Axl kinase drives immune checkpoint and chemokine signalling pathways in lung adenocarcinomas

Axl receptor tyrosine kinase is involved in the growth and metastasis and is an indicator of poor prognosis in several cancers including lung cancers. Although a mitogen-activated protein kinase (MAPK) pathway and an epithelial-to-mesenchymal transition (EMT) program are critical, molecular mechanisms underlying the Axl-driven cancer progression have not been fully elucidated. We aimed to identify molecules up-regulated by Axl kinase in lung adenocarcinomas. Through the global gene expression analysis and the functional annotation clustering, we found that AXL expression positively correlated with mRNA expressions of immune checkpoint molecules and chemokine receptors in non-small-cell lung cancers. Validation cohorts including our biobank confirmed that the AXL expression significantly correlated with expression of genes encoding programmed death-ligand1 (PD-L1) and CXC chemokine receptor 6 (CXCR6) in lung adenocarcinoma, especially in epidermal growth factor receptor (EGFR) mutation-positive adenocarcinoma. Pharmacological inhibition of Axl kinase activity decreased mRNA expressions of PD-L1 and CXCR6 in EGFR mutation-positive cell lines. Our data indicates the novel role of Axl kinase as a driver of immune checkpoint molecules and chemokine signalling pathways in the progression of lung adenocarcinomas. This study also highlights the necessity of clinical trials in order to test the efficacy of Axl kinase inhibition in the Axl-highly expressing subset of lung adenocarcinomas. 

An integrative systems approach identifies novel candidates in Marfan syndrome-related pathophysiology

Marfan syndrome (MFS) is an autosomal dominant genetic disorder caused by mutations in the FBN1 gene. Although many peripheral tissues are affected, aortic complications, such as dilation, dissection and rupture, are the leading causes of MFS‐related mortality. Aberrant TGF‐beta signalling plays a major role in the pathophysiology of MFS. However, the contributing mechanisms are still poorly understood. Here, we aimed at identifying novel aorta‐specific pathways involved in the pathophysiology of MFS. For this purpose, we employed the Fbn1 under‐expressing mgR/mgR mouse model of MFS. We performed RNA‐sequencing of aortic tissues of 9‐week‐old mgR/mgR mice compared with wild‐type (WT) mice. With a false discovery rate <5%, our analysis revealed 248 genes to be differentially regulated including 20 genes previously unrelated with MFS‐related pathology. Among these, we identified Igfbp2, Ccl8, Spp1, Mylk2, Mfap4, Dsp and H19. We confirmed the expression of regulated genes by quantitative real‐time PCR. Pathway classification revealed transcript signatures involved in chemokine signalling, cardiac muscle contraction, dilated and hypertrophic cardiomyopathy. Furthermore, our immunoblot analysis of aortic tissues revealed altered regulation of pSmad2 signalling, Perk1/2, Igfbp2, Mfap4, Ccl8 and Mylk2 protein levels in mgR/mgR vs WT mice. Together, our integrative systems approach identified several novel factors associated with MFS‐aortic‐specific pathophysiology that might offer potential novel therapeutic targets for MFS.

HCV modifies EGF signalling and upregulates production of CXCR2 ligands: Role in inflammation and antiviral immune response

BACKGROUND & AIMS

To affect immune response and inflammation, the hepatitis C virus (HCV) substantially influences intercellular communication pathways that are decisive for immune cell recruitment. The present study investigates mechanisms by which HCV modulates chemokine-mediated intercellular communication from infected cells.

METHODS

Chemokine expression was studied in HCV_cc-infected cell lines or cell lines harbouring a subgenomic replicon, as well as in serum samples from patients. Expression or activity of mediators and signalling intermediates was manipulated using knockdown approaches or specific inhibitors.

