Uttar Pradesh, India.
authors.forename: Shailendra S
authors.initials: SS
authors.lastname: Maurya
authors.affiliation: Developmental Toxicity, IITR, Lucknow, Uttar Pradesh, India.
authors.forename: Devendra
authors.initials: D
authors.lastname: Parmar
keywords: D loop; leukoplakia; oral submucous fibrosis; polycytosine tract; tobacco