ABSTRACT
In spite of the impressing cytotoxicity of thapsigargin (Tg), this compound cannot be used as a chemotherapeutic drug because of general toxicity, causing unacceptable side effects. Instead, a prodrug targeted towards tumors, mipsagargin, was brought into clinical trials. What substantially reduces the clinical potential is the limited access to Tg and its derivatives and cost-inefficient syntheses with unacceptably low yields. Laser trilobum, which contains a structurally related sesquiterpene lactone, trilobolide (Tb), is successfully cultivated. Here, we report scalable isolation of Tb from L. trilobum and a transformation of Tb to 8-O-(12-aminododecanoyl)-8-O-debutanoylthapsigargin in seven steps. The use of cultivated L. trilobum offers an unlimited source of the active principle in mipsagargin.
Subject(s)
Antineoplastic Agents, Phytogenic/chemistry , Apiaceae/chemistry , Butyrates/chemistry , Chemistry Techniques, Synthetic , Furans/chemistry , Thapsigargin/analogs & derivatives , Antineoplastic Agents, Phytogenic/isolation & purification , Apiaceae/metabolism , Butyrates/isolation & purification , Carbon Dioxide/chemistry , Chromatography, Supercritical Fluid/methods , Fruit/chemistry , Fruit/metabolism , Furans/isolation & purification , Humans , Molecular Structure , Neoplasms/drug therapy , Neoplasms/pathology , Plant Extracts/chemistry , Sarcoplasmic Reticulum Calcium-Transporting ATPases/antagonists & inhibitors , Sarcoplasmic Reticulum Calcium-Transporting ATPases/metabolism , Thapsigargin/isolation & purificationABSTRACT
Efforts directed toward the synthesis of a basiliolide/transtaganolide model system are disclosed. A highly endo-selective intramolecular pyrone Diels-Alder (IMPDA) cycloaddition rapidly constructs the tricyclic core of the basiliolides and transtaganolides.
Subject(s)
Biological Products/chemical synthesis , Heterocyclic Compounds, Bridged-Ring/chemical synthesis , Models, Molecular , Thapsigargin/analogs & derivatives , Thapsigargin/chemical synthesis , Biological Products/chemistry , Biological Products/classification , Cyclization , Heterocyclic Compounds, Bridged-Ring/chemistry , Molecular Structure , Plants, Medicinal/chemistry , Pyrones/chemistry , Stereoisomerism , Thapsia/chemistry , Thapsigargin/chemistryABSTRACT
An investigation of Thapsia garganica afforded a series of tetracyclic C-19 dilactones, whose production was dependent on the time and location of the collection. These unusual tetrahomosesquiterpenoids are presumably biosynthesized via a carbon dioxide-triggered electrophilic polyolefin cyclization. Despite the structural differences with thapsigargin, these compounds showed SERCA-inhibiting properties.
Subject(s)
Apiaceae/chemistry , Calcium-Transporting ATPases/antagonists & inhibitors , Enzyme Inhibitors/isolation & purification , Plants, Medicinal/chemistry , Sea Urchins/enzymology , Thapsigargin , Animals , Enzyme Inhibitors/chemistry , Enzyme Inhibitors/pharmacology , Molecular Structure , Nuclear Magnetic Resonance, Biomolecular , Sarcoplasmic Reticulum Calcium-Transporting ATPases , Sea Urchins/metabolism , Stereoisomerism , Thapsigargin/analogs & derivatives , Thapsigargin/chemistry , Thapsigargin/metabolism , Thapsigargin/pharmacologyABSTRACT
OBJECTIVE: Prostate cancer cells secrete the unique protease human glandular kallikrein 2 (hK2) that represents a target for proteolytic activation of cytotoxic prodrugs. The objective of this study was to identify hK2-selective peptide substrates that could be coupled to a cytotoxic analogue of thapsigargin, a potent inhibitor of the sarcoplasmic/endoplasmic reticulum calcium ATPase pump that induces cell proliferation-independent apoptosis through dysregulation of intracellular calcium levels. METHODS: To identify peptide sequence requirements for hK2, a combination of membrane-bound peptides (SPOT analysis) and combinatorial chemistry using fluorescence-quenched peptide substrates was used. Peptide substrates were then coupled to 8-O-(12[L-leucinoylamino]dodecanoyl)-8-O-debutanoylthapsigargin (L12ADT), a potent analogue of thapsigargin, to produce a prodrug that was then characterized for hK2 hydrolysis, plasma stability, and in vitro cytotoxicity. RESULTS: Both techniques indicated that a peptide with two arginines NH2-terminal of the scissile bond produced the highest rates of hydrolysis. A lead peptide substrate with the sequence Gly-Lys-Ala-Phe-Arg-Arg (GKAFRR) was hydrolyzed by hK2 with a Km of 26.5 micromol/L, kcat of 1.09 s(-1), and a kcat/Km ratio of 41,132 s(-1) mol/L(-1). The GKAFRR-L12ADT prodrug was rapidly hydrolyzed by hK2 and was stable in plasma, whereas the GKAFRR-L peptide substrate was unstable in human plasma. The hK2-activated thapsigargin prodrug was not activated by cathepsin B, cathepsin D, and urokinase but was an excellent substrate for plasmin. The GKAFRR-L12ADT was selectively cytotoxic in vitro to cancer cells in the presence of enzymatically active hK2. CONCLUSION: The hK2-activated thapsigargin prodrug represents potential novel targeted therapy for prostate cancer.