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Biomedical subjects

J K Willson

Publications and source records attributed to J K Willson.

At least 91 records · Page 5Linked to original sources
PubMed1989

Methotrexate and dipyridamole combination chemotherapy based upon inhibition of nucleoside salvage in humans.

We have carried out a clinical trial in 23 patients to determine whether dipyridamole modulates the clinical effect of methotrexate. This trial was based upon in vitro studies which indicate that dipyridamole potentiates the cytotoxic action of methotrexate through inhibition of thymidine salvage. Methotrexate was given as a bolus injection 24 h after initiation of a high dose dipyridamole infusion. The trial was designed so that methotrexate was escalated in individuals until toxicity occurred and then the methotrexate dose resulting in toxicity was repeated without dipyridamole. During the course of this study the methotrexate dose was escalated from 10 to 130 mg/m2. While individual patient tolerance varied, moderate to severe myelosuppression and/or mucositis occurred frequently in patients receiving the combination with methotrexate doses greater than or equal to 60 mg/m2. Ten of 10 patients who experienced moderate or severe toxicity with the combination had significantly less toxicity when treated with methotrexate alone. Dipyridamole did not increase toxicity by an alteration in methotrexate elimination. The potentiation of methotrexate by dipyridamole in these patients suggests that physiological thymidine levels are sufficient to perturb the clinical effects of methotrexate and that thymidine salvage may represent a mechanism for clinical resistance to methotrexate. These results also suggest that a high dose dipyridamole regimen can be used as a pharmacological approach to test the role of nucleoside membrane flux on the clinical action of other standard chemotherapeutic drugs. Phase II studies testing the clinical efficacy of this combination should use a methotrexate dose of 60 mg/m2 with a provision for methotrexate dose escalation based upon individual patient tolerance.

Antineoplastic Combined Chemotherapy Protocols↗
PubMed1989

Biology of large bowel cancer.

The progression of large bowel cancer from the colon crypt cell involves a series of sequential stages of altered growth regulation. An increase in the proliferative compartment of the colonic crypt characterizes the earliest stage. This is followed by loss of normal maturation and gain of more autonomous growth. Ultimately, cells that acquire the capability to migrate and grow at a distant site appear as metastases. Clinical and pathologic observations have been used to identify these stages of large bowel cancer progression, but only with the recent application of molecular and biologic tools are we beginning to identify potential mechanisms responsible for the altered growth. The development of laboratory models that reflect the key clinical and pathologic stages of progression should prove particularly valuable in sorting out the biology of large bowel tumor progression. The challenge then will be to use this knowledge for the design of preventive and therapeutic strategies.

Animals↗
PubMed1988

Phase I clinical trial of a combination of dipyridamole and acivicin based upon inhibition of nucleoside salvage.

A Phase I clinical trial of simultaneous 72-h infusions of dipyridamole and acivicin was carried out in patients with advanced malignancies. The objective of this trial was to determine the maximum tolerated dose of dipyridamole when administered as a 72-h infusion in combination with acivicin. The development of this combination is of interest because of in vitro observations which demonstrate that dipyridamole potentiates the cytotoxic action of acivicin by blocking nucleoside salvage. Patients were treated with concomitant i.v. infusions of dipyridamole and acivicin for 72 h. The acivicin dose infused remained constant during the trial at 60 mg/m2/72 h. The maximum tolerated dose (MTD) of dipyridamole was 23.1 mg/kg/72 h. Limiting toxicities at the MTD of dipyridamole with acivicin were severe gastrointestinal and constitutional symptoms which appeared to be caused by the high doses of dipyridamole administered. Escalation of dipyridamole did not potentiate the mild myelosuppression or the neurotoxicity which occurs with acivicin alone. At a dose of dipyridamole which was well below the MTD, one patient experienced symptomatic orthostatic hypotension, and another patient with coronary artery disease developed dizziness and transient electrocardiogram abnormalities. However, no other hypotensive or cardiovascular events occurred as dipyridamole was escalated to the MTD. Phlebitis occurred at the site of infusion when the dose of dipyridamole exceeded 13.5 mg/kg/72 h. Because of this local toxicity, it was necessary to administer dipyridamole through a central venous catheter to achieve maximum plasma levels. At the MTD of dipyridamole, steady-state total and free plasma levels of 11.9 microM and 27.8 nM, respectively, were attained by 24 h. These are free dipyridamole levels which in vitro were sufficient to block cytidine salvage and to potentiate the biochemical and cytotoxic effects of acivicin against human colon cancer cells (P.H. Fischer et al., Cancer Res., 44:3355-3359, 1984).

