In vitro and in vivo anti-tumor activity of recombinant mouse tumor necrosis factor (TNF) in a mouse bladder tumor (MBT-2)

Tumor necrosis factor (TNF) has confirmed anti-tumor activity. When used in combination with interferon gamma (IFNG) or chemotherapeutic drugs targeted at DNA topoisomerase II, synergistic cytotoxicity has been observed. Investigations of the anti-tumor activity of recombinant mouse TNF in a mouse bladder tumor model (MBT-2) were performed. The cytotoxicity of TNF and low dose actinomycin-D (AMD) against MBT-2 in vitro was examined alone and following preincubation with IFNG. The activity of TNF/AMD in vivo utilizing an intravesical implantation mode (MBT-2) was also evaluated. TNF alone had no cytotoxic effect in vitro. TNF/AMD was cytotoxic for MBT-2 growth in vitro. Maximum cytotoxicity (86%) occurred at one microgram./ml. TNF/one microgram./ml. AMD with 50% cytotoxicity at .64 micrograms./ml. TNF/one/microgram./ml. AMD. A two hour preincubation with IFNG markedly increased the cytotoxicity of TNF/AMD whereas longer incubations did not enhance cytotoxic activity. TNF alone and in combination with AMD did not significantly reduce the percentage of intravesical tumor outgrowth in vivo compared to controls. This study demonstrated that TNF/AMD exhibits cytotoxicity for MBT-2 cells in vitro but is ineffective in reducing implantation of intravesical tumors in vivo. The in vitro data suggest brief exposure of MBT-2 cells to IFNG augments the subsequent anti-tumor activity of TNF/AMD.     

Effects of photodynamic therapy in combination with intravesical drugs in a murine bladder tumor model.

This study was designed to evaluate the interaction of photodynamic therapy (PDT) and intravesical drugs (thiotepa, adriamycin, mitomycin C and BCG) in a murine transitional cell carcinoma (MBT-2) model. C3H/He mice with implanted MBT-2 flank tumors were treated with either thiotepa (TT), adriamycin (ADM), mitomycin C, Bacillus Calmette-Guerin (BCG), photodynamic therapy (PDT) or a combination of the drug and PDT. The MBT-2 tumor showed sensitivity to adriamycin, MMC or PDT compared to control. PDT combined with either adriamycin, MMC or BCG, produced a greater retardation in the growth of the MBT-2 tumor than monotherapy with adriamycin, MMC, BCG or PDT. PDT combined with the anticancer agents currently used in intravesical therapy for bladder cancer is well tolerated. The combination of PDT and intravesical drugs may enhance the tumoricidal effect of either treatment used alone.     

Interferons Modify in Vitro Proliferation of Human Bladder Transitional Cell Carcinoma in the Presence of Doxorubicin and Mitomycin C

Purpose

The aim of the present study was to investigate whether interferons with their known antitumor activity modify the response of human bladder carcinoma cells to antitumor drugs.

Materials and Methods

We investigated the in vitro effect of doxorubicin, mitomycin C and the interferons alpha and gamma on cell proliferation in human bladder carcinoma cell lines as measured by 5-bromo-2'-deoxy-uridine (BrdU) incorporation.

Results

Exposure of RT 112 (but not EJ 28) cells for 2 hours to doxorubicin (500 ng./ml.) and mitomycin C (200 ng./ml.) reduced the proliferation rate to 85.9 plus/minus 3.3 percent (n = 4) and 89.3 plus/minus 4.0 percent (n = 4) of control. Treatment for 2 days with interferon alpha and gamma up to the highest concentration (200 U/ml.) showed no effect. The combination of 100 U/ml. interferon alpha and doxorubicin decreased proliferation significantly. At 50 ng./ml. the proliferation rate was decreased to 88.0 plus/minus 5.7 percent of control and at 500 ng./ml. to 67.7 plus/minus 3.1 percent. Thus interferon alpha seems to increase the sensitivity of the cells to doxorubicin. Cells treated with 20 ng./ml. mitomycin C after pretreatment with interferon alpha showed a dramatic decrease in cell proliferation (from 98.8 plus/minus 2.1 percent to 80.2 plus/minus 4.0 percent of control). This decrease was similar in the presence of 200 ng./ml. mitomycin C. Thus mitomycin C seems to render cells more sensitive to the antiproliferative action of interferon alpha. Interferon gamma had only minor effects on the response of the cells to doxorubicin or mitomycin C.

