Selective mitomycin C and cyclophosphamide induction of apoptosis in differentiating B lymphocytes compared to T lymphocytes in vivo

Oxazaphosphorines combined with immune checkpoint blockers: dose-dependent tuning between immune and cytotoxic effects

Background

Oxazaphosphorines (cyclophosphamide (CPA), ifosfamide (IFO)) are major alkylating agents of polychemotherapy protocols but limiting their toxicity and increasing their efficacy could be of major interest. Oxazaphosphorines are prodrugs that require an activation by cytochrome P450 (CYP). CPA is mainly metabolized (>80%) to phosphoramide mustard while only 10%–50% of IFO is transformed in the alkylating entity, isophosphoramide mustard and 50%–90% of IFO release chloroacetaldehyde, a nephrotoxic and neurotoxic metabolite. Geranyloxy-IFO (G-IFO) was reported as a preactivated IFO to circumvent the toxic pathway giving directly the isophosphoramide mustard without CYP metabolization. The similarity in structure of CPA and IFO and the similarity in metabolic balance of CPA and G-IFO have led us to explore immunomodulatory effect of these components in mice and to investigate the combination of these oxazaphosphorines with immune checkpoint blockers (ICB).

Methods

The investigation of the immunomodulatory properties of IFO and G-IFO compared with CPA has been conducted through immune cell phenotyping by flow cytometry and analysis of the cytokine profile of T cells after ex-vivo restimulation. T cell-mediated antitumor efficacy was confirmed in CD4⁺ and CD8⁺ T cell-depleted mice. A combination of oxazaphosphorines with an anti-programmed cell death 1 (PD-1) antibody has been studied in MCA205 tumor-bearing mice.

Results

Studies on a MCA205 mouse model have demonstrated a dose-dependent effect of IFO and G-IFO on T cell immunity. These components in particular favored Th1 polarization when used at low dose (150 and eq. 100 mg/kg, respectively). Antitumor activity at low dose was abolished in mice depleted in CD4⁺ and CD8⁺ T cells. G-IFO at low dose (eq. 100 mg/kg) in combination with anti-PD-1 antidody showed high synergistic antitumor efficacy compared with IFO.

Conclusion

Oxazaphosphorines are characterized by a dual mechanism of antitumor action; low-dose schedules should be preferred in combination with ICB, and dose escalation was found to have better utility in polychemotherapy protocols where a conventional direct cytotoxic anticancer effect is needed. G-IFO, the novel oxazaphosphorine drug, has shown a better metabolic index compared with IFO as its metabolization gives mainly the alkylating mustard as CPA (and not IFO) and a best potential in combination with ICB.

Inflammatory Signals Regulate IL-15 in Response to Lymphodepletion

Induction of lymphopenia has been exploited therapeutically to improve immune responses to cancer therapies and vaccinations. Whereas IL-15 has well-established roles in stimulating lymphocyte responses after lymphodepletion, the mechanisms regulating these IL-15 responses are unclear. We report that cell surface IL-15 expression is upregulated during lymphopenia induced by total body irradiation (TBI), cyclophosphamide, or Thy1 Ab-mediated T cell depletion, as well as in RAG(-/-) mice; interestingly, the cellular profile of surface IL-15 expression is distinct in each model. In contrast, soluble IL-15 (sIL-15) complexes are upregulated only after TBI or αThy1 Ab. Analysis of cell-specific IL-15Rα conditional knockout mice revealed that macrophages and dendritic cells are important sources of sIL-15 complexes after TBI but provide minimal contribution in response to Thy1 Ab treatment. Unlike with TBI, induction of sIL-15 complexes by αThy1 Ab is sustained and only partially dependent on type I IFNs. The stimulator of IFN genes pathway was discovered to be a potent inducer of sIL-15 complexes and was required for optimal production of sIL-15 complexes in response to Ab-mediated T cell depletion and TBI, suggesting products of cell death drive production of sIL-15 complexes after lymphodepletion. Lastly, we provide evidence that IL-15 induced by inflammatory signals in response to lymphodepletion drives lymphocyte responses, as memory CD8 T cells proliferated in an IL-15-dependent manner. Overall, these studies demonstrate that the form in which IL-15 is expressed, its kinetics and cellular sources, and the inflammatory signals involved are differentially dictated by the manner in which lymphopenia is induced.

Peripheral CD24hi CD27+ CD19+ B cells subset as a potential biomarker in naïve systemic lupus erythematosus

AIM

B cells are likely to play critical roles in the pathogenesis of systemic lupus erythematosus (SLE). Our aim was to investigate the role of peripheral CD24(hi) CD27(+) CD19(+) B cells in Chinese patients with new-onset SLE.

