Production of scatter factor-like activity by a nitrosamine-induced pancreatic cancer cell line

Two hamster pancreatic cancer cell lines, PC-1 and PC1.0, established from N-nitrosobis(2-oxopropyl)amine-induced pancreatic ductal/ductular adenocarcinomas exhibit different growth patterns. PC-1 cells, which produce well differentiated adenocarcinomas in vitro after allogeneic inoculation, form cell aggregates and characteristic island-like structures in vitro. PC1.0 cells, which produce poorly differentiated tumors in vivo, form dispersed colonies in vitro. Conditioned medium prepared from PC1.0 cells inhibits PC-1 cells from forming island-like colonies. The conditioned medium also prevents several human pancreatic carcinoma cell lines, HPAF, CD11 and CD18, from forming compact colonies. These properties are similar to those described previously as scatter factors. The scatter factor-like activity is heat-labile, acid-stable, non-dialyzable, trypsin sensitive and unaffected by reducing agents. The activity is not suppressed by addition of heparin, and it does not bind to heparin. In addition, the scatter phenomenon is not reproduced by acidic or basic fibroblast growth factor, epidermal growth factor or transforming growth factor-beta 1. Based on these findings, it appears that the scattering activity produced by PC1.0 cells differs from the scatter factors that have been identified in other systems.

Modification of antigen expression in human and hamster pancreatic cancer cell lines induced by sodium butyrate

The effects of sodium butyrate (NaB) on the growth, morphology, and expression of blood group A, Lewis(a), and CA 19-9 antigen in the hamster pancreatic cancer cell lines, PC-1 (well differentiated) and PC-1.0 (poorly differentiated), and of blood group A, DU-PAN-2, and CA 19-9 antigens in four human pancreatic cancer cell lines, HPAF and CD11 (well differentiated) and CD18 and PANC-1 (poorly differentiated), were examined. NaB inhibited the growth of all cell lines and induced cell enlargement, an increase in secretory material, microfilaments, and pseudopodia. NaB stimulated the production of blood group A antigen in PC-1.0 cells dose dependently, but no change in the expression of this antigen was observed in the human cell lines. However, NaB treatment increased the presence of cells positive for CA 19-9 in PANC-1 but not in the remaining cell lines, none of which reacted with the anti-CA 19-9 antibody before or after NaB treatment. Untreated PANC-1 cells did not produce either blood group A or DU-PAN-2 antigen, but expressed these antigens after NaB treatment in a dose-dependent manner. The results suggest that NaB stimulates the differentiation of the hamster and human pancreatic cancer cell lines and increases or induces the expression of some tumor-associated antigens.

Relationship between blood group-A antigen expression and malignant potential in hamster pancreatic cancers

The loss of expression of the ABH blood group antigens is suggested to be associated with more aggressive behavior of cancers. We have compared the growth behaviors of two hamster pancreatic cancer cell lines with different blood group-A expressions. PC-1.0 cells, which expressed blood group-A antigen poorly, showed a faster growth in vitro and in vivo when implanted into the pancreas of homologous animals, whereas PC-1.2 cells, all of which express the antigen, had a slower growth rate both in vitro and in vivo. PC-1.0 also tended to metastasize, whereas PC-1.2 cells grew primarily locally. The allografts of both PC-1.2 cells (PC-1.2AG) and PC-1.0 cells (PC-1.0AG) and the metastases of PC-1.0 cells expressed blood group A antigen in a similar rate. There was no significant difference in the number of A-antigen positive cells (A+) between the PC-1.2AG and PC-1.0AG, although the expression of A antigen in PC-1.0AG showed a greater heterogeneity. The combined immunohistochemistry and autoradiography did not show any significant differences in the labeling index of A+ or A- cells between the two allografts. Thus, the results indicate that blood group A antigen expression is unrelated to malignancy in this model. The faster growth rate of PC-1.0 cells may be due to their shorter cell cycle.

