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Background: Oct4 has been shown to present a stem cell marker that is expressed in embryonic cells and in germ cell tumors. Recently, its expression in a few human tissues and cancer cells has been reported. Because in the hamster pancreatic cancer model most tumors develop from within islets presumably from stem cells, we investigated the expression of Oct4 in this model. Methods: Two normal pancreases and 15 pancreatic cancers induced by N-nitrosobis(2-oxypropyl)amine (BOP) were processed for immunohistochemistry using a monoclonal Oct4 antibody at a concentration of 1:500. Results: In the normal pancreas, Oct4 was expressed only in islet cells in a diffuse cytoplasmic pattern. No nuclear staining was found in any cells. In 14 of the pancreatic cancers, nuclear staining was detected in many cells or in small foci. Diffuse cytoplasmic but no nuclear staining was found in one tumor and a mixed Golgi type and nuclear staining in two cases. Nuclear staining was also identified in early intrainsular ductular and in Ca in situ lesions. Conclusions: BOP reactivates the Oct4 gene and can be considered an early tumor marker in this model.

Background/Purpose Matrix metalloproteinases (MMPs) have been implicated as playing an important role in cancer invasion and metastasis. MMPs have been identified in various malignancies, including pancreatic duct adenocarcinomas. Methods We investigated the circulating level of MMP-2 and MMP-9 in sera from Syrian golden hamsters into which hamster pancreatic duct adenocarcinoma tissues had been transplanted subcutaneously (HPDt hamsters). Northern blot analysis and gelatin zymographic analysis were performed to detect the expression of MMPs and that of tissue inhibitors of metalloproteinases (TIMPs) in HPDt hamsters. Results Northern analysis revealed overexpression of MMP-2, MMP-9, and TIMP-2 mRNAs in subcutaneous tumors of HPDt hamsters as compared with normal pancreatic tissue. Sera from HPDt hamsters possessed significantly higher levels of serum MMP-2 and MMP-9 than control sera, as determined by gelatin zymographic analysis, and there was a significant correlation between tumor growth and serum MMP levels. Conclusions These results indicate that overexpression of MMP mRNAs is involved in the progression of pancreatic duct adenocarcinomas, and that MMP protein expression in hamster sera is associated with the presence of pancreatic duct adenocarcinoma cells. The findings also suggest that serum MMPs could be useful markers for monitoring patients with pancreatic duct adenocarcinomas.

A 57 year-old man presented with abdominal discomfort and melena. Abdominal ultrasonography clearly revealed a duodenal tumor as a hypoechoic mass in the transverse segment of the duodenum. The lesion was a 4 x 4-cm oval mass with partial concavity, an irregular surface, high-level central echoes, and a hypoechoic periphery. After confirmation of the diagnosis of duodenal carcinoma, a pylorus-preserving pancreatoduodenectomy was performed curatively. Pathological examination revealed moderately differentiated tubular adenocarcinoma partially invading the pancreatic parenchyma. Ultrasonography can be used to detect lesions of the transverse segment of the duodenum as the first imaging procedure.

