Yucel Erbilgin

Parallel visualization of multiple protein complexes in individual cells in tumor tissue.

Cellular functions are regulated and executed by complex protein interaction networks. Accordingly, it is essential to understand the interplay between proteins in determining the activity status of signaling cascades. New methods are therefore required to provide information on different protein interaction events at the single cell level in heterogeneous cell populations such as in tissue sections. Here, we describe a multiplex proximity ligation assay for simultaneous visualization of multiple protein complexes in situ. The assay is an enhancement of the original proximity ligation assay, and it is based on using proximity probes labeled with unique tag sequences that can be used to read out which probes, from a pool of probes, have bound a certain protein complex. Using this approach, it is possible to gain information on the constituents of different protein complexes, the subcellular location of the complexes, and how the balance between different complex constituents can change between normal and malignant cells, for example. As a proof of concept, we used the assay to simultaneously visualize multiple protein complexes involving EGFR, HER2, and HER3 homo- and heterodimers on a single-cell level in breast cancer tissue sections. The ability to study several protein complex formations concurrently at single cell resolution could be of great potential for a systems understanding, paving the way for improved disease diagnostics and possibilities for drug development.

Elevated TRIB2 with NOTCH1 activation in paediatric/adult T-ALL

TRIB2 is a potent oncogene, elevated in a subset of human acute myeloid leukaemias (AML) with a mixed myeloid/lymphoid phenotype and NOTCH1 mutations. Although rare in AML, activating NOTCH1 mutations occur in 50% of all T cell acute lymphoblastic leukaemias (T‐ALL). TRIB2 is a NOTCH1 target gene that functions in the degradation of key proteins and modulation of MAPK signalling pathways, implicated in haematopoietic cell survival and proliferation. This study showed that TRIB2 expression level is highest in the lymphoid compartment of normal haematopoietic cells, specifically in T cells. Analysis of TRIB2 expression across 16 different subtypes of human leukaemia demonstrated that TRIB2 expression was higher in ALL phenotypes versus all other phenotypes including AML, chronic lymphocytic leukaemia (CLL), myelodysplastic syndrome (MDS) and chronic myeloid leukaemia (CML). A T cell profile was distinguished by high TRIB2 expression in normal and malignant haematopoiesis. High TRIB2 expression was seen in T‐ALL with normal karyotype and correlated with NOTCH signalling pathways. High TRIB2 expression correlated with NOTCH1/FBXW7 mutations in a paediatric T‐ALL cohort, strongly linking NOTCH1 activation and high TRIB2 expression in paediatric T‐ALL. The relationship between TRIB2 and T cell signalling pathways uniquely identifies leukaemia subtypes and will be useful in the advancement of our understanding of T cell and ALL biology.

Deregulated WNT signaling in childhood T-cell acute lymphoblastic leukemia

WNT signaling has been implicated in the regulation of hematopoietic stem cells and plays an important role during T-cell development in thymus. Here we investigated WNT pathway activation in childhood T-cell acute lymphoblastic leukemia (T-ALL) patients. To evaluate the potential role of WNT signaling in T-cell leukomogenesis, we performed expression analysis of key components of WNT pathway. More than 85% of the childhood T-ALL patients showed upregulated β-catenin expression at the protein level compared with normal human thymocytes. The impact of this upregulation was reflected in high expression of known target genes (AXIN2, c-MYC, TCF1 and LEF). Especially AXIN2, the universal target gene of WNT pathway, was upregulated at both mRNA and protein levels in ∼40% of the patients. When β-CATENIN gene was silenced by small interfering RNA, the cancer cells showed higher rates of apoptosis. These results demonstrate that abnormal WNT signaling activation occurs in a significant fraction of human T-ALL cases independent of known T-ALL risk factors. We conclude that deregulated WNT signaling is a novel oncogenic event in childhood T-ALL.

Prognostic significance of NOTCH1 and FBXW7 mutations in pediatric T-ALL.

The NOTCH signaling pathway plays important role in the development of multicellular organisms, as it regulates cell proliferation, survival, and differentiation. In adults, it is essential for the T- or B-lymphocyte lineage commitment. NOTCH1 and FBXW7 mutations both lead the activation of the NOTCH1 pathway and are found in the majority of T-ALL patients. In this study, the mutation analysis of NOTCH1 and FBXW7 genes was performed in 87 pediatric T-ALLs who were treated on the ALL-BFM protocols. In 19 patients (22%), activating NOTCH1 mutations were observed either in the heterodimerization domain or in the PEST domain and 7 cases (10%) demonstrated FBXW7 mutations (2 cases had both NOTCH1 and FBXW7 mutations). We also analyzed the relationship of the mutation data between the clinical and biological data of the patients. NOTCH1 and FBXW7, NOTCH1 alone were found correlated with lower initial leucocyte counts which was independent from the sex and T- cell immunophenotype. However, NOTCH1 and FBXW7 mutations were not predictive of outcome in the overall cohort of pediatric T-ALLs.

