Cost-Effectiveness of Unrelated Umbilical Cord Blood vs. HLA Haploidentical Related Bone Marrow Transplant: Evidence from BMT CTN 1101

BACKGROUND

BMT CTN 1101 was a Phase III randomized controlled trial comparing reduced intensity conditioning followed by double unrelated umbilical cord blood (UCB) versus HLA-haploidentical related donor bone marrow (haplo-BM) transplantation for patients with high-risk hematologic malignancies.

OBJECTIVE

The objective of this study is to report the results of a parallel cost-effectiveness analysis.

STUDY DESIGN

Three hundred sixty-eight patients were randomized to unrelated UCB (n=186) or haplo-BM (n=182) transplant. We estimated healthcare utilization and costs using propensity score-matched BMT patients from the OptumLabs^Ⓡ Data Warehouse for trial participants <65 years and Medicare claims for participants ≥65 years. Weibull models were used to estimate 20-year survival. EQ-5D surveys by trial participants were used estimate Quality-Adjusted Life Years (QALYs).

RESULTS

At 5-year follow-up, survival was 42% for haplo-BM versus 36% for UCB (P=.06). Over a 20-year time horizon, haplo-BM is expected to be more effective (+0.63 QALY) and more costly +$118,953) for persons under 65. For those over 65, haplo-BM is expected to be more effective and less costly. In one-way uncertainty analyses, for persons <65, the cost per QALY result was most sensitive to life years and health state utilities. For persons ≥65, life years were more influential than costs and health state utilities.

CONCLUSION

Compared to UCB, haplo-BM was moderately cost-effective for patients aged <65 years, and less costly and more effective for persons ≥65 years. Haplo-BM is a fair value choice for commercially insured patients with high-risk leukemia and lymphoma who require HCT. For Medicare enrollees, haplo-BM is a preferred choice when considering costs and outcomes.

Successful transplantation of kidney allografts in sensitized rats after syngeneic hematopoietic stem cell transplantation and fludarabine

Current methods to remove donor-specific HLA antibody (DSA) from sensitized patients remain imperfect. We tested novel approaches to desensitization using an animal model of allogeneic sensitization with skin grafts from dark agouti (DA) to Lewis rats. At the peak IgG alloantibody response we transplanted DA kidneys into nephrectomized Lewis recipients (n = 6) and all died within 10 days from antibody-mediated rejection (AMR). Allogeneic hematopoietic stem cell transplants (HSCT) from DA donors failed to engraft after lethal or sub-lethal irradiation. Sensitized rats given lethal irradiation plus syngeneic green fluorescent protein (GFP) + HSCT had repopulation of blood, spleen, thymus and lymph nodes by GFP+ cells. At 2 months after HSCT, serum DSA levels were reduced 60-70% and DSA (IgG) production in cultured splenocytes was also significantly decreased. However, there was only a modest improvement in graft survival from an average of 6.5 to 13.9 (n = 9) days. Adding seven daily doses of fludarabine to the preconditioning regimen resulted in long-term survival (>90 days) in 7 out of 10 rat kidney allografts. We conclude that syngeneic HSCT performed after preconditioning with irradiation and fludarabine can reduce DSA, prevent DSA rebound and AMR, enabling successful transplantation in animals with strong antibody reactivity to the donor MHC.

Neither insects nor wind: ambophily in dioecious Chamaedorea palms (Arecaceae)

