Project description:LNK (SH2B3) is a key negative regulator of JAK-STAT signaling which has been extensively studied in malignant hematopoietic diseases. We found that LNK is significantly elevated in cutaneous melanoma; this elevation is correlated with hyperactive signaling of the RAS-RAF-MEK pathway. Elevated LNK enhances cell growth and survival in adverse conditions. Forced expression of LNK inhibits signaling by interferon-STAT1 and suppresses interferon (IFN) induced cell cycle arrest and cell apoptosis. In contrast, silencing LNK expression by either shRNA or CRISPR-Cas9 potentiates the killing effect of IFN. The IFN-LNK signaling is tightly regulated by a negative feedback mechanism; melanoma cells exposed to IFN upregulate expression of LNK to prevent overactivation of this signaling pathway. Our study reveals an unappreciated function of LNK in melanoma and highlights the critical role of the IFN-STAT1-LNK signaling axis in this potentially devastating disease. LNK may be further explored as a potential therapeutic target for melanoma immunotherapy.
Project description:LNK (SH2B3) is a key negative regulator of JAK-STAT signaling which has been extensively studied in malignant hematopoietic diseases. We found that LNK is significantly elevated in cutaneous melanoma; this elevation is correlated with hyperactive signaling of the RAS-RAF-MEK pathway. Elevated LNK enhances cell growth and survival in adverse conditions. Forced expression of LNK inhibits signaling by interferon-STAT1 and suppresses interferon (IFN) induced cell cycle arrest and cell apoptosis. In contrast, silencing LNK expression by either shRNA or CRISPR-Cas9 potentiates the killing effect of IFN. The IFN-LNK signaling is tightly regulated by a negative feedback mechanism; melanoma cells exposed to IFN upregulate expression of LNK to prevent overactivation of this signaling pathway. Our study reveals an unappreciated function of LNK in melanoma and highlights the critical role of the IFN-STAT1-LNK signaling axis in this potentially devastating disease. LNK may be further explored as a potential therapeutic target for melanoma immunotherapy.
Project description:To investigate the effect of Interferon-gamma signaling on gene expression in melanoma cells We performed gene expression analysis of mouse melanoma cell lines that have been treated with Interferon-gamma cytokine as compared with mock-treated controls.
Project description:Activation of oncogenes often leads to induction of the DNA damage responses and onset of the cell senescence. Given that DNA damage can also trigger production of type I interferons (IFN) that contribute to senescence development, we sought to determine the role of IFN in the oncogene-induced senescence. Our data in mouse model demonstrate that inactivation of IFN signaling is sufficient for inducing melanomas in melanocytes harboring mutant Braf. Restoration of IFN signaling in IFN-deficient melanoma cells induces cell senescence and suppresses melanoma progression. In addition, data in human patients that received high dose IFN therapy and in mouse transplanted tumor models strongly suggest the importance of the non-cell-autonomous IFN signaling. Suppression of IFN signaling mediated by the downregulation of IFN receptor IFNAR1 invariably occurs during development of mouse melanoma. Mice harboring the IFNAR1 mutant, which is relatively resistant to downregulation, delay melanoma development, suppress the metastatic disease, and better respond to treatment with BRAF or PD1 inhibitors. These results suggest that IFN signaling is an important tumor suppressive pathway that inhibits melanoma development and progression. Accordingly, the inhibition of IFN pathway via IFNAR1 downregulation plays a key role in melanoma pathogenesis. Conversely, these data also argue for targeting IFNAR1 downregulation to prevent the metastatic disease and improve the efficacy of molecularly targeted and immune-targeted therapies. Two genotypes of mice were examined at 2 to 3 times after tamoxifen adminstration, with 2 replicates for each condition, yielding 8 samples in total.
Project description:The cohesin complex participates in the organization of 3D genome through generating and maintaining DNA loops. Stromal antigen 2 (STAG2), a core subunit of the cohesin complex, is frequently mutated in various cancers. However, the impact of STAG2 inactivation on 3D genome organization and subsequent gene expression in cancer remain poorly understood. Here we show that depletion of STAG2 in melanoma cells leads to expansion of topologically associating domains (TADs) and enhances the formation of H3K27Ac-associated DNA loops at sites where binding of STAG2 is switched to its paralog STAG1. We further identify Interferon Regulatory Factor 9 (IRF9) as a major direct target of STAG2 in melanoma cells via integrated RNA-Seq, STAG2 ChIP-Seq and H3K27Ac HiChIP analyses. We demonstrate that loss of STAG2 activates IRF9 through modulating the 3D genome organization, which in turn enhances type I interferon signaling and increases the expression of PD-L1. Our findings not only establish a previously unknown role of the STAG2 to STAG1 switch in 3D genome organization, but also reveal a functional link between STAG2 and interferon signaling in cancer cells, which may contribute to malignant phenotype in STAG2-mutant cancer.
Project description:We analyzed baseline and on-therapy tumor biopsies from 101 patients with advanced melanoma treated with nivolumab (anti-PD-1) alone or combined with ipilimumab (anti-CTLA-4). Analysis of whole transcriptome data showed that T cell infiltration and interferon-gamma signaling signatures corresponded most highly with clinical response to therapy, with a reciprocal decrease in cell cycle and WNT signaling pathways in responding biopsies. Clinical outcome differences were likely not due to differential melanoma cell responses to interferon-gamma, as 57 human melanoma cell lines exposed in vitro to this cytokine showed a conserved interferon-gamma transcriptome response unless they had mutations that precluded signaling from the interferon-gamma receptor. Therefore, the magnitude of the antitumor T cell response and the corresponding downstream interferon-gamma signaling are the main drivers of clinical response or resistance to immune checkpoint blockade therapy.