RESUMEN
<p><b>OBJECTIVE</b>To study the BRCA1 mutations in patients with early-onset breast cancer and their affected relatives in Guangdong province and explore the relationship between BRCA1 mutation and the expressions of estrogen receptor(ER), progesterone receptor(PR), HER2 and ALN.</p><p><b>METHODS</b>From 58 patients with early-onset breast cancer and their affected relatives, the genomic DNA was extracted from the peripheral blood mononuclear cells and the coding regions of the BRCA1 gene was amplified using polymerase chain reaction. BRCA1 gene mutations were screened by denaturing high performance liquid chromatography (DHPLC) and subsequent direct DNA sequencing. The expression of ER, PR, HER2 and ALN were detected with immunohistochemistry and their relations with the gene mutation were analyzed.</p><p><b>RESULTS</b>Disease-related BRCA1 mutations were detected in 2 of the 58 patients, who were younger than 35 years old, including 1 with a novel splice-site mutation (IVS5-1 G-->A). No association was found between this novel mutation and the expressions of ER, PR, HER2 and ALN.</p><p><b>CONCLUSION</b>The incidence of BRCA1 mutation is significantly lower in patients with early-onset breast cancer and their affected relatives in Guangdong province than in the Western populations. The novel mutation identified in BRCA1 gene may represent a mutation characteristic of the patients in Guangdong province. BRCA1 gene mutations may not have any relation with the expression of ER, PR, HER2 and ALN.</p>