Radiation Therapy Sensitizes Head-and-Neck Cancer Cells to Killing by Chimeric Antigen Receptor (CAR)-NK Cells Targeting CD70

PURPOSE/OBJECTIVE(S)

CAR-T cell therapy is limited by toxicity, high cost, logistical manufacturing issues in the autologous setting and risk of GVHD in the allogeneic setting. Substitution of T cells with NK cells opens the possibility for an allogeneic off-the-shelf product with a better safety profile. However, the inadequate efficacy of CAR-NK cells against solid tumors can be extrapolated from experience with CAR-T cells. There is limited but promising preclinical evidence that radiation therapy (RT) enhances CAR-T cell tumoricidal activity against solid tumors. However, there is no data examining the potential synergy between RT and CAR-NK cell therapy.

MATERIALS/METHODS

We engineered CAR-NK cells with CD27 receptor as extracellular domain to target its natural ligand CD70, which is overexpressed in head-and-neck cancers (HNSCC). CAR-NK cell killing was assessed real-time through xCELLigence cytotoxicity assays. CD70+ OQ01 human HNSCCs were used for most experiments. FaDu is a CD70- HNSCC (negative ctrl). UMRC3 is a CD70+ kidney cancer cell line (positive ctrl). CD70 expression pre- and post-RT was assessed by flow cytometry and Western blot. Ionizing RT was compared at 5 doses: 0, 1.75, 3.5, 7, and 14 Gy. A single dose of 3.5 Gy was used for most experiments. Post-radiation effects were generally assessed at 3 days or 9 days post-RT. Intracellular staining was used to assess NK cell expression of IFN-γ, CD107a, and TNF-α by flow cytometry. CD27/CD70 interaction blockade was through α-CD27 pre-treatment of CAR-NK cells.

RESULTS

OQ01 HNSCCs heterogeneously express CD70 and are killed by CD70 CAR-NK cells in vitro. Pre-conditioning low-dose RT of 3.5 Gy applied to OQ01 HNSCCs 3 days prior to coculture with NK cells enhances CD70 CAR-NK cell killing, with ∼30% increased cytotoxicity against the tumor cells. Low-dose RT by itself did not induce acute cytolysis. As a possible mechanism for the increased sensitivity of irradiated OQ01 cells to CD70 CAR-NK cells, we found that RT enhances CD70 expression among HNSCCs in a dose-dependent manner. There was no increase in NK cell expression of IFN-γ, CD107a, and TNF-α with exposure to irradiated target cells. CD27/CD70 blockade does not solely abrogate RT-induced sensitization toward CAR-NK cell killing. Despite RT induction of transient increased expression of CD70, which normalizes by 9 days post-RT, there is persistent increase in RT-synergized target cell killing even at this later timepoint. Thus, altogether, RT sensitizes CD70-expressing HNSCC cells to CAR-NK cell killing in vitro.

CONCLUSION

This work represents the first preclinical study to identify the synergy of RT and CAR-NK cell therapy in solid tumors and is the first demonstration of CAR-NK cell activity against human HNSCCs. We show significantly enhanced potency of CAR-NK cells against irradiated tumor cells in vitro. Collectively, this research will be vital to guide efforts expanding into other target antigens and tumor types.

Gut microbiome modulates response to anti-PD-1 immunotherapy in melanoma patients

Preclinical mouse models suggest that the gut microbiome modulates tumor response to checkpoint blockade immunotherapy; however, this has not been well-characterized in human cancer patients. Here we examined the oral and gut microbiome of melanoma patients undergoing anti-programmed cell death 1 protein (PD-1) immunotherapy (n = 112). Significant differences were observed in the diversity and composition of the patient gut microbiome of responders versus nonresponders. Analysis of patient fecal microbiome samples (n = 43, 30 responders, 13 nonresponders) showed significantly higher alpha diversity (P < 0.01) and relative abundance of bacteria of the Ruminococcaceae family (P < 0.01) in responding patients. Metagenomic studies revealed functional differences in gut bacteria in responders, including enrichment of anabolic pathways. Immune profiling suggested enhanced systemic and antitumor immunity in responding patients with a favorable gut microbiome as well as in germ-free mice receiving fecal transplants from responding patients. Together, these data have important implications for the treatment of melanoma patients with immune checkpoint inhibitors.

