Enhanced pro-apoptotic activity of rituximab through IBTK silencing in non-Hodgkin lymphoma B-cells

Rituximab is a commonly used chemotherapeutic drug for patients with aggressive lymphomas, such as non-Hodgkin's lymphoma (NHL). Currently, the combination of Rituximab and chemotherapy (R-CHOP) stands as the most prevalent first-line therapy for NHL. Nevertheless, the development of new therapeutic approaches remains imperative. An increasing body of evidence highlights a novel role for IBTK in tumorigenesis and cancer growth. In this study, we aim to broaden our understanding of IBTK's function in B-lymphoma, with a particular focus on its impact on the expression of the oncogene MYC. Here, we assessed the effects of combining Rituximab with IBTK silencing on cell viability through cell cycle analysis and Annexin V assays in vitro. Furthermore, we leveraged the transplantability of Eμ-myc lymphomas to investigate whether the inhibition of IBTK could elicit anti-tumor effects in the treatment of lymphomas in vivo. Our data suggests that IBTK silencing may serve as an effective anti-tumor agent for aggressive B-Lymphomas, underscoring its role in promoting apoptosis when used in combination with Rituximab, both in in vitro and in vivo settings.

SARS CoV-2 spike protein-guided exosome isolation facilitates detection of potential miRNA biomarkers in COVID-19 infections

OBJECTIVES

Nearly three years into the pandemic, SARS-CoV-2 infections are occurring in vaccinated and naturally infected populations. While humoral and cellular responses in COVID-19 are being characterized, novel immune biomarkers also being identified. Recently, an increase in angiotensin-converting enzyme 2 expressing (aka, ACE2 positive) circulating exosomes (ExoACE2) were identified in the plasma of COVID-19 patients (El-Shennawy et al.). In this pilot study, we describe a method to characterize the exosome-associated microRNA (exo-miRNA) signature in ACE2-positive and ACE2-negative exosomal populations (non-ExoACE2).

METHODS

We performed a sorting protocol using the recombinant biotin-conjugated SARS CoV-2 spike protein containing the receptor binding domain (RBD) on plasma samples from six patients. Following purification, exo-miRNA were characterized for ACE2-positive and ACE2-negative exosome subpopulations by RT-PCR.

RESULTS

We identified differential expression of several miRNA. Specifically let-7g-5p and hsa-miR-4454+miR-7975 were upregulated, while hsa-miR-208a-3p and has-miR-323-3p were downregulated in ExoACE2 vs. non-ExoACE2.

CONCLUSIONS

The SARS CoV-2 spike-protein guided exosome isolation permits isolation of ExoACE2 exosomes. Such purification facilitates detailed characterization of potential biomarkers (e.g. exo-miRNA) for COVID-19 patients. This method could be used for future studies to further the understanding mechanisms of host response against SARS CoV-2.

Development of Cyclic Peptides Targeting the Epidermal Growth Factor Receptor in Mesenchymal Triple-Negative Breast Cancer Subtype

Triple-negative breast cancer (TNBC) is an aggressive malignancy characterized by the lack of expression of estrogen and progesterone receptors and amplification of human epidermal growth factor receptor 2 (HER2). Being the Epidermal Growth Factor Receptor (EGFR) highly expressed in mesenchymal TNBC and correlated with aggressive growth behavior, it represents an ideal target for anticancer drugs. Here, we have applied the phage display for selecting two highly specific peptide ligands for targeting the EGFR overexpressed in MDA-MB-231 cells, a human TNBC cell line. Molecular docking predicted the peptide-binding affinities and sites in the extracellular domain of EGFR. The binding of the FITC-conjugated peptides to human and murine TNBC cells was validated by flow cytometry. Confocal microscopy confirmed the peptide binding specificity to EGFR-positive MDA-MB-231 tumor xenograft tissues and their co-localization with the membrane EGFR. Further, the peptide stimulation did not affect the cell cycle of TNBC cells, which is of interest for their utility for tumor targeting. Our data indicate that these novel peptides are highly specific ligands for the EGFR overexpressed in TNBC cells, and thus they could be used in conjugation with nanoparticles for tumor-targeted delivery of anticancer drugs.

