Heterocyclic substituted cantharidin and norcantharidin analogues--synthesis, protein phosphatase (1 and 2A) inhibition, and anti-cancer activity.
Norcantharidin (3) is a potent PP1 (IC(50)=9.0+/-1.4 microM) and PP2A (IC(50)=3.0+/-0.4 microM) inhibitor with 3-fold PP2A selectivity and induces growth inhibition (GI(50) approximately 45 microM) across a range of human cancer cell lines including those of colorectal (HT29, SW480), breast (MCF-7), ovarian (A2780), lung (H460), skin (A431), prostate (DU145), neuroblastoma (BE2-C), and glioblastoma (SJ-G2) origin. Until now limited modifications to the parent compound have been tolerated. Surprisingly, simple heterocyclic half-acid norcantharidin analogues are more active than the original lead compound, with the morphilino-substituted (9) being a more potent (IC(50)=2.8+/-0.10 microM) and selective (4.6-fold) PP2A inhibitor with greater in vitro cytotoxicity (GI(50) approximately 9.6 microM) relative to norcantharidin. The analogous thiomorpholine-substituted (10) displays increased PP1 inhibition (IC(50)=3.2+/-0 microM) and reduced PP2A inhibition (IC(50)=5.1+/-0.41 microM), to norcantharidin. Synthesis of the analogous cantharidin analogue (19) with incorporation of the amine nitrogen into the heterocycle further increases PP1 (IC(50)=5.9+/-2.2 microM) and PP2A (IC(50)=0.79+/-0.1 microM) inhibition and cell cytotoxicity (GI(50) approximately 3.3 microM). These analogues represent the most potent cantharidin analogues thus reported.
Hill
Timothy A
TA
Department of Chemistry, School of Environmental and Life Sciences, The University of Newcastle, Callaghan, NSW 2308, Australia.
Stewart
Scott G
SG
Sauer
Benjamin
B
Gilbert
Jayne
J
Ackland
Stephen P
SP
Sakoff
Jennette A
JA
McCluskey
Adam
A
D000970:Antineoplastic Agents / Q000138:chemical synthesis / Q000494:pharmacology*; D019086:Bridged Bicyclo Compounds, Heterocyclic / Q000138:chemical synthesis / Q000494:pharmacology*; D002193:Cantharidin / Q000031:analogs & derivatives / Q000138:chemical synthesis / Q000494:pharmacology*; D004791:Enzyme Inhibitors / Q000138:chemical synthesis / Q000494:pharmacology*; D006571:Heterocyclic Compounds / Q000737:chemistry*; D006801:Humans; D020128:Inhibitory Concentration 50; D010749:Phosphoprotein Phosphatases / Q000037:antagonists & inhibitors*; D054645:Protein Phosphatase 1; D013329:Structure-Activity Relationship; D014407:Tumor Cells, Cultured / Q000187:drug effects / Q000473:pathology
D000970:Antineoplastic Agents; D019086:Bridged Bicyclo Compounds, Heterocyclic; D004791:Enzyme Inhibitors; D006571:Heterocyclic Compounds; C069741:norcantharidin; D010749:Phosphoprotein Phosphatases; D054645:Protein Phosphatase 1; D002193:Cantharidin