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Background/aim Breast cancer (BC) may be affected by diabetes and anti-diabetic medication, as well as its therapeutic agents. Low-dose metronomic chemotherapy (LDMC) is an available treatment option in BC. We investigated the impact of insulin on low-dose metronomic vinorelbine and mafosfamide in BC cell lines. Materials and methods Human BC cell lines T-47D, MCF-7, MDA-MB-231, BT-549 and non-tumorigenic breast cell line MCF-10A were exposed to 0.01 μg/ml and 10 μg/ml insulin in combination with low-dose metronomic vinorelbine or mafosfamide. The cell viability was determined after 24-72 hours using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay. Results Insulin, especially at a concentration of 10 μg/ml, seemed to increase viability of vinorelbine-treated hormone receptor-positive BC cells, whereas low-dose mafosfamide treatment tended to be potentiated by insulin in triple-negative cells. Conclusion Our findings suggest that insulin may influence the cytotoxic activity of LDMC depending on insulin concentration, type of cytotoxic drug used and BC cell line.

Objective: Promotion of the proliferative expansion of CD4+Foxp3+ regulatory T cells (Tregs) is one of the side effects that limitsthe use of bleomycin (BLM) in the treatment of tumors. In this study, we examined the hypothesis that cyclophosphamide (CY),a chemotherapeutic agent with the capacity to eliminate tumor infiltrating Tregs, abrogated BLM-induced expansion of Tregs andconsequently resulted in a better anti-tumor effect. Methods: The in vitro effects of BLM, with or without mafosfamide (MAF, the active metabolite of CY), on both TGF-β-induceddifferentiation of Tregs (iTregs), and TNF-induced expansion of naturally occurring Tregs (nTregs) were assessed. The in vivo effectof low doses of BLM and CY on tumor-infiltrating Tregs, as well as on the growth of mouse B16-F10 melanomas, was also studied. Results: In vitro treatment with BLM promoted the differentiation of iTregs, as well as TNF-induced expansion of nTregs. Theseeffects of BLM were completely abrogated by MAF. Furthermore, in the mouse B16-F10 melanoma model, treatment with lowdoses of BLM increased the number of tumor-infiltrating Tregs, and this effect of BLM was also abrogated by CY. Importantly,combination therapy with low doses of BLM and CY showed synergistic anti-tumor effects. Conclusions: CY abrogated the effect of BLM on the expansion of Tregs. The combination of these 2 chemotherapeutic agents mayrepresent a safer and more effective therapy in the treatment of cancer patients, and thus merits future clinical evaluation.

The concept of immunogenic cell death (ICD) has emerged as a cornerstone of therapy-induced anti-tumor immunity. To this end, the following chemotherapies were evaluated for their ability to induce ICD in non-small cell lung cancer (NSCLC) cell lines: docetaxel, carboplatin, cisplatin, oxaliplatin and mafosfamide. The ICD hallmarks ATP, ecto-calreticulin, HMGB1, phagocytosis and maturation status of dendritic cells (DCs) were assessed in vitro. Furthermore, an in vivo vaccination assay on C57BL/6J mice was performed to validate our in vitro results. Docetaxel and the combination of docetaxel with carboplatin or cisplatin demonstrated the highest levels of ATP, ecto-calreticulin and HMGB1 in three out of four NSCLC cell lines. In addition, these regimens resulted in phagocytosis of treated NSCLC cells and maturation of DCs. Along similar lines, all mice vaccinated with NSCLC cells treated with docetaxel and cisplatin remained tumor-free after challenge. However, this was not the case for docetaxel, despite its induction of the ICD-related molecules in vitro, as it failed to reject tumor growth at the challenge site in 60% of the mice. Moreover, our in vitro and in vivo data show the inability of oxaliplatin to induce ICD in NSCLC cells. Overall with this study we demonstrate that clinically relevant chemotherapeutic regimens in NSCLC patients have the ability to induce ICD.

Activation of T cells, a major fraction of peripheral blood lymphocytes (PBLCS), is essential for the immune response. Genotoxic stress resulting from ionizing radiation (IR) and chemical agents, including anticancer drugs, has serious impact on T cells and, therefore, on the immune status. Here we compared the sensitivity of non-stimulated (non-proliferating) vs. CD3/CD28-stimulated (proliferating) PBLC to IR. PBLCs were highly sensitive to IR and, surprisingly, stimulation to proliferation resulted in resistance to IR. Radioprotection following CD3/CD28 activation was observed in different T-cell subsets, whereas stimulated CD34+ progenitor cells did not become resistant to IR. Following stimulation, PBLCs showed no significant differences in the repair of IR-induced DNA damage compared with unstimulated cells. Interestingly, ATM is expressed at high level in resting PBLCs and CD3/CD28 stimulation leads to transcriptional downregulation and reduced ATM phosphorylation following IR, indicating ATM to be key regulator of the high radiosensitivity of resting PBLCs. In line with this, pharmacological inhibition of ATM caused radioresistance of unstimulated, but not stimulated, PBLCs. Radioprotection was also achieved by inhibition of MRE11 and CHK1/CHK2, supporting the notion that downregulation of the MRN-ATM-CHK pathway following CD3/CD28 activation results in radioprotection of proliferating PBLCs. Interestingly, the crosslinking anticancer drug mafosfamide induced, like IR, more death in unstimulated than in stimulated PBLCs. In contrast, the bacterial toxin CDT, damaging DNA through inherent DNase activity, and the DNA methylating anticancer drug temozolomide induced more death in CD3/CD28-stimulated than in unstimulated PBLCs. Thus, the sensitivity of stimulated vs. non-stimulated lymphocytes to genotoxins strongly depends on the kind of DNA damage induced. This is the first study in which the killing response of non-proliferating vs. proliferating T cells was comparatively determined. The data provide insights on how immunotherapeutic strategies resting on T-cell activation can be impacted by differential cytotoxic effects resulting from radiation and chemotherapy.