METHOD

Peripheral CD24(hi) CD27(+) CD19(+) B cells were analyzed in 55 new-onset lupus and 36 healthy controls by flow cytometry. All SLE cases were treated with prednisolone and hydroxychloroquine during a 1-year follow-up. Thirteen cases were added with cyclophosphamide or mycophenolate mofetil. The CD24(hi) CD27(+) CD19(+) B cells were analyzed at days 0, 7, 14 and months 1, 3, 6, 9 and 12. Interleukin-10 (IL-10)-producing B cell was detected in eight naïve lupus and 10 healthy controls.

RESULTS

Compared to healthy controls, the frequency and number of primary circulating CD24(hi) CD27(+) CD19(+) B cells was significantly reduced in SLE cases (8.22 ± 3.48% vs. 31.67 ± 5.53%, P < 0.0001; 4.04 ± 2.85 vs. 38.66 ± 10.22 10(3) cells/mL, P = 0.0001) before treatment; IL-10(+) CD19(+) B cells and IL-10(+) CD24(hi) CD27(+) CD19(+) B cells also decreased in SLE. Interestingly, primary CD24(hi) CD27(+) CD19(+) B cells inversely correlated with SLE disease activity index (SLEDAI) score. Patients with arthritis and hematologic disorders had a lower primary CD24(hi) CD27(+) CD19(+) B cells. In 48 SLE cases who finished the 1-year follow-up, the frequency and number of CD24(hi) CD27(+) CD19(+) B cells increased from 8.26 ± 3.61% to 25.51 ± 4.56%; 3.99 ± 2.86 to 28.64 ± 11.81 10(3) cells/mm(3) (P < 0.0001), accompanied by a significantly decreased SLEDAI score. Of note, CD24(hi) CD27(+) CD19(+) B cells decreased in some flare cases with an elevated SLEDAI score.

CONCLUSION

These results demonstrate that a lower primary CD24(hi) CD27(+) CD19(+) B cells may be an immunologic aspect of new-onset SLE. CD24(hi) CD27(+) CD19(+) B cells may be a useful tool to evaluate lupus activity and monitor the response to therapy.

Effects of Lactoferrin on IL-6 Production by Peritoneal and Alveolar Cells in Cyclophosphamide-Treated Mice

Previous studies have shown that oral treatment with lactoferrin (LF) restores the immune response in cyclophosphamide (CP) immunocompromised mice. The aim of the present investigation was to determine the regulatory ability of LF on the production of interleukin 6 (IL-6) in peritoneal and alveolar cells, derived from CP-treated mice. CBA mice were injected with a single, intraperitoneal (i.p.) dose of CP (350 mg/kg body weight) followed by LF administered in drinking water (0.5% solution) for 21 days. The control counterparts were given water. Peritoneal and alveolar cells were isolated from mice and the production of IL-6, both spontaneous and lipopolysaccharide (LPS) induced, was determined in 24h cell cultures using a bioassay. The results showed increased production of IL-6 in both CP-treated mice and in mice given, in addition, LF. The administration of LF alone led also to an increase in IL-6 production by the cell cultures. Intravenous (i.v.) administration of LPS resulted in a significant increase in IL-6 serum levels in CP and CP/LF but not in LF-treated mice. Analysis of cell type composition in the peritoneal cavity revealed a strong increase in mastocyte and neutrophil content in CP and CP/LF-treated groups. Our findings suggest that enhanced IL-6 production in CP and CP/LF-treated mice may contribute to reconstitution of immune system function in immunocompromised mice.

Restoration of immune system function is accelerated in immunocompromised mice by the B-cell-tropic isoxazole R-11

BACKGROUND

Restoration of impaired immune response in immunocompromised patients is a crucial problem. In this study we evaluated the efficacy of isoxazole R-11 in reconstitution of the immune response in immunosuppressed mice.

METHODS

Mice were given a sublethal dose (250 mg/kg b.w.) of cyclophosphamide (CP). The cellular immune response to ovalbumin (OVA) and the humoral immune response to sheep erythrocytes (SRBC) were generated. R-11 was administered at repetitive, intraperitoneal doses (20 μg/mouse) until determination of the immune responses: 7 and 15 doses on alternate days for cellular and humoral immune response, respectively. For phenotypic studies R-11 was given per os, at a single dose of 20 μg/mouse. The ability of R-11 to affect interleukin- 6 (IL-6) production was determined in the whole human blood cell culture.