BACKGROUND Previously, the authors reported the role of the vascular endothelial growth factor (VEGF) as an angiogenic factor in 40 patients with pancreatic carcinoma. In this study, they investigated the mechanism underlying the regulation of VEGF gene expression and evaluated VEGF expression and K-ras gene status in 48 patients with pancreatic carcinoma. METHODS The authors used quantitative reverse transcriptase-polymerase chain reaction analysis and direct sequencing techniques for a retrospective study of VEGF gene expression and K-ras gene status in tumor tissue samples from 48 patients with pancreatic carcinoma. Immunohistochemistry also was used to investigate VEGF protein expression. RESULTS Thirty-one tumors (64.6%) were evaluated with high VEGF expression, and 17 tumors (35.4%) were evaluated with low VEGF expression. Of the 48 primary pancreatic tumors studied, 33 tumors (68.8%) contained mutations of the K-ras gene. There was a significant correlation between VEGF expression and K-ras status. Twenty-five of 33 tumors (75.8%) with mutant K-ras genes showed high VEGF expression, whereas only 6 of 15 tumors with the wild type K-ras (40.0%) showed high VEGF expression (P = 0.038). The mean (± standard error) VEGF conservation rate for the 33 tumors with mutant K-ras was 1.839 ± 1.241, and that for the 15 tumors with wild type K-ras was 1.057 ± 0.983 (P = 0.037). Furthermore, the median survival for patients with mutant K-ras was shorter than for those with wild type K-ras (10.6 months vs. 27.6 months, respectively; P = 0.026), whereas the median survival for patients with high VEGF expression was shorter compared with that for patients with low VEGF expression (9.5 months vs. 26.4 months, respectively; P = 0.002). Cox regression model analysis indicated that only the VEGF status was a significant factor for prognosis (P = 0.024). Other variables, i.e., K-ras status, histopathologic tumor grade, tumor status, lymph node status, metastatic status, gender, and age at surgery, were not significant. CONCLUSIONS The results of this study suggest that K-ras oncogene mutation may be associated with VEGF expression and that patients with pancreatic carcinoma who have high VEGF expression are associated with a poor prognosis. Cancer 2001;92:488–99. © 2001 American Cancer Society.

高齢人口の増加とともに大腸癌手術症例のうち高齢者の占める割合は増加の一途をたどり,当科では高齢者 (75歳以上)は20%を越えた.そこで高齢群(75歳以上)(240例) と非高齢群(41～50歳)(155例)を臨床病理学的に比較し高齢者の特徴を検討した.他病死を含めた累積生存率は高齢群で不良であった.術後早期死亡例の検討では高齢群といえども非高齢群と変わらず安全に手術が行われていた.両群間の腹膜播種,肝転移,リンパ節転移,壁深達度には有意差はみられず高齢者に進行例が多いとはいえなかった.組織学的分化度の検討では高齢群は高分化型が多いという傾向はみられず,一般的に高齢者癌は悪性度が低いという印象があるが,大腸癌にっいては非高齢者と変わらなかった.腫瘍占居部位は高齢群女性で右側結腸に発生する頻度が高かった.死因では他病死の占める割合が多く,併存疾患,余命を考慮した手術が行われるべきである.

The expression of vascular endothelial growth factor (VEGF) and its receptors (VEGFRs), VEGFR-1/Flt-1 and VEGFR-2/Flk-1, was investigated by immunohistochemical and northern blot analysis during lung carcinogenesis by N-nitrosobis(2-hydroxypropyl)amine (BHP) in male Wistar rats. After BHP was given in the drinking water for 12 wk, the rats were maintained without further treatment until they were killed at 20–28 wk. Immunohistochemical studies revealed VEGF expression in almost all malignancies, the reaction being strongly positive in most adenocarcinomas (15 of 18; 83.3%) and squamous cell carcinomas (four of five; 80.0%), but less so in a total of 120 adenomas and 136 alveolar hyperplasias. In addition, VEGF mRNA and VEGFR mRNAs were found to be overexpressed in most adenocarcinomas and squamous cell carcinomas as well as in one to three of the five adenomas tested. The results indicated that VEGF and VEGFRs play important roles in the acquisition of malignant potential by preneoplastic lung lesions induced by BHP in rats. Moreover, overexpression of VEGF was related to upregulation of VEGFR-1/Flt-1 and VEGFR-2/Flk-1 expression in malignant and premalignant lung lesions. Mol. Carcinog. 24:287–293, 1999. © 1999 Wiley-Liss, Inc.

