Roscovitine sensitizes leukemia and lymphoma cells to tumor necrosis factor-related apoptosis-inducing ligand-induced apoptosis

Peptide-Functionalized Nanoparticles-Encapsulated Cyclin-Dependent Kinases Inhibitor Seliciclib in Transferrin Receptor Overexpressed Cancer Cells

Seliciclib, a broad cyclin-dependent kinases (CDKs) inhibitor, exerts its potential role in cancer therapy. For taking advantage of overexpressive transferrin receptor (TfR) on most cancer cells, T7 peptide, a TfR targeting ligand, was selected as a targeting ligand to facilitate nanoparticles (NPs) internalization in cancer cells. In this study, poly(d,l-lactide-co-glycolide) (PLGA) was conjugated with maleimide poly(ethylene glycol) amine (Mal-PEG-NH₂) to form PLGA-PEG-maleimide copolymer. The synthesized copolymer was used to prepare NPs for encapsulation of seliciclib which was further decorated by T7 peptide. The result shows that the better cellular uptake was achieved by T7 peptide-modified NPs particularly in TfR-high expressed cancer cells in order of MDA-MB-231 breast cancer cells > SKOV-3 ovarian cancer cells > U87-MG glioma cells. Both SKOV-3 and U87-MG cells are more sensitive to encapsulated seliciclib in T7-decorated NPs than to free seliciclib, and that IC₅₀ values were lowered for encapsulated seliciclib.

Inhibition of Cyclin-dependent Kinase 2 Signaling Prevents Liver Ischemia and Reperfusion Injury

BACKGROUND

Liver ischemia and reperfusion injury (IRI) is a major complication of liver transplant, hepatectomy, and hemorrhagic shock. The cyclin-dependent kinase 2 (CDK2) acts as a pivotal regulator of cell cycle and proliferation.

METHODS

This study evaluated the modulation and therapeutic potential of CDK2 inhibition in a mouse model of partial liver warm IRI.

RESULTS

Liver IR-triggered intrinsic CDK2 expression, peaking by 0.5 hour of reperfusion and maintaining a high-level throughout 1 to 24 hours. Roscovitine, a specific CDK2 inhibitor, prevented liver IR-mediated damage with abolished serum alanine aminotransferase levels and reserved liver pathology. CDK2 inhibition-mediated liver protection was accompanied by decreased macrophage/neutrophil infiltration, diminished hepatocyte apoptosis, abolished toll like receptor 4 signaling and downstream gene inductions (C-X-C motif ligand-10, Tumor necrosis factor-α, interleukin-1β, and interleukin-6), yet augmented interleukin-10 expression. In vitro, CDK2 inhibition by Roscovitine suppressed macrophage TLR4 activation and further depressed downstream inflammatory signaling (myeloid differentiation factor 88, interferon regulatory transcription factor 3, p38, c-Jun N-terminal kinase, and extracellular-regulated kinase).

CONCLUSIONS

Our novel findings revealed the critical role of CDK2 in hepatic cytoprotection and homeostasis against liver IRI. As CDK2 inhibition regulated local immune response and prevented hepatocyte death, this study provided the evidence for new treatment approaches to combat IRI in liver transplant.

Roscovitine in cancer and other diseases

Roscovitine [CY-202, (R)-Roscovitine, Seliciclib] is a small molecule that inhibits cyclin-dependent kinases (CDKs) through direct competition at the ATP-binding site. It is a broad-range purine inhibitor, which inhibits CDK1, CDK2, CDK5 and CDK7, but is a poor inhibitor for CDK4 and CDK6. Roscovitine is widely used as a biological tool in cell cycle, cancer, apoptosis and neurobiology studies. Moreover, it is currently evaluated as a potential drug to treat cancers, neurodegenerative diseases, inflammation, viral infections, polycystic kidney disease and glomerulonephritis. This review focuses on the use of roscovitine in the disease model as well as clinical model research.

Selective CDK9 inhibition overcomes TRAIL resistance by concomitant suppression of cFlip and Mcl-1

Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) can induce apoptosis in many cancer cells without causing toxicity in vivo. However, to date, TRAIL-receptor agonists have only shown limited therapeutic benefit in clinical trials. This can, most likely, be attributed to the fact that 50% of all cancer cell lines and most primary human cancers are TRAIL resistant. Consequently, future TRAIL-based therapies will require the addition of sensitizing agents that remove crucial blocks in the TRAIL apoptosis pathway. Here, we identify PIK-75, a small molecule inhibitor of the p110α isoform of phosphoinositide-3 kinase (PI3K), as an exceptionally potent TRAIL apoptosis sensitizer. Surprisingly, PI3K inhibition was not responsible for this activity. A kinome-wide in vitro screen revealed that PIK-75 strongly inhibits a panel of 27 kinases in addition to p110α. Within this panel, we identified cyclin-dependent kinase 9 (CDK9) as responsible for TRAIL resistance of cancer cells. Combination of CDK9 inhibition with TRAIL effectively induced apoptosis even in highly TRAIL-resistant cancer cells. Mechanistically, CDK9 inhibition resulted in downregulation of cellular FLICE-like inhibitory protein (cFlip) and Mcl-1 at both the mRNA and protein levels. Concomitant cFlip and Mcl-1 downregulation was required and sufficient for TRAIL sensitization by CDK9 inhibition. When evaluating cancer selectivity of TRAIL combined with SNS-032, the most selective and clinically used inhibitor of CDK9, we found that a panel of mostly TRAIL-resistant non-small cell lung cancer cell lines was readily killed, even at low concentrations of TRAIL. Primary human hepatocytes did not succumb to the same treatment regime, defining a therapeutic window. Importantly, TRAIL in combination with SNS-032 eradicated established, orthotopic lung cancer xenografts in vivo. Based on the high potency of CDK9 inhibition as a cancer cell-selective TRAIL-sensitizing strategy, we envisage the development of new, highly effective cancer therapies.

Cyclin-dependent kinase inhibitor therapy for hematologic malignancies

INTRODUCTION

Cyclin-dependent kinases (CDKs) regulate cell cycle progression. Certain CDKs (e.g., CDK7, CDK9) also control cellular transcription. Consequently, CDKs represent attractive targets for anticancer drug development, as their aberrant expression is common in diverse malignancies, and CDK inhibition can trigger apoptosis. CDK inhibition may be particularly successful in hematologic malignancies, which are more sensitive to inhibition of cell cycling and apoptosis induction.

AREAS COVERED

A number of CDK inhibitors, ranging from pan-CDK inhibitors such as flavopiridol (alvocidib) to highly selective inhibitors of specific CDKs (e.g., CDK4/6), such as PD0332991, that are currently in various phases of development, are profiled in this review. Flavopiridol induces cell cycle arrest, and globally represses transcription via CDK9 inhibition. The latter may represent its major mechanism of action via down-regulation of multiple short-lived proteins. In early phase trials, flavopiridol has shown encouraging efficacy across a wide spectrum of hematologic malignancies. Early results with dinaciclib and PD0332991 also appear promising.

EXPERT OPINION

In general, the antitumor efficacy of CDK inhibitor monotherapy is modest, and rational combinations are being explored, including those involving other targeted agents. While selective CDK4/6 inhibition might be effective against certain malignancies, broad-spectrum CDK inhibition will likely be required for most cancers.

Resistance to TRAIL in mantle cell lymphoma cells is associated with the decreased expression of purine metabolism enzymes

Mantle cell lymphoma (MCL) is a rare aggressive type of B-cell non-Hodgkin's lymphoma. Response to chemotherapy tends to be short and virtually all patients sooner or later relapse. The prognosis of relapsed patients is extremely poor. The tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) is considered one of the novel experimental molecules with strong antitumor effects. TRAIL triggers extrinsic apoptotis in tumor cells by binding to TRAIL 'death receptors' on the cell surface. Recombinant TRAIL has shown promising pro-apoptotic effects in a variety of malignancies including lymphoma. However, as with other drugs, lymphoma cells can develop resistance to TRAIL. Therefore, the aim of this study was to identify the molecular mechanisms responsible for, and associated with TRAIL resistance in MCL cells. If identified, these features may be used as molecular targets for the effective elimination of TRAIL-resistant lymphoma cells. From an established TRAIL-sensitive mantle cell lymphoma cell line (HBL-2) we derived a TRAIL-resistant HBL-2/R subclone. By TRAIL receptor analysis and differential proteomic analysis of HBL-2 and HBL-2/R cells we revealed a marked downregulation of all TRAIL receptors and, among others, the decreased expression of 3 key enzymes of purine nucleotide metabolism, namely purine nucleoside phosphorylase, adenine phosphoribosyltransferase and inosine-5'-monophosphate dehydrogenase 2, in the resistant HBL-2/R cells. The downregulation of the 3 key enzymes of purine metabolism can have profound effects on nucleotide homeostasis in TRAIL-resistant lymphoma cells and can render such cells vulnerable to any further disruption of purine nucleotide metabolism. This pathway represents a 'weakness' of the TRAIL-resistant MCL cells and has potential as a therapeutic target for the selective elimination of such cells.