Modulation of enzymatic activities during spontaneous and induced differentiation in a human pancreatic adenocarcinoma cell line CAPAN-1

Different enzymatic activities were studied in the human pancreatic cancer cell line CAPAN-1 in order to analyze their relation to differentiation. Alkaline phosphatase (Alk Ph), acid phosphatase, aminopeptidase, dipeptidyl peptidase IV, acid and neutral alpha-glucosidases, and acid beta-galactosidase were present. Especially alkaline phosphatase, which we have found to be of the placental type isoenzyme, is being highly expressed. Spontaneous cell differentiation at confluence as well as differentiating agents: sodium butyrate and DMSO, modulated the levels of three enzymes: Alk. Ph., aminopeptidase, and acid alpha-glucosidase. The exposure of the cells to the differentiating agents amplified the modulations occurring during the spontaneous differentiation. Aminopeptidase and acid alpha-glucosidase were found to be induced by differentiation. Alk Ph specific activity was significantly increased by the spontaneous and the butyrate-induced differentiations; whereas DMSO exerted an opposite effect, probably related to its biphasic action on cell proliferation.

Lipid content of human and rat pancreas

We analyzed the lipid composition of the human pancreas and performed a parallel study on rat pancreas. Some precautions were taken in order to keep the secretory zymogens as inactive precursors in both tissues. The lipid content of the human pancreas corresponded to 5.5% of the tissue wet weight, lower than that found in pancreas of two-month-old Wistar rats (10%). In man, triglycerides and phospholipids were found at comparable levels, respectively, 37 and 30 mg/g of pancreas wet weight, not far from the values of the rat pancreas. In human pancreas, phosphatidylcholines and lysophosphatidylcholines represented about 40% of the total phospholipid fraction, phosphatidylethanolamines and lysophosphatidylethanolamines 21%, and phosphatidylserines and -inositols were found equally represented with 7.5%. The total cholesterol content accounted for about 4.5% of the total lipids; only 30% was esterified. By comparison, in rat, total cholesterol represented 3.3% of lipids and 90% was esterified. The phospholipids in human pancreas contained high amounts of saturated fatty acids (92%) mainly stearic and palmitic, whereas triglycerides contained equal amounts of saturated and unsaturated fatty acids, principally represented by oleic and palmitic acids. In rats the phospholipids contained only 63% saturated fatty acids (palmitic and stearic) and triglycerides contained 61% unsaturated fatty acids (mainly oleic and linoleic). In terms of lipid composition, there is a greater similarity between human and rat pancreas than with other known pancreas, such as the guinea pig and the ox.

VIP regulation of a human pancreatic cancer cell line: Capan-1

VIP and secretin control the secretory function of the normal pancreas. We analysed their regulatory functions in a human pancreatic cancer cell line: Capan-1. Saturation binding experiments with 125I-VIP showed the existence of one class of binding sites of very high affinity: KD 6.4 +/- 3.0 X 10(-11) M and a low Bmax: 12 fmoles/10(6) cells, in both intact cells and membrane preparations. This site has not yet been described in normal or tumorous digestive cells. Competition binding experiments let us characterize two more binding sites, KD: 2.1 +/- 0.7 X 10(-9) M and 5.0 +/- 0.6 X 10(-8) M and the corresponding Bmax: 120 and 500 fmoles/10(6) cells. These sites are similar to those found on cells of the digestive tract. Competition binding experiments gave the following IC50: 3.0 +/- 0.9 X 10(-9) M for VIP; 2 +/- 0.6 X 10(-6) M for PHI; and 1 +/- 0.7 X 10(-5) M for secretin. VIP elicited a cAMP rise, the half maximal response being obtained at 1.2 X 10(-10) M. Secretin induced a cAMP response but only for concentrations higher than 10(-8) M. VIP receptors were found to be modulated by two factors: cell ageing and cell density. Cells chronically treated with VIP showed a slight decrease of their proliferation; insulin exerted an opposite effect. It is concluded that at the difference of normal pancreatic cells, the present cell line lacks secretin-preferring receptors and acquires some of the properties of intestinal cells.

