Aberrant promoter methylation and reduced expression of p16 gene in esophageal squamous cell carcinoma from Kashmir valley: a high-risk area

Esophageal squamous cell carcinoma (ESCC) is one of the most prevalent cancer in Jammu and Kashmir region of India and has multi-factorial etiology involving dietary habits, genetic factors, and gene environmental interactions. Inactivation of the p16 gene expression by aberrant promoter methylation plays an important role in the progression of esophageal carcinoma. In the present investigation, we have studied the role of p16 promoter methylation in 69 histopathologically confirmed ESCC tissues and compared it with corresponding normal adjacent tissues for DNA methylation in the CpG island in the p16 promoter region by methylation-specific polymerase chain reaction (MSP) and p16 protein expression by immunoblotting. The results showed loss of p16 expression in 67% (46/69) of tumor tissues compared to only 3% in control tissues (2/69). Promoter methylation was observed in 52% (36/69) of tumor tissues and it gradually increased with the increasing severity of histological grades of the cancer (P = 0.0001). Loss of p16 expression with promoter methylation was observed in 26 of 36 cases (72%). Analysis of patients dietary habits revealed a strong association between promoter methylation and high consumption of hot salted tea (P < 0.05) which is a most favourite drink commonly consumed by Kashmiri people.     

Characterization of variation in the canine suppressor of cytokine signaling-2 (SOCS2) gene

Suppressor of cytokine signaling 2 (SOCS2) is a negative regulator of growth hormone signaling. The deletion of SOCS2 in mice results in a 30-50% increase in post-natal growth. In an effort to identify polymorphisms in the SOCS2 gene that may be associated with body size in dogs, we characterized the canine SOCS2 gene and analyzed its genetic diversity among small and large dog breeds. The study was carried out on a total of 520 dogs from 66 different breeds. Dogs were classified as large or small based on height and weight as determined by their respective American Kennel Club breed standards. The SH2 and SOCS domains of the canine SOCS2 gene were sequenced in 32 dogs from different breeds. Only one non-synonymous sequence variant (DQ415457:g.326G>T) was detected which corresponds to an amino acid change (Asp127Tyr). All samples were genotyped by PCR/RFLP and the allele frequencies were determined for each dog breed. The T allele was distributed primarily among European large dog breeds with a gene frequency ranging from 0.72 to 0.04. The nature of the nucleotide change and the effect on the protein together with the finding of a QTL related to body size in the same CFA15 region by other researchers suggest canine SOCS2 as a potential candidate gene for body size in dogs. Future studies will be needed to clarify the role of the 326G>T polymorphism and its interaction with genes like growth hormone and insulin-like growth factor 1.     

Bacterial flagellin inhibits T cell receptor-mediated activation of T cells by inducing suppressor of cytokine signalling-1 (SOCS-1)

Flagellin, the structural component of bacterial flagella, is secreted by pathogenic and commensal bacteria, and is recognized by Toll-like receptor (TLR) 5. Flagellin is a common bacterial antigen present on most motile bacteria and is speculated to contribute to the activation of CD4+ T cells in the intestine. However, molecular mechanisms by which flagellin regulate T cell activation remains to be determined. Using Jurkat T cells or human primary T cell, we showed that flagellin stimulation induced tyrosine phosphorylation of TLR5 and activation of both mitogen-activated protein kinases and nuclear factor kappaB. In addition, stimulation by flagellin did not induce nuclear factor of activated T cells (NFAT) activation, while stimulation via the T cell receptor (TCR) leads to activation of NFAT. However, TCR-mediated NFAT activation and tyrosine phosphorylation of zeta-associated protein 70 (Zap-70) were inhibited in cells pre-stimulated by flagellin. Furthermore, flagellin stimulation induced suppressor of cytokine signalling-1 (SOCS-1), which formed a complex with Zap-70 after stimulation via TCR, and inhibition of SOCS-1 expression by SOCS-1-specific small interfering RNA reinstated TCR-mediated activation of NFAT in cells pre-stimulated with flagellin. These results collectively indicate that bacterial flagellin inhibits TCR-mediated activation of T cells by inducing SOCS-1.     