Ibrutinib modulates the immunosuppressive CLL microenvironment through STAT3-mediated suppression of regulatory B-cell function and inhibition of the PD-1/PD-L1 pathway

Ibrutinib, a covalent inhibitor of Bruton Tyrosine Kinase (BTK), is approved for treatment of patients with relapsed/refractory or treatment-naïve chronic lymphocytic leukemia (CLL). Besides directly inhibiting BTK, ibrutinib possesses immunomodulatory properties through targeting multiple signaling pathways. Understanding how this ancillary property of ibrutinib modifies the CLL microenvironment is crucial for further exploration of immune responses in this disease and devising future combination therapies. Here, we investigated the mechanisms underlying the immunomodulatory properties of ibrutinib. In peripheral blood samples collected prospectively from CLL patients treated with ibrutinib monotherapy, we observed selective and durable downregulation of PD-L1 on CLL cells by 3 months post-treatment. Further analysis showed that this effect was mediated through inhibition of the constitutively active signal transducer and activator of transcription 3 (STAT3) in CLL cells. Similar downregulation of PD-1 was observed in CD4+ and CD8+ T cells. We also demonstrated reduced interleukin (IL)-10 production by CLL cells in patients receiving ibrutinib, which was also linked to suppression of STAT3 phosphorylation. Taken together, these findings provide a mechanistic basis for immunomodulation by ibrutinib through inhibition of the STAT3 pathway, critical in inducing and sustaining tumor immune tolerance. The data also merit testing of combination treatments combining ibrutinib with agents capable of augmenting its immunomodulatory effects.

Cord blood NK cells engineered to express IL-15 and a CD19-targeted CAR show long-term persistence and potent antitumor activity

Chimeric antigen receptors (CARs) have been used to redirect the specificity of autologous T cells against leukemia and lymphoma with promising clinical results. Extending this approach to allogeneic T cells is problematic as they carry a significant risk of graft-versus-host disease (GVHD). Natural killer (NK) cells are highly cytotoxic effectors, killing their targets in a non-antigen-specific manner without causing GVHD. Cord blood (CB) offers an attractive, allogeneic, off-the-self source of NK cells for immunotherapy. We transduced CB-derived NK cells with a retroviral vector incorporating the genes for CAR-CD19, IL-15 and inducible caspase-9-based suicide gene (iC9), and demonstrated efficient killing of CD19-expressing cell lines and primary leukemia cells in vitro, with marked prolongation of survival in a xenograft Raji lymphoma murine model. Interleukin-15 (IL-15) production by the transduced CB-NK cells critically improved their function. Moreover, iC9/CAR.19/IL-15 CB-NK cells were readily eliminated upon pharmacologic activation of the iC9 suicide gene. In conclusion, we have developed a novel approach to immunotherapy using engineered CB-derived NK cells, which are easy to produce, exhibit striking efficacy and incorporate safety measures to limit toxicity. This approach should greatly improve the logistics of delivering this therapy to large numbers of patients, a major limitation to current CAR-T-cell therapies.

Latent cytomegalovirus infection enhances anti-tumour cytotoxicity through accumulation of NKG2C+ NK cells in healthy humans

Cytomegalovirus (CMV) infection markedly expands NKG2C+/NKG2A- NK cells, which are potent killers of infected cells expressing human leucocyte antigen (HLA)-E. As HLA-E is also over-expressed in several haematological malignancies and CMV has been linked to a reduced risk of leukaemic relapse, we determined the impact of latent CMV infection on NK cell cytotoxicity against four tumour target cell lines with varying levels of HLA-E expression. NK cell cytotoxicity against K562 (leukaemia origin) and U266 (multiple myeloma origin) target cells was strikingly greater in healthy CMV-seropositive donors than seronegative donors and was associated strongly with target cell HLA-E and NK cell NKG2C expression. NK cell cytotoxicity against HLA-E transfected lymphoma target cells (221.AEH) was ∼threefold higher with CMV, while NK cell cytotoxicity against non-transfected 721.221 cells was identical between the CMV groups. NK cell degranulation (CD107a(+) ) and interferon (IFN)-γ production to 221.AEH cells was localized almost exclusively to the NKG2C subset, and antibody blocking of NKG2C completely eliminated the effect of CMV on NK cell cytotoxicity against 221.AEH cells. Moreover, 221.AEH feeder cells and interleukin (IL)-15 were found to expand NKG2C(+) /NKG2A(-) NK cells preferentially from CMV-seronegative donors and increase NK cell cytotoxicity against HLA-E(+) tumour cell lines. We conclude that latent CMV infection enhances NK cell cytotoxicity through accumulation of NKG2C(+) NK cells, which may be beneficial in preventing the initiation and progression of haematological malignancies characterized by high HLA-E expression.

