Deletions of IKZF1 and SPRED1 are associated with poor prognosis in a population-based series of pediatric B-cell precursor acute lymphoblastic leukemia diagnosed between 1992 and 2011.

Despite the favorable prognosis of childhood acute lymphoblastic leukemia (ALL), a substantial subset of patients relapses. Since this occurs not only in the high risk but also in the standard/intermediate groups, the presently used risk stratification is suboptimal. The underlying mechanisms for treatment failure include presence of genetic changes causing insensitivity to the therapy administered. To identify relapse-associated aberrations we performed single nucleotide polymorphism array analyses of 307 uniformly treated, consecutive pediatric ALL cases accrued 1992-2011. Recurrent aberrations of 14 genes in patients who subsequently relapsed or had induction failure were detected. Of these, deletions/uniparental isodisomies of ADD3, ATP10A, EBF1, IKZF1, PAN3, RAG1, SPRED1, and TBL1XR1 were significantly more common in B-cell precursor ALL patients who relapsed compared with those remaining in complete remission. In univariate analyses, age (10 years), WBC counts (>100 × 109/l), t(9;22)(q34;q11), MLL rearrangements, near-haploidy, and deletions of ATP10A, IKZF1, SPRED1, and the pseudoautosomal 1 regions on Xp/Yp were significantly associated with decreased 10-year event-free survival, with IKZF1 abnormalities being an independent risk factor in multivariate analysis irrespective of risk group. High age and deletions of IKZF1 and SPRED1 were also associated with poor overall survival. Thus, analyses of these genes provide clinically important information.Leukemia accepted article preview online, 4 July 2013; doi:10.1038/leu.2013.206

Clonal Evolution through Loss of Chromosomes and Subsequent Polyploidization in Chondrosarcoma

Near-haploid chromosome numbers have been found in less than 1% of cytogenetically reported tumors, but seem to be more common in certain neoplasms including the malignant cartilage-producing tumor chondrosarcoma. By a literature survey of published karyotypes from chondrosarcomas we could confirm that loss of chromosomes resulting in hyperhaploid-hypodiploid cells is common and that these cells may polyploidize. Sixteen chondrosarcomas were investigated by single nucleotide polymorphism (SNP) array and the majority displayed SNP patterns indicative of a hyperhaploid-hypodiploid origin, with or without subsequent polyploidization. Except for chromosomes 5, 7, 19, 20 and 21, autosomal loss of heterozygosity was commonly found, resulting from chromosome loss and subsequent duplication of monosomic chromosomes giving rise to uniparental disomy. Additional gains, losses and rearrangements of genetic material, and even repeated rounds of polyploidization, may affect chondrosarcoma cells resulting in highly complex karyotypes. Loss of chromosomes and subsequent polyploidization was not restricted to a particular chondrosarcoma subtype and, although commonly found in chondrosarcoma, binucleated cells did not seem to be involved in these events

The quality control of MHC class I antigen presentation

Major histocompatibility complex (MHC) class I molecules present antigenic peptides to CD8+ T cells. The peptides are generated by proteasomes in the cytosol, then translocated across the membrane of the endoplasmic reticulum (ER) by the transporter associated with antigen processing (TAP). Only properly assembled class I molecules loaded with high affinity peptides reach the cell surface. The maturation process is performed in a sequential mode where the chaperones BiP and calnexin sequentially control the folding of the MHC class I. Dimerised MHC class I then associate with the loading complex (paper I). An essential component of the loading complex is the trimeric complex consisting of TAP1, TAP2, and tapasin as shown in paper II. Due to its ability to interact with TAP and MHC class I, tapasin is a central component in the assembly of MHC class I. Efficient peptide binding by TAP prior to translocation across the ER membrane requires the presence of tapasin (paper III). Once in the ER, the assembly of tapasin-associated MHC class I with peptide depends on the presence of TAP transported peptides (paper IV). The transport of stably loaded class I molecules to the cell surface goes through the secretory route. Tapasin interacts specifically with COPI vesicles, possibly allowing recycling of unstable class I molecules from the Golgi back to the ER (paper V)

Chaperones and folding of MHC class I molecules in the endoplasmic reticulum.

