The oncofetal J28 epitope involves fucosylated O-linked oligosaccharide structures of the fetoacinar pancreatic protein.

The fetoacinar pancreatic protein (FAP), characterized by the mAb J28, is an oncofetal form of bile salt dependent lipase (BSDL), the expression of which is related to pancreatic differentiation and neoplastic processes. Because the J28 epitope, recognized by mAb J28, is suggested to be dependent upon carbohydrates, we have attempted to gain information about the structure of this epitope. Indeed, treatment of FAP with sodium periodate abolished the reactivity of the protein to mAb J28, which demonstrates the implication of oligosaccharides in the structure of the J28 epitope. FAP offers both O-linked and N-linked carbohydrate structures, of which, as we have determined, one is involved. Peptides obtained after cyanogen bromide cleavage were desialylated then separated by affinity chromatography on an immobilized peanut agglutinin agarose column. The peptide retained on this column carried out the reactivity with the mAb J28. Although some differences in amino acid analysis were observed, the N-terminal sequence of this peptide correlates with that of the C-terminal part of the enzyme. Carbohydrate analysis of the peptide bearing the J28 epitope revealed fucose, galactose, N-acetylgalactosamine, N-acetylglucosamine, and N-acetylneuraminic acid. The competition observed between mAb J28 and Ulex europaeus I lectin for binding to the J28 epitope suggested that fucose residue alpha (1-2) linked to a galactose residue was implicated in the structure of the J28 epitope. Alternatively, the loss of the mAb J28 reactivity upon treatment of FAP either with bovine kidney or bovine epididymis fucosidase was observed indicating that fucose residues linked at the alpha (1-2) and alpha (1-6) positions may be involved in the establishment of the structure of the J28 epitope. These observations suggest that mAb J28 recognized a particular fucosylated O-linked oligosaccharide structure located at the mucin-like extended C-terminal part of FAP.

Retention of the fetoacinar pancreatic (FAP) protein to the endoplasmic reticulum of tumor cells.

The fetoacinar pancreatic (FAP) protein is a specific component of the human exocrine pancreas associated with the differentiation and proliferation of acinar cells. FAP expression is enhanced in cases of pancreatic exocrine cancer and it is found in relatively high concentrations in pathological pancreatic juices. However, tumor cell lines do not secrete FAP into the culture medium. In this paper we analyze the intracellular localization of FAP in cell lines and compare some biological properties of the tumoral FAP with the normal adult and fetal forms. Immunocytological experiments performed using Mab J28 which characterizes FAP, gave a staining pattern suggestive of FAP localization in the ER. Subcellular fractionation corroborated this localization and established that FAP is tightly associated with the microsomal membranes. The absence of reactivity of the tumoral FAP with wheat germ agglutinin lectin and its strong reactivity with concanavalin A is consistent with the idea that FAP in tumor cells does not reach the Golgi apparatus and it is consequently retained in the endoplasmic reticulum (ER). FAP contained in hepatic metastasis derived from pancreatic adenocarcinoma appeared to be similar, if not identical, to that expressed by cell lines. This supports the hypothesis that FAP retention in the ER of malignant cells is a physiological phenomenon and not the result of a modification of cell lines due to the culture conditions. FAP expressed by cancer cell lines and metastases appeared by sodium dodecyl sulfate polyacrylamide gel electrophoresis a homogeneous protein with a M(r) of 120,000. Instead, the secreted mature protein consists of a main component of M(r) 110,000 and shows pronounced polymorphism (dispersion from M(r) 110,000 to 80,000). Increased size of the ER-retained protein is likely due to elongation of the peptide chain. Defective processing in the ER as a result of amino acid mutation could therefore explain the behavior of this protein in tumors.

Human fetoacinar pancreatic protein: an oncofetal glycoform of the normally secreted pancreatic bile-salt-dependent lipase.

