Investigation of the mechanisms by which EB1089 abrogates apoptosis induced by 9-cis retinoic acid in pancreatic cancer cells.
OBJECTIVE
Previous research has shown that the retinoid 9-cis retinoic acid (RA) promotes apoptosis in pancreatic cancer cells. The vitamin D analog EB1089 does not. Furthermore, cotreatment of cells with 9-cis RA and EB1089 abrogates apoptosis. To explain this, we studied the regulation of proteins involved in apoptotic signaling pathways in pancreatic cancer cells.


METHODS
The pancreatic adenocarcinoma cell line T3M4 was used. Cell proliferation was measured using the SRB protein dye assay. Induction of apoptosis was evaluated using an ELISA assay. Caspase activation was detected using a colorimetric assay based on cleavage of a caspase-associated substrate. Regulation of protein levels and posttranslational events were detected using immunoblotting.


RESULTS
We confirm that EB1089 diminishes apoptosis induced by 9-cis RA in T3M4 cells. We extend the study to show that EB1089 abrogates increases, induced by 9-cis RA, in caspase activation, p27Kip1 protein levels, Bim and Bax protein levels and in Bax/Bcl2 ratio. In addition, the CDKI p21Waf1 and CAII, a differentiation marker for pancreatic cancer cells are also differentially regulated.


CONCLUSIONS
These results suggest that the inhibitory effects of EB1089 on 9-cis RA-induced apoptosis lie upstream of caspase activation and could be associated with reduction of p27Kip1 protein levels.
Mouratidis
Petros X E
PX
Division of Oncology, Department of Cellular and Molecular Medicine, St. George's University of London, London, United Kingdom.
Dalgleish
Angus G
AG
Colston
Kay W
KW
D000230:Adenocarcinoma / Q000188:drug therapy / Q000473:pathology; D000077556:Alitretinoin; D000970:Antineoplastic Agents / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects*; D002117:Calcitriol / Q000031:analogs & derivatives* / Q000494:pharmacology; D020169:Caspases / Q000378:metabolism; D002455:Cell Division / Q000187:drug effects; D045744:Cell Line, Tumor; D050760:Cyclin-Dependent Kinase Inhibitor p27 / Q000187:drug effects / Q000378:metabolism; D004797:Enzyme-Linked Immunosorbent Assay; D006801:Humans; D010190:Pancreatic Neoplasms / Q000188:drug therapy* / Q000473:pathology; D014212:Tretinoin / Q000494:pharmacology*
D000970:Antineoplastic Agents; D050760:Cyclin-Dependent Kinase Inhibitor p27; D000077556:Alitretinoin; D014212:Tretinoin; D020169:Caspases; D002117:Calcitriol; C078903:seocalcitol