Proteins In Acute Lymphoblastic Leukemia Research Articles

A Comprehensive Analysis of the Expression Profiles of KCTD Proteins in Acute Lymphoblastic Leukemia: Evidence of Selective Expression of KCTD1 in T-ALL.

Acute leukemia is the most common pediatric cancer. In most cases, this disease results from the malignant transformation of either the B-cell (B-ALL) or, less frequently, T-cell progenitors (T-ALL). Recently, a marked overexpression of KCTD15, a member of the emerging class of the potassium (K) channel tetramerization domain-containing proteins (KCTDs) has been detected in both patients and continuous cell lines as in vitro model systems. Because there is growing evidence of the key, yet diversified, roles played by KCTDs in cancers, we here report an exhaustive analysis of their expression profiles in both B-ALL and T-ALL patients. Although for most KCTDs, no significant alterations were found in these pathological states, for some members of the family, significant up- and down-regulations were detected in comparison with the values found in healthy subjects in the transcriptome analysis. Among these, particularly relevant is the upregulation of the closely related KCTD1 and KCTD15 in T-ALL patients. Interestingly, KCTD1 is barely expressed in both unaffected controls and B-ALL patients. Therefore, not only does this analysis represent the first study in which the dysregulation of all KCTDs is simultaneously evaluated in specific pathological contexts, but it also provides a promising T-ALL biomarker that could be suitable for clinical applications.

Synergistic activity of combined inhibition of anti-apoptotic molecules in B-cell precursor ALL

Targeting BCL-2, a key regulator of survival in B-cell malignancies including precursor B-cell acute lymphoblastic leukemia, has become a promising treatment strategy. However, given the redundancy of anti-apoptotic BCL-2 family proteins (BCL-2, BCL-XL, MCL-1), single targeting may not be sufficient. When analyzing the effects of BH3-mimetics selectively targeting BCL-XL and MCL-1 alone or in combination with the BCL-2 inhibitor venetoclax, heterogeneous sensitivity to either of these inhibitors was found in ALL cell lines and in patient-derived xenografts. Interestingly, some venetoclax-resistant leukemias were sensitive to the MCL-1-selective antagonist S63845 and/or BCL-XL-selective A-1331852 suggesting functional mutual substitution. Consequently, co-inhibition of BCL-2 and MCL-1 or BCL-XL resulted in synergistic apoptosis induction. Functional analysis by BH3-profiling and analysis of protein complexes revealed that venetoclax-treated ALL cells are dependent on MCL-1 and BCL-XL, indicating that MCL-1 or BCL-XL provide an Achilles heel in BCL-2-inhibited cells. The effect of combining BCL-2 and MCL-1 inhibition by venetoclax and S63845 was evaluated in vivo and strongly enhanced anti-leukemia activity was found in a pre-clinical patient-derived xenograft model. Our study offers in-depth molecular analysis of mutual substitution of BCL-2 family proteins in acute lymphoblastic leukemia and provides targets for combination treatment in vivo and in ongoing clinical studies.

Neoantigens in Hematologic Malignancies.

T cell cancer neoantigens are created from peptides derived from cancer-specific aberrant proteins, such as mutated and fusion proteins, presented in complex with human leukocyte antigens on the cancer cell surface. Because expression of the aberrant target protein is exclusive to malignant cells, immunotherapy directed against neoantigens should avoid “on-target, off-tumor” toxicity. The efficacy of neoantigen vaccines in melanoma and glioblastoma and of adoptive transfer of neoantigen-specific T cells in epithelial tumors indicates that neoantigens are valid therapeutic targets. Improvements in sequencing technology and innovations in antigen discovery approaches have facilitated the identification of neoantigens. In comparison to many solid tumors, hematologic malignancies have few mutations and thus fewer potential neoantigens. Despite this, neoantigens have been identified in a wide variety of hematologic malignancies. These include mutated nucleophosmin1 and PML-RARA in acute myeloid leukemia, ETV6-RUNX1 fusions and other mutated proteins in acute lymphoblastic leukemia, BCR-ABL1 fusions in chronic myeloid leukemia, driver mutations in myeloproliferative neoplasms, immunoglobulins in lymphomas, and proteins derived from patient-specific mutations in chronic lymphoid leukemias. We will review advances in the field of neoantigen discovery, describe the spectrum of identified neoantigens in hematologic malignancies, and discuss the potential of these neoantigens for clinical translation.

Abstract 2503: Differential expression of cytoskeletal proteins in acute lymphoblastic leukemia in accordance with initial response to chemotherapy

Abstract Precursor B lymphoblastic leukemia is a B-cell lineage neoplasm of lymphoblasts. The initial response to induction-chemotherapy is the most important prognostic factor in acute lymphoblastic leukemia (ALL) patients. Patients with rapid-early-response (RER, below 5% of blast in bone marrow at day-7 after induction-chemotherapy) have better event-free survival compared to slow-early-responders (SER, above 25% of blast). The drug sensitivity/resistance of leukemic blasts is mainly determined by specific genetic abnormalities, however, in more than 20% of ALL, the abnormalities remain unclassified, and the treatment outcome persist variable. This study aimed to find plausible biomarkers of drug sensitivity/resistance in ALL using proteomic analysis. We identified 28 up-regulated and 25 down-regulated proteins in SER_as compared to RER_by MALDI-TOF and mass spectrometry. Of these, 14-3-3 isoforms and cytoskeletal proteins were differentially expressed. Alpha tubulin and 14-3-3 gamma, down-regulated in RER were further verified by Western blot analysis. In further studies, the roles of these proteins in drug sensitivity/resistance are undergoing to elucidate as a potential biomarker for ALL therapy. Citation Format: Kee R. Kang, Eun Sil Park. Differential expression of cytoskeletal proteins in acute lymphoblastic leukemia in accordance with initial response to chemotherapy. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 2503. doi:10.1158/1538-7445.AM2014-2503

