Synergistic effect of Sorafenib and Sunitinib with Enzastaurin, a selective protein kinase C inhibitor in renal cell carcinoma cell lines

Convection-enhanced delivery of sorafenib and suppression of tumor progression in a murine model of brain melanoma through the inhibition of signal transducer and activator of transcription 3

OBJECT Despite recent advances, metastatic melanoma remains a terminal disease, in which life-threatening brain metastasis occurs in approximately half of patients. Sorafenib is a multikinase inhibitor that induces apoptosis of melanoma cells in vitro. However, systemic administration has been ineffective because adequate tissue concentrations cannot be achieved. This study investigated if convection-enhanced delivery (CED) of sorafenib would enhance tumor control and survival via inhibition of the signal transducer and activator of transcription 3 (Stat3) pathway in a murine model of metastatic brain melanoma. METHODS Melanoma cells treated with sorafenib in vitro were examined for signaling and survival changes. The effect of sorafenib given by CED was assessed by bioluminescent imaging and animal survival. RESULTS The results showed that sorafenib induced cell death in the 4 established melanoma cell lines and in 1 primary cultured melanoma cell line. Sorafenib inhibited Stat3 phosphorylation in HTB65, WYC1, and B16 cells. Accordingly, sorafenib treatment also decreased expression of Mcl-1 mRNA in melanoma cell lines. Because sorafenib targets multiple pathways, the present study demonstrated the contribution of the Stat3 pathway by showing that mouse embryonic fibroblast (MEF) Stat3 +/+ cells were significantly more sensitive to sorafenib than MEF Stat3 -/- cells. In the murine model of melanoma brain metastasis used in this study, CED of sorafenib increased survival by 150% in the treatment group compared with animals receiving the vehicle control (p < 0.01). CED of sorafenib also significantly abrogated tumor growth. CONCLUSIONS The data from this study indicate that local delivery of sorafenib effectively controls brain melanoma. These findings validate further investigation of the use of CED to distribute molecularly targeted agents.

A phase 1 and pharmacokinetic study of enzastaurin in pediatric patients with refractory primary central nervous system tumors: a pediatric brain tumor consortium study

BACKGROUND

We sought to estimate the maximum tolerated or recommended phase 2 dose and describe the pharmacokinetics and toxicities of enzastaurin, an oral inhibitor of protein kinase Cβ, in children with recurrent central nervous system malignancies.

METHODS

Enzastaurin was administered continuously once daily at 3 dose levels (260, 340, and 440 mg/m(2)) and twice daily at 440 mg/m(2)/day. Plasma pharmacokinetics were evaluated following a single dose and at steady state. Inhibition of protein kinase C and Akt cell signaling in peripheral blood mononuclear cells was evaluated. Akt pathway activity was measured in pretreatment tumor samples.

RESULTS

Thirty-three patients enrolled; 1 was ineligible, and 3 were nonevaluable secondary to early progressive disease. There were no dose-limiting toxicities during the dose-finding phase. Two participants receiving 440 mg/m(2) given twice daily experienced dose-limiting toxicities of grade 3 thrombocytopenia resulting in delayed start of course 2 and grade 3 alanine transaminase elevation that did not recover within 5 days. There were no grade 4 toxicities during treatment. The concentration of enzastaurin increased with increasing dose and with continuous dosing; however, there was not a significant difference at the 440 mg/m(2) dosing level when enzastaurin was administered once daily versus twice daily. There were no objective responses; however, 11 participants had stable disease >3 cycles, 7 with glioma, 2 with ependymoma, and 2 with brainstem glioma.

CONCLUSION

Enzastaurin was well tolerated in children with recurrent CNS malignancies, with chromaturia, fatigue, anemia, thrombocytopenia, and nausea being the most common toxicities. The recommended phase 2 dose is 440 mg/m(2)/day administered once daily.

Sorafenib and lithium chloride combination treatment shows promising synergistic effects in human glioblastoma multiforme cells in vitro but midkine is not implicated

OBJECTIVES

The objectives of this study were to test the effects of the new combination treatment modality, sorafenib (SOR) and lithium chloride (LiCl) and to assess whether midkine (MK) protein has a role in any potential effects.

METHODS

Monolayer and spheroid cultures of T98G human glioblastoma multiforme (GBM) cells were treated with LiCl and SOR (inhibition concentration 50 value  =  100 μM), or their combination, or were left untreated (control). Cell proliferation and apoptotic indices, the mechanism of action, and the levels of apoptotic and anti-apoptotic proteins were evaluated in monolayer cultures and ultrastructure was evaluated by transmission electron microscopy (TEM) in spheroid cultures after for 72 hours.

