Growth factors and oncogenes in pancreatic cancer

Molecular pathogenesis of precursor lesions of pancreatic ductal adenocarcinoma

Precursor lesions are assuming greater importance in the study of pancreatic ductal adenocarcinoma. As pancreatic cancer is almost universally fatal due to late clinical presentation and biological aggressiveness, characterisation of its precursor lesions may create scope for early diagnosis and improved outcome with conventional therapies as well as the development of novel therapeutic and preventative strategies. Pancreatic intraepithelial neoplasia (PanIN) and intraductal papillary mucinous tumours (IPMTs) are thought to be precursor lesions of ductal adenocarcinoma of the pancreas. Recent work has focused on the molecular aberrations associated with these lesions leading to the formulation of a progression model for pancreatic cancer. Progressive histopathological changes along the progression model are associated with aberrations of cell cycle regulatory and growth factor signalling molecules that occur in pancreatic cancer at high frequency and are common to many cancers. Characterisation of these molecular aberrations provides scope for the development of novel diagnostic and treatment strategies that will ultimately impact on the outcome for people who develop pancreatic cancer.

Pancreatic cancer: factors regulating tumor development, maintenance and metastasis

Pancreatic cancer has one of the poorest prognoses of all gastrointestinal malignancies. Today, it is the fourth or fifth leading cause of cancer-related deaths in Western industrialized countries, and the incidence has been increasing throughout the past decades. Insensitivity to growth-inhibitory and apoptotic signals as well as self-sufficiency of growth-promoting factors are hallmarks of the pathogenesis of this malignancy. In pancreatic cancer, a variety of growth factors and their receptors are expressed at increased levels. For example, the concomitant presence of the epidermal growth factor (EGF) receptor and its ligand EGF is associated with enhanced tumor aggressiveness and shorter survival following tumor resection. Furthermore, a number of other growth factors and their receptors, such as nerve growth factor and its receptor, are overexpressed in pancreatic cancer and contribute to its malignant phenotype. Besides factors which directly promote cell proliferation, a variety of other factors such as galectins are upregulated, which influences the tumor environment and the invasiveness of pancreatic cancer cells. In addition, tumor suppressor genes such as KAI1 are expressed at reduced levels, thereby enhancing the ability of pancreatic cells to form metastases. A complex disturbance of factors is present in pancreatic cancer, resulting in a distinct growth advantage which clinically results in rapid tumor progression and poor patient survival.

Growth factors in pancreatic health and disease

In this article the role of different growth factors and their receptors in the pathogenesis of chronic pancreatitis and pancreatic cancer is discussed. The expression of members of the epidermal growth factor family, the fibroblast growth factor family, the transforming growth factor-beta family, the platelet-derived growth factor family, the nerve growth factor family, the insulin-like growth factor family and their signaling receptors is presented, and a correlation of the molecular data with clinical and pathological changes is performed. A number of these growth factors and their receptors are markedly overexpressed in chronic pancreatitis and pancreatic cancer. In chronic pancreatitis, overexpression of growth factors and their receptors contributes to tissue remodeling and fibrogenesis. In contrast to chronic pancreatitis, pancreatic cancer is associated with a variety of genetic alterations, including mutations in tumor suppressor genes and cell cycle regulators. In the presence of these genetic disturbances, enhanced expression of growth factors and their receptors contributes to cell proliferation and enhances the aggressiveness of pancreatic cancer cells. In summary, growth factors and their receptors are often altered in chronic pancreatitis and pancreatic cancer and contribute to various pathogenetic aspects in these disorders.

An immunostaining panel for diagnosis of malignancy in mucinous tumors of the pancreas

BACKGROUND

The diagnosis of malignancy in pancreatic mucinous cystic tumors depends on demonstrating invasion that may be focal and require extensive sectioning.

OBJECTIVE

To explore markers that may indicate malignant potential in mucinous cystic tumors.

DESIGN

Routinely processed sections from resected specimens of 12 normal pancreata, 14 pancreata with chronic pancreatitis, 9 mucinous cystic tumors, and 30 invasive adenocarcinomas were immunostained with antibodies to p53, HER-2/neu, epithelial growth factor receptor (EGFR), transforming growth factor alpha (TGF-alpha), and Ki-67.

