The exogenous wild-type p14ARF gene induces growth arrest and promotes radiosensitivity in human lung cancer cell lines

The cyclin-dependent kinase inhibitor p16INK4a encoded by the INK4A/CDKN2/M TS1 gene is a frequent target of 9p21 inactivation in human lung cancers. T he p14ARF transcript, which is an alternative spliced form of this locus, i s also altered or deleted in a proportion of human lung cancers and has bee n shown to inhibit cell cycle progression as an endogenous cellular regulat or of the p53 protein, raising the possibility that it might constitute an additional lung tumor suppressor gene at the 9p21 locus. To test the candid acy of p14ARF as a lung cancer suppressor and assess the role it plays in r adiosensitivity, we transfected the wild-type p14ARF gene into four cell li nes which had various endogenous gene backgrounds of INK IA-I p53+/RB+(A549 and H460), INK4A+/p53+/RB-(H446) as well as p14ARF+/p53-/RB+ (Calu-1). We found that. transfection of p14ARF is related to an obvious growth inhibiti on in all wtp53 cell lines, regardless of INK4A/ARF and RB status. Although it has been shown that: p53-induced G1 checkpoint in response to DNA damag e by ionizing radiation is p14ARF-independent, we found the radiosensitivit y of two p14ARF-deficient cell lines was increased after p14ARF gene transf er. The results indicated that cell cycle redistribution after acquiring th e exogenous gene might be the main explanation for the enhanced sensitizati on. An increased radiation-induced apoptotic proportion in one cell line al so suggested a fortified p53 function that might be triggered by the restor ed p14ARF protein.