Analysis of HLA class Ia transcripts in human leukaemias

The immune landscape in BCR-ABL negative myeloproliferative neoplasms: inflammation, infections and opportunities for immunotherapy

Breakpoint cluster region-Abelson (BCR-ABL) negative myeloproliferative neoplasms (MPNs) are chronic myeloid neoplasms initiated by the acquisition of gene mutation(s) in a haematopoietic stem cell, leading to clonal expansion and over-production of blood cells and their progenitors. MPNs encompass a spectrum of disorders with overlapping but distinct molecular, laboratory and clinical features. This includes polycythaemia vera, essential thrombocythaemia and myelofibrosis. Dysregulation of the immune system is key to the pathology of MPNs, supporting clonal evolution, mediating symptoms and resulting in varying degrees of immunocompromise. Targeting immune dysfunction is an important treatment strategy. In the present review, we focus on the immune landscape in patients with MPNs - the role of inflammation in disease pathogenesis, susceptibility to infection and emerging strategies for therapeutic immune modulation. Further detailed work is required to delineate immune perturbation more precisely in MPNs to determine how and why vulnerability to infection differs between clinical subtypes and to better understand how inflammation results in a competitive advantage for the MPN clone. These studies may help shed light on new designs for disease-modifying therapies.

Selection of allogeneic hematopoietic cell transplant donors to optimize natural killer cell alloreactivity

Natural killer (NK) cells are potent mediators of the graft versus leukemia phenomenon critical to the success of allogeneic hematopoietic cell transplantation. Central to calibrating NK effector function via their interaction with class I human leukocyte antigens are the numerous inhibitory killer Ig-like receptors (KIR). The KIR receptors are encoded by a family of polymorphic genes, whose expression is largely stochastic and uninfluenced by human leukocyte antigens genotype. These features provide the opportunity to select hematopoietic cell donors with favorable KIR genotypes that confer enhanced protection from relapse via NK-mediated graft versus leukemia. Over the last 2 decades, a large body of work has emerged examining the use of KIR genotyping to stratify potential donors based on anticipated NK alloreactivity. Overall, these results support KIR-based donor selection for patients undergoing allogeneic hematopoietic cell transplantation for a diagnosis of acute myelogenous leukemia. Despite this, the underlying factors that control NK cell responsiveness are not completely understood, and opportunities remain to refine donor selection using NK cell receptor genotyping. In this review, we will summarize the relevant findings with respect to KIR genotyping as a selection parameter for allogeneic hematopoietic cell donors and address practical considerations with respect to KIR-based selection of donors for patients with myeloid neoplasia.

Purging of malignant cell contamination prior to spermatogonia stem cell autotransplantation to preserve fertility: progress & prospects

PURPOSE OF REVIEW

This systematic review evaluates the state of the art in terms of strategies used to detect and remove contaminated malignant cells from testicular biopsy prior to spermatogonia stem cells (SSCs) autotransplantation to restore fertility.

RECENT FINDINGS

Several trials have been done in past two decades to determine the reliable methods of detecting and purging cancer cells prior to SSCs autotransplantation.

SUMMARY

The success in treating childhood cancer has dramatically increased over the past few decades. This leads to increasing demand for a method of fertility preservation for patients with pediatric cancer, as many cancer therapies can be gonadotoxic. Storing the SSCs prior to chemo- or radiation therapies and transplanting them back has been tested as a method of restoring fertility in rodents and nonhuman primate models. This has promise for restoring fertility in childhood cancer survivors. One of the major concerns is the possibility of malignant cell presence in testicular tissue biopsies that could re-introduce cancer to the patient after SSCs autotransplantation. Non-solid cancers - especially hematologic malignancies - have the risk of being transplanted back into patients after SSCs cryopreservation even if they were only present in small number in the stored testicular tissue biopsy.

The impact of interferon-alpha2 on HLA genes in patients with polycythemia vera and related neoplasms

Gene expression profiling in Philadelphia-negative chronic myeloproliferative neoplasms (MPNs) have unraveled significant deregulation of several immune and inflammation genes of potential importance for clonal evolution. Other mechanisms might be downregulation of major histocompatibility class I and II genes used by tumor cells to escape antitumor T-cell-mediated immune responses. Several genes encoding human leukocyte antigen (HLA) class I and II molecules have been shown to be significantly downregulated. Upregulation of HLA genes is considered one of the mechanisms of action of interferon (IFN)-alpha2, but regulation of these genes during IFN-alpha2 treatment in MPNs has never been studied. Our findings show a significant upregulation of several HLA genes of importance for tumor immune surveillance by IFN-alpha2 treatment in MPNs. This mechanism might enhance the cytotoxic potential of immune cells against MPNs and explain the induction of minimal residual disease by IFN-alpha2 treatment in these patients.

