Project description:The hallmark of Kaposi’s sarcoma (KS), the most common cancer in HIV-infected patients caused by Kaposi’s sarcoma-associated herpesvirus (KSHV) infection, is hyperinflammation. However, the role of inflammation and the mechanism of induction of inflammation in KSHV-induced cancer remain unclear. In a previous high-throughput screening against KSHV-induced oncogenesis, over half of the identified candidates were anti-inflammatory agents. Among them, dexamethasone, a common anti-inflammatory corticosteroid, functions through binding to and activating glucocorticoid receptor (GR). In this study, we examined the mechanism mediating KSHV-induced inflammation. We found that numerous inflammatory pathways were activated in KSHV-transformed cells. Particularly, the interleukin-1 alpha (IL-1α) and IL-1 receptor antagonist (IL-1Ra) from the IL-1 family, implicated in a wide variety of inflammatory diseases, were the most induced and suppressed cytokines in KSHV-transformed KMM cells compared to the matched primary MM cells, respectively. By using reverse genetics, we showed that KSHV-encoded miRNAs mediated IL-1α induction while both miRNAs and vFLIP mediated IL-1Ra suppression. Furthermore, the GR signaling was inhibited in KSHV-transformed cells, which was mediated by vFLIP and vCyclin. Importantly, dexamethasone treatment inhibited cell proliferation, and colony formation in softagar of KMM cells but had a minimal effect on MM cells. Consequently, dexamethasone suppressed the initiation and growth of KS-like KMM tumors in mice. Mechanistically, dexamethasone suppressed IL-1α expression but induced IL-1Ra expression. Treatment with recombinant IL-1α protein was sufficient to rescue the inhibitory effect of dexamethasone while overexpression of IL-1Ra alone caused a weak growth inhibition of KMM cells. Furthermore, dexamethasone induced IκBα expression resulting in the inhibition of the classical and alternative NF-kB pathways and IL-1α expression. Taken together, these results revealed the important role of IL-1 signaling pathway in KSHV-induced inflammation and oncogenesis, which can be inhibited by dexamethasone-activated GR signaling. This study determined the mechanism of inflammation in KSHV-induced oncogenesis and identified IL-1-mediated inflammation as a potential therapeutic target for KSHV-induced malignancies.
Project description:Ferroptosis, a defensive strategy employed by the host to restrict pathogenic infections, has been implicated in the development and therapeutic responses of various types of tumors. However, the role of ferroptosis in KSHV-induced malignant tumors remains elusive. A steadily growing number of non-histone proteins have been identified as acetylation targets, their functions have yet to be revealed. In this study, we obtained a marked disparity in the landscape of acetylation between MM and KSHV-transformed MM (KMM) cells. SERBP1 deacetylation was upregulated in KMM cells and contributed to KSHV-induced cellular transformation by inhibiting ferroptosis. Mechanistically, KSHV-encoded viral interleukin-6 (vIL-6) hijacks SIRT3, a mitochondrial NAD+-dependent deacetylase, to interact with SERBP1 leading to the deacetylation of SERBP1. Deacetylated SERBP1 exhibits reduced binding to Lipt2 mRNA, which promotes Lipt2 mRNA degradation, resulting in ferroptosis inhibition. Our findings unveil a novel role of SERBP1 deacetylation in regulating ferroptosis and KSHV-induced cellular transformation and identify potential new therapeutic targets for KSHV infection and KSHV-induced cancers.