Gene expression profiling identifies BAX-delta as a novel tumor antigen in acute lymphoblastic leukemia

Development of Cancer Immunotherapies

Cancer immunotherapy, or the utilization of components of the immune system to target and eliminate cancer, has become a highly active area of research in the past several decades and a common treatment strategy for several cancer types. The concept of harnessing the immune system for this purpose originated over 100 years ago when a physician by the name of William Coley successfully treated several of his cancer patients with a combination of live and attenuated bacteria, later known as "Coley's Toxins", after observing a subset of prior patients enter remission following their diagnosis with the common bacterial infection, erysipelas. However, it was not until late in the twentieth century that cancer immunotherapies were developed for widespread use, thereby transforming the treatment landscape of numerous cancer types. Pivotal studies elucidating molecular and cellular functions of immune cells, such as the discovery of IL-2 and production of monoclonal antibodies, fostered the development of novel techniques for studying the immune system and ultimately the development and approval of several cancer immunotherapies by the United States Food and Drug Association in the 1980s and 1990s, including the tuberculosis vaccine-Bacillus Calmette-Guérin, IL-2, and the CD20-targeting monoclonal antibody. Approval of the first therapeutic cancer vaccine, Sipuleucel-T, for the treatment of metastatic castration-resistant prostate cancer and the groundbreaking success and approval of immune checkpoint inhibitors and chimeric antigen receptor T cell therapy in the last decade, have driven an explosion of interest in and pursuit of novel cancer immunotherapy strategies. A broad range of modalities ranging from antibodies to adoptive T cell therapies is under investigation for the generalized treatment of a broad spectrum of cancers as well as personalized medicine. This chapter will focus on the recent advances, current strategies, and future outlook of immunotherapy development for the treatment of cancer.

Recent progress of palmitoyl transferase DHHC3 as a novel antitumor target

DHHC3 is a DHHC-family palmitoyl acyltransferase that is responsible for many mammalian palmitoylation events. By regulating the posttranslational modification of its specific substrates, DHHC3 has shown a strong protumor effect in various cancers. In this review, the authors introduce the research progress of DHHC3 as a new antitumor target through the expression of DHHC3 in patients with tumors, substrate proteins and potential mechanisms. Recent advances in the search for protein structures and inhibitors are also reviewed. Several design strategies to facilitate the optimization of the process of drug design based on DHHC3 are also discussed.

Unexpected suppression of tumorigenesis by c-MYC via TFAP4-dependent restriction of stemness in B lymphocytes

The proliferative burst of B lymphocytes is essential for antigen receptor repertoire diversification during the development and selective expansion of antigen-specific clones during immune responses. High proliferative activity inevitably promotes oncogenesis, the risk of which is further elevated in B lymphocytes by endogenous gene rearrangement and somatic mutations. However, B-cell-derived cancers are rare, perhaps owing to putative intrinsic tumor-suppressive mechanisms. We show that c-MYC facilitates B-cell proliferation as a protumorigenic driver and unexpectedly coengages counteracting tumor suppression through its downstream factor TFAP4. TFAP4 is mutated in human lymphoid malignancies, particularly in >10% of Burkitt lymphomas, and reduced TFAP4 expression was associated with poor survival of patients with MYC-high B-cell acute lymphoblastic leukemia. In mice, insufficient TFAP4 expression accelerated c-MYC-driven transformation of B cells. Mechanistically, c-MYC suppresses the stemness of developing B cells by inducing TFAP4 and restricting self-renewal of proliferating B cells. Thus, the pursuant transcription factor cascade functions as a tumor suppressor module that safeguards against the transformation of developing B cells.

Identification of immune subtypes of Ph-neg B-ALL with ferroptosis related genes and the potential implementation of Sorafenib

BACKGROUND

The clinical outcome of Philadelphia chromosome-negative B cell acute lymphoblastic leukemia (Ph-neg B-ALL) varies considerably from one person to another after clinical treatment due to lack of targeted therapies and leukemia's heterogeneity. Ferroptosis is a recently discovered programmed cell death strongly correlated with cancers. Nevertheless, few related studies have reported its significance in acute lymphoblastic leukemia.

