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D S Longnecker

Publications and source records attributed to D S Longnecker.

At least 37 records · Page 2Linked to original sources
PubMed1995

Pancreatoblastoma in an older adult.

We present a case of pancreatoblastoma in a 61-year-old man. To our knowledge, this is the oldest patient with this tumor to be reported. Originally regarded as a microadenocarcinoma, the tumor was composed of small cells, sometimes in acinar groups with clusters of squamoid cells. It also showed acinar and neuroendocrine features by immunohistochemistry. Staining for trypsin and several neuroendocrine markers was widespread and intense in the smaller, majority-type cells. There was faint staining for some neuroendocrine markers in the larger squamoid cells. By electron microscopy both exocrine secretory and neurosecretory dense core granules were found. Modern methods of immunohistochemistry and greater understanding of rare tumor types allowed reclassification of this tumor.

DNA, Neoplasm↗
PubMed1994

Only wild-type c-Ki-ras codons 12, 13, and 61 in human pancreatic acinar cell carcinomas.

Activation of the c-Ki-ras proto-oncogene is more common in carcinomas of the pancreas than in other human carcinomas. Most such carcinomas are of the ductal cell phenotype. Ductal adenocarcinomas of the hamster pancreas have similar mutations, but acinar cell carcinomas of the mouse and rat pancreas lack the common c-Ki-ras mutations. Therefore, we examined 11 acinar cell carcinomas of the human pancreas for evidence of mutations at codons 12, 13, and 61. DNA was isolated from tumor cells in paraffin-embedded sections. The polymerase chain reaction was used to amplify the appropriate DNA sequence, and then allele-specific oligonucleotide hybridization and DNA sequence analysis were used to evaluate c-Ki-ras structure. Only wild-type sequences were found in codons 12, 13, and 61. Thus, in both the human and rodent species, mutations of c-Ki-ras appear to be more important in the genesis of ductal carcinomas than in the genesis of acinar cell carcinomas of the pancreas.

Alleles↗
PubMed1994

Novel expression of gastrin (CCK-B) receptors in pancreatic carcinomas and dysplastic pancreas from transgenic mice.

Transgenic mice bearing the elastase I promoter--SV40 T-antigen fusion gene (ELSV) develop pancreatic acinar cell carcinomas by 3 to 6 months of age. The purpose of the study was to determine if pancreatic carcinomas and dysplastic pancreas from the Tg (Ela-1, SV40E + Ela-1, neo) Bri19 strain of ELSV transgenic mice express gastrin (CCK-B) receptors. To accomplish this, we utilized iodine 125 (125I)-gastrin binding studies, reverse transcription-polymerase chain reaction (RT-PCR), and Southern blot analysis to examine pancreatic carcinomas from 26-week-old male ELSV transgenic mice, dysplastic pancreas from 8-week-old male ELSV transgenic mice, and normal pancreas from 30-week-old nontransgenic male mice (SJL/J) and from 8-week-old nontransgenic male mice (B6SJLF1/J). No saturable gastrin binding to normal nontransgenic mouse pancreas was found. In contrast, saturable gastrin binding was detected at pH 6.5, 22 degrees C, in 9 of 13 pancreatic carcinomas and all 5 dysplastic pancreata. Competitive inhibition 125I-gastrin binding assays showed gastrin bound to a single class of high-affinity receptors (receptor binding affinity [Kd] 0.11 +/- 0.02 nM, binding capacities ranging from 1 to 60 fmol/mg protein for pancreatic carcinomas; Kd: 0.15 +/- 0.04 nM, binding capacities ranging from 1 to 9 fmol/mg protein for dysplastic pancreas). RT-PCR and Southern blot analysis confirmed 125I-gastrin binding studies by demonstrating gastrin (CCK-B) receptor mRNA expression in pancreatic carcinomas and dysplastic pancreas but an absence of mRNA expression in normal nontransgenic mouse pancreas. In conclusion, pancreatic carcinomas and dysplastic pancreas in ELSV transgenic mice novelly express gastrin (CCK-B) receptors. This expression may provide a growth advantage to acinar cells as part of the multistage process of carcinogenesis.

Animals↗
PubMed1994

Stimulation of in vivo pancreatic growth in the rat is mediated specifically by way of cholecystokinin-A receptors.