In this review we discuss the influence of chaperones on the general phenomena of folding as well as on the specific folding of an individual protein, MHC class I. MHC class I maturation is a highly sophisticated process in which the folding machinery of the endoplasmic reticulum (ER) is heavily involved. Understanding the MHC class I maturation per se is important since peptides loaded onto MHC class I molecules are the base for antigen presentation generating immune responses against virus, intracellular bacteria as well as tumours. This review discusses the early stages of MHC class I maturation regarding BiP and calnexin association, and differences in MHC class I heavy chain (HC) interaction with calnexin and calreticulin are highlighted. Late stage MHC class I maturation with focus on the dedicated chaperone tapasin is also discussed. (C) 2003 Elsevier Science B.V. All rights reserved

HLA-I Antigen Presentation and Tapasin Influence Immune Responses Against Malignant Brain Tumors - Considerations for Successful Immunotherapy.

Human leukocyte antigen class I (HLA-I) presents antigenic peptides to cytotoxic CD8+ T cells (CTLs). This is a pivotal step in the generation of CTL responses. Both the quantity and quality of peptide-HLA-I (pHLA-I) complexes are crucial for CTL responses, but the level of HLA-I expression per se is also directly involved in dictating NK-cell responses. Antigen processing machinery (APM) proteins are involved in the maturation of HLA-I and in the selection of which peptides are - or are not - presented. Thus, these proteins are key players in shaping the immune response to cells in health and disease. In this review, we recap the most important features of APM components and their synergistic work to assure proper pHLA-I cell surface expression. We pay special attention to the HLA-I dedicated multifunctional protein, tapasin, and in relation to the different tapasin-dependency of HLA-I allomorphs we also discuss allomorph specific traits in maturation, structure and linkage to malignant diseases and brain tumors in particular. We next discuss the possibilities of restoring or manipulating the immune responses against brain tumors. In this context we discuss IFNγ therapy, cytostatics and irradiation. Finally, we integrate current views and knowledge to set the direction for future emphasis in the area of immunotherapy against brain tumors

Tapasin and human leukocyte antigen class I dysregulation correlates with survival in glioblastoma multiforme.

Human leukocyte antigen class I (HLA-I) molecules present antigenic peptides to cytotoxic CD8(+) T cells. Downregulation of peptide:HLA-I complexes is common in tumors and results in tumor immune escape variants. Also molecules involved in the maturation of HLA-I have been demonstrated to be dysregulated in malignant neoplasms. We here set out to investigate the antigen presentation capabilities of a set of 12 glioblastoma multiforme (GBM) tumors based on the expression of HLA-I. Moreover, we analyzed the expression of tapasin, a protein dedicated and essential to HLA-I maturation, as well as the infiltration of CD8+ cells using immunohistochemistry on paraffin-embedded sections. Comparison of different GBMs showed a variation in expression of both HLA-I heavy chain (HC) and tapasin. Interestingly, the expression of tapasin and HLA-I HC correlated significantly (p=0.0002) suggesting tapasin to be a key factor for efficient HLA-I antigen presentation in GBMs. Although no statistically significant correlation between CD8(+) cells and survival was found, probably due to a very low number of infiltrating CD8(+) cells at the time of surgical resection, both tapasin and HLA-I HC levels significantly correlated with survival. We suggest that analysis of expression of tapasin and/or HLA-I may be of value as prognostic tool for GBM patients, especially when considering immunotherapy

Stability of peptide-HLA-I complexes and tapasin folding facilitation - tools to define immunogenic peptides

Only a small fraction of the peptides generated inside the cell end up being presented by HLA-I on the cell surface. High stability of peptide-HLA-I complexes and a low HLA-I tapasin-facilitation have been proposed to predict immunogenicity. We here set out to investigate if these parameters correlated and defined immunogenic peptides. Both peptide-HLA-B*08:01 and peptide-HLA-A*02:01 complexes showed small differences in tapasin-facilitation and larger differences in stability. This suggests that the stability of immunogenic peptide-HLA-I complexes vary above an HLA-I allomorph dependent lower limit (e. g. > 2 h for HLA-A*02:01), immunogenicity predicted by tapasin-facilitation may be defined by an equally allomorph unique upper value (e. g. tapasin-facilitation <1.5 for HLA-A*02:01), and variation above the stability-threshold does not directly reflect a variation in tapasin-facilitation. (C) 2012 Federation of European Biochemical Societies. Published by Elsevier B. V. All rights reserved