Alteration of p16 (CDKN2) gene is associated with interleukin-2-induced tumor cell growth in adult T-cell leukemia

Because tumorigenesis frequently involves the dysfunction of cell cycle-rel ated proteins, we examined the effect of mutations in CDK inhibitor p16 and its linked genomic loci p15, cl.B, and 1063.7 on the growth of primary adu lt T-cell leukemia (ATL) cells. Southern blot analysis of primary ATL cells showed a significantly higher incidence of p16 gene alteration in acute AT L than in chronic ATL [67.7% (23/34) vs 26.1% (6/23), respectively; p < 0.0 03]. Similarly, polymerase chain reaction (PCR) analysis of p16 exon 2 reve aled a higher incidence of alteration in acute ATL than in chronic ATL [52. 9% (18/34) vs 26.1% (6/23), respectively; p < 0.05]. PCR-single strand conf ormation polymorphism analysis of exons 1 and 2 of p16 showed no mutations in the patients,,vith normal pattern by Southern blotting or PCR analysis. Notably five of six chronic ATL patients with abnormal p16 genes progressed to acute crisis within 4 months. PCR analysis of the p16 linked loci 1063. 7, p15 exon 2, and cl.B found homozygous deletion in 55.9%, 20.6%, and 2.9% of acute ATL cells and 39.1%, 13.0%, and 0% of chronic ATL cells, respecti vely, showing no relationship of homozygous deletion in either loci with di sease subtypes. In most cases, deletions were seen in multiple genes, inclu ding p16. Acute ATL cells had a higher frequency of multigene deletions tha n chronic ATL cells [44.1% vs 17.4%;p < 0.05]. When leukemic cells were ana lyzed for interleukin 2 (IL-2) responsive growth, only p16 gene alteration was directly associated with leukemic cell growth activity. Among leukemic cells showing high IL-2 responsiveness, 73.1% (19/26) had p16 gene alterati on vs 27.8% (5/18) of leukemic cells that showed low IL-2 responsiveness (p < 0.005). p16 gene alteration was found in 73.3% (14/19) of leukemic cells showing high autonomous growth rates but in only 40.0% (10/25) of those le ukemic cells showing low autonomous growth (p < 0.03). These results sugges t the following: alteration of p16-related genomic regions in ATL is usuall y a wide rearrangement including the p16 gene; within this region, only p16 gene alteration is associated with disease aggressiveness; and p16 gene de letion may be a proximate event in leukemogenesis. Society for Experimental Hematology. Science Inc. (C) 1999 International Published by Elsevier.