Dopamine receptors in a human colonic cancer cell line (HT29). Some receptor-related biological effects of dopamine

The presence of dopamine receptors in normal colonic cells has been postulated from physiological studies. The existence of such receptors in human colonic tumor cells and their role in tumor progression are still unknown. The aim of the present work was to characterize the dopaminergic receptors in a human colonic adenocarcinoma cell line (HT29) and to evaluate the effect of dopamine on cAMP, protein and DNA synthesis. The binding characteristics of 3H-dopamine on the tumor cells were rapid, reversible, specific, saturable and stereospecific. The first site characterized corresponds to a D3 subtype:KD 3.09 nM, insensitive to sulpiride, unrelated to adenylate cyclase. Competitive inhibitions of 3H-dopamine binding by different drugs showed the existence of a second binding site, D1, with an apparent affinity for dopamine of 6,700 nM. The rank order of potency of inhibitors of 3H-dopamine binding was: haloperidol greater than dopamine greater than cis flupenthixol greater than (+) butaclamol greater than (-) butaclamol greater than trans flupenthixol greater than isoproterenol greater than clonidine greater than prazosin. D3 binding sites are modulated with age, Bmax was 116 fmol/10(6) cells on the 5th day and decreased to 8.2 fmol/10(6) cells on the 15th day of culture. Cell culture in serum-deprived medium allowed an increase in the number of high-affinity receptor sites. D1 sites are coupled to adenylate cyclase as shown by a dose-dependent cAMP accumulation from 10(-8) M to 10(-5) M dopamine concentrations. Interacting with D1 sites, dopamine evokes an increase in protein synthesis with no modification of 3H thymidine incorporation. The present results indicate that the human colonic cancer cell line HT29 exhibits dopamine receptors and that stimulation may induce metabolic modifications in the tumor cells.

[Inhibition of the adherence of leukocytes labelled with Cr-51 in colorectal cancer]

The leukocyte adherence inhibition test (LAI) is an in vitro test of immunity. Its high sensitivity in early cancer and its organ-specificity are of great interest in the study of human tumors. We developed an isotopic method (51Cr-LAI) for colorectal cancer, which has the advantage of being easier to perform than optic-counting assays. 87 patients (35 colorectal cancers, 29 benign diseases, 23 cancers of non-colorectal origin) were studied. We obtained a statistically significant difference between the mean LAI index for colorectal cancers and that for controls (p less than 0.01). LAI values greater than 13 p. 100 were considered positive. The specificity of the test was 94 p. 100 and the sensitivity for all colorectal cancers was 66 p. 100 with the highest value in the Dukes A group (LAI = 83 p. 100). Tests were negative in disseminated neoplasms. The actual fields of interest of LAI in tumor immunology and clinical research are discussed.

Differentiation features of human pancreatic tumor cells maintained in nude mice and in culture: immunocytochemical and ultrastructural studies

A poorly differentiated human pancreatic adenocarcinoma was maintained in nude mice for more than 3 years. When tumor fragments from xenografts were cultivated in suspension, some became adherent, allowing cell culture. Cytochemical, immunocytological and ultrastructural methods were used to study cell differentiation in both solid tumors and cultures. Pancreatic differentiation features such as cell polarization, production of secretory granules, and M1 and M3 mucus-associated antigens were maintained in the tumor cells, in vivo and in vitro. Moreover, in long-term cell cultures, cells were able to organize themselves spontaneously into duct-like structures. Other differentiation features such as production of pancreatic enzymes and hormones were not expressed. However, differentiation patterns such as an intestinal-like brush border and the presence of the M3 antigen associated with intestinal mucus were observed in both xenografts and cultures. This study shows the possible differentiation patterns which can be expressed by the hypothetical tumor pancreatic stem cell in nude mice as well as in culture.

