ZAP-70 constitutively regulates gene expression and protein synthesis in chronic lymphocytic leukemia

The dual role of SUSD2 in cancer development

Sushi domain-containing protein 2 (SUSD2, also known as the complement control protein domain) is a representative and vital protein in the SUSD protein family involved in many physiological and pathological processes beyond complement regulation. Cancer is one of the leading causes of death worldwide. The complex role of SUSD2 in tumorigenesis and cancer progression has raised increasing concerns. Studies suggest that SUSD2 has different regulatory tendencies among different tumors and exerts its biological effects in a cancer type-specific manner; for instance, it has oncogenic effects on breast cancer, gastric cancer, and glioma and has tumor-suppression effects on lung cancer, bladder cancer, and colon cancer. Moreover, SUSD2 can be regulated by noncoding RNAs, its promoter methylation and other molecules, such as Galectin-1 (Gal-1), tropomyosin alpha-4 chain (TPM4), and p63. The therapeutic implications of targeting SUSD2 have already been preliminarily revealed in some malignancies, including melanoma, colon cancer, and breast cancer. This article reviews the role and regulatory mechanisms of SUSD2 in cancer development, as well as its structure and distribution. We hope that this review will advance the understanding of SUSD2 as a diagnostic and/or prognostic biomarker and provide new avenues for the development of novel cancer therapies.

B cell receptor signaling proteins as biomarkers for progression of CLL requiring first-line therapy

The molecular landscape of chronic lymphocytic leukemia (CLL) has been extensively characterized, and various potent prognostic biomarkers were discovered. The genetic composition of the B-cell receptor (BCR) immunoglobulin (IG) was shown to be especially powerful for discerning indolent from aggressive disease at diagnosis. Classification based on the IG heavy chain variable gene (IGHV) somatic hypermutation status is routinely applied. Additionally, BCR IGH stereotypy has been implicated to improve risk stratification, through characterization of subsets with consistent clinical profiles. Despite these advances, it remains challenging to predict when CLL progresses to requiring first-line therapy, thus emphasizing the need for further refinement of prognostic indicators. Signaling pathways downstream of the BCR are essential in CLL pathogenesis, and dysregulated components within these pathways impact disease progression. Considering not only genomics but the entirety of factors shaping BCR signaling activity, this review offers insights in the disease for better prognostic assessment of CLL.

ZAP-70 augments tonic B-cell receptor and CCR7 signaling in IGHV-unmutated chronic lymphocytic leukemia

ABSTRACT

Expression of ZAP-70 in a subset of patients with chronic lymphocytic leukemia (CLL) positively correlates with the absence of immunoglobulin heavy-chain gene (IGHV) mutations and is indicative of a more active disease and shorter treatment-free survival. We recently demonstrated that ZAP-70 regulates the constitutive expression of CCL3 and CCL4, activation of AKT, and expression of MYC in the absence of an overt B-cell receptor (BCR) signal, bona fide functions of BCR activation. We, here, provide evidence that these features relate to the presence of a constitutive tonic BCR signal, exclusively found in IGHV-unmutated CLL and dependent on the ZAP-70-mediated activation of AKT and its downstream target GSK-3β. These findings are associated with increased steady-state activation of CD19 and SRC. Notably this tonic BCR signal is not present in IGHV-mutated CLL cells, discordantly expressing ZAP-70. Results of quantitative mass spectrometry and phosphoprotein analyses indicate that this ZAP-70-dependent, tonic BCR signal regulates CLL cell migration through phosphorylation of LCP1 on serine-5. Indeed, we show that CCL19- and CCL21-induced chemotaxis is regulated by and dependent on the expression of ZAP-70 through its function to enhance CCR7 signaling to LCP1. Thus, our data demonstrate that ZAP-70 converges a tonic BCR signal, exclusively present in IGHV-unmutated CLL and CCR7-mediated chemotaxis.

B cell receptor signaling and associated pathways in the pathogenesis of chronic lymphocytic leukemia

B cell antigen receptor (BCR) signaling is a key driver of growth and survival in both normal and malignant B cells. Several lines of evidence support an important pathogenic role of the BCR in chronic lymphocytic leukemia (CLL). The significant improvement of CLL patients' survival with the use of various BCR pathway targeting inhibitors, supports a crucial involvement of BCR signaling in the pathogenesis of CLL. Although the treatment landscape of CLL has significantly evolved in recent years, no agent has clearly demonstrated efficacy in patients with treatment-refractory CLL in the long run. To identify new drug targets and mechanisms of drug action in neoplastic B cells, a detailed understanding of the molecular mechanisms of leukemic transformation as well as CLL cell survival is required. In the last decades, studies of genetically modified CLL mouse models in line with CLL patient studies provided a variety of exciting data about BCR and BCR-associated kinases in their role in CLL pathogenesis as well as disease progression. BCR surface expression was identified as a particularly important factor regulating CLL cell survival. Also, BCR-associated kinases were shown to provide a crosstalk of the CLL cells with their tumor microenvironment, which highlights the significance of the cells' milieu in the assessment of disease progression and treatment. In this review, we summarize the major findings of recent CLL mouse as well as patient studies in regard to the BCR signalosome and discuss its relevance in the clinics.