Antineoplastic Combined Chemotherapy Protocols↗
PubMed1988

Biochemical assessment of the effects of acivicin and dipyridamole given as a continuous 72-hour intravenous infusion.

Since this Phase I trial was based on a strategy of biochemical modulation, namely, the inhibition of nucleoside uptake by dipyridamole, a biochemical assessment of the actions of acivicin and dipyridamole was undertaken in order to aid our interpretation of the clinical findings. The primary biochemical objectives of this trial were: (a) to determine whether plasma levels of dipyridamole sufficient to inhibit nucleoside uptake could be achieved with a 72-h continuous i.v. infusion; (b) to monitor the effects of acivicin on two key enzymatic targets, CTP synthetase and GMP synthetase; and (c) to evaluate changes in cellular ribonucleoside triphosphate pools during therapy. Since peripheral blood mononuclear cells have relevant biochemical targets and can be serially obtained during the course of therapy, the biochemical effects of acivicin and dipyridamole were determined in these cells. At the maximally tolerated dose of dipyridamole (23.1 mg/kg/72 h), the steady-state concentrations of total and free dipyridamole averaged 11.9 microM and 27.8 nM, respectively. These levels were sufficient to inhibit cytidine (1 microM) uptake by greater than 50% in the lymphocytes of five of six patients so treated. Using lymphocytes obtained from 14 normal volunteers the concentration of free dipyridamole needed to inhibit the uptake of 1 microM cytidine by 50% averaged 13.8 +/- 1.1 nM. The plasma levels of alpha 1-acid glycoprotein, which tightly binds dipyridamole, ranged from 60 to 300 mg/dl in the patients in this study. As a consequence there were wide variations in the percentage of dipyridamole present as the unbound, pharmacologically active form and in the rates of dipyridamole clearance. The decreased rate of dipyridamole clearance seen in patients with high levels of alpha 1-acid glycoprotein resulted in higher plasma concentrations of total dipyridamole and compensated for the reduced fraction of free drug. Therefore, the plasma concentration of free dipyridamole varied much less than the total drug concentration in these patients. CTP synthetase and GMP synthetase activities were measured in patients' peripheral mononuclear cells prior to and at various times during therapy. CTP synthetase activity was inhibited in a time-dependent fashion by greater than 75% in seven of 13 evaluable courses; GMP synthetase was similarly inhibited in only three of ten cases. Ribonucleoside triphosphate pools were also measured in the patient's lymphocytes. CTP pool reductions of 30 to 50% were seen in nine of 19 courses, but in only four cases was the inhibition greater than 50%.(ABSTRACT TRUNCATED AT 400 WORDS)

Antineoplastic Combined Chemotherapy Protocols↗
PubMed1988

Lack of interferon production by dipyridamole.

Dipyridamole, previously reported to be an interferon (IFN) inducer in mice, was evaluated in 43 normal volunteers or cancer patients. At doses ranging from 150 mg orally to 887 mg intravenously, no serum antiviral activity suggesting IFN induction was observed.

Dipyridamole↗
PubMed1988

Phase II trial of a combination of interferon-beta ser and interferon-gamma in patients with advanced malignant melanoma.

Based upon the in vitro synergistic activity of interferon-beta (IFN-beta) and interferon-gamma (IFN-gamma) observed in melanoma cells, we initiated a Phase II trial using the combination to determine the clinical antitumor efficacy in patients with advanced disease. Fifteen patients with metastatic malignant melanoma were given 2,000 micrograms of recombinant IFN-gamma (rIFN-gamma) (Biogen) intravenously (i.v.) over 10 min, followed by a 10 min i.v. injection of 30 million units of recombinant IFN-beta (rIFN-beta ser) (Triton) 3 x/week. Six patients had skin, soft tissue, nodal, or subcutaneous metastases, 6 had visceral disease only, and 3 had both. Seven patients had received prior treatment, including chemotherapy (6), radiotherapy (3), and/or immunotherapy (3). Side effects included typical IFN constitutional symptoms such as anorexia, fatigue, nausea, and myalgias, but were not dose limiting. The mean drop in the white blood cell count (WBC) following 1 month of therapy, compared to baseline, was 3.3 x 10(3)/mm2 (p = 0.002); the mean increase in SGOT was 24.1 U/l (p less than 0.001). One patient had a dose reduction for Grade III anorexia and fatigue which did not resolve with repeated treatment. One patient with liver metastases had radiographical and clinical stabilization of his disease for 1 year. No responses were seen. The median time to progression was 6 weeks. Two patients' tumors were evaluable in the human tumor colony forming assay (HTCFA) and were markedly sensitive to the antiproliferative effects of IFN combinations. Both patients, however, failed to respond clinically.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1988

In vitro models of human colonic adenomatous polyps.

