SMAD1 and central nervous system cancer: While the sample contained too few cells to allow for meaningful unsupervised clustering, differential expression of analysis of cells at recurrence revealed a trend toward enrichment of the SMAD1(+) glioma cells markers, ID1 and SAT1, and a statistically significant loss of the SMAD2(+) glioma cell markers, EGFR and SALL2 (Fig. 5F).