PubMed Health⌕ Search

Biomedical subjects

John L Cameron

Publications and source records attributed to John L Cameron.

At least 73 records · Page 4Linked to original sources
PubMed2002

Discovery of novel tumor markers of pancreatic cancer using global gene expression technology.

Despite several advances in our basic understanding and in the clinical management of pancreatic cancer, virtually all patients who will be diagnosed with pancreatic cancer will die from this disease. The high mortality of pancreatic cancer is predominantly because of diagnosis at an advanced stage of disease and a lack of effective treatments. We used the Gene Logic Inc. BioExpress platform and Affymetrix GeneChip arrays to identify genes differentially expressed in pancreatic cancer. cDNA was prepared from samples of normal pancreas (n = 11), normal gastrointestinal mucosa (n = 22), resected pancreas cancer tissues (n = 14), and pancreas cancer cell lines (n = 8), and was hybridized to the complete Affymetrix Human Genome U95 GeneChip set (arrays U95 A, B, C, D, and E) for simultaneous analysis of 60,000 cDNA fragments, with 12,000 fragments covering full-length genes and 48,000 fragments covering expressed sequence tags (ESTs). Genes expressed at levels at least fivefold greater in the pancreatic cancers ascompared to normal tissues were identified. Serial analysis of gene expression (SAGE) libraries (http://www.ncbi.nlm.nih.gov/SAGE/) of two normal pancreatic ductal cell cultures (HX and H126) were used to exclude genes expressed in the normal ducts (more than five tags per library). Differential expression of selected candidate genes was validated by immunohistochemical analysis (n = 3), by in situ hybridization (n = 1), and by reverse transcriptase-polymerase chain reaction (n = 8). One hundred eighty fragments were identified as having fivefold or greater expression levels in pancreas cancer specimens as compared to normal tissue, of which 124 corresponded to known genes and 56 to ESTs. Of these 124 fragments, 10 genes were represented by two or more fragments, resulting in 107 known genes identified as differentially expressed in pancreatic cancer. An additional 10 genes were expressed in the SAGE libraries of normal pancreatic duct epithelium, and were excluded from further analysis. A literature search indicated that 28 of the remaining 97 genes have been reported in association with pancreatic cancer, validating this approach. The remaining 69 genes have not been implicated in pancreatic cancer before, and have immediate potential as novel therapeutic targets and tumor markers of pancreatic cancer.

Biomarkers, Tumor↗
PubMed2002

Solid-pseudopapillary tumors of the pancreas are genetically distinct from pancreatic ductal adenocarcinomas and almost always harbor beta-catenin mutations.

Solid-pseudopapillary tumors (SPTs) are unusual pancreatic neoplasms of low malignant potential that most frequently affect young women. Genetic events contributing to the development of SPTs are unknown. Whereas the more common ductal adenocarcinomas of the pancreas essentially never harbor beta-catenin or APC gene mutations, we have recently identified alterations of the APC/beta-catenin pathway in other nonductal pancreatic neoplasms including pancreatoblastomas and acinar cell carcinomas. We analyzed a series of 20 SPTs for somatic alterations of the APC/beta-catenin pathway using immunohistochemistry for beta-catenin protein accumulation, direct DNA sequencing of beta-catenin exon 3, and direct DNA sequencing of the mutation cluster region in exon 15 of the APC gene in those SPTs that did not harbor beta-catenin mutations. Immunohistochemical labeling for cyclin D1 was performed to evaluate the overexpression of this cell-cycle protein as one of the putative downstream effectors of beta-catenin dysregulation. In addition, we analyzed the SPTs for genetic alterations commonly found in pancreatic ductal adenocarcinomas, including mutations in the K-ras oncogene and p53 and DPC4 tumor suppressor genes, using direct DNA sequencing of K-ras and immunostaining for p53 and Dpc4. Almost all SPTs harbored alterations in the APC/beta-catenin pathway. Nuclear accumulation of beta-catenin protein was present in 95% (19 of 20), and activating beta-catenin oncogene mutations were identified in 90% (18 of 20) of the SPTs. Seventy-four percent (14 of 19) showed overexpression of cyclin D1, ranging from 10 to 70% of tumor nuclei. In contrast, no K-ras mutations were present in any of the 20 SPTs, and Dpc4 expression was intact in all 16 SPTs for which immunohistochemical labeling was successful. Overexpression of p53 was limited to only 3 of 19 (15.8%) SPTs. These results emphasize the two distinct, divergent genetic pathways of neoplastic progression in pancreatic ductal and nonductal neoplasms.