Purification and analysis of glycoproteins bearing blood group-A determinants from hamster pancreatic ductal adenocarcinomas

Although the hamster pancreas does not express A, B or H blood group antigens, all hamster pancreatic ductal adenocarcinomas induced by treatment with N-nitrosobis(2-oxopropyl)amine express blood group-A antigen. Thus, the acquisition of blood group-A antigen expression in this system is a cancer-associated alteration. We have purified three major blood group-A antigen bearing glycoproteins (gp120, gp135 and gp150) from hamster pancreatic cancer cell membrane preparations using affinity chromatography on DBA (Dolichos biflorus) agglutinin-agarose. When assayed by immunoblotting, gp120 and gp135 showed strong blood group-A reactivity, which was removed by treating membrane samples with peptide-N-glycosidase F. Blood group-A reactivity was unchanged by treatment of the membrane fractions with endoglycosidases F and H. In addition, these two glycoproteins bearing blood group-A antigen also bound L-PHA (Phaseolus vulgaris leucoagglutinin). These results demonstrate that gp120 and gp135 express blood group-A antigen on Asn-linked multi-antennary complex type glycan structures. The gp150 showed weak blood group-A expression. This is the first demonstration of the neoexpression of cancer-associated blood group-A determinants which reside on Asn-linked glycan structures.

Submandibular gland as a site for islet transplantation

Homologous transplantation of islets of Langerhans into the submandibular glands of Syrian hamsters was successful in 8 out of 10 recipients. The technique was simple and led to formation of islets of various sizes within the parenchyma of the gland. The morphology and endocrine cell patterns of this islets were identical to pancreatic islets. The advantage of this model for islet transplantation is discussed.

Modification of blood group A antigen expression in a pancreatic cancer cell line (PC-1) by inhibitors of N-glycan processing

Pancreatic adenocarcinomas induced in Syrian hamsters by treatment with N-nitrosobis(2-oxopropyl) amine express blood group A antigen, which is absent in normal pancreatic cells. On membrane glycoproteins purified from tumors, blood group A antigen has been found to be expressed on multiantennary Asn-linked complex glycans. In this study, we investigated the effect of inhibitors of Asn-glycan processing on blood group A antigen bearing glycan structures in a cell line (PC-1) established from a primary induced pancreatic cancer. Expression of blood group A antigen on cells and in membrane preparations was blocked by treatment with 1-deoxymannojirimycin, an inhibitor of mannosidase I, but was retained after treatment with swainsonine, an inhibitor of mannosidase II. However, swainsonine treatment altered the glycan structure associated with blood group A antigen from an endoglycosidase H resistant type to a sensitive type, indicating that the blood group A structure might shift from a complex type to a hybrid type glycan by this treatment. These results demonstrate that Asn-linked glycans carry the major blood group A antigens in PC-1 cells.

Immunohistochemical characterization of endocrine cells in experimental exocrine pancreatic cancer in the Syrian golden hamster

Fifty exocrine pancreatic adenocarcinomas and 57 benign tumors induced in Syrian hamsters by N-nitrosobis(2-oxopropyl)amine (BOP) were examined for the presence of argyrophil cells antiinsulin, -glucagon, -somatostatin, -pancreatic polypeptide (PP), -gastrin/CCK, -vasoactive intestinal polypeptide (VIP), and - neuron-specific enolase (NSE) reactive cells. Argyrophil - and antihormone-reactive cells were found in the normal pancreatic ducts and in the acini, as well as in hyperplastic and atypical ducts/ductules, tubular complexes, benign lesions, and in 80% of ductal adenocarcinomas. Insulin and antiNSE-reactive cells were the most common, followed in decreasing frequency by glucagon, somatostatin, and PP cells. Antigastrin-/CCK-and -VIP-reactive cells were found in two cases. Argyrophil cells were present in about 60% of the tumors with Grimelius staining and in 55% of those with Churukian-Schenk staining. Insulin cells were seen in ductal cancer that had grown into a lymph node and in the lymph node metastases of another cancer. A novel finding was the presence of argyrophil and insulin cells within the lumen of some malignant glandular structures. Coexistence of several peptide cells was found in 52% of the cancers. The presence of argyrophil and hormone-producing cells in induced pancreatic ductal/ductular lesions further strengthens the existence of a close developmental relationship between exocrine and endocrine cells of the pancreas.

