Expression of DNA methyltransferase 1 mRNA in patients of endemic arsenism and its clinical significances

Abstract

Objective To investigate the transcription and expression of DNA methyltransferase 1 (DNMT1) mRNA in endemic arsenism patients by burning coal usage,to probe its effects on the development and carcinogenesis of arsenism. Methods In 2008,68 arsenism patients(including 24 mild cases,28 moderate cases and 16 severe cases) were selected in the areas with endemic arsenism according to Standarding of Diagnosis for Endemic Arsenism from Xingren county,Guizhou province. Among the subjects,40 cases were diagnosed by pathological methods,and they were divided into general pathological changes(20),precancerous(14) and cancerous group(6). Tweleve kilometer away from the endemic arsenism area,23 controls were selected in Daguoduo village (non-arsenism exposure). Under the principle of informed consent,blood samples were collected from individuals. The mRNA expression of DNMTI was detected by real-time quantitative reverse transcription polymerase chain reaction(FQ-PCR). At the same time,skin tissue samples were collected from the voluntary surgical treatment patients with endemic arsenism (total 61 cases,including 34 general pathological changes cases,21 precancerous cases and 6 cancerous cases) and from the control(15 cases). DNMT1 protein was detected by immunohistochemical method.Results Average level of DNMT1 mRNA were 0.221 83±0.595 09,0.246 11±0.509 79 and 0.389 27±0.411 33 respectively among mild,moderate and severe arsenism group. DNMT1 mRNA level of mild and moderate group were obviously lower than the control group(0.695 95±0.463 98,all P < 0.01). The mRNA average level of DNMT1 were 0.320 64±0.547 46,0.313 09±0.529 13 and 0.159 07±0.342 56 individually among general pathological changes,precancerous and cancerous group,which were obviously lower than the control group(0.695 95±0.463 98,all P < 0.05). The expression rates of DNMT1 protein in skin were 88.24%(30/34),100%(21/21) and 100% (6/6) among general pathological changes,precancerous and cancerous group were higher than the control group [0(0/15),all P < 0.01],and the extent of expression gradually increased with the aggravation of skin damage(r,= 0.740,P < 0.01). Conclusions DNMT1 participated in the development of the arsenism. High expression of its protein was an early event during the process of the arsenism. DNMT1 may be the new target markers for early diagnosis and treatment of arsenism. Key words: Arsenic poisoning; DNA methyltransferase 1 ; Gene expression