Presence of VIP receptors in a human pancreatic adenocarcinoma cell line. Modulation of the cAMP response during cell proliferation

It is known that the human exocrine pancreas responds to secretin stimulation more than does VIP, a structurally related peptide. We looked for the receptors for those polypeptides in a human pancreatic cancer cell line grown in culture and in nude mice. By analysing the cAMP responses and the 125I-VIP binding we found VIP receptors with a KD of 1.5 10(-9) M. Secretin stimulates the adenylate cyclase through the VIP receptor sites with a KD of 1.7. 10(-6) M. We noted also that during cell proliferation in culture there was about a 5 fold increase of the cAMP response to VIP.

A non-secretory phospholipase A2 in the rat pancreas

The rat pancreas shows a phospholipase activity in the absence of the tryptic activation of the zymogens. We verified that this activity was not due to the zymogen of the secretory phospholipase. Indeed unlike the prophospholipase, the enzyme responsible for the spontaneous phospholipase activity shows a higher catalytic rate at substrate concentrations higher than the critical micelle concentration. This enzyme has a positional specificity of the A2 type and possesses a molecular weight of about 9,500.

The quantitative distribution of certain enzymes along the small intestine of the rat and its correlation with the villous area and the Paneth cells

The distribution of lysozyme, alkaline phosphatase, aminopeptidase, maltase and amylase was studied throughout the small intestine of the adult rat. Lysozyme activity increases along the length of the small intestine and the behaviour of this enzyme slightly differs from the mucosal enzymes reported in this investigation. A positive correlation is found between the percentage of crypts with granulated Paneth cells and the lysozyme activity. This corroborates with the secretory origin of this enzyme from these intestinal cells.

[Spontaneous phospholipase A activity of rat pancreatic homogenates]

Rat pancreas presents a spontaneous phospholipase A activity which appears before trypsin activation at optimal pH 6.5. The responsible enzyme is independent of pancreatic prophospholipase A, as can be seen through experiments done in the presence of trypsin inhibitors. On the other hand, this enzyme is distinct from excretory phospholipase which is more active and whose optimal pH is 8.8. Thermostability and insensibility of spontaneously active phospholipase A to DFP differentiate it from lipase, carboxyl-esterhydrolase and lysophospholipase, respectively.

Support for the medical profession among the aged

National survey data are utilized to delineate areas of confidence among the aged in the medical profession. Four key specifying variables were used in the analysis-race, sex, socioeconomic status, and size of community. Findings indicate that confidence in medical leaders is lowest among that group which in past studies has been found to visit the doctor most often: the elderly of low socioeconomic status. This finding suggests that improvement in the medical care received by the aged could be an important first step in restoring the elderly's confidence in medical leaders.

Calcium and pancreatic secretion-dynamics of subcellur calcium pools in resting and stimulated acinar cells

1 Pulse-chase experiments were carried out on pancreatic tissue lobules incubated in vitro, with 45Ca as the tracer, in order to shed some light on the functional significance of the calcium pools associated with the various cell organelles of the acinar cell, especially in relation to stimulus-secretion coupling. 2 The kinetics of tracer uptake and release which were observed in the intact lobules suggest the existence of a number of intracellular pools, whose rate of exchange is slower than that across teh plasmalemma. 3 The various subcellular fractions accumulate the tracer in different amounts: some (rough microsomes and postmicrosomal supernatant) showed little radioactivity and some (smooth microsomes and zymogen granule membranes) were heavily labelled; mitochondria and zymogen granules showed intermediate values. 4 The fractions are heterogeneous also in relation to the time course of uptake and release of the tracer: in rough and smooth microsomes and, especially, in the postmicrosomal supernatant both rates were fast; zymogen granules and zymogen granule membranes showed slow rates of uptake and little release during chase; intermediate rates were found in mitochondria. 5 In agreement with previous findings we observed that in 45Ca preloaded lobules, stimulation of secretion (brought about by the secretagogue polypeptide caerulein) results in an increase of the tracer release which seems to be due primarily to the rise of the intracellular concentration of free Ca2+ and to the consequent increase of the transmembrane Ca2+ efflux. Among the cell fractions isolated from stimulated lobules only the mitochondria exhibited a significantly lower 45Ca level relative to the unstimulated controls. 6 It is concluded that, of the organelle-bound calcium pools, that associated with the mitochondria might be involved in the regulation of the calcium-dependent functions, including stimulus-secretion coupling; the calcium associated with the zymogen granule content probably has a role in the architecture of the organelle and in the functionality of the pancreatic juice, while the calcium bound to the membrane of the granules might be concerned with the regulation of its permeability properties.

