Antitumor effects of flavopiridol on human uterine leiomyoma in vitro and in a xenograft model

Therapeutic Potential of the Cyclin-Dependent Kinase Inhibitor Flavopiridol on c-Myc Overexpressing Esophageal Cancer

Tumors with elevated c-Myc expression often exhibit a highly aggressive phenotype, and c-Myc amplification has been shown to be frequent in esophageal cancer. Emerging data suggests that synthetic lethal interactions between c-Myc pathway activation and small molecules inhibition involved in cell cycle signaling can be therapeutically exploited to preferentially kill tumor cells. We therefore investigated whether exploiting elevated c-Myc expression is effective in treating esophageal cancer with the CDK inhibitor flavopiridol. We found frequent overexpression of c-Myc in human esophageal cancer cell lines and tissues. c-Myc overexpression correlated with accelerated esophageal cancer subcutaneous xenograft tumor growth. Esophageal cancer cells with elevated c-Myc expression were found preferentially more sensitive to induction of apoptosis by the CDK inhibition flavopiridol compared to esophageal cancer cells with lower c-Myc expression. In addition, we observed that flavopiridol alone or in combination with the chemotherapeutic agent nanoparticle albumin-bound paclitaxel (NPT) or in combinations with the targeted agent BMS-754807 significantly inhibited esophageal cancer cell proliferation and subcutaneous xenograft tumor growth while significantly enhancing overall mice survival. These results indicate that aggressive esophageal cancer cells with elevated c-Myc expression are sensitive to the CDK inhibitor flavopiridol, and that flavopiridol alone or in combination can be a potential therapy for c-Myc overexpressing esophageal cancer.

The survivin molecule as a double-edged sword in cellular physiologic and pathologic conditions and its role as a potential biomarker and therapeutic target in cancer

Survivin is a member of the family of apoptosis inhibitory proteins with increased expression level in most cancerous tissues. Evidence shows that survivin plays regulatory roles in proliferation or survival of normal adult cells, principally vascular endothelial cells, T lymphocytes, primitive hematopoietic cells, and polymorphonuclear neutrophils. Survivin antiapoptotic role is, directly and indirectly, related to caspase proteins and shows its role in cell division through the chromosomal passenger complex. Survivin contains many genetic polymorphisms that the role of some variations has been proven in several cancers. The -31G/C polymorphism is one of the most important survivin mutations which is located in the promoter region on a CDE/CHR motif. This polymorphism can upregulate the survivin messenger RNA. In addition, its allele C can increase the risk of cancers in 1.27-fold than allele G. Considering the fundamental role of survivin in different cancers, this protein could be considered as a new therapeutic target in cancer treatment. For this purpose, various strategies have been designed including the prevention of survivin expression through inhibition of mRNA translation using antagonistic molecules, inhibition of survivin gene function through small inhibitory molecules, gene therapy, and immunotherapy. In this study, we describe the structure, played roles in physiological and pathological states and genetic polymorphisms of survivin. Finally, the role of survivin as a potential target in cancer therapy given challenges ahead has been discussed.

MiR-150-5p May Contribute to Pathogenesis of Human Leiomyoma via Regulation of the Akt/p27Kip1 Pathway In Vitro

Uterine leiomyoma is found in ~50–80% of women of a reproductive age and is the most common reason for hysterectomy. Recently, posttranscriptional gene silencing by microRNAs (miRs) has been reported as a mechanism for regulating gene expression stability in the pathogenesis of uterine leiomyomas. In this study, miR microarray analysis of leiomyomas and paired myometrial tissue revealed numerous aberrantly expressed miRs, including miR-150. In functional assays, transfection with miR-150 mimic resulted in decreased migration and fibrosis, implying an inhibition of leiomyoma growth. To identify the target genes of miR-150 in leiomyoma, gene set analysis and network analysis were performed. To overcome the limitations of in silico analysis, changes in expression levels of hallmark genes in leiomyoma after transfection with a miR-150 mimic were also evaluated using qRT-PCR. As a result, the Akt/p27^Kip1 pathway was presumed to be one of the target pathways of miR-150. After transfecting cultured leiomyoma cells with the miR-150 mimic, expression levels of its target gene Akt decreased, whereas those of p27^Kip1 increased significantly. Our results suggest that miR-150 affects the cell cycle regulation in uterine leiomyoma through the Akt/p27^Kip1 pathway.