RESULTS

R-11 increased the content of CD19+ cells in the spleens and lymph nodes with a concomitant decrease of CD3+ and CD4+ cells. The compound significantly accelerated restoration of both cellular and humoral immune responses, elevated the numbers of circulating leukocytes and splenocytes and normalized the blood cell picture. Supplementary experiments showed that R-11 was not toxic with regard to human peripheral blood mononuclear cells (PBMC) and that it upregulated IL-6 production in blood cell culture stimulated with lipopolysaccharide (LPS).

CONCLUSIONS

We demonstrated that R-11 is likely a B-cell tropic agent which can restore both cellular and humoral immune responses in immunocompromised mice and may have a potential to be applied in therapy of immunocompromised patients.

The effects of bestatin on humoral response to sheep erythrocytes in non-treated and cyclophosphamide-immunocompromised mice

The effects of bestatin on humoral immune response to sheep erythrocytes (SRBC) and restoration of the response impaired by a single cyclophosphamide dose (350 mg/kg) were tested on mice. Bestatin (at doses of 10, 1, and 0.1 mg/kg) was administered intraperitoneally (i.p.) 5 or 10 times. The pharmacological immunosuppression was induced by a single i.p. injection of cyclophosphamide (350 mg/kg) administered 24 h before the first bestatin dose. The mice were immunized i.p. with SRBC 24 h after the last dose of bestatin. It was found that multiple administration of bestatin at all three doses potentiated the humoral response to SRBC in non-treated mice, resulting in an increased number of plaque-forming cells (PFC) and 2-mercaptoethanol (2-ME)-resistant anti-SRBC antibodies. However, five times administration of bestatin at the doses under investigation caused further decreases in total anti-SRBC hemagglutinins. A single injection of cyclophosphamide (350 mg/kg) suppressed humoral response of mice to the antigen. Administration of bestatin after pharmacological immunosuppression partially prevented the suppressive action of cyclophosphamide in the in vivo model of the humoral immune response to SRBC. The protective action of bestatin was both dose- and schedule-dependent. Ten times' exposure to a bestatin dose of 0.1 mg/kg after a high cyclophosphamide dose partially reduced the suppressive effect of this drug on humoral response of SRBC-immunized mice, increasing PFC on days 4 and 7 after immunization, which coincided with restored ability of the lymphocytes to produce the 2-ME-resistant hemagglutinins on day 7 and the total anti-SRBC hemagglutinins on day 14 after priming.

Cyclophosphamide promotes engraftment of gene-modified cells in a mouse model of Fanconi anemia without causing cytogenetic abnormalities

A major hurdle for hematopoietic stem cell (HSC) gene therapy for inherited bone marrow disorders, including Fanconi anemia (FA), is adequate engraftment of gene-modified cells. A phenotypic defect in DNA repair renders FA patients sensitive to alkylating agents such as cyclophosphamide (Cy); however, at lower doses, Cy is well tolerated in the FA transplant setting. We tested whether non-alkylating agents could replace Cy for pretransplant conditioning to enhance engraftment of FANCA gene-modified hematopoietic cells. We compared Cy preconditioning with fludarabine (Flu) or cytarabine (AraC) or no conditioning as a control in fanca ( -/- ) mutant mice receiving gene-modified bone marrow cells. Only mice conditioned with Cy exhibited appreciable engraftment of gene-modified cells by PCR and resistance to mitomycin C (MMC). Cy administration following transplantation increased gene marking levels in all animals treated, but highest gene marking and corresponding MMC resistance were observed in mice receiving Cy pre- and posttransplantation. Importantly, no cytogenetic abnormalities were observed in Cy-treated mice. We conclude that Cy is an effective and superior preparative regimen with respect to engraftment of lentivirus-transduced cells and functional correction in fanca ( -/- ) mice. Thus, appropriately dosed Cy may provide a suitable conditioning regimen for FA patients undergoing HSC gene therapy.

Cyclophosphamide therapy in Sweet's syndrome complicating refractory Crohn's disease − Efficacy and mechanism of action

BACKGROUND

Sweet's syndrome is a rare extraintestinal manifestation of Crohn's disease that is usually treated by corticosteroids. Cyclophosphamide therapy has been shown to be effective in steroid-refractory Crohn's disease with extraintestinal manifestations. The mechanism of action remains obscure. Here, we report about a case of steroid-refractory Sweet's syndrome accompanying Crohn's colitis treated by cyclophosphamide.

