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Background: When given during pregnancy, the drug 3'-azido-2',3'-dideoxy-thymidine (AZT) substantially reduces maternal--fetal transmission of human immunodeficiency virus type 1 (HIV-1). However, AZT has been shown to be carcinogenic in adult mice after lifetime oral administration. In this study, we assessed the transplacental tumorigenic and genotoxic effects of AZT in the offspring of CD-1 mice and Erythrocebus patas monkeys given AZT orally during pregnancy. Methods: Pregnant mice were given daily doses of either 12.5 or 25.0 mg AZT on days 12 through 18 of gestation (last 37% of gestation period). Pregnant monkeys were given a daily dose of 10.0 mg AZT 5 days a week for the last 9.5-10 weeks of gestation (final 41%-43% of gestation period). AZT incorporation into nuclear and mitochondrial DNA and the length of chromosomal end (telomere) DNA were examined in multiple tissues of newborn mice and fetal monkeys. Additional mice were followed from birth and received no further treatment until subjected to necropsy and complete pathologic examination at 1 year of age. An anti-AZT radioimmunoassay was used to monitor AZT incorporation into DNA. Results: At 1 year of age, the offspring of AZT-treated mice exhibited statistically significant, dose-dependent increases in tumor incidence and tumor multiplicity in the lungs, liver, and female reproductive organs. AZT incorporation into nuclear and mitochondrial DNA was detected in multiple organs of transplacentally exposed mice and monkeys. Shorter chromosomal telomeres were detected in liver and brain tissues from most AZT-exposed newborn mice but not in tissues from fetal monkeys. Conclusions: AZT is genotoxic in fetal mice and monkeys and is a moderately strong transplacental carcinogen in mice examined at 1 year of age. Careful long-term follow-up of AZT-exposed children would seem to be appropriate.

Background: Onconase, a protein isolated from oocytes and early embryos of the frog Rana pipiens, shares extensive homology with bovine pancreatic ribonuclease (RNase A) and possesses similar enzyme activity. Onconase is cytotoxic toward cancer cells in vitro and exhibits antitumor activity in animal models. In addition, Onconase has been shown to enhance the cytotoxic activity of some chemotherapeutic agents in vitro. Purpose: We studied interactions between the cytotoxic effects of Onconase and the chemotherapeutic agent vincristine (VCR) in the treatment of drug-sensitive and multidrug-resistant human colon carcinoma cells in vitro and in mice. Methods: Transplantable human colon carcinoma cells (HT-[29.sup.par] cells) were infected with a retrovirus containing human marl (also known as MDR1 and PGY1) complementary DNA (encoding P-glycoprotein [P-gp]), and clones that were cross-resistant to colchicine, doxorubicin, and vinblastine were selected (HT-[29.sup.mdr1] cells). Drug-resistant HT-[29.sup.mdr1] cells and drug-sensitive HT[29.sup.par] parental cells were treated with Onconase and/or VCR in vitro at varying concentrations to measure the effects on protein synthesis and cell viability. The impact of Onconase on VCR accumulation in both types of cells was determined in the presence or absence of MRK-16, an anti-P-gp monoclonal antibody capable of reversing the multidrug-resistant phenotype. The antitumor effects of onconase and/or VCR treatment were assessed in nude mice bearing established HT-[29.sup.par] or HT-[29.sup.mdr1] intraperitoneal tumors. [IC.sup.50] values (drug concentrations resulting in 50% inhibition of protein synthesis or cell viability) for Onconase and VCR were determined from semilogarithmic dose-response curves; interactions between the cytotoxic effects of these two agents were evaluated using data from protein synthesis inhibition experiments and a two-way analysis of variance. Survival distributions from in vivo experiments were compared using Cox proportional hazards models. Results: The combination of Onconase and VCR yielded enhanced cytotoxicity in vitro that was independent of P-gp expression. Evaluation of the effects of these two compounds on protein synthesis over a wide range of drug concentrations indicated possible synergistic interactions (i.e., greater than additive effects) in both drug-resistant and drug-sensitive cells. The enhancement of VCR cytotoxicity was dependent on onconase enzyme activity and was not associated with increased intracellular levels of VCR. Simultaneous treatment of mice bearing HT-[29.sup.par] tumors with Onconase and VCR did not extend their median survival time (MST) significantly (MST with VCR = 66 days; MST with VCR plus Onconase = 69 days; two-tailed P = .57); however, the MST of mice with HT-[29.sup.mdr1] tumors was extended significantly by this treatment (MST with VCR = 44 days; MST with VCR plus Onconase = 66 days; two-tailed P