BACKGROUND/AIMS: Cholecystokinin (CCK) and gastrin stimulate growth of rodent pancreas in vivo. However, it remains unclear whether these growth effects are mediated specifically by CCK-A receptors, CCK-B receptors, or both. To clarify this issue, the present study examined the effect of highly selective and biologically active CCK agonists on pancreatic growth. METHODS: Rats were subcutaneously injected with either (1) CCK-8, a nonselective CCK agonist (2.50 micrograms/kg body wt); (2) A-71623, a selective CCK-A agonist, tert-butyl-oxycarbonyl-Trp-Lys (epsilon-N-2-methylphenylaminocarbonyl)-Asp-(N-methyl)-Phe-NH2 (1.84 micrograms/kg body wt); (3) SNF-8815; a selective CCK-B agonist, [(2R,3S)-beta-MePhe28, N-MeNle31]CCK26-33 (2.40 micrograms/kg body wt); or (4) saline (control) for 21 days. Rats were killed, and pancreatic weight, protein content, RNA content, DNA content, protein-DNA ratio, RNA-DNA ratio, pancreatic area per nucleus, and number of mitoses per 10,000 acinar cells were determined. RESULTS: Nonselective CCK agonist significantly increased pancreatic weight, protein, RNA, and DNA contents, and number of mitoses per 10,000 acinar cells. Likewise, selective CCK-A agonist significantly increased pancreatic weight, protein, RNA, and DNA contents, protein-DNA ratio, RNA-DNA ratio, pancreatic area per nucleus, and number of mitoses per 10,000 acinar cells. In contrast, selective and biologically active CCK-B agonist had no effect. CONCLUSION: These findings indicate that pancreatic growth is mediated specifically by CCK-A receptors in the rat in vivo.

Animals↗
PubMed1994

Cell lines derived from pancreatic tumors of Tg(Ela-1-SV40E)Bri18 transgenic mice express somatostatin and T antigen.

Continuous cell lines have been isolated from islet cell, small cell anaplastic and acinar cell carcinomas arising in the pancreas of transgenic mice, line Tg(Ela-1-SV40E)Bri18. These mice carry the pseudogene construct composed of elastase-1 promoter linked to the SV40 T antigen. Cells derived from islet cell or small cell anaplastic tumors secreted insulin and somatostatin during the early period of culture. Phenotypic alterations occurred during culture, whereby insulin secretion ceased and cells instead secreted somatostatin, indicating a change from beta-cell to delta-cell phenotype. Acinar cell lines did not secrete amylase or lipase.

Adenoma, Islet Cell↗
PubMed1994

Mutated c-K-ras in small pancreatic adenocarcinomas.

The objective of this study was to determine whether small human pancreatic adenocarcinomas contain activated c-K-ras as an approach to answering the question of whether c-K-ras mutation is an early change in this disease. Eight pancreatic adenocarcinomas in the range 1.2-3 cm were analyzed for c-K-ras mutation at codon 12 by amplifying the c-K-ras gene around codon 12 out of paraffin-embedded tissue sections using the polymerase chain reaction. c-K-ras mutations were detected by allele-specific oligonucleotide hybridization. Six of the eight small pancreatic adenocarcinomas contained mutated c-K-ras at codon 12, position 2, and two of the six tumors had an additional mutation at position 1 of codon 12. Our results indicate that small pancreatic adenocarcinomas are similar to large, late-stage pancreatic adenocarcinomas in that 75% of the tumors analyzed contain mutated c-K-ras at codon 12, position 2. These data suggest that c-K-ras mutation occurs early and may therefore have a role in initiation of human pancreatic adenocarcinoma.

Adenocarcinoma↗
PubMed1994

Cholecystokinin receptor characterization and cholecystokinin-A receptor messenger RNA expression in transgenic mouse pancreatic carcinomas and dysplastic pancreas.

Transgenic mice bearing the rat elastase I promoter - SV40 T-antigen (ELSV) fusion gene develop pancreatic acinar cell carcinomas by 3-6 months of age. In other animal models of pancreatic cancer, cholecystokinin (CCK) has been shown to be a tumor promoter. Therefore, we characterized CCK binding properties and CCK-A receptor mRNA expression in pancreatic carcinomas and dysplastic pancreata from the Tg(Ela-1, SV40E+Ela-1, neo)Bri19 strain of ELSV transgenic mice. To accomplish this, we utilized 125I-Bolton-Hunter-labeled-cholecystokinin octapeptide (125I-BH-CCK-8) binding studies, reverse transcription-polymerase chain reaction (RT-PCR), and Southern blot analysis to examine pancreatic carcinomas from 26-week-old male ELSV transgenic mice, dysplastic pancreata from 8-week-old male ELSV transgenic mice, and normal pancreas from 30-week-old nontransgenic male mice (SJL/J) and 8-week-old nontransgenic male mice (B6SJLF1/J). Optimal saturable CCK-8 binding was detected at pH 6.5, 22 degrees C. Competitive inhibition 125I-BH-CCK-8 binding assays performed on all four mouse pancreatic tissues showed that CCK-8 bound to two classes of CCK binding sites: a high affinity, lower capacity CCK binding site and a low affinity, higher capacity CCK binding site. RT-PCR and Southern blot analysis confirmed the 125I-BH-CCK-8 binding studies by demonstrating CCK-A receptor mRNA expression in the ELSV transgenic pancreatic carcinomas and dysplastic pancreas, as well as in normal nontransgenic mouse pancreas. In conclusion, pancreatic carcinomas and dysplastic pancreas from ELSV transgenic mice and normal nontransgenic mouse pancreas all bind 125I-BH-CCK-8 and express mRNA for the CCK-A receptor. In contrast to chemically-induced pancreatic tumors in the rat, ELSV transgenic mouse pancreatic tumors do not appear to significantly overexpress CCK-A receptors.