RESULTS

Expression of p53, HER-2/neu, and Ki-67 was significantly more frequent in mucinous tumors than in normal pancreatic tissue and chronic pancreatitis tissue (P =.0003 to.05). Strong expression (more than one third of cells positive) and strong intensity (2+ and 3+) of staining of p53 and EGFR were seen only in carcinomas. Coexpression of p53/HER-2/neu and EGFR/HER-2/neu and a frequency of Ki-67+ nuclei of greater than 5% of cells discriminated between mucinous tumors and normal pancreatic tissue and chronic pancreatitis tissue. p53 expression was significantly more frequent in carcinomas than in mucinous tumor (P =.0326). Coexpression of p53/EGFR discriminated between mucinous tumors and carcinomas; however, TGF-alpha was not discriminative.

CONCLUSIONS

The immunostaining panel of p53, HER-2/neu, Ki-67, and EGFR can be helpful in indicating malignant potential in mucinous tumors of pancreas in routine pathology practice.

Apoptosis and expression of Bcl-2 and Bax proteins in invasive ductal carcinoma of the pancreas

The Bcl-2 family of genes plays important roles in the regulation of apoptosis. The present study was designed to assess the clinicopathologic significance of apoptosis and the expression of the apoptosis-inhibitory Bcl-2 protein (pBcl-2) and the apoptosis-promoting Bax protein (pBax) in human invasive ductal carcinomas (IDCs) of the pancreas. The present study included 66 IDCs that were resected between 1982 and 1998. Apoptosis was assessed by the in situ nick end labeling method and pBcl-2 and pBax were stained immunohistochemically. Apoptosis was quantified as the apoptotic index (AI, the percentage of apoptotic cells of the total tumor cells), and a high AI (>10%) was observed in 26 of the 66 (39%) IDCs. The AI correlated significantly with the extent of nodal involvement. pBax immunoreactivity was detected in 42 of 66 IDCs (64%), and pBax expression was significantly correlated with female gender and showed a significant negative correlation with the extent of nodal involvement. pBcl-2 was expressed in 16 IDCs (24%) but did not show any correlation with the clinicopathologic factors. The AI did not correlate with the expression of pBcl-2 or pBax, but there was a significant correlation between the expression of pBcl-2 and that of pBax; 15 of the 16 pBcl-2(+)IDCs were also pBax(+), and only one pBcl-2(+)IDC was pBax(-). Univariate analysis demonstrated that the degree of apoptosis had no significant influence on the patients' prognosis, pBax or pBcl-2 expression was significantly associated with a better prognosis, and in particular, the pBax(+)pBcl-2(+) group had a significantly higher survival than the other groups. On the other hand, the survival curve of the adjuvant chemotherapy (ACT) group was also higher than that of the surgery alone (SA) group, with borderline statistical signfiicance. The ACT group showed a significantly better survival rate than the SA group for the pBax(+)IDC patients, but the AI and pBcl-2 expression were not correlated with an improved survival rate in the ACT group. Multivariate analysis showed that the AI. pBcl-2 expression, and pBax expression by themselves did not represent significant variables for death owing to IDC, but pBax expression was significantly associated with the efficacy of ACT. In conclusion, pBax expression may be essential for pBcl-2 expression. pBcl-2 and pBax expressions are not significant prognostic factors for patients with IDC, but pBax expression may be beneficial in predicting the effects of ACT on patients with IDC.

Expression of Bcl-2 and p53 protein in resectable invasive ductal carcinoma of the pancreas: effects on clinical outcome and efficacy of adjuvant chemotherapy

BACKGROUND AND OBJECTIVES

p53 tumor suppressor gene has a dual role as a trigger of apoptosis and as an initiator of DNA repair. The Bcl-2 can work to protect cells from apoptosis, which is induced by p53 gene. These facts suggest the significant role of these genes in the genesis and progression of various tumors. The present study was designed to assess the significance of p53 and Bcl-2 protein (pBcl-2) expression on resectable invasive ductal carcinoma (IDC) of the pancreas.

METHODS

The present study included 63 IDCs, which were resected between 1982 and 1998. pBcl-2 and p53 were stained immunohistochemically with monoclonal antibodies.

RESULTS

pBcl-2 was expressed in 16 (25.4%), and p53 was positively expressed in 32 out of 63 IDCs (50.8%); however, expression of pBcl-2 did not necessarily correlate with that of p53. Although p53 expression did not show any significant influence on the patients' survival, pBcl-2(+) patients showed a higher survival than pBcl-2(-) patients for both p53(+) and p53(-) patients, which suggested that pBcl-2 expression had a more significant effect on the survival of patients than p53 expression. On the other hand, there were no differences in the survival curve between the adjuvant chemotherapy (ACT) group and the surgery alone (SA) group. pBcl-2 expression had no influence on the effect of ACT, the ACT group showed a significantly better survival than the SA group for p53(+) IDC patients.

