The ERBB2 gene, previously called Her2-neu, is a proto-oncogene located on human chromosome 17q21.1. It encodes the human epidermal growth factor receptor-2, a tyrosine kinase. This transmembrane cell surface protein is significantly over expressed in many different human cancers, among them breast, ovarian and cervical cancers. Overexpression is most often due to an increased copy number of the ERBB2 gene.
This probemix P004-C1 ERRB2 contains four MLPA probes recognizing different sequences of the ERBB2 gene. In addition, it contains 27 probes for other genes on chromosome 17, including BRCA1, genes close to the centromere and genes close to ERBB2, such as TOP2A. TOP2A encodes for human topoisomerase 2. Overexpression of TOP2A, due to co-amplification with ERBB2, may influence the response of tumors to certain treatments. In addition, 6 probes targeting possibly affected genes on other chromosomes are included: two probes for EGFR, two for the ESR1 gene encoding the estrogen receptor and two for BRCA2. A deletion of either the BRCA1 and/or the BRCA2 probes indicates a genetic predisposition for breast cancer. Finally, 12 reference probes have been included, all of which are located in chromosomal regions which have been found to be silent regions in CGH experiments. However, it is possible that one or more of reference probes is altered in tumor samples.
Amplification of the EGFR gene has been reported in various tumors, including breast tumors. Co-amplification of only ERBBB2 and the chromosome 17 centromere region has been observed in some samples that were expected to have polysomy 17 (based on a FISH centromere-specific probe).