Cholecystokinin inhibits DNA alkylation induced by N-nitrosobis (2-oxopropyl)amine (BOP) in hamster pancreas

Cholecystokinin (CCK) inhibits pancreatic cancer but not hepatic tumor induction by N-nitrosobis (2-oxopropyl) amine (BOP) in hamsters when administered with or shortly before BOP. In this study, we evaluated the capability of sulfated CCK-8 to inhibit DNA alkylation in the hamster pancreas. We examined the pattern of O6-methylguanine (G6-Me) and N7-methylguanine (G7-Me) in pancreatic ductal, acinar and liver tissues from Syrian hamsters treated with a single dose of BOP (20 mg/kg s.c.) and with five s.c. injections of CCK-8 (200 pM/kg, 30 min apart). The first CCK injection was given either 90 min before, or together, or 3 h after POP administration. The amount of G6-Me in liver DNA did not differ significantly. We observed a decrease of G7-Me in the liver of the group treated with CCK together with POP as compared to POP alone (P less than 0.005). Lower amounts of G6-Me were found in ductal preparations (P less than 0.01) of the animals treated with CCK before POP as compared to POP alone. CCK also modified the pattern of alkylation in the acinar tissue, but without a clear relationship with the timing of administration. The results suggest that the inhibitory effect of CCK-8 on pancreatic carcinogenicity of BOP could be related to its capability to modify DNA alkylation by yet unknown mechanisms.

Pancreatic mixed ductal-islet tumors. Is this an entity?

Thirty-eight human pancreatic cancer specimens were studied for the reactivity of cancer cells with monoclonal antibodies against insulin, glucagon, somatostatin, pancreatic polypeptide (PP), vasoactive intestinal peptide (VIP), gastrin, calcitonin, and with argyrophilic reactivity. Immunoreactivity with one or several antibodies or argyrophilic reactivity were found in 30 (79%) cases. In 17 cases, the number of endocrine cells was excessive and morphologically consistent with the mixed ductal-islet tumor. Although most immunoreactive cells were located at the base of the malignant glands, some had intraepithelial location and were also present in the invasive portion of cancers, indicating their malignant nature. Endocrine cell proliferation were found in the pancreatic tissue adjacent to the carcinoma in 8 out of 12 specimens examined. In these cases, the immunoreactive cells were either distributed among the acinar cells or ductal cells. More endocrine cells were found in the hyperplastic ducts; however, no correlation was found between the degree of hyperplasia and the occurrence of any type of immunoreactive cells. Although several types of endocrine cells occurred in different pancreatic regions (head, body, and tail), PP cells were restricted to tissues taken from the head of the pancreas. Experimental data and similar observations by other investigators led us to conclude that participation of endocrine cells in ductal-type carcinomas is a general phenomenon and does not justify the classification of these lesions to mixed ductal-islet entity. However, because immunoreactive cells were more common and numerous in well-differentiated carcinomas, they may have some prognostic values.

Enhanced levels of annexins in pancreatic carcinoma cells of Syrian hamsters and their intrapancreatic allografts

