Expression And DNA Methylation Of GADD45G Gene In Meibomian Cell Carcinoma

Meibomian cell carcinoma(MCC) is rare and aggressive eyelid tumor. It accounts for 31.7% of all malignant eyelid tumors. A high rate of epidemic of this disease center on the age of 65 years old, also meibomian cell carcinoma has been described in young patients. MCC is associated with a high incidence of locoregional recurrence in skin and lymph nodes but also with distant metastases, resulting in the higher mortality. MCC usually misdiagnosed by chronic conjunctivitis and chalazion. Early diagnosis and treatment is important for the prognosis of this disease. Recently study suggests that epigenetics play a vital role in the process of the tumors occurrence and development. The detection of aberrant DNA methylation in tumor tissue and blood of tumor patients indicated that DNA methylation may be served as a new sensitive indicator of tumor formation, which may be used in the prevention and treatment of cancer.The GADD45(growth arrest and DNA- damage 45) gene family encodes three structurally related growth arrest-and DNA damage-inducible protein, GADD45 A, GADD45 B, GADD45 G. All of the three genes were identified that bound to an N-terminal domain of MTK1. These proteins can activate MTK1 kinase activity, further to induce p38/JNK activation and apoptosis. Recent study indicated that GADD45 family is an important regulator in apoptosis pathways in cancer, and the member of GADD45 G paly a very important role in the NF-B-mediated pathway. We found the expression of GADD45 G in normal tissue, but lower in tumor tissue. Aberrant DNA hypermethylation of GADD45 G was founded in a variety of tumors. Aberrant DNA hypermethylation of GADD45 G may be one of the important reasons that lead to low expression of this gene in a variety of tumors. At present, the expression and aberrant DNA hypermethylation of GADD45 G in MCC have not been reported. In our study, the aim of this project is to research the expression of MCC, further to provide a valuable target for cure and prevention of this disease.Objective: To detect the protein expression and the methylation status of GADD45 G by Immunohistochemistry method and Methylation specific PCR.Methods:1 Immunohistochemistry method was used to detect the protein expression of GADD45 G in 40 MCC tumor tissues and corresponding normal tissues.2 Methylation specific PCR(MSP) method was used to examine the methylation status of GADD45 G gene in 40 MCC tumor tissues and corresponding normal tissues.3 Analysis the data with SPSS13.0Results:1 The expression of GADD45 g in MCC was decreaseThe protein expression of GADD45 G in 40 tumor specimens(22.5%, 9/40) was significantly lower than that in corresponding normal tissues(82.5%, 33/40)(P =0.000). Furthermore, the protein expression of GADD45 G was not associated with age(P>0.05), gender(P>0.05), TNM stage(P>0.05), recurrence(P>0.05), differentiation(P>0.05).2 DNA hypermethylation of GADD45 G in MCCGADD45G methylation rate of this locus in tumor specimens(62.5%, 25/40) was significantly higher than that in corresponding normal tissues(10%, 4/40)(P =0.000). Furthermore, the methylation rate of GADD45 G was not associated with age(P>0.05), gender(P>0.05), TNM stage(P>0.05), recurrence(P >0.05), differentiation(P >0.05).3 The methylation status of GADD45 G is negative correlation with the positive protein expression of GADD45 G in MCC.The positive protein expression of GADD45 G in tumor tissues with hypermethylation of the gene(6%, 1/25) was significantly lower than that in tumor tissues with unmethylation of the gene(55.3 %, 8/15)(P =0.000).Conclusions:1 The lower protein expression of GADD45 G was associated with MCC. The methylation rate of Cp G loci in GADD45 G gene Promoter region were distinct, indicating the methylation of critical Cp G loci may be one of the main mechanisms that lead to the decreased expression of the gene in MCC.2 The methylation status of GADD45 G had no association with age, gender, TNM stage recurrence and differentiation of MCC patients. Indicating methylation of GADD45 G was no relationship with the development and infiltration of MCC, but has connected with the tumor happened.