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[96] The MINO Mouse Model of DCIS Reveals a Genetically Stable Precancer Stem Cell with a Programmed Malignant Potential

AD Borowsky, P Damonte, JP Gregg, QA Chen, LJT Young, JG Hodgson. UC Davis, Davis, CA; UC Davis, Sacramento, CA; UCSF, San Francisco, CA

Background: The MINO mouse consists of six lines with distinct morphologic phenotypes and behavior, each meeting experimentally defined criteria for pre-cancer. Specifically, these serially transplanted outgrowths derived from the Tg(MMTV-PyVmT) mouse grow orthotopically in cleared mammary fat pads and consistently progress to an invasive phenotype capble of ectopic growth. Transition to carcinoma has a consistent latency for each line, ranging from 11wks (+/-1.2) to 22 wks (+/- 1.7). Three of the liines also show pulmonary metastatic potential.
Design: MINO tissues were harvested for DNA extraction and cell dissociations. Comparative genomic hybridizaion was performed by BAC array hybridization, and oligonucleotide array hybridization. Cell dissociation, culture conditions and flow cytometry separations have been optimized. Normal mouse mammary tissues, and tissues from invasive carcinomas were harvested for parallel analysis.
Results: (1) Comparative genomic hybridization shows that the pre-cancer and invasive tumors are genetically stable with low level changes including whole chormosome gains in some lines. Other lines show no genomic abnormalities (euploidy). No changes are associated with progression, though occasional spontaneous focal amplificaitons and deletions are detectable. (2) Dissociation of the precancer lesion cells and three dimensional spheroid culture of single cells reveals a bipotential for myoepithelial and luminal differentiation and the formation of unique 3D MINO-spheres with intermediate features between nomral and carcinoma cells performed in parallel. (3) Flow cytometric sorting for CD49f+/CD24hi/CD29+/CD45-/CD31-/Ter119-/ single viable cells shows enrichment of the cells capable of forming these MINOspheres. (4) Transplantation of a single MINOsphere recapitulates the outgrowth of the precancer morphology and progression to carcinoma.
Conclusions: These data establish a pre-cancer stem cell capable of self renwal and multilineage differentiation as the origin of invasive cancer. In the context of this model, these cells have programmed potential for latency and metastasis that does not appear to require sequential genetic hits for transformation.
Category: Breast

Monday, March 26, 2007 9:15 AM

Platform Session: Section D, Monday Morning