In this report we describe methods which were used to cultivate cell lines from adenomatous polyps. Many of the techniques used have evolved from our past experience with the cultivation of colonic epithelial neoplastic cells (McBain et al., 1984) and the experience of others successful in the cultivation of benign and cancerous colon tissues. We feel that the preservation of cell-to-cell associations is a key to our successful cultivation of adenomas. Moyer (Moyer and Aust, 1984) has also pointed out the importance of preserving cell-to-cell associations in her successful studies to culture normal and neoplastic colonic tissues. Friedman's primary culture system for adenomatous polyps (Friedman et al., 1981) is further evidence supporting this point. Using the techniques described in this report, three cell lines, two small tubular polyps and one villous polyp, have been established and characterized. These cells can be expanded to numbers that will be sufficient for molecular and biochemical studies, and the cell number will be sufficient to conduct transfection experiments. Paraskeva (Paraskeva et al., 1984) has described two other cell lines derived from adenomatous polyps arising in patients with familial polyposis. The availability of cell lines from tubular and villous polyps make it possible to propose experiments to probe the biology of colonic adenomas.

Adenoma↗
PubMed1987

Phase I clinical trial and pharmacokinetic evaluation of acodazole (NSC 305884), an imidazoquinoline derivative with electrophysiological effects on the heart.

Acodazole (NSC 305884) is a synthetic imidazoquinoline which has antimicrobial as well as antineoplastic properties. A Phase I trial of acodazole administered as a 1-h i.v. infusion once weekly X 4 was conducted. Mild to moderate nausea and vomiting and moderate burning and erythema at the infusion site were the only toxicities seen among 33 patients treated over 51 courses at doses between 20 mg/m2/week and 888 mg/m2. The first patient treated at 1184 mg/m2 developed an irregular pulse and was found to have a prolonged cardiac output interval (Q-Ti) on electrocardiogram and polymorphic ventricular tachycardia ("torsades des pointes"). Careful study of five additional patients treated according to a modified schedule (340 mg/m2 week one, 500 mg/m2 week 2, 666 mg/m2 week 3, and 888 mg/m2 week 4) revealed 20% or greater Q-Ti prolongation after 20 of 27 treatments; Q-Ti prolongation had resolved 24-36 h after each infusion. Q-Ti prolongation occurred at all dose levels; no ventricular arrhythmias occurred. Acodazole was cleared with a long t1/2 (20.7 h) primarily by nonrenal mechanisms. No alterations in peak plasma levels or excretion were seen in the patients in whom Q-Ti prolongation was detected. No antitumor activity was seen. Further development of acodazole will require delineation of pharmacological means of surppressing this Q-Ti prolongation.

Adult↗
PubMed1987

Synergistic antitumor effects of tumor necrosis factor and gamma-interferon on human colon carcinoma cell lines.

We assessed the antiproliferative effects of tumor necrosis factor (TNF-alpha) and gamma-interferon (IFN-gamma) alone and in combination, on nine human colon carcinoma cell lines. All were resistant (less than 30% inhibition) to TNF-alpha alone. Four cell lines were resistant to IFN-gamma alone, two exhibited a minimal degree of sensitivity (30-50% inhibition), one was moderately sensitive, and two were inhibited 70% or greater. A synergistic antiproliferative effect occurred in eight of the nine cell lines treated with a combination of TNF-alpha and IFN-gamma. In seven of these eight, the combination of cytokines resulted in 30-40% more growth inhibition than predicted had an additive interaction occurred (P less than 0.005). In two cell lines with an induced resistance to mitomycin C, an increase in resistance to combined TNF-alpha and IFN-gamma treatment correlated with an increasing resistance to mitomycin C. The data were further analyzed to determine if combination treatment altered the sensitivity of the cells to one or both agents in addition to synergistically potentiating growth inhibitory effects. Combinations of TNF-alpha/IFN-gamma enhanced the dose response activity of TNF-alpha in three cell lines (P less than or equal to 0.09) and decreased the dose response activity of IFN-gamma in another three (P less than or equal to 0.02). Colony forming experiments on HCT 116 cells demonstrated a reduction in the number of 250-micron colonies in the IFN-gamma/TNF-alpha treatment groups when compared to controls, indicating that combined treatment had a cytotoxic effect. We conclude that combination TNF-alpha/IFN-gamma treatment has a synergistic cytotoxic effect on human colon carcinoma cells. IFN-gamma may enhance the effectiveness of TNF-alpha in some cell lines, but not conversely. These results may have therapeutic implications.