Umbilical cord blood graft engineering: challenges and opportunities

We are entering a very exciting era in umbilical cord blood transplantation (UCBT), where many of the associated formidable challenges may become treatable by ex vivo graft manipulation and/or adoptive immunotherapy utilizing specific cellular products. We envisage the use of double UCBT rather than single UCBT for most patients; this allows for greater ability to treat larger patients as well as to manipulate the graft. Ex vivo expansion and/or fucosylation of one cord will achieve more rapid engraftment, minimize the period of neutropenia and also give certainty that the other cord will provide long-term engraftment/immune reconstitution. The non-expanded (and future dominant) cord could be chosen for characteristics such as better HLA matching to minimize GvHD, or larger cell counts to enable part of the unit to be utilized for the development of specific cellular therapies such as the production of virus-specific T-cells or chimeric-antigen receptor T-cells which are reviewed in this study.

FOXP3 is a direct target of miR15a/16 in umbilical cord blood regulatory T cells

Exact mechanism of action of umbilical cord blood (CB)-derived regulatory T cells (Tregs) in the prevention of GVHD remains unclear. On the basis of selective overexpression of peptidase inhibitor 16 in CB Tregs, we explored the related p53 pathway, which has been shown to negatively regulate miR15a/16 expression. Significantly lower levels of miR15a/16 were observed in CB Tregs when compared with conventional CB T cells (Tcons). In a xenogeneic GVHD mouse model, lower levels of miR15a/16 were also found in Treg recipients, which correlated with a better GVHD score. Forced overexpression of miR15a/16 in CB Tregs led to inhibition of FOXP3 and CTLA4 expression and partial reversal of Treg-mediated suppression in an allogeneic mixed lymphocyte reaction that correlated with the reversal of FOXP3 demethylation in CB Tregs. On the other hand, miR15a/16 knockdown in CB Tcons led to expression of FOXP3 and CTLA4 and suppression of allogeneic lymphocyte proliferation. Using a luciferase-based mutagenesis assay, FOXP3 was determined to be a direct target of miR15a and miR16. We propose that miR15a/16 has an important role in mediating the suppressive function of CB Tregs and these microRNAs may have a 'toggle-switch' function in Treg/Tcon plasticity.

Ubiquitin-like (UBX)-domain-containing protein, UBXN2A, promotes cell death by interfering with the p53-Mortalin interactions in colon cancer cells

Mortalin (mot-2) induces inactivation of the tumor suppressor p53's transcriptional and apoptotic functions by cytoplasmic sequestration of p53 in select cancers. The mot-2-dependent cytoprotective function enables cancer cells to support malignant transformation. Abrogating the p53-mot-2 interaction can control or slow down the growth of cancer cells. In this study, we report the discovery of a ubiquitin-like (UBX)-domain-containing protein, UBXN2A, which binds to mot-2 and consequently inhibits the binding between mot-2 and p53. Genetic analysis showed that UBXN2A binds to mot-2's substrate binding domain, and it partly overlaps p53's binding site indicating UBXN2A and p53 likely bind to mot-2 competitively. By binding to mot-2, UBXN2A releases p53 from cytosolic sequestration, rescuing the tumor suppressor functions of p53. Biochemical analysis and functional assays showed that the overexpression of UBXN2A and the functional consequences of unsequestered p53 trigger p53-dependent apoptosis. Cells expressing shRNA against UBXN2A showed the opposite effect of that seen with UBXN2A overexpression. The expression of UBXN2A and its apoptotic effects were not observed in normal colonic epithelial cells and p53-/- colon cancer cells. Finally, significant reduction in tumor volume in a xenograft mouse model in response to UBXN2A expression was verified in vivo. Our results introduce UBXN2A as a home defense response protein, which can reconstitute inactive p53-dependent apoptotic pathways. Inhibition of mot-2-p53 interaction by UBXN2A is an attractive therapeutic strategy in mot-2-elevated tumors.