A fetoacinar pancreatic protein (FAP) associated with the ontogenesis, differentiation and oncogenic transformation of the human exocrine pancreas has been purified from pancreatic juices of patients suffering from pancreatitis or duodenal cancers invading the pancreas [Escribano and Imperial (1989) J. Biol. Chem. 264, 21865-21871]. This protein has striking similarities, i.e. M(r), amino acid composition and N-terminal sequence, to the bile-salt-dependent lipase (BSDL) of normal human pancreatic secretion. The aim of this study was to gain further insight into the nature of the two proteins. Reactivity with the mouse monoclonal antibody J28 (mAb J28), which characterizes FAP, and enzyme activity could not be dissociated during biochemical purification of BSDL. Furthermore, a polyclonal antiserum raised against purified human BSDL reacted completely with FAP in Western-blot analysis giving additional support to the idea of similar molecular structures for BSDL and FAP. However, by the same technique, mAb J28 reacted with a relatively restricted population of BSDL molecules. The classical BSDL preparation could be separated into molecules bearing the J28 epitope and those devoid of it by immunoaffinity on immobilized mAb J28. The two subpopulations had identical N-terminal sequences and some differences in their amino acid compositions. However, they had different carbohydrate compositions. J28-epitope-bearing molecules were active on BSDL substrates, although their specific activity was decreased. These results are consistent with the existence of two closely related polypeptide chains with different glycan counterparts. Therefore, if the name FAP is reserved for molecules bearing the J28 epitope, which is linked to a carbohydrate-dependent structure. FAP could represent an oncofetal-related variant of BSDL. Our result is the first demonstration of the existence of an oncofetal-type subpopulation of an otherwise normally secreted human pancreatic enzyme.

Immunosurveillance by T-lymphocytes in pretumoral stages of chemically induced pancreatic carcinogenesis.

Cellular immune-response during pancreatic carcinogenesis induced by N-nitroso-bis(2-hydroxy-propyl)amine in Syrian Golden hamsters was studied using a mouse antiserum to hamster T-lymphocytes in indirect immunofluorescence. The chronology of lesions in this model is, acinar cell atypia, cystadenoma, ductal hyperplasia and adenocarcinoma. Lymphocyte infiltration began before microscopic lesions. Starting as an interstitial and interlobular migration, this earliest population was composed of various kind of mononuclear cells including T-cells. As pancreatic lesions proceeded, an abundant lymphocyte supply through newly formed capillaries (angiogenesis), gave rise to inter- and intralobular nodules composed almost exclusively of T-cells. Migrating from nodules, T-cells invaded and readily destroyed the exocrine tissue. Formation of hyperplasic ducts and of adenocarcinoma was accompanied by considerable accretion of the basal membrane (fibrosis). T-cells were located outside and around this basal membrane so that they never invaded the ductal epithelium. Our results suggest there is an effective immunosurveillance in the early stages of transformation that becomes ineffective at later stages as a consequence of T-cells' inability to pass through the basal membrane barrier surrounding the ductal epithelium in preneoplasic lesions (ductal hyperplasia) and in adenocarcinoma. Extending our observations to human pancreatic cancer could provide a new insight in cellular immunosurveillance and, as a consequence might, help cellular immunotherapeutic approaches for this almost fatal disease.

Radioimmunolocalization of the monoclonal antibody J28 in early transformation stages in N-nitrosobis(2-hydroxypropyl)amine-induced pancreatic tumors in the Syrian golden hamster.

We describe the in vivo localization of radiolabeled mAb J28, a murine monoclonal antibody characterizing the oncodevelopmental human fetoacinar pancreatic (FAP) protein, at different stages of chemical induction of pancreatic tumors in the Syrian golden hamster. Before doing localization studies in this model, we looked at the cross-reactivity of mAb J28. Semiquantitative dot-blot analysis demonstrated that the antigen recognized in hamster pancreas has an oncodevelopmental expression pattern, while a molecular mass identical to that of human FAP was deduced from sodium dodecyl sulfate/polyacrylamide gel electrophoresis/nitrocellulose immunoblot. 125I-labeled mAb J28 was administered through micro-osmotic pumps to hamsters treated with N-nitrosobis(2-hydroxypropyl)amine (BHP). This was done at three intervals that roughly correspond to the latent period, pretumoral stages, and terminal cancerogenesis in two independent groups of hamsters. Both studies allowed similar results: (a) mAb J28 accumulated almost specifically in the pancreas; (b) maximal accumulation was associated with pleomorphic alterations of the acinar cell tissue at pretumoral stages; (c) no accumulation was found in the case of adenocarcinoma of the pancreas. It is concluded that FAP behaves as a marker of preneoplastic lesions, and therefore that radioimmunoimaging with mAb J28 might help with early diagnosis of pancreatic cancer.