There is individual variation in the course of disease development and response to therapy of patients with chronic lymphocytic leukemia (CLL). Novel treatment options for CLL include a new generation of purine analogs, antibodies and inhibitors of specific cell signaling pathways, which typically induce apoptosis or necrosis. A prospective analysis of patient blood samples revealed that a combination of four tests allowed the most appropriate and effective type of treatment to be selected prior to drug administration, and for the analysis of leukemic cell sensitivity to anticancer drug(s) during disease development. The comparative analysis of blood from the stable and progressive form of CLL in an individual patient revealed diversity in the response to anticancer agents. CLL peripheral blood mononuclear cells were incubated with cladribine + mafosfamide (CM), fludarabine + mafosfamide, CM + rituximab, rituximab alone (Rit) or kinetin riboside (RK). A combination of cell viability, differential scanning calorimetry (DSC) profiles of nuclear preparations and poly(ADP-ribose) polymerase 1 (PARP-1) protein expression analysis of the leukemic cells was performed to evaluate the anticancer effects of the tested agents during CLL development. The results of the present study indicate that such studies are effective in determining the most appropriate anticancer drug and could monitor disease progression on an individual level. In addition, the results of the current study suggest that CLL progression leads to diversification of the cellular drug response. The most efficient apoptosis inducer for the patient was purine analog RK when the disease was stable, while the CM combination was the most effective agent for the progressive form of disease.

The use of chemotherapeutic agents prior to treatment with infusion of cluster of differentiation (CD)19-chimeric antigen receptor (CAR)-T cells is important for the efficacy of clinical therapies against hematological malignancies. However, the effect of chemotherapeutic agents on CD19-CAR-T cells and the associated underlying mechanisms remain unknown. The first aim of the present study was to determine the effect of chemotherapeutic agents on CAR-T cells using the in vitro Cell Counting kit 8 assay. The second aim was to evaluate the abilities of fludarabine (FDR) and mafosfamide (MFA; a metabolite of cyclophosphamide) to induce apoptosis of CD19-CAR-T cells via the use of Annexin V/propidium iodide double staining. In addition, a JC-1 fluorescent probe was used to detect alterations in cell membrane potential, and flow cytometry analysis was used to measure concentrations of caspase-3/7 to identify apoptotic pathways of CD19-CAR-T cells. The data of the present study suggested that FDR and MFA inhibit the activities of CD19-CAR-T cells. Alterations to the mitochondrial membrane potential and an increase in the concentration of caspase-3/7 indicated early apoptosis of FDR- and MFA-treated CD19-CAR-T cells. The present study laid a theoretical foundation for the development of programs for clinical treatment.

Aldehyde dehydrogenase 3A1 (ALDH3A1) plays an important role in many cellular oxidative processes, including cancer chemoresistance, by metabolizing activated forms of oxazaphosphorine drugs such as cyclophosphamide (CP) and its analogues, such as mafosfamide (MF), ifosfamide (IFM), and 4-hydroperoxycyclophosphamide (4-HPCP). Compounds that can selectively target ALDH3A1 could permit delineation of its roles in these processes and could restore chemosensitivity in cancer cells that express this isoenzyme. Here we report the detailed kinetic and structural characterization of an ALDH3A1-selective inhibitor, CB29, previously identified in a high-throughput screen. Kinetic and crystallographic studies demonstrate that CB29 binds within the aldehyde substrate-binding site of ALDH3A1. Cellular proliferation of ALDH3A1-expressing lung adenocarcinoma (A549) and glioblastoma (SF767) cell lines, as well as ALDH3A1 non-expressing lung fibroblast (CCD-13Lu) cells, is unaffected by treatment with CB29 and its analogues alone. However, sensitivity toward the anti-proliferative effects of mafosfamide is enhanced by treatment with CB29 and its analogue in the tumor cells. In contrast, the sensitivity of CCD-13Lu cells toward mafosfamide was unaffected by the addition of these same compounds. CB29 is chemically distinct from the previously reported small-molecule inhibitors of ALDH isoenzymes and does not inhibit ALDH1A1, ALDH1A2, ALDH1A3, ALDH1B1, or ALDH2 isoenzymes at concentrations up to 250 μM. Thus, CB29 is a novel small molecule inhibitor of ALDH3A1, which might be useful as a chemical tool to delineate the role of ALDH3A1 in numerous metabolic pathways, including sensitizing ALDH3A1-positive cancer cells to oxazaphosphorines.

Background The heterogeneity of chronic lymphocytic leukemia (CLL) is thought to be due to differences in the expression of factors that regulate apoptosis and cell cycle, giving rise to diverse apoptotic disturbances and tumor properties. Therefore, the primary goal in CLL treatment is to overcome resistance to apoptosis and efficiently trigger this process in leukemic cells. Methods Mononuclear cells were obtained from the blood of CLL patients by Histopaque-1077 sedimentation. CLL cell samples from the blood of drug treated patients, (cladribine or fludarabine with cyclophosphamide; CC or FC), as well as the cell samples of untreated patients exposed to the used drug combinations (CM, FM) or mafosfamide alone for 48 h were fractionated into nuclear and cytoplasmic fractions or were lysed. DNA fragmentation was evaluated by agarose electrophoresis and also cytometrically as sub-G1 population. The expression of apoptosis related proteins and H1.2 histone translocation were evaluated in lysates and nuclear and cytoplasmic fractions, respectively with appropriate antibodies. Results Cladribine (C) and fludarabine (F) combined with cyclophosphamide/mafosfamide in vivo , as well as ex vivo trigger apoptosis in CLL cells. These drug combinations (CC; FC/CM; FM) induce leukemic cell apoptosis confirmed by DNA fragmentation, sub-G1 cell number, down-regulation of anti-apoptotic proteins (Mcl-1, Bcl-2), and H1.2 histone translocation in comparison with appropriate control cells, however, to a different degree. Conclusions The kinetics and rate of drug-induced apoptosis in leukemic cells under ex vivo experiments differ between patients, mirroring the differences noticed during in vivo treatment. Individual model cell samples indicate comparable susceptibility to the used drug combinations under in vivo and ex vivo conditions.

