Supplementary 3 PTB PTB Actin Actin 0.014 GM1953 control 0.03 GM1953 siPTB 0.012 0.025 GM1311 siPTB 0.01 0.02 0.008 CPM/cell number CPM/cell number 0.015 0.006 0.01 0.004 0.002 0.005 6 12 18 24 6 12 18 24 Time (hrs) Time (hours) PTB levels were reduced by siRNA and cells were seeded into 12 well plates at 100,000 cells/well. After 24 hours, 5µCi/ml of [3H]thymidine was added to each well with fresh media, and then cells were incubated and harvested at 6 hour intervals. The cells were then washed twice with phosphate buffered saline before the addition of 10 % (w/v) trichloroacetic acid. Cells were collected and precipitated on ice for 30 min before being filtered through nitrocellulose with extensive washing. Filters were dried, and scintillation readings taken on a Molecular Dynamics scintillation counter. Cell proliferation is expressed as [3H]thymidine incorporation (CPM) relative to cell number. The data show that in GM1311 the MM derived cell line when the expression of PTB-1 is reduced proliferation is inhibited more than the control B-cell line GM1953. Supplementary 3