KIR2DS1 genotype predicts for complete cytogenetic response and survival in newly diagnosed chronic myeloid leukemia patients treated with imatinib

Natural killer (NK) cells are expanded in chronic myeloid leukemia (CML) patients on tyrosine kinase inhibitors (TKI) and exert cytotoxicity. The inherited repertoire of killer immunoglobulin-like receptors (KIR) may influence response to TKI. We investigated the impact of KIR-genotype on outcome in 166 chronic phase CML patients on first-line imatinib treatment. We validated our findings in an independent patient group. On multivariate analysis, KIR2DS1 genotype (RR=1.51, P=0.03) and Sokal risk score (low-risk RR=1, intermediate-risk RR=1.53, P=0.04, high-risk RR=1.69, P=0.034) were the only independent predictors for failure to achieve complete cytogenetic response (CCyR). Furthermore, KIR2DS1 was the only factor predicting shorter progression-free (PFS) (RR=3.1, P=0.03) and overall survival (OS) (RR=2.6, P=0.04). The association between KIR2DS1 and CCyR, PFS and OS was validated by KIR genotyping in 174 CML patients on first-line imatinib in the UK multi-center SPIRIT-1 trial; in this cohort, KIR2DS1(+) patients had significantly lower 2-year probabilities of achieving CCyR (76.9 vs 87.9%, P=0.003), PFS (85.3 vs 98.1%, P=0.007) and OS (94.4 vs 100%, P=0.015) than KIR2DS1(-) patients. The impact of KIR2DS1 on CCyR was greatest when the ligand for the corresponding inhibitory receptor, KIR2DL1, was absent (P=0.00006). Our data suggest a novel role for KIR-HLA immunogenetics in CML patients on TKI.

Modeling pathogenesis of Huntington's disease with inducible neuroprogenitor cells

Huntington's disease (HD) is caused by an abnormal expansion of CAG trinucleotide repeats encoding polyglutamine (polyQ) in the first exon of the huntingtin (htt) gene. Despite considerable efforts, the pathogenesis of HD remains largely unclear due to a paucity of models that can reliably reproduce the pathological characteristics of HD. Here, we report a neuronal cell model of HD using the previously established tetracycline regulated rat neuroprogenitor cell line, HC2S2. Stable expression of enhanced green fluorescence protein tagged htt exon 1 (referred to as 28Q and 74Q, respectively) in the HC2S2 cells did not affect rapid neuronal differentiation. However, compared to the cells expressing wild type htt, the cell line expressing mutant htt showed an increase in time-dependent cell death and neuritic degeneration, and displayed increased vulnerability to oxidative stress. Increased protein aggregation during the process of neuronal aging or when the cells were exposed to oxidative stress reagents was detected in the cell line expressing 74Q but not in its counterpart. These results suggest that the neuroprogenitor cell lines mimic the major neuropathological characteristics of HD and may provide a useful tool for studying the neuropathogenesis of HD and for high throughput screening of therapeutic compounds.

Hematopoietic stem cells and progenitors of chronic myeloid leukemia express leukemia-associated antigens: implications for the graft-versus-leukemia effect and peptide vaccine-based immunotherapy