Adolescent↗
PubMed2002

Overexpression of S100A4 in pancreatic ductal adenocarcinomas is associated with poor differentiation and DNA hypomethylation.

Using the National Center for Biotechnology Information Serial Analysis of Gene Expression database, we found that S100A4, a calcium-binding protein previously implicated in metastasis, was expressed in five of seven pancreatic carcinoma libraries but not in the two normal pancreatic duct libraries. We confirmed the overexpression of S100A4 using reverse transcriptase-polymerase chain reaction, which demonstrated that 18 of 19 (95%) pancreatic carcinoma cell lines expressed S100A4. Using immunohistochemistry, we found that 57 of 61 invasive pancreatic carcinomas (93%), 3 of 18 high-grade pancreatic intraepithelial neoplasia lesions (17%), and 0 of the 69 low-grade pancreatic intraepithelial neoplasia lesions expressed S100A4 protein, whereas normal pancreatic tissue and tissue affected by chronic pancreatitis did not label. Expression of S100A4 was associated with poor differentiation of the pancreatic adenocarcinomas (P = 0.001). We found that three CpG sites in the first intron of the S100A4 gene were approximately 90% methylated in microdissected normal pancreatic duct cells using bisulfite-modified sequencing and in two cell lines and three primary pancreatic carcinomas with a reduced or absent expression of S100A4. In contrast, these CpGs were 100% hypomethylated in 11 of 12 pancreatic cancer cell lines by methylation-specific polymerase chain reaction. The association between the expression of S100A4 and hypomethylation of the first intron of S100A4 was statistically significant (P = 0.002). These data suggest that the majority of pancreatic carcinomas undergo selection for hypomethylation and overexpression of S100A4. Because most pancreatic carcinomas express S100A4, it may be a useful target for early detection strategies.

Adenocarcinoma↗
PubMed2002

Telomere shortening is nearly universal in pancreatic intraepithelial neoplasia.

A multistep model of carcinogenesis has recently been proposed for pancreatic ductal adenocarcinomas. In this model, noninvasive precursor lesions in the pancreatic ductules accumulate genetic alterations in cancer-associated genes eventually leading to the development of an invasive cancer. The nomenclature for these precursor lesions has been standardized as pancreatic intraepithelial neoplasia or PanIN. Despite the substantial advances made in understanding the biology of invasive pancreatic adenocarcinomas, little is known about the initiating genetic events in the pancreatic ductal epithelium that facilitates its progression to cancer. Telomeres are distinctive structures at the ends of chromosomes that protect against chromosomal breakage-fusion-bridge cycles in dividing cells. Critically shortened telomeres can cause chromosomal instability, a sine qua non of most human epithelial cancers. Although evidence for telomeric dysfunction has been demonstrated in invasive pancreatic cancer, the onset of this phenomenon has not been elucidated in the context of noninvasive precursor lesions. We used a recently described in situ hybridization technique in archival samples (Meeker AK, Gage WR, Hicks JL, Simon I, Coffman JR, Platz EA, March GE, De Marzo AM: Telomere length assessment in human archival tissues: combined telomere fluorescence in situ hybridization and immunostaining. American Journal of Pathology 2002, 160:1259-1268) for assessment of telomere length in tissue microarrays containing a variety of noninvasive pancreatic ductal lesions. These included 82 PanIN lesions of all histological grades (24 PanIN-1A, 23 PanIN-1B, 24 PanIN-2, and 11 PanIN-3) that were selected from pancreatectomy specimens for either adenocarcinoma or chronic pancreatitis. Telomere fluorescence intensities in PanIN lesions were compared with adjacent normal pancreatic ductal epithelium and acini (62 of 82 lesions, 76%), or with stromal fibroblasts and islets of Langerhans (20 of 82 lesions, 24%). Telomere signals were strikingly reduced in 79 (96%) of 82 PanINs compared to adjacent normal structures. Notably, even PanIN-1A, the earliest putative precursor lesion, demonstrated a dramatic reduction of telomere fluorescence intensity in 21 (91%) of 23 foci examined. In chronic pancreatitis, reduction of telomere signal was observed in all PanIN lesions, whereas atrophic and inflammatory ductal lesions retained normal telomere length. Telomere fluorescence intensity in PanIN lesions did not correlate with proliferation measured by quantitative Ki-67-labeling index or topoisomerase IIalpha expression. Thus, telomere shortening is by far the most common early genetic abnormality recognized to date in the progression model of pancreatic adenocarcinomas. Telomeres may be an essential gatekeeper for maintaining chromosomal integrity, and thus, normal cellular physiology in pancreatic ductal epithelium. A critical shortening of telomere length in PanINs may predispose these noninvasive ductal lesions to accumulate progressive chromosomal abnormalities and to develop toward the stage of invasive carcinoma.

