The enriched fraction of Elephantopus scaber Triggers apoptosis and inhibits multi-drug resistance transporters in human epithelial cancer cells

Abstract

Background: Medicinal plants have played an important role in the development of clinically useful anticancer agents. Elephantopus scaber (Asteraceae) (ES) is widely used in Indian traditional system of medicine for the treatment of various ailments including cancer.

Objective: To investigate anticancer effects of ES in human epithelial cancer cells.

Materials and methods: Cytotoxicity of ethanolic extract of ES (ES-ET) and its fractions, such as ES Petroleum ether fraction (ES-PET), ES Dichloromethane fraction (ES DCM), n Butyl alcohol fraction (ES-BT), and ES-Rest (ES-R) were assessed in human epithelial cancer cell lines using sulforhodamine B (SRB) assay. Acridine orange/ethidium bromide assay and Hoechst 33342 assays were used to gauge induction of apoptosis. Cell cycle analysis and micronuclei assay were used to assess cell cycle specific pharmacological effects and drug induced genotoxicty. Further, the ability of ES to inhibit multi drug resistant (MDR) transporters (ABC-B1 and ABC-G2) was determined by Rhodamine (Rho) and Mitoxantrone (MXR) efflux assays.

Results: The enriched fraction of ES (ES DCM) possessed dose-dependent potent cytotoxicity in human epithelial cancer cells. Further, treatment of cancer cells (HeLa, A549, MCF-7, and Caco-2) with ES DCM showed hall mark properties of apoptosis (membrane blebbing, nuclear condensation etc.). Similarly, ES DCM caused enhanced sub G0 content and micronuclei formation indicating the induction of apoptosis and drug induced genotoxicity in cancer cells, respectively. Interestingly, ES DCM inhibited MDR transporters (ABC B1 and ABC G2) in cancer cells.

Conclusion: The enriched fraction of ES imparted cytotoxic effects, triggered apoptosis, induced genotoxicity, and inhibited MDR transporters in human epithelial cancer cells. Thus, ES appears to be potential anticancer agent.

Keywords: Anti-cancer; Elephantopus scaber L; apoptosis; cytotoxicity; multi-drug resistance.

Supplementary Figure 1

High-performance thin layer chromatography (HPTLC) densitogram of enriched fraction of Elephantopus scaber dichloromethane fraction (ES-DCM). ES-DCM was dissolved in methanol (1 mg/mL) and analyzed (10 μL) using HPTLC (Camag Linomat-V). Mobile phase used was toluene: Ethyl acetate: Formic acid (6:3:1); detection wavelength at 366 nm; band length at 6 mm; and the solvent front at 85 mm

Figure 1

Dose-dependent cytotoxic effects of fractions of Elephantopus scaber (ES) in human epithelial cancer cells. Cervical carcinoma (HeLa), lung adenocarcinoma (A549), breast cancer cells (MCF-7, BT-474 and MDA-MB-231), and colon carcinoma (Caco₂) cells were treated with ES Ethanolic extract (ES-ET); ES Petroleum ether fraction (ES-PET), ES Dichloromethane fraction (ES-DCM), ES n-butyl alcohol fraction and ES Rest fraction for 48 h. At the end of the treatment, percentage cell viability was determined by sulforhodamine B assay. Each point represents the mean ± standard error of the mean of three independent experiments performed in triplicates

Figure 2

Apoptotic effects of enriched fraction of Elephantopus scaber (ES-DCM) in human epithelial cancer cells. Cervical carcinoma (HeLa), lung adenocarcinoma (A549), breast carcinoma (MCF-7), and colon carcinoma (Caco₂) cells were treated with the enriched fraction of ES (ES-DCM) for 48 h. Dimethyl sulfoxide and doxorubicin were used as vehicle control and positive control, respectively. At the end of the treatment, cells were harvested and stained to detect apoptosis using fluorescence microscopy. (a) Acridine orange/ethidium bromide staining to distinguish between necrosis and apoptosis. Uniformly stained green colored nuclei indicate live cells; condensed or fragmented nucleus with green or orange-red color indicates the apoptosis. (b) Hoechst 33342 staining to detect apoptosis. Condensed and fragmented nuclei indicate the hall mark properties of apoptosis. The data are representative of three independent experiments

Figure 3

Cell cycle inhibitory effects of enriched fraction of Elephantopus scaber (ES-DCM) in human epithelial cancer cells. Cervical carcinoma (HeLa), lung adenocarcinoma (A549), breast carcinoma (MCF-7), and colon carcinoma (Caco₂) cells were treated with the enriched fraction of ES (ES-DCM) for 48 h. Dimethyl sulfoxide and doxorubicin were used as vehicle control and positive control, respectively. At the end of the treatment, cells were harvested, stained with propidium iodide, and DNA content was analyzed using flow cytometry. Percentage DNA content in G₀/G₁, S, G₂M, and sub-G₀ were determined. The data represents mean ± standard error of the mean of three independent experiments

Figure 4

Genotoxicity of enriched fraction of Elephantopus scaber (ES-DCM) in human epithelial cancer cells. Cervical carcinoma (HeLa), lung adenocarcinoma (A549), breast carcinoma (MCF-7), and colon carcinoma (Caco₂) cells were treated with enriched fraction of Elephantopus scaber (ES-DCM) for 48 h. Dimethyl sulfoxide and doxorubicin were used as vehicle control and positive control, respectively. At the end of the treatment, cells were harvested and assessed for the frequency of micronuclei formation (micronucleated bi/tri-nucleate cells). The data are representative of three independent experiments

Figure 5

MDR-1 (ABC-B1) inhibitory effects of enriched fraction of Elephantopus scaber (ES-DCM) in human epithelial cancer cells. HeLa (a) and Caco-2 (b) cells were incubated with rhodamine 123 (Rho-123) in Dulbecco's modified eagle medium with 2% fetal bovine serum for 30 min at 37°C (accumulation phase), after which excess dye was washed and cells were re-incubated with vehicle control (dimethyl sulfoxide), verapamil, and ES-DCM for 60 min at 37°C (efflux phase). The mean cellular Rho-123 fluorescence in the efflux phase was analyzed by flow cytometry. Error bars represent ± standard error of the mean; n = 3, ***P < 0.001

Figure 6

ABC-G2 (BCRP) inhibitory effects of enriched fraction of Elephantopus scaber (ES-DCM) in human epithelial cancer cells. A549 (a) and MCF-7 (b) cells were incubated with mitoxantrone (MXR) in Dulbecco's modified eagle medium with 2% Fetal bovine serum for 30 min at 37°C (accumulation phase), after which excess dye was washed and cells were re-incubated with vehicle control (dimethyl sulfoxide), fumitremorgin C (FTC), and ES-DCM for 60 min at 37°C (efflux phase). The mean cellular MXR fluorescence in the efflux phase was analyzed by flow cytometry. Error bars represent ± standard error of the mean; n = 3, ***P < 0.001