Choose Your Country or Region

ENZASTAURIN AGAINST MALIGNANCIES

by Selleckchem | Mar 20 2012

Introduction: The Protein Kinase C family

A cytosolic protein kinase isolated in the late 1970’s by the Nishizuka group of Kobe University, Japan [1] has been found to be a key factor in the regulation of the cell cycle. Established as the protein kinase C family several isoforms have subsequently be isolated [2]. These serine / threonine kinases are activated by the diacylglycerol (DAG) which is generated by the agonist induced hydrolysis of Trans-membrane G-protein kinases or tyrosine kinases. Activation of protein kinase C leads to a movement of the protein to the either the cytosolic skeleton or to the cellular membrane triggering a cascade of downstream signals which induce cell growth, differentiation or proliferation activities [3], this process appears to be mediated by the release of Ca²⁺ [4;5]. One of the key elements to be discovered concerning this protein was the discovery that phorbol esters were also a ligand for activating this protein; this created a direct link between PKC and the formation of various tumors [6;7]. Further insight into the mechanisms behind this protein family demonstrates roles in the cell cycle, where PKC was determined to critical for entry of cells into the G0 and G1 phase while it was heavily involved in the mechanisms of the G0 and G1 check point proteins [8-10]. PKc proteins have been found to be downstream targets for VEGFR [11] and EGFR [11-13]. The relative importance of this family of proteins makes it an ideal target for inhibition in relation to tumor growth or proliferation.

The Enzastaurin PKC beta inhibitor is a small molecule designed to inhibit this kinase by competitive binding to the tyrosine kinase ATP domain. Inhibition at this level halts signals promoting survival and re-growth of damaged cells. It has been demonstrated that Enzastarin is a potent anti-tumor molecules and has received a great deal of attention in recent times.

Enzastaurin: Properties and Availability

Developed by the Eli Lily pharmaceuticals Enzastaurin is extensively listed in literature under the code names LY-317615 and D04014. Enzasaurin has demonstrated activity towards the PKC ß isoform with an Enzastaurin IC50 of 6nM, relative to the IC50’s for the α, ε and γ isoforms (39, 110 & 83 nM).Enzastaurin solubility in DMSO is limited compared to similar compounds achieving only a 7.1 mg /ml saturated solution after gentle warming. In ethanol and aqueous solutions the solubility is lower limiting buffer concentrations to 1 – 10 µM. However, Enzastaurin stability has been determined to be reasonable in the solid state while caution should be taken to store solutions at -20°C or lower until required. To buy Enzastaurin there are various Enzastaurin suppliers with 99% pure product available with Enzastaurin prices ranging from $212 to $576 for 50 mg samples.

Enzastaurin: Preclinical investigations

Enzastaurin as specificity at low concentrations toward the PKC ß isoforms with some activity towards the α, ε and γ isoforms. In addition it has been established that Enzastaurin has activity towards GSK3ß (also known as SER⁹) and towards the ribosomal protein S6 ( also known as SER^240/244) [14] Against a panel of SCLC and nSCLC cell lines Enzastaurin demonstrated low µM sensitivity, inhibiting cell growth and exhibiting a decrease in GSK activity [14-16]In various animal models Enzastaurin has demonstrated prolific anti tumor activity in a range of tumor types ( renal, hepatic and colon) [17-21]. Synergistically Enzastaurin has demonstrated good sensitivity in combination with tyrosine kinase inhibitors, platinum compounds and other first line traditional treatment profiles [22-27].

Enzastaurin: Clinical status

Enzastaurin clinical trials are onging for a variety of conditions such Malignant Gliomas, refractory mantle cell lymphoma, tumors of the central nervous system, non hodgkin’s lymphomas, breast cancer and glioblastoma multiforme to name only a few of the many avenues of investigation that are being pursued for this molecule.

References

1. Inoue M, Kishimoto A et al. Studies on a cyclic nucleotide-independent protein kinase and its proenzyme in mammalian tissues. II. Proenzyme and its activation by calcium-dependent protease from rat brain. J Biol Chem 1977; 252(21):7610-7616.

2. Bynagari-Settipalli YS, Chari R et al. Protein kinase C - possible therapeutic target to treat cardiovascular diseases. Cardiovasc Hematol Disord Drug Targets 2010; 10(4):292-308.

3. Takai Y, Kishimoto A et al. Unsaturated diacylglycerol as a possible messenger for the activation of calcium-activated, phospholipid-dependent protein kinase system. Biochem Biophys Res Commun 1979; 91(4):1218-1224.

4. Nakamura S, Asaoka Y et al. Protein kinase C for cell signaling: a possible link between phospholipases. Adv Second Messenger Phosphoprotein Res 1993; 28:171-178.

5. Asaoka Y, Nakamura S et al. Protein kinase C, calcium and phospholipid degradation. Trends Biochem Sci 1992; 17(10):414-417.

6. Asaoka Y, Oka M et al. Metabolic rate of membrane-permeant diacylglycerol and its relation to human resting T-lymphocyte activation. Proc Natl Acad Sci U S A 1991; 88(19):8681-8685.

