In vitro chemotherapeutic and antiangiogenic properties of cardenolides from Acokanthera oblongifolia (Hochst.) Codd

Acovenoside A and acobioside A were isolated from Acokanthera oblongifolia. Their anticancer properties were explored regarding, antiproliferative and antiangiogenic activities. The study included screening phase against six cancer cell lines followed by mechanistic investigation against HepG2 cancer cell line. The sulforhodamine-B (SRB) was used to determine their growth inhibitory power. In the other hand, flow cytometry techniques were recorded the cell death type and cell cycle analysis. The clonogenic (colony formation) and wound healing assays, enzyme-linked immunosorbent assay (ELISA) and molecular docking, were performed to evaluate the antiangiogenesis capability. Both compounds were strongly, inhibited four cancer cell lines at GI50 less than 100 nM. The in vitro mechanistic investigation against HepG2 resulted in cell accumulations at G2M phase and induction of apoptosis upon treating cells separately, with 400 nM Acov-A and 200 nM Acob-A. Interestingly, the same concentrations were able to activate caspase-3 by 7.2 and 4.8-fold, respectively. Suppressing the clonogenic capacity of HepG2 cells (20 and 40 nM) and inhibiting the migration of the colon Caco-2 cancer cells were provoke the results of vascular endothelial growth factor receptor2 (VEGFR2) kinase enzyme inactivation. The docked study was highly supportive, to the antiangiogenic approach of both cardenolides. The isolated cardenolides could orchestrate pivotal events in fighting cancer.

A strategy for clinical guidance using PD biomarkers revealed from human primary (HuPrime) tumors transplanted in nude mice

e14612 Background: Most anticancer drug candidates, currently in clinical trials, have clear targets in molecular and cellular systems. However, such molecular targets are not always affected (or not correlated with efficacious endpoints) when the candidate is evaluated in a clinical setting. There is an urgent need to develop better biological tools and models to ease the transition between in vitro and in vivo, and between preclinical and clinical settings. Activation of tyrosine kinases in tumor cells has been recognized as key driving force in malignancy; therefore inhibitors of tyrosine kinases (TKI) have often shown efficacy in preclinical in vivo models and beneficial responses in clinical trials. An increasing number of TKI has been approved as anticancer drugs in selected cancer types. Methods: We have developed a unique platform combining our novel HuPrime™ xenograft models with our PD biomarker technologies. This platform is used to better understand the efficacy of novel drug candidates and generate information critical to maximize the chance of a successful clinical development. To illustrate the usefulness of our platform, we have applied it to understand the pharmacodynamic changes (at the molecular level) which are associated with the activity of sunitinib and sorafenib in our sensitive esophageal HuPrime models. Tumor tissues from sensitive esophageal HuPrime models treated with single dose of the respective drugs (and a vehicle control) have been collected at time-points 4, 8, 16, and 24 hour. Results: We have successfully applied immunohistochemistry (IHC) assays on many molecules covering most pathways including proliferation, apoptotic, necrotic, and cell cycle regulation, G2M phase arrest, DNA damage response, etc. Additional markers including angiogenesis can also be included for certain therapeutic compounds. These tissues have been analyzed with our platform and we have uncovered key molecular events which correlate with the efficacy and potency of the drugs. Conclusions: The PD biomarkers validated in this approach have potential for clinical application and patient stratification. [Table: see text]

Pegylated Recombinant Human Arginase, Rharg-Peg5,000MW, Targets Cell Cycle Machinery in Multiple Myeloma Cells.

Arginase has been shown to inhibit growth of human hepatocellular carcinoma by depletion of arginine. We have studied the effects of the pegylated human recombinant arginase (BCT-100, rhArg-peg5,000MW) on RPMI8226 cells, a multiple myeloma cell line. This study showed that three day exposure of the myeloma cells to pegylated rhArg at a concentration of 0.08 IU/ml and 0.48 IU/ml resulted in growth suppression of 10% and 70% respectively, as compared to untreated control. Cell cycle analysis revealed significant decreases in the proportion of cells in both S- and G2M-phase and a concomitant increase of cells in G1-phase in a time- and concentration- dependent manner. We further studied the mechanisms of cell cycle arrest induced by the pegylated rhArg. The pegylated rhArg inhibited both cyclin-dependent kinases CDK2 and CDK4, enhanced the expression of the CDK inhibitor p21, and reduced the expression of cyclinD1, D2, and E. The level of phosphorylated Rb protein was also found to be significantly decreased. The regulators of cell cycle have thus been revealed as targets of pegylated rhArg for myeloma growth arrest. The pegylated rhArg may serve as a novel antitumor agent for multiple myeloma.

