Dysregulation and Epigenetic Reprogramming of NRF2 Signaling Axis Promote Acquisition of Cisplatin Resistance and Metastasis in Head and Neck Squamous Cell Carcinoma.

PURPOSE: Cisplatin (CDDP)-based chemotherapy is a first-line treatment for patients with advanced head and neck squamous cell carcinomas (HNSCC), despite a high rate of treatment failures, acquired resistance, and subsequent aggressive behavior. The purpose of this study was to study the mechanism of CDDP resistance and metastasis in HNSCC. We investigated the role of NRF2 pathway activation as a driven event for tumor progression and metastasis of HNSCC. EXPERIMENTAL DESIGN: Human HNSCC cell lines that are highly resistant to CDDP were generated. Clonogenic survival assays and a mouse model of oral cancer were used to examine the impact of NRF2 activation in vitro and in vivo on CDDP sensitivity and development of metastasis. Western blotting, immunostaining, whole-exome sequencing, single-cell transcriptomic and epigenomic profiling platforms were performed to dissect clonal evolution and molecular mechanisms. RESULTS: Implantation of CDDP-resistant HNSCC cells into the tongues of nude mice resulted in a very high rate of distant metastases. The CDDP-resistant cells had significantly higher expression of NRF2 pathway genes in the presence of newly acquired KEAP1 mutations, or via epigenomic activation of target genes. Knockdown of NRF2 or restoration of the wild-type KEAP1 genes resensitized resistant cells to CDDP and decreased distant metastasis (DM). Finally, treatment with inhibitor of glutaminase-1, a NRF2 target gene, alleviated CDDP resistance. CONCLUSIONS: CDDP resistance and development of DM are associated with dysregulated and epigenetically reprogrammed KEAP1-NRF2 signaling pathway. A strategy targeting KEAP1/NRF2 pathway or glutamine metabolism deserves further clinical investigation in patients with CDDP-resistant head and neck tumors.

Long Noncoding RNA Ceruloplasmin Promotes Cancer Growth by Altering Glycolysis.

Long noncoding RNAs (lncRNAs) significantly influence the development and regulation of genome expression in cells. Here, we demonstrate the role of lncRNA ceruloplasmin (NRCP) in cancer metabolism and elucidate functional effects leading to increased tumor progression. NRCP was highly upregulated in ovarian tumors, and knockdown of NRCP resulted in significantly increased apoptosis, decreased cell proliferation, and decreased glycolysis compared with control cancer cells. In an orthotopic mouse model of ovarian cancer, siNRCP delivered via a liposomal carrier significantly reduced tumor growth compared with control treatment. We identified NRCP as an intermediate binding partner between STAT1 and RNA polymerase II, leading to increased expression of downstream target genes such as glucose-6-phosphate isomerase. Collectively, we report a previously unrecognized role of the lncRNA NRCP in modulating cancer metabolism. As demonstrated, DOPC nanoparticle-incorporated siRNA-mediated silencing of this lncRNA in vivo provides therapeutic avenue toward modulating lncRNAs in cancer.

Beta-arrestin scaffolding of phosphatidylinositol 4-phosphate 5-kinase Ialpha promotes agonist-stimulated sequestration of the beta2-adrenergic receptor.

Members of the seven-transmembrane receptor (7TMR) superfamily are sequestered from the plasma membrane following stimulation both to limit cellular responses as well as to initiate novel G protein-independent signaling pathways. The best studied mechanism for 7TMR internalization is via clathrin-coated pits, where clathrin and adaptor protein complex 2 nucleate and polymerize upon encountering the membrane phospholipid phosphatidylinositol 4,5-bisphosphate (PIP(2)) to form the outer layer of the clathrin-coated vesicle. Activated receptors are recruited to clathrin-coated pits by beta-arrestins, scaffolding proteins that interact with agonist-occupied 7TMRs as well as adaptor protein complex 2 and clathrin. We report here that following stimulation of the beta2-adrenergic receptor (beta2-AR), a prototypical 7TMR, beta-arrestins bind phosphatidylinositol 4-phosphate 5-kinase (PIP5K) Ialpha, a PIP(2)-producing enzyme. Furthermore, beta-arrestin2 is required to form a complex with PIP5K Ialpha and agonist-occupied beta2-AR, and beta-arrestins synergize with the kinase to produce PIP(2) in response to isoproterenol stimulation. Interestingly, beta-arrestins themselves bind PIP(2), and a beta-arrestin mutant deficient in PIP(2) binding no longer internalizes 7TMRs, fails to interact with PIP5K Ialpha, and is not associated with PIP kinase activity assayed in vitro. However, a chimeric protein in which the core kinase domain of PIP5K Ialpha has been fused to the same beta-arrestin mutant rescues internalization of beta2-ARs. Collectively, these data support a model in which beta-arrestins direct the localization of PIP5K Ialpha and PIP(2) production to agonist-activated 7TMRs, thereby regulating receptor internalization.

The HDAC complex and cytoskeleton.

HDAC6 is a cytoplasmic deacetylase that dynamically associates with the microtubule and actin cytoskeletons. HDAC6 regulates growth factor-induced chemotaxis by its unique deacetylase activity towards microtubules or other substrates. Here we describe a non-catalytic structural domain that is essential for HDAC6 function and places HDAC6 as a critical mediator linking the acetylation and ubiquitination network. This evolutionarily conserved motif, termed the BUZ domain, has features of a zinc finger and binds both mono- and polyubiquitinated proteins. Furthermore, the BUZ domain promotes HDAC6 mono-ubiquitination. These results establish the BUZ domain, in addition to the UIM and CUE domains, as a novel motif that both binds ubiquitin and mediates mono-ubiquitination. Importantly, the BUZ domain is essential for HDAC6 to promote chemotaxis, indicating that communication with the ubiquitin network is critical for proper HDAC6 function. The unique presence of the UIM and CUE domains in proteins involved in endocytic trafficking suggests that HDAC6 might also regulate vesicle transport and protein degradation. Indeed, we have found that HDAC6 is actively transported and concentrated in vesicular compartments. We propose that an integration of reversible acetylation and ubiquitination by HDAC6 may be a novel component in regulating the cytoskeleton, vesicle transport and protein degradation.