Obatoclax and ABT-737 belong to a new class of anticancer agents known as BH3-mimetics. These agents antagonize the anti-apoptotic members of Bcl-2 family. The Bcl-2 proteins modulate sensitivity of many types of cancer cells to chemotherapy. Therefore, the objective of the present study was to examine and compare the antileukemic activity of obatoclax and ABT-737 applied alone, and in combination with anticancer agent, mafosfamide and daunorubicin. The in vitro cytotoxic effects of the tested agents on human leukemia cells were determined using the spectrophotometric MTT test, Coulter electrical impedance method, flow cytometry annexin V–fluorescein/propidium iodide assay, and light microscopy technique. The combination index analysis was used to quantify the extent of agent interactions. BH3 mimetics significantly decreased the leukemia cell viability and synergistically enhanced the cytotoxic effects induced by mafosfamide and daunorubicin. Obatoclax affected the cell viability to a greater degree than did ABT-737. In addition, various patterns of temporary changes in the cell volume and count, and in the frequency of leukemia cells undergoing apoptosis, were found 24 and 48 h after the tested agent application. ABT-737 combined with anticancer agents induced apoptosis more effectively than obatoclax when given in the same combination regimen. The results of the present study point to the different antileukemic activities of obatoclax and ABT-737, when applied alone, and in combination with anticancer agents. A better understanding of the exact mechanisms of BH3 mimetic action is of key importance for their optional use in cancer therapy.

We have already shown that IL-10 plays an important role in immunosuppression and metastatic dissemination in the rat B-cell lymphoma L-TACB model. It was suggested that the up-regulation of IL-10 production and IL-10 receptor (IL-10R) expression would be part of the transition from primary tumor to metastatic phenotype and that IL-10, besides its immunosuppressive activity, may act as a growth factor for metastatic L-TACB cells. The treatment of L-TACB-bearing rats with a single low-dose cyclophosphamide decreased IL-10 production, reverted immunosuppression and induced the immunologic rejection of tumor metastasis without any effect on primary tumor growth. Our current aim was to investigate the effects of cyclophosphamide on the expression of IL-10 and IL-10R on primary and metastatic L-TACB cells. Considering that cyclophosphamide is a prodrug, we used mafosfamide, a compound that yields in vitro the same active metabolites as cyclophosphamide does in vivo. Mafosfamide induced down-regulation of IL-10 production and IL-10R expression on metastatic cells and, concomitantly, inhibited metastatic cell proliferation. We suggest that mafosfamide would inhibit the regulatory loop mediated by the IL-10/IL-10R system and, as a consequence, metastatic cell proliferation. These results may have a considerable impact on the design of new therapies for metastatic lymphomas.

Background A major barrier to treatment of leptomeningeal disease is the lack of proven combination chemotherapy regimens for intrathecal administration. The purpose of this study was to determine the cytotoxic effects of karenitecin and mafosfamide in vitro against leukemia, medulloblastoma, and neuroblastoma cell lines. Procedure A modified methyl tetrazolium (MTT) assay was used to determine the sensitivity of the cells to karenitecin and mafosfamide. Cells were exposed to drug for 72 hr, after which the number of surviving cells was quantitated. For drug combination experiments, cells were exposed to medium alone (controls), single drugs alone (mafosfamide only, karenitecin only) or to different concentrations of the combination of the two drugs (karenitecin + mafosfamide), for a total of 36 concentration pairs per plate. The universal response surface approach (URSA) was used to analyze the cytotoxic effects of the combination of karenitecin and mafosfamide. Results The IC50s of karenitecin and mafosfamide for the various cell lines were similar. For both drugs nearly complete inhibition of cell growth was demonstrated at higher concentrations in all cell lines. In the neuroblastoma cell lines (SK-N-DZ; SK-N-SH) and the DAOY medulloblastoma cell line, the combination of karenitecin and mafosfamide were synergistic. In the D283 medulloblastoma and both the leukemia cell lines (JM1 and Molt-4), the drug interaction was additive. Antagonism was not seen in any cell line. Conclusions Karenitecin and mafosfamide are additive or synergistic in vitro against tumor types that disseminate to the leptomeninges. These results provide guidance for the choice of potential combination intrathecal regimens. Pediatr Blood Cancer 2008;50:757–760. © 2007 Wiley-Liss, Inc.

A fundamental problem in cancer drug development is that antitumor efficacy in preclinical cancer models does not translate faithfully to patient outcomes. Much of early cancer drug discovery is performed under in vitro conditions in cell-based models that poorly represent actual malignancies. To address this inconsistency, we have developed a technology platform called CIVO, which enables simultaneous assessment of up to eight drugs or drug combinations within a single solid tumor in vivo. The platform is currently designed for use in animal models of cancer and patients with superficial tumors but can be modified for investigation of deeper-seated malignancies. In xenograft lymphoma models, CIVO microinjection of well-characterized anticancer agents (vincristine, doxorubicin, mafosfamide, and prednisolone) induced spatially defined cellular changes around sites of drug exposure, specific to the known mechanisms of action of each drug. The observed localized responses predicted responses to systemically delivered drugs in animals. In pair-matched lymphoma models, CIVO correctly demonstrated tumor resistance to doxorubicin and vincristine and an unexpected enhanced sensitivity to mafosfamide in multidrug-resistant lymphomas compared with chemotherapy-naïve lymphomas. A CIVO-enabled in vivo screen of 97 approved oncology agents revealed a novel mTOR (mammalian target of rapamycin) pathway inhibitor that exhibits significantly increased tumor-killing activity in the drug-resistant setting compared with chemotherapy-naïve tumors. Finally, feasibility studies to assess the use of CIVO in human and canine patients demonstrated that microinjection of drugs is toxicity-sparing while inducing robust, easily tracked, drug-specific responses in autochthonous tumors, setting the stage for further application of this technology in clinical trials.

It has been previously revealed that statins used at high concentrations display antileukemic potential towards chronic lymphocytic leukemia (CLL) cells. However, their usage alone in clinical practice may be limited due to possible side effects of high doses of these drugs. On the other hand, combined treatment of leukemia with statins and the conventional chemotherapeutics is questionable because of unknown influence of the first on the standard treatment results. This study has revealed that in vitro atorvastatin increases the proapoptotic potential of cladribine and mafosfamide in CLL cells isolated from peripheral blood of patients. Moreover, a preincubation with the above statin sensitizes leukemic cells to CM-induced apoptosis even at small concentrations of the drug. The usage of atorvastatin together with or followed by the conventional chemotherapy should be considered as therapeutic option for the treatment for this leukemia. Interestingly, CM-resistant patients might have the biggest benefits from atorvastatin administration. Grant no. 1407 from the University of Łódź.