METHODS

Herein, we collected clinical data of 80 Ph-neg B-ALL patients diagnosed in our center and performed RNA-seq with their initial bone marrow fluid samples. Throughout unsupervised machine learning K-means clustering with 24 ferroptosis related genes (FRGs), the clustered patients were parted into three variant risk groups and were performed with bioinformatics analysis.

RESULTS

As a result, we discovered significant heterogeneity of both immune microenvironment and genomic variance. Furthermore, the immune check point inhibitors response and potential implementation of Sorafenib in Ph-neg B-ALL was also analyzed in our cohort. Lastly, one prognostic model based on 8 FRGs was developed to evaluate the risk of Ph-neg B-ALL patients.

CONCLUSION

Jointly, our study proved the crucial role of ferroptosis in Ph-neg B-ALL and Sorafenib is likely to improve the survival of high-risk Ph-neg B-ALL patients.

CCR7 in Blood Cancers - Review of Its Pathophysiological Roles and the Potential as a Therapeutic Target

According to the classical paradigm, CCR7 is a homing chemokine receptor that grants normal lymphocytes access to secondary lymphoid tissues such as lymph nodes or spleen. As such, in most lymphoproliferative disorders, CCR7 expression correlates with nodal or spleen involvement. Nonetheless, recent evidence suggests that CCR7 is more than a facilitator of lymphatic spread of tumor cells. Here, we review published data to catalogue CCR7 expression across blood cancers and appraise which classical and novel roles are attributed to this receptor in the pathogenesis of specific hematologic neoplasms. We outline why novel therapeutic strategies targeting CCR7 might provide clinical benefits to patients with CCR7-positive hematopoietic tumors.

ASF1B Promotes Oncogenesis in Lung Adenocarcinoma and Other Cancer Types

Anti-silencing function 1B histone chaperone (ASF1B) is known to be an important modulator of oncogenic processes, yet its role in lung adenocarcinoma (LUAD) remains to be defined. In this study, an integrated assessment of The Cancer Genome Atlas (TCGA) and genotype-tissue expression (GTEx) datasets revealed the overexpression of ASF1B in all analyzed cancer types other than LAML. Genetic, epigenetic, microsatellite instability (MSI), and tumor mutational burden (TMB) analysis showed that ASF1B was regulated by single or multiple factors. Kaplan-Meier survival curves suggested that elevated ASF1B expression was associated with better or worse survival in a cancer type-dependent manner. The CIBERSORT algorithm was used to evaluate immune microenvironment composition, and distinct correlations between ASF1B expression and immune cell infiltration were evident when comparing tumor and normal tissue samples. Gene set enrichment analysis (GSEA) indicated that ASF1B was associated with proliferation- and immunity-related pathways. Knocking down ASF1B impaired the proliferation, affected cell cycle distribution, and induced cell apoptosis in LUAD cell lines. In contrast, ASF1B overexpression had no impact on the malignant characteristics of LUAD cells. At the mechanistic level, ASF1B served as an indirect regulator of DNA Polymerase Epsilon 3, Accessory Subunit (POLE3), CDC28 protein kinase regulatory subunit 1(CKS1B), Dihydrofolate reductase (DHFR), as established through proteomic profiling and Immunoprecipitation-Mass Spectrometry (IP-MS) analyses. Overall, these data suggested that ASF1B serves as a tumor promoter and potential target for cancer therapy and provided us with clues to better understand the importance of ASF1B in many types of cancer.

The Mad2-Binding Protein p31comet as a Potential Target for Human Cancer Therapy

The spindle assembly checkpoint (SAC) is a surveillance mechanism that prevents mitotic exit at the metaphase-to-anaphase transition until all chromosomes have established correct bipolar attachment to spindle microtubules. Activation of SAC relies on the assembly of the mitotic checkpoint complex (MCC), which requires conformational change from inactive open Mad2 (OMad2) to the active closed Mad2 (C-Mad2) at unattached kinetochores. The Mad2-binding protein p31^comet plays a key role in controlling timely mitotic exit by promoting SAC silencing, through preventing Mad2 activation and promoting MCC disassembly. Besides, increasing evidences highlight the p31^comet potential as target for cancer therapy. Here, we provide an updated overview of the functional significance of p31^comet in mitotic progression, and discuss the potential of deregulated expression of p31^comet in cancer and in therapeutic strategies.

