OBJECTIVETo study mRNA and protein expression of HOXA5 gene in breast carcinoma, to correlate the expression of HOXA5 gene with clinicopathologic parameters and to explore the possible role of HOXA5 gene in carcinogenesis, progression and metastasis of breast carcinoma.

METHODSTaqMan real-time reverse transcriptase-polymerase chain reaction (RT-PCR) was applied on 60 cases of primary breast carcinoma and 24 cases of benign mammary lesions in order to detect mRNA expression of HOXA5 gene. Immunohistochemical study using polyclonal antibody against HOXA5 was also performed. Statistical analysis was carried out to analyze the correlation between HOXA5 gene expression and various clinical parameters in these breast cancer patients.

RESULTS(1) The relative expression level of HOXA5 mRNA ranged from 0.73 to 193.07 (average = 20.85) in primary breast carcinoma, in contrast to 5.42 to 81.91 (average = 30.94) in benign mammary lesions. Compared with benign mammary lesions, a significant reduction in expression of HOXA5 mRNA was noted in primary breast carcinoma (P < 0.01). (2) There was a decreased or completely diminished HOXA5 protein expression in breast carcinoma. (3) HOXA5 mRNA expression was significantly lower in lymph node-positive cases, when compared with that in lymph node-negative cases (P < 0.05). A significant difference of HOXA5 protein expression was also observed in both groups (P < 0.01). Immunohistochemical staining of HOXA5 was either negative or weakly positive in lymph node-positive cases. On the other hand, moderately or strongly positive HOXA5 staining was noted in lymph node-negative cases. (4) Neither mRNA nor protein expression of HOXA5 gene correlated with clinicopathologic parameters such as age of patients, size of tumor, clinical stage, pathologic subtype or histologic grade (P > 0.05).

CONCLUSIONSDisordered expression of HOXA5 gene may play a role in the carcinogenesis of breast cancer. Reduced expression of HOXA5 gene may be related to the metastatic potential of breast carcinoma cells.