Transfer of p16(inka)/CDKN2 gene in leukaemic cell lines inhibits cell proliferation

The gene encoding for p16(ink4a), a negative regulator of transition between G1 and S phase, is homozygously deleted in a large proportion of acute lymphoblastic leukaemias (ALL). Transfer of p16(ink4a) gene in several solid tumour cell lines with functional pRb and lacking both p16(ink4a) alleles has resulted in a dramatic reduction of cell proliferation, and the aim of this work was to confirm this effect in leukaemic (especially ALL) cell lines, We tested the proliferation in liquid medium and in soft agar after transfer of pi 6(ink4a) gene by a retroviral vector in leukaemic cell lines with homozygous p16(ink4a) gene deletion (K562, GEM, Jurkat cell lines) or with p16(ink4a) gene hemizygous deletion and a point mutation inactivating the remaining allele (HL60 cell line). The viral titre obtained after transfection of PA317 amphotropic packaging cell line, which has a p16(ink4a) gene homozygous deletion, was low, suggesting that p16(ink4a) gene expression could impair viral production of retroviral packaging cell lines derived from the NIH3T3 cell line. After retroviral transfer of p16(ink4a) in cell lines and G418 selection in liquid medium, a strong cell proliferation inhibition was observed for K562, CEM and Jurkat, but no inhibition was seen for HL60, A strong growth reduction in soft agar was also observed with p16(ink4a)-transduced GEM, Jurkat and K562 cells, with a moderate growth reduction in the HL6O cell line. The growth inhibition in liquid culture, of K562 and Jurkat cell lines, was confirmed by electroporation transfer of the p16(ink4a) gene. Our findings show that p16(ink4a) gene transfer has a growth-inhibitory effect in leukaemic cell lines with p16(ink4a) gene homozygous deletion, These data suggest that p16 could be a suitable gene for gene therapy in ALL.