Regulation of Adaptive NK Cells and CD8 T Cells by HLA-C Correlates with Allogeneic Hematopoietic Cell Transplantation and with Cytomegalovirus Reactivation

Mass cytometry was used to investigate the effect of CMV reactivation on lymphocyte reconstitution in hematopoietic cell transplant patients. For eight transplant recipients (four CMV negative and four CMV positive), we studied PBMCs obtained 6 mo after unrelated donor hematopoietic cell transplantation (HCT). Forty cell-surface markers, distinguishing all major leukocyte populations in PBMC, were analyzed with mass cytometry. This group included 34 NK cell markers. Compared with healthy controls, transplant recipients had higher HLA-C expression on CD56(-)CD16(+) NK cells, B cells, CD33(bright) myeloid cells, and CD4CD8 T cells. The increase in HLA-C expression was greater for CMV-positive HCT recipients than for CMV negative recipients. Present in CMV-positive HCT recipients, but not in CMV-negative HCT recipients or controls, is a population of killer cell Ig-like receptor (KIR)-expressing CD8 T cells not previously described. These CD8 T cells coexpress CD56, CD57, and NKG2C. The HCT recipients also have a population of CD57(+)NKG2A(+) NK cells that preferentially express KIR2DL1. An inverse correlation was observed between the frequencies of CD57(+)NKG2C(+) NK cells and CD57(+)NKG2A(+) NK cells. Although CD57(+)NKG2A(+) NK cells are less abundant in CMV-positive recipients, their phenotype is of a more activated cell than the CD57(+)NKG2A(+) NK cells of controls and CMV-negative HCT recipients. These data demonstrate that HCT and CMV reactivation are associated with an increased expression of HLA-C. This could influence NK cell education during lymphocyte reconstitution. The increased inhibitory KIR expression by proliferating CMV-specific CD8 T cells suggests regulatory interactions between HLA-C and KIR might promote Graft-versus-Leukemia effects following transplantation.

Analysis of HLA-ABC locus-specific transcription in normal tissues

We developed a novel human leukocyte antigen HLA-ABC locus-specific quantitative real-time polymerase chain reaction (PCR) to determine the locus-specific gene expression of HLA-ABC in peripheral blood leukocytes (PBLs, n = 53), colon mucosa (n = 15), and larynx mucosa (n = 15). Laser-assisted tissue microdissection allowed us to study the selected cells without interference from surrounding stroma. We report evidence on the specificity of the technique, describing the HLA-ABC locus-specific gene expression patterns found in the PBLs and two solid tissues studied. PBLs showed a higher gene expression of HLA-B than of HLA-A or HLA-C (p = 4.7 × 10(-10) and p = 1.6 × 10(-6), respectively). In solid tissue, HLA-A and HLA-B gene expressions were similar and HLA-C expression lower. In particular, in larynx mucosa, significant differences were found between HLA-A and HLA-C expressions and between HLA-B and HLA-C expressions (p = 6.5 × 10(-4) and p = 8.1 × 10(-4), respectively). The same differences were observed in colon mucosa, but significance was not reached (p = 0.08 and p = 0.06, respectively). Differences in locus-specific regulation may be related to the control of cytotoxic responses of NK and CD8 positive T cells. Gene expression of HLA-ABC specific locus showed no intra-individual variability, but there was a high inter-individual variability. This may result from differences in the expression of common regulatory factors that control HLA-ABC constitutive expression.

Fertility preservation for boys with cancer

Childhood cancer is a curable disease due to the development of chemo- and radiation therapies, but long-term survivors suffer late side-effects including infertility. Cytotoxic agents and radiation impair spermatogenesis and cause oligospermia or azoospermia as well as genetic damage in sperm. To date, the only established option to preserve fertility is cryopreservation of sperm before treatment and artificial reproduction techniques, if men with cancer can ejaculate, but only a quarter of men have banked sperm. Lack of information is the most common reason for failing to bank sperm. However, prepubertal patients who have only spermatogonia and spermatocytes in their testes do not benefit from cryopreservation of their sperm and assisted reproductive techniques. Thus, the only available option is to harvest testicular tissues before treatment for cryopreservation, from which immature germ cells can somehow be maturated. Autotransplantation of germ cells into the testis holds promise for fertility restoration, but contamination by malignant cells may induce relapse. Fluorescence-activated cell sorting (FACS) with two surface markers could exclude contaminated leukemic cells from murine germ cells, and transplantation of sorted germ cells successfully restored fertility without transmission of leukemia. Human germ cells could be also isolated from human leukemia and lymphoma cell lines by FACS using surface markers. Before autotransplantation can be applied clinically, some issues, including the risk of contamination by malignant cells and in vitro propagation of spermatogonial stem cells, should be resolved.