Animals↗
PubMed1994

Pancreatic carcinomas of acinar and mixed acinar/ductal phenotypes in Ela-1-myc transgenic mice do not contain c-K-ras mutations.

c-K-ras is activated by mutation at codon 12 in the majority of human pancreatic carcinomas of ductal but not acinar phenotype. The Ela-1-myc transgene when expressed in transgenic mice induces pancreatic carcinomas of both acinar and mixed acinar/ductal phenotype. The histopathology of 110 pancreatic carcinomas were characterized in this model. A high percentage of the low to moderately differentiated acinar cell carcinomas contain areas of ductal metaplasia. The latter tumors and several well-differentiated acinar tumors were evaluated for c-K-ras mutation to determine whether there is a relationship between the ductal phenotype and c-K-ras mutation. The polymerase chain reaction and allele-specific oligomer hybridization were used to determine whether the c-K-ras gene was mutated at codons 12, 13, or 61. Amplified DNA products from these tumors were also evaluated by single strand conformation polymorphism analysis. Only wild-type c-K-ras was found in these tissues. Not finding c-K-ras mutation in tumors containing ductal morphology indicates that c-K-ras mutation is not a required factor for acinar to ductal metaplasia or a factor in the tumorigenesis of pancreatic tumors that arise in acinar tissue.

Animals↗
PubMed1993

Stimulation of growth of azaserine-induced putative preneoplastic lesions in rat pancreas is mediated specifically by way of cholecystokinin-A receptors.

Cholecystokinin (CCK) has been shown to stimulate the growth of both normal pancreas and azaserine-induced putative preneoplastic pancreatic lesions in the rat. The present study was performed to determine whether these effects are mediated by way of CCK-A receptors, CCK-B receptors, or both. Sixteen-day-old male Lewis rats were given i.p. injections of azaserine at 30 mg/kg body weight. Starting on day 21, rats were given s.c. injections, 5 days/week for 16 consecutive weeks, of either (a) CCK octapeptide (nonselective CCK agonist) (2.50 micrograms/kg body weight, n = 17), (b) tert-butyloxycarbonyl-Trp-Lys(epsilon-N-2-methylphenylaminocarbonyl++ +)-Asp- (N-methyl)-Phe-NH2 (highly selective CCK-A agonist) (1.84 micrograms/kg body weight, n = 18), (c) [(2R,3S)-beta-MePhe28,N-MeNle31]CCK26-33 (highly selective CCK-B agonist) (2.40 micrograms/kg body weight, n = 18), or (d) normal saline solution (control, n = 17). Rats were subsequently sacrificed, pancreatic weights were determined, and quantitative morphometric analysis of atypical acinar cell foci and nodules was performed. Both CCK octapeptide and the selective CCK-A agonist tert-butyloxycarbonyl-Trp-Lys(epsilon-N-2- methylphenylaminocarbonyl)-Asp-(N-methyl)-Phe-NH2 stimulated pancreatic growth and the development of acidophilic atypical acinar cell foci and nodules. Furthermore, the effect produced by the selective CCK-A agonist tert-butyloxycarbonyl-Trp-Lys(epsilon-N-2- methylphenylaminocarbonyl)-Asp-(N-methyl)-Phe-NH2 was greater than that produced by CCK octapeptide. In contrast, the selective CCK-B agonist [(2R,3S)-beta-MePhe28,N-MeNle31]CCK26-33 had no effect. These findings suggest that the growth of putative preneoplastic lesions (acidophilic atypical acinar cell foci and nodules) in the rat pancreas during the early stages of azaserine-induced pancreatic carcinogenesis is mediated specifically by way of CCK-A receptors.

Animals↗
PubMed1993

Evaluation of c-K-ras in pancreatic carcinomas from Ela-1, SV40E transgenic mice.

c-K-ras is activated by mutation at codon 12 in the majority of human pancreatic carcinomas of ductal, but not acinar, phenotype. Therefore, evaluation of c-K-ras in experimentally induced pancreatic carcinomas in animal models is of interest for comparison with the human disease. Acinar cell carcinomas and islet cell tumors arising in two strains of transgenic mice carrying the Ela-1-SV40E transgene were evaluated using the polymerase chain reaction and allele specific oligomer hybridization to seek evidence of c-K-ras mutation at codons 12, 13 and 61. Amplified DNA products, including codons 12 and 13, from the majority of these tumors were also evaluated by single strand conformation polymorphism analysis. Only wild type c-K-ras was found in the tumors.