Epigenetic silencing of miR-203 in Kazakh patients with esophageal squamous cell carcinoma by MassARRAY spectrometry

Dysregulation of miR-203 by promoter methylation is associated with the development of various cancers. We aimed to explore the underlying link between promoter methylation and miR-203 expression in Kazakh esophageal squamous cell carcinoma (ESCC). MassARRAY® System spectrometry was used to quantitatively analyze the DNA methylation of 32 CpG sites within miR-203 in 99 Kazakh ESCC and 46 normal esophageal tissues (NETs) with similar population characteristics. We conducted real-time PCR to detect miR-203 expression levels and evaluated their association with methylation. Eleven CpG units within miR-203 promoter were frequently hypermethylated in ESCC compared with NETs (P < 0.05). The hypermethylation of several CpG units positively correlated with age, lower esophagus, constrictive type of ESCC, and moderately differentiated ESCC. Given the involvement of human papillomavirus (HPV) in etiology of ESCC was confirmed from our previous reports, herein we found that CpG units within miR-203 in HPV16-positive ESCC are more heavily methylated. Furthermore, miR-203 expression showed a nearly 4.5-fold decrease in ESCC than NETs (0.206 ± 0.336 vs. 0.908 ± 1.424, P < 0.001) and was significantly associated with lymph node metastasis (P = 0.012). The expression of miR-203 with 11 completely hypermethylated CpG units was approximately 6.5-fold lower than that with at least 1 unmethylated CpG unit (P < 0.001) and especially the CpG_15.16 and CpG_31.32 with higher methylation levels in ESCC tissues exhibited lower expression levels of miR-203, which indicated a reverse association between miR-203 methylation and expression. Hypermethylated miR-203 is a potential biomarker and targeted delivery of miR-203 could therefore serve as a preventive or therapeutic strategy for Kazakh ESCC.     

Silencing suppressor of cytokine signaling-1 (SOCS1) in macrophages improves Mycobacterium tuberculosis control in an interferon-gamma (IFN-gamma)-dependent manner

Protection against infection with Mycobacterium tuberculosis demands IFN-γ. SOCS1 has been shown to inhibit responses to IFN-γ and might thereby play a central role in the outcome of infection. We found that M. tuberculosis is a highly efficient stimulator of SOCS1 expression in murine and human macrophages and in tissues from infected mice. Surprisingly, SOCS1 reduced responses to IL-12, resulting in an impaired IFN-γ secretion by macrophages that in turn accounted for a deteriorated intracellular mycobacterial control. Despite SOCS1 expression, mycobacteria-infected macrophages responded to exogenously added IFN-γ. SOCS1 attenuated the expression of the majority of genes modulated by M. tuberculosis infection of macrophages. Using a conditional knockdown strategy in mice, we found that SOCS1 expression by macrophages hampered M. tuberculosis clearance early after infection in vivo in an IFN-γ-dependent manner. On the other hand, at later time points, SOCS1 expression by non-macrophage cells protected the host from infection-induced detrimental inflammation.     

MicroRNA-143 functions as a tumor suppressor in human esophageal squamous cell carcinoma

Esophageal cancer is one of the most common cancers worldwide with a poor prognosis. MicroRNAs(miRNAs) are a class of naturally occurring small noncoding RNAs and play an important role in cancer initiation and development. In this study, we demonstrate that the expression levels of miR-143 and miR-145 were significantly decreased in ESCC tissues in comparison with adjacent normal esophageal squamous tissues(NESTs). Furthermore, an inverse correlation between miR-143 and tumor invasion depth and lymph node metastasis was observed. The enforced expression of miR-143 induced growth suppression and apoptosis of ESCC cells. Rescue of miR-143 significantly suppressed the ESCC cells migration and invasion capabilities. Moreover, we show that functions of miR-143 in ESCC are mediated at least in part by the inhibition of extracellular signal regulated kinase-5(ERK-5) activity. These results prove that miR-143 may act as a tumor suppressor in ESCC.     

Regulation of IL-21 signaling by suppressor of cytokine signaling-1 (SOCS1) in CD8(+) T lymphocytes

Mice lacking the gene for suppressor of cytokine signaling 1 (SOCS1) show defective homeostasis of T lymphocytes due to accumulation of CD8⁺ T cells, resulting at least partly from dysregulated IL-15 signaling. IL-15 alone does not stimulate proliferation of naïve CD8 T cells, but can synergize with IL-21 to induce proliferation, suggesting a potential role for IL-21 in the defective homeostasis of CD8⁺ T lymphocytes in SOCS1^−/− mice. Since IL-21 strongly induced SOCS1 mRNA in CD8⁺ T cells, we investigated whether SOCS1 regulates their response to IL-21. CD8⁺ T cells isolated from SOCS1-deficient mice proliferated vigorously in response to IL-21 + IL-15. In CD8⁺ T lymphocytes expressing transgenic TCR, IL-21 + IL-7 provided a stronger stimulus to naïve cells whereas IL-15 + IL-21 potently stimulated memory cells. Compared to truly naïve or memory cells, SOCS1^−/− H-Y TCR⁺ CD8⁺ T cells displayed CD44^loLy6C^hiCD122^intCD127^lo partial memory phenotype and exhibited stronger response to IL-15 + IL-21 than truly naïve cells. In SOCS1^−/− CD8⁺ T cells, IL-21 caused greater reduction in IL-15 threshold for activation in a dose-dependent manner. SOCS1 deficiency did not modulate IL-21Rα expression or sensitivity to IL-21, but delayed the loss of IL-21-induced phospho-STAT3 signal. These results show that SOCS1 is a critical regulator of IL-21 signaling in CD8⁺ T cells, and support the notion that sustained IL-21 signaling might also contribute to the aberrant T cell homeostasis in SOCS1-deficient mice.     