Pollination of Neotropical dioecious trees is commonly related to generalist insects. Similar data for non-tree species with separated genders are inconclusive. Recent studies on pollination of dioecious Chamaedorea palms (Arecaceae) suggest that species are either insect- or wind-pollinated. However, the wide variety of inflorescence and floral attributes within the genus suggests mixed pollination mode involving entomophily and anemophily. To evaluate this hypothesis, we studied the pollination of Chamaedorea costaricana, C. macrospadix, C. pinnatifrons and C. tepejilote in two montane forests in Costa Rica. A complementary morphological analysis of floral traits was carried out to distinguish species groups within the genus according to their most probable pollination mechanism. We conducted pollinator exclusion experiments, field observations on visitors to pistillate and staminate inflorescences, and trapped airborne pollen. A cluster analysis using 18 floral traits selected for their association with wind and insect pollination syndromes was carried out using 52 Chamaedorea species. Exclusion experiments showed that both wind and insects, mostly thrips (Thysanoptera), pollinated the studied species. Thrips used staminate inflorescences as brood sites and pollinated pistillate flowers by deception. Insects caught on pistillate inflorescences transported pollen, while traps proved that pollen is wind-borne. Our empirical findings clearly suggest that pollination of dioecious Chamaedorea palms is likely to involve both insects and wind. A cluster analysis showed that the majority of studied species have a combination of floral traits that allow for both pollination modes. Our pollination experiments and morphological analysis both suggest that while some species may be completely entomophilous or anemophilous, ambophily might be a common condition within Chamaedorea. Our results propose a higher diversity of pollination mechanisms of Neotropical dioecious species than previously suggested.

Immunologic recovery following autologous stem-cell transplantation with pre- and posttransplantation rituximab for low-grade or mantle cell lymphoma

BACKGROUND

Rituximab may improve transplant outcomes but may delay immunologic recovery.

PATIENTS AND METHODS

Seventy-seven patients with low-grade or mantle cell lymphoma received autologous stem-cell transplantation (ASCT) on a phase II study. Rituximab 375 mg/m(2) was administered 3 days before mobilization-dose cyclophosphamide, then weekly for four doses after count recovery from ASCT. Immune reconstitution was assessed.

RESULTS

Sixty percent of transplants occurred in first remission. Actuarial event-free survival (EFS) and overall survival (OS) were 60% and 73%, respectively, at 5 years, with 7.2-year median follow-up for OS in surviving patients. Median EFS was 8.3 years. Older age and transformed lymphomas were independently associated with inferior EFS, whereas day 60 lymphocyte counts did not predict EFS or late infections. Early and late transplant-related mortality was 1% and 8%, with secondary leukemia in two patients. B-cell counts recovered by 1-2 years; however, the median IgG level remained low at 2 years. Late-onset idiopathic neutropenia, generally inconsequential, was noted in 43%.

CONCLUSION

ASCT with rituximab can produce durable remissions on follow-up out to 10 years. Major infections do not appear to be significantly increased or to be predicted by immune monitoring.

Salvage transplantation for allograft failure using fludarabine and alemtuzumab as conditioning regimen

Graft failure after allogeneic blood or marrow transplantation, although generally uncommon, can be a devastating complication. This report includes the outcome of nine patients who received a salvage transplant for failure to engraft after one (n=8) or 2 (n=1) prior transplants. Eight patients received allografts from the original donor. All received fludarabine 30 mg/m(2) i.v. and alemtuzumab 20 mg i.v. daily from days -6 to -2. Daily CYA was begun on day -2, and the allograft was infused on day 0. The therapy was well tolerated with low toxicity, and all nine patients engrafted, recovering neutrophils at a median of 12 days after transplant. Four patients died: two of relapse, one of a fungal infection in the setting of GVHD and one of multiple sclerosis. The combination of fludarabine and alemtuzumab is an effective and well-tolerated salvage conditioning regimen for patients who experience graft failure after blood or marrow transplants.

Reduced intensity HLA-haploidentical BMT with post transplantation cyclophosphamide in nonmalignant hematologic diseases

Allogeneic blood or marrow transplantation (BMT) is potentially curative for a variety of life-threatening nonmalignant hematologic diseases such as paroxysmal nocturnal hemoglobinuria (PNH) and hemoglobinopathies. The application of BMT to treat these disorders is limited by the lack of suitable donors and often end-organ damage from the underlying disease. We treated three patients with thrombotic PNH, one of whom also had sickle cell disease, with a nonmyeloablative, HLA-haploidentical BMT with post-transplant CY. Rapid engraftment without GVHD occurred in two of the patients, including the patient with sickle cell disease. Both patients are disease free with full donor chimerism and require no immunosuppressive therapy, with follow-up of 1 and 4 years, respectively. Nonmyeloablative, HLA-haploidentical BMT with post-transplant CY is a promising approach for patients with life-threatening nonmalignant hematologic disease who lack an HLA-matched sibling donor.

