SP3 and neoplasm: The cell growth step of the mechanism has been addressed in two ways: 1) the possibility of obtaining cells resistant to Sp3-induced apoptosis through specific cleavage by caspase; the presence of a putative consensus cleavage site (DSSD) in the Sp3 sequence supports our results but the cleavage at this specific site needs to be confirmed; 2) formation of tumours in nude mice has highlighted in vivo selection processes.