Ahmed M. Al-Abd

P-glycoprotein inhibitors of natural origin as potential tumor chemo-sensitizers: A review

Graphical abstract

Pharmacokinetics of doxorubicin after intratumoral injection using a thermosensitive hydrogel in tumor-bearing mice

A novel, thermosensitive hydrogel, poly(organophosphazene), is an injectable drug delivery system that transforms from sol to gel at body temperature. Doxorubicin (DOX) is a cytotoxic drug used for the treatment of several solid tumors. Due to its acute cardiac toxicity, DOX is a good candidate for local chemo-drug delivery system. In this study, we evaluated the pharmacokinetics of DOX (30 mg/kg) when given as an intratumoral injection using poly(organophosphazene) hydrogel in mice with human gastric tumor xenografts. DOX was formulated at 0.6% into a 10% hydrogel, and 40% and 90% of the dose was released in a sustained manner over 5 weeks in vitro and in vivo, respectively. The hydrogel mass was well retained over 7 weeks, and T(1/2beta, tumor) was 1.8-fold longer than that of the solution, but the 2.2-fold lower C(max, tumor), produced a similar AUC(tumor) and antitumor effect. However, solution caused a 2-fold higher systemic exposure (AUC(plasma)), which resulted in significant mortality due to acute cardiac toxicity. These data indicate that hydrogel formulation may have similar efficacy but lower systemic exposure than aqueous solution. In conclusion, poly(organophosphazene) showed adequate characteristics for local intratumoral delivery of DOX, including dose capacity, local retention, and minimal systemic spill-over. The safety and biocompatibility of poly(organophosphazene) should be further evaluated and its application should be extended to other anticancer agents.

Resveratrol enhances the cytotoxic profile of docetaxel and doxorubicin in solid tumour cell lines in vitro

Objectives:  Resveratrol, with its robust antioxidant activity, has frequently been suggested as potentially having activity in cancer prevention and some recent reports have indicated that it has cancer treatment potential for several types of neoplasia. It has been found to block p‐glycoprotein and to protect against several chemotherapeutic agents’ side effects. In this study, we assessed interactive characteristics of resveratrol with docetaxel and doxorubicin and further investigated molecular bases of this interaction in cells of three different solid tumour lines (MCF‐7, HeLa and HepG2).

Novel application of multicellular layers culture for in situ evaluation of cytotoxicity and penetration of paclitaxel

Limited drug penetration into tumor tissue is one of the major factors causing clinical drug resistance in human solid tumors. The multicellular layers (MCL) of human cancer cells have been successfully used to study tissue pharmacokinetics of anticancer drugs. The purpose of this study was to develop a direct and simple method to evaluate vitality changes in situ within MCL using calcein‐AM. Human colorectal (DLD‐1, HT‐29) and bladder (HT‐1376, J‐82) cancer cells were grown in Transwell inserts to form MCL and subjected to paclitaxel exposure. The drug distribution was evaluated using paclitaxel‐rhodamine. Photonic attenuation and limited penetration of calcein‐AM prevented cellular vitality evaluation on optical sections under confocal microscopy in DLD‐1 MCL. However, direct measurement of the fluorescence intensity on frozen sections of MCL allowed successful vitality assessment in more than 80% depth for HT‐29 and J‐82 MCL and in the upper 40% depth for DLD‐1 and HT‐1376 MCL. The penetration of paclitaxel‐rhodamine was greater in HT‐29 than DLD‐1 and its distribution pattern was correlated to the spatial profile of vitality deterioration in both MCL, suggesting that tissue penetration may be an important determinant of drug effect in tumors. In conclusion, a novel method for vitality evaluation in situ within MCL was developed using calcein‐AM. This method may provide clinically relevant data regarding the spatial pharmacodynamics of anticancer agents within avascular regions of solid tumors. (Cancer Sci 2008; 99: 423–431)

Caffeic acid phenethyl ester synergistically enhances docetaxel and paclitaxel cytotoxicity in prostate cancer cells