Quantitative imaging and sigmoidoscopy to assess distribution of rectal microbicide surrogates

Understanding the distribution of microbicide and human immunodeficiency virus (HIV) within the gastrointestinal tract is critical to development of rectal HIV microbicides. A hydroxyethylcellulose-based microbicide surrogate or viscosity-matched semen surrogate, labeled with gadolinium-DTPA (diethylene triamine pentaacetic acid) and 99mTechnetium-sulfur colloid, was administered to three subjects under varying experimental conditions to evaluate effects of enema, coital simulation, and microbicide or semen simulant over 5 h duration. Quantitative assessment used single photon emission computed tomography (SPECT)/computed tomography (CT) and magnetic resonance imaging (MRI) imaging, and sigmoidoscopic sampling. Over 4 h, radiolabel migrated cephalad in all studies by a median (interquartile range) of 50% (29-102%; P<0.001), as far as the splenic flexure (approximately 60 cm) in 12% of studies. There was a correlation in concentration profile between endoscopic sampling and SPECT assessments. HIV-sized particles migrate retrograde, 60 cm in some studies, 4 h after simulated ejaculation in our model. SPECT/CT, MRI, and endoscopy can be used quantitatively to facilitate rational development of microbicides for rectal use.

Balancing justice and autonomy in clinical research with healthy volunteers

In clinical research, ethics review generally first examines whether study risks are reasonable in light of benefits provided. Through informed consent, then, prospective subjects consider whether the risk/benefit balance and procedures are reasonable for them. Unique ethics issues emerge in clinical research with healthy volunteers. Certain types of studies only recruit healthy volunteers as participants. Phase 1 studies, for example, including first time in human studies of investigational drugs and vaccines, generally are conducted in healthy volunteers. Although such research carries inherent and often unknown risks, healthy subjects provide the most efficient target population in which to conduct such research, as these volunteers generally are free of concurrent diseases or medications that could confound interpretation of toxicity. Other studies enrolling healthy volunteers often are simply looking for the most scientifically sound population for the study of normal human physiology.

Nonmyeloablative bone marrow transplantation from partially HLA-mismatched related donors using posttransplantation cyclophosphamide

Cyclophosphamide (Cy) is a potent immunosuppressive agent that is selectively toxic to lymphocytes proliferating in response to recent antigen stimulation. In animal models, both graft rejection and GVHD after histoincompatible BMT can be inhibited by the posttransplantation administration of high-dose Cy. Therefore, a phase I clinical trial was undertaken to determine the minimal conditioning, including posttransplantation Cy, that permits the stable engraftment of partially HLA-mismatched marrow (up to 3 HLA antigens) from first-degree relatives. Thirteen patients (median age, 53 years) with high-risk hematologic malignancies received conditioning with fludarabine, 30 mg/m2 per day from days -6 to -2, and TBI, 2 Gy on day -1. All patients received Cy, 50 mg/kg on day 3, mycophenolate mofetil from day 4 to day 35, and tacrolimus from day 4 to day > or = 50. Three patients in cohort 1 received no additional conditioning, and 2 experienced graft rejection. Ten patients in cohort 2 received identical conditioning with the addition of Cy 14.5 mg/kg on days -6 and -5. Sustained donor cell engraftment occurred in 8 of these patients, with a median time to absolute neutrophil count > 500/microL of 15 days (range, 13-16 days) and to unsupported platelet count > 20,000/microL of 14 days (range, 0-26 days). All patients with engraftment achieved > or = 95% donor chimerism within 60 days of transplantation. Two patients with myelodysplastic syndrome rejected their grafts but experienced autologous neutrophil recovery at 24 and 44 days. Histologic acute GVHD developed in 6 patients (grade II in 3 patients, grade III in 3 patients) at a median of 99 days (range, 38-143 days) after transplantation and was fatal in 1 patient. At a median follow-up of 191 days (range, 124-423 days), 6 of 10 patients in cohort 2 were alive, and 5 were in complete remission of their disease, including both patients with graft rejection. These data demonstrate that partially HLA-mismatched bone marrow can engraft rapidly and stably after nonmyeloablative conditioning that includes posttransplantation Cy. Clinically significant antitumor responses occur, even among patients who reject their donor grafts.