METHODS

At baseline and two weeks after initiating cyclophosphamide pulse therapy, clinical symptoms were evaluated and apoptosis in mononuclear cells of the colon mucosa was quantified via immunofluorescence TUNEL-labeling. Ongoing clinical follow-up lasts for more than three years.

RESULTS

Cyclophosphamide pulse therapy resulted in complete resolution of luminal activity and extraintestinal manifestations. TUNEL-marked CD4(+), CD8(+) and CD68(+) cells in intestinal biopsies showed a 338% increase as compared to baseline.

CONCLUSIONS

Cyclophosphamide therapy was highly effective in steroid-refractory Crohn's colitis accompanied by Sweet's syndrome for induction of remission. Furthermore, apoptosis of mononuclear cells in the colon mucosa, including CD68(+) macrophages as well as CD4(+) and CD8(+) cells, appears to be a component of the anti-inflammatory effect of cyclophosphamide in Crohn's disease.

Enhanced selection of high affinity DNA-reactive B cells following cyclophosphamide treatment in mice

A major goal for the treatment of patients with systemic lupus erythematosus with cytotoxic therapies is the induction of long-term remission. There is, however, a paucity of information concerning the effects of these therapies on the reconstituting B cell repertoire. Since there is recent evidence suggesting that B cell lymphopenia might attenuate negative selection of autoreactive B cells, we elected to investigate the effects of cyclophosphamide on the selection of the re-emerging B cell repertoire in wild type mice and transgenic mice that express the H chain of an anti-DNA antibody. The reconstituting B cell repertoire in wild type mice contained an increased frequency of DNA-reactive B cells; in heavy chain transgenic mice, the reconstituting repertoire was characterized by an increased frequency of mature, high affinity DNA-reactive B cells and the mice expressed increased levels of serum anti-DNA antibodies. This coincided with a significant increase in serum levels of BAFF. Treatment of transgene-expressing mice with a BAFF blocking agent or with DNase to reduce exposure to autoantigen limited the expansion of high affinity DNA-reactive B cells during B cell reconstitution. These studies suggest that during B cell reconstitution, not only is negative selection of high affinity DNA-reactive B cells impaired by increased BAFF, but also that B cells escaping negative selection are positively selected by autoantigen. There are significant implications for therapy.

Effects of prophylactic administration of bacteriophages to immunosuppressed mice infected with Staphylococcus aureus

BACKGROUND

Bacteriophages can be successfully applied to treat infections caused by antibiotic-resistant bacteria. Until now no attempts have been undertaken to treat infections in immunosuppressed patients with phages. In this work we investigated the prophylactic efficacy of specific bacteriophages in CBA mice treated with cyclophosphamide (CP) and infected with Staphylococcus aureus.

RESULTS

High numbers of bacterial colony-forming units in the organs as well as elevated tumor necrosis factor and interleukin-6 serum concentrations in CP-treated and S. aureus-infected mice were significantly lowered upon application of phages. The phages markedly increased the percentage of circulating neutrophils and immature cells from the myelocytic and lymphocytic lineages in CP-treated, S. aureus-infected mice as well as of myelocytes and immature neutrophils in the bone marrow. In addition, phages stimulated in such mice generation of specific agglutinins against S. aureus.

CONCLUSION

Application of specific phages to immunosuppressed mice prior to infection with S. aureus proved very effective, suggesting a potential benefit of phage therapy in immunocompromised patients experiencing bacterial infections.

Lead exposure induces pycnosis and enucleation of peripheral erythrocytes in the domestic fowl

Lead (Pb) shot were administered orally to young chickens to determine the effects on red blood cells (RBCs). The concentrations of Pb in the blood of young chickens rose rapidly after Pb administration and were maintained at high levels for several days. The number of RBCs with pycnotic nuclei, reticulocytes and enucleated RBCs increased concurrently. Pycnotic nuclei were surrounded by enlarged nucleolemmal cisternae, which sometimes opened to the extracellular space. Gel electrophoresis showed that the presence of pycnotic nuclei was not associated with DNA fragmentation typical of apoptosis. It was concluded that exposure to lead shot changes nuclear morphology in the peripheral blood of domestic fowl.

Antiphospholipid antibody syndrome and autoimmune diseases

The arbitrary division between antiphospholipid antibody syndrome and secondary antiphospholipid antibody syndrome has not proven useful. Antiphospholipid antibodies in the absence of antiphospholipid antibody syndrome often occur as epiphenomena in many autoimmune diseases. They are very common in systemic lupus erythematosus. Antiphospholipid antibody syndrome is a significant comorbidity in lupus but is uncommon in Sjögren's syndrome, rheumatoid arthritis, scleroderma, and systemic vasculitis. Evidence is growing that antiphospholipid antibodies may have a pathogenic role in pulmonary hypertension and accelerated atherosclerosis of autoimmune diseases.