Leptomeningeal carcinomatosis is defined as malignant infiltration of the pia matter and arachnoid membrane. Leukaemias and lymphomas, lung, breast cancer and melanoma are the primary tumours commonly associated with leptomeningeal carcinomatosis. Diagnosis is based on compatible symptoms and signs, cytological evidence of malignancy in the cerebrospinal fluid, and neuroimaging studies. Treatment is largely palliative (median survival 2 - 4 months). Patients with lympomatous or leukaemic meningitis, chemosensitive tumours such as breast cancer, low tumour burden, minimal neurological deficits, good performance status and controllable systemic disease survive longer with occasional long-term responses. Available treatment options include focal radiation therapy to CNS sites of bulky, symptomatic or obstructive meningeal deposits, intrathecal cytotoxic therapy and systemic chemotherapy. No evidence of superiority of intrathecal treatment compared with best palliative care (including radiation therapy and systemic treatment) is available from clinical trials. Novel treatment approaches include intrathecal liposomal Ara-C, the development of new cytotoxic compounds, signal transduction inhibitors and monoclonal antibodies for intrathecal or systemic use. Until data from multi-centre randomised trials are available, rationalisation of therapy should be done by stratifying patients to prognostic groups. High-risk patients will only survive for a few weeks and are better managed with supportive measures, whereas low-risk patients justify vigorous cerebrospinal fluid-directed treatment combined with radiation therapy and systemic chemotherapy. © 2005 Ashley Publications Ltd. 6 7 1115 1125

We have analyzed the long-term outcome and toxicities in 98 patients with high-risk acute myelogenous leukemia (AML) who were treated with autologous bone marrow transplantation (ABMT) and monitored for a median observation period of 11.67 years. Between 1983 and 1994, 98 patients in our institution in first or second and higher complete remission (CR) underwent total body irradiation and high-dose cyclophosphamide prior to ABMT purged with mafosfamide. Twenty-seven out of the 90 evaluable patients (30%) were alive and in continuous CR for a median of 11.67 years (range, 6.39-15.53) after ABMT and could be considered as 'cured'. Among the 90 patients, 39 were transplanted at first CR and had a significantly higher survival rate than those transplanted ator = 2 CR. Younger patients (40 years) had a better prognosis and patients with FAB M1-4 had a more favorable outcome than those with M5. Long-term complications included four patients with cardiac complications, two with renal insufficiency. Five developed HCV infections, four myelodysplastic syndrome. The incidence of cataract among the long-term survivors was 44.4%. Therefore, a significant number of adult patients with AML in first CR derived long-term benefit from ABMT, despite the risks of a few long-term complications and of MDS (4.4%).

Purpose: Diffuse malignant pleural mesothelioma is the most common primary pleural malignancy. At the beginning of the last century, this tumor was of minor incidence. Meanwhile, the use of asbestos has led to and is still leading to a rise in pleural mesothelioma incidence. There is no standard therapy for this highly aggressive disease and the development of new therapeutic strategies is imperative. Methods: We, therefore, investigated the morphological and pharmakokinetic effects of a combined thermochemotherapy consisting of the administration of different dosages of mafosfamide with and without the application of a 1-h hyperthermia at 41.7 °C on the human biphasic malignant pleural mesothelioma cell line MSTO-211H. After therapy, cells were prepared for light and electron microscopy. BrdU-incorporation for the S-phase fraction, TUNEL-labeling for detection of apoptosis, and quantitative assessments using the MTT assay were performed. Results: Our results demonstrate that the combination of mafosfamide with hyperthermia leads to qualitatively and quantitatively enhanced cellular damage compared to monotherapy. During combined thermochemotherapy, cell damage and death is already induced at lower mafosfamide concentrations than without hyperthermia which suggests an additive effect from hyperthermia to the action of the alkylating drug mafosfamide. Cell death thereby mostly occurs as necrotic cell death rather than as apoptosis, although in a combined thermochemotherapy apoptosis is induced temperature-dependently, when comparing temperatures from 37 °C to 43 °C. Conclusions: We suggest that the effect of substances such as ifosfamide and cyclophosfamide which are in clinical use, might be enhanced by the combination of local or regional hyperthermia in order to improve the therapeutical index of these substances in the treatment of pleural mesothelioma.

To improve the efficacy of therapeutic options in chronic lymphocytic leukemia (CLL) an in vitro system to determine the response of mononuclear blood cells from blood of patients was elaborated. The study combines four approaches, i.e., cell viability, apoptosis rate, differential scanning calorimetry (DSC), and immunoblotting to develop personalized therapy protocols based on the cell sensitivity to drug exposure of individual CLL patients. The complementary analyses were performed on 28 peripheral blood samples from previously untreated CLL patients before therapy. The induction and progress of apoptosis in CLL cells exposed in vitro to purine analogs combined with mafosfamide, i.e., cladribine + mafosfamide (CM) and fludarabine + mafosfamide (FM) were assessed using the above approaches. The changes in thermal profiles (decrease/loss of transition at 95±5˚C) coincided with an accumulation of apoptotic cells, a decrease in the number of viable cells, and differences in the expression of the apoptosis‑related protein PARP‑1. No significant changes were observed in the thermal profiles of nuclei isolated from CLL cells resistant to the treatment. The complementary assays revealed a strong relationship between both the in vitro sensitivity of leukemia cells to drugs and the clinical response of the patients, determined usually after the sixth course of treatment (after ~6 months of therapy). As a summary of studies followed by complementary tests, our findings demonstrate the value of in vitro exposure of CLL cell samples to drugs intended to treat CLL patients, before their administration in order to recommend the most suitable and effective therapy for individual patients.

Aldehyde dehydrogenase enzymes irreversibly oxidize aldehydes generated from metabolism of amino acids, fatty acids, food, smoke, additives, and xenobiotic drugs. Cyclophosphamide is one such xenobiotic used in cancer therapies. Upon activation, cyclophosphamide forms an intermediate, aldophosphamide, which can be detoxified to carboxyphosphamide by aldehyde dehydrogenases (ALDH), especially ALDH1A1 and ALDH3A1. Consequently, selective inhibition of ALDH3A1 could increase chemosensitivity toward cyclophosphamide in ALDH3A1 expressing tumors. Here, we report detailed kinetics and structural characterization of a highly selective submicromolar inhibitor of ALDH3A1, 1-[(4-fluorophenyl)sulfonyl]-2-methyl-1H-benzimidazole (CB7, IC50 of 0.2 μM). CB7 does not inhibit ALDH1A1, ALDH1A2, ALDH1A3, ALDH1B1, or ALDH2 activity. Structural, kinetics, and mutagenesis studies show that CB7 binds to the aldehyde binding pocket of ALDH3A1. ALDH3A1-expressing lung adenocarcinoma and glioblastoma cell lines are sensitized toward mafosfamide (MF) treatment in the presence analogues of CB7, whereas primary lung fibroblasts lacking ALDH3A1 expression, are not.