Durable engraftment of major histocompatibility complex-incompatible cells after nonmyeloablative conditioning with fludarabine, low-dose total body irradiation, and posttransplantation cyclophosphamide

Treatment of leukemia by myeloablative conditioning and transplantation of major histocompatibility complex (MHC)-mismatched stem cells is generally avoided because of the high risk of graft rejection or lethal graft-versus-host disease (GVHD). This study shows that MHC-incompatible cells can engraft stably after nonmyeloablative conditioning with immunosuppressive chemotherapy and low-dose total body irradiation (TBI). Long-term mixed hematopoietic chimerism, clonal deletion of donor-reactive T cells, and bidirectional cytotoxic T-cell tolerance were achieved by transplanting MHC-mismatched marrow cells into recipients conditioned with pretransplantation fludarabine or cyclophosphamide (Cy), 50 to 200 cGy TBI on day -1, and Cy 200 mg/kg intraperitoneally on day 3. In this model, long-term donor chimerism was proportional to the dose of TBI or donor marrow cells. Pretransplantation fludarabine and posttransplantation Cy were both required for alloengraftment, but the drugs had additional effects. For example, fludarabine sensitized host stem cells to the toxicity of TBI, because animals conditioned with both agents had higher chimerism than animals conditioned with TBI alone (P <.05). Also, posttransplantation Cy attenuated lethal and nonlethal GVH reactions, because F(1) recipients of host-reactive, parental spleen cells survived longer (P <.05) and had lower donor cell chimerism (P <.01) if they received posttransplantation Cy than if they did not. Finally, delayed infusions of donor lymphocytes into mixed chimeras prolonged survival after leukemia challenge (P <.0001) without causing lethal GVHD. These results indicate that stable engraftment of MHC-incompatible cells can be induced after fludarabine-based, nonmyeloablative conditioning and that it serves as a platform for adoptive immunotherapy with donor lymphocyte infusions.

Pollen load size, reproductive success, and progeny kinship of naturally pollinated flowers of the tropical dry forest tree Pachira quinata (Bombacaceae)

Several studies have demonstrated, using controlled pollinations, that the number and identity of pollen grains deposited onto a flower's stigma affect the reproductive success of plants. However, few studies have shown this relationship under conditions of natural pollination. Using the tropical dry forest tree Pachira quinata, we evaluated the relationship between the number of microgametophytes per pistil and the number of sires with respect to the production of fruits and seeds in a natural population of Pachira quinata. Our study demonstrates that fruit and seed production are directly related to the number of microgametophytes per pistil in natural populations of P. quinata. Only 6% of the marked flowers developed into mature fruits and 10% of the marked flowers initiated fruits but later aborted them. A mean of 23 pollen grains were required to produce a seed. Flowers with >400 pollen grains on the stigma always developed into mature fruits, whereas flowers that received <200 grains never matured fruits. Half of the pollen grains transferred to a flower stigma germinated and developed pollen tubes to the base of the style. The number of pollen grains on a stigma explained 34% of the variation in seed number per fruit, and the number of seeds produced per fruit is positively correlated with the size of the seeds. The population of P. quinata studied is predominantly outcrossing, and seeds within fruits are sired by one or a few donors. The total seed crop within trees was sired by three to five donors. Our study examined the implications of the variation in size of microgametophyte loads per pistil with respect to the breeding system and the paternity of progeny under natural conditions. The competitive ability of pollen and pollen tube attrition are important factors regulating fruit production in P. quinata.

