quantitative-mass-spectrometric-profiling-cancer-cell-proteomes

Quantitative Mass Spectrometric Profiling of Cancer-cell Proteomes Derived From Liquid and Solid Tumors

In-depth analyses of cancer cell proteomes are needed to elucidate oncogenic pathomechanisms, as well as to identify potential drug targets and diagnostic ...

University Medical Center, Göttingen

Topical ketoprofen (KP) is widely used because of its anti-inflammatory effect. Parallel with its popular usage, the number of reported cases of ketoprofen-induced photoallergic contact dermatitis has increased. A review of the literature was made to evaluate the spectrum of cross sensitization in patients with ketoprofen-induced photoallergic contact dermatitis using ketoprofen and other structurally similar chemicals and sunscreens, fragrance components, as well as the presence of prolonged photosensitivity related to it. Furthermore, the distinction between true cross-reactivity and concomitant sensitization may be difficult. Therefore, further investigations are needed to gain a more complete understanding of this important topic. This article also reviews some patents related to alternative treatment of musculoskeletal diseases and/or treatment of allergic reactions due to NSAIDs use.

Ketoprofen allergic reactions.

Spleen tyrosine kinase Syk provides critical transducer functions for a number of immune cell receptors and has been implicated in the generation of several forms of leukemias. Catalytic activity and the ability of Syk to interact with other signaling elements depend on the phosphorylation status of Syk. We have now identified and quantified the full spectrum of phosphoacceptor sites in human Syk as well as the interactome of Syk in resting and activated B cells by high-resolution mass spectrometry. While the majority of inducible phosphorylations occurred on tyrosine residues, one of the most frequently detected phosphosites encompassed serine 297 located within the linker insert distinguishing the long and short isoforms of Syk. Full-length Syk can associate with more than 25 distinct ligands including the 14-3-3γ adaptor protein, which binds directly to phosphoserine 297. The latter complex attenuates inducible plasma membrane recruitment of Syk, thereby limiting antigen receptor-proximal signaling pathways. Collectively, the established ligand library provides a basis to understand the complexity of the Syk signaling network.

Complex phosphorylation dynamics control the composition of the Syk interactome in B cells.

Spleen tyrosine kinase Syk and its substrate SLP65 (also called BLNK) are proximal signal transducer elements of the B-cell antigen receptor (BCR). Yet, our understanding of signal initiation and processing is limited owing to the incomplete list of SLP65 interaction partners and our ignorance of their association kinetics. We have now determined and quantified the in vivo interactomes of SLP65 in resting and stimulated B cells by mass spectrometry. SLP65 orchestrated a complex signal network of about 30 proteins that was predominantly based on dynamic interactions. However, a stimulation-independent and constant association of SLP65 with the Cbl-interacting protein of 85 kDa (CIN85) was requisite for SLP65 phosphorylation and its inducible plasma membrane translocation. In the absence of a steady SLP65/CIN85 complex, BCR-induced Ca(2+) and NF-κB responses were abrogated. Finally, live cell imaging and co-immunoprecipitation experiments further confirmed that both SLP65 and CIN85 are key components of the BCR-associated primary transducer module required for the onset and progression phases of BCR signal transduction.

The B-cell antigen receptor signals through a preformed transducer module of SLP65 and CIN85.

Recruitment of the growth factor receptor-bound protein 2 (Grb2) by the plasma membrane-associated adapter protein downstream of kinase 3 (Dok-3) attenuates signals transduced by the B cell antigen receptor (BCR). Here we describe molecular details of Dok-3/Grb2 signal integration and function, showing that the Lyn-dependent activation of the BCR transducer kinase Syk is attenuated by Dok-3/Grb2 in a site-specific manner. This process is associated with the SH3 domain-dependent translocation of Dok-3/Grb2 complexes into BCR microsignalosomes and augmented phosphorylation of the inhibitory Lyn target SH2 domain-containing inositol 5' phosphatase. Hence, our findings imply that Dok-3/Grb2 modulates the balance between activatory and inhibitory Lyn functions with the aim to adjust BCR signaling efficiency.

The Dok-3/Grb2 protein signal module attenuates Lyn kinase-dependent activation of Syk kinase in B cell antigen receptor microclusters.

Spleen tyrosine kinase (Syk) induces cell survival and proliferation in a high proportion of acute myeloid leukemia (AML) blasts, but the underlying molecular events of Syk signaling have not been investigated. Proteomic techniques have allowed us to identify the multiprotein complex that is nucleated by constitutively active Syk in AML cells. This complex differs from the B-lymphoid Syk interactome with respect to several proteins, especially the integrin receptor Mac-1, the Fc-γ receptor I (FcγRI), and the transcription factors STAT3 and STAT5. We show in several AML cell line models that tonic signals derived from the Fc-γ chain lead to Syk-dependent activation of STAT3 and STAT5, which in turn induces cell survival and proliferation. Moreover, stimulation of Mac-1 or FcγRI intensifies the constitutive Syk-mediated STAT3/5 activation in AML cells, a scenario likely to take place in the bone marrow niche. In accordance with these findings, we observed that β2 integrins, including Mac-1, trigger proliferation of AML cells in an AML cell/stroma coculture model. Taken together, we identified an oncogenic integrin/Syk/STAT3/5 signaling axis that might serve as a therapeutic target of AML in the future.

β2 integrin-derived signals induce cell survival and proliferation of AML blasts by activating a Syk/STAT signaling axis.

This clinical report deals with a giant true pulmonary venous aneurysm, which was partially thrombosed. The overall incidence of pulmonary venous aneurysms is unknown, and they are reported only occasionally. We present the case of a previously healthy man with acute onset of ischemic cerebral stroke. The cause was a thrombus in a huge aneurysm of the left superior pulmonary vein. The patient subsequently underwent uncomplicated therapy for stroke, including thrombolysis followed by excision of the giant pulmonary venous aneurysm. As curative therapy we recommend complete resection of this rare entity.

Aneurysm of the pulmonary vein: an unusual cause of stroke.

Acute myeloid leukemia (AML) is driven by niche-derived and cell-autonomous stimuli. While many cell-autonomous disease drivers are known, niche-dependent signaling in the context of the genetic disease heterogeneity has been difficult to investigate. Here, we analyzed the role of Bruton's tyrosine kinase (BTK) in AML. BTK was frequently expressed and its inhibition strongly impaired the proliferation and survival of AML cells - also in the presence of bone marrow stroma. By interactome analysis, (phospho)proteomics and transcriptome sequencing, we characterized BTK signaling networks. We show that BTK-dependent signaling is highly context-dependent. In FLT3-ITD-positive AML, BTK mediates FLT3-ITD-dependent Myc- and STAT5 activation and combined targeting of FLT3-ITD and BTK showed additive effects. In FLT3-ITD-negative AML, BTK couples Toll-like receptor 9 (TLR9) activation to NFκB and STAT5. Both BTK-dependent transcriptional programs were relevant for cell cycle progression and apoptosis regulation. Thus, we identify context-dependent oncogenic driver events that may guide subtype-specific treatment strategies and point for the first time to a role of TLR9 in AML. Clinical evaluation of BTK inhibitors in AML seems warranted.

Hanibal Bohnenberger

Institute of Pathology

University Medical Center, Göttingen

Quantitative Mass Spectrometric Profiling of Cancer-cell Proteomes Derived From Liquid and Solid Tumors