These results suggest that HAGE prevents IFNobservations above (Figure 3c)

These results suggest that HAGE prevents IFNobservations above (Figure 3c). HAGE. Furthermore, we provide a MM-102 mechanism by which HAGE promotes SOCS1 mRNA unwinding and protein expression (IFNtreatment and that cancer therapies targeting HAGE may have broad implications for the treatment of malignant melanoma. (IFNtreatment and the involvement of MMICs in this process are MM-102 unknown. IFNsignals through the JAKCSTAT (janus kinaseCsignal transducers and activators of transcription) pathway and results in the induction of several genes. This endows IFNwith multiple effects in a variety of malignancies that range from antiangiogenic effects to potent immunoregulatory, differentiation-inducing, pro-apoptotic and anti-proliferative properties.8, 9 The DCHS1 gene encoding promyelocytic leukaemia protein (PML) is a well-known downstream target of IFNs signalling and its induction by IFNs results in a significant increase in the expression of PML and the number of PML nuclear bodies (PML-NBs).10, 11, 12 PML, a member of the Ring-B Box-Coiled Coil family, is a tumour suppressor which was originally identified at the breakpoint of the t (15;17) translocation found in acute promyelocytic leukaemia (APL).13, 14, 15 It is at the heart of many cellular pathways such as cell growth, differentiation, DNA damage, senescence, apoptosis and anti-viral responsiveness.16, 17, 18 PML functions by interacting and recruiting different factors that compose these cellular processes into subnuclear structures known as PML-NBs, of which it is the essential component.18 Although the role of PML in IFNs-mediated antiviral responses has been well studied, little is known about its role in the anti-tumour properties of IFNs.16, 19 On the basis of this background, we hypothesised that this helicase HAGE (DDX43) may endow MMICs with a resistance to the anti-tumour effects of IFN-induced PML. Here, we reveal a previously unknown role of HAGE, namely that it ensures the survival of MMICs in response to the anti-proliferative and pro-apoptotic effects of IFN. Using a stem cell proliferation assay and tumour xenotransplantation assay in non-obese diabetic/severe combined immunodeficiency (NOD/SCID) mice, we show that HAGE promotes tumour initiation and MMIC-dependent growth by preventing the IFN-induced inhibition. HAGE expression in malignant melanoma cells prevents the activation of the JAKCSTAT signalling pathway which is usually involved in the induction of PML transcription. Knockdown of HAGE in ABCB5+ MMICs results in increased PML expression at the RNA and protein levels. This event is usually favoured through an increase in expression of the suppressor of cytokine signalling SOCS1 protein, a known positive regulator of ubiquitination and degradation of JAK proteins.20 HAGE knockdown in melanoma cell lines expressing ABCB5 decreases SOCS1 protein expression and this is reversed by re-introducing HAGE in these cells. An unwinding assay provides a mechanistic insight by demonstrating the capacity of the helicase HAGE to unwind SOCS1 RNA MM-102 complexes and thereby promote the expression of SOCS1 protein. Collectively, these findings support the model by which HAGE promotes the initiation of tumours by ABCB5+ MMICs and their resistance to the anti-proliferative effects of IFN by inactivating the JAKCSTAT pathway which is necessary for PML expression via a mechanism which involves the SOCS1. Results Decreased PML expression in HAGE+?ABCB5+ MMICs The loss of PML expression has been previously reported in several solid tumours from different tissue origins. 21 MM-102 To investigate the expression status of PML in HAGE+ and ABCB5+ MMICs, we performed immunostaining on a malignant melanoma tissue microarray (TMA) using antibodies against PML, HAGE and ABCB5. PML expression was significantly decreased in HAGE+ and ABCB5+ tumour cells when compared with the control (normal skin). As a consequence, this decrease correlated with.