G2/M inhibitors as pharmacotherapeutic opportunities for glioblastoma: the old, the new, and the future

Glioblastoma (GBM) is one of the deadliest tumors and has a median survival of 3 months if left untreated. Despite advances in rationally targeted pharmacological approaches, the clinical care of GBM remains palliative in intent. Since the majority of altered signaling cascades involved in cancer establishment and progression eventually affect cell cycle progression, an alternative approach for cancer therapy is to develop innovative compounds that block the activity of crucial molecules needed by tumor cells to complete cell division. In this context, we review promising ongoing and future strategies for GBM therapeutics aimed towards G2/M inhibition such as anti-microtubule agents and targeted therapy against G2/M regulators like cyclin-dependent kinases, Aurora inhibitors, PLK1, BUB, 1, and BUBR1, and survivin. Moreover, we also include investigational agents in the preclinical and early clinical settings. Although several drugs were shown to be gliotoxic, most of them have not yet entered therapeutic trials. The use of either single exposure or a combination with novel compounds may lead to treatment alternatives for GBM patients in the near future.

Effect of 2-methoxyestradiol on SK-LMS-1 uterine leiomyosarcoma cells

An endogenous metabolite of 17β-estradiol, 2-methoxyestradiol (2-ME), has affinity for estrogen receptors. This compound was reported to be a promising antitumor drug due to its anti-proliferative effects on a wide range of tumor cell types. Numerous previous studies have been performed to evaluate the cytotoxic effects of 2-ME on tumor cell lines in following the induction of G₂/M cell cycle arrest and subsequent apoptosis. Uterine leiomyosarcoma (ULMS) is a relatively rare malignant smooth muscle cell tumor that develops in the uterus muscle layer. The aim of the present study was to examine the in vitro anti-proliferative effects of 2-ME on SK-LMS-1 human leiomyosarcoma cells. An MTT assay, terminal deoxynucleotidyltransferase-mediated dUTP nick-end labeling assay, immunocytochemistry and western blotting were performed. A high concentration (10⁻⁵ M) of 2-ME was identified to have an anti-proliferative effect on SK-LMS-1 cells. Additionally, expression of the apoptosis markers was upregulated in the presence of 10⁻⁵ M 2-ME, according to western blot analysis. Furthermore, the expression level of an autophagic marker, light chain 3, was increased by 2-ME treatment in a dose-dependent manner. This was associated with cell death induced by the upregulation of phosphorylated extracellular-signal-regulated kinase 1/2 signaling pathway. The results of the present study demonstrated that 2-ME, which is used as a therapeutic agent for treating solid tumors, exhibits apoptotic and anti-proliferative effects depending on the dose. Therefore, 2-ME may be a potential therapeutic reagent for human ULMS, but the appropriate dose of this compound should be carefully selected.

Alvocidib (flavopiridol) for the treatment of chronic lymphocytic leukemia

INTRODUCTION

Alvocidib, which has orphan drug designation in chronic lymphocytic leukemia (CLL) from the FDA and the EMA, is a plant-derived semisynthetic flavone that acts as a cyclin-dependent kinase inhibitor. It induces apoptosis in CLL cells in vitro and was introduced into clinical trials in CLL as an intravenous infusion in 1997, which proved disappointing. Since the drug avidly binds to plasma proteins, higher serum concentrations were required for clinical antileukemia activity than those suggested by in vitro studies. Subsequent studies utilizing bolus plus infusional doses revealed significant activity against CLL, even in patients with unfavorable characteristics. However, significant toxicity including high rates of major tumor lysis syndrome, cytokine release syndrome and secretory diarrhea were also observed.

AREAS COVERED

The chemistry, pharmacodynamics, pharmacokinetics and metabolism of alvocidib are briefly discussed and phase I-II studies in CLL are discussed in detail. To date, no phase III studies in CLL have been reported.

EXPERT OPINION

A number of much less toxic drugs with similar efficacy against CLL both with and without unfavorable cytogenetics have come to market. Furthermore, enthusiasm for the development of alvocidib as a single agent for the treatment of CLL has waned, primarily due to its toxicity.

Recent Advances on Small-Molecule Survivin Inhibitors

Survivin, a member of the inhibitor of apoptosisproteins family, is highly expressed in most human neoplasms, but its expression is very low or undetectable in terminally differentiated normal tissues. Survivin has been shown to inhibit cancer cell apoptosis and promote cell proliferation. The overexpression of survivin closely correlates with tumor progression and drug resistance. Because of its key role in tumor formation and maintenance, survivin is considered as an ideal target for anticancer treatment. However, the development of small-molecule survivin inhibitors has been challenging due to the requirement to disrupt the protein-protein interactions. Currently only a limited number of survivin inhibitors have been developed in recent years, and most of these inhibitors reduce survivin levels by interacting with other biomolecules instead of directly interacting with survivin protein. Despite these challenges, developing potent and selective small-molecule survivin inhibitors will be important in both basic science to better understand survivin biology and in translational research to develop potentially more effective, broad-spectrum anticancer agents. In this review, the functions of survivin and its role in cancer are summarized. Recent developments, challenges, and future direction of small-molecule survivin inhibitors are also discussed in detail.