The cure of chronic myeloid leukemia (CML) patients following allogeneic stem cell transplantation (SCT) is attributed to graft-versus-leukemia (GVL) effects targeting alloantigens and/or leukemia-associated antigens (LAA) on leukemia cells. To assess the potential of LAA-peptide vaccines in eliminating leukemia in CML patients, we measured WT1, PR3, ELA2 and PRAME expression in CD34+ progenitor subpopulations in CML patients and compared them with minor histocompatibility antigens (mHAgs) HA1 and SMCY. All CD34+ subpopulations expressed similar levels of mHAgs irrespective of disease phase, suggesting that in the SCT setting, mHAgs are the best target for GVL. Furthermore, WT1 was consistently overexpressed in advanced phase (AdP) CML in all CD34+ subpopulations, and mature progenitors of chronic phase (CP) CML compared to healthy individuals. PRAME overexpression was limited to more mature AdP-CML progenitors only. Conversely, only CP-CML progenitors had PR3 overexpression, suggesting that PR1-peptide vaccines are only appropriate in CP-CML. Surface expression of WT1 protein in the most primitive hematopoietic stem cells in AdP-CML suggest that they could be targets for WT1 peptide-based vaccines, which in combination with PRAME, could additionally improve targeting differentiated progeny, and benefit patients responding suboptimally to tyrosine kinase inhibitors, or enhance GVL effects in SCT patients.

Transfer of PR1-specific T-cell clones from donor to recipient by stem cell transplantation and association with GvL activity

BACKGROUND

The curative effects of GvL following transfer of donor-derived T cells during allogeneic stem cell transplantation (SCT) are well established. However, little is known about the nature, origin and kinetics of the anti-leukemic T-cell responses involved.

METHODS

We used quantitative real-time PCR (qRT-PCR) for interferongamma mRNA production (IFN-gamma) and PR1/HLA-A*0201 tetramer staining to detect PR1-specific CD8+ T-cell activity in a donor and a patient with CML. Unbiased strand switch anchored RT-PCR was used to further characterize specific clones in PR1 sorted CD8+ T-cell populations.

RESULTS

We identified PR1-specific CD8(+) T-cell clones from a donor pre-transplant, and demonstrated their transfer in the recipient's blood post-SCT using molecular tracking of Ag-specific T-cell receptors. PR1-specific CD8(+) T-cell populations were polyclonal, with a range of functional avidities for cognate Ag, and displayed predominantly effector memory phenotype early post-SCT, suggesting active stimulation in vivo. Expansion of these PR1-specific CD8(+) T-cell clones in the recipient was followed by complete remission of CML.

DISCUSSION

This report represents the first direct demonstration that PR1-specific CD8(+) T-cell clones can be transferred during SCT, and supports the feasibility of pre-transplant vaccination strategies that aim to boost the number of anti-leukemic T cells in the graft.

Rapid natural killer cell recovery determines outcome after T-cell-depleted HLA-identical stem cell transplantation in patients with myeloid leukemias but not with acute lymphoblastic leukemia

Natural killer (NK) cells are the first lymphocytes to recover after allogeneic stem cell transplantation (SCT) and can exert powerful graft-versus-leukemia (GVL) effects determining transplant outcome. Conditions governing NK cell alloreactivity and the role of NK recovery in sibling SCT are not well defined. NK cells on day 30 post-transplant (NK30) were measured in 54 SCT recipients with leukemia and donor and recipient killer immunoglobulin-like receptor (KIR) genotype determined. In univariate analysis, donor KIR genes 2DL5A, 2DS1, 3DS1 (positive in 46%) and higher numbers of inhibitory donor KIR correlated with higher NK30 counts and were associated with improved transplant outcome. NK30 counts also correlated directly with the transplant CD34 cell dose and inversely with the CD3+ cell dose. In multivariate analysis, the NK30 emerged as the single independent determinant of transplant outcome. Patients with NK30 >150/microl had less relapse (HR 18.3, P=0.039), acute graft-versus-host disease (HR 3.2, P=0.03), non-relapse mortality (HR 10.7, P=0.028) and improved survival (HR 11.4, P=0.03). Results suggest that T cell-depleted SCT might be improved and the GVL effect enhanced by selecting donors with favorable KIR genotype, and by optimizing CD34 and CD3 doses.

