Jl. Grem et al., DETERMINANTS OF SENSITIVITY TO 1-BETA-D-ARABINOFURANOSYLCYTOSINE IN HCT-116 AND NCI-H630 HUMAN COLON-CARCINOMA CELLS, Molecular pharmacology, 48(2), 1995, pp. 305-315
The cytotoxicity and metabolism of 1-beta-D-arabinofuranosylcytosine (
AraC) and its effects on DNA synthesis and integrity were studied in H
CT 116 and NCl-H630 human colon cancer cells. In 116 cells, 0.1 mu M A
raC decreased colony formation by similar to 50%, whereas 1 mu M was r
equired in H630 cells. AraCTP levels after a 24-hr AraC exposure were
2.3- to 3.5-foId lower in H630 cells due to increased ability to deami
nate AraCMP. AraC DNA levels increased in proportion to AraCTP pools (
r = 0.99) and were 2-fold higher in 116 cells after a 24-hr exposure t
o 0.1 and 1 mu M AraC. Although the half-life of AraCTP was < 1 hr in
both lines, > 80% of AraC DNA was retained at 24 hr after drug removal
. Clonogenic capacity was inversely related to the extent of AraC DNA
incorporation. Interference with nascent DNA chain elongation increase
d with increasing AraC concentration x time. A 24-hr AraC exposure pro
duced a dramatic shift in the elution profile of nascent DNA during a
15-hr elution at pH 12.1; these effects were greater in 116 cells (DNA
retained on filter [percentage of control]): 78%, 23%, and 9% with 0.
1, 1, and 10 mu M AraC versus 84%, 42%, and 18% in H630 cells, respect
ively. The extent of nascent DNA damage was proportional to AraC DNA c
ontent. Net DNA synthesis was potently inhibited during AraC exposure
in both lines. H630 cells had partial recovery of DNA synthesis at 24
hr after drug removal, whereas persistent inhibition was noted in 116
cells. A slight excess of double-strand breaks in parental DNA was det
ected after a 24-hr exposure to 10 mu M AraC in 116 cells. The extent
of DNA fragmentation was more pronounced 16 hr after drug removal and
was greater in 116 cells: 8.5%, 19%, and 21% with 0.1, 1, and 10 mu M
AraC versus 2.3%, 9%, and 15% in 630 cells, respectively. Thus, AraC D
NA content, magnitude of nascent DNA damage, duration of DNA synthetic
inhibition, and induction of double-stranded DNA fragmenation appeare
d to be the crucial determinants of lethality.