Unmutated IGHV1-69 CLL Clone Displays a Distinct Gene Expression Profile by a Comparative qRT-PCR Assay

Chronic Lymphocytic Leukemia (CLL) is a heterogeneous disease characterized by variable clinical courses among different patients. This notion was supported by the possible coexistence of two or more independent CLL clones within the same patients, identified by the characterization of the B cell receptor immunoglobulin (BcR IG) idiotypic sequence. By using the antigen-binding site of the BcR IG as bait, the identification and isolation of aggressive and drug-resistance leukemic B-cell clones could allow a deeper biological and molecular investigation. Indeed, by the screening of phage display libraries, we previously selected a peptide binder of the idiotypic region of CLL BCR IGs expressing the unmutated rearrangement IGHV1-69 and used it as a probe to perform a peptide-based cell sorting by flow cytometry in peripheral blood samples from patients with CLL. Since the IGHV1-69 clones persisted during the follow-up time in both patients, we explored the possibility of these clones having acquired an evolutive advantage compared to the other coexisting clones in terms of a higher expression of genes involved in the survival and apoptosis escape processes. To this end, we studied the expression patterns of a panel of genes involved in apoptosis regulation and in NF-kB-dependent pro-survival signals by comparative qRT-PCR assays. According to the results, IGHV1-69 clones showed a higher expression of pro-survival and anti-apoptotic genes as compared to the other CLL clones with different immunogenetic characteristics. Moreover, these IGHV1-69 clones did not carry any characteristic genetic lesions, indicating the relevance of our approach in performing a comprehensive molecular characterization of single tumor clones, as well as for designing new personalized therapeutic approaches for the most aggressive and persistent tumor clones.

A novel phage display based platform for exosome diversity characterization

We present an innovative approach allowing the identification, isolation, and molecular characterization of disease-related exosomes based on their different antigenic reactivities. The designed strategy could be immediately translated into any disease in which exosomes are involved. The identification of specific markers and their subsequent association with exosome subtypes, together with the possibility to engineer target-guided exosome-like particles, could represent the key for the effective adoption of exosomes in clinical practice.

Metabolites Profiling of Melanoma Interstitial Fluids Reveals Uridine Diphosphate as Potent Immune Modulator Capable of Limiting Tumor Growth

Tumor interstitial fluid (TIF) surrounds and perfuses tumors and collects ions, metabolites, proteins, and extracellular vesicles secreted by tumor and stromal cells. Specific metabolites, accumulated within the TIF, could induce metabolic alterations of immune cells and shape the tumor microenvironment. We deployed a metabolomic approach to analyze the composition of melanoma TIF and compared it to the plasma of C57BL6 mice, engrafted or not with B16-melanoma cells. Among the classes of metabolites analyzed, monophosphate and diphosphate nucleotides resulted enriched in TIF compared to plasma samples. The analysis of the effects exerted by guanosine diphosphate (GDP) and uridine diphosphate (UDP) on immune response revealed that GDP and UDP increased the percentage of CD4+CD25+FoxP3- and, on isolated CD4+ T-cells, induced the phosphorylation of ERK, STAT1, and STAT3; increased the activity of NF-κB subunits p65, p50, RelB, and p52; increased the expression of Th1/Th17 markers including IFNγ, IL17, T-bet, and RORγt; and reduced the expression of IL13, a Th2 marker. Finally, we observed that local administrations of UDP in B16-engrafted C57BL6 mice reduced tumor growth and necrotic areas. In addition, UDP-treated tumors showed a higher presence of MHCIIhi tumor-associated macrophage (TAM) and of CD3+CD8+ and CD3+CD4+ tumor-infiltrating T-lymphocytes (TILs), both markers of anti-tumor immune response. Consistent with this, intra-tumoral gene expression analysis revealed in UDP-treated tumors an increase in the expression of genes functionally linked to anti-tumor immune response. Our analysis revealed an important metabolite acting as mediator of immune response, which could potentially represent an additional tool to be used as an adjuvant in cancer immunotherapy.