Conclusions

These studies suggest that exposure to interferon alpha increases the efficacy of anticancer drugs in vitro, probably by several mechanisms. Potential consequences of this finding for the therapeutic regime employed for treatment of bladder carcinoma are discussed.     

Comparison of the efficacy of intravesical Bacillus Calmette-Guérin with thiotepa, mitomycin C, poly I:C/poly-L-lysine and cis platinum in murine bladder cancer

The efficacy of intravesical Bacillus Calmette-Guérin for the treatment of the mouse bladder tumor MBT-2 was compared with that of thiotepa, mitomycin C, cis-diamminedichloroplatinum II and poly I:C/poly-L-lysine. MBT-2 cells were instilled into the bladder immediately after electrocauterization. Drug instillations were initiated 24 hours later and continued on a weekly basis for 4 weeks. Both Bacillus Calmette-Guérin and cis-diamminedichloroplatinum II significantly (p less than .0004) inhibited MBT-2 tumor implantation when compared to diluent-treated controls. Neither mitomycin C, thiotepa nor poly I:C/poly-L-lysine significantly inhibited tumor implantation. Mean tumor weights also were significantly (p less than .05) reduced in Bacillus Calmette-Guérin and cis-diamminedichloroplatinum II-treated mice, while tumor mean weights in mice treated with thiotepa, mitomycin C or poly I:C/poly-L-lysine were not significantly different than controls. These results suggest that the efficacy of intravesical Bacillus Calmette-Guérin in comparison with other drugs in the MBT-2 mouse bladder tumor model is similar to observations reported in human clinical trials in which intravesical Bacillus Calmette-Guérin was shown to be more effective than other cytotoxic drugs. These data further support the utility of the MBT-2 model for the study of the mechanisms by which Bacillus Calmette-Guérin inhibits bladder tumor growth.     

Tumor necrosis factor enhances the in vitro and in vivo efficacy of chemotherapeutic drugs targeted at DNA topoisomerase II in the treatment of murine bladder cancer

Recombinant human tumor necrosis factor (rTNF) is a macrophage secretory protein with antitumor activity. The murine bladder tumor cell line MBT-2 was used to evaluate the in vitro and in vivo antitumor effects of rTNF in combination with chemotherapeutic drugs targeted at DNA topoisomerase II. These drugs, such as adriamycin and etoposide (VP 16), are in widespread use in the treatment of human cancer. The rTNF significantly enhanced the cytotoxic efficacy of the topoisomerase-targeted drugs actinomycin D, adriamycin, etoposide (VP 16) and teniposide (VM 26) against MBT-2 cells in vitro. The rTNF alone had no effect upon the cells in the same assay. When examined in vivo using MBT-2 tumor-bearing C3H/HeJ mice, these same antitumor relationships were seen. The addition of rTNF to actinomycin D or VP 16 resulted in a significant reduction in tumor volume at 20 days compared to untreated animals. Actinomycin D, VP 16 or rTNF treatment alone had no significant effect on 20 day tumor volume. The data provide a reasonable basis for the addition of rTNF to experimental protocols for the treatment of human bladder cancer using topoisomerase-targeted drugs such as adriamycin both intravesically and systemically. These observations may also be relevant to other human cancers currently treated with these drugs.     

