The inhibitory effect of Gleditsia sinensis on cyclooxygenase-2 expression in human esophageal squamous cell carcinoma

The anti-cancer effects of the anomalous fruit extract of Gleditsia sinensis (GSE) attributed to its apoptotic activity, telomerase inhibition and anti-angiogenesis in a panel of solid and non-solid tumor cell lines including esophageal squamous cell carcinoma (ESCC) have been intensively investigated by us in previous studies. Cyclooxygenase-2 (COX-2) has been well described as another promising target of cancer therapy for ESCC, and novel therapeutic agents are still being sought which target COX-2 expression. However, the anti-cancer effect of GSE through the suppression of COX-2 expression has not been previously investigated. In the present study, the anti-cancer effects of GSE on eight ESCC cell lines (KYSE 30, KYSE 150, KYSE 450, KYSE 510, KYSE 520, HKESC-3, HKESC-4 and SLMT-1) of Chinese and Japanese origins were first studied by MTS cytotoxicity assays. The effects of GSE on COX-2 expression levels and on the housekeeping form COX-1 were also investigated by multiplex RT-PCR analysis. Moreover, the anti-proliferative effect of GSE on KYSE 510 was also studied by anchorage-independent clonogenicity assay in soft agar. The results showed that GSE induced a dose- and time-dependent cytotoxicity on all of the eight ESCC cell lines and caused positive anti-proliferative action on KYSE 510 in the anchorage-independent clonogenicity assay, suggesting that GSE suppressed the in vitro growth of the ESCC cell lines. More importantly, the MRNA expression levels of COX-2, but not COX-1, in all of the ESCC cell lines were suppressed by GSE in a dose-dependent fashion. The overall results of the present study show that the anti-cancer effect of GSE on the ESCC cell lines is associated with the suppression of COX-2 expression, but not COX-1. Our findings also open a new chapter for the future advancement of GSE as a novel anti-cancer agent or as an adjuvant of traditional cancer treatments.

Identification of a tumor suppressive critical region mapping to 3p14.2 in esophageal squamous cell carcinoma and studies of a candidate tumor suppressor gene, ADAMTS9

A gene critical to esophageal cancer has been identified. Functional studies using microcell-mediated chromosome transfer of intact and truncated donor chromosomes 3 into an esophageal cancer cell line and nude mouse tumorigenicity assays were used to identify a 1.61 Mb tumor suppressive critical region (CR) mapping to chromosome 3p14.2. This CR is bounded by D3S1600 and D3S1285 microsatellite markers. One candidate tumor suppressor gene, ADAMTS9, maps to this CR. Further studies showed normal expression levels of this gene in tumor-suppressed microcell hybrids, levels that were much higher than observed in the recipient cells. Complete loss or downregulation of ADAMTS9 gene expression was found in 15 out of 16 esophageal carcinoma cell lines. Promoter hypermethylation was detected in the cell lines that do not express this gene. Re-expression of ADAMTS9 was observed after demethylation drug treatment, confirming that hypermethylation is involved in gene downregulation. Downregulation of ADAMTS9 was also found in 43.5 and 47.6% of primary esophageal tumor tissues from Hong Kong and from the high-risk region of Henan, respectively. Thus, this study identifies and provides functional evidence for a CR associated with tumor suppression on 3p14.2 and provides the first evidence that ADAMTS9, mapping to this region, may contribute to esophageal cancer development.

Antiproliferative activity of the extract of Gleditsia sinensis fruit on human solid tumour cell lines

BACKGROUND

The fruit extract of Gleditsia sinensis Lam. (GSE) is a traditional herbal medicine that is saponin-rich. However, its activity on solid tumour cell lines has never been demonstrated.

METHODS

The activity of GSE was demonstrated in four cancer cell lines (breast cancer MCF-7, MDA-MB231, hepatoblastoma HepG2 and oesophageal squamous carcinoma cell line SLMT-1) using MTT assay, anchorage-independent clonogenicity assay, DNA laddering and in situ cell death detection.

RESULTS

The mean MTT(50) (the mean concentration of GSE to reduce MTT activity by 50%) ranged from 16 to 20 microg/ml of GSE. An anchorage-independent clonogenicity assay showed that all of the four solid tumour cell lines gradually lost their regeneration potential after treatment with GSE, DNA fragmentation and TUNEL analysis demonstrated that the action of GSE is both dose- and time course-dependent.

CONCLUSIONS

Our results suggest that GSE has a cytotoxic activity and can induce apoptosis in human solid tumour cell lines.