CONCLUSIONS

pBcl-2 expression is a beneficial prognostic factor for patients with IDC, whereas p53 expression may be beneficial in the prediction of the effects of adjuvant chemotherapy on patients with IDC. J. Surg. Oncol. 2001;76:188-196.

Growth factors and their receptors in pancreatic cancer

Pancreatic cancer has an incidence of approximately 8 to 10 cases per 100,000 citizens in Western industrialized countries, and the incidence has been increasing throughout the last decades. Insensitivity to antigrowth and apoptotic signals as well as self-sufficiency in growth signals are hallmarks of malignant growth. Pancreatic cancers often exhibit alterations in growth inhibitory pathways such as Smad4 mutations and Smad6 and Smad7 overexpression, and evade apoptosis through p53 mutations and aberrant expression of apoptosis regulating genes. In addition, in pancreatic cancer a variety of growth factors are expressed at increased levels. For example, the concomitant presence of the EGF-receptor and its ligands EGF, TGF-alpha, and/or amphiregulin is associated with enhanced tumor aggressiveness and shorter survival periods following tumor resection. Furthermore, a number of other growth factors and their receptors, such as fibroblast growth factors, nerve growth factor, platelet-derived growth factors, and insulin-like growth factors and their respective receptors are expressed at increased levels in pancreatic cancer and are thought to contribute to its malignant phenotype. Taken together, the disturbance of growth inhibitory and apoptotic pathways and the abundance of growth promoting factors give pancreatic cancer cells a distinct growth advantage which clinically results in rapid tumor progression and poor survival prognosis.

Molecular technology and pancreatic cancer

BACKGROUND

Pancreatic cancer is the fifth leading cause of cancer death in the Western world. Despite improvement in operative mortality rates, little impact has been made on overall 5-year survival. This review discusses the molecular changes peculiar to pancreatic cancer and how the use of molecular technology might affect detection, screening, diagnosis and treatment of the disease.

METHODS

A literature review was performed using the National Library of Medicine's Pubmed database; this was combined with ongoing work within the Queen Elizabeth Hospital, Birmingham.

RESULTS

Over the past 20 years great strides have been made in our understanding of the molecular basis of disease. Advances in molecular biology are now reshaping how diseases are screened for, diagnosed, investigated and treated. In recent years collaboration between clinicians and basic scientists has revealed a unique pattern of genetic and molecular events in pancreatic cancer. This review discusses how these advances may impact on patients with this disease.

CONCLUSION

The past decade has seen some improvement in outlook for patients with pancreatic cancer, but the 'molecular age' promises to deliver even better results.

Molecular biology of pancreatic cancer; oncogenes, tumour suppressor genes, growth factors, and their receptors from a clinical perspective

Pancreatic cancer represents the fourth leading cause of cancer death in men and the fifth in women. Prognosis remains dismal, mainly because the diagnosis is made late in the clinical course of the disease. The need to improve the diagnosis, detection, and treatment of pancreatic cancer is great. It is in this type of cancer, in which the mortality is so great and the clinical detection so difficult that the recent advances of molecular biology may have a significant impact. Genetic alterations can be detected at different levels. These alterations include oncogene mutations (most commonly, K-ras mutations, which occur in 75% to more than 95% of pancreatic cancer tissues), tumour suppressor genes alterations (mainly, p53, p16, DCC, etc.), overexpression of growth factors (such as EGF, TGF alpha, TGF beta 1-3, aFGF, bTGF, etc.) and their receptors (i.e., EGF receptor, TGF beta receptor I-III, etc.). Insights into the molecular genetics of pancreatic carcinogenesis are beginning to form a genetic model for pancreatic cancer and its precursors. These improvements in our understanding of the molecular biology of pancreatic cancer are not simply of research interest, but may have clinical implications, such as risk assessment, early diagnosis, treatment, and prognosis evaluation.

The use of molecular technology in the differentiation of pancreatic cancer and chronic pancreatitis

CONCLUSION

It is concluded that currently there are limitations in the use of some of the proposed tests, whereas in the future, further progress in our understanding of the molecular biology of pancreatic disease and the development and application of existing techniques should have a greater impact on clinical practice.

