Anticancer activity of extracts derived from the mature roots of Scutellaria baicalensis on human malignant brain tumor cells

Abstract

Background: Flavonoid-rich extracts from the mature roots of Scutellaria baicalensis have been shown to exhibit antiproliferative effects on various cancer cell lines. We assessed the ability of an ethanolic extract of S. baicalensis root to inhibit the proliferation of malignant glioma cells.

Methods: Cell lines derived from primary and recurrent brain tumors from the same patient and cells selected for resistance to the chemotherapeutic agent 1,3-bis(2-chloroethyl)-1-nitrosourea (BCNU) were used to identify antiproliferative effects of this extract when used alone and in conjunction with BCNU.

Results and discussion: Results indicated that Scutellaria baicalensis not only inhibits cellular growth in recurrent and drug resistant brain tumor cell lines, but also demonstrates an increased inhibitory effect when used in conjunction with BCNU.

Conclusion: The results of this study support the efficacy of S. baicalensis as an anticancer agent for glioblastomas multiforme and a potential adjuvant treatment to current chemotherapeutic agents used in the treatment of both primary and recurrent GBMs. Further studies of the effects of individual flavonoids alone and in combination with each other and with currently used therapies are needed.

Figure 1

Time course treatment of ME series cells with S. baicalensis extract. Metabolic activity was measured using AlamarBlue™. Wells were subconfluent on Day 0. Cells were left untreated (■-■), mock treated with 0.4% ethanol (∇-∇) or treated with a 0.4% ethanol solution containing 100 μg/ml S. baicalensis extract (△-△). Data is mean ± SD using 5 replicates. (A) cells from primary tumor (ME), (B) ME cells selected for resistance to 10 μg/ml BCNU (ME drug), (C) cells from recurrent tumor (MER), (D) cells from recurrent tumor selected for resistance to 10 μg/ml BCNU (MER drug).

Figure 2

Dose-dependent inhibition of glioma cell proliferation by Scutellaria baicalensis extract. Glioma cell lines from primary tumors (ME and DI) and recurrent (MER and DIR) tumors, as well as BCNU resistant (designated "Drug") glioma cell lines were cultured with various concentrations of S. baicalensis extract (0–200 μg/ml). After treatment, cells were incubated for 14 days to allow for colony growth. Colonies of at least 50 cells were counted using a 4% Giemsa stain. Results were normalized to the control (untreated cells). Data show means ± SD of 3 replicates.

Figure 3

Dose-dependent growth inhibition of a low-passage glioma cell line by an extract from S. baicalensis. The viability of cell line 00WA following treatment with 0–200 μg/ml of S. baicalensis extract was tested by trypan blue exclusion at serial passage 5. Results are the mean ± SD of 2 replicates and data were normalized to the control.

Figure 4

The cytotoxic effects of Scutellaria baicalensis extract on normal glial cells and glioma cells. Wells were essentially confluent at the beginning of the experiment. (A) Metabolic activity of normal glial cells (HJ) and cells from a recurrent tumor (MER) were measured using the AlamarBlue™ metabolic assay. Glioma cells were cultured with 100 μg/ml of the S. baicalensis extract for approximately 48 hours. Results were presented as a percentage of the control (untreated). Data show means ± SD of 3 replicates. (B) Photomicrographs of cells 48 hours following treatment with 100 μg/ml of S. baicalensis extract.

Figure 5

The effects of Scutellaria baicalensis extract (50 μg/ml) and BCNU on glioma cell viability in BCNU-resistant and low passage cell lines. (A) Glioma cell lines from primary and recurrent tumors (ME/MER; DI/DIR) selected for resistance to 10 μg/ml BCNU (designated "Drug") were treated with either 50 μg/ml of S. baicalensis extract alone (Scut.), 2.5 μg/ml of BCNU alone, or a combination of the S. baicalensis extract and BCNU (Scut. + BCNU). (B) Low passage cells from tumor 00WA were treated with either 50 μg/ml of S. baicalensis extract alone (Scut.), 5 μg/ml of BCNU alone, or a combination of the S. baicalensis extract and BCNU (Scut. + BCNU). The percentage of viable cells following 3 consecutive days of treatment was assessed using a trypan blue exclusion assay. Results are normalized to the control (untreated) cells and data is the mean ± SD for 2 replicates.

Figure 6

Photomicrographs of ME Drug cells (selected for resistance to 10 μg/ml BCNU) treated with either (B) 5 μg/ml BCNU, (C) 50 μg/ml of S. baicalensis extract, (D) or a combination of S. baicalensis extract and BCNU. Glioma cells were treated for 3 consecutive days and then compared to the (A) control (untreated) cells.