Resistance of trisomy 8 cells to apoptosis is abrogated by knock-down of c-myc and survivin.Trisomy 8 BM was subjected to 25 Gy of gamma radiation and cultured for 1 hour in media as described in “Materials and methods.” The TUNEL assay was performed to identify DNA nicks and TUNEL⁺ and TUNEL⁻ fractions sorted for both irradiated and nonirradiated fractions. The numbers of viable cells were decreased in the irradiated fraction, and the TUNEL⁺ cells increased from 18% to 30%. When FISH was performed on these fractions, trisomy 8 cells were consistently present in the TUNEL⁺ fraction (A). When control (nonirradiated) and irradiated lymphocyte-depleted BMMNCs were placed in short-term methylcellulose culture for 2 weeks the numbers of diploid colonies decreased to a greater extent than the numbers of trisomy 8 colonies (B). When an inhibitor of c-myc was cocultured with BMMNCs from a patient with trisomy 8, and immunoblotted, and FISH performed after 2 weeks of growth, there was a substantial decrease in the number of trisomy 8 cells coincident with a decrease in c-myc protein (C). BMMNCs transfected with siRNA specific for survivin were placed in hematopoietic growth factors for 36 hours at 37°C as described in “Materials and methods.” FISH and cell enumeration were performed before, and following culture using a labeled probe for chromosome 8. Immunoblotting was performed on total-cell lysates using antibody to survivin. (D) A substantial loss of trisomy 8 cells is seen compared with the baseline.