BACKGROUND

Fifteen to 20% of patients with pancreatic cancer present with a resectable mass in the head of the pancreas, but there is a subgroup of patients for whom it is difficult to reach the correct diagnosis.

METHOD

This article addresses how molecular technology can be used to aid in the diagnosis of this group of patients. The clinical and scientific literature is reviewed by accessing papers through the Medline database.

RESULTS

This article reviews the limitations of conventional imaging techniques and the limitations of fine needle aspiration cytology and cytological examination of pancreatic duct secretions. The molecular biology of both pancreatic cancer and chronic pancreatitis is then reviewed with emphasis on the common molecular defects seen in these diseases. The current use of molecular techniques in the examination of cytological and histological specimens, stool, blood, and pancreatic duct secretions and how this helps discriminate between benign and malignant lesions of the pancreas is addressed. Finally, the use of novel serum screening tests in groups at high risk of pancreatic cancer is discussed.

Molecular diagnosis of pancreas carcinoma

Cellular protooncogenes, tumor suppressor genes (antioncogenes), and DNA mismatch repair mutators are generally the key molecular genetic biomarkers undergoing alterations during carcinogenesis, i.e., activation of oncogenes, inactivation of tumor suppressors, and DNA mismatch repair gene defects are essential events in cancer causation. In pancreas cancer, high incidence of oncogene K-ras point mutations at the codon 12th is associated with premalignant and malignant transformation. Mutation in p53 tumor suppressor is also detected in pancreas adenocarcinoma. Concurrent loss of p53 and K-ras function may contribute to the clinical aggressiveness of pancreas cancer. Microsatellite instability and DNA mismatch repair defects may represent new mutator phenotype for pancreas carcinogenesis. Mutation of cell cycle regulators, such as inhibitor of CDK4 or p16 tumor suppressor gene, is a new molecular event in pancreas cancer. Mutation of cyclin-dependent kinases also may be involved in pancreas carcinogenesis. Loss or mutation of a new candidate tumor suppressor, DPC4 (deleted in pancreas carcinoma locus 4), is reported in pancreas cancer. The protein products of these gene mutations are potential tumor antigens, thus genotype expression can be detected by phenotype. Most of these emerging molecular genetic biomarkers are associated with regulation of cell growth and recognition, as well as gene expression, and may offer new insight into the cellular precursors to and genesis of pancreas cancer.

Immunohistochemical evaluation of HER-2/neu expression in pancreatic adenocarcinoma and pancreatic intraepithelial neoplasms

Although several morphological and molecular genetic studies have implicated various grades of pancreatic duct hyperplasia as precursor lesions to infiltrating pancreatic adenocarcinoma, the identity of preinvasive pancreatic neoplasms remains controversial. In the present study, the authors examined the expression of the epidermal growth factor receptor homologue, HER-2/neu (c-erbB-2), in pancreatic duct lesions adjacent to infiltrating pancreas cancers in a series of 19 cases of pancreatic duct adenocarcinoma. HER-2/neu expression was examined because it has been identified in a proportion of infiltrating pancreas cancers and because it may provide early neoplasms with a growth advantage over adjacent nonneoplastic epithelium. In normal pancreatic ducts and ductules, HER-2/neu expression was absent in all but one case. By contrast, HER-2/neu was expressed in 82% (P = .008 vs normal ) of ducts with flat mucinous hyperplasia, 86% (P = .03 vs normal) of ducts with papillary mucinous hyperplasia without atypia, 92% (P = .001 vs normal) of ducts with atypical papillary mucinous hyperplasia, and all specimens with carcinoma in situ. HER-2/neu expression was observed in 69% (P = .002 vs normal) of the moderately differentiated infiltrating carcinomas and none of the poorly differentiated infiltrating carcinomas. These data establish HER-2/neu as a potential mediator of growth factor-related signal transduction in pancreatic duct lesions, and provide additional support for the hypothesis that lesions formerly regarded as various grades of hyperplasia instead may represent intraepithelial neoplasms with the potential for subsequent invasion and metastasis.

