Inhibition of IL-6-dependent growth of myeloma cells by an acidic peptide repressing the gp130-mediated activation of Src family kinases

Endocytosis of pro-inflammatory cytokine receptors and its relevance for signal transduction

The pro-inflammatory cytokines tumor necrosis factor (TNF), interleukin-1 (IL-1) and interleukin-6 (IL-6) are key players of the innate and adaptive immunity. Their activity needs to be tightly controlled to allow the initiation of an appropriate immune response as defense mechanism against pathogens or tissue injury. Excessive or sustained signaling of either of these cytokines leads to severe diseases, including rheumatoid arthritis, inflammatory bowel diseases (Crohn's disease, ulcerative colitis), steatohepatitis, periodic fevers and even cancer. Studies carried out in the last 30 years have emphasized that an elaborate control system for each of these cytokines exists. Here, we summarize what is currently known about the involvement of receptor endocytosis in the regulation of these pro-inflammatory cytokines' signaling cascades. Particularly in the last few years it was shown that this cellular process is far more than a mere feedback mechanism to clear cytokines from the circulation and to shut off their signal transduction.

Recombinant soluble gp130 protein reduces DEN-induced primary hepatocellular carcinoma in mice

IL-6 (interleukin 6) plays an important role in the development and growth of hepatocellular carcinoma (HCC) via both classic signaling and trans-signaling pathways. Soluble gp130 (sgp130) is known to be a natural inhibitor of the trans-signaling pathway. In the present study, our goal was to investigate whether recombinant sgp130 could suppress the initiation and progression of HCC in mouse models. Our results demonstrate that sgp130 induced an apoptosis of HepG2 cells and inhibited the clonogenicity of HepG2 in vitro. Moreover, the IL-6 trans-signaling pathway is significantly suppressed by sgp130 as reflected by the decrease in the level of STAT3 phosphorylation and other inflammatory factors both in vitro and in vivo. In the DEN-induced HCC mouse model, intravenous injection of sgp130 attenuated hepatic fibrosis at 16 weeks and reduced the initiation and progression of primary HCC at 36 weeks. Furthermore, our results also demonstrate that intravenous administration of sgp130 significantly suppressed the growth and metastasis of xenograft human HCC in NOD/SCID mice.

Hematopoietic cell kinase (HCK) as a therapeutic target in immune and cancer cells

The hematopoietic cell kinase (HCK) is a member of the SRC family of cytoplasmic tyrosine kinases (SFKs), and is expressed in cells of the myeloid and B-lymphocyte cell lineages. Excessive HCK activation is associated with several types of leukemia and enhances cell proliferation and survival by physical association with oncogenic fusion proteins, and with functional interactions with receptor tyrosine kinases. Elevated HCK activity is also observed in many solid malignancies, including breast and colon cancer, and correlates with decreased patient survival rates. HCK enhances the secretion of growth factors and pro-inflammatory cytokines from myeloid cells, and promotes macrophage polarization towards a wound healing and tumor-promoting alternatively activated phenotype. Within tumor associated macrophages, HCK stimulates the formation of podosomes that facilitate extracellular matrix degradation, which enhance immune and epithelial cell invasion. By virtue of functional cooperation between HCK and bona fide oncogenic tyrosine kinases, excessive HCK activation can also reduce drug efficacy and contribute to chemo-resistance, while genetic ablation of HCK results in minimal physiological consequences in healthy mice. Given its known crystal structure, HCK therefore provides an attractive therapeutic target to both, directly inhibit the growth of cancer cells, and indirectly curb the source of tumor-promoting changes in the tumor microenvironment.

Preclinical validation of interleukin 6 as a therapeutic target in multiple myeloma

Studies on the biologic and molecular genetic underpinnings of multiple myeloma (MM) have identified the pleiotropic, pro-inflammatory cytokine, interleukin-6 (IL-6), as a factor crucial to the growth, proliferation and survival of myeloma cells. IL-6 is also a potent stimulator of osteoclastogenesis and a sculptor of the tumor microenvironment in the bone marrow of patients with myeloma. This knowledge has engendered considerable interest in targeting IL-6 for therapeutic purposes, using a variety of antibody- and small-molecule-based therapies. However, despite the early recognition of the importance of IL-6 for myeloma and the steady progress in our knowledge of IL-6 in normal and malignant development of plasma cells, additional efforts will be required to translate the promise of IL-6 as a target for new myeloma therapies into significant clinical benefits for patients with myeloma. This review summarizes published research on the role of IL-6 in myeloma development and describes ongoing efforts by the University of Iowa Myeloma Multidisciplinary Oncology Group to develop new approaches to the design and testing of IL-6-targeted therapies and preventions of MM.