Ranpirnase (onconase; ONC) is an endoribonuclease obtained from the frog Rana pipiens. This enzyme exhibits anticancer properties mediated by degradation of cellular RNA and induction of apoptosis. In this study we assessed cytotoxicity of ONC in combination with currently used anticancer drugs on a human diffuse large B-cell lymphoma (DLBCL)-derived cell line (Toledo). Cytotoxic activity was measured by the exclusion of propidium iodide assay while apoptosis was assessed using the annexin-V binding method. Additionally, flow cytometry was used to assess the decline of mitochondrial potential and to determine activation of caspases 3, 8 and 9. It was observed that in vitro treatment with ONC in combination with rituximab, mafosfamide, vincristine, doxorubicin, and dexamethasone (drugs corresponding with elements of R-CHOP regimen) resulted in increased cytotoxicity. As a result ONC showed marked cytotoxicity against Toledo cells. Importantly, in combination of ONC with drugs imitating the R-CHOP regimen, this effect was significantly intensified. The main mechanism responsible for this event was induction of apoptosis along a mitochondrial dependent pathway. In conclusion, these data indicate that further preclinical and eventually clinical studies assessing activity of ONC+R-CHOP treatment are warranted.

A hundred and eight patients less than 60 years old with de novo acute myeloid leukemia were treated between 1982 and 1994 by protocols including final intensification with a transplant using autologous bone marrow purged by mafosfamide in first remission in the absence of an HLA-matched sibling donor available for allograft. From 1989, we attempted to improve tumor control by using high-dose anthracyclines in induction, by increasing from one to two the number of consolidation courses pre-transplant and by introducing intermediate doses of cytarabine in the first consolidation course. The CR rate was 77% (33/43) before 1989 and 90% (59/65) after 1989 (P = 0.06). Forty-five out of the 59 patients (76%) who achieved CR after 1989 could undergo bone marrow grafting in CR1 vs 16/33 (48%) before 1989 (P = 0.01). In spite of the higher proportion of patients above 50 years after 1989 (32%) toxicity was mild and an adequate graft was obtained more frequently after one collection. The principal factor relating to improvement in graft feasibility was the post-1989 modification of induction and consolidation regimens. This improvement in graft feasibility was associated with a better disease-free survival (DFS) (48 +/- 7% vs 32 +/- 8%, P = 0.04) and overall survival (OS) (53 +/- 6% vs 30 +/- 7%, P = 0.007) at 5 years. By multivariate analysis four factors were associated with overall survival (OS): karyotype, white blood cell count at diagnosis, treatment regimen and bone marrow grafting in CR1. This global approach should be prospectively compared with intensive chemotherapy.

We report our long-term experience with autologous bone marrow transplantation (ABMT) for 32 adult patients with acute lymphocytic leukaemia (ALL) in second or later remission (CR), or in first CR but with high-risk. Bone marrow was purged with mafosfamide (n = 25) or with immunomagnetic beads and monoclonal antibodies (n = 7). Retrospective analysis showed that 12 out of 32 patients were in continuous complete remission (CCR) at a median of 143 months (range 66-181 months). A plateau was reached at 50 months and the disease-free and overall survival rates were both 37.5%. It was notable that durable CCR could be achieved for patients in second (three out of nine) or third (one out of six) CR. ABMT could produce durable CCR and the long-term outcome compared favourably with those reported for allogeneic transplantation.

We report the feasibility of ex vivo mafosfamide treatment of peripheral blood stem cells (PBSCs) collected by leukapheresis instead of bone marrow in a single patient with acute myeloid leukemia FAB M1. Mononuclear cells (MNC) (2 ×107/ml) were incubated with 50 µg/ml mafosfamide (30 min, 37 °C) in phosphate-buffered saline supplemented with 1% HSA, resulting in a marked reduction of BFU-E (94%) and CFU-GM (90%). The hematopoietic recovery was slightly delayed comparable to bone marrow grafts, with neutrophils > 500/µl at day 15 and platelets > 20,000/µl at day 45. In consideration of several factors influencing the drug toxicity, mafosfamide can be used in PBSC products just as in bone marrow harvests. This observation opens the field of pharmacological purging strategies for departments of transfusion medicine and hematology specialized in collecting and processing PBSC products in consideration of the good manufacturing practice guidelines used.

In the present study the in vitro growth of CFU-GM from PBPC of patients with AML (n = 11), purged with mafosfamide alone or a combination of mafosfamide and amifostine, was compared to historical controls of mafosfamide-purged bone marrow (AML CR1, n = 16). Two patients were transplanted with mafosfamide and mafosfamide/amifostine pretreated PBPC autografts. The in vitro experiments demonstrated a significantly higher resistance of peripheral blood derived CFU-GM to mafosfamide (median ID95 190 μg mafosfamide/ml) compared with bone marrow derived CFU-GM (median ID95130 μg/ml). Preincubation with amifostine significantly further increased the median ID95 to 245 μg/ml. the clinical results showed short recovery times for neutrophils >500/μl (9 and 13 days) and platelets >20 000/μl (12 and 21 days) and stable long-term engraftment with one relapse at day +118 and one patient in CR at day 760 after transplantation. The in vitro results show a significant advantage of PBPC over bone marrow-derived progenitors for purging with mafosfamide. Furthermore, a protective effect from mafosfamide of amifostine on normal progenitors could be demonstrated. The clinical results demonstrate the clinical feasibility of using mafosfamide-purged autologous PBPCT without impairing the short-term and long-term repopulating capacities of the autografts. Bone Marrow Transplantation (2000) 25, 831–836.

