PLAUR and neoplasm: A decrease in the frequency of neurosphere formation in a limiting dilution assay is frequently interpreted as indicating a decrease in the percentage of tumor-initiating cells or cells with stem cell-like properties35,36,44; however, the decrease in neurosphere formation also may reflect the effects of uPAR gene-silencing on cell proliferation and/or survival so that neurospheres fail to achieve the 60 μm diameter threshold.