Cell Cycle↗
PubMed1987

Cell culture of human colon adenomas and carcinomas.

Cell lines were established from colon adenomas, including tubular and villous polyps, primary adenocarcinomas, and metastases arising in patients with colon adenocarcinomas. The protocol for cultivating these diverse tissues includes primary cultivation of tissue explants on a type I collagen gel followed by nonenzymatic subculture of the epithelial outgrowth. All early passages were accomplished using low subculture ratios. Cultured cells elaborate morphological structures which are similar to features present in the tissues from which they were cultivated. Specifically, all structural features of colon epithelial cells were identified, including junction formation, prominent microvilli, and mucin secretion, in several cell lines. Five cell lines cultured from colonic neoplasms at different stages of cancer progression were selected for detailed characterization. Cells grown from two tubular polyps had normal human karyotypes. Cells from a villous polyp and all adenocarcinomas were aneuploid with stable marker chromosomes. The established cell lines exhibit distinct phenotypes based on growth characteristics in vitro and in athymic mice; and it is suggested that these cell lines represent useful models for studying the evolution of colon cancer from a benign to an aggressive cell type.

Adenocarcinoma↗
PubMed1987

Augmentation of methotrexate cytotoxicity in human colon cancer cells achieved through inhibition of thymidine salvage by dipyridamole.

In HCT 116 cells, a human colon cancer cell line, the levels of thymidine (0.6 microM) and hypoxanthine (9 microM) contributed to the tissue culture medium by the fetal bovine serum significantly reduced the growth inhibition and lethality produced by 0.1 microM methotrexate. Dipyridamole, an inhibitor of nucleoside transport, potentiated the growth inhibitory effects of methotrexate when the cells were grown in medium that was changed daily. However, when the medium was supplemented with dialyzed serum, methotrexate cytotoxicity was not increased by dipyridamole. Similarly, in cloning experiments, dipyridamole increased the cell killing produced by methotrexate. The potentiation of methotrexate toxicity produced by dipyridamole was mediated through inhibition of thymidine uptake. The uptake of 1 microM thymidine was inhibited 50% by 0.12 microM dipyridamole but neither hypoxanthine nor guanine uptake was decreased by dipyridamole (5 microM). As a result, the decrease in dTTP pools produced by methotrexate was augmented by dipyridamole. In contrast, dipyridamole did not influence the effect of methotrexate on ribonucleoside triphosphate pools. HCT 116 cells avidly salvaged low concentrations of thymidine, and methotrexate increased this capacity. Conversion of 0.11 microM thymidine to thymidine triphosphate was increased by 55%, from 16.6 to 25.7 pmoles/10(6) cells, following exposure to 1.0 microM methotrexate. Dipyridamole blocked this pool expansion. This study suggests that the salvage of physiological levels of thymidine may diminish the cytotoxic effects of methotrexate on human colon cancer cells. Inhibition of thymidine uptake by dipyridamole may be an effective strategy to increase the cytotoxicity of methotrexate.

Cell Line↗
PubMed1987

Platinum analogue combination chemotherapy: cisplatin and carboplatin--a phase I trial with pharmacokinetic assessment of the effect of cisplatin administration on carboplatin excretion.