The expression of midkine (MK) in lung tumors induced by N-nitrosobis(2-hydroxypropyl)amine (BHP) in rats was examined. The animals were administered 2000 p.p.m. of BHP in their drinking water for 12 weeks, then maintained without further treatment until being killed 20-28 weeks after the beginning of the experiment. MK mRNA expression of adenocarcinomas and squamous cell carcinomas assessed by means of the reverse transcriptase-polymerase chain reaction and northern blot analysis was significantly higher than in rat embryonic tissues (positive controls) and contrasted strongly with the lack in normal lungs. MK protein was detected immunohistochemically in 58.3% of alveolar hyperplasias, 92.3% of adenomas and 100% of adenocarcinomas and squamous cell carcinomas. The extent of staining significantly increased along with malignant progression in adenomatous (pre-)neoplastic lesions and tended to become more pronounced with malignant progression in squamous lesions. The results suggest that MK may play some essential roles in the development and progression of lung tumors induced by BHP in rats.

In the present experiment, we examined the effects of OPB‐3206, 3S‐[4‐(N‐hydroxyamino)‐2R isobutylsuccinyl] amino‐1‐methoxy‐3,4‐dihydrocarbostyril, a novel metalloproteinase inhibitor, on the growth and metastasis of transplantable osteosarcomas (spontaneous osteosarcoma, selected lung metastatic lesions; S‐SLM), which were previously established in rats. OPB‐3206 inhibited the activities of interstitial collagenase, gelatinases A and B, and stromelysin in vitro. After oral administration to rats, its serum concentration peaked at 40 min and the drug was no longer detectable at 8 h. When OPB‐3206 was orally administered at 0%, 0.1% and 0.4% in the diet for 4 weeks, starting 7 days after subcutaneous transplantation of osteosarcomas to male Fischer 344 rats, numbers of lung metastatic nodules were significantly reduced by the highest dose, while the growth of subcutaneous tumors was not affected. Zymographic analysis showed the presence of pro matrix metalloproteinase (proMMP)‐2, proMMP‐9 and MMP‐9 activities in S‐SLM. In animals fed 0.4% OPB‐3206, the activity of proMMP‐9 was increased, but that for MMP‐9 had become undetectable. The results thus suggest that OPB‐3206 selectively inhibits lung metastasis of rat transplantable osteosarcomas by inhibiting MMP‐9 activation.

Telomerase activities in intrahepatic cholangiocarcinomas induced by N-nitrosobis(2-oxopropyl)amine (BOP) in female hamsters were determined using a telomeric repeat amplification protocol (TRAP) assay followed by densitometric quantification. Each determination was repeated to confirm the results and telomerase activity was also detected by gel electrophoresis. An increase was evident in all of 10 cholangiocarcinomas examined, with levels ranging from 2.48 to 4.40 times the normal liver value by densitometric quantification. This finding of a consistent increase suggests that telomerase activation is involved in the development of intrahepatic cholangiocarcinomas and immortalization of cancer cells.

We experienced a rare case of malignant melanoma metastasized to the small intestine. A 59-year-old man, who had been diagnosed as having a malignant melanoma of the nasal cavity two years earlier, had been admitted to the Department of Otorhinolaryngology in our hospital several times for anticancer drug treatment. On November 6, 1994, he was seen at the Department of Surgey in the hospital because of upper abdominal pain. He had a protuberant tense abdomen with slight tenderness and bilateral nasal bleeding with anemia. Plain abdominal roentgenograms showed multiple, small fluid levels of the small bowel. These findings were suggestive of obstruction of the small intestine. Nasogastric long tube suction was continued and intravenous hyperalimentation was given. After relief of the intestinal obstruction, an abdominal firm mass was palpated and a barium meal study demonstrated a filling defect in the ileum. The preoperative diagnosis was made as metastatic malignant melanoma to the ileum. At operation, endoscopic examination of the small intestine showed a 3.0×3.0 cm nodular mass in the ileum with no other lesions. Partial resection of the ileum with the tumor was performed. Macroscopic examination of the resected specimen revealed a brown nodular mass with an ulcer, 2.5×2.5 cm in size, which occupied most of the intestinal wall area. In immunohistological stainig, S-100 antibody was positive. The histological diagnosis was thus established as metastatic malignant melanoma to the ileum. The patient was discharged on the 14th day after the surgery following an uneventful postoperative course. However, he died of metastatic lung cancer with no abdominal complaints one year after the operation.