Effects of Imatinib Mesylate on Renin-Angiotensin System (RAS) Activity During the Clinical Course of Chronic Myeloid Leukaemia

The renin–angiotensin system (RAS) is involved in cell growth, proliferation and differentiation in bone marrow in an autocrine–paracrine manner, and it modulates normal and neoplastic haematopoietic cell proliferation. This study aimed to assess expressions of the RAS components, renin, angiotensinogen and angiotensin-converting enzyme (ACE), during imatinib mesylate treatment of patients with chronic myeloid leukaemia (CML). Expressions of RAS components were studied in patients with CML at the time of diagnosis (n = 83) and at 3, 6 and 12 months after diagnosis (n = 35) by quantitative real-time polymerase chain reaction. De novo CML patients had increased ACE, angiotensinogen and renin mRNA levels and these expression levels decreased following administration of imatinib. The RAS activities were significantly different among Sokal risk groups of CML, highlighting the altered biological activity of RAS in neoplastic disorders. The results of this study confirm that haematopoietic RAS affects neoplastic cell production, which may be altered via administration of tyrosine kinase inhibitors such as imatinib mesylate.

Local hematopoietic renin-angiotensin system in myeloid versus lymphoid hematological neoplastic disorders

There is preliminary evidence that the local renin-angiotensin system (RAS) could affect neoplastic hematopoiesis. The aim of this study is to search messenger RNA (mRNA) expressions of the essential RAS elements in myeloid and lymphoid hematological neoplastic disorders. Forty-six patients with newly diagnosed myeloid (AML, biphenotypic leukemia, CML) or lymphoid (CLL, NHL, B-ALL, T-ALL) hematological disorders were included in the study. In the lymphoid group, the median expression values of RENIN, ACE1, ACE2 and ANGIOTENSINOGEN (ANGTS) mRNAs were 1.96%, 0.42%, 0.00% and 0.00%, respectively; in the myeloid group, 0.73%, 1.55%, 0.04% and 0.006%, respectively. In the lymphoid group, RENIN levels were significantly higher (p = 0.001), whereas ACE1 and ACE2 levels were significantly higher in the myeloid group (p values were 0.013 and 0.010, respectively). ANGTS levels were similar in both groups. In patients with non-ALL lymphoid malignancies, RENIN expressions were significantly higher when compared to ALL patients (p = 0.004). All patients with active disease had significantly higher RENIN mRNA expression levels than patients without active disease (2.03% vs 0.30%) (p = 0.034). The result of our present study indicates that the activities of local RAS may differ in distinct disease states such as leukemia and lymphomas.

ABL gene kinase domain mutation scanning by denaturing high performance liquid chromatography sequencing method.

OBJECTIVE Despite the efficacy of the BCR-ABL tyrosine kinase inhibitor imatinib, the development of resistance against imatinib has been observed. The most important mechanisms known to cause resistance are point mutations in the ABL tyrosine kinase and the ATP domain. This study describes the use of denaturing high performance liquid chromatography (dHPLC) as a method to screen for mutations of the ABL gene. METHODS We used the dHPLC based assay for the screening of ABL point mutations. Forty chronic myeloid leukemia (CML) patients who showed resistance to imatinib were screened in parallel by dHPLC and direct sequencing. RESULTS Nine of the 40 patients (23%) had mutations. CONCLUSION dHPLC can be a useful method for pre-screening. Analyzing the mutations and monitoring (high-risk) patients can improve their prognosis and survival rate. dHPLC can potentially become a valuable tool for regular testing of patients in the future.