Systematic Analysis of Spleen Tyrosine Kinase Expression and its Clinical Outcomes in Various Cancers

Background:

Spleen tyrosine kinase (SYK) is an important enzyme in the proliferation and differentiation of all hematopoietic tissues. Its role as a cancer driver is well documented in liquid tumors; however, cumulative evidence has suggested an opposite role in other tumor types.

Objectives:

To systematically assess the expression of SYK, its prognostic value and epigenetic status in different cancers using bioinformatics tools.

Methods:

In this bioinformatics study, Oncomine database and cBioPortal were used to study the SYK gene expression, Kaplan–Meier plotter to study its prognostic value and MethHC to assess the SYK gene methylation in various cancers.

Results:

From 542 unique analyses of the SYK gene, it was found to be overexpressed in bladder, breast and colon cancers but downregulated in leukemia, lymphoma and myeloma. Compared with normal tissues, breast and brain tumors showed an overexpression of the SYK gene, whereas lymphoma and leukemia had lower expression. The Kaplan–Meier survival analysis revealed that SYK expression in pancreatic, gastric, liver and lung patients were correlated with better overall survival. Using cBioPortal, prostate cancer was found to have the highest SYK gene mutation frequency, and the mean expression was highest in diffuse large B-cell lymphoma, acute myeloid leukemia and thymoma. Using the MethHC database, SYK promoter hypermethylation was found to be significantly higher in breast, renal, liver, lung, pancreatic, prostatic, skin and stomach cancers compared with the normal tissue (P < 0.005).

Conclusion:

The results of this study indicate the potential use of SYK as a diagnostic and therapeutic target for different type of cancers. However, further experimental data are required to validate these results before use of SYK in clinical settings.

HMGA Proteins in Hematological Malignancies

The high mobility group AT-Hook (HMGA) proteins are a family of nonhistone chromatin remodeling proteins known as "architectural transcriptional factors". By binding the minor groove of AT-rich DNA sequences, they interact with the transcription apparatus, altering the chromatin modeling and regulating gene expression by either enhancing or suppressing the binding of the more usual transcriptional activators and repressors, although they do not themselves have any transcriptional activity. Their involvement in both benign and malignant neoplasias is well-known and supported by a large volume of studies. In this review, we focus on the role of the HMGA proteins in hematological malignancies, exploring the mechanisms through which they enhance neoplastic transformation and how this knowledge could be exploited to devise tailored therapeutic strategies.

Integrated bioinformatics analysis of the crucial candidate genes and pathways associated with glucocorticoid resistance in acute lymphoblastic leukemia

Glucocorticoids (GC) are the foundation of the chemotherapy regimen in acute lymphoblastic leukemia (ALL). However, resistance to GC is observed more frequently than resistance to other chemotherapy agents in patients with ALL relapse. Moreover, the mechanism underlying the development of GC resistance in ALL has not yet been fully uncovered. In this study, we used bioinformatic analysis methods to integrate the candidate genes and pathways participating in GC resistance in ALL and subsequently verified the bioinformatics findings with in vitro cell experiments. Ninety‐nine significant common differentially expressed genes (DEGs) associated with GC resistance were determined by integrating two gene profile datasets, including GC‐sensitive and ‐resistant samples. Using Kyoto Encyclopedia of Genes and Genomes (KEGG) and REACTOME pathways analysis, the signaling pathways in which DEGs were significantly enriched were clustered. The GC resistance‐related biologically functional interactions were visualized as DEG‐associated Protein–Protein Interaction (PPI) network complexes, with 98 nodes and 127 edges. MYC, a node which displayed the highest connectivity in all edges, was highlighted as the core gene in the PPI network. Increased C‐MYC expression was observed in adriamycin‐resistant BALL‐1/ADR cells, which we demonstrated was also resistant to dexamethasone. These results outlined a panorama in which the solitary and scattered experimental results were integrated and expanded. The potential promising target of the candidate pathways and genes involved in GC resistance of ALL was concomitantly revealed.