Predominant VH1-69 IgBCR Clones Show Higher Expression of CD5 in Heterogeneous Chronic Lymphocytic Leukemia Populations

The immunoglobulin B cell receptor (IgBCR) expressed by chronic lymphocytic leukemia (CLL) B cells plays a pivotal role in tumorigenesis, supporting neoplastic transformation, survival, and expansion of tumor clones. We demonstrated that in the same patient, two or more CLL clones could coexist, recognized by the expression of different variable regions of the heavy chain of IgBCR, composing the antigen-binding site. In this regard, phage display screening could be considered the easier and most advantageous methodology for the identification of small peptide molecules able to mimic the natural antigen of the tumor IgBCRs. These molecules, properly functionalized, could be used as a probe to specifically identify and isolate single CLL subpopulations, for a deeper analysis in terms of drug resistance, phenotype, and gene expression. Furthermore, CLL cells express another surface membrane receptor, the CD5, which is commonly expressed by normal T cells. Piece of evidence supports a possible contribution of CD5 to the selection and maintenance of autoreactivity in B cells and the constitutive expression of CD5 on CLL cells could induce pro-survival stimuli. In this brief research report, we describe a peptide-based single-cell sorting using as bait the IgBCR of tumor cells; in the next step, we performed a quantitative analysis of CD5 expression by qRT-PCR related to the expressed IgBCR. Our approach could open a new perspective for the identification, isolation, and investigation of all subsets of IgBCR-related CLL clones, with particular attention to the more aggressive clones.

Phage-Displayed Peptides for Targeting Tyrosine Kinase Membrane Receptors in Cancer Therapy

Receptor tyrosine kinases (RTKs) regulate critical physiological processes, such as cell growth, survival, motility, and metabolism. Abnormal activation of RTKs and relative downstream signaling is implicated in cancer pathogenesis. Phage display allows the rapid selection of peptide ligands of membrane receptors. These peptides can target in vitro and in vivo tumor cells and represent a novel therapeutic approach for cancer therapy. Further, they are more convenient compared to antibodies, being less expensive and non-immunogenic. In this review, we describe the state-of-the-art of phage display for development of peptide ligands of tyrosine kinase membrane receptors and discuss their potential applications for tumor-targeted therapy.

Role of Chronic Lymphocytic Leukemia (CLL)-Derived Exosomes in Tumor Progression and Survival

Chronic lymphocytic leukemia (CLL) is a B-lymphoproliferative disease, which consists of the abnormal proliferation of CD19/CD5/CD20/CD23 positive lymphocytes in blood and lymphoid organs, such as bone marrow, lymph nodes and spleen. The neoplastic transformation and expansion of tumor B cells are commonly recognized as antigen-driven processes, mediated by the interaction of antigens with the B cell receptor (BCR) expressed on the surface of B-lymphocytes. The survival and progression of CLL cells largely depend on the direct interaction of CLL cells with receptors of accessory cells of tumor microenvironment. Recently, much interest has been focused on the role of tumor release of small extracellular vesicles (EVs), named exosomes, which incorporate a wide range of biologically active molecules, particularly microRNAs and proteins, which sustain the tumor growth. Here, we will review the role of CLL-derived exosomes as diagnostic and prognostic biomarkers of the disease.

Uncovering the Exosomes Diversity: A Window of Opportunity for Tumor Progression Monitoring

Cells can communicate through special “messages in the bottle”, which are recorded in the bloodstream inside vesicles, namely exosomes. The exosomes are nanovesicles of 30–100 nm in diameter that carry functionally active biological material, such as proteins, messanger RNA (mRNAs), and micro RNA (miRNAs). Therefore, they are able to transfer specific signals from a parental cell of origin to the surrounding cells in the microenvironment and to distant organs through the circulatory and lymphatic stream. More and more interest is rising for the pathological role of exosomes produced by cancer cells and for their potential use in tumor monitoring and patient follow up. In particular, the exosomes could be an appropriate index of proliferation and cancer cell communication for monitoring the minimal residual disease, which cannot be easily detectable by common diagnostic and monitoring techniques. The lack of unequivocal markers for tumor-derived exosomes calls for new strategies for exosomes profile characterization aimed at the adoption of exosomes as an official tumor biomarker for tumor progression monitoring.