Annexins are a family of calcium- and phospholipid-binding proteins related by amino acid sequence homology. Annexins I and II are substrates for protein tyrosine kinases. Recent investigations have revealed a possible involvement of annexins I and II in mitogenic signal transduction and cell proliferation. To investigate further the involvement of annexins in cell proliferation, we measured the levels of annexins I and II and the enzyme 3-phosphoglycerate kinase (PGK) (annexin II and PGK are components of the primer recognition protein complex) in normal Syrian hamster pancreas, three hamster pancreatic ductal carcinoma cell lines, and allografts of the three cell lines into hamster pancreas. All three carcinoma cell lines had 5-8-fold higher levels of annexin II compared to normal pancreas. An inverse relationship was seen between level of annexin II and the doubling time of the cell culture. In intrapancreatic allografts, annexin II levels were 3-6-fold higher than in normal pancreas. Annexin I levels were 2-3-fold higher in the allografts. Significant increases (5-6-fold) in specific activity of PGK were seen in all allografts examined. However, the level of PGK, as measured by immunoblotting, was not significantly altered. Immunohistochemical staining revealed heterogeneity in the reactivity of the antiannexin and anti-PGK antibodies with tumor cells. Strikingly, the reactivity and staining intensity were greater in the proliferating regions of the primary tumors and in the metastatic foci. Mitotic cells were either unstained or very weakly stained. We conclude from these findings that annexin II and PGK, as primer recognition proteins, may have a role in cell proliferation.

Effects of high-fat diet on the patterns of prostatic cancer induced in rats by N-nitrosobis(2-oxopropyl)amine and testosterone

Controversial views exist on the link between prostatic cancer and consumption of high-fat (HF) diet. This topic was examined in experimental prostatic cancer induced in rats by N-nitrosobis(2-oxopropyl)amine (BOP). Groups of Wistar-derived MRC rats were fed a semipurified diet containing either 5% (low fat = LF) or 24.6% (HF) corn oil for life, beginning after weaning. In the short-term study, treatment with testosterone significantly increased the rate of cellular DNA synthesis (as determined by autoradiographs after tritiated thymidine injection) that was not influenced by the level of dietary fat. HF diet alone depressed the rate significantly in the dorsal lobe only. There was a significant increase in the plasma level of estradiol, a decrease in the level of luteinizing hormone, but no changes in the level of follicle-stimulating hormone (FSH) in rats treated with testosterone, with no differences between the HF and LF groups. However, HF in the absence of testosterone depressed the serum FSH level. In the carcinogenicity experiment, all rats fed HF or LF diet developed prostatic cancers (mostly adenocarcinomas). The incidence, however, was significantly higher in testosterone-treated rats. Dietary fat did not influence the incidence, histological patterns, or anatomical distribution of tumors, and there were no differences in the parameters between the HF- and LF-fed groups. Long-term administration of testosterone significantly lowered serum levels of luteinizing hormone but did not change the FSH level and affected estradiol levels to a variable extent. These values were not influenced by dietary fat. However, in the HF-BOP group, significantly higher levels of FSH were found compared with the values in the LF-BOP group. We concluded that (a) under the described experimental conditions, dietary fat, fed ad libitum, does not influence the patterns of prostatic cancer induced in rats by BOP; (b) testosterone alters the serum levels of estradiol and luteinizing hormone; and (c) both testosterone and estradiol could be involved in carcinogenesis.

Diagnosis of pancreatic cancer. Alteration of glucose metabolism

Alterations of glucose metabolism occur frequently in association with pancreatic cancer. Whether diabetes predisposes or is a consequence of pancreatic cancer has not been settled. We have found that induced diabetes prevents development of pancreatic cancer in the hamster model and that genetically diabetic Chinese hamsters resist pancreatic cancer induction, whereas the nondiabetic strain does not. Also, preliminary clinical data indicates that diabetes is associated with pancreatic cancer and that the two conditions develop simultaneously. We have found diabetes or impaired glucose tolerance in 76% of the pancreatic cancer patients at the time of cancer diagnosis. The diabetic condition improved after 75% pancreatectomy. Although the preliminary observations suggest that diabetes accompanies the disorder of pancreatic cancer, additional data are needed before any conclusion can be drawn.

