Abstract
The aim of this study was to investigate the cytotoxic and apoptotic effects of Nephelium ramboutan-ake (pulasan) rind in selected human cancer cell lines. The crude ethanol extract and fractions (ethyl acetate and aqueous) of N. ramboutan-ake inhibited the growth of HT-29, HCT-116, MDA-MB-231, Ca Ski cells according to MTT assays. The N. ramboutan-ake aqueous fraction (NRAF) was found to exert the greatest cytotoxic effect against HT-29 in a dose-dependent manner. Evidence of apoptotic cell death was revealed by features such as chromatin condensation, nuclear fragmentation and apoptotic body formation. The result from a TUNEL assay strongly suggested that NRAF brings about DNA fragmentation in HT-29 cells. Phosphatidylserine (PS) externalization on the outer leaflet of plasma membranes was detected with annexin V-FITC/PI binding, confirming the early stage of apoptosis. The mitochondrial permeability transition is an important step in the induction of cellular apoptosis, and the results clearly suggested that NRAF led to collapse of mitochondrial transmembrane potential in HT-29 cells. This attenuation of mitochondrial membrane potential (Δψm) was accompanied by increased production of ROS and depletion of GSH, an increase of Bax protein expression, and induced-activation of caspase-3/7 and caspase-9. These combined results suggest that NRAF induces mitochondrial-mediated apoptosis.
Highlights
Cancer is a major health problem of global concern and is the second leading cause of death.Among various types of cancer, colorectal cancers are the third most common cancer in both men and women [1]
The results of the present study indicated that N. ramboutan-ake aqueous fraction (NRAF) exhibited the greatest cytotoxicity against HT-29, which may be associated with the high levels of tannins and saponins in this fraction
To further investigate whether NRAF-mediated cell death in HT-29 cells was due to apoptosis, the cells were double stained with Hoechst 33342/propidium iodide (PI) and the resulting nuclear morphological changes were observed under a fluorescence microscope
Summary
Cancer is a major health problem of global concern and is the second leading cause of death. The most prominent genes involved in these alterations include APC, K-ras, p53, c-myc, DNA mismatch repair genes, BRAF, PIK3CA and PTEN Accumulation of these alterations promotes the growth and results in clonal expansion of tumor cells [3,4]. It has been found that the intake of fresh fruits, vegetables and plants rich in natural antioxidants could be associated with the prevention of diseases such as cancer, diabetes mellitus and cardiovascular diseases [13,14] Tropical fruits such as mangosteen, rambutan, mango, pomegranate and others are lately found to contain large variety of substances possess antioxidant [15,16] anti-diabetic [17]. In the present study, we have investigated the cytotoxic effects of NRAF in HT-29 human colon adenocarcinoma cancer cells. We examined the effects of NRAF on apoptosis and suggest a possible NRAF-induced apoptotic mechanism for the observed activity
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