Molecular studies on MYD88 alternative splicing in oncogenesis and Toll-like receptor 2 recognition of fungal chitin

Toll-like receptors (TLRs) play critical roles in human innate and adaptive immune responses and although they are well characterized, there remain gaps in our understanding of the early events upon TLR activation. Here I present two different topics: first the regulation and function of MyD88 alternative splicing in B cell lymphomas and second, the role of the receptor TLR2 in the recognition of the very abundant natural agonist chitin. First topic: MyD88, a pivotal signaling protein for almost all TLRs, has been determined as an oncogenic driver in numerous cancers especially in Non-Hodgkin B cell lymphomas (B-NHL), and on the other hand, it has been found that the MyD88 gene undergoes alternative splicing. To date, five MyD88 isoforms were found in transcriptional analyses, but little is known about their natural occurrence and abundance in specific cell types. Furthermore, alternative splicing is often aberrant in cancers, resulting in novel protein isoforms which could originate or aid oncogenesis. In the present study, I evaluated the hypothesis that MyD88 alternatively spliced isoforms could be more highly expressed in B-NHL and might contribute to the well-studied oncogenic effect of MyD88. Second topic: Chitin is the second most abundant polysaccharide in nature and has been linked to fungal infection and allergic asthma. To date, several different receptors have been proposed to recognize chitin and evoke an inflammatory response. However, literature presents contradictory results and the physical binding of immune receptors to chitin has not been shown. Colleagues and I speculated that the discrepancies might be due to chitin’s highly polymeric nature and the use of crude extracts from crustaceans or fungi with variable purity as chitin preparations. Thus, we propose to use defined chitin (N-acetyl-glucosamine) oligomers comprising 4 to 15 subunits to overcome these limitations and identify the still unknown chitin-receptor

Interleukin-1 receptor-associated kinase 4 (IRAK4) plays a dual role in myddosome formation and Toll-like receptor signaling

Toll-like receptors (TLRs) form part of the host innate immune system, in which they act as sensors of microbial and endogenous danger signals. Upon TLR activation, the intracellular Toll/interleukin-1 receptor domains of TLR dimers initiate oligomerization of a multiprotein signaling platform comprising myeloid differentiation primary response 88 (MyD88) and members of the interleukin-1 receptor-associated kinase (IRAK) family. Formation of this myddosome complex initiates signal transduction pathways, leading to the activation of transcription factors and the production of inflammatory cytokines. To date, little is known about the assembly and disassembly of the myddosome and about the mechanisms by which these complexes mediate multiple downstream signaling pathways. Here, we isolated myddosome complexes from whole-cell lysates of TLR-activated primary mouse macrophages and from IRAK reporter macrophages to examine the kinetics of myddosome assembly and disassembly. Using a selective inhibitor of IRAK4\u27s kinase activity, we found that whereas TLR cytokine responses were ablated, myddosome formation was stabilized in the absence of IRAK4\u27s kinase activity. Of note, IRAK4 inhibition had only a minimal effect on NF-kappaB and mitogen-activated protein kinase (MAPK) signaling. In summary, our results indicate that IRAK4 has a critical scaffold function in myddosome formation and that its kinase activity is dispensable for myddosome assembly and activation of the NF-kappaB and MAPK pathways but is essential for MyD88-dependent production of inflammatory cytokines. Our findings suggest that the scaffold function of IRAK4 may be an attractive target for treating inflammatory and autoimmune diseases

HLA class I-restricted MYD88 L265P-derived peptides as specific targets for lymphoma immunotherapy

