Inula Viscosa Extracts Induces Telomere Shortening and Apoptosis in Cancer Cells and Overcome Drug Resistance.

Telomerase is activated in human papillomavirus (HPV) positive cervical cancer and targeting telomeres offers a novel anticancer therapeutic strategy. In this study, the telomere targeting properties, the cytotoxic as well as the pro-apoptotic effects of hexane (IV-HE) and dichloromethane (IV-DF) fractions from Inula viscosa L. extracts were investigated on human cervical HeLa and SiHa cancer cells. Our data demonstrate that IV-HE and IV-DF extracts were able to inhibit cell growth in HeLa and SiHa cells in a dose-dependent manner and studied resistant cell lines exhibited a resistance factor less than 2 when treated with the extracts. IV-HE and IV-DF extracts were able to inhibit telomerase activity and to induce telomere shortening as shown by telomeric repeat amplification protocol and TTAGGG telomere length assay, respectively. The sensitivity of fibroblasts to the extracts was increased when telomerase was expressed. Finally, IV-HE and IV-DF were able to induce apoptosis as evidenced by an increase in annexin-V labeling and caspase-3 activity. This study provides the first evidence that the IV-HE and IV-DF extracts from Inula viscosa L. target telomeres induce apoptosis and overcome drug resistance in tumor cells. Future studies will focus on the identification of the molecules involved in the anticancer activity.

Medicarpin and millepurpan, two flavonoids isolated from Medicago sativa, induce apoptosis and overcome multidrug resistance in leukemia P388 cells.

BACKGROUND: High consumption of flavonoids has been associated with a decrease risk of cancer. Alfalfa (Medicago sativa) leaves have been widely used in traditional medicine and is currently used as a dietary supplement because of their high nutrient content. We previously reported the cytotoxic activity of alfalfa leaf extracts against several sensitive and multidrug resistant tumor cell lines. HYPOTHESIS/PURPOSE: We aimed to determine whether medicarpin and millepurpan, two isoflavonoids isolated from alfalfa leaves, may have pro-apoptotic effects against drug-sensitive (P388) and multidrug resistant P388 leukemia cells (P388/DOX). STUDY DESIGN/METHODS: Cells were incubated with medicarpin or millepurpan for the appropriate time. Cell viability was assessed by the MTT assay. DNA fragmentation was analyzed by agarose gel electrophoresis. Cell cycle analysis was realized by flow cytometry technics. Caspases 3 and 9 activities were measured using Promega caspACE assay kits. Proteins and genes expression were visualized respectively by western-blot using specific antibodies and RT-PCR assay. RESULTS: P-glycoprotein-expressing P388/DOX cells did not show resistance to medicarpin (IC50 ≈ 90 µM for P388 and P388/DOX cells) and millepurpan (IC50 = 54 µM and 69 µM for P388 and P388/DOX cells, respectively). Treatment with medicarpin or millepurpan triggered apoptosis in sensitive as well as multidrug resistant P388 cells. These effects were mediated through the mitochondrial pathway by modifying the balance pro/anti-apoptotic proteins. While 3 µM doxorubicin alone could not induce cell death in P388/DOX cells, concomitant treatment with doxorubicin and subtoxic concentration of medicarpin or millepurpan restored the pro-apoptotic cascade. Each compound increased sensitivity of P388/DOX cells to doxorubicin whereas they had no effect in sensitive P388 cells. Vinblastine cytotoxicity was also enhanced in P388/DOX cells (IC50 = 210 nM to 23 and 25 nM with medicarpin and millepurpan, respectively). This improved sensitivity was mediated by an increased uptake of doxorubicin in P388/DOX cells expressing P-gp. P-gp expression was not altered by exposure to medicarpin and millepurpan. CONCLUSION: These data indicate that medicarpin and millepurpan possess pro-apoptotic properties and potentiate the cytotoxicity of chemotherapy drugs in multidrug resistant P388 leukemia cells by modulating P-gp-mediated efflux of drugs. These flavonoids may be used as chemopreventive agents or as sensitizer to enhance cytotoxicity of chemotherapy drugs in multidrug resistant cancer cells.