Pathological developments mediated by cyclophosphamide in rats infected with Trypanosoma lewisi

Trypanosoma lewisi is an obligatory, flagellated parasite of the rat. Despite the fact that naturally the rats overcome the disease, a lethal infection can be induced by the administration of an immunosuppressive agent, i.e. cyclophosphamide (Cy). In the Cy treated infected rats (CyI) the severity of the trypanosome infection was demonstrated in the internal organs, in the following order: lungs>liver>heart>spleen>kidney. The parasites were not detected in the brain. The accumulation of the parasites in the lungs led to the development of hemorrhagic inflammatory foci. The rupture of blood vessels was accompanied by lymphocyte infiltrations into the damaged tissues and multiple foci of edema around the blood vessels. In most cases the lungs were dark brown in color due to intra-alveolar hemorrhages. The spleen of the CyI rats showed general deformation of the tissue's architecture, migration of macrophages and cell depletion due to the Cy action. The liver showed inflammatory hemorrhagic foci associated with massive destruction of the parenchyma. In spite of the heavy parasitemia (>50%) developed in the CyI rats the brain remained free of parasites, which might explain the non-virulent character of this parasite compared to the African trypanosomes.

Lactoferrin accelerates reconstitution of the humoral and cellular immune response during chemotherapy-induced immunosuppression and bone marrow transplant in mice

Experimental evidence from previous studies supports the conclusion that orally administered lactoferrin (LF) restores the immune response in mice treated with a sublethal dose of cyclophosphamide (CP). The aim of this study was to elucidate potential benefit of LF in mice undergoing chemotherapy with busulfan (BU) and CP, followed by intravenous (i.v.) injection of bone marrow cells. CBA mice were treated orally with busulfan (4 mg/kg) for 4 consecutive days, followed by two daily doses of CP delivered intraperitoneally (i.p.) at a dose of 100 mg/kg and reconstituted next day with i.v. injection of 10(7) syngeneic bone marrow cells. One group of these mice was given LF in drinking water (0.5% solution). After treatment, mice were immunized with ovalbumin (OVA) to subsequently measure delayed type hypersensitivity responsiveness and with sheep red blood cells to determine humoral immunity by evaluation of splenic antibody-forming cells. As expected, both humoral and cellular immune responses of mice that were treated with these chemotherapeutic agents was markedly impaired. Here we report that this impairment was remarkably attenuated by oral administration of LF. Humoral immunity fell to levels that were 66-88% lower than that of untreated animals. Humoral immunity of LF-treated animals was equivalent to that of untreated mice within 1 month. Cellular immune responses were inhibited by chemotherapy treatment to a lesser degree, reaching levels that were approximately 50% lower than those of untreated animals. Again, LF mitigated this decrease, resulting in responses that were only slightly lower than those observed in untreated animals. Furthermore, when mice were given a lethal dose of BU (4 x 25 mg daily doses, i.p.) followed by a bone marrow transplant, LF caused enhanced lympho-, erythro-, and myelopoiesis in the bone marrow and appearance of transforming splenic lymphoblasts, similar to effects caused by administration of recombinant human granulocyte-macrophage colony-stimulating factor (GM-CSF). In summary, our study suggests that LF may be a useful agent to accelerate restoration of immune responsiveness induced by chemotherapy in bone marrow transplant recipients.

The Use of Systemic Immune Moderators in Dermatology: An Update

In addition to corticosteroids, dermatologists have access to an array of immunomodulatory therapies. Azathioprine, cyclophosphamide, methotrexate, cyclosporine, and mycophenolate mofetil are the systemic immunosuppressive agents most commonly used by dermatologists. In addition, new developments in biotechnology have spurred the development of immunobiologic agents that are able to target the immunologic process of many inflammatory disorders at specific points along the inflammatory cascade. Alefacept, efalizumab, etanercept, and infliximab are the immunobiologic agents that are currently the most well known and most commonly used by dermatologists. This article reviews the pharmacology, mechanism of action, side effects, and clinical applications of these therapies.