The anti--P-glycoprotein monoclonal antibody MRK-16 mediates the reversal of multidrug resistance. Recombinant human interferon alfa (rHuIFN [alpha]) enhances the cytotoxic activity of diverse chemotherapeutics and may modulate multidrug resistance. Purpose: Our purpose was to determine the outcome of combination treatment with MRK-16, rHuIFN [alpha]-2a, and cytotoxic agents on tumor cells that express P-glycoprotein (Pgp). Methods: Three Pgp-expressing, multidrug-resistant human tumor cell lines were used: the MDR1 retrovirus-infected HT-29 colon adenocarcinoma (HT-[29.sup.mdr1]), the doxorubicin (Adriamycin)-resistant MCF-7 ([Adr.sup.R] MCF-7) breast carcinoma, and the de novo Pgp-acquired, HCT-15 colon carcinoma. The parental cell lines HT-[29.sup.par] and MCF-7 were used as controls. The in vitro effects of MRK-16 and rHuIFN [alpha]-2a were studied on: (a) chemosensitivity of parental and multidrug-resistant cell lines to vincristine, doxorubicin, or paclitaxel (Taxol); (b) intracellular drug concentrations; and (c) Pgp expression. The efficacy of vincristine alone or in combination with MRK-16 and/or rHuIFN [alpha]-2a was assessed against HT-[29.sup.mdr1] cells in female, athymic NCr-nu/nu mice. Results: For vincristine, the [IC.sub.50] (i.e., the concentration that causes 50% inhibition of cell growth) was 7.0 ng/mL in HT-[29.sup.mdr1] cells. Pretreatment of HT-[29.sup.mdr1] cells with MRK-16 partially restored vincristine sensitivity ([IC.sub.50] = 4.8 ng/mL), which was enhanced by noncytotoxic concentrations of rHuIFN [alpha]-2a ([IC.sub.50] = 2.9 ng/mL) via a mechanism independent of Pgp modulation or [[.sup.3.H]]vincristine efflux. rHuIFN [alpha]-2a potentiated MRK-16 reversal of multidrug resistance with both doxorubicin and paclitaxel on HT-[29.sup.mdra1] cells and with vincristine on [Adr.sup.R] MCF-7 and HCT-15 tumor cells. Treatment of mice with 1 mg/kg vincristine weekly for 3 weeks, beginning 10 days after tumor injection, significantly increased the median survival times of the HT-[29.sup.par] tumor-bearing mice (60 days versus 35 days; P

Background: We have demonstrated that, in the human ovarian carcinoma cell line (OVCAR-3), recombinant human interferon [alpha] (rHuIFN-[alpha]) potentiated in vitro inhibition of protein synthesis by immunotoxins. The antitumor activity of intracavitary immunotoxin administered to nude mice 5 days after tumor cell injection was enhanced by a nontherapeutic dose of rHuIFN-[alpha], as evidenced by increased survival time. Purpose: Our purpose was to determine the outcome of treatment with immunotoxin and rHuIFN-[alpha] in xenografts of more advanced tumors. Methods: At 10 or 15 days after tumor cell injection, nude mice with peritoneal OVCAR-3 xenografts were treated intraperitoneally with immunotoxin or with 454A12 monoclonal antibody (Mab) recombinant ricin A chain (rRA), alone or combined with a nontherapeutic dose of rHuIFN-[alpha]. The immunotoxin was composed of rRA covalently bound to an anti-CD71 (transferrin receptor) MAb. In other experiments, mice were treated intraperitoneally with cyclophosphamide and cisplatin to reduce tumor size on days 20 and 27 after tumor cell inoculation and then, beginning on day 40, with immunotoxin alone or combined with rHuIFN-[alpha]. Results: Initiation of treatment 10 days after OVCAR-3 transplantation significantly increased median survival from 41 to 89 days (10% survivors on day 120) with 454A12 MAb rRA alone and to more than 120 days (70% survivors) with 454A12 MAb rRA combined with rHuIFN-[alpha] (P

