Evaluation of energy state of islet independent of size using a newly developed ATP bioluminescence assay

ATP content or energy charge (EC) of islets may be a good parameter to assess viability. In this study, we examined adenine nucleotides and EC of freshly isolated or 24-hour cultured rat islets of various diameters using a novel bioluminescent enzymatic cycling assay system. For freshly isolated islets, ATP content and islet diameter showed a high correlation (r = 0.842, P < .001), but a significant correlation was not observed for cultured islets (r = 0.284) when all islets were included for the analysis. When only the cultured islets with a diameter <350 microm were included for analysis, a significant correlation was observed (r = 0.719). EC of freshly isolated islets fluctuated widely irrespective of diameter, in contrast with results of 24-hour cultured islets, which showed a stable, high EC, regardless of diameter. These data suggest that the ATP content of islets correlates with the islet size and that EC of islets widely fluctuates following isolation, indicating a significant role of monitoring ATP and EC of islets before transplantation.

Phylogeographic origin of Hokkaido house mice (Mus musculus) as indicated by genetic markers with maternal, paternal and biparental inheritance

We examined intraspecies genetic variation in house mice (Mus musculus molossinus) from the northern third of the Japanese Islands, in order to obtain evidence of the history of mouse colonization that might have shaped the current genetic diversity. We extended the previous sampling of mitochondrial cytochrome b sequence and added information from the Y-linked Sry gene and ribosomal RNA gene surveys. We distinguish mitochondrial haplotypes characteristic of the North Asian musculus subspecies group (involving M. m. musculus and M. m. molossinus) as 'MUS', and that of the Southeast Asian castaneus subspecies group as 'CAS' (although the mice resemble MUS morphologically). There was a clear geographic partition of MUS and CAS types into southern and northern Hokkaido, respectively. Conversely, on Tohoku, the MUS and CAS types were interspersed without clear geographic subdivision. In contrast to the mtDNA data, all Hokkaido and Tohoku mice examined were found to possess a unique type for the Y-linked Sry gene, specific to Korea and Japan. Restriction site analysis of nuclear rDNA probe showed a consistent distribution of MUS and CAS types, as major and minor components, respectively, in the Hokkaido and Tohoku mice. These data support the previous notion that the Hokkaido and Tohoku mice experienced genetic hybridization between primary residents of CAS origin and MUS newcomers arriving via a southern route. The invasion of the MUS type could correspond with the evidence for arrival of prehistoric peoples. There are, however, alternative interpretations, including genetic admixture between MUS arriving by a southern route and CAS from a northern route.

RASSF2, a potential tumour suppressor, is silenced by CpG island hypermethylation in gastric cancer

RASSF2, a member of the RASSF1 family, has recently been identified as a potential tumour suppressor. We examined methylation status in multiple regions which included the CpG island and spanned the transcription start site of RASSF2 in 10 gastric cancer cell lines, as well as 78 primary gastric cancers and corresponding non-neoplastic gastric epithelia. Hypermethylation of RASSF2 in at least one of the regions examined was detected in seven (70%) of the 10 cell lines; two (20%) exhibited hypermethylation in all the regions examined including the transcription start site and lost expression of RASSF2 mRNA, which could, however, be restored by 5-aza-2′ deoxycytidine treatment, while the other five (50%) cell lines exhibited hypermethylation at the 5′- and/or 3′- edge, with four of them expressing RASSF2 mRNA. In primary gastric cancers and corresponding non-neoplastic gastric epithelia, frequencies of RASSF2 methylation ranged from 29% (23 out of 78) to 79% (62 out of 78) and 3% (two out of 78) to 60% (47 out of 78), respectively, at different CpG sites examined. Methylation was frequently observed at the 5′- and 3′- edges, and became less frequent near the transcription start site in both the primary gastric cancers and corresponding non-neoplastic gastric epithelia. Hypermethylation near the transcription start site was mostly cancer-specific. We thus showed that RASSF2 is silenced by hypermethylation near the transcription start site in gastric cancer. Hypermethylation was found initially to occur at the 5′- and 3′- furthest regions of the CpG island in non-neoplastic gastric epithelia, to gradually spreads near the transcription start site to shut down RASSF2 expression, and ultimately to constitute a field-defect placing tissue increased risk for development of gastric cancer.