Combination Therapy for Treating Advanced Drug-Resistant Acute Lymphoblastic Leukemia

Drug-resistant acute lymphoblastic leukemia (ALL) patients do not respond to standard chemotherapy, and an urgent need exists to develop new treatment strategies. Our study exploited the presence of B-cell activating factor receptor (BAFF-R) on the surface of drug-resistant B-ALL cells as a therapeutic target. We used anti-BAFF-R (VAY736), optimized for natural killer (NK) cell-mediated antibody-dependent cellular cytotoxicity (ADCC), to kill drug-resistant ALL cells. VAY736 antibody and NK cell treatments significantly decreased ALL disease burden and provided survival benefit in vivo However, if the disease was advanced, the ADCC efficacy of NK cells was inhibited by microenvironmental transforming growth factor-beta (TGFβ). Inhibiting TGFβ signaling in NK cells using the TGFβ receptor 1 (R1) inhibitor (EW-7197) significantly enhanced VAY736-induced NK cell-mediated ALL killing. Our results highlight the potential of using a combination of VAY736 antibody with EW-7197 to treat advance-stage, drug-resistant B-ALL patients.

Phosphatase of regenerating liver-3 is expressed in acute lymphoblastic leukemia and mediates leukemic cell adhesion, migration and drug resistance

Phosphatase of regenerating liver-3 (PRL-3/PTP4A3) is upregulated in multiple cancers, including BCR-ABL1- and ETV6-RUNX-positive acute lymphoblastic leukemia (ALL). With this study, we aim to characterize the biological role of PRL-3 in B cell ALL (B-ALL). Here, we demonstrate that PRL-3 expression at mRNA and protein level was higher in B-ALL cells than in normal cells, as measured by qRT-PCR or flow cytometry. Further, we demonstrate that inhibition of PRL-3 using shRNA or a small molecular inhibitor reduced cell migration towards an SDF-1α gradient in the preB-ALL cell lines Reh and MHH-CALL-4. Knockdown of PRL-3 also reduced cell adhesion towards fibronectin in Reh cells. Mechanistically, PRL-3 mediated SDF-1α stimulated calcium release, and activated focal adhesion kinase (FAK) and Src, important effectors of migration and adhesion. Finally, PRL-3 expression made Reh cells more resistance to cytarabine treatment. In conclusion, the expression level of PRL-3 was higher in B-ALL cells than in normal cells. PRL-3 promoted adhesion, migration and resistance to cytarabine. PRL-3 may represent a novel target in the treatment of B-ALL.

Cancer-type dependent expression of CK2 transcripts

A multitude of proteins are aberrantly expressed in cancer cells, including the oncogenic serine-threonine kinase CK2. In a previous report, we found increases in CK2 transcript expression that could explain the increased CK2 protein levels found in tumors from lung and bronchus, prostate, breast, colon and rectum, ovarian and pancreatic cancers. We also found that, contrary to the current notions about CK2, some CK2 transcripts were downregulated in several cancers. Here, we investigate all other cancers using Oncomine to determine whether they also display significant CK2 transcript dysregulation. As anticipated from our previous analysis, we found cancers with all CK2 transcripts upregulated (e.g. cervical), and cancers where there was a combination of upregulation and/or downregulation of the CK2 transcripts (e.g. sarcoma). Unexpectedly, we found some cancers with significant downregulation of all CK2 transcripts (e.g. testicular cancer). We also found that, in some cases, CK2 transcript levels were already dysregulated in benign lesions (e.g. Barrett’s esophagus). We also found that CK2 transcript upregulation correlated with lower patient survival in most cases where data was significant. However, there were two cancer types, glioblastoma and renal cell carcinoma, where CK2 transcript upregulation correlated with higher survival. Overall, these data show that the expression levels of CK2 genes is highly variable in cancers and can lead to different patient outcomes.

The functional domains for Bax∆2 aggregate-mediated caspase 8-dependent cell death

Bax∆2 is a functional pro-apoptotic Bax isoform having alterations in its N-terminus, but sharing the rest of its sequence with Baxα. Bax∆2 is unable to target mitochondria due to the loss of helix α1. Instead, it forms cytosolic aggregates and activates caspase 8. However, the functional domain(s) responsible for BaxΔ2 behavior have remained elusive. Here we show that disruption of helix α1 makes Baxα mimic the behavior of Bax∆2. However, the other alterations in the Bax∆2 N-terminus have no significant impact on aggregation or cell death. We found that the hallmark BH3 domain is necessary but not sufficient for aggregation-mediated cell death. We also noted that the core region shared by Baxα and Bax∆2 is required for the formation of large aggregates, which is essential for BaxΔ2 cytotoxicity. However, aggregation by itself is unable to trigger cell death without the C-terminus. Interestingly, the C-terminal helical conformation, not its primary sequence, appears to be critical for caspase 8 recruitment and activation. As Bax∆2 shares core and C-terminal sequences with most Bax isoforms, our results not only reveal a structural basis for Bax∆2-induced cell death, but also imply an intrinsic potential for aggregate-mediated caspase 8-dependent cell death in other Bax family members.