• The use of immunotherapy for acute myelogenous leukemia (AML) is controversial. Twenty-four trials have been reported in which 1,491 patients with AML received various forms of immunotherapy, including BCG, methanol extract residue (MER) of BCG, or Corynebacterium parvum. Some patients were immunized with allogeneic or autologous leukemia blast cells. In only four of the 24 trials was a significant prolongation of remission reported. Pooled data from all 24 studies were analyzed further. No statistically significant difference in duration of remission between patients who received maintenance chemotherapy alone and those who received maintenance chemotherapy plus immunotherapy was found. A significant survival advantage for those patients who received BCG and chemotherapy for maintenance therapy was detected. A beneficial biologic effect for the patients treated with BCG is suggested but this was not a disease-free survival advantage, and had no impact on cure of patients with AML. Immunotherapy, as currently conceived, seems to have no substantial benefit for patients with AML receiving optimal chemotherapy.(Arch Intern Med 1983;143:1726-1731)

Background: We have demonstrated that, in the human ovarian carcinoma cell line (OVCAR-3), recombinant human interferon α (rHuIFN-α) potentiated in vitro inhibition of protein synthesis by immunotoxins. The antitumor activity of intracavitary immunotoxin administered to nude mice 5 days after tumor cell injection was enhanced by a nontherapeutic dose of rHuIFN-α, as evidenced by increased survival time. Purpose: Our purpose was to determine the outcome of treatment with immunotoxin and rHuIFN-α in xenografts of more advanced tumors. Methods: At 10 or 15 days after tumor cell injection, nude mice with peritoneal OVCAR-3 xenografts were treated intraperitoneally with immunotoxin or with 454A12 monoclonal antibody (MAb) recombinant ricin A chain (rRA), alone or combined with a nontherapeutic dose of rHuIFN-α. The immunotoxin was composed of rRA covalently bound to an anti-CD71 (transferrin receptor) MAb. In other experiments, mice were treated intraperitoneally with cyclophosphamide and cisplatin to reduce tumor size on days 20 and 27 after tumor cell inoculation and then, beginning on day 40, with immunotoxin alone or combined with rHuIFN-α. Results: Initiation of treatment 10 days after OVCAR-3 transplantation significantly increased median survival from 41 to 89 days (10% survivors on day 120) with 454A12 MAb rRA alone and to more than 120 days (70% survivors) with 454A12 MAb rRA combined with rHuIFN-α (P<.0001). The increase in survival time between tumor-bearing mice treated with immunotoxin combined with rHuIFN-α and those treated with immunotoxin alone was statistically significant (P =.017). In contrast, the 15-day transplant tumors were not curable with immunotoxin therapy (survival, 72 days; 0% survivors) and were refractory to rHuIFN-α potentiation (survival, 75 days; 0% survivors). After the second course of chemotherapy to reduce the size of the advanced tumors (day 40), during the ascites cell count nadir, initiation of treatment with 454A12 MAb rRA alone or combined with rHuIFN-α resulted in significantly different survival times of 129 and 162 days, respectively (P =.0037). Pathologic examination of surviving mice treated with chemotherapy and 454A12 MAb rRA alone or in combination with rHuIFN-α revealed that one (17%) of six mice and 11 (65%) of 17 were tumor free, respectively. Conclusions: The synergy between immunotoxins and IFN-α is dependent on tumor burden. These agents are less effective against large tumor burdens (i.e., advanced stage disease), but their beneficial effects re-emerge after cytoreduction by combination chemotherapy. Implications: The ideal setting for testing the efficacy of intracavitary immunotoxin combined with rHuIFN-a after front-line chemotherapy is in patients with residual tumor refractory to additional chemotherapy or in those with toxic effects that prevent delivery of effective doses. [J Natl Cancer Inst 85:907–912, 1993]