Gene expression profiles in human gastric cancer: expression of maspin correlates with lymph node metastasis

To seek for a candidate gene that would regulate tumour progression and metastasis in gastric cancer, we investigated gene expression profiles by using DNA microarray. Tumour tissue and adjacent normal tissue were obtained from 21 patients with gastric cancer and then examined for their gene expression profiles by the Gene Chip Human U95Av2 array, which includes 12 000 human genes and EST sequences. A total of 25 genes were upregulated and two genes were downregulated by at least four-fold in the tumour tissue. In a further analysis according to lymph node metastasis, the expressed levels of maspin, as well as carcinoembryonic antigen and nonspecific crossreacting antigen were significantly higher in tumours with lymph node metastasis than in those without it. Maspin expression in 85 gastric cancer patients was further investigated by using immunohistochemistry. Maspin expression was not observed in normal gastric epithelia without intestinal metaplasia. In contrast, maspin was expressed in 74 of 85 tumour tissues. There was a significant correlation between the incidence of maspin-positive tumour staining and lymph node metastasis. These results suggest that maspin has a potential role for tumour metastasis in gastric cancer.

A novel method for determination of ATP, ADP, and AMP contents of a single pancreatic islet before transplantation

Assessment of islet viability before transplantation is mandatory for successful clinical transplantation. ATP content or energy charge (EC) of islets may represent a good parameter to assess viability. We have introduced a novel bioluminescent enzymatic cycling assay using synthetic firefly luciferase, pyruvate kinase) (PK), and pyruvate orthophosphate dikinase (PPDK) to determine adenine nucleotides (AN) in isolated islets. A complete assay requires several minutes. The ATP contents of 1, 3, 10, 30 or 100 islets each with a diameter of 150 microm were 9.95 +/- 0.03, 28.3 +/- 1.18, 89.5 +/- 1.48, 282 +/- 10.2, and 673 +/- 27.1 pmol, respectively, showing a relatively constant ATP content per 30 islets (9.95, 9.42, 8.95, and 9.41 pmol/IEQ). ECs of each group were 0.74 +/- 0.02, 0.74 +/- 0.02, 0.75 +/- 0.02, 0.74 +/- 0.02, and 0.65 +/- 0.01, respectively, a value that was quite constant up to 30 islets. The quantity of ATP and EC in a single islet can be measured quickly and reproducibly, offering a new method to determine viability of isolated islets prior to transplantation.

Prognostic significance of peritoneal minimal residual disease in gastric cancer detected by reverse transcription-polymerase chain reaction

BACKGROUND

A sensitive method for detecting minimal residual disease in the peritoneal cavity by quantifying carcinoembryonic antigen (CEA) mRNA using real-time quantitative reverse transcription-polymerase chain reaction (RQ-RT-PCR) was developed. The clinical value of the method for predicting peritoneal recurrence in patients with gastric cancer was evaluated.

METHOD

A total of 195 patients with gastric cancer and 20 with asymptomatic cholecystolithiasis were included in the study. CEA mRNA expression in peritoneal washings (p-CEA mRNA) was measured by RQ-RT-PCR and normalized to glyceraldehyde-3-phosphate dehydrogenase mRNA expression. The cut-off level of p-CEA mRNA for gastric cancer was determined by examining p-CEA mRNA levels in patients with asymptomatic cholecystolithiasis.

RESULTS

Fifty-five (28.2 per cent) of the 195 patients were p-CEA mRNA positive. The rate of p-CEA mRNA positivity correlated significantly with clinicopathological factors. In 163 patients who underwent curative surgery, overall survival and disease-free survival were significantly poorer in p-CEA mRNA-positive patients than in p-CEA mRNA-negative patients (P < 0.001). Cox regression analysis revealed that only p-CEA mRNA was a significant independent prognostic factor (P = 0.034). Multivariate logistic regression analysis showed that p-CEA mRNA was a significant independent risk factor for peritoneal recurrence (P = 0.027).

CONCLUSION

These results suggest that p-CEA mRNA is a reliable prognostic factor and predictor of peritoneal recurrence in gastric cancer.