Comparison of carbohydrate and peptide biotinylation on the immunological activity of IgG1 murine monoclonal antibodies.

When the classical amino acid esterification procedure was used for the biotinylation of the IgG1 monoclonal antibody J28 it resulted in a loss of immunological activity. This antibody recognizes the fetoacinar pancreatic (FAP) antigen and the decrease in reactivity was directly proportional to the molar biotin/antibody ratio indicating substitutions at or near the antibody combining site. This effect was specific to J28 since the IgG1 Mab F22 which recognises the same antigen was not damaged by this procedure. Active Mab J28 conjugates were obtained using biotinylation via oligosaccharide moieties. The biotinylation efficiency using this method was dependent on the previous degree of antibody periodate oxidation and the maximal substitution was 3 mol biotin per mol of antibody. Using these conditions the sensitivity of the biotinylated J28 for the FAP antigen was similar to that obtained when using non-substituted antibody in the two antibodies technique.

Expression of fetoacinar pancreatic (FAP) protein in the pancreatic human tumor cell line BxPC-3.

Fetoacinar pancreatic (FAP) protein is a specific component of the human exocrine pancreas that may have a role in the differentiation and transformation of this organ. In order to set out a model for studies on the regulation of FAP, 47 established cell lines from human cancer of different origins were tested for FAP expression using the monoclonal antibody J28 (Mab J28). Only two, both pancreatic, were positive. This finding supports the already reported pancreatic specificity of this antigen. Strongest expression was shown by the BxPC-3 cell line, derived from a moderately well-differentiated adenocarcinoma in the body of the pancreas. In BxPC-3 cells grown in Roswell Park Memorial Institute (RPMI) 1640-10% fetal bovine serum (FBS), Mab J28 immunostaining was localized in the cytoplasm of the cells. In serum-free medium, cells quickly died. Growth and FAP expression were maintained when this medium was supplemented with insulin. FAP is not released to the culture medium, as evidence by absence of reaction with the monoclonal antibody on nitrocellulose dot-blots. On the contrary, a positive reaction was observed in cell homogenates made by sonication or by extraction with 0.1% Triton. A competitive enzyme-linked immunosorbent assay (ELISA), using biotinylated FAP, was developed to quantify the protein in cell homogenates. Concentrations of FAP in homogenates from cells cultured in standard conditions or serum-free supplemented with insulin were in the range of 0.28-0.40 micrograms FAP/mg total protein.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of insulin and somatostatin on the growth and the colony formation of two human pancreatic cancer cell lines.

The effects of insulin and somatostatin on the growth and the colony formation of two human pancreatic cancer cell lines, BxPC-3 and SOJ-6, were studied. The BxPC-3 cell line (American Type Culture Collection no. CRL 1687) was derived from a moderately differentiated pancreatic adenocarcinoma. The SOJ-6 cell line is a subclone of SOJ that was initiated from ascites of a well-differentiated pancreatic adenocarcinoma. Both cell lines express fetoacinar pancreatic antigen, an antigen that might be associated with early transformation stages. However, these lines have different proliferation and tumoral powers. SOJ-6 cells showed an almost twofold higher division rate over BxPC-3 cells when cultured in RPMI-1640 medium containing 10% fetal bovine serum. The tumorigenic degree of SOJ-6 cells, as assessed by tumor growth in nude mice, was about three times greater than that of BxPC-3. The in vitro growth of BxPC-3 cells was significantly promoted by insulin, and was slightly inhibited by somatostatin, whereas the growth of SOJ-6 cells was not influenced by these hormones. Using a clonogenic assay in soft agar, the average ratio of colony numbers formed by SOJ-6 and BxPC-3 was about 10/1, indicating a good correlation between the colony formation and tumorigenic degree in vivo. In this test, the number of colonies formed by BxPC-3 cells was increased about twofold in insulin-supplemented medium. On the other hand, somatostatin inhibited the colony formation by a factor of four to six. However, no hormonal modulation of the colony formation of SOJ-6 cells was observed. Our data show that pancreatic cancer cell lines respond differently to pancreatic hormones, and suggest that this may be correlated to a tumour stage or a tumour type.

