Oncogene amplification in male breast cancer: analysis by multiplex ligation-dependent probe amplification

Abstract

Gene amplification is an important mechanism for oncogene activation, a crucial step in carcinogenesis. Compared to female breast cancer, little is known on the genetic makeup of male breast cancer, because large series are lacking. Copy number changes of 21 breast cancer related genes were studied in 110 male breast cancers using multiplex ligation-dependent probe amplification. A ratio of >1.3 was regarded indicative for gene copy number gain and a ratio >2.0 for gene amplification. Data were correlated with clinicopathological features, prognosis and 17 genes were compared with a group of female breast cancers. Gene copy number gain of CCND1, TRAF4, CDC6 and MTDH was seen in >40 % of the male breast cancer cases, with also frequent amplification. The number of genes with copy number gain and several single genes were associated with high grade, but only CCND1 amplification was an independent predictor of adverse survival in Cox regression (p = 0.015; hazard ratio 3.0). In unsupervised hierarchical clustering a distinctive group of male breast cancer with poor prognosis (p = 0.009; hazard ratio 3.4) was identified, characterized by frequent CCND1, MTDH, CDC6, ADAM9, TRAF4 and MYC copy number gain. Compared to female breast cancers, EGFR (p = 0.005) and CCND1 (p = 0.041) copy number gain was more often seen in male breast cancer, while copy number gain of EMSY (p = 0.004) and CPD (p = 0.001) and amplification in general was less frequent. In conclusion, several female breast cancer genes also seem to be important in male breast carcinogenesis. However, there are also clear differences in copy number changes between male and female breast cancers, pointing toward differences in carcinogenesis between male and female breast cancer and emphasizing the importance of identifying biomarkers and therapeutic agents based on research in male breast cancer. In addition CCND1 amplification seems to be an independent prognosticator in male breast cancer.Electronic supplementary materialThe online version of this article (doi:10.1007/s10549-012-2051-3) contains supplementary material, which is available to authorized users.

Analysis of copy number changes on chromosome 16q in male breast cancer by multiplex ligation-dependent probe amplification

“…All consecutive cases of surgical breast specimens of invasive male breast cancer from 1986 to 2011 were collected from four different pathology labs in the Netherlands (St. Antonius Hospital, Nieuwegein, Diakonessenhuis Utrecht, University Medical Center Utrecht, and Laboratory for Pathology East Netherlands), as described in more detail previously 1,9 and from three pathology labs in Germany (Paderborn, Cologne, Kassel). Hematoxylin and eosin (HE) slides were reviewed by four experienced observers (PJvD, RK, AM, ML) to confirm the diagnosis and to type and grade according to current standards.…”

“…Negative reference samples (normal breast and blood) were included in each MLPA run as before. 1 The PCR products were separated by electrophoresis on an ABI 3730 capillary sequencer (Applied Biosystems). Mean probe peaks were used for final gene copy number analysis with Genescan v4.1 (Applied Biosystems) and Coffalyser v9.4 (MRC-Holland) software.…”

“…We used the maximum distance and Ward's clustering method, and calculated the stability of the clusters with pvclust as before. 1 Information regarding prognosis and therapy was requested from the Integral Cancer registration, the Netherlands (IKNL). Survival data were available for 100 cases with a mean follow-up of 5.6 years.…”

“…1 This emphasizes the importance of identifying biomarkers and therapeutic targets that could aid in clinical management of male breast cancer.…”

“…High-grade ductal cancer often has complex changes, typically small regions of gain together with larger regions of loss. [2][3][4][5][6] Genetic alterations on chromosome 16 in male breast cancer are poorly characterized compared with female breast cancer, and only a few studies have been performed 1,7,8 of which the first analyzes only one gene on 16q and the latter studies analyze small series of male breast cancer. These studies report frequent chromosomal imbalances on both the short and long arm of chromosome 16.…”