Sl. Hsu et al., RETINOIC ACID-INDUCED APOPTOSIS IS PREVENTED BY SERUM-ALBUMIN AND ENHANCED BY LIPIODOL IN HUMAN HEPATOMA HEP3B CELLS, Cancer letters, 129(2), 1998, pp. 205-214
The effects of retinoic acid (RA) on the cell growth and viability of
human hepatoma Hep3B cells were examined. We showed that removal of se
rum in the presence of RA results in cell death in a dose-dependent ma
nner in human hepatoma Hep3B cells. Time-course cell death analysis sh
owed that RA at a dose of 10 mu M induces a rapid (48-72 h) fall in ce
ll viability (>95%). The drug-induced cell death was RA-specific, sinc
e three RA analogs (retinol, retinal and retinol acetate) did not show
any cytocidal activity at an equimolar dose. Fluorescence microscopy
and DNA fragmentation analysis showed that Hep3B cells treated with RA
underwent a death process highly reminiscent of apoptosis, with chrom
atin condensation, nuclear fragmentation and the presence of a 180-200
bp DNA fragment ladder. Additionally, we found that RA-induced apopto
sis was reduced by 70-80% when the medium was supplemented with serum
albumin (human and bovine) at a concentration of 0.05%. However, a var
iety of known growth factors were ineffective in preventing RA-induced
apoptosis. Preincubating serum and serum albumin with Lipiodol restor
ed the apoptotic effects of RA demonstrated in serum-free systems. The
se data suggest that the binding of RA by serum albumin may have reduc
ed the bioavailability of RA, restricting its apoptotic effects on Hep
3B cells. Blocking RA-albumin interactions with a Lipid lymphographic
contrast medium (Lipiodol) may improve the bioavailability of RA and s
ignificantly enhance its apoptotic effect on human hepatoma Hep3B cell
s. (C) 1998 Elsevier Science Ireland Ltd. All rights reserved.