P2-01-22: Characterization of Four ER-Negative Breast Primary Tumor Dissociated Cultures as a Model for the In Vitro and In Vivo Study of Tumorigenesis, Metastasis and Angiogenesis.

ER negative breast cancers comprise a subtype of tumors for which there are few therapies with successful response. Currently, the use of established cell lines has allowed detailed molecular and cellular studies on cancer mechanisms ranging form stem cells to proliferation, from tumorigenesis to invasion and metastases, and from tumor suppressors to oncogenes. But while cell lines provide a source of homogeneous, propagatable material, a drawback of this model is that most breast cancer cell lines are derived from metastatic lesions that may harbor additional mutations and have little resemblance with the primary tumor of origin. Additionally, the continuous passage of these cells over the last 20-plus years has given rise to well-established differences in growth rate, hormone receptor status, karyotype and clonogenicity. Our purpose here was to characterize four primary dissociated tumor (DT) cell cultures from ER- breast tumors, the establishment of which we had previously described, to determine if they could provide more accurate models for both in vitro and in vivo studies. These four DT cultures (DT16, DT22, DT25 and DT28) display a triple negative phenotype and were characterized by their genomic profile by the PAM50 predictor analysis as belonging to the basal (DT22, DT25 and DT28) and luminal B (DT16) subtypes. Of those cultures for which primary tumor sample was available, microarray gene expression profiling and cell line clustering analysis show the primary tumor and dissociated culture cluster together and to similar breast tumors. Interestingly, of the three basal DT cultures, DT22 clusters with Claudin-low tumors and cell lines. We have established that each of these 4 DTs are tumorigenic in the NOD/SCID mouse model, and are now assessing their metastatic potential. DT16 generated metastases in 25% of the mice (6 out of 24; two in liver, four in lymph node). DT22 generated highly vascularized tumors, which may provide a relevant model for study of the in vivo vascular recruitment process. In addition, we have analyzed and characterized the role of pivotal signaling pathways often deregulated in breast cancer such as EGFR, P-MAPK, PI3k/mTOR, p53, TGFb, Hedgehog, Notch, and Wnt in both the 2D culture as well as in sections of xenograft samples. Given that the scope of primary tumor heterogeneity and consequently the early stages of breast tumorigenesis are under-represented by current in vitro models in breast cancer research, the use of these DT cell cultures could more accurately recapitulate the disease in both the in vitro and in vivo settings. Citation Information: Cancer Res 2011;71(24 Suppl):Abstract nr P2-01-22.