Cisplatin (NSC 119875) and carboplatin (NSC 241240) are platinum (II) analogues with very different spectra of toxicity. Cisplatin dose is limited by nausea and vomiting, renal dysfunction, and dose-related peripheral neuropathy, whereas carboplatin is myelosuppressive. There are also clinical and laboratory data that suggest that these drugs may not be completely cross-resistant. Therefore, the following phase I trial of combination therapy with cisplatin and carboplatin was undertaken. Since carboplatin toxicity is enhanced in the presence of renal impairment, carboplatin excretion was also evaluated in selected patients at the maximum tolerated dose. Thirty-three patients received 50 mg/m2 cisplatin and doses of carboplatin between 160 mg/m2 and 400 mg/m2. Sequential 20-minute infusions of carboplatin and then cisplatin were able to be administered at the standard doses of carboplatin (320 and 400 mg/m2) with thrombocytopenia to the degree expected if carboplatin alone had been given. However, 280 mg/m2 carboplatin followed by 25 mg/m2 cisplatin/d X 3 caused unexpectedly severe thrombocytopenia in seven of eight patients (median platelet nadir 45,000/microL; range, 12 to 321,000/microL; nadir was less than 90,000 in seven of eight patients). In three patients treated with 280 mg/m2 carboplatin plus 25 mg/m2/d X 3 cisplatin, pharmacokinetics of carboplatin were compared during consecutive monthly cycles without and with cisplatin. Modestly increased areas under the curve (AUC) for carboplatin (15% and 35%) with cisplatin were seen in the two patients who experienced more pronounced platelet suppression with combination therapy. No other limiting or unusual toxicity was seen with this combination. Responses, primarily in "platinum responsive" tumors, were seen. The combination of cisplatin plus carboplatin is feasible and merits further study.

Anemia↗
PubMed1987

Phase I study of taxol administered as a short i.v. infusion daily for 5 days.

Taxol inhibits cell division by promoting the assembly and stabilization of microtubules. This report describes the results of a phase I trial of taxol administered as a short iv infusion daily for 5 days every 4 weeks. Sixteen patients with refractory malignancy received 21 courses of taxol at five doses between 5 and 40 mg/m2/day X 5. The first nine patients received taxol as a 60-minute infusion. Two patients experienced anaphylactoid reactions, one at the 5-mg/m2/day and the second at the 15-mg/m2/day X 5 dose levels. These reactions were characterized by facial flushing, tachypnea, and hypotension within several minutes of drug administration. These anaphylactoid reactions occurred on the first day of treatment in the first patient and on the first day of the second course in the second patient. These reactions may be related to the rapid administration of the polyoxyethylated castor oil (Cremophor EL) vehicle in which taxol is formulated. No anaphylactoid reactions were observed in the seven patients who received taxol as a 6-hour infusion with antihistamine and prednisone premedication. Dose-related myelosuppression was seen; leukopenia (wbc count less than 1000/mm3) and granulocytopenia (granulocytes less than or equal to 200/mm3) occurred on Days 8 and 9 in two of two patients treated at the 40 mg/m2/day X 5 level. Thrombocytopenia was mild, with a platelet nadir of 87,000-95,000/mm3 at the highest dose level. Premedication with glucocorticoids and antihistamines coupled with a prolonged 6-hour infusion permitted taxol to be administered at 30 mg/m2/day X 5 safely without immediate life-threatening reactions.

Alkaloids↗
PubMed1987

Phase II trial evaluating continuous infusion of etoposide, cisplatin, and hexamethylmelamine in extensive-disease small cell carcinoma of the lung.

A total of 27 untreated and 24 previously treated patients with extensive-disease small cell lung cancer (SCLC) were treated with a combination chemotherapeutic regimen of continuous-infusion etoposide for 5 days, cisplatin, and hexamethylmelamine. of 25 evaluable patients with untreated SCLC, three (12%) achieved a complete response and 16 (64%) achieved a partial response. Among 23 evaluable patients with relapsed SCLC there were no complete responses and nine (39%) achieved a partial response. Median survival times were 252 and 109 days for the above groups, respectively. Myelotoxicity, especially thrombocytopenia, was moderately severe. Other toxic effects, including renal and neurologic, were minimal. These results compare favorably with other regimens including etoposide and cisplatin. Our results further confirm the activity of etoposide and cisplatin as both initial therapy and as a salvage regimen in the management of patients with extensive-stage SCLC.

Adult↗
PubMed1987

Phase I trial of combinations of recombinant interferons beta(ser) and gamma in patients with advanced malignancy.