RESULTS

All drug applications decreased cell numbers and increased the apoptotic index. The combination shows a synergistic effect. In the combination group, the decrease in cell numbers and the increase in the apoptotic index were significantly greater than with the individual drugs (P < 0.01). The combination treatment led to the greatest decreases in MRP-1 and p170 levels; but the greatest decreases in p-STAT-3, p-ERK (P < 0.05), p-AKT, p-GSK-3-beta (P < 0.01), EGFR (P < 0.01), NF-kappa-β levels were with SOR alone, followed by the combination. The decreases in MK levels in the SOR and combination groups were similar (P  =  0.06). Severe ultrastructural damage was more frequently observed in the combination group compared with the other groups.

CONCLUSIONS

These results suggest the possibility that the addition of LiCl to SOR could improve the prognosis in at least some patients who need both cancer and psychotherapy and indicate the need for further studies.

Protein kinase C-beta inhibition induces apoptosis and inhibits cell cycle progression in acquired immunodeficiency syndrome-related non-hodgkin lymphoma cells

INTRODUCTION

Acquired immunodeficiency syndrome (AIDS)-related non-Hodgkin lymphoma (NHL) constitutes an aggressive variety of lymphomas characterized by increased extranodal involvement, relapse rate, and resistance to chemotherapy. Protein kinase C-beta (PKCβ) targeting showed promising results in preclinical and clinical studies involving a wide variety of cancers, but studies describing the role of PKCβ in AIDS-NHL are primitive if not lacking.

METHODS

In the present study, 3 AIDS-NHL cell lines were examined: 2F7 (AIDS-Burkitt lymphoma), BCBL-1 (AIDS-primary effusion lymphoma), and UMCL01-101 (AIDS-diffuse large B-cell lymphoma).

RESULTS

Immunoblot analysis demonstrated expression of PKCβ1 and PKCβ2 in 2F7 and UMCL01-101 cells, and PKCβ1 alone in BCBL-1 cells. The viability of 2F7 and BCBL-1 cells decreased significantly in the presence of PKCβ-selective inhibitor at half-maximal inhibitory concentration of 14 and 15 μmol/L, respectively, as measured by tetrazolium dye reduction assay. In contrast, UMCL01-101 cells were relatively resistant. As determined using flow cytometric deoxynucleotidyl transferase dUTP nick-end labeling assay with propidium iodide staining, the responsiveness of sensitive cells was associated with apoptotic induction and cell cycle inhibition. Protein kinase C-beta-selective inhibition was observed not to affect AKT phosphorylation but to induce a rapid and sustained reduction in the phosphorylation of glycogen synthase kinase-3 beta, ribosomal protein S6, and mammalian target of rapamycin in sensitive cell lines.

CONCLUSIONS

The results indicate that PKCβ plays an important role in AIDS-related NHL survival and suggest that PKCβ targeting should be considered in a broader spectrum of NHL. The observations in BCBL-1 were unexpected in the absence of PKCβ2 expression and implicate PKCβ1 as a regulator in those cells.

Apoptotic induction in B-cell acute lymphoblastic leukemia cell lines treated with a protein kinase Cβ inhibitor

B-cell acute lymphoblastic leukemia (B-ALL) in adults exhibits a 5-year disease-free survival rate of only 25-40% after currently available treatment. Protein kinase Cβ (PKCβ) is under active consideration as a rational therapeutic target in several B-cell malignancies, but studies of its possible utility in B-ALL are lacking. Expression of PKCβ1 and PKCβ2 isoforms was demonstrated in five B-ALL cell lines characterized by distinctive chromosomal translocations, and sensitivity to PKCβ-selective inhibition was examined. Inhibitor treatment resulted in a dose-dependent reduction in viability in all cell lines, although pro-B ALL with t(4;11)(q21;q23) was most sensitive. Apoptotic induction was evident after 24-48 h of treatment, and an inhibition of cell cycle progression was detected in one cell line. Treatment resulted in a rapid induction of poly(ADP-ribose) polymerase (PARP) cleavage, indicating caspase-3-mediated apoptosis, and a rapid reduction in phosphorylation of AKT and its downstream target glycogen synthase kinase 3β (GSK3β). These results indicate that PKCβ targeting should be considered as a potential treatment option in B-ALL.