To understand the role of islet amyloid polypeptide (IAPP) in type 2 diabetes and pancreatic cancer (PC), we investigated the patterns of its expression and its ratio to insulin, glucagon, somatostatin and pancreatic polypeptide cells by morphometry in tissues from these two diseases in comparison to the normal pancreas.Pancreatic tissues from 11 donors (five without pancreatic disease and six with type 2 diabetes) and 11 surgical specimens from PC patients obtained from the cancer area (zone A) and the adjacent tumor-free area (zone B) were examined immunohistochemically. The size of islets, the number on beta-, alpha-, delta- pp- and IAPP-expressing cells and their ratios in the islets of these tissues were determined.In the normal pancreas, only 50% of the beta-cells while alpha- and delta-cells co-expressed IAPP only sporadically. In tissues from diabetics as well as in zone A, the number of the beta-cells and the IAPP-expressing cells was reduced significantly, while the number of alpha- and delta-cells was increased. In zone B, however, significantly more beta-cell and IAPP-expressing cells and a significantly lower number of alpha-cells were found compared to those in zone A. Significant differences were also found between the specimens from type 2 diabetics and pancreatic cancer relative to the ratios of IAPP/beta-cell, IAPP/alpha-cells and beta-cell/delta-cells.The morphometric data show a decrease rather than an increase in the number of IAPP-expressing cells in PC. Differences in abnormalities in type-2 diabetics and in zone B of PC tissue strongly argue against the role of type 2 diabetes in PC. Rather, the development of diabetes in subjects prone to pancreatic cancer could be a red flag for malignancy.

Hepaticarterial infusional(HAI)5-FU chemotherapy, which involves the use of interventional radiology technique, has matured technically in Japan in the 1990's. The antitumor effect of 5-FU is enhanced by combination with leucovorin. This study was performed to evaluate the efficacy and toxicity of HAI 5-FU and leucovorin chemotherapy for patients with unresectable liver metastases from colorectal cancer.Treatment was given to 20 patients with unresectable liver metastases from colorectal cancer. The chemotherapy regimen consisted of weekly HAI of 5-FU(1,000 mg/body)and leucovorin(250 mg/body)over five hours. The survival and response rates to the therapy were assessed according to RECIST. Hematologic and non-hematologic toxicity was assessed according to CTCAE v3.0.Combined HAI 5-FU and leucovorin therapy was carried out an average of 27 times. The response rate for liver tumors was 75%, and the median survival time was 22 months. The applied regimen caused only mild adverse events. There was no evidence of myelosuppression except for platelet decrease(grade 3)in a patient with chronic renal failure.This HAI approach using 5-FU and leucovorin was effective and the therapy for unresectable liver metastases from colorectal cancer was tolerated well. Therefore the HAI approach should be reconsidered as an effective therapy against this disease in Japan.

There is a lack of agreement on the distribution of islet amyloid polypeptide (IAPP) in the pancreases of healthy and diabetic subjects. Therefore, a detailed morphometrical and immunohistochemical study was performed to obtain information on the distribution of cells expressing insulin, glucagon, somatostatin, pancreatic polypeptide (PP), and IAPP in the pancreases of non-diabetic (n=4) and diabetic individuals (n=6). In the non-diabetic cases, beta-cells contributed to approximately 64%, alpha-cells to 26%, delta-cells to 8%, PP cells to 0.3%, and IAPP cells to 34% of the islet cell population. The ratio of IAPP/insulin was approximately 1:2. In diabetic cases, beta-cells were decreased by 24%, and IAPP was decreased by 57%. The alpha- and delta-cells were increased by 40% and 58%, respectively. IAPP/insulin ratio was decreased by 41%. Thus, only 50% of the beta-cells in non-diabetics and only 30% in diabetics coexpressed IAPP. In diabetics, more delta-cells coexpressed IAPP than in non-diabetics. The results seem to argue against the notion that the secretion of IAPP is increased in diabetics. It is possible that an increase in somatostatin and glucagon plays a greater role in diabetes than IAPP.

