Impact of temozolomide on immune response during malignant glioma chemotherapy.

Malignant glioma, or glioblastoma, is the most common and lethal form of brain tumor with a median survival time of 15 months. The established therapeutic regimen includes a tripartite therapy of surgical resection followed by radiation and temozolomide (TMZ) chemotherapy, concurrently with radiation and then as an adjuvant. TMZ, a DNA alkylating agent, is the most successful antiglioma drug and has added several months to the life expectancy of malignant glioma patients. However, TMZ is also responsible for inducing lymphopenia and myelosuppression in malignant glioma patients undergoing chemotherapy. Although TMZ-induced lymphopenia has been attributed to facilitate antitumor vaccination studies by inducing passive immune response, in general lymphopenic conditions have been associated with poor immune surveillance leading to opportunistic infections in glioma patients, as well as disrupting active antiglioma immune response by depleting both T and NK cells. Deletion of O6-methylguanine-DNA-methyltransferase (MGMT) activity, a DNA repair enzyme, by temozolomide has been determined to be the cause of lymphopenia. Drug-resistant mutation of the MGMT protein has been shown to render chemoprotection against TMZ. The immune modulating role of TMZ during glioma chemotherapy and possible mechanisms to establish a strong TMZ-resistant immune response have been discussed.

Temozolomide associated with PEG-interferon in patients with metastatic melanoma: a multicenter prospective phase I/II study.

Metastatic melanoma treatment remains disappointing, and a combined approach by chemotherapy and immunotherapy might increase the response rates through a synergistic action. Accordingly, a clinical trial using oral temozolomide (TMZ) and subcutaneous PEG-interferon alpha-2b (PEG) in patients with metastatic melanoma was designed to determine the maximal tolerated dosage of both drugs and the antitumoral response. A multicenter, prospective, phase I/II study was conducted in 31 metastatic melanoma patients, without cerebral metastasis. Dose escalation was performed according to the modified continual reassessment method scale and resulted in four cohorts of patients: TMZ 150 mg/m2 5 days/week each 4 weeks and PEG 0.5 microg/kg/week - TMZ 150 mg/m2 5 days/week and PEG 1.0 microg/kg/week - TMZ 200 mg/m2 5 days/week and PEG 0.5 microg/kg/week - TMZ 200 mg/m2 5 days/week and PEG 1.0 microg/kg/week. Patients received a maximum of six cycles. Thirty-three patients were enrolled in this study: one in the first dose level, one in the second one, 18 in the third one and 11 in the fourth one. At level 4, four of 11 patients experienced dose-limiting toxicity and four nondose-limiting toxicity; toxicity was mainly hematologic (grade IV thrombocytopenia). An objective response was observed in five patients (two complete response and three partial response) receiving level 3 or 4 of treatment. The disease remained stable in three patients, and six of 31 patients were alive 24 months after enrollment. The association of oral TMZ with subcutaneous PEG in metastatic melanoma displayed an unacceptable hematological toxicity with the dosages of 200 mg/m2 5 days/week and 1 microg/week, respectively. At a lower level, this treatment was effective and deserves further investigations to define its indications in metastatic melanoma patients.

Selective CD4+ lymphopenia in melanoma patients treated with temozolomide: a toxicity with therapeutic implications.

PURPOSE: Standard schedule temozolomide (TMZ; daily for 5 days every 4 weeks) is often used in melanoma patients, but phase III data show that it is no more effective than standard dacarbazine. Extended TMZ dosing regimens may be superior by delivering the drug continuously at a higher dose over time. Using an extended dosing schedule, we noted a high incidence of lymphopenia and occasional opportunistic infections (OIs). Here we report our retrospective experience in the first 97 patients. MATERIALS AND METHODS: TMZ was administered at 75 mg/m(2)/d orally for 6 weeks every 8 weeks, although nine patients were treated continuously without a break. Seventeen patients were treated with TMZ alone; 73 patients received TMZ with thalidomide; seven patients received TMZ with low-dose interferon alfa. RESULTS: Median duration of TMZ treatment was 113 days; 29% received > or = 24 weeks of therapy. Lymphopenia was seen in 60% of patients (absolute lymphocyte count < 800/microL) with a median of 101 days to lymphopenia. TMZ did not cause significant neutropenia or thrombocytopenia. Lymphopenia was not more common in patients treated concomitantly with thalidomide. In all patients analyzed for lymphocyte subsets, lymphopenia induced by TMZ affected the CD4(+) compartment preferentially. There were two documented OIs (Pneumocystis and Aspergillus pneumonia) as well as other infections indicative of T-cell dysfunction in another 21 patients. CONCLUSION: TMZ at this dose and schedule results in CD4(+) lymphopenia in a majority of patients that can result in OIs. Pneumocystis pneumonia prophylaxis should be considered for patients who develop sustained lymphopenia on TMZ.

Stress and chemotherapy. Combined effects on tumor progression and immunity in animal models.