Purpose: Modulation of DNA repair represents one strategy to overcome cellular drug resistance to alkylating agents and platinum compounds. The effects of different known DNA repair modulators such as O 6-benzylguanine (6 μg/ml), fludarabine (25 ng/ml), aphidicolin (8.5 ng/ml), pentoxifylline (1.4 μg/ml) and methoxamine (12.4 μg/ml) on the cytotoxicity of mafosfamide, chlorambucil, 1,3-bis-(2-chloroethyl)-1-nitrosourea (BCNU), cisplatin and carboplatin were tested in human lung cancer cell lines. Methods: Chemosensitivity of the human adenocarcinoma cell line MOR/P and the cisplatin-resistant subline MOR/CPR as well as the large-cell lung cancer cell line L23/P and its cisplatin-resistant counterpart L23/CPR were evaluated by the MTT colorimetric assay. Results: O 6-benzylguanine, an inhibitor of O 6-alkylguanine-DNA alkyltransferase, significantly sensitised MOR/P and MOR/CPR cells to the cytotoxic effect of BCNU. Fludarabine, methoxamine and aphidicolin did not change the chemosensitivity of the parental and cisplatin-resistant cell lines to any cytotoxic drug tested. Interestingly, O 6-benzylguanine enhanced the chemoresistance of parental and cisplatin-resistant cell lines to platinum compounds. Also, pentoxifylline increased resistance of the MOR cell lines to mafosfamide. Conclusions: Modulation of DNA repair elicits not only chemosensitisation but may also enhance cellular resistance to DNA-affine drugs.

Several prospective randomized trials in acute myelocytic leukemia (AML) documented a lower relapse rate with autologous bone marrow transplantation (ABMT) than with conventional chemotherapy. However, they also identified some transplant difficulties, such as failure to collect sufficient numbers of stem cells, slow kinetics of engraftment, and a high transplant-related mortality that diminished or negated positive impact on overall survival. Data for ABMT are inconclusive in acute lymphocytic leukemia (ALL) in adults. We retrospectively analyzed patients with acute leukemia autografted with marrow purged with mafosfamide after January 1983 in our institution. The population comprised 229 consecutive patients; 165 with AML [123 in first remission (CR1), 32 in second remission (CR2)]; 61 with ALL (46 in CR1, 4 in CR2); and 3 with undifferentiated acute leukemia. All patients were autografted with marrow purged with mafosfamide. Mafosfamide was given at a constant dose of 50 μg/mL in 103 and adjusted individually to produce a CFU-GM LD 95 (5% residual CFU-GM post purging) in 126. The outcome was analyzed for correlation with patient characteristics, the disease including cytogenetics, and the graft itself. Prognostic factors identified by multivariate analysis were used to derive a prognostic classification. Patients receiving higher doses of marrow submitted to purging (>5.46 × 10 4 CFU-GM/kg) experienced a lower treatment-related mortality (RR = 0.11, p=0.005) and a higher leukemia-free (RR = 0.5, p=0.005) and overall survival (RR = 0.4, p=0.001). Patients receiving 5.46 × 10 4 CFU-GM/kg and doses actually infused post purging of ≤0.02 × 10 4 /kg had a treatment-related mortality of only 2 ± 2%, a leukemia-free survival of 70%, and an overall survival of 77 ± 7% at 10 years. In this study of autotransplantation for acute leukemia using mafosfamide-purged marrow, the stem cell dose used for purging and the intensity of purging were the most important factors predicting outcome.

Because 2-chloro-2'-deoxyadenosine (CdA) is active in B-chronic lymphocytic leukemia (B-CLL), and may interfere with DNA repair, we investigated the potentiating effect of CdA on the cytotoxicity induced in vitro in B-CLL lymphocytes by cyclophosphamide (CP) derivatives, which induce DNA damage by DNA cross-linking. Exposure to CdA at clinically achievable concentrations for 2 h, followed by mafosfamide (MAF) or 4-hydroxycyclophosphamide (4HC) for 22 h, resulted in synergistic cytotoxicity in the majority of B-CLL samples tested. Synergy between CdA and MAF was observed in cell samples of sensitive/untreated patients, as well as in cells of resistant/pretreated patients, particularly at the highest concentrations of MAF. In the cells treated with CdA and MAF, we observed loss in ATP and hallmarks of apoptosis, as evidenced by cellular morphology and high molecular weight DNA fragmentation. The synergy could be explained neither by an influence of MAF on the phosphorylation of CdA, nor by an increase in the incorporation of CdA into DNA in the presence of MAF. The in vitro synergy between CdA and CP derivatives provides a rationale for the use of this association in B-CLL patients.

Radio- and chemotherapy for the treatment of malignancies are often associated with significant toxicity. One approach to reduce the toxicity is the concomitant treatment with chemoprotective agents. This article reviews two sulfhydryl compounds, namely the agent WR-2721 (amifostine), a compound recently registered for use in human in many countries, and the natural occurring compound glutathione (GSH). GSH is not registered as a chemoprotective agent. WR-2721 is an aminothiol prodrug and has to be converted to the active compound WR-1065 by membrane-bound alkaline phosphatase. WR-1065 and GSH both act as naturally occurring thiols. No protective effect on the tumour has been found when these compounds are administered intravenously. There is even in vitro evidence for an increased anti-tumour effect with mafosfamide after pretreatment with WR-2721, and in vivo after treatment with carboplatin and paclitaxel. Randomized clinical studies have shown that WR-2721 and GSH decrease cisplatin-induced nephrotoxicity and that WR-2721 reduces radiation radiotherapy-induced toxicity. Side-effects associated with WR-2721 are nausea, vomiting and hypotension, GSH has no side-effects. An exact role of WR-2721 and GSH as chemoprotectors is not yet completely clear. Future studies should examine the protective effect of these drugs on mucositis, cardiac toxicity, neuro- and ototoxicity, the development of secondary neoplasms and their effect on quality of life. © 1999 Cancer Research Campaign

Summary. Bone marrow (BM) samples from 24 patients with acute leukaemia (AML 17, ALL seven) in first complete remission were compared to samples from 10 normal donors with regard to their content in long-term culture-initiating cells (LTC-IC) as assessed by a limiting dilution assay and the clonogeneic capacity of these cells, in order to determine whether remission marrow cells displayed any specific defect at the primitive stem cell level. The frequency of LTC-IC in the whole patient group was 1 in 3487 6 3125 mononuclear cells (MNC) as compared to 1 in 794 6 492 MNC in normal controls (P o 0·0009), with no difference between AML and ALL. Moreover, the clonogeneic capacities were 2·66 6 0·7 (range 1·8‐1·6) and 4·0 6 1·6 (range 2·2‐7·9) CFC per LTC-IC in patients and controls respectively (P o 0·0015). These quantitative and qualitative defects were aggravated by treatment with mafosfamide at a dose of 50 mg/10 7 MNC/ ml, where the mean recovery of LTC-IC after in vitro purging was 42%. In nine patients autografted with purged marrow following high-dose radiochemotherapy, no correlation could be detected between the dose of LTC-IC (mean 6742 6 7877/kg) and the kinetics of recovery of haemopoiesis. We concluded that, in acute leukaemia patients in complete remission, the presumably normal residual stem cell pool was not only quantitatively diminished but also qualitatively altered in its capacity to give rise to clonogeneic progenitor cells.

