Frequent co-amplification of two different regions on 17q in aneuploid breast carcinomas

Chromosome 17q is highly susceptible to rearrangement mutations in breast c ancer. c-erbB-2 at 17q11.2 similar to q21.1 is frequently amplified, as is a region at 17q22 similar to q24. As a step in the search for the target ge ne(s) of the 17q22-q24 amplification we determined whether the placental la ctogen (PL) genes at 17q23 were amplified in 59 breast carcinomas. These ge nes were selected as their upregulation could theoretically be involved in breast cancer tumorigenesis. Amplification of the PL genes, and also of c-e rbB-2, was detected using semi-quantitative PCR. The reliability of this me thod was confirmed since c-erbB-2 results obtained using PCR, Southern blot ting and immunohistochemistry were in good agreement. The PL genes were amp lified in 13 (22%) of the tumors. Furthermore, the PL and c-erbB-2 genes we re frequently co-amplified although there is a nonamplified region between them. Expression of PL was investigated in 26 tumors and was detected in 16 of these cases including all 10 tumors with amplification of the PL genes. The tumors with PL gene amplification were all aneuploid. A trend was seen towards an increased incidence of lymph node involvement for tumors with a mplification of the PL genes and fur tumors with co-amplification of PL and c-erbB-2, which suggests a possible association with high malignancy. (C) 2001 Elsevier Science Inc. All rights reserved.