Effects of mixed hematopoietic chimerism in a mouse model of bone marrow transplantation for sickle cell anemia

Sickle cell anemia (SCA) is an inherited disorder of beta-globin, resulting in red blood cell rigidity, anemia, painful crises, organ infarctions, and reduced life expectancy. Allogeneic blood or marrow transplantation (BMT) can cure SCA but is associated with an 8% to 10% mortality rate, primarily from complications of marrow-ablative conditioning. Transplantation of allogeneic marrow after less intensive conditioning reduces toxicity but may result in stable mixed hematopoietic chimerism. The few SCA patients who inadvertently developed mixed chimerism after BMT remain symptom free, suggesting that mixed chimerism can reduce disease-related morbidity. However, because the effects of various levels of mixed chimerism on organ pathology have not been characterized, this study examined the histologic effects of an increasing percentage of normal donor hematopoiesis in a mouse model of BMT for SCA. In lethally irradiated normal mice that were reconstituted with varying ratios of T-cell-depleted marrow from normal and transgenic "sickle cell" mice, normal myeloid chimerism in excess of 25% was associated with more than 90% normal hemoglobin (Hb). However, 70% normal myeloid chimerism was required to reverse the anemia. Organ pathology, including liver infarction, was present in mice with sickle Hb (HbS) levels as low as 16.8% (19.6% normal myeloid chimerism). Histologic abnormalities increased in severity up to 80% HbS, but were less severe in mice with more than 80% HbS than in those with 40% to 80% HbS. Therefore, stable mixed chimerism resulting from nonmyeloablative BMT may reduce the morbidity from SCA, but prevention of all disease complications may require minimizing the fraction of circulating sickle red cells. (Blood. 2001;97:3960-3965)

Regulation of death receptor expression and TRAIL/Apo2L-induced apoptosis by NF-kappaB

TRAIL (tumour-necrosis factor-related apoptosis ligand or Apo2L) triggers apoptosis through engagement of the death receptors TRAIL-R1 (also known as DR4) and TRAIL-R2 (DR5). Here we show that the c-Rel subunit of the transcription factor NF-kappaB induces expression of TRAIL-R1 and TRAIL-R2; conversely, a transdominant mutant of the inhibitory protein IkappaBalpha or a transactivation-deficient mutant of c-Rel reduces expression of either death receptor. Whereas NF-kappaB promotes death receptor expression, cytokine-mediated activation of the RelA subunit of NF-kappaB also increases expression of the apoptosis inhibitor, Bcl-xL, and protects cells from TRAIL. Inhibition of NF-kappaB by blocking activation of the IkappaB kinase complex reduces Bcl-x L expression and sensitizes tumour cells to TRAIL-induced apoptosis. The ability to induce death receptors or Bcl-xL may explain the dual roles of NF-kappaB as a mediator or inhibitor of cell death during immune and stress responses.

Pharmacokinetics and safety of AMD-3100, a novel antagonist of the CXCR-4 chemokine receptor, in human volunteers

AMD-3100, a bicyclam, is a novel agent that uniquely inhibits the entry of human immunodeficiency virus type 1 (HIV-1) into CD4(+) T cells via selective blockade of the chemokine CXCR-4 receptor. Twelve healthy volunteers were given AMD-3100 as a single 15-min intravenous infusion at 10, 20, 40, or 80 microg/kg. Five subjects also received a single subcutaneous injection of AMD-3100 (40 or 80 microg/kg). Three subjects received two escalating oral doses each (80 and 160 microg/kg). All subjects tolerated their dose(s) well without any grade 2 toxicity or dose adjustment. Six subjects experienced mild, transient symptoms, primarily gastrointestinal in nature and not dose related. All subjects experienced a dose-related elevation of the white blood cell count, from 1.5 to 3.1 times the baseline, which returned to the baseline 24 h after dosing. AMD-3100 demonstrated dose proportionality for the maximum drug concentration in serum (C(max)) and the area under the concentration-time curve from 0 h to infinity (AUC(0-infinity)) over the entire dose range. At the highest intravenous dose (80 microg/kg), the median C(max) was 515 (range, 470 to 521) ng/ml and the AUC(0-infinity) was 1,044 (range, 980 to 1,403) ng-h/ml. The median systemic absorption after subcutaneous dosing was 87% (range, 67 to 106%). No drug was detectable in the blood following oral dosing. Using a two-compartment model, the median pharmacokinetic parameter estimates (ranges) were as follows: volume of distribution, 0.34 (0. 27 to 0.36) liter/kg; clearance, 1.30 (0.97 to 1.34) liters/h; elimination half-life, 3.6 (3.5 to 4.9) h. After a single, well-tolerated intravenous dose of AMD-3100, concentrations were sustained for 12 h above the in vitro antiretroviral 90% inhibitory concentrations and for 8 h above antiviral concentrations identified in the SCID-hu Thy/Liv mouse model of HIV infection.