Based upon in vitro and in vivo synergistic activity of Type I and Type II interferons (IFNs) in preclinical in vitro and in vivo studies, we initiated a phase I trial evaluating the doses, safety, and pharmacokinetics of combinations of recombinant DNA-produced human IFN-beta ser and IFN-gamma in 27 patients with cancer. Twenty-four patients were treated with a 2-hour infusion of IFN-gamma, followed by a 10-minute iv injection of IFN-beta ser, three times a week. Patients were entered on fixed dose levels of 1 X 10(6), 3 X 10(6), 10 X 10(6), 30 X 10(6), and 100 X 10(6) units of each IFN. In addition, three patients were treated at the highest dose level with a 10-minute iv infusion of IFN-gamma and a 10-minute iv infusion of IFN-beta ser. The maximally tolerated dose when administered by this schedule for greater than or equal to 4 weeks was 30 X 10(6) units of each IFN. Dose-limiting side effects at doses of 100 X 10(6) units of each IFN consisted of fatigue, nausea, vomiting, anorexia, paralytic ileus, and neutropenia. The most common side effects at the three highest dose levels were fever, rigors often requiring parenteral meperidine, and constitutional symptoms. Reversible elevations in SGOT and LDH were also noted. Serum IFN levels were dose related, with peak titers occurring immediately after IFN administration. One patient with a nodular mixed lymphoma had a partial response which has been sustained for over 1 year. We conclude that combinations of IFN-beta ser and IFN-gamma can be safely administered on a chronic basis without enhanced or cumulative toxic effects.

Adolescent↗
PubMed1986

Antiproliferative effects of interferons on human melanoma cells in the human tumor colony-forming assay.

The human tumor colony-forming assay (HTCFA) is an in vitro test that has been used to predict the activity of anticancer drugs against a patient's tumor. We utilized the assay to analyze the antiproliferative effects of seven interferons (IFNs) against 40 human melanomas to determine which IFN had the greatest antiproliferative activity in this drug-resistant tumor. IFNs studied included recombinant IFN-alpha 2; human lymphoblastoid IFN; IFN-alpha Cantell; native beta RPMI; two recombinant IFNs-beta; and recombinant IFN-gamma. Growth was sufficient [greater than 30 tumor colony-forming units (TCFU)/well] for assessing the antiproliferative effects of at least one IFN in 25 tumors (63%). A dose-response relationship was demonstrated by all IFNs in tumors in which some activity was observed (p less than or equal to 0.01). Individual melanomas differed in their sensitivities to the various IFNs. Overall, however, none of the IFNs was markedly more effective in antiproliferative effects than any other, although there was a trend toward IFN-beta ser having more potent antiproliferative properties when compared to IFN-alpha 2 (p = 0.055). Twelve of 13 tumors exposed to combinations of IFN-beta ser and IFN-gamma demonstrated a synergistic antiproliferative effect. In all but two of these, low concentrations of each IFN (less than or equal to 50 U/ml), when combined, resulted in 85-95% inhibition. As prolonged exposure to high concentrations of IFN are often not clinically tolerable, these data suggest that IFN combinations may be one way of achieving more clinically meaningful IFN doses, schedules, and regimens, provided antiproliferative effects are of importance in vivo.

Antineoplastic Agents↗
PubMed1986

Synergistic antiproliferative effects of human recombinant alpha 54- or beta ser-interferon with gamma-interferon on human cell lines of various histogenesis.

The antiproliferative effects of human interferon (IFN), IFN-gamma, IFN-alpha 54, and IFN-beta ser, alone and in combination, were assessed on 10 human cell lines. All IFNs were produced by recombinant technology and purified to homogeneity. In all cell lines except one, the addition of IFN-gamma to either IFN-alpha 54 or IFN-beta ser resulted in a synergistic antiproliferative effect, regardless of individual IFN sensitivities or tissue of origin. The only exception was a normal diploid fibroblast cell in which an additive antiproliferative effect occurred with combination IFN treatment. A malignant fibrosarcoma cell line of similar mesenchymal origin demonstrated a synergistic antiproliferative effect. One cell line was sensitive to both type I and type II IFN alone. Three cell lines were relatively resistant to IFN-gamma but not to IFN-beta ser, one was relatively resistant to IFN-beta ser but not to IFN-gamma, and the remainder were resistant to both IFN-gamma and IFN-beta ser or IFN-alpha 54. The addition of IFN-alpha 54 to IFN-beta ser in the SKCO 1 cell line resulted in an antagonistic interaction. Timing experiments with RT112 cells indicate that IFN-gamma and IFN-beta ser need not be in the media at the same time for the synergistic effect to occur. Combinations of type I and type II IFN thus resulted in synergistic antiproliferative effect for transformed human cells of various histogenesis, including some with a relative resistance to one or both IFN types.

Cell Cycle↗