Risk of ovarian failure and pregnancy outcome in patients with lupus nephritis treated with intravenous cyclophosphamide pulse therapy

This study was designed to investigate the risk of ovarian failure and the pregnancy outcomes in women treated with intravenous cyclophosphamide (IVCYC) pulse therapy for lupus nephritis. Sixty-seven women with proliferative lupus nephritis were studied. The clinical and laboratory data, SLEDAI and damage indices at IVCYC initiation, doses and numbers of IVCYC pulses, pregnancy and fetal outcomes were evaluated. During a follow-up of 74.4+/-20.6 months, amenorrhea occurred in 25 (37.3%) and was sustained permanently in 10 patients (14.9%). Thirteen women became pregnant with a total of 19 pregnancies. Seventeen pregnancies ended without complications and all babies were born healthy without any congenital anomalies or perinatal illnesses. Two pregnancies were terminated by induced abortion but no congenital anomaly was noted in these cases. Logistic regression analysis showed that old age, high damage index at the initiation of IVCYC pulse therapy and high cumulative dosage of IVCYC were the independent risk factors of ovarian failure, and that the presence of amenorrhea, regardless of its duration, was the risk factor of pregnancy failure. Pregnancy was possible with a favorable outcome after the withdrawal of IVCYC pulse therapy, unless amenorrhea develops.

Orally administered lactoferrin restores humoral immune response in immunocompromised mice

Cyclophosphamide (CP) is an anti-tumor drug commonly used in the chemotherapy of human cancer and autoimmune diseases. In our previous studies, we have demonstrated that lactoferrin (LF), given orally to CP-immunosuppressed mice, could reconstitute a T cell mediated immune response by the renewal of the T cell population. The aim of this present study was to evaluate the effects of LF on humoral responses in mice treated with cyclophosphamide. We demonstrate that a single, sublethal dose of cyclophosphamide (400 mg/kg body weight) profoundly inhibited the humoral immune response of CBA mice to sheep red blood cells (SRBC), as measured by the number of antibody forming cells (AFC) in the spleen after 5 weeks following CP treatment. Administration of 0.5% bovine LF in drinking water for 5 weeks partially reconstituted the AFC number (30-40% of the control values, but 7-10x more than in CP-treated controls). Determination of T and B cell levels in the spleens by flow cytometry revealed that the content of CD3+ and CD4+ as well as Ig+ splenocytes was elevated in the immunocompromised mice treated with LF. In addition, the number of peritoneal macrophages was partially restored following LF treatment. Evaluation of the proliferative response to concanavalin A (ConA) and pokeweed mitogen (PWM) demonstrated that the diminished reactivity of splenocytes from CP-treated mice was significantly enhanced by LF. In summary, we conclude that the prolonged, oral treatment of immunocompromised mice with LF led to partial reconstitution of the humoral response, associated with elevation of T and B cell and macrophage content and the proliferative response of splenocytes to mitogens.

Differential induction of apoptosis and MAP kinase signaling by mitochondrial toxicants in drug-sensitive compared to drug-resistant B-lineage lymphoid cell lines

A panel of human B-lineage lymphoma cell lines differing in cancer drug-resistance status and Bcl-2/Bax expression were used to study the contribution of mitochondrial-based perturbations and regulation in differential induction of apoptosis. Mitochondrial dysfunction was induced in cells by the uncoupler carbonyl cyanide m-chlorophenylhydrazone (mClCCP) and the respiratory chain inhibitor antimycin A. Cells were then assayed for early changes in MAP kinase signaling and subsequent induction of apoptosis. The cancer drug-resistant cell lines EW36 and CA46, overexpressing Bcl-2 and deficient in Bax, respectively, were both resistant to mitochondrial toxicant-induced cleavage of poly(ADP-ribose) polymerase (PARP) and morphologically detectable apoptotic cell death. In contrast, cancer drug-sensitive ST486 cell line, with low Bcl-2 expression, was sensitive to PARP cleavage and apoptosis engagement. Interestingly, mClCCP induced twofold more apoptosis than antimycin A in the ST486 cells. Exposure to the mitochondrial toxicants resulted in the early and preferential activation of the ERK and p38 MAP kinase pathways in only the drug-sensitive ST486 cell line, with mClCCP more potent than antimycin A. Specific inhibition of the p38 pathway augmented baseline and mClCCP-induced apoptosis. These results show that multi-drug-resistant and -sensitive B-lineage cells are also resistant and sensitive to compounds inducing mitochondrial dysfunction. The differential sensitivity to mitochondrial toxicant effects involved regulation by MAP kinases, since ERK and p38 were found to be preferentially activated only in the drug-sensitive B-lineage cells. Modulation of the p38 signaling pathway altered the sensitivity of cells to mitochondrial stress and may play a more general role in regulating the sensitivity of B-lineage cells to drugs and environmental toxicants.