An immunohistologic study of the feto-acinar pancreatic protein (FAP) in the normal pancreas, chronic pancreatitis, pancreatic adenocarcinoma, and intraabdominal metastases of adenocarcinomas.

The immunohistologic distribution of the feto-acinar pancreatic protein (FAP), detected by the monoclonal antibody (MoAb) J28 using an indirect immunoperoxidase technique, is described. Tests were carried out on normal adult pancreas (n = 10), chronic pancreatitis (n = 14), pancreatic adenocarcinoma (n = 17), intraabdominal metastases of pancreatic and nonpancreatic origin (n = 22), metastatic tumors invading the pancreas (n = 3), nonpancreatic fetal (n = 39) and adult (n = 65) normal organs (n = 104), and nonpancreatic malignancies (n = 145). All sections were formalin fixed and paraffin embedded. In the normal pancreas, only a few positive acinar cells were found around some islets of Langerhans. In pancreatitis there was an increased expression of FAP protein in the acinar tissue in relation to inflammatory changes. In cases of primary pancreatic adenocarcinoma and metastatic tumors in the pancreas, a strong expression of FAP protein in the peritumoral acinar area was found. The tumors themselves were FAP protein negative, as were the nonpancreatic tumors and normal organs. It can be concluded that FAP protein, detected by MoAb J28 in tissue sections, is specific for pancreatic exocrine tissue with reactive changes.

Purification and molecular characterization of FAP, a feto-acinar protein associated with the differentiation of human pancreas.

This work describes the purification of FAP, a feto-acinar pancreatic protein associated with the ontogenesis, differentiation, and transformation of the human exocrine pancreas. The protein was purified to homogeneity from pancreatic juices of patients with pancreatic pathology by a two-step chromatographic procedure which consisted of size exclusion on Sephacryl S-200 and affinity on heparin-Sepharose. The final preparation gave a single band at Mr 110,000 by sodium dodecyl sulfate-polyacrylamide gel electrophoresis after Coomassie stain or autoradiography of the 125I-labeled protein. Immunodetection with the murine monoclonal antibody mAb J28 in nitrocellulose replicas demonstrated a main Mr 110,000 component and trace components in the Mr 100,000-80,000 range. The immunopattern was identical to that in the original crude pancreatic secretion, therefore showing that the molecular characteristics of the protein, i.e. molecular mass, microheterogeneity, and immunoreactivity, were not altered along the purification procedure. FAP was identified as an acidic protein (isoelectric point 4.2-4.8) consisting of a single polypeptide chain having no free SH residues. Analysis of the amino acid composition showed a high proline content. Twenty-two residues of the N-terminal sequence were determined. No significant homology between this peptide and other proteins was found following a search of the NBRF-18 data bank. Sugar analysis showed the presence of mannose which is consistent with N-linked carbohydrate chains and an unusual high ratio in N-acetylgalactosamine residues suggesting the presence of many O-linked carbohydrate chains. Sequential deglycosylation with neuraminidase, hexosaminidase, and O-glycanase yield a single Mr 58,000 peptide showing that, relative to a molecular mass of 110,000, the carbohydrate moiety of FAP accounts for at least 47% of its apparent Mr by sodium dodecyl sulfate-polyacrylamide gel electrophoresis.

A Mr 58,000 glycoprotein specifically expressed in developing hamster pancreas and reexpressed in hamster and human pancreatic carcinomas.