Cell softness renders cytotoxic T lymphocytes and T leukemic cells resistant to perforin-mediated killing

Mechanical force contributes to perforin pore formation at immune synapses, thus facilitating the cytotoxic T lymphocytes (CTL)-mediated killing of tumor cells in a unidirectional fashion. How such mechanical cues affect CTL evasion of perforin-mediated autolysis remains unclear. Here we show that activated CTLs use their softness to evade perforin-mediated autolysis, which, however, is shared by T leukemic cells to evade CTL killing. Downregulation of filamin A is identified to induce softness via ZAP70-mediated YAP Y357 phosphorylation and activation. Despite the requirements of YAP in both cell types for softness induction, CTLs are more resistant to YAP inhibitors than malignant T cells, potentially due to the higher expression of the drug-resistant transporter, MDR1, in CTLs. As a result, moderate inhibition of YAP stiffens malignant T cells but spares CTLs, thus allowing CTLs to cytolyze malignant cells without autolysis. Our findings thus hint a mechanical force-based immunotherapeutic strategy against T cell leukemia.

Prognostic Potential of Galectin-9 mRNA Expression in Chronic Lymphocytic Leukemia

Galectin-9 (Gal-9), very poorly characterized in chronic lymphocytic leukemia (CLL), was chosen in our study to examine its potential role as a CLL biomarker. The relation of Gal-9 expression in malignant B-cells and other routinely measured CLL markers, as well as its clinical relevance are poorly understood. Gal-9 mRNA expression was quantified with RT-qPCR in purified CD19+ B-cells of 100 CLL patients and analyzed in the context of existing clinical data. Our results revealed the upregulation of Gal-9 mRNA in CLL cells. High Gal-9 mRNA expression was closely associated with unfavorable prognostic markers. In addition, Gal-9 expression in leukemic cells was significantly elevated in CLL patients who did not respond to the first-line therapy compared to those who did respond. This suggests its potential predictive value. Importantly, Gal-9 was an independent predictor for the time to treatment parameters. Thus, we can suggest an adverse role of Gal-9 expression in CLL. Interestingly, it is possible that Gal-9 expression is induced in B-cells by EBV infection, so we determined the patients' EBV status. Our suggestion is that EBV coinfection could worsen prognosis in CLL, partly due to Gal-9 expression upregulation caused by EBV.

A Story of Kinases and Adaptors: The Role of Lck, ZAP-70 and LAT in Switch Panel Governing T-Cell Development and Activation

Specific antigen recognition is one of the immune system's features that allows it to mount intense yet controlled responses to an infinity of potential threats. T cells play a relevant role in the host defense and the clearance of pathogens by means of the specific recognition of peptide antigens presented by antigen-presenting cells (APCs), and, to do so, they are equipped with a clonally distributed antigen receptor called the T-cell receptor (TCR). Upon the specific engagement of the TCR, multiple intracellular signals are triggered, which lead to the activation, proliferation and differentiation of T lymphocytes into effector cells. In addition, this signaling cascade also operates during T-cell development, allowing for the generation of cells that can be helpful in the defense against threats, as well as preventing the generation of autoreactive cells. Early TCR signals include phosphorylation events in which the tyrosine kinases Lck and ZAP70 are involved. The sequential activation of these kinases leads to the phosphorylation of the transmembrane adaptor LAT, which constitutes a signaling hub for the generation of a signalosome, finally resulting in T-cell activation. These early signals play a relevant role in triggering the development, activation, proliferation and apoptosis of T cells, and the negative regulation of these signals is key to avoid aberrant processes that could generate inappropriate cellular responses and disease. In this review, we will examine and discuss the roles of the tyrosine kinases Lck and ZAP70 and the membrane adaptor LAT in these cellular processes.