Interleukin-6 is associated with steroid resistance and reflects disease activity in severe pediatric ulcerative colitis

BACKGROUND AND AIM

Approximately one third of patients with acute severe ulcerative colitis (ASC) will fail intravenous corticosteroids (IVCS). Predicting response to IVCS to initiate early salvage therapy remains challenging. The aim of this study was to evaluate the role of serum inflammatory cytokines in ASC and determine their predictive utility with IVCS treatment failure.

METHODS

This preplanned ancillary study, part of the prospective multicenter OSCI study, evaluated pediatric ASC in North America. Serum samples were obtained from 79 children admitted for ASC on the third day of IVCS treatment. Twenty-three (29%) patients required second-line therapy. ELISA-based cytokine arrays were used [TNF-α, IFN-γ, interleukin (IL)-1β, IL-2, IL-4, IL-5, IL-6, IL-8, IL-10, IL-12, IL-13, and IL-17], selected based on a systematic literature search.

RESULTS

In univariate analysis, only IL-6 was significantly different between responders and non-responders (P=0.003). The risk for IVCS failure increased by 40% per each pg/mL increase in IL-6 level. Factor analysis found IL-6 to be associated with IL-17, suggesting involvement of the T-helper (TH)17 pathway. In a multivariate analysis, disease activity [judged by the Pediatric UC Activity Index (PUCAI)] assumed all the association with the treatment outcome while IL-6 was no longer significant (P=0.32; PUCAI score P<0.001).

CONCLUSIONS

While IL-6 strongly predicted IVCS failure, it likely reflects disease activity and not direct interference with corticosteroid pathway. Nonetheless, IL-6 levels may have a role in predicting IVCS response in severe pediatric UC for treatment decision-making or potentially in medical intervention by virtue of anti-IL-6 antibodies in severe UC.

Environmental-mediated drug resistance: a target for multiple myeloma therapy

Multiple myeloma is an incurable malignancy of mature clonal B cells. The refractory nature of this disease has long been attributed to the acquisition of drug resistance. Traditionally, mechanisms of drug resistance have been defined by genetic, acquired changes in the expression or function of specific genes products. However, over the past 10 years a large body of evidence has emerged demonstrating that in addition to mechanisms of drug resistance intrinsic to the cancer cell, there exist dynamic, de novo mechanisms coordinated by the tumor microenvironment resulting in a environmental-mediated drug resistance (EM-DR). Within this review we will provide an overview of some of these mechanisms of drug resistance and how they contribute to minimal residual disease and subsequent treatment failure. By understanding mechanisms of EM-DR, therapeutic targets can be identified and interventions designed to reduce minimal residual disease and improve clinical outcomes.

Src-family and Syk kinases in activating and inhibitory pathways in innate immune cells: signaling cross talk

The response of innate immune cells to growth factors, immune complexes, extracellular matrix proteins, cytokines, pathogens, cellular damage, and many other stimuli is regulated by a complex net of intracellular signal transduction pathways. The majority of these pathways are either initiated or modulated by Src-family or Syk tyrosine kinases present in innate cells. The Src-family kinases modulate the broadest range of signaling responses, including regulating immunoreceptors, C-type lectins, integrins, G-protein-coupled receptors, and many others. Src-family kinases also modulate the activity of other kinases, including the Tec-family members as well as FAK and Pyk2. Syk kinase is required for initiation of signaling involving receptors that utilize immunoreceptor tyrosine activation (ITAM) domains. This article reviews the major activating and inhibitory signaling pathways regulated by these cytoplasmic tyrosine kinases, illuminating the many examples of signaling cross talk between pathways.

Disruption of Src function potentiates Chk1-inhibitor-induced apoptosis in human multiple myeloma cells in vitro and in vivo

Ras/MEK/ERK pathway activation represents an important compensatory response of human multiple myeloma (MM) cells to checkpoint kinase 1 (Chk1) inhibitors. To investigate the functional roles of Src in this event and potential therapeutic significance, interactions between Src and Chk1 inhibitors (eg, UCN-01 or Chk1i) were examined in vitro and in vivo. The dual Src/Abl inhibitors BMS354825 and SKI-606 blocked Chk1-inhibitor-induced extracellular signal-regulated kinase 1/2 (ERK1/2) activation, markedly increasing apoptosis in association with BimEL up-regulation, p34(cdc2) activation, and DNA damage in MM cell lines and primary CD138(+) MM samples. Loss-of-function Src mutants (K297R, K296R/Y528F) or shRNA knock-down of Src prevented the ERK1/2 activation induced by Chk1 inhibitors and increased apoptosis. Conversely, constitutively active Ras or mitogen-activated protein kinase/ERK kinase 1 (MEK1) significantly diminished the ability of Src inhibitors to potentiate Chk1-inhibitor lethality. Moreover, Src/Chk1-inhibitor cotreatment attenuated MM-cell production of vascular endothelial growth factor and other angiogenic factors (eg, ANG [angiogenin], TIMP1/2 [tissue inhibitor of metalloproteinases 1/2], and RANTES [regulated on activation normal T-cell expressed and secreted]), and inhibited in vitro angiogenesis. Finally, coadministration of BMS354825 and UCN-01 suppressed human MM tumor growth in a murine xenograft model, increased apoptosis, and diminished angiogenesis. These findings suggest that Src kinase is required for Chk1-inhibitor-mediated Ras → ERK1/2 signaling activation, and that disruption of this event sharply potentiates the anti-MM activity of Chk1 inhi-bitors in vitro and in vivo.