Redefining the BH3 Death Domain as a 'Short Linear Motif'

B cell lymphoma-2 (BCL-2)-related proteins control programmed cell death through a complex network of protein–protein interactions mediated by BCL-2 homology 3 (BH3) domains. Given their roles as dynamic linchpins, the discovery of novel BH3-containing proteins has attracted considerable attention. However, without a clearly defined BH3 signature sequence the BCL-2 family has expanded to include a nebulous group of nonhomologous BH3-only proteins, now justified by an intriguing twist. We present evidence that BH3s from both ordered and disordered proteins represent a new class of short linear motifs (SLiMs) or molecular recognition features (MoRFs) and are diverse in their evolutionary histories. The implied corollaries are that BH3s have a broad phylogenetic distribution and could potentially bind to non-BCL-2-like structural domains with distinct functions.

BCL-2 family interactions are mediated by evolutionarily diverse BH3 motifs to regulate apoptosis. Given their key roles, BH3 mimetics are in clinical trials as cancer therapies.

The discovery of novel BH3-only proteins represents a major endeavor in the cell death field. As a result, BH3 motifs are reportedly present in a nebulous conglomerate of different proteins, both structured and intrinsically disordered.

There is no rigorous definition of a BH3 motif. Currently available BH3 signatures are diverse and elusive for predicting new functional BH3-containing proteins.

Redefining the BH3 motif as a new type of short linear motif (SLiM) or molecular recognition feature (MoRF) reconciles many puzzling features of this motif and opens up new avenues for research.

Identifying new targets in leukemogenesis using computational approaches

There is a need to identify novel targets in Acute Lymphoblastic Leukemia (ALL), a hematopoietic cancer affecting children, to improve our understanding of disease biology and that can be used for developing new therapeutics. Hence, the aim of our study was to find new genes as targets using in silico studies; for this we retrieved the top 10% overexpressed genes from Oncomine public domain microarray expression database; 530 overexpressed genes were short-listed from Oncomine database. Then, using prioritization tools such as ENDEAVOUR, DIR and TOPPGene online tools, we found fifty-four genes common to the three prioritization tools which formed our candidate leukemogenic genes for this study. As per the protocol we selected thirty training genes from PubMed. The prioritized and training genes were then used to construct STRING functional association network, which was further analyzed using cytoHubba hub analysis tool to investigate new genes which could form drug targets in leukemia. Analysis of the STRING protein network built from these prioritized and training genes led to identification of two hub genes, SMAD2 and CDK9, which were not implicated in leukemogenesis earlier. Filtering out from several hundred genes in the network we also found MEN1, HDAC1 and LCK genes, which re-emphasized the important role of these genes in leukemogenesis. This is the first report on these five additional signature genes in leukemogenesis. We propose these as new targets for developing novel therapeutics and also as biomarkers in leukemogenesis, which could be important for prognosis and diagnosis.

Regulation of RAB5C is important for the growth inhibitory effects of MiR-509 in human precursor-B acute lymphoblastic leukemia

MicroRNAs (miRs) regulate essentially all cellular processes, but few miRs are known to inhibit growth of precursor-B acute lymphoblastic leukemias (B-ALLs). We identified miR-509 via a human genome-wide gain-of-function screen for miRs that inhibit growth of the NALM6 human B-ALL cell line. MiR-509-mediated inhibition of NALM6 growth was confirmed by 3 independent assays. Enforced miR-509 expression inhibited 2 of 2 additional B-ALL cell lines tested, but not 3 non-B-ALL leukemia cell lines. MiR-509-transduced NALM6 cells had reduced numbers of actively proliferating cells and increased numbers of cells undergoing apoptosis. Using miR target prediction algorithms and a filtering strategy, RAB5C was predicted as a potentially relevant target of miR-509. Enforced miR-509 expression in NALM6 cells reduced RAB5C mRNA and protein levels, and RAB5C was demonstrated to be a direct target of miR-509. Knockdown of RAB5C in NALM6 cells recapitulated the growth inhibitory effects of miR-509. Co-expression of the RAB5C open reading frame without its 3' untranslated region (3'UTR) blocked the growth-inhibitory effect mediated by miR-509. These findings establish RAB5C as a target of miR-509 and an important regulator of B-ALL cell growth with potential as a therapeutic target.