Flavopiridol induces apoptosis in chronic lymphocytic leukemia cells via activation of caspase-3 without evidence of bcl-2 modulation or dependence on functional p53

Flavopiridol has been reported to induce apoptosis in lymphoid cell lines via downregulation of bcl-2. The in vitro activity of flavopiridol against human chronic lymphocytic leukemia (CLL) cells and potential mechanisms of action for inducing cytotoxicity were studied. The in vitro viability of mononuclear cells from CLL patients (n = 11) was reduced by 50% at 4 hours, 24 hours, and 4 days at a flavopiridol concentration of 1.15 micromol/L (95% confidence interval [CI] +/-0.31), 0.18 micromol/L (95% CI +/-0.04), and 0.16 micromol/L (95% CI +/-0.04), respectively. Loss of viability in human CLL cells correlated with early induction of apoptosis. Exposure of CLL cells to 0.18 micromol/L of flavopiridol resulted in both decreased expression of p53 protein and cleavage of the caspase-3 zymogen 32-kD protein with the appearance of its 20-kD subunit. Contrasting observations of others in tumor cell lines, flavopiridol cytotoxicity in CLL cells did not correlate with changes in bcl-2 protein expression alterations. We evaluated flavopiridol's dependence on intact p53 by exposing splenocytes from wild-type (p53(+/+)) and p53 null (p53(-/-)) mice that demonstrated no preferential cytotoxicity as compared with a marked differential with F-ara-a and radiation. Incubation of CLL cells with antiapoptotic cytokine interleukin-4 (IL-4) did not alter the LC50 of flavopiridol, as compared with a marked elevation noted with F-ara-a in the majority of patients tested. These data demonstrate that flavopiridol has significant in vitro activity against human CLL cells through activation of caspase-3, which appears to occur independently of bcl-2 modulation, the presence of IL-4, or p53 status. Such findings strongly support the early introduction of flavopiridol into clinical trials for patients with B-CLL.

p53-mediated repression of nuclear factor-kappaB RelA via the transcriptional integrator p300

The p53 tumor suppressor gene plays an instrumental role in transcriptional regulation of target genes involved in cellular stress responses. p53-dependent transactivation and transrepression require its interaction with p300/CBP, a coactivator that also interacts with the RelA subunit of nuclear factor-kappaB. We find that p53 inhibits RelA-dependent transactivation without altering RelA expression or inducible kappaB-DNA binding. p53-mediated repression of RelA is relieved by p300 overexpression and the increased RelA activity conferred by p53-deficiency is counteracted by either transactivation domain-deficient p300 fragments that bind RelA or a transdominant mutant of IkappaB alpha. Our results suggest that p53 can regulate diverse kappaB-dependent cellular responses.

Chemotherapy does not nullify the ability of donor lymphocyte infusions to mediate graft-versus-host reactions

Two patients with multiple myeloma in relapse after allogeneic BMT received donor lymphocyte infusions (DLI) but later required chemotherapy for treatment of myeloma-related complications. In both patients, recovery from chemotherapy-induced aplasia was accompanied by manifestations of graft-versus-host reactions. The first patient developed grade II acute GVHD and a complete remission which has lasted >22 months. The second patient developed grade III acute GVHD but died with co-existing GVHD and extensive extramedullary myeloma. These results demonstrate that chemotherapy does not nullify the ability of donor lymphocytes to mediate graft-versus-host reactions.