Anaplastic plasmacytomas: relationships to normal memory B cells and plasma cell neoplasms of immunodeficient and autoimmune mice

Anaplastic plasmacytomas (APCTs) from NFS.V(+) congenic mice and pristane-induced plasmacytic PCTs from BALB/c mice were previously shown to be histologically and molecularly distinct subsets of plasma cell neoplasms (PCNs). Here we extended these comparisons, contrasting primary APCTs and PCTs by gene expression profiling in relation to the expression profiles of normal naïve, germinal centre, and memory B cells and plasma cells. We also sequenced immunoglobulin genes from APCT and APCT-derived cell lines and defined surface phenotypes and chromosomal features of the cell lines by flow cytometry and by spectral karyotyping and fluorescence in situ hybridization. The results indicate that APCTs share many features with normal memory cells and the plasma cell-related neoplasms (PLs) of FASL-deficient mice, suggesting that APCTs and PLs are related and that both derive from memory B cells. Published in 2010 by John Wiley & Sons, Ltd.

IL-6 and MYC collaborate in plasma cell tumor formation in mice

Interleukin-6 (IL-6) plays a critical role in the natural history of human plasma cell neoplasms (PCNs), such as plasma cell myeloma and plasmacytoma (PCT). IL-6 is also at the center of neoplastic plasma cell transformation in BALB/c (C) mice carrying a transgene, H2-L(d)-IL6, that encodes human IL-6 under control of the major histocompatibility complex H2-L(d) promoter: strain C.H2-L(d)-IL6. These mice are prone to PCT, but tumor development is incomplete with long latencies ( approximately 40% PCT at 12 months of age). To generate a more robust mouse model of IL-6-dependent PCN, we intercrossed strain C.H2-L(d)-IL6 with strains C.iMyc(Emu) or C.iMyc(Calpha), 2 interrelated gene-insertion models of the chromosomal T(12;15) translocation causing deregulated expression of Myc in mouse PCT. Deregulation of MYC is also a prominent feature of human PCN. We found that double-transgenic C.H2-L(d)-IL6/iMyc(Emu) and C.H2-L(d)-IL6/iMyc(Calpha) mice develop PCT with full penetrance (100% tumor incidence) and short latencies (3-6 months). The mouse tumors mimic molecular hallmarks of their human tumor counterparts, including elevated IL-6/Stat3/Bcl-X(L) signaling. The newly developed mouse strains may provide a good preclinical research tool for the design and testing of new approaches to target IL-6 in treatment and prevention of human PCNs.

The kinase inhibitor dasatinib induces apoptosis in chronic lymphocytic leukemia cells in vitro with preference for a subgroup of patients with unmutated IgVH genes

Src family kinases (SFKs) were described to be overexpressed in chronic lymphocytic leukemia (CLL). We wished to examine the effects of the Src and Abl kinase inhibitor dasatinib on the intracellular signaling and survival of CLL cells. Dasa-tinib showed a dose- and time-dependent reduction of global tyrosine phosphorylation and of activating phosphotyrosine levels of SFKs. Treatment with 100 nM dasatinib led to decreased levels of the activated, phosphorylated forms of Akt, Erk1/2, and p38, and induced PARP cleavage through caspase activity. In Mec1 and JVM-3 cell lines, dasatinib increased p53 protein levels and inhibited proliferation. In freshly isolated CLL cells, dasatinib reduced the expression of Mcl-1 and Bcl-x(L). Combination of 5 microM dasatinib and fludarabine increased the apoptosis induction of each by approximately 50%. In 15 primary CLL samples, cells with unmutated immunoglobulin variable heavy chain (IgV(H)) genes were more sensitive to dasatinib than those with mutated IgV(H) genes (P = .002). In summary, dasatinib shows potent inhibitory effects on the survival of CLL cells in vitro, most prominently in samples obtained from patients with unfavorable prognostic features.