Carcinoma, Pancreatic Ductal↗
PubMed2002

Genetic and immunohistochemical analysis of pancreatic acinar cell carcinoma: frequent allelic loss on chromosome 11p and alterations in the APC/beta-catenin pathway.

Acinar cell carcinomas (ACCs) are rare malignant tumors of the exocrine pancreas. The specific molecular alterations that characterize ACCs have not yet been elucidated. ACCs are morphologically and genetically distinct from the more common pancreatic ductal adenocarcinomas. Instead, the morphological, immunohistochemical, and clinical features of ACCs overlap with those of another rare pancreatic neoplasm, pancreatoblastoma. We have recently demonstrated a high frequency of allelic loss on chromosome arm 11p and mutations in the APC/beta-catenin pathway in pancreatoblastomas, suggesting that similar alterations might also play a role in the pathogenesis of some ACCs. We analyzed a series of 21 ACCs for somatic alterations in the APC/beta-catenin pathway and for allelic loss on chromosome 11p. In addition, we evaluated the ACCs for alterations in p53 and Dpc4 expression using immunohistochemistry, and for microsatellite instability (MSI) using polymerase chain amplification of a panel of microsatellite markers. Allelic loss on chromosome 11p was the most common genetic alteration in ACCs, present in 50% (6 of 12 informative cases). Molecular alterations in the APC/beta-catenin pathway were detected in 23.5% (4 of 17) of the carcinomas, including one ACC with an activating mutation of the beta-catenin oncogene and three ACCs with truncating APC mutations. One ACC (1 of 13, 7.6%) showed allelic shifts in four of the five markers tested (MSI-high), two (15.4%) showed an allelic shift in only one of the five markers tested (MSI-low), and no shifts were detected in the remaining 10 cases. The MSI-high ACC showed medullary histological features. In contrast, no loss of Dpc4 protein expression or p53 accumulation was detected. These results indicate that ACCs are genetically distinct from pancreatic ductal adenocarcinomas, but some cases contain genetic alterations common to histologically similar pancreatoblastomas.

Adenomatous Polyposis Coli Protein↗
PubMed2002

Aberrant methylation of CpG islands in intraductal papillary mucinous neoplasms of the pancreas.