IN SILICO EVIDENCE OF SIGNALING PATHWAYS OF NOTCH MEDIATED NETWORKS IN LEUKEMIA

Notch signaling plays a critical role in cell fate determination and maintenance of progenitors in many developmental systems. Notch receptors have been shown to be expressed on hematopoietic progenitor cells as well as to various degrees in peripheral blood T and B lymphocytes, monocytes, and neutrophils. Our aim was to understand the protein interaction network, using Notch1 protein name as query in STRING database and we generated a model to assess the significance of Notch1 associated proteins in Acute Lymphoblastic Leukemia (ALL). We further analyzed the expression levels of the genes encoding hub proteins, using Oncomine database, to determine their significance in leukemogenesis. Of the forty two hub genes, we observed that sixteen genes were underexpressed and eleven genes were overexpressed in T-cell Acute Lymphoblastic samples in comparison to their expression levels in normal cells. Of these, we found three novel genes which have not been reported earlier- KAT2B, PSEN1 (underexpressed) and CDH2 (overexpressed). These three identified genes may provide new insights into the abnormal hematopoietic process observed in Leukemia as these genes are involved in Notch signaling and cell adhesion processes. It is evident that experimental validation of the protein interactors in leukemic cells could help in the identification of new diagnostic markers for leukemia.

Cyclic-AMP Responsive Element Binding Protein 1 (CREB) As a New Potential Druggable Target in Pediatric Acute Lymphoblastic Leukemia

Abstract 1368New treatment options are necessary to improve survival rates for patients with Acute Lymphoblastic Leukemia (ALL), especially for patients with unfavorable prognostic predictors. As a new therapeutic approach specific protein kinase inhibitors are being developed that can down-regulate vital signaling pathways in leukemic blasts (McCubrey et al, 2008). The main goal of the present study is to obtain a better understanding of the kinase signaling pathways active in ALL cells and to identify potential targets for therapeutic intervention, To identify active signaling pathways in ALL we have used kinase activity arrays containing 1024 peptides representing all major signaling pathways and human proteome profiler arrays containing 46 phospho-antibodies on lysates of primary ALL blasts. In 20 patient samples a total of 10.6% 109(1024) peptides were found to be phosphorylated in 90% of the samples. About 46% 50(109). Activities for kinases including PKC, PKA, Akt, CAMK2, CDC2, CDK2, ERK, GSK3beta, JAK and MAPK were detected in these lysates. The human proteome profiler array demonstrated high levels of protein phosphorylation of CREB and RSK. We constructed a provisional signal transduction scheme of active kinases and phosphorylated proteins in ALL cells (Fig. 1A). Consistent with earlier reports, we identified a prominent role for the Raf/MEK/ERK and the PI3K/Akt/mTOR pathways in these ALL cells. Based on this provisional signal transduction scheme we composed a list of possible new druggable targets. Two proteins were selected for further investigation, CREB and RSK. Inhibition of RSK by the p90 RSK inhibitor BI-D1870 had no effect on cell viability as measured with WST-1 cell viability assay in ALL cell lines. Interestingly, inhibition of CREB by the CREB inhibitor KG-501 showed a dose- and time-dependent decrease in cell viability in all cell lines tested (LC50 values after 24h: Jurkat: 18.55 mM, Molt 4: 13.02 mM, RCH-ACV: 38.11 mM, and RS4;11 45.36 mM (Fig. 1B). LC50 values after 48h: Jurkat: 7.36 mM, Molt 4: 6.53 mM, RCH-ACV: 31.73 mM, RS4;11 36.66 mM (Fig. 1C)). In addition, apoptosis measured by AnnexinV/ PI staining showed an increased percentage of apoptotic cells in a dose- and time-dependent manner in all cell lines upon treatment with the CREB inhibitor (apoptosis after 24h: Jurkat 35.83% to 79.7%, Molt 4: 12.19% to 48.5%), RCH-ACV 11.30% to 45.9%, and RS4;11 9.84% to 19.16. Apoptosis after 48h: Jurkat 53.40% to 86.4%, Molt 4: 27.70% to 92.9%, RCH-ACV 14.07% to 63.32%, and RS4;11 7.11% to 20.75%) (Fig. 1D). To investigate the downstream effect of CREB inhibition we measured the mRNA expression of a know CREB target gene: BCL-2. Upon inhibition of CREB (50 mM KG-501) mRNA levels of BCL-2 were found to be significantly decreased compared to vehicle treated cells. In conclusion we have identified the transcription factor CREB in vitro as a potential druggable target for ALL. It is known that CREB plays an important role as a downstream target of hematopoietic growth factor signaling in hematopoiesis (Cheng et al, 2008). Based on these results, we propose CREB as a promising potential druggable target in ALL. [Display omitted] Figure 1. (A) Provisional signal transduction scheme of active kinases and phosphorylated proteins in ALL. Green: active kinase; Yellow: phosphorylated protein; Green-Yellow: active kinase and phosphorylated protein. (B) Cell viability percentages plotted against concentration of KG-501 (mM) after 24h. (C) Cell viability percentages plotted against concentration of KG-501 (mM) after 48h. (D) Representative flow cytometric dot-plots of AnnexinV/ PI flow cytometry, inhibition of CREB induced a dose- and time-dependent apoptosis in the Molt 4 cell line. Disclosures:No relevant conflicts of interest to declare.