Animals↗
PubMed1993

Temporal expression of the gastrin (CCK-B) receptor during azaserine-induced pancreatic carcinogenesis.

Cholecystokinin (CCK-A) and gastrin (CCK-B) receptors have been demonstrated in the azaserine-induced rat pancreatic carcinoma DSL-6. In order to determine at what stage in azaserine-induced pancreatic carcinogenesis gastrin (CCK-B) receptors are first expressed, we examined the binding of [125I]gastrin-I to normal rat pancreas, azaserine-induced premalignant pancreatic nodules, grossly normal internodular pancreas, and DSL-6 carcinoma. We observed that specific gastrin binding was absent in normal pancreas, premalignant nodules, and internodular pancreas, and also reconfirmed our previous report of marked overexpression of gastrin (CCK-B) receptors in the DSL-6 carcinoma. Specific cholecystokinin (CCK) binding was present in all pancreatic tissue types tested. Therefore, we conclude that the presence of gastrin (CCK-B) receptors in the azaserine-induced pancreatic carcinoma DSL-6, in contrast to their absence in premalignant nodules, suggests that the expression of the gastrin (CCK-B) receptor may be important in the transformation from premalignant nodules to pancreatic cancer.

Animals↗
PubMed1993

Derivation of ductlike cell lines from a transplantable acinar cell carcinoma of the rat pancreas.

Two cell lines were derived from a transplantable acinar cell carcinoma that had been established from a primary carcinoma of the pancreas in an azaserine-treated Lewis rat. The cultured tumor cells initially produced amylase, but production of exocrine enzymes ceased after 1-2 weeks in culture. The cultured cells were tumorigenic in Lewis rats, and one line produced solid tumors composed of ductlike structures surrounded by dense fibrous tissue. The second cell line produced partially solid and partially cystic tumors with a mixed phenotype of squamous, mucinous, and glandular areas when it grew in vivo following regrafting. Both cell lines lost structural and immunohistochemical acinar cell markers while acquiring duct cell markers during culture and regrafting. These studies provide strong support for the hypothesis that ductlike carcinomas can arise from neoplastic pancreatic acinar cells in rats.

Animals↗
PubMed1992

Novel expression of gastrin (cholecystokinin-B) receptors in azaserine-induced rat pancreatic carcinoma: receptor determination and characterization.

Many reports have emphasized the role of gastrin as a growth factor for normal gastrointestinal mucosa and gastrointestinal cancers. Recent studies have pointed out that this peptide acts also as a growth factor for the pancreatic cancer cell line AR42J. This effect is mediated by gastrin [cholecystokinin (CCK)-B] receptors. In the present study, we investigated gastrin (CCK-B) receptor expression in the azaserine-induced rat pancreatic carcinoma DSL-6, comparing it to normal rat pancreas, and we also characterized CCK receptor subtypes in this tumor. The results showed that there is extensive gastrin binding to the DSL-6 pancreatic carcinoma. No evidence of specific gastrin binding to normal pancreas was found. Analysis of the ability of gastrin-17-I to inhibit 125I-gastrin-I binding demonstrated that gastrin bound to a single class of receptors with a Kd of 0.21 +/- 0.04 nM and a binding capacity of 184 +/- 29 fmol/mg protein. 125I-Gastrin-I binding was inhibited by the specific CCK-B receptor antagonist L365,260 approximately 40 times more effectively than by the specific CCK-A receptor antagonist L364,718. Analysis of the ability of cholecystokinin octapeptide (CCK-8) to inhibit 125I-Bolton-Hunter-CCK-8 binding revealed two CCK binding sites, i.e., a high affinity site and a low affinity site. The observed binding affinities of CCK-8 were then introduced into the computer analysis of the dose-inhibition curve of the ability of gastrin-17-I to inhibit binding of 125I-Bolton-Hunter-CCK-8, which was significantly better fit by a three-site model than by a two-site model. The three sites meet the criteria for CCK-B, high affinity CCK-A, and low affinity CCK-A receptors. The binding capacity of CCK-B receptors constitutes 34% of the total high affinity CCK binding sites. This study demonstrated that DSL-6 pancreatic carcinoma expresses three subtypes of CCK receptors. Gastrin (CCK-B) receptors, which were not detected in normal rat pancreas, constitute about one third of the total high affinity CCK receptors. We suggest that novel expression of gastrin (CCK-B) receptors may be generated by gene mutation or amplification during carcinogenesis and may play an important role in promoting tumor growth.

Animals↗