The participation of the black aged in voluntary associations

Racial differences in membership in and attendance of voluntary associations were analyzed for comparable samples of 753 black and 260 white residents of Philadelphia age 65 and over. A hypothesis suggesing aged blacks have higher rates of participation than aged whites was derived from the literature and tested by regression analysis. Potentially confounding variables, e.g., health and socioeconomic status, were entered into the regression equation as controls. The results of the regression analysis indicated the black aged belonged to more associations than the white aged and had higher rates of attendance. Examination of findings previously reported by Kent and Hirsch (1972) indicates part of the difference is due to the greater participation of aged blacks in church-related groups. Implications of the findings are briefly discussed.

Calcium and pancreatic secretion. I. Subcellular distribution of calcium and magnesium in the exocrine pancreas of the guinea pig

The distribution of calcium and magnesium has been studied in the acinar cells of the pancreas of the guinea pig. Most of the magnesium was found to be associated with the rough microsomes (probably bound to the ribosomes) and with the postmicrosomal supernate. In contrast, calcium was distributed among all the particulate fractions, primarily the mitochondria, microsomes (especially smooth surfaced), zymogen granules, and the plasmalemma, and was low in the postmicrosomal supernate. Most of the calcium recovered in the particulate fractions was found to be membrane bound. The highest concentrations were found in the membranes of the zymogen granules and in the plasmalemma. By means of control experiments using -45Ca as the tracer, it was established that a considerable redistribution of calcium occurs during homogenization and cell fractionation. At least some of the resulting artifacts were estimated quantitatively and the data were corrected accordingly. The biochemical results were confirmed with the cytochemical antimonate technique carried out on the tissue as well as on isolated fractions. The role of calcium associated with the zymogen granules and with their limiting membranes is discussed in relation to the architecture of the granule and to the functionality of the pancreatic juice.

Secretion of calcium in pancreatic juice

1. The orgin of the calcium secreted by the pancreas has been investigated in vivo in the guinea-pig by a study carried out in parallel (a) in the juice secreted in response to the injection of either secretin or caerulein and (b) in the pancreatic tissue and in cell fractions isolated thereform. 2. In agreement with previous findings we observed that the concentration of calcium is low in the secretin-stimulated and high in the caerulein-stimulated juice. In the latter calcium and protein are proportional (cal0 n-mole:mg). 3. After I.V. injection of 45Ca the radioactivity decreases rapidly and quasi-exponentially in the blood plasma. A roughly parallel time course is found in the secretin-stimulated juice: the evolution of the juice: plasma radioactivity ratio resembles that observed with the extraceullar space marker [3H]D-sorbitol. In contrast, the time course of 45Ca in plasma and caerulein-stimulated juice are not proportional: the high levels characteristic of this juice are reached several minutes after the injection and maintained thereafter. This increase is followed ca. 50 min later by the appearance of the newly synthesized [3H]L-leucine-labelled proteins. 4. The pancreatic tissue is rich in calcium which is localized primarily in zymogen granules (Ca.36 n-mole:mg protein) and mitochondria; the soluble cytoplasm is low in calcium. 5. The injected 45Ca accumulates in zymogen granules faster than [3H]L-leucine-labelled proteins. The 45Ca:protein ratio of these organelles is considerably lower than that of the caerulein-stimulated juice. 6. It is concluded (a) that calcium is secreted in to the pancreatic juice in two fractions, one (possibly released by simple diffusion) associated with the electrolyte component, the other with protein of the juice, (b) that zymogen granules are the major, but not the only source of the latter fraction, and (c) that the zymogen granule-associated calcium joins the exportable proteins some time after their synthesis, possibly in the Golgi complex and/or in the condensing vacuoles.