SUSCEPTIBILITY TO P53 DEPENDENT APOPTOSIS CORRELATES WITH INCREASED LEVELS OF GAS2 AND GAS3 PROTEINS

p53 dependent apoptosis is a critical regulator of tumorigenesis. In t his paper we demonstrate that BALB/c cells transformed with a LT mutan t perturbing pRb but not p53 functions (LT-2809) show unrestrained cel l division under low serum condition which is actively counterbalanced by apoptosis. BALB/c cells transformed with a LT mutant perturbing p5 3 but not pRb functions (LT-K1), show similar unrestrained cell divisi on but no evident signs of apoptosis when grown in low serum. Such apo ptotic response of LT-2809 cells is characterised by increased express ion of Gas2 which becomes proteolytically processed. Similarly Gas3 ex pression is markedly increased in LT-2809 cells with respect to LT-K1. Since both Gas2 and Gas3 have been previously associated with the apo ptotic response at growth arrest, our observations suggest that they c ould also contribute to the regulation of cellular susceptibility to p 53 dependent apoptosis.