BACKGROUND Philadelphia cells are human chronic myelogenous leukemia (CML) cells that contain the BCR/ABL oncogene (a fusion of the BCR and ABL genes). Selective eradication of these cells in vitro can be achieved by combined treatment with antisense phosphorothioate oligodeoxynucleotides ([S]ODNs) specifically targeted to this oncogene (bcr/abl [S]ODNs) and a suboptimal (for use as a single agent) dose of mafosfamide (the in vitro active form of cyclophosphamide). PURPOSE We evaluated the ability of bcr/abl antisense [S]ODNs, alone or subsequent to treatment with a single injection of cyclophosphamide, to suppress the leukemic process induced in severe combined immunodeficient (SCID) mice by Philadelphia cells (i.e., primary CML-blast crisis [CML-BC] cells). In addition, we studied potential mechanisms that might explain the efficacy of the bcr/abl antisense [S]ODN-mafosfamide combination against Philadelphia cells in vitro. METHODS The effects of treating leukemic mice with cyclophosphamide (25 mg/kg body weight; 25% of the dose required to eradicate evidence of leukemia in SCID mice) and/or bcr/abl antisense [S]ODNs were assessed by analysis of survival, by examination of bone marrow for the presence of leukemia cells (using a colony formation assay or using coupled reverse transcription and the polymerase chain reaction to screen for bcr/abl messenger RNA), and by examination of a variety of tissues for the presence of infiltrating leukemia cells. The induction of apoptosis (a cell death program) in vitro in primary CML-BC cells following treatment with bcr/abl antisense [S]ODNs plus or minus prior treatment with mafosfamide was monitored by use of a commercial assay. Relative cellular uptake of [S]ODNs by CML-BC cells treated in vitro with or without prior treatment with mafosfamide was determined by use of confocal microscopy and flow cytometry (for fluorescent [S]ODNs) or by use of blotting techniques that employed radioactively labeled probes (for extracted, unlabeled [S]ODNs). Levels of specific proteins in treated and untreated cells were determined by use of western blotting methods. Reported P values are two-sided. RESULTS The disease process in leukemic mice was retarded substantially by combination treatment with cyclophosphamide and specific bcr/abl antisense [S]ODNs (P < .001, relative to treatment with specific antisense [S]ODNs alone, cyclophosphamide alone, or cyclophosphamide plus nonspecific [i.e., control] antisense [S]ODNs); 50% of the mice treated with cyclophosphamide and specific antisense [S]ODNs appeared to be cured of leukemia. The combination treatment was associated with increased induction of apoptosis. In addition, cellular uptake of bcr/abl antisense [S]ODNs appeared to be increased twofold to sixfold by prior treatment with mafosfamide. This increased uptake of [S]ODNs was associated with enhanced suppression of p210bcr/abl protein levels. CONCLUSIONS AND IMPLICATIONS Combination therapy with antisense [S]ODNs targeted to specific oncogenes and less toxic doses of anticancer drugs may represent a rational strategy to purpose for the treatment of human leukemias.

High-dose, posttransplantation cyclophosphamide (PTCy) is an effective strategy for preventing graft-versus-host disease (GVHD) after allogeneic blood or marrow transplantation (alloBMT). However, the mechanisms by which PTCy modulates alloimmune responses are not well understood. We studied early T cell reconstitution in patients undergoing alloBMT with PTCy and the effects of mafosfamide, a cyclophosphamide (Cy) analog, on CD4(+) T cells in allogeneic mixed lymphocyte reactions (MLRs) in vitro. Patients exhibited reductions in naïve, potentially alloreactive conventional CD4(+) T cells with relative preservation of memory CD4(+)Foxp3(+) T cells. In particular, CD4(+)CD45RA(-)Foxp3(+hi) effector regulatory T cells (Tregs) recovered rapidly after alloBMT and, unexpectedly, were present at higher levels in patients with GVHD. CD4(+)Foxp3(+) T cells from patients and from allogeneic MLRs expressed relatively high levels of aldehyde dehydrogenase (ALDH), the major in vivo mechanism of Cy resistance. Treatment of MLR cultures with the ALDH inhibitor diethylaminobenzaldehyde reduced the activation and proliferation of CD4(+) T cells and sensitized Tregs to mafosfamide. Finally, removing Tregs from peripheral blood lymphocyte grafts obviated PTCy's GVHD-protective effect in a xenogeneic transplant model. Together, these findings suggest that Treg resistance to Cy through expression of ALDH may contribute to the clinical activity of PTCy in preventing GVHD.

Shiga toxin 1 (Stx1), produced by pathogenic Escherichia coli, targets a restricted subset of human cells, which possess the receptor globotriaosylceramide (Gb3Cer/CD77), causing hemolytic uremic syndrome. In spite of the high toxicity, Stx1 has been proposed in the treatment of Gb3Cer/CD77-expressing lymphoma. Here, we demonstrate in a Burkitt lymphoma cell model expressing this receptor, namely Raji cells, that Stx1, at quasi-non-toxic concentrations (0.05–0.1 pM), inhibits the repair of mafosfamide-induced DNA alkylating lesions, synergistically potentiating the cytotoxic activity of the anticancer drug. Conversely, human promyelocytic leukemia cells HL-60, which do not express Gb3Cer/CD77, were spared by the toxin as previously demonstrated for CD34+ human progenitor cells, and hence, in this cancer model, no additive nor synergistic effects were observed with the combined Stx1/mafosfamide treatment. Our findings suggest that Stx1 could be used to improve the mafosfamide-mediated purging of Gb3Cer/CD77+ tumor cells before autologous bone marrow transplantation.