BACKGROUND & AIMS: The functional abrogation of several tumor suppressor genes, including p16, DPC4, and p53, is a major mechanism underlying pancreatic ductal carcinogenesis. However, mutational inactivation of these genes is relatively uncommon in intraductal papillary mucinous neoplasms (IPMNs) of the pancreas. We hypothesized that an alternative mechanism for gene inactivation (notably, transcriptional silencing by promoter methylation) could be important in the pathogenesis of IPMNs. METHODS: Using methylation-specific polymerase chain reaction, we analyzed the methylation status of 7 CpG islands previously identified as aberrantly methylated in pancreatic adenocarcinoma (including preproenkephalin [ppENK], p16, and thrombospondin 1) in 51 IPMNs of different histologic grades. The relationship between methylation status and expression was evaluated using reverse-transcription polymerase chain reaction for ppENK and immunohistochemistry for p16. RESULTS: We found that more than 80% of the IPMNs exhibited hypermethylation of at least one of these CpG islands. Hypermethylation of ppENK and p16 was detected at a significant higher frequency in high-grade (in situ carcinoma) IPMNs than in low-grade (adenoma/borderline) IPMNs (ppENK, 82% vs. 28%, P = 0.0002; p16, 21% vs. 0%, P = 0.04). Furthermore, the average number of methylated loci was significantly higher in high-grade IPMNs than in low-grade IPMNs (2.4 vs. 0.9; P = 0.0008). Aberrant methylation of ppENK and p16 was associated with loss of expression. CONCLUSIONS: These results suggest that de novo methylation of multiple CpG islands is one of the critical pathways that contributes to the malignant progression of IPMNs.

Adenocarcinoma, Mucinous↗
PubMed2002

Almost all infiltrating colloid carcinomas of the pancreas and periampullary region arise from in situ papillary neoplasms: a study of 39 cases.

Colloid carcinomas of organs such as the breast, colon, and prostate have been well characterized. However, up until now there have been only a few studies of colloid carcinomas of the pancreas and periampullary region, and the number of colloid carcinomas in these studies has been limited. A search of our files revealed 39 resections for pancreatic and periampullary carcinomas with colloid differentiation. All neoplasms were extensively sampled. "Carcinomas with colloid differentiation" were defined as tumors associated with abundant extracellular mucin containing free-floating mucinous epithelial cells. Cases with >50% colloid differentiation were classified as "colloid carcinomas," whereas those with less were termed "carcinomas with focal colloid features." Cases with no colloid differentiation at all were designated "carcinomas without colloid differentiation." Of the 39 carcinomas, 31 were colloid carcinomas, and eight were carcinomas with focal colloid features. Twenty-seven were centered in the pancreas, seven were in the duodenum, and five were in the ampulla of Vater. Remarkably, 38 of the 39 carcinomas (97%) arose in association with an intraductal papillary mucinous neoplasm or a tubular/tubulovillous adenoma. Of the patients with colloid carcinomas, the 2-and 5-year actuarial survival rates were 69% and 29%, respectively. There was no significant difference in survival rates between patients with colloid carcinomas and patients with adenocarcinomas without colloid differentiation, whether or not the latter arose in association with intraductal papillary mucinous neoplasms or tubular/tubulovillous adenomas. In a multivariate model colloid differentiation was not an independent predictor of patient survival, while other factors such as tumor location, perineural invasion, vascular invasion, and margin status after resection independently influenced patient survival. Most colloid carcinomas of the pancreas and periampullary region arise in association with a well-defined in situ papillary neoplasm. The diagnosis of a pancreatic or periampullary colloid carcinoma should encourage the pathologist to search for an associated low-grade in situ component. In addition, colloid carcinomas of the pancreas and periampullary region do not necessarily have a better prognosis than carcinomas without colloid differentiation. Instead, other factors such as tumor location, perineural invasion, vascular invasion, and margin status after resection are far more important.

Adenocarcinoma, Mucinous↗
PubMed2002

Trends in long-term survival following liver resection for hepatic colorectal metastases.