A Nine-Gene Expression Signature Distinguished a Patient with Chronic Lymphocytic Leukemia Who Underwent Prolonged Periodic Fasting

Background and Objectives: This study aimed to investigate the causes of continuous deep fluctuations in the absolute lymphocyte count (ALC) in an untreated patient with Chronic Lymphocytic Leukemia (CLL), who has had a favorable prognosis since the time of diagnosis. Up until now, the patient has voluntarily chosen to adopt a predominantly vegetarian and fruitarian diet, along with prolonged periods of total fasting (ranging from 4 to 39 days) each year. Materials and Methods: For this purpose, we decided to analyze the whole transcriptome profiling of peripheral blood (PB) CD19+ cells from the patient (#1) at different time-points vs. the same cells of five other untreated CLL patients who followed a varied diet. Consequently, the CLL patients were categorized as follows: the 1st group comprised patient #1 at 20 different time-points (16 time-points during nutrition and 4 time-points during fasting), whereas the 2nd group included only one time point for each of the patients (#2, #3, #4, #5, and #6) as they followed a varied diet. We performed microarray experiments using a powerful tool, the Affymetrix Human Clariom™ D Pico Assay, to generate high-fidelity biomarker signatures. Statistical analysis was employed to identify differentially expressed genes and to perform sample clustering. Results: The lymphocytosis trend in patient #1 showed recurring fluctuations since the time of diagnosis. Interestingly, we observed that approximately 4-6 weeks after the conclusion of fasting periods, the absolute lymphocyte count was reduced by about half. The gene expression profiling analysis revealed that nine genes were statistically differently expressed between the 1st group and the 2nd group. Specifically, IGLC3, RPS26, CHPT1, and PCDH9 were under expressed in the 1st group compared to the 2nd group of CLL patients. Conversely, IGHV3-43, IGKV3D-20, PLEKHA1, CYBB, and GABRB2 were over-expressed in the 1st group when compared to the 2nd group of CLL patients. Furthermore, clustering analysis validated that all the samples from patient #1 clustered together, showing clear separation from the samples of the other CLL patients. Conclusions: This study unveiled a small gene expression signature consisting of nine genes that distinguished an untreated CLL patient who followed prolonged periods of total fasting, maintaining a gradual growth trend of lymphocytosis, compared to five untreated CLL patients with a varied diet. Future investigations focusing on patient #1 could potentially shed light on the role of prolonged periodic fasting and the implication of this specific gene signature in sustaining the lymphocytosis trend and the favorable course of the disease.

A Non-Canonical Role for the Glycosyltransferase Enzyme UGT2B17 as a Novel Constituent of the B Cell Receptor Signalosome

In chronic lymphocytic leukemia (CLL), an elevated glycosyltransferase UGT2B17 expression (UGT2B17HI) identifies a subgroup of patients with shorter survival and poor drug response. We uncovered a mechanism, possibly independent of its enzymatic function, characterized by an enhanced expression and signaling of the proximal effectors of the pro-survival B cell receptor (BCR) pathway and elevated Bruton tyrosine kinase (BTK) phosphorylation in B-CLL cells from UGT2B17HI patients. A prominent feature of B-CLL cells is the strong correlation of UGT2B17 expression with the adverse marker ZAP70 encoding a tyrosine kinase that promotes B-CLL cell survival. Their combined high expression levels in the treatment of naïve patients further defined a prognostic group with the highest risk of poor survival. In leukemic cells, UGT2B17 knockout and repression of ZAP70 reduced proliferation, suggesting that the function of UGT2B17 might involve ZAP70. Mechanistically, UGT2B17 interacted with several kinases of the BCR pathway, including ZAP70, SYK, and BTK, revealing a potential therapeutic vulnerability. The dual SYK and JAK/STAT6 inhibitor cerdulatinib most effectively compromised the proliferative advantage conferred by UGT2B17 compared to the selective BTK inhibitor ibrutinib. Findings point to an oncogenic role for UGT2B17 as a novel constituent of BCR signalosome also connected with microenvironmental signaling.

CD160 receptor in CLL: Current state and future avenues

CD160 is a glycosylphosphatidylinositol (GPI)-anchored cell surface glycoprotein expressed on cytotoxic natural killer (NK) cells and T-cell subsets. It plays a crucial role in the activation of NK-cell cytotoxicity and cytokine production. It also modulates the immune system and is involved in some pathologies, such as cancer. CD160 is abnormally expressed in B-cell chronic lymphocytic leukemia (CLL) but not expressed in normal B lymphocytes. Its expression in CLL enhances tumor cell proliferation and resistance to apoptosis. CD160 is also a potential prognostic marker for the detection of minimal residual disease (MRD) in CLL, which is important for the clinical management of CLL, the prevention of disease relapse, and the achievement of complete remission. In this review, we present an overview of CD160 and its involvement in the pathophysiology of CLL. We also discuss its use as a prognostic marker for the assessment of MRD in CLL.