Insights about MYC and Apoptosis in B-Lymphomagenesis: An Update from Murine Models

The balance between cell survival and cell death represents an essential part of human tissue homeostasis, while altered apoptosis contributes to several pathologies and can affect the treatment efficacy. Impaired apoptosis is one of the main cancer hallmarks and some types of lymphomas harbor mutations that directly affect key regulators of cell death (such as BCL-2 family members). The development of novel techniques in the field of immunology and new animal models has greatly accelerated our understanding of oncogenic mechanisms in MYC-associated lymphomas. Mouse models are a powerful tool to reveal multiple genes implicated in the genesis of lymphoma and are extensively used to clarify the molecular mechanism of lymphoma, validating the gene function. Key features of MYC-induced apoptosis will be discussed here along with more recent studies on MYC direct and indirect interactors, including their cooperative action in lymphomagenesis. We review our current knowledge about the role of MYC-induced apoptosis in B-cell malignancies, discussing the transcriptional regulation network of MYC and regulatory feedback action of miRs during MYC-driven lymphomagenesis. More importantly, the finding of new modulators of apoptosis now enabling researchers to translate the discoveries that have been made in the laboratory into clinical practice to positively impact human health.

IBTK contributes to B-cell lymphomagenesis in Eμ-myc transgenic mice conferring resistance to apoptosis

Increasing evidence supports the involvement of IBTK in cell survival and tumor growth. Previously, we have shown that IBTK RNA interference affects the wide genome expression and RNA splicing in cell-type specific manner. Further, the expression of IBTK gene progressively increases from indolent to aggressive stage of chronic lymphocytic leukemia and decreases in disease remission after therapy. However, the role of IBTK in tumorigenesis has not been elucidated. Here, we report that loss of the murine Ibtk gene raises survival and delays tumor onset in Eμ-myc transgenic mice, a preclinical model of Myc-driven lymphoma. In particular, we found that the number of pre-cancerous B cells of bone marrow and spleen is reduced in Ibtk^-/-Eμ-myc mice owing to impaired viability and increased apoptosis, as measured by Annexin V binding, Caspase 3/7 cleavage assays and cell cycle profile analysis. Instead, the proliferation rate of pre-cancerous B cells is unaffected by the loss of Ibtk. We observed a direct correlation between Ibtk and myc expression and demonstrated a Myc-dependent regulation of Ibtk expression in murine B cells, human hematopoietic and nonhematopoietic cell lines by analysis of ChIP-seq data. By tet-repressible Myc system, we confirmed a Myc-dependent expression of IBTK in human B cells. Further, we showed that Ibtk loss affected the main apoptotic pathways dependent on Myc overexpression in pre-cancerous Eμ-myc mice, in particular, MCL-1 and p53. Of note, we found that loss of IBTK impaired cell cycle and increased apoptosis also in a human epithelial cell line, HeLa cells, in Myc-independent manner. Taken together, these results suggest that Ibtk sustains the oncogenic activity of Myc by inhibiting apoptosis of murine pre-cancerous B cells, as a cell-specific mechanism. Our findings could be relevant for the development of IBTK inhibitors sensitizing tumor cells to apoptosis.

Exosome-associated miRNA profile as a prognostic tool for therapy response monitoring in multiple sclerosis patients

Multiple sclerosis (MS) is an autoimmune pathology leading to neurodegeneration. Because of the complexity and heterogenic etiology of this disease, diagnosis and treatment for individual patients are challenging. Exosome-associated microRNAs (miRNAs) have recently emerged as a new class of diagnostic biomarkers involved in both autoimmune and neurologic disorders. Interesting new evidence has emerged showing that circulating miRNAs are dysregulated in MS body fluids, including serum, plasma, and cerebrospinal fluid. We hypothesized that exosome-associated miRNAs could present a readily accessible blood-based assay for MS disease. We detected expression of miRNAs by quantitative PCR on a small cohort of MS patients. We analyzed circulating exosome-associated miRNAs of MS patients before and after therapy and found that 14 exosome-associated miRNAs were significantly down-regulated, while 2 exosome-associated miRNAs were significantly up-regulated in IFN-β-treated relapsing-remitting MS patients with response to therapy compared to those without response. We identified a serum miRNA panel that could be used to monitor the response to IFN-β therapy. Overall, these data suggest that circulating exosome-associated miRNA profiling could represent an easily detectable biomarker of disease and treatment response.-Manna, I., Iaccino, E., Dattilo, V., Barone, S., Vecchio, E., Mimmi, S., Filippelli, E., Demonte, G., Polidoro, S., Granata, A., Scannapieco, S., Quinto, I., Valentino, P., Quattrone, A. Exosome-associated miRNA profile as a prognostic tool for therapy response monitoring in multiple sclerosis patients.