Review of current knowledge on HPV vaccination: an appendix to the European Guidelines for Quality Assurance in Cervical Cancer Screening

The recognition of a strong etiological relationship between infection with high-risk human papillomavirusses and cervical cancer has prompted research to develop and evaluate prophylactic and therapeutic vaccines. One prophylactic quadrivalent vaccine using L1 virus-like particles (VLP) of HPV 6, 11, 16 and 18 is available on the European market since the end of 2006 and it is expected that a second bivalent vaccine containing VLPs of HPV16 and HPV18 will become available in 2007. Each year, HPV16 and HPV18 cause approximately 43,000 cases of cervical cancer in the European continent. Results from the phase-IIb and III trials published thus far indicate that the L1 VLP HPV vaccine is safe and well-tolerated. It offers HPV-naive women a very high level of protection against HPV persistent infection and cervical intra-epithelial lesions associated with the types included in the vaccine. HPV vaccination should be offered to girls before onset of sexual activity. While prophylactic vaccination is likely to provide important future health gains, cervical screening will need to be continued for the whole generation of women that is already infected with the HPV types included in the vaccine. Phase IV studies are needed to demonstrate protection against cervical cancer and to verify duration of protection, occurrence of replacement by non-vaccine types and to define future policies for screening of vaccinated cohorts. The European Guidelines on Quality Assurance for Cervical Cancer Screening provides guidance for secondary prevention by detection and management of precursors lesions of the cervix. The purpose of the appendix on vaccination is to present current knowledge. Developing guidelines for future use of HPV vaccines in Europe, is the object of a new grant offered by the European Commission.

Phenotype and function of a CD56+ peripheral blood monocyte

G-CSF primed CD34 cells cultured for 2-3 weeks in IL-2 and stem cell factor generate CD56(high) cells with phenotypic and morphologic features of NK cells, and a novel adherent CD56(low) CD16- population expressing myeloid markers (CD33 and HLA-DR). We hypothesized that similar cells might also occur in peripheral blood. In 13/13 normal individuals, we found a circulating population of CD56(low), CD33+, FcgammaRI+, FcgammaRII+, HLA-DR+, CD11b(high), CD14+ monocytes closely resembling the cultured CD56(low)CD33+ cells. They may represent a normal counterpart of the CD56+ CD33+ hybrid myeloid/natural killer cell leukemia. Their mean frequency was 1.3+/-1% (standard deviation), range 0.16-3.5%, of total mononuclear cells. CD56(low)CD33+ cells, primed with cytomegalovirus antigen, induced autologous T-lymphocyte proliferation comparably to CD56-, CD14+ peripheral blood monocytes (PBM). Conversely, CD56(low) cells induced greater T-cell proliferation than CD56- PBM when lymphocyte responders were HLA mismatched. Unstimulated CD56(low)CD33+ cells showed a low antiproliferative effect on K562, which was increased upon LPS stimulation. The pattern of cytokine production by CD56(low)CD33+ cells and PBM largely overlapped; however, they produced detectable levels of IL-6 and IL-1beta. These results define a minor monocyte population with distinct phenotypic and functional features.

Proteasomal interactors control activities as diverse as the cell cycle and glutaminergic neurotransmission

The six regulatory non-redundant ATPases in the base of the 19 S regulator of the 26 S proteasome belong to the AAA superfamily of ATPases. Yeast two-hybrid genetic screens, biochemical analyses and cell biological studies have identified and characterized new interactors of the human S6 (rpt3) and S8 (rpt6) ATPases of the 19 S regulator of the 26 S proteasome. The S6 ATPase interacts with gankyrin. This protein is found in purified human 26 S proteasomes and in a smaller complex(es) containing CDK4 and free S6 ATPase. Gankyrin overexpression causes the phosphorylation of the retinoblastoma protein (pRb) and the release of E2F transcription factor to trigger the expression of DNA synthesis genes. Gankyrin is oncogenic in nude mice and is overexpressed in hepatocellular carcinoma cells (HCCs). The S8 ATPase interacts with members of the large Homer-3 protein family. There are three Homer genes; the Homer 1 and 2 gene products control trafficking and calcium-store-related functions of metabotropic glutamate receptors (e.g. mGluR1alpha). Homer-3A11 by binding to the S8 ATPase brings mGluR1alpha to the 26 S proteasome for degradation. The degradation of mGluR1alpha is blocked by proteasomal inhibitors and by overexpression of the N-terminus of Homer which binds to the receptor. The S8 ATPase and mGluR1alpha are co-localized in Purkinje dendrites in rat cerebellum. The data are discussed in terms of the regulation of the cell cycle and glutaminergic receptor functions by the 26 S proteasome.

