Diversity of RGD radiotracers in monitoring antiangiogenesis of flavopiridol and paclitaxel in ovarian cancer xenograft-bearing mice

The Pharmacological Implications of Flavopiridol: An Updated Overview

Flavopiridol is a flavone synthesized from the natural product rohitukine, which is derived from an Indian medicinal plant, namely Dysoxylum binectariferum Hiern. A deeper understanding of the biological mechanisms by which such molecules act may allow scientists to develop effective therapeutic strategies against a variety of life-threatening diseases, such as cancer, viruses, fungal infections, parasites, and neurodegenerative diseases. Mechanistic insight of flavopiridol reveals its potential for kinase inhibitory activity of CDKs (cyclin-dependent kinases) and other kinases, leading to the inhibition of various processes, including cell cycle progression, apoptosis, tumor proliferation, angiogenesis, tumor metastasis, and the inflammation process. The synthetic derivatives of flavopiridol have overcome a few demerits of its parent compound. Moreover, these derivatives have much improved CDK-inhibitory activity and therapeutic abilities for treating severe human diseases. It appears that flavopiridol has potential as a candidate for the formulation of an integrated strategy to combat and alleviate human diseases. This review article aims to unravel the potential therapeutic effectiveness of flavopiridol and its possible mechanism of action.

Recent Research Progress of RGD Peptide–Modified Nanodrug Delivery Systems in Tumor Therapy

There have been great advancements in targeted nanodrug delivery systems for tumor therapy. Liposomes, polymeric nanoparticles, and inorganic nanoparticles are commonly employed as nanocarriers for drug delivery, and it has been found that arginine glycine aspartic acid (RGD) peptides and their derivatives can be used as ligands of integrin receptors to enhance the direct targeting ability. In this paper, we review the recent applications of RGD-modified liposomes, polymeric nanoparticles, and inorganic nanocarriers in cancer diagnosis and treatment, discuss the current challenges and prospects, and examine the progress made by the latest research on RGD peptide–modified nano delivery systems in cancer therapy. In recent years, RGD peptide–modified nanodrug delivery systems have been proven to have great potential in tumor therapy. Finally, we provide an overview of the current limitations and future directions of RGD peptide–modified nano-drug delivery systems for cancer therapy. This review aims to elucidate the contribution of RGD peptide–modified nanodrug delivery systems in the field of tumor therapy.

Gemcitabine-loaded RGD modified liposome for ovarian cancer: preparation, characterization and pharmacodynamic studies

Background

Ovarian cancer is the third leading cause of death among gynecological cancers in women in China. Chemotherapy is an important method for comprehensive treatment of ovarian cancer, but the curative effect is poor.

Purpose

In this study, gemcitabine (GEM) -loaded RGD modified liposomes (LPs) were developed by the emulsification-solvent evaporation method and evaluated for their antitumor activity in vitro and in vivo.

Methods

The physicochemical properties of LPs such as particle size, zeta potential and in vitro drug release were investigated. We also demonstrated the effect of RGD-GEM-PEG LPs in ovarian cancer.

Results

RGD-PEG3500-DSPE GEM LPs had a uniform spherical morphology. The mean particle size and polydispersity index were determined to be 106.7 nm and 0.13 respectively. The ER% and DL% of the formulation were 79.6±3.1% and 6.1±1.4% respectively. Compared with the free drug, RGD modified GEM LPs had sustained-release properties in vitro. In vivo, compared with the DiD-RGD-PEG3500-DSPE GEM LPs group, free DiD-GEM and DiD-GEM LPs had no obvious fluorescence intensity in tumor of mice at all times, indicating that ordinary liposomes and drugs had no tumor targeting function. RGD-PEG3500-DSPE GEM LPs showed a superior antiproliferative effect on SKOV3 cells and had a better antitumor effect in vivo than non-modified LPs.

Conclusion

These results indicated that RGD-PEG3500-DSPE GEM LPs were a promising candidate for antitumor drug delivery.