The patterns of beta-cell regeneration in untreated diabetic and insulin-treated diabetic Syrian hamsters after streptozotocin treatment

Our previous study showed that Syrian hamsters recover from streptozotocin (SZ)-induced diabetes spontaneously and that insulin therapy adversely affects diabetes. The recovery and lack of recovery was associated with beta-cell regeneration and lack of regeneration. In this study, we examined the patterns of beta-cell regeneration in hamsters by using an immunohistochemical-autoradiographical method. We used tritiated thymidine to examine the DNA synthesis in islet cells and evaluated the number of labeled cells that were or were not immunoreactive with antiinsulin, antiglucagon, and anatisomatostatin. The results showed that, in untreated control hamsters, beta-cell regeneration took place both from preexisting beta cells and from undifferentiated cells (labeled cells unstained with any of the three antibodies) in equal proportions. In the SZ-treated hamsters, however, most regenerating cells seemed to derive from undifferentiated cells within the islets. Insulin therapy inhibited beta-cell regeneration from both the preexisting cells, but more so from the undifferentiated cells. The number of extrainsular islet cell foci was the same in all treatment groups and paralleled the number of islets in each animal during the entire experiment. We concluded the following about diabetic hamsters: 1. beta-Cell regeneration occurs primarily from undifferentiated cells within the islet; 2. Exogenous insulin inhibits beta-cell differentiation from the precursor cells; and 3. The response of intrainsular and extrainsular islet cells to SZ and insulin therapy is similar and the number of extrainsular islet cell foci per pancreas parallel the changes in the number of islets.

Subcellular localization of blood group A substance produced by pancreatic adenocarcinoma induced in hamsters by N-nitrosobis(2-oxopropyl)amine (BOP) and by its cell line (PC-1)

The subcellular localization and biochemical characteristics of blood group A antigen were studied by immunogold methods and by SDS-PAGE and Western blotting procedures in N-nitrosobis)2-oxopropyl)amine (BOP)-induced pancreatic cancer (PC) in Syrian hamsters, in the pancreatic cancer cell line (PC-1) derived from a primary induced pancreatic cancer, and in intrapancreatic and subcutaneous transplants of PC-1 cells. Normal hamster duodenal epithelial cells expressing A antigen were compared with the normal hamster pancreas (lacking A antigen), human PC tissues from patients with blood group A and human PC cell lines. Blood group A antigen was present on the membrane of hamster duodenal cells, but was absent in the normal pancreatic cells. A antigen was localized mainly on the cell membrane of the hamster cancer cells both in vivo and in vitro. Glycoproteins with blood group A specificity were observed by SDS-PAGE and Western blotting procedures in the membrane fraction of PC-1 cells, with a major component of molecular mass of approximately 120 kd. Similar migration patterns were observed in the primary induced PC and in subcutaneous and intrapancreatic transplants of PC-1 cells. Membrane preparations from cell lines derived from two primary pancreatic cancers from patients of blood group A and from human pancreatic cell lines, CD11 and CD18, showed a major A reactive component with a molecular mass similar to that found in the hamster PC cells. These findings suggest that: (i) both the hamster and human PC cells in vitro produce glycoproteins with blood group A specificity of similar molecular masses; (ii) differences exist in the structure of the glycoprotein immunoreactive with the anti-A antigen between the normal and cancerous cells; and (iii) differences exist in the molecular mass of the anti-A reactive substance between hamsters and human PC cells and between tissues in vivo and in vitro.

Correlation between morphology and blood group-related antigen expression in pancreatic tumors induced in Syrian hamsters

Expression of blood group-related antigens (BGRAs) A, B, H, Le(b), Le(x) and Le(y) was examined immunohistochemically in neoplastic and hyperplastic lesions induced by N-nitrosobis(2-oxopropyl)amine in Syrian hamsters to determine a relationship between histological and biological patterns of the lesion and expression of BGRAs. With the exception of papillary ductal cell hyperplasia, A-antigen discriminated between the benign and malignant lesions far better than the other antigens, which showed heterogeneity in the expression of benign and malignant tumors. However, production of A-antigen decreased with the degree of tumor dedifferentiation and was absent in anaplastic regions of tumors. Marked differences were found in the expression of A- and B-antigen in tubular complexes, one of the earliest induced changes, in relation to the type of cells populating these lesions. Overall, B-antigen seemed to be associated more with benign cells than malignant cells. On the other hand, Le(x)-antigen was expressed primarily in the invasive portion of some cancers and seemed to reflect active proliferative processes.