Demethylation of MAGE promoters during gastric cancer progression

Melanoma antigen (MAGE)-encoding genes are expressed in various tumour types via demethylation of their promoter CpG islands, which are silent in all non-neoplastic tissues except for the testis and placenta. The clinicopathological significance of demethylation of MAGE genes in gastric carcinoma is not known. We investigated the promoter methylation status of MAGE-A1 and -A3 in 10 gastric cancer cell lines and in surgical specimens from 84 gastric cancer patients by methylation-specific PCR (MSP). Expression of MAGE-A1 and -A3 in the 10 gastric cancer cell lines was also investigated by RT–PCR. Any correlation between the methylation status of the MAGE promoters and clinicopathological characteristics of the gastric cancer patients was then assessed. Eight of the 10 gastric cancer cell lines showed demethylation of both MAGE-A1 and -A3, and the remaining two cell lines did either of MAGE-A1 or -A3. Expression of MAGE-A1 and -A3 was confirmed in seven and nine of the 10 gastric cancer cell lines, respectively. The MAGE-A1 and -A3 promoters were demethylated in 29% (25 out of 84) and 66% (56 out of 84) of the gastric tumour specimens, respectively. Demethylation of both MAGE-A1 and -A3 promoters (n=22) was found more frequently in gastric cancer patients in advanced clinical stages (P=0.0035), and these patients also exhibited a higher incidence of lymph node metastasis (P=0.0007) compared to those patients without demethylation (n=25). Furthermore, demethylation patients tended to have a worse prognosis, although this difference was not statistically significant (P=0.183). Demethylation of MAGE-A1 and -A3 occurs during progressive stages of gastric cancer, and may be associated with aggressive biological behaviour of gastric cancer.

Superior antitumour activity of S-1 in tumours with a high dihydropyrimidine dehydrogenase activity

To elucidate the mechanism of the enhanced antitumour activity of S-1 (1 M tegafur, 0.4 M 5-chloro-2, 4-dihydroxypyridine, and 1 M potassium oxonate) in terms of the phosphorylation and degradation pathways of 5-fluorouracil (5-FU) metabolism, we investigated tumoral thymidylate synthase (TS) content, dihydropyrimidine dehydrogenase (DPD) activity, the TS inhibition rate (TS-IR), and 5-FU incorporated into RNA (F-RNA) in four human gastric cancer xenografts (MKN-28, MKN-74, GCIY and GT3TKB) and compared the results obtained with S-1 with those obtained with 5-FU and UFT (1 M tegafur, 4 M uracil). 5-FU was administered intraperitoneally (i.p.) to mice at a dose of 50 mg/kg, three times, on days 0, 4 and 8. S-1 and UFT were administered orally at doses of 10 and 24 mg/kg, respectively, once a day, for 9 consecutive days. Antitumour activity was evaluated as the maximum inhibition of tumour growth in each animal. S-1 showed a better antitumour activity than 5-FU and UFT in tumours with a high DPD activity (GCIY and GT3TKB). There were inverse correlations between the antitumour activity and both TS content and DPD activity in the 5-FU and UFT groups. However, no such correlations were observed in the S-1 group. In GCIY and GT3TKB xenografts, TS-IR was significantly higher in the S-1 group than in the 5-FU or UFT groups. In GT3TKB xenografts, the F-RNA level was significantly higher in the S-1 group than in the 5-FU or UFT groups. The superior cytotoxicity of S-1 appears to be attributable to both an increased inhibition of DNA synthesis and an enhanced blockade of RNA function against tumours with a high DPD activity.

Role of thymidine phosphorylase and dihydropyrimidine dehydrogenase in tumour progression and sensitivity to doxifluridine in gastric cancer patients

This study was designed to investigate the role of thymidine phosphorylase (TP) and dihydropyrimidine dehydrogenase (DPD) on tumour progression and sensitivity to 5'-deoxy-5-fluorouridine (5'-DFUR). Tumour tissue was obtained from surgically resected samples from 93 patients with primary gastric cancer. Tumour TP and DPD expression levels were determined by the enzyme-linked immunosorbent assay (ELISA) system and compared with several clinicopathological factors and in vitro sensitivity to 5'-DFUR. DPD showed no correlation with any clinicopathological factors. However, the TP level was significantly correlated with the depth of tumour, lymphatic invasion and venous invasion. In comparison with 5'-DFUR sensitivity, there was a weak inverse correlation between the DPD level and the sensitivity to 5'-DFUR (r(s)=-0.361). Furthermore, the TP/DPD ratio showed a significant correlation with 5'-DFUR sensitivity (r(s)=0.634). In a subgroup of patients with postoperative 5'-DFUR administration, the survival rate was significantly better in patients with a high TP/DPD ratio (n=8) than in those with low TP/DPD ratio (n=14) (P=0.0140). These results suggest that sensitivity to 5'-DFUR is predictable by measurement of both TP and DPD levels.