Sensitivity and resistance of human tumor cells to interferon and rIn . rCn.
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Biomedical subjects
Publications and source records attributed to W A Carter.
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Resting Burkitt's lymphoma cells (Daudi) in culture are more sensitive targets for the antiproliferative activity of purified human fibroblast interferon than cells that are rapidly multiplying. Thus, interferon may be of significant clinical value in neoplasms involving stem cells and, after chemotherapy, in suppressing the reemergence of tumors.
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A 23 year old woman with chronic active hepatitis documented by liver biopsy demonstrated persistent hepatitis B surface antigen, hepatitis B virus specific DNA polymerase hepatitis B core antigen (HBcAg), for approximately one year. The number of circulating T lymphocytes that rosetted with sheep erythrocytes was decreased, and a rosette-inhibitory factor was present in her peripheral blood. Interferon treatment (1 X 10(6) U/day intramuscularly for 82 days) resulted in a decrease of HBsAg and disappearance of HBcAg, (HBeAg) and specific DNA polymerase. In addition, the number of T lymphocytes increased to normal, and the rosette-inhibitory factor disappeared from the circulation. These findings suggest that the effect of interferon in chronic active hepatitis is mediated in part through its action on the immune system.
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Human interferon from normal diploid fibroblasts, purified by sequential chromatography on concanavalin A-agarose and phenyl-sepharose, was administered parenterally in 4 subjects. Fever, marked skin hypersensitivity reactions and suppression of marrow stem cells (estimated by the count of myeloid colony-forming cells), side-effects common for less purified fibroblast and leukocyte interferons, were absent. Purified fibroblast interferon retained antiviral and immunomodulatory activity, evidenced by reduction of the blastogenic response of peripheral lymphocytes and decrease of hepatitis B virus markers in a patient with chronic hepatitis B infection treated with this substance.
Some of the human prostatic cells in culture apparently produce oncornavirus-like particles. Bromodeoxyuridine does not enhance the production of these particles. On the contrary, this drug depresses such production. This depression is likely to be due to the cytotoxic effects of bromodeoxyuridine for these cells. These results can be interpreted to suggest that the human prostatic cells used in this study do not contain endogenous oncornavirus genetic information that is inducible. Purified human interferon inhibits the production of oncornavirus-like particles by these prostatic cells. It is also inhibits the rate of cellular DNA synthesis in these cells. These results are consistent with the notion that the inhibitory effects of interferon are mediated through its effect on cellular biosynthetic machinery.
Explant cultures from several human prostatic tissues have been examined for oncornavirus production. Some of these explants, epithelial in morphology, appear to release oncornavirus-like particles. The extracellular particulate material, obtained from the culture medium of these explants display the following characteristics: (1) It contains particles that band at a density of 1.1-1.2 g/cm3 in a sucrose density gradient. (2) The particles contain RNA-directed DNA polymerase. This polymerase utilizes poly(Cm) as a template and shows preference for poly(A) over poly(dA) and manganese over magnesium. (3) Apparently, the particles also contain RNA that directs the synthesis of DNA in vitro. The DNA thus synthesized is associated with RNA, some of it with high molecular weight RNA. Such particles are not observed in the culture medium from monolayers of monkey kidney CV-1 cells. We have found that explant cultures from 5 out of 15 tissue specimens with prostatic hyperplasia and 3 out of 4 with prostatic adenocarcinoma release particles that band at a density of 1.1-1.2 g/cm3 and contain RNA-directed DNA polymerase. Explant cultures of two normal prostates examined did not release such particles.
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Interferon, a glycoprotein with demonstrated antitumor and antiviral properties, can be obtained from cells of different species, and some of these interferons can be effective across species lines. I hypothesize that the ability to cross or not to cross species lines lies in the carbohydrate moiety, and cross-species biological activity is a property of the polypeptide. This would represent one of the first major roles uncovered for glycosylation in any biological system. If this hypothesis is correct, then it should be possible to use animal-derived interferon as a large scale, inexpensive source to treat human diseases.
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Human immune interferon, induced in leukocytes by phytohemagglutinin, was prepared in the absence and presence of tunicamycin, an antibiotic which selectively inhibits the glycosylation of newly synthesized glycoproteins. Interferon preparations, produced in the absence of the antibiotic, displayed a considerable chromatographic heterogeneity on: (a) concanavalin A-agarose, (b) phenyl-agarose, (c) Cibacron Blue F3GA-agarose, and (d) polyuridylic acid-agarose. This heterogeneity was completely eliminated when tunicamycin (2 microgram/ml) was present during induction of interferon; all activity was then recovered in the breakthrough fractions from all sorbents. The level of interferon activity in leukocyte culture fluid was not affected by tunicamycin within the range of concentration 0.05 to 2.0 microgram/ml. These data indicate that (a) human immune interferon undergoes glycosylation, and tunicamycin is an effective inhibitor of this process. Thus, it appears that (b) at least some of the carbohydrates of human immune interferon are N-glycosidically linked. Moreover, it seems that (c) glycosylation is not necessary for an interferon molecule to either be secreted by the cell or (d) to express its antiviral function. Such properties of human immune interferon as (e) the apparent hydrophobicity and (f) an affinity for a polyribonucleotide are conferred only when its glycosylation is unimpaired.