Expression of High Mobility Group Protein Family [HMGI(Y) and HMGI-C] in Human Breast Cancer

Breast cancer results from the progressive accumulation of a series of genetic alterations leading to neoplastic transformation. Recent studies have shown that a) HMGI proteins play an important role in the regulation of chromatin structure and function and b) the expression of aberrant HMGI [HMGI(Y) and HMGI-C] proteins is generally correlated with malignant tumors. We tried to define the function of HMGI in carcinogenesis and we compare the expression of HMGI with known clinicopathologic parameters.

Using Reverse transcriptase-polymerase chain reaction (RT-PCR), we determined the expression of HMGI mRNA in 60 primary malignant tumors, 20 normal tissue, 13 benign tumors, and four ductal carcinoma in situ. Immunohistochemical staining of p53, ER, PR, and clinicopathological parameters were evaluated.

The expression of the HMGI(Y) mRNA increased more in malignant tissue (90%, 54 of 60) than in benign (76.9%) and normal (65%) tissues (p=0.031). The expression of HMGI-C mRNA was visible only in malignant (48.4%, 29 of 60) and benign (23.1%, 3 of 13) tumors. The expression of HMGI-C mRNA increased more in malignant tumors than in benign tumors (p<0.001). In invasive ductal tumors (n=50), the expression of HMGI-C mRNA was observed more in high grade tumors (grade 3~81.3%, grade 1, 2~32.4%) (p=0.005). Among the prognostic parameters, only the number of mitotic figures was related to the expression of HMGI-C mRNA (p=0.046).

These results suggest that a) HMGI-C gene may be correlated with the formation of breast tumors and b) the expression of HMGI-C gene may be of pathogenetic and prognostic importance in human breast cancer.