The acquisition of an invasive phenotype is a pre-requisite for metastasis. We set out to develop cellular systems that can mirror transient and stbale molecular alterations that confer an invasive phenotype to breast cancer cells. We observed that it is possible to isolate invasive subpopulations from moderately invasive cancer cell lines. Enrichment of invasive sub-populations of MDA-MB-231 breast cancer cells in three successive preparative invasion assays in Matrigel covered Boyden chambers yielded a highly invasive cell line. Prolonged cultivation of these cells did not abolish the invasive phenotype although not all phenotypic changes acquired during selection are maintained by long term cultures. Genetic analyses of these cells by cytogenetics and array based comparative genome hybridization revealed many genetic alterations including increased ploidy. The flow cytometric DNA Index (DI) changes from 1.28 to 2.28. Cells with DI 2.28 constitute 1.4% of the parental cell line. Whole genome SNP analysis shows that the two populations are genetically related excluding any cell contamination. The invasive cells proliferate and undergo apoptosis similar to the parental cells. Commitment to apoptosis is increased since invasive cells respond more strongly to curcumin or peroxide induced apoptosis. Invasive cells show relative resistance to the cytotoxic, alkylating agent Doxorubicin and increased sensitivity to the anti-mitotic drugs Vincristine and Taxol. Increased resistance to the topoisomerase II inhibitor Mitoxantrone is observed only transiently in invasive cells and lost in long term cultures. Similarly, the chemokines CXCL1 and -2 are transiently upregulated. Response to the anti-diabetic drug Metformin showed a reduced sensibility for invasive cells in terms of growth inhibition (IC50). Gene expression profiling shows complex alterations in gene expression. Many of the genes that are differentially expressed in highly versus moderately invasive cells are differentially expressed in human breast cancer cases with and without distant metastasis and correlate with disease free survival. The invasive phenotype is not related to stem cell features nor to epithelial mesenchymal transition. These cells constitute a novel model for tumor progression. Tumorigenicity and metastatic potential in vivo are currently being tested.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 496. doi:1538-7445.AM2012-496