A glycoprotein with a molecular weight of 58,000 specifically expressed in exocrine hamster fetal pancreas was characterized using a monoclonal antibody (Mab B4). By immunoperoxidase, Mab B4 stained pancreatic tissue from the 10th day of gestation (6 days before delivery) until the 10th day after birth. The maximal expression of the Mab B4-specific protein called fetal pancreatic (FP) protein was reached between delivery and the 5th day of postnatal life. Endocrine pancreas was negative at any developmental stage. All adult pancreata examined were negative. Moreover, Mab B4 was tested against a wide variety of fetal and adult tissues; only immature pancreata were stained. Chemically induced pancreatic carcinomas were strongly stained by this Mab. On the contrary, other tumors (liver and kidney) appearing simultaneously with pancreatic carcinomas were negative. Using a nitrocellulose immunofixation assay, FP protein was found in all sera from hamsters bearing pancreatic tumors (23 cases tested). This protein was not detected in normal sera. Mab B4 cross-reacted with a protein in human fetal pancreas extracts, that behaves similarly to the hamster FP protein: it is present exclusively in exocrine fetal pancreas and is reexpressed in pancreatic adenocarcinomas. The high tissue specificity of this protein, its oncofetal character, and release into the blood circulation make the FP protein a potential tumor marker of pancreatic cancer.

Immunohistochemistry of CEA in the human pancreas during development, in the adult, chronic pancreatitis, and pancreatic adenocarcinoma.

This study describes the immunohistologic distribution of carcinoembryonic antigen (CEA) in 30 fetal pancreata, 5 normal adult pancreata, 11 cases of chronic pancreatitis without carcinoma, 16 cases of chronic pancreatitis with carcinoma, and 20 cases of primary pancreatic adenocarcinoma. The position of CEA-cross-reacting antigen, especially of nonspecific cross-reacting antigen (NCA), was also studied in the case of chronic pancreatitis and pancreatic adenocarcinoma. For this purpose, both monospecific antibodies to CEA and NCA, as well as cross-reacting antibodies, were used in an indirect immunoperoxidase technique. CEA reactivity could not be detected, neither during pancreatic development nor in chronic pancreatitis with or without associated adenocarcinoma. In 15 of 20 pancreatic adenocarcinomas, CEA positivity was found both with membranous and cytoplasmic localization. With the use of the cross-reacting antibodies, all cases of chronic pancreatitis and pancreatic adenocarcinomas showed positive staining of both ductal and tubular structures. Antibodies to NCA closely mimicked the results obtained with the cross-reacting antibodies both in pancreatitis and adenocarcinoma. From the authors' results it can be concluded that CEA is not a developmental antigen of the pancreas. Furthermore, NCA cross-activity of anti-CEA antibodies is an important reason of false positive reaction in chronic pancreatitis. Moreover, true CEA positivity in the pancreas appears to be restricted to adenocarcinoma of the exocrine pancreas.

The diagnostic value of the foetoacinar pancreatic (FAP) protein in cancer of the pancreas; a comparative study with CA19/9.

The serum diagnostic value of the foeto-acinar pancreatic protein (FAP protein), an oncofoetal pancreatic antigen, was tested in 201 patients. Of these, 112 suffered from malignant disease (57 patients had pancreatic carcinoma and 55, extra-pancreatic malignancies) and 89 had benign disease (49 patients with hepato-pancreato-biliary disease and 40 with other benign disease). FAP protein was measured by a competitive radioimmunoassay. In this technique, the normal cut-off level was 10% inhibition. This was deducted from values in 32 normal sera. FAP protein levels superior to 10% inhibition were found in 86% of patients with pancreatic cancer, in 31% with non-pancreatic malignancy, in 69% with benign hepato-pancreato-biliary disease and in 20% with other benign diseases. Accordingly, sensitivity of FAP protein for pancreatic carcinoma was 86% and specificity, 66%. However, high FAP protein levels (greater than 30% inhibition) were almost exclusively seen in patients with pancreatic cancer. At this cut-off level, specificity increased to 95% but sensitivity decreased to 51%. Determination of the carbohydrate antigen CA19/9 was made in parallel by a commercially available assay. At the cut-off level of 37 u ml-1, CA19/9 in our serum panel had a sensitivity of 74% for pancreatic carcinoma and a specificity of 88%. In pancreatic cancer 55 out of 57 patients had elevated levels of either FAP protein or CA19/9 (sensitivity; 96%).