Patterns of growth and metastases of induced pancreatic cancer in relation to the prognosis and its clinical implications

To understand high malignancy of pancreatic cancer, the growth and metastatic patterns of pancreatic cancer induced in Syrian hamsters were examined. In this model, induced tumors resemble the human disease morphologically, clinically, biologically, and immunologically. In the current study, primary-induced cancer and transplants of pancreatic cancer cell line (PC-1) into the SC tissue or pancreas of homologous hosts were used. In the primary-induced pancreatic cancer, perineural invasion was the most common path (88%), followed by lymphogenic (31%) or vascular (2%) metastases. Inoculation of PC-1 cells into the pancreas resulted in 100% tumor take within 3 weeks. Of 19 intrapancreatic allografts, all showed peritoneal invasion, 5 (26%) liver metastases, 3 (16%) lymph node metastases, 17 (89%) perineural invasion, and none vascular invasion. Even microscopic tumors were found to metastasize primarily via perineural spaces. It was also demonstrated, for the first time, that cancer cells take this route to reach distant tissues, including the lymph nodes. Intraductal spreading occurred in both primary cancers and intrapancreatic allografts either continuously or discontinuously. The patterns of discontinuous intraductal tumor expansion imitated tumor multicentricity. Although perineural invasion was the most common feature of primary cancer and intrapancreatic allografts, lymphatic, hepatic, and vascular invasion and metastases usually occurred in advanced cases. Environmental factors seem to influence expansion and metastases, as evidenced by differences in growth and in metastatic patterns between SC and intrapancreatic allografts.

Comparative histopathological findings in the pancreas of cigarette smokers and non-smokers

Although a correlation has been suggested between cigarette smoking and pancreatic cancer, studies on pathological changes in the pancreas of smokers are fragmentary. In the present study we examined histopathologically 73 pancreases obtained by autopsy from 42 heavy cigarette smokers and 31 non-smoker patients. One invasive adenocarcinoma (2 cm in diameter) and three small carcinomas (2-5 mm in diameter) were found in smokers and one small carcinoma in a non-smoker patient. Although the incidence of pancreatic cancer in smokers was higher than in non-smokers, the difference was statistically not significant. Of smokers with pancreatic cancer, 2 had lung cancer, 1 skin cancer, 1 colon cancer and 1 was free of any malignancies. Ductal changes, including mucinous or squamous cell metaplasia and papillary hyperplasia, were found with equal frequencies in both groups of patients. The type and the incidence of these ductal alterations were not related to smoking but to the age. Our results do not indicate that cigarette smoking increases the incidence of pancreatic cancer, although, the limited number of the sections of the pancreas examined, as well as exclusion of other important variables, such as alcohol, diet and diabetes weaken the value of this study.

Comparative studies on expression of tumor-associated antigens in human and induced pancreatic cancer in Syrian hamsters

The expression of blood-group-related antigens (BGRAs) in experimental primary pancreatic cancer induced by N-nitrosobis(2-oxopropyl)amine (BOP) treatment of Syrian hamsters and homologous subcutaneous transplants of this primary cancer in the cell line, PC-1, established from the primary cancer and intrapancreatic transplanted PC-1 cells were studied by histochemical and biochemical methods. Human primary pancreatic cancer; the human pancreatic cancer cell line, HPAF; and its subclones, CD11 and CD18, also were studied on a comparative basis. Histochemical analysis of BGRAs demonstrated that A, B, H, Leb, Lex, Ley, and T antigen were expressed both in vivo and in vitro in hamster and human materials in similar patterns. However, Lea, CA 19-9 and sialylated Tn antigens were not found in hamster-derived tissues. SDS-PAGE and Western blotting procedures using anti-A antigen revealed similar major bands in the membrane fractions of both human and hamster pancreatic cells between 97 and 200 kdalton. Among other human pancreatic cancer-associated antigens, TAG-72, CA 125, and 17-1A were detected immuno-histochemically in the hamster tumors both in vivo and in vitro, in a pattern similar to that seen in human pancreatic cancer. Tumor antigen DU-PAN-2, associated with human pancreatic cancer, was found infrequently in hamster pancreatic cancer specimens. These results indicate that the experimental hamster pancreatic cancer model provides a unique tool for investigating antigenicity of pancreatic cancer, particularly in relation to diagnosis and therapy.