Cytotoxicity and apoptosis induced by alfalfa (Medicago sativa) leaf extracts in sensitive and multidrug-resistant tumor cells.

Alfalfa (Medicago sativa) has been used to cure a wide variety of ailments. However, only a few studies have reported its anticancer effects. In this study, extracts were obtained from alfalfa leaves and their cytotoxic effects were assessed on several sensitive and multidrug-resistant tumor cells lines. Using the mouse leukaemia P388 cell line and its doxorubicin-resistant counterpart (P388/DOX), we showed that the inhibition of cell growth induced by alfalfa leaf extracts was mediated through the induction of apoptosis, as evidenced by DNA fragmentation analysis. The execution of programmed cell death was achieved via the activation of caspase-3, leading to PARP cleavage. Fractionation of toluene extract (To-1), the most active extract obtained from crude extract, led to the identification of 3 terpene derivatives and 5 flavonoids. Among them, (-)-medicarpin, (-)-melilotocarpan E, millepurpan, tricin, and chrysoeriol showed cytotoxic effects in P388 as well as P388/DOX cells. These results demonstrate that alfalfa leaf extract may have interesting potential in cancer chemoprevention and therapy.

In vitro and in vivo anti-tumoral effect of curcumin against melanoma cells.

Curcumin, the active ingredient from the spice turmeric (Curcuma longa Linn), is known to be an anti-oxidant and an anti-inflammatory agent. It has been demonstrated recently to possess anti-angiogenic effects and pro-apoptotic activities against Ehrlich ascites tumor cells. In the current study, curcumin was found to be cytotoxic in vitro for B16-R melanoma cells resistant to doxorubicin either cultivated as monolayers or grown in three-dimensional (3-D) cultures (spheroids). We have demonstrated that the cytotoxic effect observed in the 2 culture types can be related to the induction of programmed cell death. In our in vivo studies, we examined the effectiveness of a prophylactic immune preparation of soluble proteins from B16-R cells, or a treatment with curcumin as soon as tumoral appearance, alone or in combination, on the murine melanoma B16-R. The combination treatment resulted in substantial inhibition of growth of B16-R melanoma, whereas each treatment by itself showed little effect. Moreover, animals receiving the combination therapy exhibited an enhancement of their humoral anti-soluble B16-R protein immune response and a significant increase in their median survival time (> 82.8% vs. 48.6% and 45.7% respectively for the immunized group and the curcumin-treated group). Our study shows that curcumin may provide a valuable tool for the development of a therapeutic combination against the melanoma.

Gallium in cancer treatment.

Gallium (Ga) is the second metal ion, after platinum, to be used in cancer treatment. Its activities are numerous and various. It modifies three-dimensional structure of DNA and inhibits its synthesis, modulates protein synthesis, inhibits the activity of a number of enzymes, such as ATPases, DNA polymerases, ribonucleotide reductase and tyrosine-specific protein phosphatase. Ga alters plasma membrane permeability and mitochondrial functions. Ga salts are taken up more efficiently and more specifically by tumour cells when orally administered. New compounds have been prepared: Ga maltolate, doxorubicin-Ga-transferrin conjugate and Tris(8-quinolinolato)Ga(III), which show interesting activities. Ga toxicity is well documented in vitro and in vivo in animals. In humans, the oral administration Ga is less toxic, and allows a chronic treatment, allowing an improvement of its bioavailability in tumours, by comparison with the parenteral use. The anticancer activity of Ga salts has been demonstrated but other effects have also been noted such as many bone effects that could be useful in bone metastatic patients. Its has also been shown that a long period of administration could induce tumour fibrosis. Ga is synergistic with other anticancer drugs. Although not as potent as platinum in vitro, the anticancer activity of Ga should not be ignored, but the schedule of administration still needs to be optimised and new compounds are now under clinical investigations.