Expression Efficiency of Multiple Il9 Reporter Alleles Is Determined by Cell Lineage.

Generation of allelic gene reporter mice has provided a powerful tool to study gene function in vivo. In conjunction with imaging technologies, reporter mouse models facilitate studies of cell lineage tracing, live cell imaging, and gene expression in the context of diseases. Although there are several advantages to using reporter mice, caution is important to ensure the fidelity of the reporter protein representing the gene of interest. In this study, we compared the efficiency of two Il9 reporter strains Il9citrine and Il9GFP in representing IL-9-producing CD4+ TH9 cells. Although both alleles show high specificity in IL-9-expressing populations, we observed that the Il9GFP allele visualized a much larger proportion of the IL-9-producing cells in culture than the Il9citrine reporter allele. In defining the mechanistic basis for these differences, chromatin immunoprecipitation and chromatin accessibility assay showed that the Il9citrine allele was transcriptionally less active in TH9 cells compared with the wild-type allele. The Il9citrine allele also only captured a fraction of IL-9-expressing bone marrow-derived mast cells. In contrast, the Il9 citrine reporter detected Il9 expression in type 2 innate lymphoid cells at a greater percentage than could be identified by IL-9 intracellular cytokine staining. Taken together, our findings demonstrate that the accuracy of IL-9 reporter mouse models may vary with the cell type being examined. These studies demonstrate the importance of choosing appropriate reporter mouse models that are optimal for detecting the cell type of interest as well as the accuracy of conclusions.

High expression of IL-9R promotes the progression of human hepatocellular carcinoma and indicates a poor clinical outcome.

Interleukin-9 receptor (IL-9R) overexpression has a pivotal role in human hematological malignancies. However, the expression of IL-9R and its biological role in human solid tumors remains elusive. In the present study, western blot analysis and RT-qPCR were used to determine the expression of IL-9R in hepatocellular carcinoma (HCC) cell lines and tumor tissues. Proliferation, cell cycle, apoptosis and Transwell assays were used to examine the biological role of IL-9R in HCC cells. The results showed that IL-9R and its ligand IL-9 were constitutively expressed in HCC cells and tissues. Moreover, the expression levels of IL-9R and IL-9 were significantly higher in tumor tissues compared to the peritumor liver tissues. Functional experiments suggested that IL-9R significantly promoted HCC cell proliferation, invasion and inhibited apoptosis, possibly by acting through the IL-9/IL-9R axis. After silencing IL-9R, the expression of VEGF, p-p38, p-STAT3 and MMP9, markedly decreased suggesting the potential involvement of these molecules in IL-9R activity. Immunohistochemistry­based survival analysis revealed that a differential expression of IL-9R in HCC tissue was a significant and independent prognostic factor for survival [HR, 1.66; 95% confidence interval (CI), 1.17-2.36; P=0.005] and recurrence [HR, 1.50; 95%CI, 1.04­2.17; P=0.03]. In addition, a high IL-9R expression positively and significantly correlated with larger (P=0.012) and advanced tumor stage (P=0.018). The findings indicated that IL-9R was constitutively expressed and exerted a tumor-promoting effect in HCC, whose expression level may be a useful biomarker of tumor invasiveness and patient clinical outcome.

Overexpression of IL-9 receptor in diffuse large B-cell lymphoma.

Interleukin-9 (IL-9) is initially described as a growth factor secreted by helper T cells. It acts on a variety of immune cells via its receptor (IL-9R). Recently, the oncogenic activities of IL-9 and IL-9R were reported in some lymphomas but not diffuse large B-cell lymphoma (DLBCL). The purpose of the present study is to investigate the expression of IL-9R in pathological tissues from patients with DLBCL and to evaluate its correlation with clinical characteristics. Tissue samples from patients with DLBCL and reactive lymphoid hyperplasia were analyzed using RT-PCR, western blot and immunohistochemical staining. There was a higher expression of IL-9R within DLBCL tissues compared with hyperplasic lymph nodes. Immunohistochemical analysis indicated membrane localization of IL-9R in 22 of 36 (61.1%) DLBCL cases. The upregulated IL-9R was correlated to the serum levels of ß2 microglobulin and albumin, International Prognostic Index (IPI) score as well as Ki-67 expression within tumor tissues. Our findings suggest that overexpression of IL-9R may contribute to the pathogenesis of DLBCL and is associated with some adverse prognostic parameters.

A brief history of IL-9.

IL-9 was first described in the late 1980s as a member of a growing number of cytokines that had pleiotropic functions in the immune system. Although many biological functions have been attributed to IL-9, it remains an understudied cytokine. A resurgence of interest in IL-9 has been spurred by recent work demonstrating a role for IL-9 in regulating inflammatory immunity and defining the transcription factors that activate the Il9 gene in cells that most efficiently produce IL-9. In this review, we summarize the characterization of IL-9 biological activities, highlight roles for the cytokine that are clearly defined, and outline questions regarding IL-9 functions that still require further exploration.

T(H)2 cytokines modulate the IL-9R expression on human neutrophils.

Interleukin (IL)-9 is associated with key pathological features of asthma such as airway hyperresponsiveness, bronchoconstriction and mucus production. Inflammatory responses mediated by IL-9 rely on the expression of the IL-9R which has been reported on lung epithelial cells, T lymphocytes and recently on airway granulocyte infiltrates. In this study, we assessed the regulatory and constitutive cell surface expression of the IL-9Ralpha in unfractionated and purified human neutrophils from atopic asthmatics, atopic non-asthmatics and healthy normal controls. We demonstrate that T(H)2 cytokines (IL-4 or IL-13) and granulocyte macrophage-colony stimulating factor (GM-CSF) up-regulated mRNA and cell surface expression levels of the IL-9Ralpha in primary human and HL-60 differentiated neutrophils. Pharmacological inhibition of NF-kappaB did not affect T(H)2-mediated IL-9Ralpha expression in human neutrophils although IFN-gamma and IL-10 down-regulated IL-9Ralpha expression when co-incubated with IL-4, IL-13 or GM-CSF. Collectively, our results reveal a regulatory function for IFN-gamma and IL-10 on modulating the inducible IL-9Ralpha expression levels on peripheral blood neutrophils by T(H)2 cytokines.