Validation of PDGFRbeta and c-Src tyrosine kinases as tumor/vessel targets in patients with multiple myeloma: preclinical efficacy of the novel, orally available inhibitor dasatinib

Inhibition of multiple myeloma (MM) plasma cells in their permissive bone marrow microenvironment represents an attractive strategy for blocking the tumor/vessel growth associated with the disease progression. However, target specificity is an essential aim of this approach. Here, we identified platelet-derived growth factor (PDGF)-receptor beta (PDGFRbeta) and pp60c-Src as shared constitutively activated tyrosine-kinases (TKs) in plasma cells and endothelial cells (ECs) isolated from MM patients (MMECs). Our cellular and molecular dissection showed that the PDGF-BB/PDGFRbeta kinase axis promoted MM tumor growth and vessel sprouting by activating ERK1/2, AKT, and the transcription of MMEC-released proangiogenic factors, such as vascular endothelial growth factor (VEGF) and interleukin-8 (IL-8). Interestingly, pp60c-Src TK-activity was selectively induced by VEGF in MM tumor and ECs, and the use of small-interfering (si)RNAs validated pp60c-Src as a key signaling effector of VEGF loop required for MMEC survival, migration, and angiogenesis. We also assessed the antitumor/vessel activity of dasatinib, a novel orally bioactive PDGFRbeta/Src TK-inhibitor that significantly delayed MM tumor growth and angiogenesis in vivo, showing a synergistic cytotoxicity with conventional and novel antimyeloma drugs (ie, melphalan, prednisone, bor-tezomib, and thalidomide). Overall data highlight the biologic and therapeutic relevance of the combined targeting of PDGFRbeta/c-Src TKs in MM, providing a framework for future clinical trials.

The diverse functions of Src family kinases in macrophages

Macrophages are key components of the innate immune response. These cells possess a diverse repertoire of receptors that allow them to respond to a host of external stimuli including cytokines, chemokines, and pathogen-associated molecules. Signals resulting from these stimuli activate a number of macrophage functional responses such as adhesion, migration, phagocytosis, proliferation, survival, cytokine release and production of reactive oxygen and nitrogen species. The cytoplasmic tyrosine kinase Src and its family members (SFKs) have been implicated in many intracellular signaling pathways in macrophages, initiated by a diverse set of receptors ranging from integrins to Toll-like receptors. However, it has been difficult to implicate any given member of the family in any specific pathway. SFKs appear to have overlapping and complementary functions in many pathways. Perhaps the function of these enzymes is to modulate the overall intracellular signaling network in macrophages, rather than operating as exclusive signaling switches for defined pathways. In general, SFKs may function more like rheostats, influencing the amplitude of many pathways.

DNMT3A and DNMT3B mediate autocrine hGH repression of plakoglobin gene transcription and consequent phenotypic conversion of mammary carcinoma cells

Directed by microarray analyses, we report that autocrine human growth hormone (hGH) increased the mRNA and protein expression of DNA methyltransferase 1 (DNMT1), DNMT3A and DNMT3B in mammary carcinoma cells. Autocrine hGH stimulation of DNMT3A and DNMT3B expression was mediated by JAK2 and Src kinases, and treatment of mammary carcinoma cells with the DNMT inhibitor, 5'-aza-2'-deoxycytidine (AZA), abrogated autocrine hGH-stimulated cellular proliferation, apoptosis and anchorage-independent growth. AZA reversed the epitheliomesenchymal transition of mammary carcinoma cells induced by autocrine hGH, to an epithelioid morphology and abrogated cell migration stimulated by autocrine hGH. Autocrine hGH-stimulated hypermethylation of the first exon of the PLAKOGLOBIN gene and AZA abrogated the ability of autocrine hGH to repress plakoglobin gene transcription. Small interfering RNA (siRNA)-mediated depletion of the individual DNMT molecules did not release autocrine hGH repression of PLAKOGLOBIN promoter activity nor did individual DNMT depletion affect autocrine hGH-stimulated migration. However, concomitant siRNA-mediated depletion of both DNMT3A and DNMT3B abrogated hypermethylation of the PLAKOGLOBIN gene stimulated by autocrine hGH and subsequent repression of plakoglobin gene transcription and increased cell migration. Thus, the autocrine hGH-stimulated increases in DNMT3A and DNMT3B expression mediate repression of plakoglobin gene transcription by direct hypermethylation of its promoter and consequent phenotypic conversion of mammary carcinoma cells. Autocrine hGH, therefore, utilizes DNA methylation as a mechanism to exert its oncogenic effects in mammary carcinoma cells.