Peptide-guided targeting of GPR55 for anti-cancer therapy

Expression of the lysophosphatidylinositol receptor GPR55 correlates with invasive potential of metastatic cells and bone metastasis formation of different types of tumors. These findings suggest a role for GPR55 signaling in cancer progression, including in lymphoproliferative diseases. Here, we screened a M13-phage-displayed random library using the bait of HEK293 cells that heterologously expressed full-length HA-GPR55. We selected a set of phagotopes that carried 7-mer insert peptides flanked by a pair of cysteine residues, which resulted in cyclized peptides. Sequencing of selected phagotopes dictated the primary structure for the synthetic FITC-labeled peptide P1, which was analyzed for binding specificity to immunoprecipitated HA-GPR55, and to endogenously expressed GPR55, using cells interfered or not for GPR55, as well as for co-localization imaging with HA-GPR55 at the membrane level. The peptide P1 stimulated GPR55 endocytosis and inhibited GPR55-dependent proliferation of EHEB and DeFew cells, two human B-lymphoblastoid cell lines. Our data support the potential therapeutic application of peptide ligands of GPR55 for targeting and inhibiting growth of neoplastic cells, which overexpress GPR55 and are dependent on GPR55 signaling for their proliferation.

The expression of inhibitor of bruton's tyrosine kinase gene is progressively up regulated in the clinical course of chronic lymphocytic leukaemia conferring resistance to apoptosis

Chronic lymphocytic leukaemia (CLL) is the most common B-cell malignancy with a variable clinical outcome. Biomarkers of CLL progression are required for optimising prognosis and therapy. The Inhibitor of Bruton’s tyrosine kinase—isoform α (IBTKα) gene encodes a substrate receptor of Cullin 3-dependent E3 ubiquitin ligase, and promotes cell survival in response to the reticulum stress. Searching for novel markers of CLL progression, we analysed the expression of IBTKα in the peripheral blood B-cells of CLL patients, before and after first line therapy causing remission. The expression of IBTKα was significantly increased in disease progression, and decreased in remission after chemotherapy. Consistently with a pro-survival action, RNA interference of IBTKα increased the spontaneous and Fludarabine-induced apoptosis of MEC-1 CLL cells, and impaired the cell cycle of DeFew B-lymphoma cells by promoting the arrest in G0/G1 phase and apoptosis. Consistently, RNA interference of IBTKα up regulated the expression of pro-apoptotic genes, including TNF, CRADD, CASP7, BNIP3 and BIRC3. Our results indicate that IBTKα is a novel marker of CLL progression promoting cell growth and resistance to apoptosis. In this view, IBTKα may represent an attractive cancer drug target for counteracting the therapy-resistance of tumour cells.

Monitoring multiple myeloma by idiotype-specific peptide binders of tumor-derived exosomes

Tumor-derived exosomes (TDEs) play a pivotal role in tumor establishment and progression, and are emerging biomarkers for tumor diagnosis in personalized medicine. To date, there is a lack of efficient technology platforms for exosome isolation and characterization. Multiple myeloma (MM) is an incurable B-cell malignancy due to the rapid development of drug-resistance. MM-released exosomes express the immunoglobulin B-cell receptor (Ig-BCR) of the tumor B-cells, which can be targeted by Idiotype-binding peptides (Id-peptides). In this study, we analyzed the production of MM-released exosomes in the murine 5T33MM multiple myeloma model as biomarkers of tumor growth. To this end, we selected Id-peptides by screening a phage display library using as bait the Ig-BCR expressed by 5T33MM cells. By FACS, the FITC-conjugated Id-peptides detected the MM-released exosomes in the serum of 5T33MM-engrafted mice, levels of which are correlated with tumor progression at an earlier time point compared to serum paraprotein. These results indicate that Id-peptide-based recognition of MM-released exosomes may represent a very sensitive diagnostic approach for clinical evaluation of disease progression.