干扰素结合化疗药物对膀胱癌细胞株BIU-87的抑制作用

在离体条件下，采用噻唑蓝（MTT）染色法，观察干扰素（IFN）与丝裂霉素C（MMC）、阿霉素（ADM）、噻替哌（TSPA）和羟基喜树碱（HCPT）等化疗药物联合应用对人类膀胱癌细胞株BIU－87的抑制作用。结果在连续联合用药组，浓度为25000u／ml的IFN与上述药物50％抑制率（ID50－1）剂量联合使用的抑制率分别为57．4％、58．6％、55．3％和64．3％；在序贯联合用药组，将MMC、ADM的ID50－2剂量作用于细胞24h后，再使用浓度为25000u／ml的IFN，24h后两者联合使用的抑制率分别为59．4％和54．3％。认为IFN与MMC等化疗药物联合应用能够取得较好的协同作用，为临床治疗浅表性膀胱肿瘤提供了新的思路。     

Inhibition of mouse bladder tumor proliferation by alpha difluoromethylornithine and interferon in vitro and in vivo

Previous studies have reported that alpha difluoromethylornithine (DFMO), an enzyme-activated, irreversible inhibitor of ornithine decarboxylase (ODC), has anti-tumor activity in several tumor systems. Recently, investigations have revealed that combinations of DFMO and Interferon (IFN) are synergistic in inhibiting tumor cell growth. We tested the effects of DFMO and IFN alpha, beta alone and in combination on the growth of mouse bladder tumor (MBT-2) cells both in vitro and in vivo. MBT-2 cells were incubated for 72 hours in 96 well microtiter plates with DFMO, IFN alpha, beta and combinations of both agents and percentage inhibition was calculated. In vivo studies utilized the intravesical implantation method as well as subcutaneous implantation. DFMO was administered as a 1% solution in the drinking water. IFN alpha, beta was given bi-weekly by intravesical administration. DFMO effectively inhibited MBT-2 growth in vitro. The ID50 was 0.08 mM and peak inhibitory activity was reached at concentrations of 0.16 mM and remained constant with concentrations of up to 10 mM. IFN alpha, beta also inhibited the in vitro proliferation of MBT-2 with maximum inhibition (46%) at 2,000 U/ml. Combinations of DFMO and IFN alpha, beta showed increased anti-proliferative activity. The degree of enhancement varied with synergism, additivity, or sub-additivity at varying drug concentrations. In vivo, DFMO significantly retarded the growth of tumors implanted subcutaneously (p less than .05) and significantly delayed the outgrowth of tumors implanted intravesically (p less than .01). IFN alpha, beta alone was ineffective in vivo and produced no additive effect in vivo when used in combination with DFMO. Results of our investigation show that DFMO inhibits proliferation of MBT-2 cells in vitro and exhibits a similar effect in vivo against subcutaneous and intravesical tumor implants. IFN alpha, beta alone demonstrated anti-proliferative activity in vitro but did not affect MBT-2 growth in vivo. Although the combination of DFMO and IFN alpha, beta exhibited enhanced activity in vitro, no enhancement was observed with combination therapy in vivo.     

Chemosensitivity test on superficial urinary bladder cancer using the dye exclusion assay--model of intravesical chemotherapy

A chemosensitivity test was carried out on superficial bladder cancers using the trypan blue dye exclusion assay for the purpose of screening chemosensitive drugs for intravesical chemotherapy. Transplantable murine bladder tumor cells (MBT-2) were incubated, in vitro, in the presence of adriamycin (4, 40, 400, 1000 micrograms/ml) as well as verapamil (3, 30, 100, 500 micrograms/ml) at 5% CO2, 37 degrees C for two hours. After cellular viabilities were calculated, MBT-2 cells were inoculated into the hind limbs of mice. The cellular viability was correlated well with the ratio of tumor appearance, tumor growth inhibition and prolongation of survival, and was dose dependent in the adriamycin treated groups. On the other hand, a reduction of cellular viability, tumor growth inhibition and prolongation of survival were seen in the high dose verapamil (100, 500 micrograms/ml) treated groups. Human superficial bladder cancer cells were incubated in the presence of adriamycin, 4'-0-tetrahydropyranyladriamycin, mitomycin C and pepleomycin (1000 micrograms/ml) and/or verapamil (500 micrograms/ml). The reduction rates of cellular viability markedly varied with the kind of anticancer drugs. A reduction of cellular viability of human tumor cells as well as MBT-2 cells was seen in the verapamil treated groups. This rapid and handy assay seems to be useful for the purpose of screening chemosensitive drugs for intravesical chemotherapy.     