Comparative studies on the expression of gastrointestinal-cancer-associated antigen, PA8-15, CA19-9 and the blood-group antigens in non-malignant and malignant human pancreatic tissues

The expression of PA8-15 antigen and the blood-group-related antigens A, B, O, Le(a), Le(b), Le(x), and Le(y), as well as CA19-9, were examined in the normal pancreas and in specimens from benign and malignant pancreatic tissue by the avidin-biotin-immunoperoxidase technique. A correlation was found between the expression of PA8-15, Le(a), and CA19-9 in some cases. However, in the cancer tissues in which neither Le(a) nor CA19-9 could be demonstrated, strong expression of PA8-15 was observed. The reactivity of monoclonal antibody (mAb) PA8-15 with pancreatic cancer tissue was not inhibited by the preincubation of the sections with the mAb anti-Le(a) (CO514) and mAb CA19-9 (CO19-9) indicating that the epitope recognized by PA8-15 is different from that detected by the other two antibodies. Moreover, unlike Le(a) and CA19-9, PA8-15 was also expressed in cancer cells of patients of the Le(a-b-) type. The results suggest that mAb PA8-15 recognizes a sialylated molecule related to Le(a) but different from CA19-9, and seems to be an additional useful marker for pancreatic cancer.

Insulin therapy prevents spontaneous recovery from streptozotocin-induced diabetes in Syrian hamsters. An autoradiographic and immunohistochemical study

Streptozotocin (Sz) given as a single dose of 50 mg/kg body wt. caused severe diabetes in Syrian hamsters. However, the level of blood glucose decreased gradually after 21 days post-Sz and reached the near normal level at 70 days in 90% of hamsters. The recovery from diabetes was associated with the regeneration of the beta-cells of islets and a reduction in the initially increased number of alpha- and delta-cells. Daily treatment of diabetic hamsters with insulin was associated with the persistence of severe diabetes, lack of or minimal tendency for beta-cell regeneration and sustained hyperplasia of alpha- and delta-cells in 90% of hamsters. Insulin also inhibited DNA synthesis (as measured by incorporation of tritiated thymidine), in ductal, ductular and acinar cells in Sz-pretreated hamsters but not in normoglycemic control hamsters treated with insulin alone. The results demonstrate a deleterious effect of exogenous insulin in the course of Sz-induced diabetes in hamsters.

Comparison of the effects of dietary beef tallow and corn oil on pancreatic carcinogenesis in the hamster model

We previously reported an enhancement of pancreatic carcinogenesis induced by N-nitrosobis(2-oxopropyl)amine (BOP) in hamsters fed diets containing high levels of corn oil. The research presented here compared diets high in corn oil with those high in beef tallow in the enhancement of pancreatic carcinogenesis. Pancreatic cancer was induced with 20 mg BOP/kg body wt, s.c. administered at 8 weeks of age. One week later, hamsters were assigned to one of five diet treatments: (i) 4.3% corn oil (control); (ii) 20.5% corn oil (high corn oil); (iii) 0.5% corn oil + 3.8% beef tallow (low beef tallow); (iv) 0.6% corn oil + 19.9% beef tallow (high beef tallow); and (v) 5.1% corn oil + 15.4% beef tallow (high fat mixture). These diets were fed until the study ended 84 weeks after BOP treatment. Hamsters were trained through pair feeding to consume the same calorie allotment as the control corn oil group. By the end of the experiment, BOP-treated hamsters that were fed diets containing beef tallow were consistently heavier than those fed corn oil. Survival was longer in hamsters fed the high-beef tallow and high-fat mixture compared with the other diet groups. Tumor data were age adjusted to correct for survival differences. Pancreatic adenoma incidence and multiplicity (no./effective animal) were higher in hamsters fed beef tallow than those fed corn oil diets. Carcinoma in situ multiplicity was elevated in hamsters fed high-fat diets irrespective of the nature of fat fed. Pancreatic adenocarcinoma multiplicity was elevated in hamsters fed the low- or high-beef tallow diets compared with the low- or high-corn oil diets. The mixture of fat resulted in an intermediate yield.