In mice bearing Lewis lung carcinoma, rotational and restraint stress specifically increases the formation of lung metastasis, and restraint stress markedly attenuates the antitumor effects of cyclophosphamide. The aim of this investigation was therefore to examine the effects of restraint stress on tumor metastasis in mice bearing MCa mammary carcinoma, and on the effectiveness of CCNU and DTIC. Restraint stress increases MCa mammary carcinoma metastasis, causes a marked reduction in cyclophosphamide activity, and a minor attenuation of the effects of CCNU and DTIC. The possible occurrence of seasonal factors, observed for the increase by rotational stress of Lewis lung carcinoma metastasis, was also determined for cyclophosphamide effectiveness. The survival time of control mice is longer in February than in June, and is not appreciably modified by rotational stress. The effects of cyclophosphamide are similar in both seasonal periods, and are similarly attenuated by rotational stress. The seasonal effects of rotational stress, and the reduction of the effects of cyclophosphamide caused by rotational stress, are accompanied by corresponding variations in the number of CD3+ and CD4+ splenic T-lymphocyte subsets and in the CD4+/CD8+ ratio, respectively. The reported effects of stress on tumor progression and on the effectiveness of cyclophosphamide thus appear to occur via modulation of immune responses of the host directed against the tumor. These data appear of interest for their experimental implications, and suggest the opportunity to consider the role that the stress during treatment may play in determining the effectiveness of clinical antitumor chemotherapy.

Drug-induced immunogenic changes of murine leukemia cells: dissociation of onset of resistance and emergence of novel immunogenicity.

n vivo exposure of tumor-bearing mice to the antineoplastic agent 5-(3,3-dimethyl-1-triazenyl)-1H-imidazole-4-carboxamide (DTIC) results in increased immunogenicity of tumor cells, an event often referred to as "chemical xenogenization" (CX). To verify the hypothesis of DTIC-induced somatic mutation(s) as the major mechanism underlying CX, studies were performed to dissociate CX from the onset of drug resistance, which was invoked in the past as an event leading to selection of preexisting immunogenic clones. Therefore, experiments were done with a DTIC-susceptible tumor line treated with DTIC and quinacrine dihydrochloride (Q), an antimutagenic compound, according to selected experimental schedules. At different transplant generations, the CX and the onset of drug resistance were evaluated. The results show that a) Q does not prevent the onset of DTIC resistance, b) DTIC-resistant clones arising after treatment with DTIC plus Q are not immunogenic, and c) CX is selectively antagonized by Q. The present data confirm that DTIC-induced immunogenicity is not the result of a selection mechanism mediated by the drug and give further support to the hypothesis that the molecular mechanism of CX may be related to somatic mutation(s).

Susceptibility of murine lymphoma cells treated with 5-(3,3-dimethyl-1-triazenyl)-1H-imidazole-4-carboxamide to NK-mediated cytotoxicity in vitro.

Novel drug-mediated tumor antigens (DMTA) have been detected in chemically induced L5178Y lymphoma of DBA/2 origin, following treatment of tumor-bearing hosts with 5-(3,3-dimethyl-1-triazenyl)-1H-imidazole-4-carboxamide (DTIC). Studies were conducted on the susceptibility of the DTIC-treated subline, maintained in tissue culture, to NK-mediated cytolysis in vitro. The results of the experiments showed that DTIC-treated lymphoma cells are less susceptible to NK cell lysis than the parental line (i.e. L5178Y); the DTIC-treated lymphoma, maintained in vivo as ascitic form, behaved as the corresponding in vitro line, thus suggesting that NK-resistant phenotype was not dependent upon propagation conditions. The intrinsic susceptibility to cell-mediated lysis of the DTIC-treated tumor was unchanged, as demonstrated by lysis produced by alloimmune cytotoxic cells or by natural cytotoxic mesenteric lymph node effectors. "Cold" competition experiments and target binding assay performed with L5178Y/tc and its DTIC-treated subline showed that DTIC-altered cells are less efficient than the parental line as "cold" competitor cells for NK-mediated lysis and bind less efficiently than L5178Y tumor to NK lymphocytes. These data suggested that the NK resistance of the DTIC-treated lymphoma may result from a failure to bind to effector cells, as a consequence of a profound rearrangement of the cell surface produced by DTIC treatment of cancer cells.

Immunosensitivity and histocompatibility antigens in drug-altered leukemic cells.

New antigenic properties of experimental lymphomas have been reported previously following in vivo treatment with antitumor agents. 5-(3,3-Dimethyl-1-triazeno)imidazole-4-carboxamide (DIC) induced new antigenic characteristics on L1210 and L5178Y lymphomas, that were previously investigated in studies in animals compatible with the original untreated parental tumors. Here the L1210/DIC and L5178Y/DIC susceptibility to the cytotoxic effects of allogeneic and xenogeneic lymphocytes and sera obtained from animals sensitized to DBA/2 histocompatibility antigens were studied. The original and the DIC tumors showed the same sensitivity to anti-DBA/2 cellular and humoral cytotoxicity. The immune response electied in allogeneic mice by the original and DIC sublines was evaluated by in vitro cell-mediated and humoral cytotoxic assay. Beyond the immune response to histocompatibility antigens, a specific, anti-DIC-antigen immunoreaction was not found. Inhibition assay of the cell-mediated cytotoxicity and absorption of the humoral cytotoxicity demonstrated that DIC-induced antigens are not reciprocally related in cell-surface concentration to the natural DBA/2 histocompatibility antigens associated with tumor cells of DIC lines. An experiment was conducted in which specific activity against the DIC-treated L5178Y/DIC cells was observed with anti-L5178Y/DIC rabbit immune serum absorbed with the parental L5178Y lymphoma. This finding provides additional support to previous studies indicating that treatment with DIC induced new antigens on the lymphoma cells.