Proximal gastrectomy and lymph node dissection are often performed for T1 cancer of the gastric cardia; however, direct esophagogastrostomy is frequently complicated by reflux esophagitis. We describe a simple technique for preventing esophageal reflux and discuss its results.This technique is indicated for T1 cancer of the gastric cardia without lymphadenopathy. Partial resection, including the lesion, is performed, preserving the vagus nerve and lower esophageal sphincter (LES). Lymph node dissection is done around the left gastric, celiac, and splenic arteries. The esophagus is then anastomosed to the anterior wall in the center of the remnant stomach.We evaluated the results of this procedure in eight patients. X-ray films showed no esophageal reflux in either the supine or the right decubitus position. None of the patients complained of reflux or other dyscrasic symptoms, and none had any feeling of microgastria. One patient had some localized erosion near the anastomosis.This simple and safe technique does not result in post-gastrectomy syndrome or microgastria, and the risk of leaving cancer cells is minimal.

We investigated the relationship between surgical stress and tumor metastasis. The excessive surgical stress of a thoracolaparotomy enhanced tumor metastasis remarkably in an experimental model. We would like to propose that this phenomenon be termed "surgical oncotaxis". This effect has previously been attributed to some mechanisms of immunosuppression, excessive secretion of corticoids, and active oxygen production of granulocytes. An increase in lipid peroxide (LPO) in the liver was observed after a thoracolaparotomy, but a strong radical scavenger of a DL-alpha-tocopherol-L-ascorbic acid 2-0-phosphate diester (EPC-K1) restrained LPO levels in the liver and the effect of tumor metastasis in parallel. As clinical strategies for restraining the surgical oncotaxis, the control of any cytokine storm after surgery and/or the scavenging of active oxygen appears to be possible and hopeful, since it might be intermediated by cytokine. When pre-administration findings for EPC-K1 and methylpredonisolone were compared, EPC-K1 was found to be more suitable for restraining surgical oncotaxis, because serum LPO was only controlled with EPC-K1. The cytokine storm which occurs after surgery is augmented by a second stimulation, such as the administration of lipopolysaccharide, and no drug could control this well experimentally. Postoperative complications are a clinical model of a second stimulation (a so-called second attack). Our data showed the prognosis of a group with complications to be worse than that of a group without them even though no difference existed in the background of the esophageal cancer patients studied. Based on these results, safe surgery and the choice of minimally invasive surgery are the best ways to control surgical oncotaxis. Following a major surgical procedure, such as a thoracolaparotomy, the use of corticoids and/or radical scavengers can contribute to restraining surgical oncotaxis.

Fluorouracil-based chemotherapy, such as that with 5-fluorouracil (5-FU)/leucovorin, is standard as first-line chemotherapy for advanced colorectal cancer (CRC) in Japan. However, the best agent for second-line chemotherapy after fluorouracil failure is yet to be determined. This study was undertaken to find an appropriate agent for second-line chemotherapy. Seventy-five tumor specimens from CRC patients with no prior chemotherapy were obtained operatively and their chemosensitivity to five anticancer agents; i.e., 5-FU, mitomycin C (MMC), cisplatin, docetaxel, and an active metabolite of irinotecan (SN-38), was analyzed in an in vitro chemosensitivity test. In this method, the degree of chemosensitivity was expressed as the percent T/C ratio, where T was the total volume of the tumor colonies in the treated group and C was that of the control group. Pearson's correlation coefficients were used to assess the relationship between two agents. Fifty-eight specimens (colon, 28; rectum, 30) were successfully analyzed. Positive correlations with 5-FU chemosensitivity were verified for the chemosensitivity of MMC, cisplatin, and docetaxel. No correlation with 5-FU chemosensitivity was verified for SN-38 chemosensitivity. Although the functional mechanism of each of the agents differs from that of 5-FU, with the exception of irinotecan, they all had a spectrum closely similar to the 5-FU spectrum. Only irinotecan exhibited a spectrum independent of that of 5-FU, thus indicating that it could be an appropriate agent for second-line chemotherapy after fluorouracil failure.