Ultrastructural changes in acinar cells of hamster pancreas in chemically induced carcinogenesis.

Ultrastructural changes arising in the pancreas of the Syrian golden hamster after treatment with N-nitrosobis (2-oxopropyl) amine (BOP) were studied at short intervals. Alterations were found in acinar cells i.e. loss of zymogen granules, dilatation of granular endoplasmic reticulum, depolarization, irregular nucleus and separation of lateral surfaces (intermembranary spaces). As a result, the compact morphology of normal acini switched towards a new structure resembling a pseudo-ductule. Such alterations occurred from the 3rd month and preceded tumor formation. It is noteworthy that ducts and islets of Langerhans appeared unaltered in all instances. These results are consistent with the hypothesis that BOP induced pancreatic adenocarcinoma in hamsters originates in the acinar cell.

Fetoacinar pancreatic protein in the developing human pancreas.

The distribution of the 110-kilodalton fetoacinar pancreatic (FAP) protein was examined in 56 pancreases obtained from human embryos and fetuses (ranging 6 from weeks of gestation to full term) and 10 normal adult pancreases. This recently discovered protein is a concanavalin-A-binding glycoprotein that is specific for acinar cells of the pancreas. Using a murine monoclonal antibody for either immunoperoxidase or immunofluorescence procedures, FAP-protein expression was not found in embryos at less than 9 weeks of gestation. At 9-10 weeks, a clear staining was observed in the terminal portions of dilated buds in primitive pancreatic tubular structures (i.e., the site of the first development of the future acinus). At 11-12 weeks, acinar structuration began, and FAP-protein expression increased as shown by the higher number of stained acini and the greater staining intensity. Maximal expression occurred at 15-22 weeks and then gradually decreased; from 28 to 32 weeks until full term, the pancreas was almost negative for this protein. In the adult pancreases, the protein was either absent or only present in acinar cells surrounding the islets of Langerhans. The pancreatic ducts and endocrine cells remained negative throughout gestation and in adults. FAP-protein thus appears to be a marker of acinar-cell differentiation. Its function remains unknown at present. Its close association with the growth and development of the pancreas together with the fact that, in a previous study, it was found to be re-expressed in pancreatitis and in cancer, suggest that it may play a role in developmental regenerative and neoplastic processes in the pancreas.

Differentiation antigens in fetal human pancreas. Reexpression in cancer.

An antiserum was raised against pancreatic extracts obtained from human fetuses under 5 months of gestational age. After absorption with adult tissues, this antiserum specifically recognized antigens located in the cytoplasm of fetal pancreatic acini. All of the examined pancreatic tissues, ranging from 3 to 5 months of gestational age, showed a strong positive reaction of most of the acinar cells. The number of stained acini and the staining intensity gradually decreased from 5 months onwards and by the 7th-8th month only a few cells remained positive. Adult pancreas was completely negative as were a variety of normal adult and fetal tissues. This antiserum also reacted with tumor structures in 18/18 pancreatic adenocarcinomas as well as with pancreatic acini in the vicinity of tumor. Primary carcinomas of the liver, large bowel, stomach, breast, urinary bladder, lung and other localizations did not react with this antiserum. In some cases of chronic pancreatitis (3/12) a reaction was observed in a few acinar cells. Immunoblot assay after polyacrylamide electrophoresis revealed, in both fetuses and tumors, two main antigens of approximately 60 kDa and 110 kDa relative molecular weight. Several minor components were also observed. These results suggest that our polyclonal antiserum defines a new group of oncodevelopmental antigens with high organ specificity.

Isolation and characterization of two oncofetal glycoproteins from hamster pancreas using concanavalin A and preparative electrophoresis.

