Abstract
Damulin B, a dammarane-type saponin from steamed Gynostemma pentaphyllum, exhibits the strongest activity against human lung carcinoma A549 cells among the
isolated active saponins. In this study, the structure-activity relationship of a
series of saponin compounds was discussed. The inhibitory effect of damulin B on human
lung cancer A549 and H1299 cells was investigated from apoptosis, cell cycle, and
migration aspects. In vitro, human lung cancer cells were more susceptible to damulin B treatment than human
normal fibroblasts. Damulin B exhibited a strong cytotoxic effect, as evidenced by
the increase of apoptosis rate, reduction of mitochondrial membrane potential (MMP),
generation of reactive oxygen species, and G0/G1 phase arrest. Furthermore, damulin
B activated the following: both intrinsic and extrinsic apoptosis pathways along with
early G1 phase arrest via the upregulation of the Bax, Bid, tBid, cleaved caspase-8,
and p53 expression levels; downregulation of the procaspase-8/-9, CDK4, CDK6, and
cyclin D1 expression levels; and more release of cytochrome c in the cytoplasm. In
addition, antimigratory activities and suppressive effects on metastasis-related factors,
such as MMP-2 and MMP-9, accompanied by the upregulation of IL-24 were revealed. Altogether,
the results proved that damulin B could inhibit human lung cancer cells by inducing
apoptosis, blocking the cell cycle at early G0/G1 phase and suppressing the migration.
Hence, damulin B has potential therapeutic efficacy against lung cancer.
Key words
Gynostemma pentaphyllum
- Curcubitaceae - saponin - damulin B - cytotoxicity - lung cancer