Abstract 3822: DNA copy number changes in the PI3K signaling pathway genes in triple negative breast cancer

Abstract

Abstract Background: Triple negative breast cancer (TNBC) is associated with poor prognosis and a high mortality rate when compared to the other breast cancer subtypes. These tumors lack the expression of ER, PR and HER2 receptors, and do not respond well to the currently available adjuvant therapies. The phosphatidylinositol 3-kinase (PIK3) signaling pathway mediates key cellular functions. Alterations of genes in this pathway have been shown to predict responsiveness to cancer targeted therapies. In this study, five genes involved in this signaling pathway, PIK3CA, AKT1, AKT2, PTEN and FGFR, were evaluated for DNA copy number changes in two sets of TNBC specimens. Methods: TNBC samples were obtained from the Hospital Nossa Senhora das Gracas, Curitiba, PR, Brazil. Two sets of TNBC samples were analyzed: the first set was composed of 30 formalin fixed-paraffin embedded tissue specimens and were analyzed for the PIK3CA, AKT1, AKT2, PTEN and FGFR genes by FISH. Locus-specific probes were prepared from BAC contigs for each gene and a centromeric probe for chromosome 3 was used as a control for copy number. The second set was composed of 17 frozen samples and were analyzed by array-CGH using a 44K-Agilent array platform. Real-Time PCR (TaqMan assay), was used to validate the array-CGH data for the above five genes. Results: FISH: PTEN loss and FGFR3 amplification were the most common findings occurring in 56% and 41% of the TNBC samples respectively. PIK3CA, AKT2 and AKT1 were amplified in 31%, 25% and 9.5% of the samples respectively. Array-CGH/Real time PCR: DNA copy number changes were observed by array-CGH in all, but one TNBC sample. The gene with highest frequency of amplification detected by array-CGH was PIK3CA (amplified in 77% of the cases). These findings were confirmed in 70% of the cases. FGFR2, AKT2 and PTEN were amplified in 35%, 24% and 24% of the cases respectively, These findings were confirmed for FGFR2 in 83% of the samples and for PTEN in all the samples. AKT2 amplification was only confirmed in 25% of the samples. Finally AKT1 was observed amplified in by array-CGH in 6% of the cases, which was confirmed by Real-time PCR.Conclusions: Based on our initial results, we conclude that TNBC presents DNA copy number alterations in genes involved in the PIK3 signaling pathway. Upon validation of these alterations in a larger number of cases, with correlation to prognostic parameters, their potential use as therapeutic targets can be considered for further investigation. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 3822. doi:10.1158/1538-7445.AM2011-3822