Expression of Xeroderma Pigmentosum Group G (XPG) in Sporadic Breast Carcinoma

Abstract

Xeroderma Pigmentosum Group G (XPG) is one of the proteins involved in nucleotide excision repair, and is related to Xeroderma pigmentosum, a rare hereditary disease characterized by hypersensitivity to ultraviolet light, high incidence of actinic carcinomas and neurological abnormalities. The aim of this study was to investigate the expression of XPG in sporadic human breast carcinoma and to determine whether it's expression was predictive for response to tamoxifenbased chemotherapy and survival in the patients with breast carcinoma. We investigated the expression levels of mRNA and protein of XPG in 43 sporadic human breast carcinomas by real time PCR and immunohistochemical analysis. All the patients were primarily treated with reductive surgery and doxorubicin and tamoxifen-based regimen. XPG expression was observed in 35 of 43 cases (81.4%). The proportion of the cases with high expression level of XPG was 48.8% (21/43 cases). Interestingly, the cases showing the expression of mRNA without detectable levels of protein were observed in 5 of 43 cases (11.6%). The sequence analysis showed one mutation such as deletion at codon117 that leads to a following stop codon. Moreover, patients with high expression levels significantly had a poorer overall survival than those with low expression level (P = 0.048). These results suggest that XPG may be the useful molecular marker to choose the anticancer drugs for tamoxifen-based chemotherapy in human sporadic breast carcinoma.