c-IAP1 is overexpressed in HL-60 cells selected for doxorubicin resistance: effects on etoposide-induced apoptosis.
BACKGROUND
We previously demonstrated that KN-62, an inhibitor of calcium calmodulin-dependent enzymes, sensitizes human leukemia HL-60 cells resistant to topoisomerase II-targeting drugs. The objective of this study was to determine pathways of apoptosis downstream of DNA damage induced by KN-62 co-treatment with VP-16.


METHODS
HL-60/Y/DOX0.05 cells were treated with VP-16, KN-62, or VP-16 + KN-62. Following treatment, cells were assayed for c-IAP1, c-IAP2 and XIAP protein expression, as well as caspase activation, cytochrome c release and PARP cleavage.


RESULTS
Baseline c-IAP1 protein levels were 2-fold higher in HL60 cells selected for resistance to doxorubicin compared to the parent sensitive line. VP-16 and KN-62 co-treatment was associated with caspase activation via the mitochondrial pathway and significant reductions (p = 0.002) in c-IAP1 protein expression but not with c-IAP2 or XIAP.


CONCLUSIONS
These data suggest that KN-62 co-treatment sensitizes doxorubicin-resistant cells to VP-16-induced apoptosis by enhancing caspase activity and reducing c-IAP1 expression.
Vaziri
Susan A
SA
Experimental Therapeutics Program, Taussig Cancer Center, Cleveland Clinic Foundation, 9500 Euclid Avenue, Cleveland, Ohio 44195, USA.
Grabowski
Dale R
DR
Tabata
Masahiro
M
Holmes
Katherine A
KA
Sterk
Joseph
J
Takigawa
Nagio
N
Bukowski
Ronald M
RM
Ganapathi
Mahrukh K
MK
Ganapathi
Ram
R
D019307:1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine / Q000008:administration & dosage / Q000031:analogs & derivatives* / Q000494:pharmacology; D000903:Antibiotics, Antineoplastic / Q000494:pharmacology; D000970:Antineoplastic Agents / Q000494:pharmacology*; D000971:Antineoplastic Combined Chemotherapy Protocols / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects*; D020169:Caspases / Q000378:metabolism; D004249:DNA Damage; D004317:Doxorubicin / Q000494:pharmacology*; D019008:Drug Resistance, Neoplasm; D004789:Enzyme Activation / Q000187:drug effects; D005047:Etoposide / Q000008:administration & dosage / Q000494:pharmacology*; D015973:Gene Expression Regulation, Leukemic; D018922:HL-60 Cells; D006801:Humans; D051034:Inhibitor of Apoptosis Proteins; D014176:Protein Biosynthesis; D011506:Proteins / Q000037:antagonists & inhibitors / Q000235:genetics; D044767:Ubiquitin-Protein Ligases; D015854:Up-Regulation
D000903:Antibiotics, Antineoplastic; D000970:Antineoplastic Agents; D051034:Inhibitor of Apoptosis Proteins; D011506:Proteins; C063302:KN 62; D005047:Etoposide; D004317:Doxorubicin; D019307:1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine; C494833:BIRC2 protein, human; D044767:Ubiquitin-Protein Ligases; D020169:Caspases