Abstract:

Objective

To detect the aberrant methylation of fragile histidine triad(FHIT) gene and the expression of the corresponding mRNA and proteins in breast tumor tissue and normal breast tissue, explore the role of FHIT gene in the development of breast cancer and provide experimental evidence for biotherapy and prognosis.

Methods

Immunohistochemical SP method, reverse transcription polymerase chain reaction (RT-PCR)and methylation specific PCR (MSP) were used to detect the protein and mRNA expressions of FHIT in 50 cases of breast tumor tissues and adjacent normal tissues over 5 cm away from the margin of tumor. The relationship between FHIT expression and clinic-pathological parameters were analyzed by chi-square test. The correlation between FHIT methylation and the FHIT mRNA and protein expression was processed by Spearman analysis.

Results

Immunohistochemical staining showed that FHIT protein was mainly located in the cytoplasma of breast cells, being brown granules. The positive expression ratios of FHIT were 32.0% in breast tumor tissue and 88.0% in normal breast issue, respectively. The difference was significant (P ＜0.05). RT-PCR results showed that FHIT mRNA was expressed in both breast tumor tissue and normal tissue. The ratio of FHIT band optical density (OD) value to OD value of β-actin was 0.1081±0.0128 in breast tumor tissue, which was significantly lower than 0.2088±0.0137 in normal tissue (P＜0.05). It indicated that the expression of FHIT was decreased in breast tumor tissue. MSP results showed that FHIT methylation rate were 46.0%(23/50)in tumor tissue, 12.0%(6/50)in normal tissues. The difference was statistically significant (P＜0.05). FHIT methylation rate was correlated with lymph node metastasis (P ＜0.05), not related with tumor size, histological grade, TNM stage (P ＞0.05).

Conclusions

Methylation of FHIT gene in breast cancer can significantly downregulate FHIT mRNA and protein expression.

Key words: Breast neoplasms, Methylation, FHIT