Induction of hyper Th1 cell-type immune responses by dendritic cells lacking the suppressor of cytokine signaling-1 gene

Suppressor of cytokine signaling (SOCS1/JAB) has been shown to play an important role in regulating dendritic cell (DC) function and suppressing inflammatory diseases and systemic autoimmunity. However, role of SOCS1 in DCs for the initiation of Th cell response has not been clarified. Here we demonstrate that SOCS1-deficient DCs induce stronger Th1-type responses both in vitro and in vivo. SOCS1-deficient DCs induced higher IFN-gamma production from naive T cells than wild-type (WT) DCs in vitro. Lymph node T cells also produced a higher amount of IFN-gamma when SOCS1-deficient bone marrow-derived DCs (BMDCs) were transferred in vivo. Moreover, SOCS1(-/-) BMDCs raised more effective anti-tumor immunity than WT BMDCs. Microarray analysis revealed that IFN-inducible genes were highly expressed in SOCS1-deficient DCs without IFN stimulation, suggesting hyper STAT1 activation in SOCS1(-/-) DCs. These phenotypes of SOCS1-deficient DCs were similar to those of CD8alpha(+) DCs, and in the WT spleen, SOCS1 is expressed at higher levels in the Th2-inducing CD4(+) DC subset, relative to the Th1-inducing CD8alpha(+) DC subset. We propose that reduction of the SOCS1 gene expression in DCs leads to CD8alpha(+) DC-like phenotype which promotes Th1-type hyperresponses.     

Both the suppressor of cytokine signaling 1 (SOCS-1) kinase inhibitory region and SOCS-1 mimetic bind to JAK2 autophosphorylation site: implications for the development of a SOCS-1 antagonist

Suppressor of cytokine signaling (SOCS)-1 protein modulates signaling by IFN-gamma by binding to the autophosphorylation site of JAK2 and by targeting bound JAK2 to the proteosome for degradation. We have developed a small tyrosine kinase inhibitor peptide (Tkip) that is a SOCS-1 mimetic. Tkip is compared in this study with the kinase inhibitory region (KIR) of SOCS-1 for JAK2 recognition, inhibition of kinase activity, and regulation of IFN-gamma-induced biological activity. Tkip and a peptide corresponding to the KIR of SOCS-1, ((53))DTHFRTFRSHSDYRRI((68)) (SOCS1-KIR), both bound similarly to the autophosphorylation site of JAK2, JAK2(1001-1013). The peptides also bound to JAK2 peptide phosphorylated at Tyr(1007), pJAK2(1001-1013). Dose-response competitions suggest that Tkip and SOCS1-KIR similarly recognize the autophosphorylation site of JAK2, but probably not precisely the same way. Although Tkip inhibited JAK2 autophosphorylation as well as IFN-gamma-induced STAT1-alpha phosphorylation, SOCS1-KIR, like SOCS-1, did not inhibit JAK2 autophosphorylation but inhibited STAT1-alpha activation. Both Tkip and SOCS1-KIR inhibited IFN-gamma activation of Raw 264.7 murine macrophages and inhibited Ag-specific splenocyte proliferation. The fact that SOCS1-KIR binds to pJAK2(1001-1013) suggests that the JAK2 peptide could function as an antagonist of SOCS-1. Thus, pJAK2(1001-1013) enhanced suboptimal IFN-gamma activity, blocked SOCS-1-induced inhibition of STAT3 phosphorylation in IL-6-treated cells, enhanced IFN-gamma activation site promoter activity, and enhanced Ag-specific proliferation. Furthermore, SOCS-1 competed with SOCS1-KIR for pJAK2(1001-1013). Thus, the KIR region of SOCS-1 binds directly to the autophosphorylation site of JAK2 and a peptide corresponding to this site can function as an antagonist of SOCS-1.