Sphaeranthus indicus induces apoptosis through mitochondrial-dependent pathway in HL-60 cells and exerts cytotoxic potential on several human cancer cell lines.

PURPOSE: The study was designed to screen Sphaeranthus indicus, Ganoderma lucidum, and Urtica dioica for their anticancer activity against human cancer cell lines. Phytochemical screening of active extracts was also planned.

METHODS: Petroleum ether, ethanolic, and aqueous extracts of S indicus Linn, G lucidum P Karst, and U dioica Linn were subjected to cytotoxicity studies using 7 different cancer cell lines. Potent cytotoxicity was noted in petroleum ether extract of S indicus (SIP), which inhibited proliferation of various cancer cell lines. Growth inhibition was determined by sulforhodamine B assay. Two biochemical markers, namely β-sitosterol and 7-hydroxyfrullanolide were isolated and characterized using high-performance thin layer chromatography, melting point, Fourier transform infrared spectroscopy, nuclear magnetic resonance spectroscopy, and mass analysis. Cytotoxicity of isolated β-sitosterol and 7-hydroxyfrullanolide were also determined. The IC(50) of SIP was calculated in the HL-60 cells and was found to be 53 µg/mL. Furthermore, SIP induced apoptosis in human leukemia HL-60 cells as measured by several biological end points. Cell cycle analysis and change in mitochondrial membrane potential was quantified by flow cytometry. Subsequently, using annexin V/PI assay, proportion of cells actively undergoing apoptosis was determined. Changes in DNA were observed by DNA ladder assay.

RESULTS: SIP induced apoptotic bodies formation, induced DNA laddering, enhanced annexin-V-FITC binding of the cells, increased sub-G(0) DNA fraction, and induced loss of mitochondrial membrane potential (ΔΨm) in HL-60 cells. SIP also elevated the caspase 3 and caspase 9 levels in the HL-60 cells, which clearly indicates the involvement of the intrinsic proteins in inducing apoptosis.

DISCUSSION: All the above parameters revealed that SIP induced apoptosis through the mitochondrial-dependent pathway in HL-60 cells. The criterion for anticancer activity in cytotoxicity assay was ≥70% growth inhibition at 100 µg/mL against at least 4 cell lines. As G lucidum and U dioica did not exhibit appreciable inhibitory activity against human cancer cell lines (less than 50%), they were not included in the study thereafter. The results established that SIP has apoptosis-inducing effect against HL-60 cells in vitro and is a promising candidate for further anticancer study. β-Sitosterol and 7-hydroxyfrullanolide can be considered to be potent anticancer compounds isolated from SIP on the basis of present studies.