CD95 (Fas)-induced caspase-mediated proteolysis of NF-kappaB

Activation of the nuclear factor (NF)-kappaB transcription factor is instrumental for the immune response and the survival of peripheral activated T cells. We demonstrate that ligation of CD95 (Fas/APO1), a potent apoptotic stimulus in lymphocytes, results in repression of NF-kappaB activity in Jurkat T cells by inducing the proteolytic cleavage of NF-kappaB p65 (Rel A) and p50. Inhibition of caspase-3-related proteases by a specific acetylated aldehyde (Ac-DEVD-CHO) prevented CD95-induced cleavage of p65 (RelA) or p50 and restored the inducibility of NF-kappaB in cells treated with an antibody against CD95. The addition of recombinant caspase-3 also resulted in proteolytic cleavage of RelA p65 and p50 in vitro. TNF-alpha treatment, unlike CD95 ligation, did not result in the death of Jurkat cells but did so in the presence of I kappaB alphaM, a transdominant inhibitor of NF-kappaB. These results suggest that intact, functional NF-kappaB maintains the survival of activated T cells, and that CD95-induced cleavage of NF-kappaB subunits sensitizes T cells to apoptosis and, hence, facilitates the decay of an immune response.

p53-dependent DNA damage-induced apoptosis requires Fas/APO-1-independent activation of CPP32beta

In many cell types, the p53 tumor suppressor protein is required for the induction of apoptosis by DNA-damaging chemotherapy or radiation. Therefore, identification of the molecular determinants of p53-dependent cell death may aid in the design of effective therapies of p53-deficient cancers. We investigated whether p53-dependent apoptosis requires activation of CPP32beta (caspase 3), a cysteine protease that has been found to mediate apoptosis in response to ligation of the Fas molecule or to granzyme B, a component of CTL lytic granules. Irradiation-induced apoptosis was associated with p53-dependent activation of CPP32beta-related proteolysis, and normal thymocytes were protected from irradiation by Acetyl-Asp-Glu-Val-Asp-CHO (Ac-DEVD-CHO), a specific inhibitor of CPP32beta. We next examined whether the Fas system is required for p53-dependent apoptosis and whether stimuli that induce activation of CPP32beta induce apoptosis in p53-deficient cells. Thymocytes or activated T cells from Fas-deficient mice were resistant to apoptosis induced by ligation of Fas or CD3, respectively, but remained normally susceptible to irradiation. Thymocytes from p53-deficient mice, although resistant to DNA damage, remained sensitive to CPP32beta-mediated apoptosis induced by ligation of Fas or CD3, or by exposure to cytotoxic T cells. These results demonstrate that DNA damage-induced apoptosis of T cells requires p53-mediated activation of CPP32beta by a mechanism independent of Fas/FasL interactions and suggest that immunological or molecular methods of activating CPP32beta may be effective at inducing apoptosis in p53-deficient cancers that are resistant to conventional chemotherapy or irradiation.

Selective radiosensitization of p53-deficient cells by caffeine-mediated activation of p34cdc2 kinase

The induction of tumor cell death by anticancer therapy results from a genetic program of autonomous cell death termed apoptosis. Because the p53 tumor suppressor gene is a critical component for induction of apoptosis in response to DNA damage, its inactivation in cancers may be responsible for their resistance to genotoxic anticancer agents. The cellular response to DNA damage involves a cell-cycle arrest at both the G1/S and G2/M transitions; these checkpoints maintain viability by preventing the replication or segregation of damaged DNA. The arrest at the G1 checkpoint is mediated by p53-dependent induction of p21WAF1/CIP1, whereas the G2 arrest involves inactivation of p34cdc2 kinase. Following DNA damage, p53-deficient cells fail to arrest at G1 and accumulate at the G2/M transition. We demonstrate that abrogation of G2 arrest by caffeine-mediated activation of p34cdc2 kinase results in the selective sensitization of p53-deficient primary and tumor cells to irradiation-induced apoptosis. These data suggest that pharmacologic activation of p34cdc2 kinase may be a useful therapeutic strategy for circumventing the resistance of p53-deficient cancers to genotoxic anticancer agents.