Induction of multifocal pancreatic cancer after inoculation of hamster pancreatic cancer cell line (PC-1) into a defined area of homologous pancreatic tissue

Inoculation of the pancreatic cancer cell line PC-1 into a defined area of the tail of the hamster pancreas led to development of multiple cancerous foci in the body of the pancreas along the main pancreatic duct. Each carcinoma showed identical histological characteristics and was completely separated from the others by regions of normal pancreatic tissue. This observation suggests spread of the cancer from the primary site in discontinuity through the ductal system of the pancreas.

Blood group antigen expression in developing pancreas and in induced pancreatic cancer cells in Syrian hamsters

Expression of blood group-related antigens and the binding pattern of Ulex europaeus-I (UEA-I) in fetal and newborn hamster pancreases was examined immunohistochemically by monoclonal antibodies (MoAbs) against blood group antigens and by peroxidase-conjugated UEA-I. The fetal hamster pancreas was detected histologically at the 12th day of gestation. MoAbs A, B and Le(a) were not immunoreactive with pancreatic cells in any stage of development nor were they after birth. Le(x) was first expressed in the luminal surface of duct cells at the 13th day of gestation, disappeared at the 15th day of gestation, was re-expressed after birth in acinar cells and was absent in the adult pancreas. Le(b) and Le(y) were expressed in acinar cells in late fetal and early newborn stages, but disappeared with maturation and were absent in the adult pancreas. UEA-I binding, however, was demonstrated in both fetal and adult pancreatic tissue. In cancer cells induced by BOP, blood group antigens except for Le(a) and UEA-I binding were found in various reactivity. These findings suggest that in hamsters (i) A and B antigens are tumor-related antigens; (ii) H, Le(b), Le(x) and Le(y) are oncofetal antigens; and (iii) fucosylation is an important event in cell differentiation.

Long-term persistence of DNA alkylation in hamster tissues after N-nitrosobis(2-oxopropyl)amine

The persistence of 7- and O6-alkylation of guanine in DNA of cell nuclei of male Syrian hamster pancreas, liver, kidneys, lungs [target tissues of N-nitrosobis(2-oxopropyl)amine (BOP)] and salivary glands (nontarget tissue) was studied immunocytochemically 6 h, 1, 3, 7, 14, 28, and 56 days after a single s.c. injection of 20 mg BOP/kg. Conventional antisera raised against O6-methylguanine and imidazole-ring-opened 7-methyl-guanine were used. Persistent alkyl-specific staining was observed for up to 7 days (7-alkylguanine) or 56 days (O6-alkylguanine) in inter- and intralobular duct cells and centro-acinar cells of the pancreas, periportal hepatocytes and bile duct cells of the liver, cells of the proximal convoluted tubules of the renal cortex, and bronchiolar Clara and alveolar cells in the lungs. Both adducts disappeared from centrilobular liver cells within 1 day, from pancreatic acinar cells within 3 days, and from ducts and acini of the submandibular salivary glands within 14 days after BOP treatment. A high level of persistent O6-alkylation of guanine was related with a high tumor incidence only in case of the ductal/ductular system of the pancreas, the main target tissue of BOP-induced carcinogenesis. The relatively weak carcinogenicity of BOP in other tissues with long-term persistence of O6-alkylguanine in DNA indicates that the formation and persistence of DNA alkylation are not sufficient to account for the carcinogenic organotropism of BOP. Additional factors, such as cell proliferation, appropriate promoting stimuli and the (onco)genes critically involved, may be as important as the modification of DNA.