Matrix metalloproteinases (MMPs) have been implicated as playing an important role in cancer invasion and metastasis. MMPs have been identified in various malignancies, including pancreatic duct adenocarcinomas.We investigated the circulating level of MMP-2 and MMP-9 in sera from Syrian golden hamsters into which hamster pancreatic duct adenocarcinoma tissues had been transplanted subcutaneously (HPDt hamsters). Northern blot analysis and gelatin zymographic analysis were performed to detect the expression of MMPs and that of tissue inhibitors of metalloproteinases (TIMPs) in HPDt hamsters.Northern analysis revealed overexpression of MMP-2, MMP-9, and TIMP-2 mRNAs in subcutaneous tumors of HPDt hamsters as compared with normal pancreatic tissue. Sera from HPDt hamsters possessed significantly higher levels of serum MMP-2 and MMP-9 than control sera, as determined by gelatin zymographic analysis, and there was a significant correlation between tumor growth and serum MMP levels.These results indicate that overexpression of MMP mRNAs is involved in the progression of pancreatic duct adenocarcinomas, and that MMP protein expression in hamster sera is associated with the presence of pancreatic duct adenocarcinoma cells. The findings also suggest that serum MMPs could be useful markers for monitoring patients with pancreatic duct adenocarcinomas.

Effects of eight heterocyclic amines (HCAs) on pancreatic duct carcinogenesis were investigated in a rapid production model in hamsters. N-Nitrosobis(2-oxopropyl)amine (BOP) was given to effect initiation, followed by augmentation pressure consisting of four daily i.p. injections of 500 mg/kg DL-ethionine, a choline-deficient (CD) diet, a single i.p. injection of 800 mg/kg L-methionine and a s.c. injection of 20 mg/kg BOP. After two cycles of augmentation pressure, the HCAs 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP), 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline (MeIQx), 2-amino-3-methylimidazo[4,5-f]quinoline (IQ), 3-amino-1,4-dimethyl-5H-pyrido[4,3-b]indole (Trp-P-1), 3-amino-1-methyl-5H-pyrido[4,3-b]indole (Trp-P-2), 2-amino-9H-pyrido[2,3-b]indole (AalphaC), 2-amino-3-methyl-9H-pyrido[2,3-b]indole (MeAalphaC) or 2-amino-3,4,8-trimethylimidazo[4,5-f]quinoxaline [4,8-DiMeIQx) were administered in the diet for 50 or 70 days. The numbers of pancreatic ductal hyperplasias (H) and a total lesions including, atypical hyperplasia (AH), carcinomas in situ (CIS) and invasive carcinomas, were increased in hamsters given the diet containing 0.02% Trp-P-1 for 50 days. This result was confirmed and extended by the finding of increased numbers of invasive carcinomas in hamsters given 0.02% Trp-P-1 for 70 days. The number and incidence of invasive carcinomas were also elevated in hamsters given the diet containing 0.06% 4,8-DiMeIQx for 50 days. These results suggest a possible involvement of Trp-P-1 and 4,8-DiMeIQx in pancreatic duct carcinogenesis.