Preclinical protocol for in vivo selection of hematopoietic stem cells corrected by gene therapy in Fanconi anemia group C

Fanconi anemia (FA) is an autosomal recessive disorder characterized by birth defects, increased incidence of malignancy, progressive bone marrow failure, and cellular hypersensitivity to DNA cross-linking agents. Bone marrow transplantation is therapeutic and therefore FA is a candidate disease for hematopoietic gene therapy. We have previously used mitomycin C (MMC) to achieve in vivo selection of wild-type hematopoietic stem cells (HSC) transplanted into FANCC knockout mice. However, clinical application of MMC in human FA gene therapy is unlikely because of its unknown toxicity profile in human FA patients. In contrast, cyclophosphamide (CPA) and gamma-irradiation (IR) are already in use with human FA patients and we therefore tested these regimens for their ability to achieve selection of genetically corrected HSCs in vivo. We found that nonmyeloablative doses of CPA or IR or combinations of CPA + IR were highly efficient at achieving in vivo selection of transplanted wild-type HSC. Furthermore, this nontoxic regimen also selected FANCC-mutant HSC corrected by ex vivo retroviral gene therapy. We suggest those nontoxic doses of CPA and/or IR could also be used to enhance gene therapy in human FA patients.

Relatively low-dose cyclophosphamide is likely to induce apoptotic cell death in rat thymus through Fas/Fas ligand pathway

Cyclophosphamide (CPA) is widely used as an efficiently antineoplastic drug, but also causes immunosuppression as its adverse-side effect. To understand the effect of low- or relative low-dose CPA on the immune system, apoptotic cell death in rat thymus, either exposed to different doses of CPA (0, 2, 7, 20 and 70 mg/kg) for 12 h or exposed to 70 mg/kg for different times (4-48 h), was investigated by DNA fragmentation (DNA ladder) detection and in situ morphological examination using hematoxylin and eosin (H and E) staining. Immunohistochemical staining for Fas protein expression in the thymus of rats exposed to CPA was performed. Results showed that exposure of rats to CPA 0-70 mg/kg for 12 h did not cause significant decrease in the ratio of thymus weight to body weight. However, the ratio of thymus weight to body weight was decreased significantly at 48 h after exposure to 70 mg/kg CPA. Exposure to 20 and 70 mg/kg CPA for 12 h caused a visible DNA ladder in gel electrophoresis. DNA ladder formation was increased progressively in the groups from 8 h to optimal magnitude at 12-24 h and then disappeared at 48 h after 70 mg/kg CPA. This pattern was confirmed by a quantitative evaluation of the apoptotic cells using H and E staining. Expression of Fas protein was enhanced in the thymus of rats exposed to 70 mg/kg CPA for 4-8 h as compared to control rats. These results are different from previous studies on high dose CPA and the induction of the apoptotic cell death in thymus by low or relative low doses of CPA might be a result of Fas/Fas-ligand interactions.

Expression of cell death regulatory genes and limited apoptosis induction in avian blastodermal cells

Apoptosis is a well-established cellular mechanism for selective cell deletion during development. However, little is known about the expression of an apoptotic pathway and its role in determining the relative sensitivity of the early, pre-gastrula, avian embryo to stress-induced cell death. We examined the sensitivity of avian blastodermal cells to engage in apoptosis upon exposure to etoposide, a topoisomerase II-inhibitor that rapidly and efficiently induces apoptosis in many cell types. We found that while the blastodermal cells are capable of engaging in apoptosis, they are highly resistant to such induction with respect to both concentration of drug required and length of exposure, even when compared to a tumor cell line with a known multi-drug resistant phenotype. Additionally, we assessed the expression of several candidate regulatory genes in blastodiscs from infertile eggs (i.e., maternal RNA transcripts), blastodermal cells immediately following oviposition, and various stages of early development up to gastrulation. This analysis revealed that several genes whose products have anti-apoptotic activity, including bcl-2, bcl-xL, hsp70, grp78 and the glutathione S-transferases, are expressed as early as the stage 1 embryo in the newly oviposited egg. These transcripts are also found in the infertile blastodisc, suggesting a role for maternally derived transcripts in the protection of the oocyte and zygote. Significantly, constitutive levels of hsp70 mRNA exceeded those of the other anti-apoptotic genes in the blastodermal cells. These results contribute to an emerging picture of stress resistance at the earliest stages of avian embryo development which involves multiple anti-apoptotic genes that act at different regulatory points in the apoptotic cascade.