Expression of class 3 aldehyde dehydrogenase (ALDH-3) has been associated with acquired or inherent resistance to oxazaphosphorine (OAP) antineoplastic alkylating agents (e.g. cyclophosphamide). We previously demonstrated that expression of transfected rat ALDH-3 can confer OAP-specific resistance in human MCF-7 cells (Bunting, K. D., Lindahl, R., and Townsend, A. J. (1994) J. Biol. Chem. 269, 23197-23203). However, the aldophosphamide intermediate inactivated by human class 1 ALDH (hALDH-1) has not proven to be a good substrate for the purified hALDH-3. We have examined the ability of transfected human or rat ALDH-3 to confer OAP resistance in V79/SD1 cells. Clones expressing elevated human (386-5938 milliunits/mg) or rat (4-597 milliunits/mg, benzaldehyde/NADP+ substrate) ALDH-3 activity were 1.3- to 12-fold resistant to mafosfamide relative to control cells (

Current assays of human committed-stem cells are of limited value in predicting the rate of engraftment or in assessing the integrity of the stem cell pool after allogeneic bone marrow (BM) transplantation (BMT). We have used a limiting dilution assay of mafosfamide-resistant progenitors (pre-colony-forming units [CFU]), which are ancestral to committed progenitors such as CFU-granulocyte-macrophage (GM) to analyze the kinetics of myeloid engraftment after BMT and to assess the size of the stem cell pool at intervals up to 66 months thereafter. In 24 patients transplanted for chronic myeloid leukemia in chronic phase (eight with matched unrelated donors and 16 with sibling donors), the rate of neutrophil engraftment correlated strongly with the number of pre-CFU transfused per kilogram recipient body weight (r = .7, P < .005) but not with CFU-GM per kilogram or nucleated cells per kilogram. In 25 patients studied 6 to 66 months after allogeneic BMT, the mean number of pre-CFU in the marrow was 3.1/10(5) mononuclear cells (MNC) (median, 3.47; range, 0.4 to 23.3), compared with 24.7/10(5) MNC (median, 27.3; range, 4.2 to 180) in 25 normal subjects. CFU-GM were also reduced in these patients, but with considerable overlap into the normal range (mean +/- SD: 54 +/- 45.6 per 10(5) MNC; normal, 129 +/- 61.6). Low pre-CFU but not low CFU-GM levels were associated with reduced peripheral blood white blood cell counts in post-BMT patients. Pre-CFU and CFU-GM levels were not related to the interval posttransplant and remained low for up to 66 months. We conclude that the pre-CFU assay measures a population of stem/progenitor cells that are important in the kinetics of engraftment after allogeneic BMT. Our data suggest that pre-CFU levels may remain low for some years after BMT in humans.

The DNA repair protein O6-methylguanine-DNA methyltransferase (MGMT) removes alkyl groups from the O6 position of guanine in DNA and thus may protect cells against genotoxic effects of agents inducing this lesion. To analyze quantitatively the level of protection mediated by MGMT against antineoplastic drugs, we determined the cytotoxic and recombinogenic (sister-chromatid exchange inducing) effects of various chemotherapeutic agents in a pair of isogenic Chinese hamster cell lines deficient and proficient for MGMT, generated upon transfection with human MGMT cDNA. Furthermore, we compared the responses of the human cell lines HeLa MR (MGMT deficient) and HeLa S3 (MGMT proficient) to the various agents. It is shown that: (1) MGMT proficient cells are resistant in cell killing to the methylating drug streptozotocin and all the chloroethylating nitrosoureas tested. There was a marked agent specificity in protection. The level of resistance provoked by MGMT increased in the order BCNU < CCNU < ACNU < HeCNU < streptozotocin. (2) MGMT did not protect cells against killing induced by chlorambucil, cisplatin, melphalan, activated cyclophosphamide (malosfamide) and activated ifosfamide (4-hydroperoxy-ifosfamide). (3) MGMT caused protection against the recombinogenic effect of all nitrosoureas tested. The lowest level of protection was again observed for BCNU, followed by CCNU, ACNU < HeCNU < streptozotocin. (4) MGMT proficient cells did not exhibit resistance in SCE induction towards cyclophosphamide (activated by microsomes), 4-hydroperoxy-ifosfamide, mafosfamide, chlorambucil and melphalan. Some protection was afforded, however, against cisplatin (and transplatin). This effect was abolished by pretreatment of cells with O6-benzylguanine, which depletes MGMT, indicating that some lesion(s) induced by cisplatin giving rise to SCEs can be repaired by MGMT. Taken together, these results indicate that streptozotocin, HeCNU and ACNU are more selective than CCNU and BCNU in killing MGMT deficient cells, and that in the cases of cyclophosphamide, ifosfamide, chlorambucil, cisplatin and melphalan MGMT is not involved in mediating cytotoxic drug resistance.

We have studied the anti-tumor response to cyclophosphamide (CTX) in DBA/2 mice transplanted s.c. with 4 tumors exhibiting different responses to IL-2: ESb lymphoma and Friend leukemia cells (non-responsive or poorly responsive, respectively), pI I-R-Eb and Eb lymphoma cells (both highly responsive to IL-2). CTX injections on days 7, 14 and 21 resulted in a significant anti-tumor response in mice transplanted s.c. with Friend leukemia cells or ESb cells, whereas no anti-tumor effect was observed in mice injected with Eb or pI I-R-Eb cells. All 4 tumor cell lines were equally sensitive to the cytotoxic effects of mafosfamide, an in vitro active analogue of CTX. To define the host mechanisms responsible for the lack of an anti-tumor effect of CTX in mice transplanted with IL-2-responsive tumors, we studied several aspects of the spontaneous or IL-2-induced anti-tumor response in mice transplanted with pI I-R-Eb cells. Injection of monoclonal antibodies (MAbs) to IFN-γ completely abolished the anti-tumor effects of IL-2. Using a Winn assay, clear-cut anti-tumor activity was found in spleen cells from mice transplanted with the IL-2-responsive tumors. This activity was abolished by CTX, which also abrogated the anti-tumor response to IL-2 in mice injected with pI I-R-Eb cells. Our results indicate an inverse correlation between sensitivity to IL-2 and response to CTX and emphasize the importance of initial host-tumor interaction in determining the type of response to IL-2 or CTX. © 1995 Wiley-Liss, Inc.