Evaluation of Bax and Bak gene mutations and expression in breast cancer

Genetic analyses have provided evidence to suggest that Bax and Bak are the essential genes for apoptosis in mammalians cells. This study aimed to search for biomarkers in breast cancer to be used as prognostic markers for the disease. The Bak and Bax genes expressions were analyzed in 23 breast cancer patients by RT-PCR technique. SSCP technique was used to detect the mobility of the abnormal fragment in Bak exon 4. PCR for Bax promoter was digested with Tau 1 restriction enzyme to identify a single polymorphism G(-248)A. The expression of Bak gene is related to several clinical factors of breast cancer. The analysis of Bax RNA showed 4 isoforms of Bax with different distributions in the normal and tumor tissues. These isoforms were Bax α, d, δ, and ζ. Exon 4 had a normal pattern in all cases of breast cancer. There was a statistically significant difference in the frequency distribution of the G(-248)A genotypes in the breast cancer tissues with grade 3+high, T2 stage, lobular +other, and PR −ve subgroups. In this study, Bak expression seems to lead to development of breast cancer and affects the disease progression. Also, Bax d and Bax δ could be used as risk factor and biomarker for breast cancer with the distribution of G284A.

Patterns of TPD52 overexpression in multiple human solid tumor types analyzed by quantitative PCR

Tumor protein D52 (TPD52) is located at chromosome 8q21, a region that is frequently gained or amplified in multiple human cancer types. TPD52 has been suggested as a potential target for new anticancer therapies. In order to analyze TPD52 expression in the most prevalent human cancer types, we employed quantitative PCR to measure TPD52 mRNA levels in formalin-fixed tissue samples from more than 900 cancer tissues obtained from 29 different human cancer types. TPD52 was expressed at varying levels in all tested normal tissues, including skin, lymph node, lung, oral mucosa, breast, endometrium, ovary, vulva, myometrium, liver, pancreas, stomach, kidney, prostate, testis, urinary bladder, thyroid gland, brain, muscle and fat tissue. TPD52 was upregulated in 18/29 (62%) tested cancer types. Strongest expression was found in non-seminoma (56-fold overexpression compared to corresponding normal tissue), seminoma (42-fold), ductal (28-fold) and lobular breast cancer (14-fold). In these tumor types, TPD52 upregulation was found in the vast majority (>80%) of tested samples. Downregulation was found in 11 (38%) tumor types, most strongly in papillary renal cell cancer (-8-fold), leiomyosarcoma (-6-fold), clear cell renal cell cancer (-5-fold), liposarcoma (-5-fold) and lung cancer (-4-fold). These results demonstrate that TPD52 is frequently and strongly upregulated in many human cancer types, which may represent candidate tumor types for potential anti-TPD52 therapies.

Impaired OXPHOS complex III in breast cancer

We measured the mitochondrial oxidative phosphorylation (mtOXPHOS) activities of all five complexes and determined the activity and gene expression in detail of the Complex III subunits in human breast cancer cell lines and primary tumors. Our analysis revealed dramatic differences in activity of complex III between normal and aggressive metastatic breast cancer cell lines. Determination of Complex III subunit gene expression identified over expression and co-regulation of UQCRFS1 (encoding RISP protein) and UQCRH (encoding Hinge protein) in 6 out of 9 human breast tumors. Analyses of UQCRFS1/RISP expression in additional matched normal and breast tumors demonstrated an over expression in 14 out of 40 (35%) breast tumors. UQCRFS1/RISP knockdown in breast tumor cell line led to decreased mitochondrial membrane potential as well as a decrease in matrigel invasion. Furthermore, reduced matrigel invasion was mediated by reduced ROS levels coinciding with decreased expression of NADPH oxidase 2, 3, 4 and 5 involved in ROS production. These studies provide direct evidence for contribution of impaired mtOXPHOS Complex III to breast tumorigenesis.