Oncogenes in cancer of the pancreas

A three-step immunoperoxidase staining technique was used in order to estimate the immunohistochemical expression of K-ras, c-fos, c-myc and c-erbB-2 oncoproteins, in paraffin sections of 20 patients, with histologically proven adenocarcinoma of the pancreas. The two oncogenes that were found to be associated with pancreatic adenocarcinoma were K-ras and c-erbB-2. in 15 patients (75%) and four patients (20%), respectively. Positive immunostaining was intense, cytoplasmic and was noted in a great percentage of cancer cells. The same model of expression was observed in the examined cases of metastatic tissue from liver and lymph node metastases. The expression of myc and fos oncogenes was nuclear, weak and was observed in a small number of patients.

Insulin-like growth factor-I, interleukin-1 alpha and beta in pancreatic cancer: role in tumor invasiveness and associated diabetes

We evaluated levels of insulin-like growth factor-I and interleukin-1 alpha and beta in patients with pancreatic cancer; the role of these substances in tumor spread and in hyperglycemia was also investigated. Thirty pancreatic cancer patients (21 with hyperglycemia) were compared with others with diseases causing hyperglycemia [liver cirrhosis (14 cases, 12 with hyperglycemia), chronic pancreatitis (20 cases, 12 with hyperglycemia), type I diabetes mellitus (13 cases, all hyperglycemic)]. Insulin-like growth factor-I was significantly reduced in patients with liver cirrhosis, probably due to a reduced hepatic capacity for synthesis. It was increased in 6 of 30 pancreatic cancer patients; in these subjects it was correlated with alanine aminotransferase and C-peptide, but not with tumor diameter or the presence of metastases. Interleukin-1 alpha and beta were both elevated in pancreatic cancer patients. The former was high, while the latter was low when liver metastases were present. Neither was related to glucose or C-peptide levels. In summary, insulin-like growth factor-I levels are increased in some pancreatic cancer patients but this does not seem to favor tumor spread; however IGF-I could be involved influencing glucose homeostasis. Interleukin-1 alpha increased, while interleukin-1 beta decreased in pancreatic cancer patients with metastases, suggesting a different involvement of these two substances in pancreatic cancer spread.

The genetic basis of colorectal cancer--clinical implications

Colorectal carcinomas demonstrate extensive molecular genetic alterations throughout the genome. The genetic changes in cancer of the colon and rectum are among the best understood of any common human cancer. The genetic abnormalities include both dominant-acting oncogenes (Ki-ras, c-src) and tumor-suppressor genes which undergo inactivation or loss (APC, DCC, p53). The evolution of the cancer is a complicated and multistep process. At the various steps of this phenomenon we can recognize specific molecular genetic alterations. These particular genetic changes may be useful as improved markers to predict those patients who have an aggressive cancer of the colon, with occult metastases or increased metastatic capability and this selection of patients could lead to improved surgical and medical management.

Cellular and subcellular localization of transforming growth factor-alpha and epidermal growth factor receptor in normal and diseased human and hamster pancreas

Four normal pancreas, 8 chronic pancreatitis specimens, and 30 non-endocrine pancreatic tumors from humans and 6 normal and 6 induced pancreatic cancers in hamsters were examined immunohistochemically by antibodies against human transforming growth factor-alpha (TGF-alpha) and epidermal growth factor receptor (EGFR). Two normal pancreas and two pancreatic cancer specimens from each species were also studied immunoelectron microscopically by the immunogold method. In chronic pancreatitis, the reactivity and intensity of the staining with both antibodies were much greater in ductal/ductular cells than in the normal pancreas. All 30 pancreatic cancers reacted with both antibodies with a variable degree of reactivity and staining intensity. No correlation was found between the histological type of tumors, the degree of tumor differentiation, and the incidence and patterns of reactivity of either antibody. Immunoelectron microscopically, both EGFR and TGF-alpha were demonstrated primarily on the basal membrane. In the normal hamster pancreas, TGF-alpha was overexpressed in the alpha-cells but not in any other islet cells. Both TGF-alpha and EGFR were marginally detectable in the exocrine pancreas and in induced pancreatic lesions. This is the first demonstration of subcellular localization of TGF-alpha and EGFR in the normal and diseased human and hamster pancreas.