Intravesical chemotherapy: studies on the relationship between osmolality and cytotoxicity

The effectiveness of intravesical chemotherapy for the treatment of superficial bladder cancer may be influenced by the conditions of administration, such as the osmotic strength of the instillate. Urine from patients with bladder cancer before treatment had osmolalities in the range 187 to 852 mOsm./kg. and these had decreased by an average of 135 mOsm./kg. at the completion of intravesical chemotherapy. Clinical preparations of drugs used for intravesical chemotherapy had osmotic strengths ranging from 65 to 1,038 mOsm./kg. The antitumor activities of the drugs most frequently used intravesically (doxorubicin, epodyl, mitomycin C and thiotepa), and of cisplatin and epirubicin in media of 6 different osmolalities were measured with a human bladder cancer cell line by inhibition of colony-forming ability. Reducing osmotic strength from 590 to 125 mOsm./kg. significantly increased the in vitro cytotoxicities of thiotepa, mitomycin C, cisplatin and epirubicin but not those of doxorubicin and epodyl. We conclude that the use of an instillate at the lowest achievable osmotic strength probably will be optimal for the intravesical administration of chemotherapeutic drugs.     

A phase I study of intravesical suramin for the treatment of superficial transitional cell carcinoma of the bladder

PURPOSE: Suramin is a polysulfonated naphthylurea that inhibits proliferation and DNA synthesis of transitional cell carcinoma cell lines. Its large molecular size and negative charge inhibit bladder absorption, making suramin an excellent candidate for intravesical chemotherapy. Intravesical suramin was evaluated in a phase I study to define dose limiting toxicity and systemic absorption, determine a starting dose and regimen for phase II studies and provide a preliminary assessment of in vivo antitumor activity. MATERIALS AND METHODS: Intravesical suramin treatment was administered in 9 patients with histologically identified transitional cell carcinoma (Tcis, Ta or T1) in whom at least 1 course of standard intravesical chemotherapy (bacillus Calmette-Guerin, thiotepa or mitomycin C) had failed. Suramin was administered once weekly for 6 weeks. Patients were treated in groups of 3 using a 60 cc volume and intrapatient dose escalation schedule. Suramin doses of 0.3 to 614.4 mg./ml. were administered intravesically. The last group was treated with the same weekly dose for 6 weeks. RESULTS: The 9 patients underwent 54 treatments with suramin. Plasma suramin concentration after treatment was 1.9 to 38.0 microg./ml. and was not related to treatment dose. The dose escalation phase was limited by the solubility of suramin in solution. Complications included self-limited bladder spasms (less than 24 hours) in 4 of 54 treatments (7%) and new or worsening vesicoureteral reflux in 3 ureters (17%). Another patient who was treated after the Foley balloon was inflated in the urethra experienced bladder spasms, skin flushing and fever (39C). Mean bladder capacity before and after treatment was 600 and 540 ml., respectively. At followup 7 patients had stage Ta tumors and 2 had carcinoma in situ. CONCLUSIONS: An intravesical suramin dose of 153 mg./ml was defined as a safe treatment parameter with acceptable plasma concentrations and minimal side effects. Phase II studies are needed to assess the antitumor activity of suramin in patients with transitional cell carcinoma of the bladder.     

