The purpose of this study was to investigate the possible molecular mechani
sms of the antiproliferative effect induced by protocatechualdehyde (PA, a
dihydroxybenzene derivative). The viability of cytotoxic T cells (CfLL-2) s
timulated by IL2 was significantly inhibited at 0.12 mM PA. This inhibitory
effect was associated with the induction of apoptosis detected by DNA frag
mentation assay. DNA ladder appeared at 0.12 mM PA and the intensity of DNA
ladder was visible at 0.3 mM PA. PA inhibited the Ib2-dependent tyrosine p
hosphorylation of 91, 80 and 55 KDa proteins, but did not affect IL2-depenc
tent serine/threonine phosphorylation of proteins. The levels of bcl-2 prot
ein and mRNA were suppressed by PA. An alteration in bax protein expression
on the apoptosis process in CTLL-2 cells was not observed. However, caspas
e-3 activity was increased by PA. Our results demonstrate that PA inhibited
cell proliferation and induced apoptosis in CTLL-2 cells. It is concluded
that PA is a potent anti-proliferative agent and is expected to be a promis
ing candidate for novel therapeutics.