IBTK Differently Modulates Gene Expression and RNA Splicing in HeLa and K562 Cells

The IBTK gene encodes the major protein isoform IBTKα that was recently characterized as substrate receptor of Cul3-dependent E3 ligase, regulating ubiquitination coupled to proteasomal degradation of Pdcd4, an inhibitor of translation. Due to the presence of Ankyrin-BTB-RCC1 domains that mediate several protein-protein interactions, IBTKα could exert expanded regulatory roles, including interaction with transcription regulators. To verify the effects of IBTKα on gene expression, we analyzed HeLa and K562 cell transcriptomes by RNA-Sequencing before and after IBTK knock-down by shRNA transduction. In HeLa cells, 1285 (2.03%) of 63,128 mapped transcripts were differentially expressed in IBTK-shRNA-transduced cells, as compared to cells treated with control-shRNA, with 587 upregulated (45.7%) and 698 downregulated (54.3%) RNAs. In K562 cells, 1959 (3.1%) of 63128 mapped RNAs were differentially expressed in IBTK-shRNA-transduced cells, including 1053 upregulated (53.7%) and 906 downregulated (46.3%). Only 137 transcripts (0.22%) were commonly deregulated by IBTK silencing in both HeLa and K562 cells, indicating that most IBTKα effects on gene expression are cell type-specific. Based on gene ontology classification, the genes responsive to IBTK are involved in different biological processes, including in particular chromatin and nucleosomal organization, gene expression regulation, and cellular traffic and migration. In addition, IBTK RNA interference affected RNA maturation in both cell lines, as shown by the evidence of alternative 3′- and 5′-splicing, mutually exclusive exons, retained introns, and skipped exons. Altogether, these results indicate that IBTK differently modulates gene expression and RNA splicing in HeLa and K562 cells, demonstrating a novel biological role of this protein.

Impairment of T cell development and acute inflammatory response in HIV-1 Tat transgenic mice

Immune activation and chronic inflammation are hallmark features of HIV infection causing T-cell depletion and cellular immune dysfunction in AIDS. Here, we addressed the issue whether HIV-1 Tat could affect T cell development and acute inflammatory response by generating a transgenic mouse expressing Tat in lymphoid tissue. Tat-Tg mice showed thymus atrophy and the maturation block from DN4 to DP thymic subpopulations, resulting in CD4⁺ and CD8⁺ T cells depletion in peripheral blood. In Tat-positive thymus, we observed the increased p65/NF-κB activity and deregulated expression of cytokines/chemokines and microRNA-181a-1, which are involved in T-lymphopoiesis. Upon LPS intraperitoneal injection, Tat-Tg mice developed an abnormal acute inflammatory response, which was characterized by enhanced lethality and production of inflammatory cytokines. Based on these findings, Tat-Tg mouse could represent an animal model for testing adjunctive therapies of HIV-1-associated inflammation and immune deregulation.

B-cell receptor-guided delivery of peptide-siRNA complex for B-cell lymphoma therapy

Background

Despite the clinical response of conventional anticancer therapy, including chemotherapeutic treatments, radiation therapy and corticosteroids, tumorigenic B-cell lymphomas show an incomplete response to clinical practices that result in a minimal residual disease (MRD) where few residual neoplastic cells undetected in vivo, replenish the cancer cell reservoir. This scenario, which is also shared with other cancer diseases, requires the development of strategies to advance in novel, selective targeting toward the tumorigenic cells that survive to the anticancer agents.

Methods

Here, we have taken advantage of the therapeutic properties of an idiotype specific peptide (pA20-36) that bind specifically to murine B-lymphoma cells in the setting of an anti cancer strategy, based on the selected delivery of electrostatic-based complex, peptide-siRNA. To this end, two engineered, arginine rich, peptides that included the pA20-36 targeting sequence were designed to bind fluorescent-labelled siRNA. One peptide presented 9 Arg at the C-terminal of pA20-36 whereas the other included 5 Arg at the N- and C-terminus, respectively.

Results

Compared to the control and random peptide-siRNA complexes, both pA20-36-siRNA complexes were endowed with the selective delivering of fluorescent-labelled siRNA toward the A20 murine B-cell lymphoma, as evaluated by cytofluorimetry and confocal microscopy, whereas fluorescent-labelled siRNA alone was not internalized in the selected cells. Compared to peptide controls, the use of the modified pA20-36 peptides complexed with siRNA anti-GAPDH and anti-Bcl2 showed a down-regulation in the expression levels of the corresponding genes.

