OBJECTIVEThe goal of study is to explore the cytotoxic activity and its underlying mechanisms of the extract of Spatholobus suberctus in human lung cancer A549 cells.

METHODThe inhibitory effects of the extract on proliferation of human lung cancer cell line A549 was measured by MTT cell viability assay and growth curve. Cell cycle was analyzed using flow cytometry. Apoptotic morphological changes was observed by HE staining technique and AO/PI double-staining confocal laser scanning microscope (CLSM). Employing agarose gel electrophoresis and Annexin V-PI assay, we examed the presence of cytoplasmic histone-associated DNA fragments, and membrane phosphatidylserine (PS) externalization as well as caspase-3 activation.

RESULTThe extract of S. suberctus shows strong cytotoxic power on A549 cells during 24 hours and IC50 is 25.54 mg x L(-1). The cells in S-phase increase while the cells in G0-G1 and G2-M decrease. These changes recovered after 48 hours. The nucleus became pyknosis between 8 to 12 hours and many vacuoles and granules in cytoplasm can be seen. Membrane phosphatidylserine externalization occurs in a dose-dependent and time-dependent manner afer 12 hours. Caspase-3 activity has no more changes in a converse dose-dependent manner. No cytoplasmic histone-associated DNA fragments was detected by agarose gel electrophoresis.

CONCLUSIONThe extract of S. suberctus shows a direct anti-tumor activity. The drug acts quickly and causes S delay in one cell cycle. The main cell death feature appears to be non-apoptotic programmed cell death.