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).

MATERIALS AND METHODS AND RESULTS

  Resveratrol per se was found to have anti-cancer properties, but with relatively low potency in all tested cell lines (IC(50) ranged from 35.1 to 83.8 μM). Doxorubicin and docetaxel showed IC(50) ranging from 0.48 to 0.72 μM and from 25.9 to 77.8 nM, respectively. Resveratrol in combination with doxorubicin and docetaxel significantly increased potencies of both chemotherapeutic agents showing IC(50) ranging from 0.12 to 0.34 μM and from 7.2 to 53.02 nM, respectively. The combination index showed synergistic interaction between resveratrol and doxorubicin or docetaxel on MCF-7 cells, and additive interactions on HeLa and HepG2 cells. Real time PCR revealed that expression of Bax and Bcl-2 was simultaneously elevated on combination of resveratrol with doxorubicin or docetaxel in all tested cell lines, whereas p53 exhibited marginal elevation in MCF-7 and HepG2 cells. In addition, p-glycoprotein efflux activity was significantly inhibited, with subsequent accumulation of p-glycoprotein substrate in intracellular compartments. Expression level of mdr1 gene was downregulated after resveratrol combined with doxorubicin or docetaxel in all tested cell lines.

CONCLUSION

  Resveratrol potentiates cytotoxic properties of both cancer drugs used in the study through increasing their intracellular level due to p-glycoprotein inhibition and downregulation of mdr1 gene.

Antitumor properties and modulation of antioxidant enzymes' activity by Aloe vera leaf active principles isolated via supercritical carbon dioxide extraction

The aim of this study was to evaluate the potential anticancer properties and modulatory effect of selected Aloe vera (A. vera) active principles on antioxidant enzyme activities. Thus, three anthraquinones (Namely: aloesin, aloe-emodin and barbaloin) were extracted from A. vera leaves by supercritical fluid extraction and subsequently purified by high performance liquid chromatography. Additionally, the N-terminal octapeptide derived from verectin, a biologically active 14 kDa glycoprotein present in A. vera, was also tested. In vivo, active principles exhibited significant prolongation of the life span of tumor-transplanted animals in the following order: barbaloin> octapeptide> aloesin > aloe-emodin. A. vera active principles exhibited significant inhibition on Ehrlich ascite carcinoma cell (EACC) number, when compared to positive control group, in the following order: barbaloin> aloe-emodin > octapeptide > aloesin. Moreover, in trypan blue cell viability assay, active principles showed a significant concentration-dependent cytotoxicity against acute myeloid leukemia (AML) and acute lymphocytes leukemia (ALL) cancerous cells. Furthermore, in MTT cell viability test, aloe-emodin was found to be active against two human colon cancer cell lines (i.e. DLD-1 and HT2), with IC(50) values of 8.94 and 10.78 microM, respectively. Treatments of human AML leukemic cells with active principles (100 microg ml(-1)) resulted in varying intensities of internucleosomal DNA fragmentation, hallmark of cells undergoing apoptosis, in the following order: aloe-emodin> aloesin> barbaloin> octapeptide. Intererstingly, treatment of EACC tumors with active principles resulted in a significant elevation activity of key antioxidant enzymes (SOD, GST, tGPx, and LDH). Our data suggest that the tested A. vera compounds may exert their chemo-preventive effect through modulating antioxidant and detoxification enzyme activity levels, as they are one of the indicators of tumorigenesis. These findings are discussed in the light of the potential of A. vera plant extracts for developing efficient, specific and non-toxic anticancer drugs that are affordable for developing countries.

Multigeneic QTL: the laccase encoded within the soybean Rfs2/rhg1 locus inferred to underlie part of the dual resistance to cyst nematode and sudden death syndrome

Multigeneic QTL present significant problems to analysis. Resistance to soybean (Glycine max (L) Merr.) sudden death syndrome (SDS) caused by Fusarium virguliforme was partly underlain by QRfs2 that was clustered with, or pleiotropic to, the multigeneic rhg1 locus providing resistance to soybean cyst nematode (SCN; Heterodera glycines). A group of five genes were found between the two markers that delimited the Rfs2/rhg1 locus. One of the five genes was predicted to encode an unusual diphenol oxidase (laccase; EC 1.10.3.2). The aim of this study was to characterize this member of the soybean laccase gene-family and explore its involvement in SDS resistance. A genomic clone and a full length cDNA was isolated from resistant cultivar 'Forrest' that were different among susceptible cultivars 'Asgrow 3244' and 'Williams 82' at four residues R/H168, I/M271, R/H330, E/K470. Additional differences were found in six of the seven introns and the promoter region. Transcript abundance (TA) among genotypes that varied for resistance to SDS or SCN did not differ significantly. Therefore the protein activity was inferred to underlie resistance. Protein expressed in yeast pYES2/NTB had weak enzyme activity with common substrates but good activity with root phenolics. The Forrest isoform may underlie both QRfs2 and rhg1.

Locus interactions underlie seed yield in soybeans resistant to Heterodera glycines

In soybean (Glycine max L. Merr.) combining resistance to cyst nematode (SCN; Heterodera glycines I.) with high seed yield remains problematic. Molecular markers linked to quantitative trait loci (QTL) have not provided a solution. Sets of markers describing a collection of favorable alleles (linkats) may assist plant breeders seeking to combine both traits. The objective of this analysis was to identify linkats in genomic regions underlying seed yield and root SCN resistance QTL. Used were groups of cultivars selected from a single recombinant inbred (RIL) population derived from 'Essex' by 'Forrest' (ExF). The yield was measured at four locations. SCN resistance was determined in greenhouse assays. The mean seed yield was used to define 3 groups (each n = 30), high, medium and low. SCN resistance formed 2 groups (SCN resistant (n = 21) and SCN susceptible (n = 69)). Microsatellite markers (213) alleles were compared with seed yield and root SCN (Hetrodera glycines) resistance using mean analysis. The number, size and position of potential linkats were determined. Loci, genomic regions and linkats associated with seed yield were identified on linkage group (LG) K and with root resistance to SCN e on LG E, G, and D1b+W. A method to identify co-localized genomic regions is presented.