To further define the local activity of the Asm and the local formation of ceramide, we co-incubated tumor cells with wild-type or Asm-deficient platelets, washed the cells, and used the cell pellets for immunoprecipitation of the Asm from cell surfaces or measurements of surface ceramide by performing an in situ ceramide kinase assay on intact cells (Fig2C and D). The gene discussed is CERK; the disease is neoplasm.