Molecular and functional analysis of the stem cell compartment of chronic myelogenous leukemia reveals the presence of a CD34- cell population with intrinsic resistance to imatinib

We show the molecular and functional characterization of a novel population of lineage-negative CD34-negative (Lin(-)CD34(-)) hematopoietic stem cells from chronic myelogenous leukemia (CML) patients at diagnosis. Molecular karyotyping and quantitative analysis of BCR-ABL transcript demonstrated that approximately one-third of CD34(-) cells are leukemic. CML Lin(-)CD34(-) cells showed kinetic quiescence and limited clonogenic capacity. However, stroma-dependent cultures induced CD34 expression on some cells and cell cycling, and increased clonogenic activity and expression of BCR-ABL transcript. Lin(-)CD34(-) cells showed hematopoietic cell engraftment rate in 2 immunodeficient mouse strains similar to Lin-CD34(+) cells, whereas endothelial cell engraftment was significantly higher. Gene expression profiling revealed the down-regulation of cell-cycle arrest genes and genes involved in antigen presentation and processing, while the expression of genes related to tumor progression, such as angiogenic factors, was strongly up-regulated compared with normal counterparts. Phenotypic analysis confirmed the significant down-regulation of HLA class I and II molecules in CML Lin(-)CD34(-) cells. Imatinib mesylate did not reduce fusion transcript levels, BCR-ABL kinase activity, and clonogenic efficiency of CML Lin(-)CD34(-) cells in vitro. Moreover, leukemic CD34(-) cells survived exposure to BCR-ABL inhibitors in vivo. Thus, we identified a novel CD34(-) leukemic stem cell subset in CML with peculiar molecular and functional characteristics.

Impaired antigen presentation in neoplasia: basic mechanisms and implications for acute myeloid leukemia

During onset, treatment and progression of acute myeloid leukemia (AML), inadequate immune responses against certain myeloid leukemic blasts might be associated with the occurrence of minimal residual disease and subsequent relapse. Several studies on this subject have demonstrated that, in general, solid tumor cells are able to avoid CD8+ cytotoxic T-cell recognition by downregulating HLA class I-restricted presentation of tumor-associated antigens. In tumor cells that can express HLA class II molecules, such as myeloid leukemic blasts, abnormalities in the processing pathways of endogenous antigens could also result in impaired HLA class II-restricted tumor-associated antigen presentation to CD4+ T helper cells. More insight into impaired tumor-associated antigen presentation by myeloid leukemic blasts could explain their escape from immune recognition and might be crucial for selecting appropriate strategies to improve whole-cell or dendritic cell-based tumor vaccine efficacy in the treatment of AML patients.

Isolation of germ cells from leukemia and lymphoma cells in a human in vitro model: potential clinical application for restoring human fertility after anticancer therapy

More than 70% of patients survive childhood cancer, but chemotherapy and radiation therapy may cause irreversible impairment of spermatogenesis. To treat infertility secondary to anticancer treatment for childhood cancer, we have developed a procedure to isolate germ cells from leukemic mice by fluorescence-activated cell sorting with two surface markers, and transplantation of isolated germ cells successfully restored fertility without inducing leukemia. In the present study, we analyzed human germ cells and human malignant cells, including five leukemia cell lines and three lymphoma cell lines, by fluorescence-activated cell sorting with antibodies against MHC class I and CD45. Testicular specimens were obtained from a patient who underwent surgery for testicular rupture. In the high forward scatter and low side scatter region, no malignant cells were found in the MHC class I-negative and CD45-negative fraction (the germ cell fraction), with the exception of K562 cells. A total of 39.2% of the germ cells were found in the germ cell fraction. A total of 1.45% of K562 cells were found in the germ cell fraction. Treatment with IFNgamma induced the expression of MHC class I on K562 cells but not on germ cells and made it possible to isolate germ cells from K562 cells. In conclusion, we isolated human germ cells from malignant cells with two surface markers after treatment with IFNgamma. Immunophenotyping for each patient will be necessary before isolation and induction of surface marker will be clinically applicable.

Down-regulation of locus-specific human lymphocyte antigen class I expression in Epstein-Barr virus-associated gastric cancer: implication for viral-induced immune evasion

BACKGROUND

To understand whether the association between Epstein-Barr Virus (EBV) and gastric cancer (GC) has any role in loss of surface expression of human lymphocyte antigen (HLA) class I, the authors analyzed locus-specific transcriptional expression of HLA-A, HLA-B, HLA-C, and HLA-E along with other HLA-associated molecules (beta2-microglobulin [beta2M], cellular latent membrane protein [LMP], and transporter associated with antigen presentation [TAP]) in EBV-associated, primary GC (EBVaGC) and EBV-negative GC (EBVnGC) tissues.

METHODS

Approximately 20 EBVaGC tissues and 40 EBVnGC tissues and their corresponding normal tissues were used in the study. The presence of EBV in GC was established by EBV-encoded small RNA in situ hybridization analysis and BamHI W polymerase chain reaction (PCR) analysis. Transcriptional expression of viral LMP2A and several HLA class I genes were analyzed by reverse transcriptase (RT)-PCR. Surface expression levels of HLA class I proteins in cancer samples along with their normal counterparts also were quantified by flow cytometry.

RESULTS

The RT-PCR data suggested selective down-regulation of the HLA-A/HLA-B locus along with over-expression of HLA-E transcripts in EBVaGC (P < .05). This was confirmed further by the flow-cytometric studies using antibodies to HLA-ABC and HLA-E. Among the accessory molecules, LMP7 transcript was down-regulated in a number of EBVaGC tissues compared with EBVnGC.

CONCLUSIONS

The current results suggested that the establishment of EBV latent infection in gastric tissues allows malignant cells to avoid the immune surveillance of both cytotoxic T-lymphocytes and natural killer cells by regulating the differential expression of HLA class I molecules.