Conclusions

Peptide-siRNA complex can be suitable tool for both selective peptide-driven cell targeting and gene silencing. In this setting, the improvement of this strategy is expected to provide a safe and non-invasive approach for the delivery of therapeutic molecules.

CRL3IBTK Regulates the Tumor Suppressor Pdcd4 through Ubiquitylation Coupled to Proteasomal Degradation

The human inhibitor of Bruton's tyrosine kinase isoform α (IBtkα) is a BTB protein encoded by the IBTK gene, which maps to chromosomal locus 6q14.1, a mutational hot spot in lymphoproliferative disorders. Here, we demonstrate that IBtkα forms a CRL3^IBTK complex promoting its self-ubiquitylation. We identified the tumor suppressor Pdcd4 as IBtkα interactor and ubiquitylation substrate of CRL3^IBTK for proteasomal degradation. Serum-induced degradation of Pdcd4 required both IBtkα and Cul3, indicating that CRL3^IBTK regulated the Pdcd4 stability in serum signaling. By promoting Pdcd4 degradation, IBtkα counteracted the suppressive effect of Pdcd4 on translation of reporter luciferase mRNAs with stem-loop structured or unstructured 5′-UTR. IBtkα depletion by RNAi caused Pdcd4 accumulation and decreased the translation of Bcl-xL mRNA, a well known target of Pdcd4 repression. By characterizing CRL3^IBTK as a novel ubiquitin ligase, this study provides new insights into regulatory mechanisms of cellular pathways, such as the Pdcd4-dependent translation of mRNAs.

Cancer-associated CD43 glycoforms as target of immunotherapy

CD43 is a sialoglycosylated membrane protein that is involved in cell proliferation and differentiation. CD43 glycoforms that are recognized by the UN1 monoclonal antibody (mAb) were expressed in lymphoblastoid T-cell lines and solid tumors, such as breast, colon, gastric, and squamous cell lung carcinomas, while unexpressed in the normal counterparts. The cancer association of UN1/CD43 epitope suggested the possibility to use the UN1 mAb for tumor diagnosis and therapy. In this study, we show that the UN1 mAb was endowed with antitumor activity in vivo because its passive transfer inhibited the growth of UN1-positive HPB-ALL lymphoblastoid T cells in mice. Furthermore, we demonstrate that tumor inhibition was due to UN1 mAb-dependent natural killer-mediated cytotoxicity. By screening a phage-displayed random peptide library, we identified the phagotope 2/165 as a mimotope of the UN1 antigen, as it harbored a peptide sequence that was specifically recognized by the UN1 mAb and inhibited the binding of the UN1 mAb to UN1-positive tumor cells. On the basis of sequence homology with the extracellular region of CD43 (amino acids 64 to 83), the 2/165 peptide sequence was likely mimicking the protein core of the UN1/CD43 epitope. When used as vaccine in mice, the 2/165 phagotope raised antibodies against the UN1/CD43 antigen, indicating that the 2/165 phagotope mimicked the UN1 antigen structure, and could represent a novel immunogen for cancer immunotherapy. These findings support the feasibility of using monoclonal antibodies to identify cancer-associated mimotopes for immunotherapy.

Eukaryotic Initiation Factor 4H Is under Transcriptional Control of p65/NF-κB

Protein synthesis is mainly regulated at the initiation step, allowing the fast, reversible and spatial control of gene expression. Initiation of protein synthesis requires at least 13 translation initiation factors to assemble the 80S ribosomal initiation complex. Loss of translation control may result in cell malignant transformation. Here, we asked whether translational initiation factors could be regulated by NF-κB transcription factor, a major regulator of genes involved in cell proliferation, survival, and inflammatory response. We show that the p65 subunit of NF-κB activates the transcription of eIF4H gene, which is the regulatory subunit of eIF4A, the most relevant RNA helicase in translation initiation. The p65-dependent transcriptional activation of eIF4H increased the eIF4H protein content augmenting the rate of global protein synthesis. In this context, our results provide novel insights into protein synthesis regulation in response to NF-κB activation signalling, suggesting a transcription-translation coupled mechanism of control.