Elgilda Musi

Synthesis, characterization, and in vitro antimalarial and antitumor activity of new ruthenium(II) complexes of chloroquine.

The new Ru(II) chloroquine complexes [Ru(eta(6)-arene)(CQ)Cl2] (CQ = chloroquine; arene = p-cymene 1, benzene 2), [Ru(eta(6)-p-cymene)(CQ)(H2O)2][BF4]2 (3), [Ru(eta(6)-p-cymene)(CQ)(en)][PF6]2 (en = ethylenediamine) (4), and [Ru(eta(6)-p-cymene)(eta(6)-CQDP)][BF4]2 (5, CQDP = chloroquine diphosphate) have been synthesized and characterized by use of a combination of NMR and FTIR spectroscopy with DFT calculations. Each complex is formed as a single coordination isomer: In 1-4, chloroquine binds to ruthenium in the eta(1)-N mode through the quinoline nitrogen atom, whereas in 5 an unprecedented eta(6) bonding through the carbocyclic ring is observed. 1, 2, 3, and 5 are active against CQ-resistant (Dd2, K1, and W2) and CQ-sensitive (FcB1, PFB, F32, and 3D7) malaria parasites (Plasmodium falciparum); importantly, the potency of these complexes against resistant parasites is consistently higher than that of the standard drug chloroquine diphosphate. 1 and 5 also inhibit the growth of colon cancer cells, independently of the p53 status and of liposarcoma tumor cell lines with the latter showing increased sensitivity, especially to 1 (IC50 8 microM); this is significant because this type of tumor does not respond to currently employed chemotherapies.

Safingol (L-threo-sphinganine) induces autophagy in solid tumor cells through inhibition of PKC and the PI3-kinase pathway.

Safingol, the synthetic L-threo- stereoisomer of endogenous (D-erythro-) sphinganine, is an inhibitor of protein kinase C and sphingosine kinase in vitro, and in some cell types has been implicated in ceramide generation and induction of apoptosis. Utilizing electron microscopy, acridine orange staining, and immunoblot and fluorescent localization studies of the myosin light chain-associated protein (LC3), we determined that safingol induces cell death of an exclusively autophagic character and lacking any of the hallmarks of apoptosis. Safingol inhibited PKCβ-I, PKCδ and PKCε, and inhibited phosphorylation of critical components of the PI3k/Akt/mTOR pathway (Akt, p70S6k, and rS6) and the MAPk pathway (ERK). Inhibition of PI3k with LY294002 or suppression of PKCδ and PKCε with siRNA in HCT-116 cells induced autophagy, though not to the extent caused by safingol. Conversely, activation of PKCs with phorbol 12,13-dibutyrate (PDBu) or transient transfection of a constitutively active form of Akt each reduced safingol’s autophagic induction, but not completely, indicating that Akt- and PKC-dependent pathways both contribute partially and independently to safingol-induced autophagy. Accordingly, combining siRNA depletion of PKCε with LY294002 inhibition of PI3k induced autophagy to degree comparable to safingol. Liquid chromatography, electrospray tandem mass spectrometry analysis indicated that safingol did not elevate levels of any endogenous sphingolipids previously shown to induce autophagy (ceramide, sphingosine-1-phosphate and dihydroceramide), therefore, these effects may be due to safingol per se or another metabolite. Thus, our studies establish that safingol induces autophagy through inhibition of PKCs and PI3k by safingol directly rather than via changes in endogenous sphingolipids.

The cyclin-dependent kinase inhibitor flavopiridol potentiates doxorubicin efficacy in advanced sarcomas: preclinical investigations and results of a phase I dose-escalation clinical trial