OBJECTIVE: To examine trends in outcomes of patients undergoing resection at a single tertiary care referral center over a 16-year period. SUMMARY BACKGROUND DATA: Hepatic resection is considered the treatment of choice in selected patients with colorectal metastasis confined to the liver. Although a variety of retrospective studies have demonstrated improvements in short-term outcomes in recent years, changes in long-term survival over time are less well-established. METHODS: Data from 226 consecutive patients undergoing potentially curative liver resection for colorectal metastases between 1984 and 1999 were analyzed. Actuarial survival rates related to prognostic determinants were analyzed using the log-rank test. RESULTS: The median survival for the entire cohort was 46 months, with 5- and 10-year survival rates of 40% and 26% respectively. Ninety-three patients operated on between 1984 and 1992 were found to have an overall survival of 31% at 5 years, compared to 58% for the 133 patients operated on during the more recent period (1993-1999). Both overall and disease-free survival were significantly better in the recent time period compared with the earlier period on both univariate and multivariate analyses. Other independent factors associated with improved survival included number of metastatic tumors < or = 3, negative resection margin, and CEA < 100. Comparisons were made between time periods for a variety of patient, tumor and treatment-related factors. Among all parameters studied, only resection type (anatomical versus nonanatomical), use of intraoperative ultrasonography, and perioperative chemotherapy administration differed between the early and recent time periods. CONCLUSIONS: Long-term survival following liver resection for colorectal metastases has improved significantly in recent years at our institution. Although the reasons for this survival trend are not clear, contributing factors may include the use of newer preoperative and intraoperative imaging, increased use of chemotherapy, and salvage surgical therapy.

Adult↗
PubMed2002

Major bile duct injuries associated with laparoscopic cholecystectomy: effect of surgical repair on quality of life.

OBJECTIVE: To assess the quality of life (QOL) of patients after surgical reconstruction of a major bile duct injury from laparoscopic cholecystectomy (LC). SUMMARY BACKGROUND DATA: The incidence of bile duct injuries has increased dramatically since the introduction and widespread use of LC. Previous reports show that at long-term follow-up, most patients surgically repaired will have a successful outcome as measured by standard clinical parameters. However, there is a general impression that these patients have an impaired QOL. Data addressing QOL of these patients are limited. METHODS: A standard QOL questionnaire was sent to 89 patients after successful surgical repair of a major bile duct injury from a LC treated at the Johns Hopkins Hospital between 1990 and 2000. The instrument consisted of 30 items on a visual analog scale categorized into physical (15 items), psychological (10 items), and social (5 items) domains. The same questionnaire was sent to age- and sex-matched healthy controls (n = 100) and to patients who underwent uncomplicated LC (n = 100). An additional portion of the questionnaire inquired about outcome measures and legal action undertaken by patients. RESULTS: Overall QOL scores for bile duct injury patients in the three domains (physical, psychological, and social) were 76%, 77%, and 75%, respectively. QOL scores were comparable to those of patients undergoing uncomplicated LC and healthy controls in the physical and social domains but were significantly different in the psychological domain. Presenting symptoms, prior repair, level of injury, number of stents, length of postoperative stenting, and length of follow-up did not influence QOL scores. Repaired patients reported similar rates of abdominal pain, change in bowel habits, use of pain medications, and recent symptoms of fever or chills as LC controls. Thirty-one percent of responding bile duct injury patients reported having sought legal recourse for their injury. All QOL domain scores were significantly lower in the patients who pursued a lawsuit versus those who did not. CONCLUSIONS: This study provides formal data evaluating QOL after surgical repair of major bile duct injuries from LC. Although there was a significant difference in the QOL as evaluated from a psychological dimension, bile duct injury patients reported QOL scores in the physical and social domains comparable to those of control patients. The decreased QOL assessment in the psychological dimension may be attributable to the prolonged, complicated, and unexpected nature of these injuries. The presence of a lawsuit appears to be associated with a poorer QOL assessment.

Adult↗
PubMed2002

Pancreaticoduodenectomy with or without distal gastrectomy and extended retroperitoneal lymphadenectomy for periampullary adenocarcinoma, part 2: randomized controlled trial evaluating survival, morbidity, and mortality.