RESULTS

HCV enhances expression of CXCR2 ligands in its host cell via the induction of epidermal growth factor (EGF) production. Knockdown of EGF or of the p65 subunit of the NF-κB complex results in a substantial downregulation of HCV-induced CXCR2 ligand expression, supporting the involvement of an EGF-dependent mechanism as well as activation of NF-κB. Furthermore, HCV upregulates expression of CXCR2 ligands in response to EGF stimulation via downregulation of the T-cell protein tyrosine phosphatase (TC-PTP [PTPN2]), activation of NF-κB, and enhancement of EGF-inducible signal transduction via MEK1 (MAP2K1). This results in the production of a cytokine/chemokine pattern by the HCV-infected cell that can recruit neutrophils but not monocytes.

CONCLUSIONS

These data reveal a novel EGF-dependent mechanism by which HCV influences chemokine-mediated intercellular communication. We propose that this mechanism contributes to modulation of the HCV-induced inflammation and the antiviral immune response.

LAY SUMMARY

In most cases hepatitis C virus (HCV) results in chronic infection and persistent viral replication, taking decades until development of overt disease. To achieve such a course, the respective virus must have developed mechanisms to circumvent antiviral response, to modulate the inflammatory response and to utilise the infrastructure of its host with moderate effect on its viability. The present study provides novel data indicating that HCV induces epidermal growth factor production in its host cell, enhancing epidermal growth factor-inducible expression of chemokines that bind to the CXCR2 receptor and recruit neutrophile granulocytes. Importantly, chemokines are critical mediators determining the pattern of immune cells recruited to the site of injury and thereby the local inflammatory and immunological milieu. These data strongly suggest that HCV triggers mechanisms that enable the virus to influence the inflammatory and immunological processes of its host.

HIV integration and the establishment of latency in CCL19-treated resting CD4(+) T cells require activation of NF-κB

Background

Eradication of HIV cannot be achieved with combination antiretroviral therapy (cART) because of the persistence of long-lived latently infected resting memory CD4⁺ T cells. We previously reported that HIV latency could be established in resting CD4⁺ T cells in the presence of the chemokine CCL19. To define how CCL19 facilitated the establishment of latent HIV infection, the role of chemokine receptor signalling was explored.

Results

In resting CD4⁺ T cells, CCL19 induced phosphorylation of RAC-alpha serine/threonine-protein kinase (Akt), nuclear factor kappa B (NF-κB), extracellular-signal-regulated kinase (ERK) and p38. Inhibition of the phosphoinositol-3-kinase (PI3K) and Ras/Raf/Mitogen-activated protein kinase/ERK kinase (MEK)/ERK signalling pathways inhibited HIV integration, without significant reduction in HIV nuclear entry (measured by Alu-LTR and 2-LTR circle qPCR respectively). Inhibiting activation of MEK1/ERK1/2, c-Jun N-terminal kinase (JNK), activating protein-1 (AP-1) and NF-κB, but not p38, also inhibited HIV integration. We also show that HIV integrases interact with Pin1 in CCL19-treated CD4⁺ T cells and inhibition of JNK markedly reduced this interaction, suggesting that CCL19 treatment provided sufficient signals to protect HIV integrase from degradation via the proteasome pathway. Infection of CCL19-treated resting CD4⁺ T cells with mutant strains of HIV, lacking NF-κB binding sites in the HIV long terminal repeat (LTR) compared to infection with wild type virus, led to a significant reduction in integration by up to 40-fold (range 1–115.4, p = 0.03). This was in contrast to only a modest reduction of 5-fold (range 1.7–11, p > 0.05) in fully activated CD4⁺ T cells infected with the same mutants. Finally, we demonstrated significant differences in integration sites following HIV infection of unactivated, CCL19-treated, and fully activated CD4⁺ T cells.

Conclusions

HIV integration in CCL19-treated resting CD4⁺ T cells depends on NF-κB signalling and increases the stability of HIV integrase, which allow subsequent integration and establishment of latency. These findings have implications for strategies needed to prevent the establishment, and potentially reverse, latent infection.

Electronic supplementary material

The online version of this article (doi:10.1186/s12977-016-0284-7) contains supplementary material, which is available to authorized users.