A novel tumor antigen derived from enhanced degradation of bax protein in human cancers

Cancer cells frequently exhibit defects in apoptosis, which contribute to increased survival and chemotherapeutic resistance. For example, genetic mutations or abnormal proteasomal degradation can reduce expression of Bax which limits apoptosis. In cancers where abnormal proteasomal degradation of Bax occurs, we hypothesized that Bax peptides that bind to human leukocyte antigen (HLA) class I molecules would be generated for presentation to CD8(+) T cells. To test this hypothesis, we generated T cells against pooled Bax peptides, using the blood of healthy human donors. Although T-cell responses were of low frequency (0.15%), a CD8(+) T-cell clone (KSIVB17) was isolated that optimally recognized Bax(136-144) peptide (IMGWTLDFL) presented by HLA-A*0201. KSIVB17 was able to recognize and kill a variety of HLA-matched cancer cells including primary tumor cells from chronic lymphocytic leukemia (CLL). No reactivity was seen against HLA-matched, nontransformed cells such as PHA blasts and skin fibroblasts. Furthermore, KSIVB17 reactivity corresponded with the proteasomal degradation patterns of Bax protein observed in cancer cells. Taken together, our findings suggest a new concept for tumor antigens based on regulatory proteins that are ubiquitously expressed in normal cells, but that have abnormally enhanced degradation in cancer cells. Bax degradation products offer candidate immune antigens in cancers such as CLL in which increased Bax degradation correlates with poor clinical prognosis.

ATMIN is required for maintenance of genomic stability and suppression of B cell lymphoma

Defective V(D)J rearrangement of immunoglobulin heavy or light chain (IgH or IgL) or class switch recombination (CSR) can initiate chromosomal translocations. The DNA-damage kinase ATM is required for the suppression of chromosomal translocations but ATM regulation is incompletely understood. Here, we show that mice lacking the ATM cofactor ATMIN in B cells (ATMIN(ΔB/ΔB)) have impaired ATM signaling and develop B cell lymphomas. Notably, ATMIN(ΔB/ΔB) cells exhibited defective peripheral V(D)J rearrangement and CSR, resulting in translocations involving the Igh and Igl loci, indicating that ATMIN is required for efficient repair of DNA breaks generated during somatic recombination. Thus, our results identify a role for ATMIN in regulating the maintenance of genomic stability and tumor suppression in B cells.

Promotion and maintenance of leukemia by ERG

The Ets-related gene (ERG) located on human chromosome 21 encodes a transcription factor and is thought to be causally related to Down syndrome-associated acute megakaryocytic leukemia in childhood. In clinical adult leukemia, however, increased expression of ERG is indicative of poor prognosis in T-cell acute lymphoblastic leukemia and cytogenetically normal acute myeloid leukemia, although the involvement of ERG in the development of adult leukemia remains elusive. Here, we show that forced expression of ERG in adult BM cells alters differentiation and induces expansion of T and erythroid cells and increases frequencies of myeloid progenitors in mouse BM transplantation models. The expanded T cells then develop T-cell acute lymphoblastic leukemia after acquisition of mutations in the Notch1 gene. Targeted expression of ERG into B cells also altered differentiation and promoted growth of precursor B cells. Overall, these findings suggest a general role of ERG in promoting growth of adult hematopoietic cells in various lineages. In line with this, shRNA-mediated silencing of ERG expression attenuated growth of human leukemia cell lines of various lineages. Thus, ERG is capable of promoting the development of leukemia and is crucial for its maintenance.

XIAP expression is post-transcriptionally upregulated in childhood ALL and is associated with glucocorticoid response in T-cell ALL

BACKGROUND

Resistance to glucocorticoid induced apoptosis is one of the major risk factors for relapse and poor outcome in childhood acute lymphoblastic leukemia (ALL). Overexpression of X-linked inhibitor of apoptosis protein (XIAP) has been shown to be associated with chemotherapy resistance in several malignancies.

PROCEDURE

XIAP protein and mRNA expression were determined in leukemic blasts of 51 childhood ALL patients and normal bone marrow mononuclear cells. XIAP expression was correlated with glucocorticoid response and outcome.