Evidence is growing for the beneficial role of selective estrogen receptor modulators (SERM) in prostate diseases. Caffeic acid phenethyl ester (CAPE) is a promising component of propolis that possesses SERM activity. This study aimed at investigating the modulatory impact of CAPE on docetaxel (DOC) and paclitaxel (PTX) cytotoxicity in prostate cancer cells and exploring the possible underlying mechanisms for this chemomodulation. CAPE significantly increased DOC and PTX potency in PC‐3, DU‐145 and LNCaP prostate cancer cells. Combination index calculations showed synergistic interaction of CAPE/DOC and CAPE/PTX cotreatments in all the tested cell lines. Subsequent mechanistic studies in PC‐3 cells indicated that cyclin D1 and c‐myc were significantly reduced in the combined treatment groups with concurrent increase in p27kip. DNA‐ploidy analysis indicated a significant increase in the percentage of cells in pre‐G1 in CAPE/DOC and CAPE/PTX cotreatments. Decreased Bcl‐2/Bax ratio together with increased caspase‐3 activity and protein abundance were observed in the same groups. Estrogen receptor‐β (ER‐β) and its downstream tumor suppressor forkhead box O1 levels were significantly elevated in CAPE and combination groups compared to DOC or PTX‐alone. ER‐α and insulin‐like growth factor‐1 receptor protein abundance were reduced in the same groups. CAPE significantly reduced AKT, ERK and ER‐α (Ser‐167) phosphorylation in PC‐3 cells. CAPE‐induced inhibition of AKT phosphorylation was more prominent (1.7‐folds higher) in cells expressing ER‐α such as PC‐3 compared to LNCaP. In conclusion, CAPE enhances the antiproliferative and cytotoxic effects of DOC and PTX in prostate cancer cells. This can be, at least partly, attributed to CAPE augmentation of DOC and PTX proapoptotic effects in addition to CAPE‐induced alterations in ER‐α and ER‐β abundance.

Penetration and efficacy of VEGF siRNA using polyelectrolyte complex micelles in a human solid tumor model in-vitro

A polyelectrolyte complex(PEC) micelle-based siRNA delivery system has been developed for vascular endothelial growth factor (VEGF), and its antitumor efficacy has been demonstrated using in-vivo animal models. Penetration and distribution through the avascular regions of human solid tumors after extravasation are important issues for antitumor efficacy, especially for macromolecules such as VEGF siRNA PEC micelles. Using an in-vitro solid tumor model, multicellular layers(MCL) culture of human colorectal cancer cells, we evaluated the penetration kinetics and efficacy of VEGF siRNA PEC micelles(PEC-siRNA) in comparison to unmodified siRNA(N-siRNA). The PEC-siRNA showed full penetration (15-17 layers of cells) with a unique punctuated distribution pattern at 48 h following initial accumulation in the top layers and a significant suppression of mRNA and protein expression in a dose-dependent manner after 72 h exposure. Although the initial penetration of N-siRNA was faster than that of PEC-siRNA, N-siRNA showed complete loss of activity due to its instability within 24 h. Our data support the idea that PEC micelle formulation may provide stable penetration tool through the multilayers of cancer cells and ensure the gene silencing effect of VEGF. This study also demonstrated that MCL could serve as a useful in-vitro model to evaluate the dose- and time-dependent profiles of penetration and efficacy of macromolecular delivery systems in human solid tumor avascular regions.

Pharmacokinetic strategies to improve drug penetration and entrapment within solid tumors.

Despite the discovery of a large number of anticancer agents, cancer still remains among the leading causes of death since the middle of the twentieth century. Solid tumors possess a high degree of genetic instability and emergence of treatment resistance. Tumor resistance has emerged for almost all approved anticancer drugs and will most probably emerge for newly discovered anticancer agents as well. The use of pharmacokinetic approaches to increase anticancer drug concentrations within the solid tumor compartment and prolong its entrapment might diminish the possibility of resistance emergence at the molecular pharmacodynamic level and might even reverse tumor resistance. Several novel treatment modalities such as metronomic therapy, angiogenesis inhibitors, vascular disrupting agents and tumor priming have been introduced to improve solid tumor treatment outcomes. In the current review we will discuss the pharmacokinetic aspect of these treatment modalities in addition to other older treatment modalities, such as extracellular matrix dissolving agents, extracellular matrix synthesis inhibitors, chemoembolization and cellular efflux pump inhibition. Many of these strategies showed variable degrees of success/failure; however, reallocating these modalities based on their influence on the intratumoral pharmacokinetics might improve their understanding and treatment outcomes.