FLT3-ITD-TKD dual mutants associated with AML confer resistance to FLT3 PTK inhibitors and cytotoxic agents by overexpression of Bcl-x(L)

FLT3 (fms-like tyrosine kinase 3) is constitutively activated in about 30% of patients with acute myeloid leukemia (AML) and represents a disease-specific molecular marker. Although FLT3-LM (length mutation) and TKD (tyrosine kinase domain) mutations have been considered to be mutually exclusive, 1% to 2% of patients carry both mutations. However, the functional and clinical significance of this observation is unclear. We demonstrate that FLT3-ITD-TKD dual mutants induce drug resistance toward PTK inhibitors and cytotoxic agents in in vitro model systems. As molecular mechanisms of resistance, we found that FLT3-ITD-TKD mutants cause hyperactivation of STAT5 (signal transducer and activator of transcription-5), leading to upregulation of Bcl-x(L) and RAD51 and arrest in the G2M phase of the cell cycle. Overexpression of Bcl-x(L) was identified as the critical mediator of drug resistance and recapitulates the PTK inhibitor and daunorubicin-resistant phenotype in FLT3-ITD cells. The combination of rapamycin, a selective mTOR inhibitor, and FLT3 PTK inhibitors restored the drug sensitivity in FLT3 dual mutant–expressing cells. Our data provide the molecular basis for understanding clinical FLT3 PTK inhibitor resistance and point to therapeutical strategies to overcome drug resistance in patients with AML.

Growth Effects of Some Platinum(II) Complexes with Sulfur-Containing Carrier Ligands on MCF7 Human Breast Cancer Cell Line upon Simultaneous Administration with Taxol

The platinum (II)complexes, cis-[PtCl2(CH3SCH2CH2SCH3)] (Pt1), cis-[PtCl2(dmso)2] (dmso is dimethylsulfoxide; Pt2) and cis-[PtCl2(NH3)2] (cisplatin), and taxol (T) have been tested at different equimolar concentrations. Cells were exposed to complexes for 2 h and left to recover in fresh medium for 24, 48 or 72 h. Growth inhibition was measured by tetrazolium WST1 assay Analyses of the cell cycle, and apoptosis were performed by flow cytometry, at the same exposure times. The IC50 value of each platinum(II) complex as well as combination index (CI; platinum(II) complex + taxol) for various cytotoxicity levels were determined by median effects analysis.MCF7 cells were found to be sensitive to both Pt1 and Pt2 complexe These cisplatin analogues influenced the cell growth more effectively as compared to cisplatin. Cytotoxic effect was concentration and time-dependent. Profound growth inhibitory effect was observed for Pt1 complex, across all its concentrations at all recovery periods. A plateau effect was achieved three days after treatment at Pt1 concentrations ≤ 1 μM. Pt2, however, decreased MCF7 cells survival only for the first 24 h ranging between 50-55%. Pt2 cytotoxicity sharply decreased thereafter, approaching 2 h - treatment cytotoxicity level. The median IC50 values for Pt1 and Pt2 were similar (0.337 and 0.3051 μM, respectively) but only for the first 24 h. The IC50 values for Pt1 strongly depend on the recovery period. On simultaneos exposure of cells to taxol and platinum(II) complexes no consistent effect was found. The Cls for combinations of taxol with Pt1 or Pt2 revealed cytotoxic effects that were in most Cases synergistic (Pt1) or less than addtiive (Pt2). Flow cytometry analysis has shown that each platinum(II) complex induced apoptosis in MCF7 cells. The level of apoptosis correlated with cytotoxicity level for the range concentrations. Both cisplatin analogues, at IC50 concentrations, increased the number of MCF7 cells in G0G1 phase of cell cycle. Pt2-treated cells remained arrested in G0G1 phase up to 72 h after treatment. Combination of Pt2 and taxol caused further arrest of cells in G0G1 phase (24 h) in parallel with strong decrement of G2M phase cells.