Purpose: Dysregulated cyclin-dependent kinases are important to the growth of some sarcomas. Flavopiridol is a pan-CDK inhibitor that has been shown to potentiate chemotherapy. As such, we explored the potentiation of doxorubicin by flavopiridol in sarcoma, in vitro and in vivo, and conducted a phase I trial of flavopiridol with doxorubicin in patients with advanced sarcomas. Experimental Design: Sarcoma cell lines and xenografts were treated with flavopiridol alone and in combination with doxorubicin. In the phase I study, doxorubicin and flavopiridol were administered on two flavopiridol schedules; a 1-hour bolus and split dosing as a 30-minute bolus followed by a 4-hour infusion. Results: Preclinically, flavopiridol potentiated doxorubicin. In vivo, doxorubicin administered 1 hour before flavopiridol was more active than doxorubicin alone. Clinically, 31 patients were enrolled on protocol and flavopiridol was escalated to target dose in two schedules (90 mg/m2 bolus; 50 mg/m2 bolus + 40 mg/m2 infusion) both in combination with doxorubicin (60 mg/m2). Dose-limiting toxicities were neutropenia, leukopenia, and febrile neutropenia but no maximum tolerated dose was defined. Flavopiridol pharmacokinetics showed increasing Cmax with increasing dose. Response Evaluation Criteria in Solid Tumors (RECIST) responses included two partial responses, however, stable disease was seen in 16 patients. Of 12 evaluable patients with progressive well- and dedifferentiated liposarcoma, eight had stable disease greater than 12 weeks. Conclusions: The sequential combination of doxorubicin followed by flavopiridol is well tolerated on both schedules. Disease control was observed in well- and dedifferentiated liposarcoma specifically, a disease in which CDK4 is known to be amplified. Clin Cancer Res; 18(9); 2638–47. ©2012 AACR.

Inhibition of Mutant GNAQ Signaling in Uveal Melanoma Induces AMPK-Dependent Autophagic Cell Death

Oncogenic mutations in GNAQ and GNA11 genes are found in 80% of uveal melanoma. These mutations result in the activation of the RAF/MEK signaling pathway culminating in the stimulation of ERK1/2 mitogen-activated protein kinases. In this study, using a siRNA strategy, we show that mutant GNAQ signals to both MEK and AKT, and that combined inhibition of these pathways with the MEK inhibitor selumetinib (AZD6244) and the AKT inhibitor MK2206 induced a synergistic decrease in cell viability. This effect was genotype dependent as autophagic markers like beclin1 and LC3 were induced in GNAQ-mutant cells, whereas apoptosis was the mechanism of cell death of BRAF-mutant cells, and cells without either mutation underwent cell-cycle arrest. The inhibition of MEK/ATK pathways induced activation of AMP-activated protein kinase (AMPK) in the GNAQ-mutant cells. The downregulation of AMPK by siRNA or its inhibition with compound C did not rescue the cells from autophagy, rather they died by apoptosis, defining AMPK as a key regulator of mutant GNAQ signaling and a switch between autophagy and apoptosis. Furthermore, this combination treatment was effective in inhibiting tumor growth in xenograft mouse models. These findings suggest that inhibition of MEK and AKT may represent a promising approach for targeted therapy of patients with uveal melanoma. Mol Cancer Ther; 12(5); 768–76. ©2013 AACR.

Impact of combined mTOR and MEK inhibition in uveal melanoma is driven by tumor genotype.

Uveal melanomas possess activation of the mitogen-activated protein kinase (MAPK) and phosphoinositide 3-kinase (PI3K)/AKT/mammalian Target of Rapamycin (mTOR) pathways. MAPK activation occurs via somatic mutations in the heterotrimeric G protein subunits GNAQ and GNA11 for over 70% of tumors and less frequently via V600E BRAF mutations. In this report, we describe the impact of dual pathway inhibition upon uveal melanoma cell lines with the MEK inhibitor selumetinib (AZD6244/ARRY-142886) and the ATP-competitive mTOR kinase inhibitor AZD8055. While synergistic reductions in cell viability were observed with AZD8055/selumetinib in both BRAF and GNAQ mutant cell lines, apoptosis was preferentially induced in BRAF mutant cells only. In vitro apoptosis assay results were predictive of in vivo drug efficacy as tumor regressions were observed only in a BRAF mutant xenograft model, but not GNAQ mutant model. We went on to discover that GNAQ promotes relative resistance to AZD8055/selumetinib-induced apoptosis in GNAQ mutant cells. For BRAF mutant cells, both AKT and 4E-BP1 phosphorylation were modulated by the combination; however, decreasing AKT phosphorylation alone was not sufficient and decreasing 4E-BP1 phosphorylation was not required for apoptosis. Instead, cooperative mTOR complex 2 (mTORC2) and MEK inhibition resulting in downregulation of the pro-survival protein MCL-1 was found to be critical for combination-induced apoptosis. These results suggest that the clinical efficacy of combined MEK and mTOR kinase inhibition will be determined by tumor genotype, and that BRAF mutant malignancies will be particularly susceptible to this strategy.