RESULTS

XIAP protein but not mRNA expression was found to be highly increased in childhood ALL compared to control bone marrow mononuclear cells (MNC) (median: 3.5 vs. 0.14 ng/10(5) MNC, P < 0.0001) indicating a post-transcriptional regulation of XIAP expression. In patients with T-cell ALL, poor prednisone response was associated with increased XIAP expression (median: 2.8 in good vs. 5.8 in poor responders; P = 0.005). Similarly, T-cell ALL patients suffering adverse events showed higher initial XIAP levels than patients in continuous complete remission (CCR) (median: 2.7 in patients in CCR vs. 5.6 in patients suffering adverse events; P = 0.007). XIAP inhibition using the low-molecular-weight SMAC mimetic LBW242 resulted in a significant increase of prednisone-induced apoptosis in vitro.

CONCLUSION

In childhood ALL compared to control bone marrow, the expression of the apoptosis inhibitor XIAP is highly increased by post-transcriptional regulation. The association with poor in vivo glucocorticoid response and outcome in T-cell ALL suggests XIAP inhibition as a promising novel approach for the treatment of resistant ALL.

STAT3 is a substrate of SYK tyrosine kinase in B-lineage leukemia/lymphoma cells exposed to oxidative stress

We provide unprecedented genetic and biochemical evidence that the antiapoptotic transcription factor STAT3 serves as a substrate for SYK tyrosine kinase both in vitro and in vivo. Induction of SYK in an ecdysone-inducible mammalian expression system results in STAT3 activation, as documented by tyrosine phosphorylation and nuclear translocation of STAT3, as well as amplified expression of several STAT3 target genes. STAT3 activation after oxidative stress (OS) is strongly diminished in DT40 chicken B-lineage lymphoma cells rendered SYK-deficient by targeted disruption of the syk gene. Introduction of a wild-type, C-terminal or N-terminal SH2 domain-mutated, but not a kinase domain-mutated, syk gene into SYK-deficient DT40 cells restores OS-induced enhancement of STAT-3 activity. Thus, SYK plays an important and indispensable role in OS-induced STAT3 activation and its catalytic SH1 domain is critical for this previously unknown regulatory function. These results provide evidence for the existence of a novel mode of cytokine-independent cross-talk that operates between SYK and STAT3 pathways and regulates apoptosis during OS. We further provide experimental evidence that SYK is capable of associating with and phosphorylating STAT3 in human B-lineage leukemia/lymphoma cells challenged with OS. In agreement with a prerequisite role of SYK in OS-induced STAT3 activation, OS does not induce tyrosine phosphorylation of STAT3 in SYK-deficient human proB leukemia cells. Notably, inhibition of SYK with a small molecule drug candidate prevents OS-induced activation of STAT3 and overcomes the resistance of human B-lineage leukemia/lymphoma cells to OS-induced apoptosis.

Immunotherapy in acute leukemia

Recent advances in immunotherapy of cancer may represent a successful example in translational research, in which progress in knowledge and technology in immunology has led to new strategies of immunotherapy, and even past failures in many clinical trials have led to a better understanding of basic cancer immunobiology. This article reviews the latest concepts in antitumor immunology and its application in the treatment of cancer, with particular focus on acute leukemia.

High expression of connective tissue growth factor in pre-B acute lymphoblastic leukaemia

In recent years microarrays have been used extensively to characterize gene expression in acute lymphoblastic leukaemia (ALL). Few studies, however, have analysed normal haematopoietic cell populations to identify altered gene expression in ALL. We used oligonucleotide microarrays to compare the gene expression profile of paediatric precursor-B (pre-B) ALL specimens with two control cell populations, normal CD34(+) and CD19(+)IgM(-) cells, to focus on genes linked to leukemogenesis. A set of eight genes was identified with a ninefold higher average expression in ALL specimens compared with control cells. All of these genes were significantly deregulated in an independent cohort of 101 ALL specimens. One gene, connective tissue growth factor (CTGF, also known as CCN2), had exceptionally high expression, which was confirmed in three independent leukaemia studies. Further analysis of CTGF expression in ALL revealed exclusive expression in B-lineage, not T-lineage, ALL. Within B-lineage ALL approximately 75% of specimens were consistently positive for CTGF expression, however, specimens containing the E2A-PBX1 translocation showed low or no expression. Protein studies using Western blot analysis demonstrated the presence of CTGF in ALL cell-conditioned media. These findings indicate that CTGF is secreted by pre-B ALL cells and may play a role in the pathophysiology of this disease.