Immunosuppressive agents in dermatology. An update

Azathioprine, cyclophosphamide, methotrexate, and cyclosporine are the immunosuppressive agents most commonly used by dermatologists. Azathioprine has a relatively good safety profile and is therefore often preferred for the treatment of chronic eczematous dermatitides and bullous disorders. Awareness of the role of genetic polymorphisms in its metabolism can increase the efficacy and safety of this drug. Cyclophosphamide is an antimetabolite that has a more rapid onset of immunosuppressive effect than azathioprine, but has significant short-term and long-term toxicity. It is of use in fulminant, life-threatening cutaneous disease. Methotrexate is an antimetabolite that has significant anti-inflammatory activity. Despite its hepatotoxicity, its role in inflammatory dermatoses is broadening. Likewise, the role of cyclosporine is being expanded. This drug has potent T-cell inhibitory effects secondary to interference with intracellular signal transduction. Given the evidence for cumulative renal toxicity, it currently has a role in the short-term treatment of refractory psoriasis and atopic dermatitis, as well as in select inflammatory dermatoses. Familiarity with disease-specific clinical efficacy, side-effect profile, and dosage allows the successful and judicious use of these drugs in dermatologic disorders.

Contribution of gene-specific lesions, DNA-replication-associated damage, and subsequent transcriptional inhibition in topoisomerase inhibitor-mediated apoptosis in lymphoma cells

Lymphoid lineage tumor cells differ widely in their relative sensitivity or resistance to the induction of apoptosis by a variety of chemotherapeutic drugs. We used a model system of virally transformed B- and T-lymphoma cell lines to show that avian T-lymphoma cells are highly resistant, whereas B-lymphoma cells are highly sensitive, to the induction of apoptosis by a wide spectrum of chemotherapeutic drugs that induce different types of lesions in DNA. Among the various drugs examined, the topoisomerase inhibitors, camptothecin, actinomycin D, and etoposide, were the most potent inducers of apoptosis. Examination of the relative contribution of DNA replication and transcriptional inhibition to the differential induction of apoptosis by the topoisomerase inhibitors revealed that the signals initiating the apoptotic response vary, even among compounds with similar cellular targets. Specifically, DNA replication plays a major role in the induction of camptothecin-induced apoptosis, and a lesser role in the induction of apoptosis by etoposide. In contrast, DNA replication is not involved in the induction of apoptosis by actinomycin D. Transcriptional inhibition may provide the major cellular signal for apoptosis induction by this compound. In addition, we determined that the extent of topoisomerase I-cleavable complex inhibition is similar even in genes that are transcribed at different levels and by different RNA polymerases. An overexpressed c-myc gene is no more vulnerable to topoisomerase inhibition than its normally expressed counterpart. In contrast, even under conditions yielding similar amounts of topoisomerase inhibition, rRNA genes are more sensitive to transcriptional inhibition than are the c-myc genes.

Involvement of gene-specific DNA damage and apoptosis in the differential toxicity of mitomycin C analogs towards B-lineage versus T-lineage lymphoma cells

Avian and mammalian B- and T-lineage lymphocytes display differential sensitivity to a variety of genotoxic agents. Specifically, T-lineage cells show a high degree of resistance to the toxic effects of exposure to chemotherapeutic drugs, whereas B-lineage cells show a high degree of sensitivity. We used a model system consisting of virally transformed B- and T-lymphoma cell lines to further define the cellular and molecular mechanisms responsible for the differential toxicity of two chemotherapeutic drugs that induce DNA-interstrand cross-links to different degrees, mitomycin C (MMC) and its aminodisulfide analog, BMY 25067. Quantification of the number of cross-links introduced in the transcriptionally active ribosomal RNA gene cluster revealed that similar levels of DNA damage were induced in B- and T-lymphoma cell lines. However, B-lymphoma cells were highly sensitive to induction of apoptosis and inhibition of growth compared with the more resistant T-lymphoma cells for both compounds. BMY 25067 induced approximately 2-fold more cross-links in rDNA than did MMC, along with a concurrent enhanced induction of apoptosis in both B- and T-lymphoma cell lines. An analysis of the persistence of DNA lesions over multiple cell cycles revealed that neither B- nor T-lymphoma cells repaired DNA cross-links to a significant extent. These data suggest that differences in the extent or persistence of DNA-interstrand cross-links are not responsible for the differential toxicity of MMC and its analog towards B- versus T-lineage cells. Rather, differential drug toxicity involves early and extensive entry into apoptosis in B-lymphoma cells contrasted to the delayed and minimal apoptotic induction in T-lymphoma cells.