The Phosphoinositide 3-Kinase α Selective Inhibitor BYL719 Enhances the Effect of the Protein Kinase C Inhibitor AEB071 in GNAQ/GNA11-Mutant Uveal Melanoma Cells

G-protein mutations are one of the most common mutations occurring in uveal melanoma activating the protein kinase C (PKC)/mitogen-activated protein kinase and phosphoinositide 3-kinase (PI3K)/AKT pathways. In this study, we described the effect of dual pathway inhibition in uveal melanoma harboring GNAQ and GNA11 mutations via PKC inhibition with AEB071 (sotrastaurin) and PI3K/AKT inhibition with BYL719, a selective PI3Kα inhibitor. Growth inhibition was observed in GNAQ/GNA11-mutant cells with AEB071 versus no activity in wild-type cells. In the GNAQ-mutant cells, AEB071 decreased phosphorylation of myristoylated alanine-rich C-kinase substrate, a substrate of PKC, along with ERK1/2 and ribosomal S6, but persistent AKT activation was present. BYL719 had minimal antiproliferative activity in all uveal melanoma cell lines, and inhibited phosphorylation of AKT in most cell lines. In the GNA11-mutant cell line, similar effects were observed with ERK1/2 inhibition, mostly inhibited by BYL719. With the combination treatment, both GNAQ- and GNA11-mutant cell lines showed synergistic inhibition of cell proliferation and apoptotic cell death. In vivo studies correlated with in vitro findings showing reduced xenograft tumor growth with the combination therapy in a GNAQ-mutant model. These findings suggest a new therapy treatment option for G-protein–mutant uveal melanoma with a focus on specific targeting of multiple downstream pathways as part of combination therapy. Mol Cancer Ther; 13(5); 1044–53. ©2014 AACR.

BRD4-targeted therapy induces Myc-independent cytotoxicity in Gnaq/11-mutatant uveal melanoma cells.

Uveal melanoma (UM) is an aggressive intraocular malignancy with limited therapeutic options. Both primary and metastatic UM are characterized by oncogenic mutations in the G-protein alpha subunit q and 11. Furthermore, nearly 40% of UM has amplification of the chromosomal arm 8q and monosomy of chromosome 3, with consequent anomalies of MYC copy number. Chromatin regulators have become attractive targets for cancer therapy. In particular, the bromodomain and extra-terminal (BET) inhibitor JQ1 has shown selective inhibition of c-Myc expression with antiproliferative activity in hematopoietic and solid tumors. Here we provide evidence that JQ1 had cytotoxic activity in UM cell lines carrying Gnaq/11 mutations, while in cells without the mutations had little effects. Using microarray analysis, we identified a large subset of genes modulated by JQ1 involved in the regulation of cell cycle, apoptosis and DNA repair. Further analysis of selected genes determined that the concomitant silencing of Bcl-xL and Rad51 represented the minimal requirement to mimic the apoptotic effects of JQ1 in the mutant cells, independently of c-Myc. In addition, administration of JQ1 to mouse xenograft models of Gnaq-mutant UM resulted in significant inhibition of tumor growth. Collectively, our results define BRD4 targeting as a novel therapeutic intervention against UM with Gnaq/Gna11 mutations.

Significant blockade of multiple receptor tyrosine kinases by MGCD516 (Sitravatinib), a novel small molecule inhibitor, shows potent anti-tumor activity in preclinical models of sarcoma

Sarcomas are rare but highly aggressive mesenchymal tumors with a median survival of 10–18 months for metastatic disease. Mutation and/or overexpression of many receptor tyrosine kinases (RTKs) including c-Met, PDGFR, c-Kit and IGF1-R drive defective signaling pathways in sarcomas. MGCD516 (Sitravatinib) is a novel small molecule inhibitor targeting multiple RTKs involved in driving sarcoma cell growth. In the present study, we evaluated the efficacy of MGCD516 both in vitro and in mouse xenograft models in vivo. MGCD516 treatment resulted in significant blockade of phosphorylation of potential driver RTKs and induced potent anti-proliferative effects in vitro. Furthermore, MGCD516 treatment of tumor xenografts in vivo resulted in significant suppression of tumor growth. Efficacy of MGCD516 was superior to imatinib and crizotinib, two other well-studied multi-kinase inhibitors with overlapping target specificities, both in vitro and in vivo. This is the first report describing MGCD516 as a potent multi-kinase inhibitor in different models of sarcoma, superior to imatinib and crizotinib. Results from this study showing blockade of multiple driver signaling pathways provides a rationale for further clinical development of MGCD516 for the treatment of patients with soft-tissue sarcoma.

