Induction of chromosome instability and stomach cancer by altering the expression pattern of mitotic checkpoint genes in mice exposed to areca-nut

Abstract

BackgroundThere are strong indications for a causal association between areca-nut consumption and cancers. In Meghalaya, India, the variety of areca-nut is used as raw and unprocessed form whose chemical composition and pharmacological actions have been reported. Yet we know little on the initial pathway involved in areca-nut associated carcinogenesis since it is difficult to assess its effects on genetic alterations without interference of other compounding factors. Therefore, present study was undertaken in mice to verify the ability of raw areca-nut (RAN) to induce cancer and to monitor the expression of certain genes involved in carcinogenesis. This study was not intended to isolate any active ingredients from the RAN and to look its action.MethodsThree groups of mice (n = 25 in each) were taken and used at different time-points for different experimental analysis. The other three groups of mice (n = 15 in each) were considered for tumor induction studies. In each set, two groups were administered RAN-extract ad libitum in drinking water with or without lime. The expression of certain genes was assessed by conventional RT-PCR and immunoblotting. The mice were given the whole RAN-extract with and without lime in order to mimic the human consumption style of RAN.ResultsHistological preparation of stomach tissue revealed that RAN induced stomach cancer. A gradual increase in the frequency of precocious anaphase and aneuploid cells was observed in the bone marrow cells with a greater increment following RAN + lime administeration. Levels of p53, Bax, Securin and p65 in esophageal and stomach cells were elevated during early days of RAN exposure while those of different mitotic checkpoint proteins were downregulated. Apoptotic cell death was detected in non-cancerous stomach cells but not in tumor cells which showed overexpression of Bax and absence of PARP.ConclusionPresent study suggested (a) RAN induces stomach cancer, however, presence of lime promoted higher cell transformation and thereby developed cancer earlier, (b) perturbations in components of the chromosome segregation machinery could be involved in the initial process of carcinogenicity and (c) the importance of precocious anaphase as a screening marker for identification of mitotic checkpoint defects during early days.

Análise comparativa do polimorfismo genético da glutationa transferase, do Helicobacter pylori e do vírus Epstein-Barr entre a área do tumor e as margens de ressecção proximal e distal do câncer gástrico.

“…Chromosomal instability and heterogeneous gene amplifications/deletions are associated with many malignances [20][21][22][23] . For gastric cancer, Noguchi et al 24 detected no chromosomal deletions of the GSTM1 and GSTT1 genes in their work.…”

Methanolic extract of Potentilla fulgens root and its ethyl-acetate fraction delays the process of carcinogenesis in mice

“…In this study, mice were given the whole RAN-extract and lime ad libitum in drinking water with dose increased every two months to mimic the human habit of consumption of RAN. In earlier studies with similar mode of treatment, parameters like precocious anaphase and expression of Securin and p53 genes were monitored at different time-points starting from 30 days to 300 days for understanding the process of RAN-induced carcinogenesis 8 . It was found that after 240 days of ad libitum administration of RAN extract with lime in drinking water all the mice developed gastric tumour.…”

“…Earlier studies highlighted the importance of precocious anaphase, which leads to aneuploidy, as a potential screening marker for identification of mitotic checkpoint defects during early days of RAN exposure in both mice and human 8,9,31 . As observed earlier 8 , present results also showed a gradual increase in the frequency of precocious anaphase and aneuploidy in the BMC of mice following RAN + lime administration. Very significantly frequencies of both were reduced following co-administeration of both PRE or ECGU.…”

“…It has also been reported that Helicobactor pylori infection enhances development of gastric cancers caused by chewing and swallowing RAN and lime 5 . In animal model also, tumours have been shown to be induced in esophagous, stomach and liver when RAN extract was administered either by oral intubation 6 or mixed with the diet 7 or by ad libitum admisteration of RAN extract with lime in drinking water 8 . In earlier studies, induction of precocious anaphase (premature separation of sister-chromatids) and higher expression of p53 and Securin in non-target tissues like mouse bone marrow cells (BMC) were observed to be significantly associated with an increased risk of RAN-induced gastric cancer 8 .…”

“…In animal model also, tumours have been shown to be induced in esophagous, stomach and liver when RAN extract was administered either by oral intubation 6 or mixed with the diet 7 or by ad libitum admisteration of RAN extract with lime in drinking water 8 . In earlier studies, induction of precocious anaphase (premature separation of sister-chromatids) and higher expression of p53 and Securin in non-target tissues like mouse bone marrow cells (BMC) were observed to be significantly associated with an increased risk of RAN-induced gastric cancer 8 . Subsequently, similar observation was made in human peripheral blood-lymphocytes of both oral and esophageal cancer patients and non-cancerous persons having the habit of consuming RAN 9 .…”