An optimized LC-MS/MS method for determination of HYNIC-3PRGD2, a new promising imaging agent for tumor targeting, in rat plasma and its application

HYNIC-3PRGD₂ is used to prepare a new ^99mTc-radiolabeled tracer. HYNIC-3PRGD₂, which has a high binding affinity for the integrin α_vβ₃ due to its special structure, has become a promising tumor imaging agent for diagnosis and monitor of the clinical response to therapeutic effects of anti-tumor agents. Here, we developed and validated a method for determination of HYNIC-3PRGD₂ concentration in rat plasma using ultra-high performance liquid chromatography-tandem mass spectrometry system. Following sample extraction by methanol precipitation, satisfactory separation through chromatography was achieved on an hydrophilic reverse-phase C₁₈ column AQ (2.1 mm × 100 mm, 2.7 μm) at a flow rate of 0.2 mL·min^-1 with an gradient elution using mobile phase consisting of ultrapure water and acetonitrile fortified with 0.1% formic acid respectively. The calibration curve was developed over a linear range of 3.125-100 ng·mL^-1 with the lower limit of quantification of 3.125 ng·mL^-1. The HYNIC-3PRGD₂ and its internal standard c(RGDfK)(RK5) were detected and quantified with the multiple reaction monitoring (MRM) mode on a triple-quadrupole tandem mass spectrometer. This method was successfully validated and applied for pharmacokinetic evaluation of HYNIC-3PRGD₂ during pre-clinical experiments.

Combined inhibition of CDK and HDAC as a promising therapeutic strategy for both cutaneous and uveal metastatic melanoma

Very little to no improvement in overall survival has been seen in patients with advanced non-resectable cutaneous melanoma or metastatic uveal melanoma in decades, highlighting the need for novel therapeutic options. In this study we investigated as a potential novel therapeutic intervention for both cutaneous and uveal melanoma patients a combination of the broad spectrum HDAC inhibitor quisinostat and pan-CDK inhibitor flavopiridol. Both drugs are currently in clinical trials reducing time from bench to bedside. Combining quisinostat and flavopiridol shows a synergistic reduction in cell viability of all melanoma cell lines tested, irrespective of their driver mutations. This synergism was also observed in BRAF^V600E mutant melanoma that had acquired resistance to BRAF inhibition. Mechanistically, loss of cell viability was, at least partly, due to induction of apoptotic cell death. The combination was also effectively inducing tumor regression in a preclinical setting, namely a patient-derived tumor xenograft (PDX) model of cutaneous melanoma, without increasing adverse effects. We propose that the quisinostat/flavopiridol combination is a promising therapeutic option for both cutaneous and uveal metastatic melanoma patients, independent of their mutational status or (acquired) resistance to BRAF inhibition.

MicroPET imaging of tumor angiogenesis and monitoring on antiangiogenic therapy with an (18)F labeled RGD-based probe in SKOV-3 xenograft-bearing mice

So far, there is no satisfactory imaging modality to monitor antiangiogenesis therapy of ovarian cancer noninvasively. The aim of this study was to evaluate the effectiveness and sensibility of an (18)F labeled Arg-Gly-Asp (RGD) peptide in imaging and monitoring antiangiogenic responds in SKOV-3 xenograft-bearing mice. (18)F-FB-NH-PEG4-E[PEG4-c(RGDfK)]2 (denoted as (18)F-RGD2) was synthesized and employed in this study. Mice bearing ovarian cancer SKOV-3 tumors were used for biodistribution and microPET imaging studies compared with (18)F-FDG imaging. Animals were treated with low-dose paclitaxel and the effect of paclitaxel therapy on (18)F-RGD2 accumulation was investigated. Microvascular density (MVD) of SKOV-3 tumors was detected to assess the reliability of (18)F-RGD2 in antiangiogenesis monitoring. Biodistribution studies for (18)F-RGD2 revealed favorable in vivo pharmacokinetic properties, with significant levels of receptor-specific tumor uptake determined via blocking studies. MicroPET imaging results demonstrated high contrast visualization of SKOV-3 tumors. And tumor to background ratio (T/NT) of (18)F-RGD2 uptake was significantly higher than that of (18)F-FDG. Studies on antiangiogenic therapy demonstrated percentage of injected dose per gram of tissue (%ID/g) tumor uptake of (18)F-RGD2 which was obviously decreased in the treatment group than the control group, especially at 60 min (by 31.31 ± 7.18 %, P = 0.009) and 120 min (by 38.92 ± 8.31 %, P < 0.001) after injection of (18)F-RGD2. MVD measurement of SKOV-3 tumors confirmed the finding of the biodistribution studies in monitoring antiangiogenesis therapy. (18)F-RGD2, with favorable biodistribution properties and specific affinity, is a promising tracer for tumor imaging and monitoring antiangiogenesis therapy in ovarian cancer SKOV-3 xenograft-bearing mice.