Frequent alterations of the tumor suppressor genes p53 and DCC in human pancreatic carcinoma

BACKGROUND/AIMS

The pathogenesis of pancreatic cancer is poorly understood. The multigenetic nature of carcinogenesis has been best documented in colon cancer. The relevance of this model was suggested for other epithelial tumors. Only advanced stages of pancreatic cancer are usually detected because of late diagnosis. Analysis of accumulated, diverse genetic changes could allow further understanding of putative mechanisms involved in tumor development. Activated c-Ki-ras oncogene has been shown to be a frequent event. However, additional alterations of tumor suppressor genes are expected. Therefore, concomitant genetic changes of p53 and deleted in colon carcinoma (DCC) in pancreatic carcinoma cell lines and primary tumors were analyzed.

METHODS

p53 protein and transcript expression were revealed by immunocytochemistry and immunohistochemistry, immunoassay, and Northern blot analysis. p53 mutations were identified by sequence analysis. DCC expression was investigated by reverse-transcription polymerase chain reaction.

RESULTS

p53 overexpression was observed in 9 of 12 cell lines. p53 point mutations were confirmed in seven cell lines overexpressing p53. The majority of cell lines showed concomitant p53 and DCC alterations. Four of 6 primary tumors overexpressing p53 also showed loss of DCC expression.

CONCLUSIONS

p53 and DCC genetic changes are associated with pancreatic cancer and the frequently activated c-Ki-ras oncogene. Therefore, the multihit model of carcinogenesis could prove relevant for pancreatic cancer.

Human ductal adenocarcinomas of the pancreas express extracellular matrix proteins

Pancreatic ductal adenocarcinomas are characterised by a dense connective tissue reaction. To test the hypothesis that stroma components are synthesised and produced by the tumour cells themselves, eight cell lines as well as six xenografted tumours from human ductal adenocarcinomas of the pancreas were examined for the expression of extracellular matrix proteins (ECM), using cDNA probes and antibodies to collagen types I, III and IV, vitronectin, fibronectin, undulin and laminin. All tumour cell lines (CAPAN-1, CAPAN-2, AsPC-1, BxPC-3, PANC-1, PaCa-2, PaCa-3, PaCa-44) and xenografted human pancreatic tumours expressed at least one of the examined ECM at the RNA (collagen type IV > laminin = fibronectin = vitronectin > collagen type III > undulin > collagen type I) or protein level (collagen type IV = collagen type III > vitronectin > laminin > collagen type I = fibronectin > undulin). In nude mouse tumours expression of laminin and collagen I was most pronounced in well-differentiated carcinomas. In a few tumours, collagen type III, vitronectin and undulin were expressed on the luminal side of the neoplastic glands, suggesting loss of normal polar differentiation. Incubation with fetal calf serum modulated ECM RNA levels to a varying extent in all but one cell line (AsPC-1). The results suggest that human pancreatic ductal adenocarcinomas cells are capable of synthesising and producing extracellular matrix proteins in vitro and in vivo, but that the extent and pattern of ECM expression differs between the various tumours and conditions tested.

A mucous histochemical and immunohistochemical study of precancerous and neoplastic lesions in the human pancreas

A total of 44 cases of pancreatic lesions, including hyperplasia (six) cases, adenoma (mucinous cystadenomas [eight] and intraductal papillary adenoma [eight]), noninvasive intraductal papillary tumors (five), and invasive ductal carcinomas (17) were investigated possibly to establish a diagnostic marker. We examined the type of mucin secreted and immunoreactivities of antibodies to ras-p21 and c-erB-2 oncogene products. A significant decrease in the amount of mucin was found in invasive lesions, and this was associated with a shift toward production of neutral mucins and especially sialomucins. Hyperplasia and adenoma, in contrast, demonstrated a predominance of neutral mucin. The sulfated mucins found in normal epithelium were only very weakly stained in any of the tumor types. Thirty-three percent of non-invasive intraductal papillary tumors and 88% of invasive ductal adenocarcinomas demonstrated strong binding of the ras-p21 antibody. In contrast no obvious differences in expression of c-erbB-2 were evident between the groups. In conclusion, a combined mucin histochemical/immunohistochemical approach may facilitate accurate diagnosis.

Hormonal therapy of pancreatic carcinoma. Rationale and perspectives

Exocrine pancreas carcinoma is still diagnosed at a relatively late stage, so that only a few cases can be cured by surgery. Therefore, it is desirable that an effective medical therapy be found first to stall the development of the disease and second to improve the life conditions of patients. On the basis of recent discoveries, a new therapeutic approach seems to derive from hormone manipulation. The growth of pancreatic carcinoma appears to be stimulated by various factors, such as Epidermal Growth Factor (EGF) and Insulin-like Growth Factor I (IGF-I), and by various hormones, such as androgens and cholecystokinin. Several studies performed on cell lines and on animal models of pancreatic carcinoma demonstrated an antitumoral effect of certain antihormones and of somatostatin. Taking such studies as a premise, the first clinical studies were finally started in patients suffering from nonoperable pancreatic cancer. Results are still partial and contradictory, but such research is certainly worthy of further study along the lines already taken.