Stem cell transplantation for chronic myeloid leukaemia: the role of infused marrow cell dose

INTRODUCTION

Allogeneic stem cell transplantation is a potentially curative option for patients with CML. The optimal donor is an HLA-identical sibling but transplants using unrelated volunteers can also be successful. The factors influencing survival after allogeneic SCT for CML are reasonably well defined. Recently however, the Seattle group have emphasised the influence of a high marrow cell dose on outcome following volunteer unrelated donor SCT for high risk acute leukaemia.

MATERIALS AND METHODS

We have sought to define factors impacting on transplant related mortality (TRM) in a population of CML patients after allografting with matched sibling or alternative stem cell donors at a single centre over a 20-year period, with emphasis on infused marrow cell dose. Factors entered into a multivariate analysis were: recipient age, recipient CMV serostatus, disease phase, donor sex, cell dose and frequency of CTLP reactivity.

RESULTS

In multivariate analysis four factors had an adverse effect on TRM when using a VUD: low marrow cell dose (<3.65 x 10(8) TNC/kg, relative risk 2.05, CI 1.08-3.90, P = 0.029), late disease phase (relative risk 1.68, CI 1.03-2.74, P = 0.038), patient CMV seropositivity (relative risk 1.98, CI 1.25-3.13, P = 0.004) and high frequency of CTLP (relative risk 1.93, CI 1.18-3.13, P = 0.008). For HLA-identical sibling donor transplants the only factor that adversely impacted on TRM was late disease phase (P = 0.0004 in univariate analysis).

CONCLUSION

High infused cell dose is a new modifiable factor associated with reduced TRM following allogeneic SCT using an unrelated donor for the treatment of CML. The data support the recommendation that bone marrow harvest teams should aim to collect the highest possible number of nucleated cells for recipients of unrelated donor transplants.

Treatment of relapse after allogeneic bone marrow transplantation with reduced intensity conditioning (FLAG +/- Ida) and second allogeneic stem cell transplant

Acute leukaemias in relapse after allogeneic stem cell transplantation (SCT) respond poorly to donor leucocyte infusions (DLI) compared with chronic myeloid leukaemia (CML), at least in part because of faster disease kinetics. Fludarabine-containing 'non-myeloablative' chemotherapy followed by further allo SCT may offer more rapid and effective disease control. We report 14 patients with relapse after allo SCT for acute leukaemia [seven acute myeloid leukaemia (AML), five acute lymphoblastic leukaemia (ALL)] or refractory anaemia with excess blasts in transformation (RAEB-t, n = 2) treated with fludarabine, high-dose cytosine arabinoside (ara-C) and granulocyte colony-simulating factor (G-CSF) with (n = 10) or without (n = 2) idarubicin (FLAG +/- Ida) or DaunoXome (FLAG-X) (n = 2) and second allo SCT from the original donor. Donors were fully human leucocyte antigen (HLA) -matched in 13 cases with a single class A mismatch in one. Actuarial overall survival was 60% and disease-free survival was 26% at 58 months. Remissions after the second SCT were longer than those after the first bone marrow transplantation (BMT) in eight of the 13 assessable patients to date. Haematopoietic recovery was rapid. Transplants were well tolerated with no treatment-related deaths. The major complication was graft-versus-host disease (GvHD, acute >/= grade II-2 cases, chronic - eight cases, two limited, six extensive) although there have been no deaths attributable to this. FLAG +/- Ida and second allo SCT is a safe and useful approach and may be more effective than DLI in the treatment of acute leukaemias relapsing after conventional allo SCT.

Investigation of ethnic neutropenia by assessment of bone marrow colony-forming cells

Healthy individuals with African ancestry have lower neutrophil counts than Caucasians. It has previously been postulated that this was consequent on either a diminished bone marrow granulocyte reserve or an altered distribution of neutrophils between the circulating and marginated granulocyte pools. Recent indirect evidence supports the former hypothesis. In this study we have compared the number of granulocyte plus granulocyte-macrophage colony-forming units (CFUs) in the bone marrow of healthy African and Afro-Caribbean subjects with the number of CFUs in the bone marrow of healthy age and sex-matched Caucasians. We found the group with African ancestry to have significantly fewer CFUs than the Caucasian group. There was no evidence of any qualitative difference between the CFUs of the two ethnic groups: they showed similar sensitivity to granulocyte-monocyte colony stimulating factor and similar enhancement of growth when cultured with a larger range of cytokines. These observations suggest that ethnic neutropenia observed in those with African ancestry is likely to result from reduced numbers of bone marrow progenitor cells in comparison with numbers present in Caucasians.