In order to assess the significance of changes in metalloproteinase activity in pancreatic carcinogenesis, the expression of matrix metalloproteinases 2 and 9 (MMP-2 and MMP-9, respectively), tissue inhibitor of metalloproteinase-1 (TIMP-1) and TIMP-2, and membrane-type 1 MMP (MT1-MMP) and MT2-MMP in ductal lesions in a rapid-production model for pancreatic duct carcinomas (PCs) in hamsters initiated with N-nitrosobis(2-oxopropyl)amine (BOP) and in subcutaneous transplantable tumors of hamster pancreatic duct carcinoma (HPDs) was investigated. Northern analysis revealed MMP-2, MMP-9, TIMP-2 and MT1-MMP mRNAs to be overexpressed in PCs. Immunohistochemically, elevated levels of MMP-2 were apparent in early duct epithelial hyperplasias and staining increased from atypical hyperplasias to carcinomas. Gelatin zymography demonstrated clear activation of proMMP-2 but not proMMP-9 in both of primary and HPD tumors, the MT1-MMP mRNA level and proMMP-2 activation being significantly correlated (r = 0.893, P < 0.001). In our rapid production model, 0.1 and 0.2% OPB-3206, an inhibitor of MMPs, given in the diet after two cycles of augmentation pressures for 48 days decreased the incidence and number of carcinomas. Gelatin zymography demonstrated that OPB-3206 inhibited activation of proMMP-2 in pancreatic cancer tissues. These results indicate that overexpression of MMP-2, TIMP-2 and MT1-MMP, and cell surface activation of proMMP-2 by MT1-MMP, are involved in the development of PCs, and that MMP-2 expression at the protein level appears in the early phase of pancreatic duct carcinogenesis. OPB-3206 may be a candidate chemopreventive agent for pancreatic ductal adenocarcinomas.

To determine the tumor size that constitutes early pancreatic cancer, we reviewed and analyzed the English-language and Japanese literature (a total of 25 publications) on small pancreatic cancers less than 2 cm in diameter and/or stage 1 cancers. Reports on in situ carcinoma and intraductal carcinoma of the pancreas were also evaluated. The results were: (1) A total of 302 cases of small pancreatic cancer less than 2 cm in diameter reported at separate institutions were pooled from 15 reports. The rates for patients in stage I and those with no lymph node metastasis averaged 41.7% and 57.9%, respectively. The 5-year postoperative cumulative survival rate (5Y-PCR) was less than 50% in almost all these reports. Similar data were shown in the 7 collective reviews. (2) Another 33 cases of small pancreatic cancer of 1 cm or less in diameter were collected from three reports. The rates for stage I tumor and 5Y-PCR at one institution with two reports were 100% and 100% and the rates in the other report were 85% and 78%, respectively. (3) Twelve cases of in situ carcinoma and intraductal carcinoma of the pancreas were collected from four reports. All of the patients were stage I and were alive with no evidence of tumor recurrence for periods ranging from 6 to 78 months. Small pancreatic cancer less than 1 cm in diameter is better viewed as an early pancreatic cancer, and in situ carcinoma and intraductal carcinoma of the pancreas with minimal invasion to the pancreatic parenchyma may be defined as early pancreatic cancer, regardless of size.

The question of whether the changes in telomerase activity and/or the alteration of the p53 gene are involved in the development of oligo-astrocytomas induced by N-ethyl-N-nitrosourea (ENU) in rats was addressed. Telomerase activity levels of oligo-astrocytomas, including early neoplastic lesions, were significantly increased as compared to the normal controls, correlating with the degree of malignancy. In contrast, no mutations of p53 exons 5-7 were found in early neoplastic lesions or oligo-astrocytomas. These results indicate that the activation of telomerase occurs during astrocytoma carcinogenesis and contributes to the development of brain tumors, but the alterations of p53, at least on exons 5-7, may not be involved in this process.

The regulation of telomerase activity during regeneration induced by two-thirds partial hepatectomy (PH) was investigated in 6-week-old male F344 rats. Groups of animals were serially sacrificed 0, 6, 16, 24, 36 and 72 h after the operation and telomerase activity was determined by the telomeric repeat amplification protocol (TRAP) assay followed by densitometric quantification. DNA synthesis was immunohistochemically quantified in terms of bromodeoxyuridine (BrdU) incorporation. The expression levels of telomerase RNA were examined by Northern blot analysis. Telomerase activity was increased significantly from 6 to 36 h but had decreased to close to the normal levels after 72 h. DNA synthesis reached a maximum 24 h after PH. However, the expression levels of telomerase RNA did not change during regeneration. The results suggest that telomerase is actively regulated by unknown mechanisms throughout the cell cycle in regenerating rat hepatocytes.