Pancreatic fetal acinar antigens in the Syrian golden hamster, which are associated with development of the pancreas, have been previously described. In this study, two major antigens were isolated from fetal pancreas using affinity chromatography on Con A-Sepharose and preparative electrophoresis. Homogenates from fetal and adult pancreas were analyzed for their ability to bind to concanavalin A. This lectin allowed obtention of eluted fractions accounting for 2 and 0.7%, respectively, of the protein content in crude extracts. Concanavalin A-positive fraction from fetal pancreas contained two major carbohydrate-reactive glycoproteins of relative molecular weight (Mr) 80 000 and 58 000 in SDS-polyacrylamide gel electrophoresis. Both behaved as fetal antigens in nitrocellulose blot immunoassay. Similar experiments with chemically induced tumors of the pancreas led to a concanavalin A fraction containing the 80 and 58 kDa fetal glycoproteins; but in this case, the fraction was quite heterogeneous. Our data provide new support for the existence of differentiation antigens in the acinar cells of the pancreas, and indicate that two major ones are glycoproteins. Moreover, both are expressed in pancreatic tumors.

Detection of pancreas pretumoral stage by means of organ transplantation.

Syrian golden hamsters were treated at monthly intervals for three months with N-nitrosobis (2-oxopropyl) amine (BOP) at doses of 20 mg/kg. During the treatment program individual pancreases were analysed by histology and transplanted into syngeneic recipients. Within the first 20 weeks following BOP administration, only a few alterations in the acinar cells were detected histologically. Nevertheless, pancreases taken as early as 10 weeks following the initiation of the chemical treatment produced local tumors at the site of subcutaneous implantation. Tumors thus obtained by graft were noted to be carcinomas of ductal type. Organ transplantation was thus observed to be a good method of detecting early neoplastic transformations in the pancreas which were not seen by conventional histology.

Expression of oncofoetal pancreatic antigens in hamster adult pancreas during experimental carcinogenesis.

Foetal acinar components associated with the development of the hamster pancreas have been previously defined with the aid of an antifoetal pancreas serum. In immunohistology this antiserum also stained malignant ductal cells in N-nitrobis (2-oxopropyl) amine (BOP)-induced pancreatic adenocarcinoma. It did not stain adult pancreas structures including acini, ducts and islets of Langerhans. In this study, re-expression of foetal acinar antigens was disclosed before formation of tumours. Adenocarcinomas were not detected by conventional histology before the 24th week following initiation of the chemical treatment. However, staining with the antiserum was observed from the 7th week appearing in the apex of some acini cells having an almost normal histological appearance. Later, foetal acinar expression was frequently associated with evident morphological alterations in acini like dyskaryosis, enlarged cytoplasm or lumina. Staining of ducts with marked atypical epithelium and (as already reported) of neoplastic ducts was also observed. It was not detected in other pancreatic lesions viz. cystadenomas, mucoid glands and regular hyperplastic ducts. Acinar dedifferentiation as assessed by expression of foetal components preceded formation of tumours in all instances.

Variations in the levels of IgG1 and IgG2 subclasses in the sera of normal, immunized and tumor-bearing hamsters.

The concentration of IgG1 and IgG2 subclasses in the sera of hamsters bearing tumors of different origins were compared to that of normal serum and to that of sera of animals rendered resistant to tumor take by immunization with viable SV40-transformed cells. In the sera of hamsters bearing tumors induced by virus-transformed cells an augmentation of IgG2 and a diminution of IgG1 was observed during the development of the tumor compared to sera of normal hamsters. In the sera of animals bearing tumors induced by methylcholanthrene ( MCH2 ) or by spontaneously transformed cells ( EHB ) the level of IgG2 was almost normal but IgG1 was barely detectable, especially in MCH2 tumors. On the other hand, the sera of animals immunized with virus-transformed cells showed a slight increase in both IgGs, but only that of IgG2 was significant. Antibody activity was tested in the sera as well as in the IgG1 and IgG2 fractions of the sera of hamsters immunized or bearing tumors induced by SV40 transformed cells. Both sera and the subclasses showed antibody activity, the activity being more pronounced in the IgG2 fraction than in the IgG1 fraction.