Amino acid metabolism: challenges and opportunities for the therapeutic treatment of leukemia and lymphoma

Leukemia and lymphoma-the most common hematological malignant diseases-are often accompanied by complications such as drug resistance, refractory diseases and relapse. Amino acids (AAs) are important energy sources for malignant cells. Tumor-mediated AA metabolism is associated with the immunosuppressive properties of the tumor microenvironment, thereby assisting malignant cells to evade immune surveillance. Targeting abnormal AA metabolism in the tumor microenvironment may be an effective therapeutic approach to address the therapeutic challenges of leukemia and lymphoma. Here, we review the effects of glutamine, arginine and tryptophan metabolism on tumorigenesis and immunomodulation, and define the differences between tumor cells and immune effector cells. We also comment on treatments targeting these AA metabolism pathways in lymphoma and leukemia and discuss how these treatments have profound adverse effects on tumor cells, but leave the immune cells unaffected or mildly affected.

Identification of a Prognostic Model Based on Fatty Acid Metabolism-Related Genes of Head and Neck Squamous Cell Carcinoma

The fatty acid metabolism (FAM) is known to impact tumorigenesis, tumor progression and treatment resistance via enhancing lipid synthesis, storage and catabolism. However, the role of FAM in head and neck squamous cell carcinoma (HNSCC) has remained elusive. In the present study, we obtained a total of 69 differentially expressed FAM-related genes between 502 HNSCC samples and 44 normal samples from The Cancer Genome Atlas (TCGA) database. The HNSCC samples were divided into 2 clusters according to 69 differentially expressed genes (DEGs) via cluster analysis. Then DEGs in the two clusters were found, and 137 prognostic DEGs were identified by univariate analysis. Subsequently, combined with the clinical information of 546 HNSCC patients from TCGA database, a 12-gene prognostic risk model was established (FEPHX3, SPINK7, FCRLA, MASP1, ZNF541, CD5, BEST2 and ZAP70 were down-regulation, ADPRHL1, DYNC1I1, KCNG1 and LINC00460 were up-regulation) using multivariate Cox regression and LASSO regression analysis. The risk scores of 546 HNSCC samples were calculated. According to the median risk score, 546 HNSCC patients were divided into the high- and low-risk (high- and low score) groups. The Kaplan-Meier survival analysis showed that the survival time of HNSCC patients was significantly shorter in the high-risk group than that in the low-risk group (p < 0.001). The same conclusion was obtained in the Gene Expression Omnibus (GEO) dataset. After that, the multivariate Cox regression analysis indicated that the risk score was an independent factor for patients with HNSCC in the TCGA cohort. In addition, single-sample gene set enrichment analysis (ssGSEA) indicated that the level of infiltrating immune cells was relatively low in the high-risk group compared with the low-risk group. In summary, FAM-related gene expression-based risk signature could predict the prognosis of HNSCC independently.

SYK and ZAP70 kinases in autoimmunity and lymphoid malignancies

SYK and ZAP70 nonreceptor tyrosine kinases serve essential roles in initiating B-cell receptor (BCR) and T-cell receptor (TCR) signaling in B- and T-lymphocytes, respectively. Despite their structural and functional similarity, expression of SYK and ZAP70 is strictly separated during B- and T-lymphocyte development, the reason for which was not known. Aberrant co-expression of ZAP70 with SYK was first identified in B-cell chronic lymphocytic leukemia (CLL) and is considered a biomarker of aggressive disease and poor clinical outcomes. We recently found that aberrant ZAP70 co-expression not only functions as an oncogenic driver in CLL but also in various other B-cell malignancies, including acute lymphoblastic leukemia (B-ALL) and mantle cell lymphoma. Thereby, aberrantly expressed ZAP70 redirects SYK and BCR-downstream signaling from NFAT towards activation of the PI3K-pathway. In the sole presence of SYK, pathological BCR-signaling in autoreactive or premalignant cells induces NFAT-activation and NFAT-dependent anergy and negative selection. In contrast, negative selection of pathological B-cells is subverted when ZAP70 diverts SYK from activation of NFAT towards tonic PI3K-signaling, which promotes survival instead of cell death. We discuss here how both B-cell malignancies and autoimmune diseases frequently evolve to harness this mechanism, highlighting the importance of developmental separation of the two kinases as an essential safeguard.