Sunitinib malate synergistically potentiates anti-tumor effect of gemcitabine in human bladder cancer cells

PURPOSE

Sunitinib malate (Sutent; Pfizer, New York, NY, USA) is a highly selective multi-targeted agent and has been reported to have potent anti-tumor effects against various tumors, including renal cell carcinoma and gastrointestinal stromal tumors. In this study, we explored in vitro the anti-tumor effect and related molecular mechanisms of sunitinib malate against human bladder cancer cell lines. We also determined the synergistic anti-tumor effect between sunitinib and conventional cytotoxic drugs, cisplatin and gemcitabine, in bladder cancer cells.

MATERIALS AND METHODS

Six human cancer cell lines (HTB5, HTB9, T24, UMUC14, SW1710, and J82) were exposed to an escalating dose of sunitinib alone or in combination with cisplatin/gemcitabine, and the cytotoxic effect of the drugs was examined by CCK-8 assay. The synergistic effect between sunitinib and cisplatin/gemcitabine was determined by the combination index (CI) and clonogenic assay. Alterations in cell cycle (cyclin D, B1), survival (p-Akt, t-Akt), and apoptosis (Bax, Bad) regulator expression were analyzed by Western blotting.

RESULTS

Like cisplatin and gemcitabine, sunitinib exerted a dose- and time-dependent anti-tumor effect in bladder cancer cells. However, sunitinib exhibited entirely different sensitivity profiles from cisplatin and gemcitabine. Sunitinib suppressed the expression of cyclin B1, p-Akt, and t-Akt while augmenting the expression of cyclin D and pro-apoptotic Bax and Bad in HTB5 cells. Analysis of the drug combination by the isobolic method and clonogenic assay revealed that sunitinib acts in synergy with gemcitabine in HTB5 cells.

CONCLUSIONS

These results indicate that sunitinib malate has a potent anti-tumor effect and may synergistically enhance the anti-tumor effect of gemcitabine in human bladder cancer cells.

GSK3beta: role in therapeutic landscape and development of modulators

Glycogen synthase kinase-3 beta (GSK3beta) is a multifunctional serine/threonine kinase which was originally identified as a regulator of glycogen metabolism. It plays a key role in the regulation of numerous signalling pathways including cellular process such as cell cycle, inflammation and cell proliferation. Over the last few years there is a considerable rise in the number of journals and patents publication by different workers worldwide. Many pharmaceutical companies are focusing on GSK3beta as a therapeutic target for the treatment of disease conditions. The present review is focused on signalling pathways of different disease conditions where GSK3beta is implicated. In this review, we present a comprehensive map of GSK3beta signalling pathways in disease physiologies. Structural analysis of GSK3beta along with molecular modelling reports from numerous workers are reviewed in context of design and development of GSK3beta inhibitors. Patent landscape of the small molecule modulators is profiled. The chemo space for small molecule modulators extracted from public and proprietary Kinase Chembiobase for GSK3beta are discussed. Compounds in different clinical phases of discovery are analysed. The review ends with the overall status of this important therapeutic target and challenges in development of its modulators.

Enzastaurin shows preclinical antitumor activity against human transitional cell carcinoma and enhances the activity of gemcitabine

Enzastaurin, an oral serine/threonine kinase inhibitor, suppresses signaling through protein kinase C (PKC)-beta and the phosphatidylinositol 3-kinase/AKT pathways. We preclinically evaluated enzastaurin alone and in combination with gemcitabine for transitional cell cancer (TCC). Immunohistochemistry (IHC) was done on 105 human samples from a microarray to show the expression of PKC-beta. The preclinical antitumor activity of enzastaurin and gemcitabine as single agents and in combination against aggressive human -lines (-SUP and 5637) and murine subcutaneous xenografts bearing 5637 cells was determined. Western Blot was done on tumor cells in vitro to detect signaling through PKC-beta, GSK-3beta, and AKT. The effect on cell migration was determined in vitro. Modulation of proliferation (Ki-67), apoptosis (cleaved caspase-3), and angiogenesis (CD31) in vivo was determined by IHC. IHC done on human TCC samples from a microarray showed the expression of PKC-beta in 33% of tumors. Enzastaurin induced significant apoptosis and inhibited proliferation in vitro at low micromolar concentrations. The in vitro inhibitory activity of combination enzastaurin and gemcitabine by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay seemed synergistic. Western Blotting revealed down-regulation of Akt, PKC-beta, and GSK-3 beta phosphorylation. Enzastaurin inhibited migration at an earlier time point independent of antiproliferative activity. Combination therapy had significantly superior antitumor activity in murine xenografts compared with untreated controls, whereas single agents did not. IHC showed reduced Ki-67 and CD31 and increased cleaved caspase-3 with combination therapy compared with controls. Enzastaurin showed preclinical antitumor activity against human TCC and enhanced the activity of gemcitabine.