A K-ras oncogene increases resistance to sulindac-induced apoptosis in rat enterocytes.
OBJECTIVE
Mutations of c-K-ras occur commonly in colonic neoplasms. The aim of this study was to determine how c-K-ras mutations alter the responses to the chemopreventive agent sulindac.


METHODS
The parental rat intestinal cell line IEC-18 and c-K-ras-transformed derivatives were treated with sulindac sulfide. Cell cycle distribution was determined by flow-cytometric analysis (fluorescence-activated cell sorter), apoptosis by DNA fragmentation (laddering), flow cytometry, and microscopy, and changes in gene expression by immunoblotting.


RESULTS
Sulindac sulfide inhibited cell growth and induced apoptosis in a time- and dose-dependent manner more rapidly in and at lower concentrations in parental cells than ras-transformed cells. Expression of the sulindac sulfide arrested cells in G0/G1, but cells entered apoptosis throughout the cell cycle. Proapoptotic protein Bak was relatively high in untreated parental cells and increased markedly after sulindac sulfide but was low in untreated ras-transformed cells and did not increase after sulindac sulfide. Expression of other Bcl-2 family members was unchanged after sulindac sulfide. However, sulindac sulfide reduced levels of cyclin D1 protein and cyclin E- and cyclin D1-associated kinase activity.


CONCLUSIONS
c-K-ras-transformed enterocytes are relatively resistant to sulindac sulfide-induced growth inhibition and apoptosis, which may result from specific reduction of bak expression.
Arber
N
N
Herbert Irving Comprehensive Cancer Center, Columbia University, New York, USA.
Han
E K
EK
Sgambato
A
A
Piazza
G A
GA
Delohery
T M
TM
Begemann
M
M
Weghorst
C M
CM
Kim
N H
NH
Pamukcu
R
R
Ahnen
D J
DJ
Reed
J C
JC
Weinstein
I B
IB
Holt
P R
PR
D000818:Animals; D000894:Anti-Inflammatory Agents, Non-Steroidal / Q000494:pharmacology*; D017209:Apoptosis / Q000502:physiology*; D002453:Cell Cycle / Q000187:drug effects; D002455:Cell Division / Q000187:drug effects; D002461:Cell Line, Transformed; D004351:Drug Resistance / Q000502:physiology; D005786:Gene Expression Regulation / Q000187:drug effects; D011905:Genes, ras / Q000502:physiology*; D007422:Intestines / Q000166:cytology / Q000187:drug effects* / Q000502:physiology*; D051381:Rats; D013467:Sulindac / Q000494:pharmacology*
D000894:Anti-Inflammatory Agents, Non-Steroidal; D013467:Sulindac