Abstract 4526: BIBF1120, an investigational triple angiokinase inhibitor, in combination with inhibitors of mTOR signaling shows potent antitumor activity in preclinical models of sarcoma

Proceedings: AACR Annual Meeting 2014; April 5-9, 2014; San Diego, CA BIBF1120 (Nintedanib), an investigational potent small molecule angiokinase inhibitor, selectively binds to and blocks receptor tyrosine kinases (RTKs) such as vascular endothelial growth factor receptor, (VEGFR), fibroblast growth factor receptor (FGFR) and platelet derived growth factor receptor (PDGFR). Nintedanib has shown promising results in preclinical as well as clinical studies of non-small cell lung cancer, colorectal, ovarian cancer and other solid tumors. We tested the in vitro anti-proliferative activity of BIBF1120 in a panel of sarcoma cell lines including malignant peripheral nerve sheath tumor (MPNST), synovial (SYO-I), Ewings (CHP100), osteo (SaOS2) and liposarcoma (LS141). Our results indicate that when compared to other potent RTK inhibitors such as Imatinib and Pazopanib, BIBF1120 is highly efficient at nanomolar to low micromolar concentrations in blocking proliferative activity of sarcoma cell lines, specifically, SYO-I and MPNST, which are highly dependent on PDGFR signaling. Western blot analysis to test the efficacy of BIBF1120 confirmed significant blockade of RTK signaling pathways. Ras activation and/or activation of mitogen activated protein kinase (MAPK) pathway has been shown to be critical in sarcomas including MPNST and synovial sarcomas. Unlike Imatinib and Pazopanib, BIBF1120 also blocked MAPK signaling pathway as demonstrated by p-ERK1/2 blockade. In addition to the RTKs, mTOR (mammalian Target of Rapamycin) protein plays a key role in AKT activation and downstream survival signaling. Combination of RTK blockade by BIBF1120 and mTOR blockade by TORC1 inhibitor rapamycin resulted in significantly stronger inhibition of in vitro cellular proliferation compared to single agent treatments. Taken together, our data strongly supports further clinical research of BIBF1120 in sarcoma. Combining potent inhibitors of tyrosine kinase signaling, MAPK signaling and inhibitors of mTOR pathway such as rapamycin could provide a new therapeutic approach in this disease. Citation Format: Parag P. Patwardhan, Elgilda Musi, Kathryn S. Ivy, Natalie Giovino, Gary K. Schwartz. BIBF1120, an investigational triple angiokinase inhibitor, in combination with inhibitors of mTOR signaling shows potent antitumor activity in preclinical models of sarcoma. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 4526. doi:10.1158/1538-7445.AM2014-4526

Abstract 2073: The parp inhibitor olaparib (AZD2281) greatly enances the effect of temozolomide in soft tissue sarcoma cell lines.

Sarcomas are heterogeneous mesenchymal neoplasms which have very limited treatment options. Chemotherapies for advanced sarcoma include DNA damaging agents such as doxorubicin, dacarbazine and gemcitabine with very low response rates. We elected to study the effects of olaparib (AZD2281), a novel, potent orally active PARP inhibitor in combination with standard chemotherapy Temozolomide (TMZ) in various sarcoma subtypes. We examined the effects of olaparib and TMZ in a panel of 7 sarcoma cell lines including leiomyosarcoma (SK-LMS, SK-UT1, SK-UT1b), liposarcoma (LS141, DDLS) and malignant peripheral nerve sheath tumors (MPNST, ST8814). In vitro results have shown inhibition of cell viability with combination treatment in all cell lines at concentrations of 300uM TMZ and 1 uM olaparib. After 48 hrs of drug treatment, we also examined biochemical effects showing PAR inhibition, p53 induction and γH2AX increase, indicative of DNA damage. Flow cytometric analysis of each cell line indicated G2/M cell cycle arrest with combination treatment. These observations correlated with enhanced apoptosis as measured by biochemical PARP cleavage and DNA content (sub-G1 population). Taking these observations and results, there is strong evidence to support combining standard chemotherapy TMZ with the PARP inhibitor olaparib in various sarcoma subtypes. Citation Format: Elgilda Musi, Grazia Ambrosini, Gary K. Schwartz. The parp inhibitor olaparib (AZD2281) greatly enances the effect of temozolomide in soft tissue sarcoma cell lines. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 2073. doi:10.1158/1538-7445.AM2013-2073