The effect of intravesical instillations of thiotepa, mitomycin C, and adriamycin on normal urothelium: an experimental study in rats

The effects of intravesical instillations of thiotepa, mitomycin C and adriamycin on the normal urothelium were studied in rats. Changes in the bladder wall in the form of fibroblastic atypia and submucous fibrous plaques were significant in the mitomycin C treated group. In 46% of mitomycin C treated animals there was urothelial atypia and in one animal, the atypia was severe enough to resemble carcinoma in situ. None of the rats treated with thiotepa showed intramural fibrous plaques or fibroblastic atypia and only 8% showed urothelial atypia. In the group treated by adriamycin instillation, 17% showed intramural fibrous plaques, but none showed urothelial atypia or fibroblastic atypia. The fibroblastic atypia and submucosal fibrous plaques seen in the mitomycin treated group may explain the reduced bladder capacity seen in the clinical setting.     

In vitro study of the interaction of doxorubicin, thiotepa, and mitomycin-C, agents used for intravesical chemotherapy of superficial bladder cancer

Several cytotoxic agents have been identified as effective in the treatment of superficial transitional cell carcinoma of the bladder, including doxorubicin, thiotepa and mitomycin-C. An in vitro study was conducted to assess the interactions of these three drugs against a well differentiated human bladder tumor cell line, RT-4, to identify and evaluate synergistic combinations among these agents. Cytotoxicity was evaluated by a colorimetric assay based on the capacity of viable cells to metabolize a tetrazolium dye, MTT, to produce a colored formazan product. The analyses of drug interactions were done by the isobolographic method (construction of isoeffect plots). The combination of doxorubicin and thiotepa was found to be the most synergistic, followed by the combination of doxorubicin and mitomycin-C. The combination of mitomycin C and thiotepa demonstrated an unpredictable effect. These findings suggest the combination of doxorubicin and thiotepa has potential advantage for chemotherapy of superficial bladder tumors.     

The effect of suramin, tumor necrosis factor and interferon gamma on human prostate carcinoma

Suramin, an antiparasitic agent which has been shown to block the stimulatory effect of growth factors on certain cancers, is currently being evaluated in clinical trials and as an antineoplastic agent in patients with advanced prostate carcinoma. Preliminary studies suggested that suramin inhibits the growth in vitro of human prostate carcinoma. The present study was performed in order to evaluate the effect of suramin, recombinant human tumor necrosis factor (TNF), interferon gamma and the combination of suramin plus TNF or interferon gamma on proliferation of PC-3, a human, hormone unresponsive prostate carcinoma cell line. In medium containing 2% fetal calf serum (FCS) suramin, at doses of 10 microM, 30 microM and 100 microM (levels readily achievable in humans) inhibited proliferation of PC-3. TNF, at a concentration of 500 units/ml., induced an approximately 50% inhibition of growth of PC-3. The combination of suramin plus TNF induced a greater inhibition of growth than did either agent alone, even at the low dose of 10 microM suramin. Interferon gamma, 500 units/ml., inhibited PC-3 growth. However, the combination of interferon gamma plus suramin (30 microM) induced less inhibition of proliferation than did interferon gamma alone. These results may serve as a rationale for clinical trials employing the combination of TNF plus suramin in patients with advanced prostate carcinoma.     

Combination immunotherapy of murine transitional cell cancer using BCG and an interferon-inducing pyrimidinone

The immunomodulator ABPP (2-amino-5-iodo-6-phenyl-4(3H) pyrimidinone) is an interferon inducer and has been shown to have in vivo activity against the murine bladder tumor MBT-2. Two experiments were performed to determine if ABPP might enhance the in vivo anti-tumor activity of Bacillus Calmette-Guerin (BCG). First, in vivo stimulation of cell-mediated cytotoxicity by BCG and ABPP was measured in C3H mice using a chromium-release assay. An earlier, greater, and longer-lasting increase in cytotoxicity was caused by ABPP than by BCG. Based on the differing times to peak cytotoxic stimulation, groups of 15 mice each were pretreated intraperitoneally at different times prior to inoculation with MBT-2. Compared to saline, ABPP alone did not increase survival, while BCG alone did increase survival (p less than 0.01), and the combination of BCG and ABPP yielded the highest survival (p less than 0.001). These results indicate that 1) ABPP affects the immune system differently than BCG, and 2) while ABPP may have less single-agent activity against MBT-2 than BCG, ABPP may serve to potentiate the activity of BCG.     

