Abstract 3928: Caveolin-1: Beyond a marker for basal-like breast cancers

Introduction: Caveolin-1 (Cav1) is associated with basal-like triple-negative (ER-/PR-/Her2-) breast cancers (TNBC). Its biological contribution to this subtype has not been fully explored and controversy persists regarding the molecular role of Cav1 in carcinogenesis. Experimental Procedures: Thirty-four TNBC (17 Cav1+/17 Cav1-) patients molecularly-profiled with a commercial assay (Caris Life Sciences, AZ) were evaluated retrospectively. Cav1 status was determined by immunohistochemistry (caveolin-1 polyclonal; ≥2+ ≥50%). The majority of specimens (28/34) used for profiling were from primary breast sites and contained ≥50% neoplastic cells. The transcriptomes were profiled using Illumina9s HumanHT-12 microarray (v4). Data were normalized using mean normalization procedure. Differential expression analysis was performed using R9s Limma package. Pathway analysis was carried out using R9s signaling pathway impact analysis (SPIA) package with 69 cancer, immunity, and cell signaling related KEGG pathways. Results: Using a cutoff of two-fold and adjusted p-value of 0.05, we identified 954 genes differentially expressed between Cav1+/- TNBC patients. Included in these were 31 genes which were found to be up-regulated by over five- fold and 3 genes down-regulated by over five fold in Cav1+ TNBC. Genes of notable interest for their role in cell signaling, cell adhesion, tumor invasion and metastasis, included an up-regulation of TGFBR2, SPARC, integrins (ITGA11, ITGB5, ITGBL1), cell adhesion proteins (LAMB3, COL5A3) and molecules which facilitate tumor invasion (LAMB3, MMP1, MMP2, MMP9). In addition, genes found to be down-regulated in Cav1+ patients and notable for their roles in promoting epithelial-mesenchymal-transition (EMT) included Claudin 3(CLD3) and CA125/MUC16 (Mucin 16). We also detected an approximately two-fold down-regulation of CDKN2A in Cav1+ patients. Using SPIA pathway analysis, 12 pathways were found to be differentially activated in Cav1+ vs. Cav1- TNBC. The most differentially activated pathways were the focal adhesion pathway (p = 4.51E-18), PI3k-Akt signaling pathway (p = 2.01E-6) and TGF-β and MAPK signaling pathways (p = 0.005, 0.014, respectively). Conclusions: Differential gene expression patterns and pathway analyses provide evidence for distinct profiles for gene expression between Cav1+/- TNBC. Cav1+ TNBC patients exhibit up-regulation of genes important for cell signaling, extracellular matrix remodeling and tumor invasion, and down-regulation of genes that may facilitate EMT and loss of cell cycle control. The focal adhesion pathway, as well as TGF-β, PI3K and MAPK signaling pathways, were identified as differentially activated among Cav1+/- TNBC. Taken together, these data support the role of Cav1+ in identifying a subtype of TNBC that may have a greater risk for invasion and metastasis. The correlation of this subtype with prognosis and drug response should be investigated in future studies. Citation Format: Rebecca A. Feldman, Zoran Gatalica, Semir Vranic, Ryan Bender, Sandeep Reddy, Anatole Ghazalpour. Caveolin-1: Beyond a marker for basal-like breast cancers. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 3928.