Tumorigenic Cells Are Common in Mouse MPNSTs but Their Frequency Depends upon Tumor Genotype and Assay Conditions

Summary initiating cells have been suggested to be rare in many cancers. We tested this in mouse malignant peripheral nerve sheath tumors (MPNSTs) and found that 18% of primary and 49% of passaged MPNST cells from Nf1+/−; Ink4a/Arf−/− mice formed tumors upon transplantation, whereas only 1.8% to 2.6% of MPNST cells from Nf1+/−; p53+/− mice did. MPNST cells of both genotypes require laminin binding to β1-integrin for clonogenic growth. Most MPNST cells from Nf1+/−; Ink4a/Arf−/− mice expressed laminin, whereas most MPNST cells from Nf1+/−; p53+/− mice did not. Exogenous laminin increased the percentage of MPNST cells from Nf1+/−; p53+/− but not Nf1+/−; Ink4a/Arf−/− mice that formed tumorigenic colonies. Tumor-forming potential is common among MPNST cells, but the assay conditions required to detect it vary with tumor genotype.