title: Human MutL homolog 1 immunoexpression in oral leukoplakia and oral squamous cell carcinoma: A prospective study in Indian population.
abstract: BACKGROUND
  Mammalian mismatch repair system is responsible for maintaining genomic stability during repeated duplications, and human MutL homolog 1 (hMLH1) protein constitutes an important part of it. Various isolated studies have reported the altered expression of hMLH1 in oral leukoplakia (OL) and oral squamous cell carcinoma (OSCC). Research is lacking in the quantitative estimation and comparison of hMLH1 expression in OL and OSCC.
  
  
  OBJECTIVE
  To evaluate, quantify and compare hMLH1 immunoexpression in normal oral mucosa, OL and OSCC.
  
  
  METHODS
  Thirty patients of OL and thirty patients of OSCC formed the study group and thirty patients were included in the control group (normal oral mucosa). Formalin-fixed paraffin wax blocks were prepared from the tissue samples.
  
  
  METHODS
  Immunohistochemistry for hMLH1 was performed, and the total number of positive cells was counted in high-power fields, and based on that percentage positivity of hMLH1 was calculated in all the cases.
  
  
  METHODS
  Kruskal-Wallis andt-test were used.P< 0.05 was considered to be statistically significant.
  
  
  RESULTS
  The mean hMLH1 value in control group, leukoplakia and OSCC was 78.26, 54.33 and 40.97 respectively. hMLH1 immunoexpression showed decreasing indexes from control group to leukoplakia and then further to OSCC. hMLH1 expression was significantly lower in OSCC as compared to leukoplakia. There was no significant correlation of mean hMLH1 expression between different clinical and histopathological stages of leukoplakia and OSCC.
  
  
  CONCLUSIONS
  hMLH1 immunoexpression was inversely related to the degree of dysplasia. These findings suggest that there is a progressive decrease in hMLH1 expression from control to leukoplakia and further to OSCC. Thus, it can be concluded that hMLH1 can be used as a reliable biomarker for malignant transformation.
authors.affiliation: Department of Oral Pathology and Microbiology, Government Dental College and Hospital, Mumbai, Maharashtra, India.
authors.forename: Narendra T
authors.initials: NT
authors.lastname: Chaudhari
authors.affiliation: Department of Oral Pathology and Microbiology, Government Dental College and Hospital, Mumbai, Maharashtra, India.
authors.forename: Jagdish V
authors.initials: JV
authors.lastname: Tupkari
authors.affiliation: Department of Oral Pathology and Microbiology, Government Dental College and Hospital, Mumbai, Maharashtra, India.
authors.forename: Tabita
authors.initials: T
authors.lastname: Joy
authors.affiliation: Department of Oral Pathology and Microbiology, Government Dental College and Hospital, Mumbai, Maharashtra, India.
authors.forename: Manisha S
authors.initials: MS
authors.lastname: Ahire
keywords: Mismatch repair system; oral leukoplakia; oral squamous cell carcinoma