Rapid acinar to ductal transdifferentiation in cultured human exocrine pancreas

Experiments have been performed to define conditions for the primary culture of human exocrine pancreas, as a first step towards molecular reconstruction experiments of pancreatic neoplasia. Normal human exocrine pancreas was digested using collagenase and dispase and the resulting cellular aggregates were cultured in vitro. The phenotype of the digested pancreatic cells was almost exclusively acinar (amylase-positive, keratin 19 and mucin antigens-negative), yet within 4 days of culture the cells had taken on a ductal phenotype (amylase-negative, keratin 19 and mucin antigens-positive). The kinetics of these observations exclude the possibility of overgrowth of the acinar population by a ductal sub-population, and selective adherence is excluded by examination of those cells that do not adhere, which are representative of the initiating population. We interpret these data as indicating that, under the conditions of culture, the acinar cell phenotype is not stable and can transdifferentiate to a ductal phenotype. Taken together with recent data from transgenic animals, this in vitro observation has possible implications for our view of the pathogenesis of pancreatic neoplasia.

The epidermal growth factor receptor in human pancreatic cancer

The epidermal growth factor receptor (EGFR) and its ligands are thought to be important in the control of proliferation of many epithelial systems, including the exocrine pancreas. Abnormalities in expression of two of the known ligands of the EGFR, transforming growth factor alpha and epidermal growth factor, occur frequently in ductal adenocarcinoma of the human pancreas. We have examined an archival series of cases of pancreatic pathology for expression of the EGFR using the anti-EGFR antiserum 12E and found that there is almost ubiquitous overexpression of EGFR in pancreatic cancer and in chronic pancreatitis. Southern blot analysis showed no evidence of amplification or rearrangement of the EGFR gene. We conclude that an autocrine loop involving the EGFR system may be involved in the genesis of both neoplasia and reactive hyperplasia of pancreatic ductal epithelium.

Ki-ras oncogene activation in preinvasive pancreatic cancer

Activation of the Ki-ras oncogene by specific point mutations at codon 12 occurs at a remarkably high frequency in pancreatic ductal adenocarcinoma and is likely to be an important event in the pathogenesis of this cancer. To determine whether ras activation also occurs in noninvasive proliferative lesions of the pancreas, a series of cases of ductal papillary hyperplasia, intraductal papillary neoplasia, and intraduct extensions of ductal adenocarcinoma were examined for activating mutations of Ki-ras at codons 12, 13, and 61 using polymerase chain reaction amplification. Specific mutations at Ki-ras codon 12 were found in 5 of 6 cases (83%) of intraduct extensions of carcinomas and in 12 of 16 (75%) invasive carcinomas. In cases with both intraductal and invasive components, the same mutation was identified in each. No mutations were found in 5 intraductal papillary neoplasms and 9 cases of ductal papillary hyperplasia. The authors conclude that Ki-ras activation at codon 12 is important in the tumorigenesis of ductal adenocarcinoma of the pancreas but is not required in the pathogenesis of ductal papillary hyperplasia or intraductal papillary neoplasm.

Abnormalities of the p53 tumour suppressor gene in human pancreatic cancer

The tumour suppressor gene p53 has been found to be mutated or inactivated at high frequency in several common human tumours. We have examined a series of exocrine pancreatic carcinomas for over-expression of mutant forms of p53 by immunohistochemistry with a panel of specific antibodies. We found immunodetectable p53 in 13 of 22 (60%) frozen pancreatic cancers and seven of 13 pancreatic cell lines. One of the antibodies, CM1, recognises p53 in formalin-fixed, paraffin-embedded archival material and using this reagent we found immunodetectable p53 in 28 of 124 (23%) pancreatic cancers. We have successfully demonstrated the presence of point mutations by direct sequencing of genomic DNA extracted from archival tissue showing CM1 immunoreactivity. We conclude that p53 activation is an important event in human pancreatic tumorigenesis and that the CM1 antibody can detect a proportion of cases of overexpression of mutant p53 in archival pathological material.