7. Asaoka Y, Oka M et al. Lysophosphatidylcholine as a possible second messenger synergistic to diacylglycerol and calcium ion for T-lymphocyte activation. Biochem Biophys Res Commun 1991; 178(3):1378-1385.

8. Frey MR, Clark JA et al. Protein kinase C signaling mediates a program of cell cycle withdrawal in the intestinal epithelium. J Cell Biol 2000; 151(4):763-778.

9. Vrana JA, Saunders AM et al. Divergent effects of bryostatin 1 and phorbol myristate acetate on cell cycle arrest and maturation in human myelomonocytic leukemia cells (U937). Differentiation 1998; 63(1):33-42.

10. Vrana JA, Rao AS et al. Effects of bryostatin 1 and calcium ionophore (A23187) on apoptosis and differentiation in human myeloid leukemia cells (HL-60) following 1-beta-D-arabinofuranosylcytosine exposure. Int J Oncol 1998; 12(4):927-934.

11. Rahimi N. VEGFR-1 and VEGFR-2: two non-identical twins with a unique physiognomy. Front Biosci 2006; 11:818-829.

12. Blask DE, Sauer LA et al. Melatonin as a chronobiotic/anticancer agent: cellular, biochemical, and molecular mechanisms of action and their implications for circadian-based cancer therapy. Curr Top Med Chem 2002; 2(2):113-132.

13. Klein C, Malviya AN. Mechanism of nuclear calcium signaling by inositol 1,4,5-trisphosphate produced in the nucleus, nuclear located protein kinase C and cyclic AMP-dependent protein kinase. Front Biosci 2008; 13:1206-1226.

14. Graff JR, McNulty AM et al. The protein kinase Cbeta-selective inhibitor, Enzastaurin (LY317615.HCl), suppresses signaling through the AKT pathway, induces apoptosis, and suppresses growth of human colon cancer and glioblastoma xenografts. Cancer Res 2005; 65(16):7462-7469.

15. Herbst RS, Oh Y et al. Enzastaurin, a protein kinase Cbeta- selective inhibitor, and its potential application as an anticancer agent in lung cancer. Clin Cancer Res 2007; 13(15 Pt 2):s4641-s4646.

16. Oh Y, Herbst RS et al. Enzastaurin, an oral serine/threonine kinase inhibitor, as second- or third-line therapy of non-small-cell lung cancer. J Clin Oncol 2008; 26(7):1135-1141.

17. Hanauske AR, Oberschmidt O et al. Antitumor activity of enzastaurin (LY317615.HCl) against human cancer cell lines and freshly explanted tumors investigated in in-vitro [corrected] soft-agar cloning experiments. Invest New Drugs 2007; 25(3):205-210.

18. Fields AP, Calcagno SR et al. Protein kinase Cbeta is an effective target for chemoprevention of colon cancer. Cancer Res 2009; 69(4):1643-1650.

19. Vogl UM, Berger W et al. Synergistic effect of Sorafenib and Sunitinib with Enzastaurin, a selective protein kinase C inhibitor in renal cell carcinoma cell lines. Cancer Lett 2009; 277(2):218-226.

20. Schmidinger M, Szczylik C et al. Dose Escalation and Pharmacokinetics Study of Enzastaurin and Sunitinib Versus Placebo and Sunitinib in Patients With Metastatic Renal Cell Carcinoma. Am J Clin Oncol 2011.

21. Yang JI, Yoon JH et al. Synergistic antifibrotic efficacy of statin and protein kinase C inhibitor in hepatic fibrosis. Am J Physiol Gastrointest Liver Physiol 2010; 298(1):G126-G132.

22. Oberschmidt O, Eismann U et al. Enzastaurin and pemetrexed exert synergistic antitumor activity in thyroid cancer cell lines in vitro. Int J Clin Pharmacol Ther 2005; 43(12):603-604.

23. Butowski N, Chang SM et al. Enzastaurin plus temozolomide with radiation therapy in glioblastoma multiforme: a phase I study. Neuro Oncol 2010; 12(6):608-613.

24. Jian W, Yamashita H et al. Enzastaurin shows preclinical antitumor activity against human transitional cell carcinoma and enhances the activity of gemcitabine. Mol Cancer Ther 2009; 8(7):1772-1778.

25. Richards DA, Kuefler PR et al. Gemcitabine plus enzastaurin or single-agent gemcitabine in locally advanced or metastatic pancreatic cancer: results of a phase II, randomized, noncomparative study. Invest New Drugs 2011; 29(1):144-153.

26. Bodo J, Sedlak J et al. HDAC inhibitors potentiate the apoptotic effect of enzastaurin in lymphoma cells. Apoptosis 2011; 16(9):914-923.

27. Baumann P, Armann J et al. Inhibitors of protein kinase C sensitise multiple myeloma cells to common genotoxic drugs. Eur J Haematol 2008; 80(1):37-45.