A novel SERCA inhibitor demonstrates synergy with classic SERCA inhibitors and targets multidrug-resistant AML.
Drug resistance exists as a major obstacle in the treatment of cancer, and drug molecules that retain effectiveness against resistant cancers are a high clinical priority. Ethyl 2-amino-6-(3,5-dimethoxyphenyl)-4-(2-ethoxy-2-oxoethyl)-4H-chromene-3-carboxylate (CXL017) was recently identified as a promising lead for the treatment of multidrug-resistant leukemia, which elicits its cytotoxic effect, in part, through inhibition of the sarco/endoplasmic reticulum Ca(2+)-ATPase (SERCA). Herein initial experiments with SERCA1a and CXL017 demonstrated no significant effect on calcium affinity, competed with ATP, and induced a dose-dependent decrease in ATPase activity. Among all CXLs tested, (-)-CXL017 exhibited the greatest SERCA inhibition with an IC50 = 13.5 ± 0.5 μM. Inhibitor combination studies were used to assess potential interactions between (-)-CXL017 and well-known SERCA inhibitors: thapsigargin, cyclopiazonic acid, and 2,5-di-tert-butylhydroquinone. Surprisingly, (-)-CXL017 exhibited marked synergy with each of the known SERCA inhibitors, whereas all combinations of the known inhibitors yielded additive effects, indicating that (-)-CXL017 may bind at a unique allosteric site. Treatment of parental (HL60) and multidrug-resistant (HL60/MX2) acute myeloid leukemia cells with the known SERCA inhibitors revealed that all of these inhibitors demonstrate selective cytotoxicity (7.7-400-fold) for the resistant cell line. Within the CXL series, a positive correlation exists between SERCA inhibition and cytotoxicity in HL60/MX2 but not HL60. (-)-CXL017 was also shown to enhance the cytotoxicity of thapsigargin in HL60/MX2 cells. Given the elevated SERCA levels and ER calcium content in HL60/MX2, SERCA likely plays a significant role in the collateral sensitivity of this multidrug-resistance cell line to CXL molecules as well as known SERCA inhibitors.
Department of Medicinal Chemistry, University of Minnesota , 2231 Sixth St. SE, Minneapolis, Minnesota 55455, United States.
Nicholas P
NP
Bleeker
Razvan L
RL
Cornea
David D
DD
Thomas
Chengguo
C
Xing
D001578:Benzopyrans / Q000494:pharmacology; D002470:Cell Survival / Q000187:drug effects; D018432:Drug Resistance, Multiple; D019008:Drug Resistance, Neoplasm; D004357:Drug Synergism; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D018922:HL-60 Cells; D006801:Humans; D015470:Leukemia, Myeloid, Acute / Q000378:metabolism*; D053498:Sarcoplasmic Reticulum Calcium-Transporting ATPases / Q000037:antagonists & inhibitors*
D001578:Benzopyrans; D004791:Enzyme Inhibitors; C543325:ethyl 2-amino-6-(3,5-dimethoxyphenyl)-4-(2-ethoxy-2-oxoethyl)-4H-chromene-3-carboxylate; D053498:Sarcoplasmic Reticulum Calcium-Transporting ATPases