Genome sequencing has uncovered an array of recurring somatic mutations in different non-Hodgkin lymphoma (NHL) subtypes. If affecting protein-coding regions, such mutations may yield mutation-derived peptides that may be presented by HLA class I proteins and recognized by cytotoxic T cells. A recurring somatic and oncogenic driver mutation of the Toll-like receptor adaptor protein MYD88, Leu265Pro (L265P) was identified in up to 90% of different NHL subtype patients. We therefore screened the potential of MYD88(L265P)-derived peptides to elicit cytotoxic T cell responses as tumor-specific neoantigens. Based on in silico predictions, we identified potential MYD88(L265P)-containing HLA ligands for several HLA class I restrictions. A set of HLA class I MYD88(L265P)-derived ligands elicited specific cytotoxic T cell responses for HLA-B*07 and -B*15. These data highlight the potential of MYD88(L265P) mutation-specific peptide-based immunotherapy as a novel personalized treatment approach for patients with MYD88(L265P+) NHLs that may complement pharmacological approaches targeting oncogenic MyD88 L265P signaling

Oncogenic MYD88 mutations in lymphoma: novel insights and therapeutic possibilities

Oncogenic MYD88 mutations, most notably the Leu 265 Pro (L265P) mutation, were recently identified as potential driver mutations in various B-cell non-Hodgkin Lymphomas (NHLs). The L265P mutation is now thought to be common to virtually all NHLs and occurs in between 4 and 90% of cases, depending on the entity. Since it is tumor-specific, the mutation, and the pathways it regulates, might serve as advantageous therapeutic targets for both conventional chemotherapeutic intervention, as well as immunotherapeutic strategies. Here, we review recent progress on elucidating the molecular and cellular processes affected by theL265P mutation of MYD88, describe a new in vivo model for MyD88 L265P-mediated oncogenesis, and summarize how these findings could be exploited therapeutically by specific targeting of signaling pathways. In addition, we summarize current and explore future possibilities for conceivable immunotherapeutic approaches, such as L265P-derived peptide vaccination, adoptive transfer of L265P-restricted T cells, and use of T-cell receptor-engineered T cells. With clinical trials regarding their efficacy rapidly expanding to NHLs, we also discuss potential combinations of immune checkpoint inhibitors with the described targeted chemotherapies of L265P signaling networks, and/or with the above immunological approaches as potential ways of targeting MYD88-mutated lymphomas in the future

Use of Secondary Iliac Branch Devices after Previous Endovascular Abdominal and Thoraco-Abdominal Aortic Aneurysm Repair

Objective: To assess the safety and effectiveness of iliac branch devices (IBDs), as secondary procedure, for the treatment of type Ib endoleak or evolution of iliac artery disease after prior endovascular aortic repair (EVAR) for thoraco-abdominal (TAAAs) or abdominal aortic aneurysms (AAAs). Methods: A multicentre observational study of three European centres. The study included 75 patients (age 71 + 9 years, 96% men) with previous EVAR (n = 64, 85%) or fenestrated or branched (FB) EVAR (n = 11, 15%). Overall, 88 IBDs were implanted to treat aneurysmal iliac artery evolution in 40 (53%) and type Ib endoleak in 35 (47%) cases, respectively. Thirteen (17%) patients received bilateral IBDs. Internal iliac artery (IIA) catheterisation was done through a transaxillary access (n = 82, 93%) or up and over (n = 6, 7%) technique. The primary endpoint was technical success. Secondary endpoints were 30 day major adverse event, early and long term freedom from re-intervention and target vessel instability. Results: All procedures were technically successful (100%). During hospitalisation, there were four (5%) major adverse events and three (4%) early re-interventions, but no death, stroke, or damage to previous endografts. The median follow up was 47 (interquartile range 42) months, and the five year survival rate was 78 + 6% with no aortic related death. Cox's regression analysis showed pre-operative renal function impairment (hazard ratio [HR] 3.4; 95% confidence interval [CI] 1.1 -10.1; p = .033), and primary TAAA repair (HR 6.1; 95% CI 1.6-22.3; p = .006) as independent factors for long term mortality. Freedom from re-interventions was 85 + 4% at five years with 11 (12%) cases (five endoleaks, four IBD thromboses, two stenoses). IIA instability was reported in three (3%) limbs and freedom from IIA instability was 95 + 3% after 60 months. Conclusion: Secondary IBD after EVAR is a safe and effective procedure with high technical success and low complication rates. The technique of choice to revascularise the IIA seems not to affect early and follow up results. Long term durability of IBD repair is acceptable with low rates of IIA re-intervention