Immune neutropenia associated with anti-human neutrophil antigen-2a (NB1) antibodies following unrelated donor stem cell transplantation for chronic myeloid leukaemia: perpetuation by granulocyte colony-stimulating factor

A case of immune neutropenia following unrelated stem cell transplantation for chronic myeloid leukaemia is described. The neutropenia developed following herpes zoster viral infection and was associated with antibodies to the human neutrophil antigen (HNA)-2a (formerly known as NB1). The neutropenia was prolonged, profound and unresponsive to granulocyte colony-stimulating factor (GCSF). The neutrophil count recovered after GCSF was discontinued. HNA-2a has been reported to be upregulated following GCSF administration. In the present case, it appears that the immune neutropenia may have been perpetuated by GCSF administration.

Early detection of BCR-ABL transcripts by quantitative reverse transcriptase-polymerase chain reaction predicts outcome after allogeneic stem cell transplantation for chronic myeloid leukemia

The reverse transcriptase-polymerase chain reaction (RT-PCR) has become widely used for monitoring minimal residual disease after allogeneic stem cell transplantation (SCT) for chronic myeloid leukemia (CML). However, most of these studies were performed using qualitative RT-PCR, and the interpretation of the results obtained has been conflicting. The correlation of a quantitative RT-PCR test performed early after SCT (at 3 to 5 months) and long-term outcome of CML patients surviving for more than 6 months was studied. Between January 1991 and June 1999, data from 138 CML patients who received allografts were evaluated. Early RT-PCR results were classified as (1) negative if there were no BCR-ABL transcripts detected (n = 61), (2) positive at low level if the total number of BCR-ABL transcripts was less than 100 per microg RNA and/or the BCR-ABL/ABL ratio was less than 0.02% (n = 14), or (3) positive at high level if transcript levels exceeded the thresholds defined above (n = 63). Three years after SCT the cumulative incidence of relapse was 16.7%, 42.9%, and 86.4%, respectively (P =.0001). The relationship between BCR-ABL transcript level and probability of relapse was apparent whether patients had received sibling or unrelated donor SCT and also whether or not the transplantation was T cell depleted. The results suggest that quantitative RT-PCR performed early after SCT is useful for predicting outcome and may help to define the need for further treatment.

Exercise induced mobilisation of the marginated granulocyte pool in the investigation of ethnic neutropenia

This study was designed to determine whether ethnic neutropenia is caused by an increased proportion of neutrophils being present in the marginated granulocyte pool. Thirty two healthy volunteers, half of whom were African or Afro-Caribbean and half of whom were white, exercised vigorously for 10 minutes on a step machine to mobilise granulocytes from the marginated granulocyte pool into the circulating granulocyte pool. The amount of work performed and the pulse rate response of the two ethnic groups were compared to determine whether the exercise carried out was comparable. A full blood count and an automated differential count were performed before and after the exercise. The haemoglobin concentration, platelet count, and absolute counts of total leucocytes and leucocyte subsets before and after exercise were compared in each individual and the values in the two ethnic groups both before and after exercise were compared. The absolute increase in neutrophils in the two ethnic groups was compared. The African/Afro-Caribbean group was found to have a reduced rather than enhanced ability to mobilise neutrophils from the marginated granulocyte pool. Therefore, increased margination of neutrophils is unlikely to be the cause of ethnic neutropenia.

Loss of singing ability caused by vincristine

Two patients who received vincristine therapy for lymphoma suffered marked impairment of ability to sing as a consequence of neurotoxicity. Slow recovery occurred on drug withdrawal.

Ecstasy induced pneumomediastinum

Two cases are reported of pneumomediastinum induced by the use of Ecstasy, a semi-synthetic hallucinogenic compound related to amphetamine and mescaline which has become established as a recreational drug in the UK since the late 1980s. Both cases recovered without incident, but it is important that the possible complications of this drug be publicised so that at risk subjects can be diagnosed early and managed appropriately.