Apoptotic activity of caged xanthones from Garcinia hanburyi in cholangiocarcinoma cell lines.
OBJECTIVE
To investigate the growth inhibitory mechanism of four caged xanthones from Garcinia hanburyi in cholangiocarcinoma (CCA) KKU-100 and KKU-M156 cells.


METHODS
Four caged xanthones, selected on the basis of their anticancer potency and chemical structure diversities (i.e. isomorellin, isomorellinol, forbesione and gambogic acid) were used in this study. Growth inhibition of these caged xanthones was determined using the sulforhodamine B assay. Induction of apoptosis was assessed by observing cell morphology, ethidium bromide and acridine orange staining and DNA fragmentation assay. Levels of apoptotic-related gene and protein expressions were determined by a real-time reverse transcriptase polymerase chain reaction and Western blotting analysis, respectively.


RESULTS
The compounds were found to inhibit growth of both cell lines in a dose-dependent manner and also showed selective cytotoxicity against the cancer cells when compared with normal peripheral blood mononuclear cells. Growth suppression by these compounds was due to apoptosis, as evidenced by the cell morphological changes, chromatin condensation, nuclear fragmentation, and DNA ladder formation. At the molecular level, these compounds induced down-regulation of Bcl-2 and survivin proteins with up-regulation of Bax and apoptosis-inducing factor proteins, leading to the activation of caspase-9 and -3 and DNA fragmentation. The functional group variations did not appear to affect the anticancer activity with regard to the two CCA cell lines; however, at a mechanistic level, isomorellinol exhibited the highest potency in increasing the Bax/Bcl-2 protein expression ratio (120 and 41.4 for KKU-100 and KKU-M156, respectively) and in decreasing survivin protein expression (0.01 fold as compared to control cells in both cell lines). Other activities at the molecular level indicate that functional groups on the prenyl side chain may be important.


CONCLUSIONS
Our findings for the first time demonstrate that four caged xanthones induce apoptosis in CCA cells which is mediated through a mitochondria-dependent signaling pathway.
Hahnvajanawong
Chariya
C
Department of Microbiology, Center of Excellence for Innovation in Chemistry, Faculty of Medicine, Khon Kaen University, Khon Kaen 40002, Thailand.
Boonyanugomol
Wongwarut
W
Nasomyon
Tapanawan
T
Loilome
Watcharin
W
Namwat
Nisana
N
Anantachoke
Natthinee
N
Tassaneeyakul
Wichittra
W
Sripa
Banchob
B
Namwat
Wises
W
Reutrakul
Vichai
V
D017209:Apoptosis / Q000187:drug effects; D001483:Base Sequence; D001650:Bile Duct Neoplasms / Q000188:drug therapy* / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D001653:Bile Ducts, Intrahepatic; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D018281:Cholangiocarcinoma / Q000188:drug therapy* / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D017931:DNA Primers / Q000235:genetics; D029760:Garcinia / Q000737:chemistry; D015870:Gene Expression / Q000187:drug effects; D006571:Heterocyclic Compounds / Q000494:pharmacology; D006801:Humans; D044004:Xanthones / Q000737:chemistry / Q000494:pharmacology*
D017931:DNA Primers; D006571:Heterocyclic Compounds; D044004:Xanthones; C482271:forbesione; C579425:isomorellin; C052659:gambogic acid
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