OBJECTIVE: To evaluate, in a prospective, randomized single-institution trial, the end points of operative morbidity, operative mortality, and survival in patients undergoing standard versus radical (extended) pancreaticoduodenectomy. SUMMARY BACKGROUND DATA: Numerous retrospective reports and a few prospective randomized trials have suggested that the performance of an extended lymphadenectomy in association with a pancreaticoduodenal resection may improve survival for patients with pancreatic and other periampullary adenocarcinomas. METHODS: Between April 1996 and June 2001, 299 patients with periampullary adenocarcinoma were enrolled in a prospective, randomized single-institution trial. After intraoperative verification (by frozen section) of margin-negative resected periampullary adenocarcinoma, patients were randomized to either a standard pancreaticoduodenectomy (removing only the peripancreatic lymph nodes en bloc with the specimen) or a radical (extended) pancreaticoduodenectomy (standard resection plus distal gastrectomy and retroperitoneal lymphadenectomy). All pathology specimens were reviewed, fully categorized, and staged. The postoperative morbidity, mortality, and survival data were analyzed. RESULTS: Of the 299 patients randomized, 5 (1.7%) were subsequently excluded because their final pathology failed to reveal periampullary adenocarcinoma, leaving 294 patients for analysis (146 standard vs. 148 radical). The two groups were statistically similar with regard to age (median 67 years) and gender (54% male). All the patients in the radical group underwent distal gastric resection, while 86% of the patients in the standard group underwent pylorus preservation ( <.0001). The mean operative time in the radical group was 6.4 hours, compared to 5.9 hours in the standard group ( =.002). There were no significant differences between the two groups with respect to intraoperative blood loss, transfusion requirements (median zero units), location of primary tumor (57% pancreatic, 22% ampullary, 17% distal bile duct, 3% duodenal), mean tumor size (2.6 cm), positive lymph node status (74%), or positive margin status on final permanent section (10%). The mean total number of lymph nodes resected was significantly higher in the radical group. Of the 148 patients in the radical group, only 15% (n = 22) had metastatic adenocarcinoma in the resected retroperitoneal lymph nodes, and none had retroperitoneal nodes as the only site of lymph node involvement. One patient in the radical group with negative pancreaticoduodenectomy specimen lymph nodes had a micrometastasis to one perigastric lymph node. There were six perioperative deaths (4%) in the standard group versus three perioperative deaths (2%) in the radical group ( = NS). The overall complication rates were 29% for the standard group versus 43% for the radical group ( =.01), with patients in the radical group having significantly higher rates of early delayed gastric emptying and pancreatic fistula and a significantly longer mean postoperative stay. With a mean patient follow-up of 24 months, there were no significant differences in 1-, 3-, or 5-year and median survival when comparing the standard and radical groups. CONCLUSIONS: Radical (extended) pancreaticoduodenectomy can be performed with similar mortality but some increased morbidity compared to standard pancreaticoduodenectomy. The data to date fail to indicate that a survival benefit is derived from the addition of a distal gastrectomy and retroperitoneal lymphadenectomy to a pylorus-preserving pancreaticoduodenectomy.

Adenocarcinoma↗
PubMed2002

Immunohistochemical validation of a novel epithelial and a novel stromal marker of pancreatic ductal adenocarcinoma identified by global expression microarrays: sea urchin fascin homolog and heat shock protein 47.

We extended the results of a previous microarray analysis by immunohistochemical validation of differential protein expression in a series of 57 surgically resected infiltrating ductal pancreatic adenocarcinomas. Two representative genes were examined: sea urchin fascin homolog (overexpressed in both cell lines and primary tumors) and heat shock protein 47 (HSP47; overexpressed in primary tumors only). Protein expression also was evaluated in the precursor lesions of pancreatic cancer pancreatic intraepithelial neoplasia (PanIN), and normal ductal epithelium. Fascin expression was seen in the neoplastic cells of 54 (95%) of 57 ductal adenocarcinomas but not in 49 (94%) of 52 adjacent nonneoplastic epithelium. In the multistep pathogenesis of ductal adenocarcinomas, fascin expression seemed to be a late event, usually present in PanINs 2 and 3. HSP47 expression was almost universal and most intense in the ductal adenocarcinoma-associated stromal desmoplasia (57/57), although 37 cases (65%) also expressed HSP47 in the neoplastic epithelium. HSP47 expression was absent in the majority of nonneoplastic pancreata (46 [88%]). Fascin and HSP47 are novel tumor markers with potential diagnostic and therapeutic implications for pancreatic carcinoma. These results establish the usefulness of global expression platforms to identify novel tumor markers.

Adult↗