Inhibition of implantation of murine bladder tumor by thiotepa in cauterized bladder

This study was designed to determine the role of immediate intravesical instillation of single dose thiotepa post transurethral resection of bladder tumor in the prevention of recurrence by tumor implantation, using murine bladder tumor line 2 and 201 C3H/He mice. Previous studies have suggested implantation may take place as early as the first hour and reach its maximum in 24 hours after resection of bladder tumor. An in vitro dose response curve of MBT2 to thiotepa was established by treatment with various concentrations of thiotepa of 0.00, 0.01, 0.21, 0.44, and 1.91 mg./ml. In a group of 201 mice, the bladder was catheterized with a 24G angiocatheter, and a fine copper wire was inserted through the lumen. The bladder was cauterized by touching the wire with a Bovie coagulator for four seconds at the lowest setting. All bladders were instilled with 1 x 10(6) cells of murine bladder tumor line 2, followed by instillation of 1.91 mg./ml. of thiotepa with various time delays per treatment group. The bladder implantation rates were 30.4% (17/56), 3.4% (2/59), 6.5% (2/31) and 26.9% (7/26) in the control, immediate, one-hour delay and 24-hour delay groups, respectively. The urethral implantation rates were 21.4% (12/56), 0% (0/59), 6.5% (2/31) and 0% (2/26), respectively. The overall implantation rates (bladder, urethra, or both) were 42.9% (24/56), 3.4% (2/59), 6.5% (2/31) and 25.9% (7/27), respectively. Implantation rates were significantly higher in the control and 24-hour delay groups than in the immediate and one-hour instillation groups (p less than 0.05, Fisher Exact Test). We conclude from this animal model that intravesical instillation of single dose thiotepa, to be effective, should be initiated within the first hour after tumor resection, since it dramatically decreased the incidence of bladder and urethral implantation.     

吡柔比星与其他灌注化疗药物预防膀胱肿瘤复发疗效比较的Meta分析

目的 比较吡柔比星与其他灌注化疗药物预防膀胱肿瘤复发的疗效. 方法检索Medline、EMBase、CBMDisc等文摘数据库以及PubMed、ScienceDirect、Lww、Springer、中国期刊全文数据库、中文科技期刊数据库等全文数据库,收集并按照纳入和排除标准筛选已发表的关于吡柔比星与其他膀胱灌注化疗药物预防膀胱肿瘤术后复发疗效比较的对照研究,提取纳入研究中关于复发的数据进行Meta分析. 结果共获得15个符合标准的研究.其中10个研究比较了吡柔比星和丝裂霉素的疗效,Meta分析显示,吡柔比星预防膀胱肿瘤复发的疗效显著优于丝裂霉素(OR=0.41,95%CI0.27～0.61,P＜0.01);6个研究分别比较了吡柔比星与噻替哌(OR=0.35,95%CI 0.11～1.13,P＞0.05)、阿霉素(OR=0.15,95%CI 0.03～0.76,P＜0.05)、表阿霉素(OR=0.53,95%CI 0.23～1.23,P＞0.05)、羟基喜树碱(OR=0.25,95%CI 0.10～0.64,P＜0.05)等药物以及空白对照组的疗效,统计学分析显示吡柔比星疗效显著优于羟基喜树碱、阿霉素以及空白对照组,而与噻替哌和表阿霉素疗效的差异无统计学意义. 结论吡柔比星能有效预防膀胱肿瘤术后复发,其疗效优于丝裂霉素、羟基喜树碱、阿霉素等药物,是新的可选择的膀胱肿瘤灌注化疗药物.     

