Cytotoxicity and cell death mechanisms against cancer cell lines elicited by the extracts of physalis minima L.
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Date
2009
Authors
Kheng Leong, Ooi
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Abstract
Herbal therapy is fast becoming an important alternative medicine for cancer
treatment. Therefore, the aims of this study were to determine cytotoxicity of some medicinal
herbs and to investigate cell death mechanism elicited by the most potent extract as well as its
fractions. A total of 20 extracts form four anticancer plants (Pereskia grandifo/ia, Vernonia
cinerea, Elephantopus scaber and Physalis minima) were screened against three different
cancer cell lines. Physalis minima (Leletup-direct translation from Malay) chloroform extract
was shown to exhibit remarkable cytotoxic effects on NCI-H23 (human lung
adenocarcinoma), T-470 (human breast carcinoma) and Caov-3 (human ovarian carcinoma)
cell lines, with EC50 derived at 2.80f.!g/ml, 3.80f.!g/ml and 5.10f.lg/ml, respectively. Different
cell death mechanisms exerted by this extract on different cell lines. It was found that DNA
fragmentation level of the extract-treated NCI-H23 and T-470 cells was higher than Caov-3
cells. Acute exposure to the extract produced a significant regulation of c-myc, caspase-3 and
p53 mRNA expression in all cell lines. Ultrastructural analysis and annexin V staining also
demonstrated the presence of apoptotic programmed cell death in the extract-treated cell lines.
Furthermore, the appearance of non-apoptotic (vacu?lar) morphology was observed in some
treated Caov-3 cells and in minority of treated NCI-H23 and T-470 cells. Trypan blue
exclusion assay ruled out necrosis as the main cause of death. Thus, cell death mechanism
elicited by the Physalis minima chloroform extract appeared to be a mixture of programmed
cell death in Caov-3 cells and a major apoptotic cell death in both NCI-H23 and T-470 cells.
Fractionation of Physalis minima chloroform extract revealed 16 different fractions. Only
some of the fractions exhibited cytotoxic activities against T-470 cells, with Fll being the
most potent, exhibiting the lowest EC50 (3.60f.!g/ml). Fractions FlO, Fll and F13 exhibited
typical DNA fragmentation associated with apoptosis in T-470 cells. Trypan blue exclusion
assay demonstrated that necrosis did not play a major role in eliciting T-47D cell death of
these fractions. Further investigations revealed both fraction F11 and chloroform extract
induced major apoptotic cell death in T-47D cells, which was based on majority of weakly
diffused annexin V stained cells and significant regulation of c-myc, caspase-3 and p53
mRNA expression levels. Meanwhile, a considerable number of T-47D cells treated with
fractions FlO and Fl3 were stained with annexin V and propidium iodide, which further
suggested the presence of a mixture programmed cell death. Physalins B, F and K were
identified as major constituents in fraction F 11. Combination of these physalin compounds in
the extract and fraction may have contributed to the cytotoxic activities and programmed celt
death of T-47D cells. These findings warrant further research on Physalis minima plant for
use in cancer therapy due to its apoptosis- and autophagy-dependent anticancer effect on
cancer cell lines.
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Keywords
Cell death , Cancer cell lines , Physalis minima l.