Is cancer dangerous to the immune system?

The hypothesis of immunologic surveillance of neoplasia is predicated on the theory that the immune system is capable of discriminating self from foreign antigens, and that tumor-specific antigens are regarded by the immune system as nonself. We propose here an alternate view, that the immune system has evolved to detect danger by employing 'professional' antigen-presenting cells as sentinels of tissue distress. In this model, cancers do not appear dangerous to the immune system, so that the default response of T cells to tumors is to be turned off. We discuss the implications for immunotherapy of malignancy.

Neonatal tolerance revisited: turning on newborn T cells with dendritic cells

For some time it has been thought that antigenic challenge in neonatal life is a tolerogenic rather than immunogenic event. Reexamination of the classic neonatal tolerance experiments of Billingham, Brent, and Medawar showed that tolerance is not an intrinsic property of the newborn immune system, but that the nature of the antigen-presenting cell determines whether the outcome is neonatal tolerance or immunization.

Cytotoxic T cells overcome BCR-ABL-mediated resistance to apoptosis

Chronic myeloid leukemia is a disease marked by expanded clonal hematopoiesis; it is incurable by chemotherapy or radiation but is cured in a majority of patients receiving bone marrow transplantation from nonidentical sibling donors, an outcome generally attributed to a T cell-mediated graft-versus-leukemia effect. In this report, we examine the effect of the P210BCR-ABL fusion protein of the BCR-ABL oncogene, the molecular hallmark of chronic myelogenous leukemia, on the sensitivity of mouse cell lines to apoptosis induced by chemotherapy, radiation, or activated cytotoxic T lymphocytes (CTLs). We find that, although cells expressing P210BCR-ABL by gene transfer are more resistant than their normal counterparts to apoptosis induced by chemotherapy or radiation, they are equally susceptible to apoptosis induced by alloreactive CTLs. These results show that CTLs overcome BCR-ABL-mediated resistance to apoptosis and, therefore, provide a biological correlation for the success of allogeneic bone marrow transplantation in chronic myelogenous leukemia.

B cells turn off virgin but not memory T cells

There are three possible outcomes when a T cell recognizes a cell bearing a self or foreign antigen. (i) The T cell is not sufficiently signaled and is unaffected. (ii) The T cell is activated. (iii) The T cell is turned off. The differentiation state of the T cell is critical to the outcome. Although both virgin and memory T cells can be activated by antigens presented by "professional" antigen-presenting cells such as dendritic cells, they differ in their responses to B cells. Experienced T cells respond to antigen presented by B cells, whereas virgin T cells are rendered tolerant. These findings may relate to the phenomena of low- and high-zone tolerance, neonatal tolerance, and the beneficial effect of blood transfusions on allograft survival.

Clinical manifestations of acute infection with human immunodeficiency virus in a cohort of gay men

During a prospective study of the natural history of human immunodeficiency virus (HIV) infection in a cohort of gay/bisexual men, information on self-reported symptoms lasting for 3 or more days during the previous 6 months was collected without knowledge of the subject's HIV serological status. Twenty-two people were retrospectively found to have seroconverted to HIV during the interval. Each seroconverter was matched to two seronegative and two seropositive controls. Matched case-control analyses using the seronegative controls determined that the following symptoms lasting for 3 or more days were associated with new HIV infection: fever greater than 37.7 degrees C, swollen lymph nodes, night sweats and headaches. Matched case-control analyses using the seropositive controls determined that the following symptoms lasting for 3 or more days were associated with new HIV infection: fatigue, fever greater than 37.7 degrees C, swollen lymph nodes, night sweats and headaches. It was notable that the majority of seroconversions were not associated with any symptoms lasting for 3 or more days. Due to their non-specificity, symptoms associated with seroconversion are not likely to have a high positive predictive value. In high risk populations, however, appearance of these symptoms may facilitate identification of early infection that may be important for studies of natural history or for optimal timing for initiating antiviral therapy.