Local Renin-Angiotensin System in Normal Hematopoietic and Multiple Myeloma-Related Progenitor Cells

Objective: The prominent functions of the local renin-angiotensin system (RAS) in primitive hematopoiesis further support the hypothesis that local autocrine bone marrow RAS could also be active in neoplastic hematopoiesis. The aim of this study is to examine critical RAS elements in normal CD34+ hematopoietic stem cells and multiple myeloma (MM)-related progenitor cells. Materials and Methods: The study group comprised the total bone marrow cells (CBM) of 10 hematologically normal people, the CD34+ stem cell samples (CD34+CBM) of 9 healthy donors for allogeneic peripheral stem cell transplantation, and the CD34+ stem cell samples (CD34+MM) of 9 MM patients undergoing autologous peripheral stem cell transplantation. We searched for the gene expression of the major RAS components in healthy hematopoietic cells and myeloma cells by quantitative real-time polymerase chain reaction analysis. Results: RENIN, angiotensinogen (ANGTS), and angiotensin converting enzyme-I (ACE I) mRNA expression levels of CBM were significantly higher than those in myeloma patients (p=0.03, p=0.002, and p=0.0008, respectively). Moreover, RENIN and ANGTS mRNA expression levels were significantly higher in CD34+ stem cell samples of healthy allogeneic donors compared to those in myeloma patients (p=0.001 and p=0.01). However, ACE I expression levels were similar in CD34+CBM and CD34+MM hematopoietic cells (p=0.89). Conclusion: Although found to be lower than in the CBM and CD34+CBM hematopoietic cells, the local RAS components were also expressed in CD34+MM hematopoietic cells. This point should be kept in mind while focusing on the immunobiology of MM and the processing of autologous cells during the formation of transplantation treatment protocols.

Upregulation of T-Cell-Specific Transcription Factor Expression in Pediatric T-Cell Acute Lymphoblastic Leukemia (T-ALL).

Objective: T-cell acute lymphoblastic leukemia (T-ALL) is associated with recurrent chromosomal aberrations andabnormal ectopic gene expression during T-cell development. In order to gain insight into the pathogenesis of T-ALLthis study aimed to measure the level of expression of 7 T-cell oncogenes (LMO2, LYL1, TAL1, TLX1, TLX3, BMI1, andCALM-AF10) in pediatric T-ALL patients Material and Methods: LMO2, LYL1, TLX1, TLX3, BMI1, TAL1, and CALM-AF10 expression was measured usingquantitative real-time PCR in 43 pediatric T-ALL patients. Results: A high level of expression of LMO2, LYL1, TAL1, and BMI1 genes was observed in a large group of T-ALL.Several gene expression signatures indicative of leukemic arrest at specific stages of normal thymocyte development(LYL1 and LMO2) were highly expressed during the cortical and mature stages of T-cell development. Furthermore,upregulated TAL1 and BMI1 expression was observed in all phenotypic subgroups. In all, 6 of the patients had TLX1and TLX3 proto-oncogene expression, which does not occur in normal cells, and none of the patients had CALM-AF10fusion gene transcription. Expression of LYL1 alone and LMO2-LYL1 co-expression were associated with mediastinalinvolvement; however, high-level oncogene expression was not predictive of outcome in the present pediatric T-ALLpatient group, but there was a trend towards a poor prognostic impact of TAL1 and/or LMO2 and/or LYL1 protooncogeneexpression. Conclusion: Poor prognostic impact of TAL1 and/or LMO2 and/or LYL1 proto-oncogene expression indicate the needfor extensive study on oncogenic rearrangement and immunophenotypic markers in T-ALL, and their relationship totreatment outcome. Conflict of interest:None declared.

Evaluation of PAX5 gene in the early stages of leukemic B cells in the childhood B cell acute lymphoblastic leukemia.

B-lineage acute lymphoblastic leukemia (B-ALL) is a common subtype of acute leukemia in children. PAX5 plays a central role in B-cell development and differentiation. In this study, we analyzed PAX5 expression levels, transactivation domain mutations/deletions in B-ALL patients (n=115) and healthy controls (n=10). Relative PAX5 mRNA levels were significantly increased in B-ALL patients (p<0.0001). PAX5 expression was also evaluated in three different B-ALL subgroups (pro B, Common B and Pre B ALL) and showed stage specific expression levels. Pro B (p=0.04) and pre B (p=0.04) patients showed significantly high PAX5 mRNA levels compared to stage specific controls. At least one deletion of exons 7-8 or 9 has been identified in the 41% of the patients. CD34 positivity in patients and presence of large deletions (Δ7/8/9) showed a significant correlation (p=0.05). None of our patients showed PAX5 point mutations, but two previously identified SNPs (rs3780135 and rs35469494) were detected. Our results support that PAX5 is a critical factor in B-ALL development and aberrant PAX5 expression especially at early stages may leads to leukemic transformation.