Intravesical chemotherapy: Combination with tween 80 increases cytotoxicity in vitro

Summary Tween 80 was shown to enhance significantly the cytotoxic activities of the four drugs (adriamycin, epodyl, mitomycin-c, thiotepa) most frequently administered intravesically to treat superficial bladder cancer. The colony forming ability of a human bladder cancer cell line, RT112, was measured following a 1 h exposure to each of the four drugs both alone and in combination with 0.1% and 0.3% Tween 80. Cell survival was not reduced by 0.1% Tween 80 alone. We conclude that the combination of Tween 80 with these drugs might increase the therapeutic index of intravesical chemotherapy.     

Antiproliferative activities of interferons against human bladder carcinoma cell lines in vitro

The antiproliferative effect of interferons against 5 human bladder carcinoma cell lines, RT112, T24, RT4, 647V and HT1197, was determined in vitro. Each of these human bladder carcinoma cell lines except 647V was sensitive to human interferons in liquid media. The antiproliferative effect of interferons was observed only upon continuous exposure, not after 1 hour. Partially purified, naturally produced interferon beta was more inhibitory of cell growth than naturally produced interferon alpha. Interferon alpha 54, 76, 61, 6L and 1 purified to homogeneity were as effective as naturally produced, partially pure interferon alpha. Although interferon beta, produced by recombinant DNA technology and purified to homogeneity, was not equivalent in effectiveness to naturally produced interferon beta, its antiproliferative activity was greater than interferon alpha 54 for 3 of 4 cell lines tested. Antimitotic effects may underlie, at least in part, the potential therapeutic activity of interferons for bladder carcinoma.     

Enhanced in vivo therapy of pulmonary metastases with interferon and interleukin-2

Interleukin-2 (IL-2) can mediate in vivo tumor regression at high doses. To enhance this efficacy, we studied the effect of adding a human hybrid recombinant interferon alpha A/D (rHuIFN-alpha-A/D) because of its known in vitro augmentation of immune-mediated tumoricidal activity. C56BL/6 mice bearing established pulmonary metastases induced by the iv injection of the methylcholanthrene-induced fibrosarcoma MCA 106 were treated for 12 days with intraperitoneal injections of (1) Hanks' balanced salt solution, (2) recombinant IL-2, (3) rHuIFN-alpha-A/D, and (4) a combination of IL-2 and HuIFN-alpha-A/D. IL-2 and interferon each had some antitumor activity. However, maximal reduction of pulmonary metastases consistently resulted from combining IL-2 with interferon. In two of four experiments, this combination was significantly better compared to either IL-2 or interferon treatment alone. The most potent regimen was 12 days of IL-2 (50,000 units bid) together with rHuIFN-alpha-A/D (50,000 units ip qd). No consistent pattern of proliferative or cytotoxic activity was found against a panel of stimulator and target cells. These results demonstrate enhanced antitumor efficacy of combining recombinant interferon alpha and IL-2 against established pulmonary metastases. Potential clinical applications are suggested by these data.     

Effect of systemic glutathione depletion by buthionine sulfoximine on sensitivity of murine bladder cancer to cytotoxic agents

The effect of systemic glutathione (GSH) depletion on sensitization of bladder cancer cells to various antineoplastic agents was investigated using murine model, MBT-2. Subcutaneous injection(s) of buthionine sulfoximine (BSO) significantly depleted the GSH content in the tumor and organs. BSO pretreatment produced significant enhancement in the antitumor effect of cyclophosphamide (CY), though it failed to sensitize the tumors to doxorubicin hydrochloride (Adriamycin), cisplatin, mitomycin C, JM-8, methotrexate, vinblastine, and tumor necrosis factor. Mice tolerated cytotoxic agents alone and in combination with BSO except for cisplatin in combination with BSO. A 29 percent (4/14) mortality rate was observed in mice treated with BSO and divided schedule of cisplatin.