Tissue distribution and efficacy of gold nanorods coupled with laser induced photoplasmonic therapy in ehrlich carcinoma solid tumor model.

Gold nanorods (GNR) within tumor microregions are characterized by their ability to absorb near IR light and emit heat in what is called photoplasmonic effect. Yet, the efficacy of nanoparticles is limited due to intratumoral tissue distribution reasons. In addition, distribution of GNRs to normal tissue might result in non specific toxicity. In the current study, we are assessing the intratumoral and tissue distribution of PEGylated GNRs on the top of its antitumor characteristics when given intravenously or intratumoral to solid tumor bearing mice and coupled with laser photoplasmonic sessions. PEGylated GNRs with a longitudinal size of less than 100 nm were prepared with aspect ratio of 4.6 showing strong surface plasmon absorption at wavelength 800 nm. Pharmacokinetics of GNR after single I.V. administration (0.1 mg/kg) showed very short systemic circulating time (less than 3 h). On the other hand, tissue distribution of I.V. GNR (0.1 mg/kg) to normal animals showed preferential deposition in spleen tissue. Repeated administration of I.V. GNR resulted in preferential accumulation in both liver and spleen tissues. In addition, I.V. administration of GNR to Ehrlich carcinoma tumor bearing mice resulted in similar tissue distribution; tumor accumulation and anti-tumor effect compared to intratumoral administration. In conclusion, the concentration of GNR achieved within tumors microregions after I.V. administration was comparable to I.T. administration and sufficient to elicit tumoral growth arrest when coupled with laser-aided photoplasmonic treatment.

A simple HPLC method for doxorubicin in plasma and tissues of nude mice.

Doxorubicin is a cytotoxic anthracycline that has been used for the treatment of several malignancies. Several HPLC methods have been reported for the quantification of doxorubicin in biological samples. Tissue matrix effect and sample size requirements, however, have been remaining issues for simple and easy-to-adapt analytical methods in small animal experiments. The present study established a simple HPLC method for doxorubicin in plasma and tissues (tumor, heart, spleen, liver, gastrointestinal tract, brain, lung, and kidney) of nude mice. Our method required a small sample volume (100 μL plasma and 10 mg tissue), which made it possible to use each blank tissue for calibration curves. The limit of quantification was 25 ng/mL in plasma and 0.1 to 0.4 μg/mg in other tissues with recovery rates ranging from 52.4 to 95.2%. The linearity, accuracy and precision in all tissues, except gastrointestinal tract (GIT), were found to be acceptable in the range of 25–2000 ng/mL plasma and 0.1–4 ng/mg tissue. This method was used successfully to determine the drug concentration in plasma and tissues of human tumor xenograft-bearing nude mice given intratumoral doxorubicin in a polymeric drug delivery system designed for sustained release. In conclusion, the present method may be useful as a simple and easy-to-adapt, yet, sensitive analytical method of doxorubicin for plasma and tissue pharmacokinetic studies in small animals such as nude mice.

Eichhornia crassipes (Mart) solms: From water parasite to potential medicinal remedy

Water hyacinth, Eichhornia crassipes (Mart) Solms, originating in the amazonian basin, is a warm water aquatic plant. Water hyacinth is considered one of the most productive plants on earth and, accordingly, is considered one of the top 10 world’s worst weeds. Water hyacinth spread to other tropical and subtropical regions by humans. It invaded about 62 countries in Africa, Asia and North America, and propagated extremely serious ecological, economical and social problems in the region between 40 degrees north and 45 degrees south. The dense weed of water hyacinth forms dense monocultures that can threaten local native species diversity and change the physical and chemical aquatic environment, thus altering ecosystem structure and function by disrupting food chains and nutrient cycling. We have separated and identified nine active fractions from water hyacinth and showed their promising therapeutic activities. Several compounds (alkaloid, phthalate derivatives, propanoid and phenyl derivatives) were identified in the extract of water hyacinth.