Reduced expression of CYLD promotes cell survival and inflammation in gefitinib-treated NSCLC PC-9 cells: Targeting CYLD may be beneficial for acquired resistance to gefitinib therapy

CIB2 mediates acquired gefitinib resistance by inducing ZEB1 expression and epithelial-mesenchymal transition

EGFR-TKIs have been used as frontline treatment in patients with advanced non-small cell lung cancer (NSCLC) suffering from the EGFR mutation. Gefitinib, the first-generation EGFR-TKI, has greatly improved survival rates in lung cancer patients, whereas acquired gefitinib resistance is still a critical issue that needs to be overcome. In our research, high expression levels of CIB2 were found in gefitinib-resistant lung cancer cells. CIB2 knockout rendered gefitinib-resistant cells more sensitive to gefitinib, and overexpression of CIB2 in parental cells was sufficient to induce more resistance to gefitinib. Inhibition of CIB2 in gefitinib-resistant lung cancer cells significantly induced cell apoptosis. To clarify the major molecular mechanism by which CIB2 increases gefitinib resistance, we demonstrated that raised CIB2 in lung cancer cells promoted epithelial-to-mesenchymal transition (EMT) through upregulation of ZEB1. Moreover, FOSL1 transcriptionally regulated CIB2 expression. Finally, CIB2 rendered tumors resistant to gefitinib treatment in vivo. Our results explored a new mechanism: upregulated CIB2 promoted EMT through ZEB1 to regulate gefitinib resistance, which could be a candidate therapeutic target for overcoming acquired resistance to EGFR-TKIs in NSCLC patients.

CYLD regulates cell ferroptosis through Hippo/YAP signaling in prostate cancer progression

Prostate cancer (PCa) is one of the most common malignancy in men. However, the molecular mechanism of its pathogenesis has not yet been elucidated. In this study, we demonstrated that CYLD, a novel deubiquitinating enzyme, impeded PCa development and progression via tumor suppression. First, we found that CYLD was downregulated in PCa tissues, and its expression was inversely correlated with pathological grade and clinical stage. Moreover, we discovered that CYLD inhibited tumor cell proliferation and enhanced the sensitivity to cell ferroptosis in PCa in vitro and in vivo, respectively. Mechanistically, we demonstrated that CYLD suppressed the ubiquitination of YAP protein, then promoted ACSL4 and TFRC mRNA transcription. Then, we demonstrated that CYLD could enhance the sensitivity of PCa xenografts to ferroptosis in vivo. Furthermore, we discovered for the first time that there was a positive correlation between CYLD expression and ACSL4 or TFRC expression in human PCa specimens. The results of this study suggested that CYLD acted as a tumor suppressor gene in PCa and promoted cell ferroptosis through Hippo/YAP signaling.

Potential use of EGFR-targeted molecular therapies for tumor suppressor CYLD-negative and poor prognosis oral squamous cell carcinoma with chemoresistance

BACKGROUND

Tumor suppressor CYLD dysfunction by loss of its expression, triggers malignant transformation, especially drug resistance and tumor invasion/metastasis. Although loss of CYLD expression is significantly associated with poor prognosis in a large variety of tumors, no clinically-effective treatment for CYLD-negative cancer patients is available.

METHODS

We focused on oral squamous cell carcinoma (OSCC), and sought to develop novel therapeutic agents for CYLD-negative cancer patients with poor prognosis. CYLD-knockdown OSCC cells by using CYLD-specific siRNA, were used to elucidate and determine the efficacy of novel drug candidates by evaluating cell viability and epithelial-mesenchymal transition (EMT)-like change. Therapeutic effects of candidate drug on cell line-derived xenograft (CDX) model and usefulness of CYLD as a novel biomarker using patient-derived xenograft (PDX) model were further investigated.

RESULTS

CYLD-knockdown OSCC cells were resistant for all currently-available cytotoxic chemotherapeutic agents for OSCC, such as, cisplatin, 5-FU, carboplatin, docetaxel, and paclitaxel. By using comprehensive proteome analysis approach, we identified epidermal growth factor receptor (EGFR), a receptor tyrosine kinase, played key roles in CYLD-knockdown OSCC cells. Indeed, cell survival rate in the cisplatin-resistant CYLD-knockdown OSCC cells was markedly inhibited by treatment with clinically available EGFR tyrosine kinase inhibitors (EGFR-TKIs), such as gefitinib. In addition, gefitinib was significantly effective for not only cell survival, but also EMT-like changes through inhibiting transforming growth factor-β (TGF-β) signaling in CYLD-knockdown OSCC cells. Thereby, overall survival of CYLD-knockdown CDX models was significantly prolonged by gefitinib treatment. Moreover, we found that CYLD expression was significantly associated with gefitinib response by using PDX models.

CONCLUSIONS

Our results first revealed that EGFR-targeted molecular therapies, such as EGFR-TKIs, could have potential to be novel therapeutic agents for the CYLD-negative OSCC patients with poor prognosis.

Effects of immune cells and cytokines on inflammation and immunosuppression in the tumor microenvironment

Chronic inflammation and immune responses are two core element that characterize the tumor microenvironment. A large number of immune/inflammatory cells (including tumor associated macrophages, neutrophils and myeloid derived suppressor cells) as well as cytokines (such as IL-6, IL-10, TGF-β) are present in the tumor microenvironment, which results in both a chronic inflammatory state and immunosuppression. As a consequence tumor cell migration, invasion, metastasis and anticancer drug sensitivity are modulated. On the one hand, secreted cytokines change the function of cytotoxic T lymphocytes and antigen presenting cells, thereby inhibiting tumor specific immune responses and consequently inducing a special immunosuppressive microenvironment for tumor cells. On the other hand, tumor cells change the differentiation and function of immune/inflammatory cells in the tumor microenvironment especially via the NF-κB and STAT3 signaling pathways. This may promote proliferation of tumor cells. Here we review these double edged effects of immune/inflammatory cells and cytokines on tumor cells, and explored their interactions with inflammation, hypoxia, and immune responses in the tumor microenvironment. The tumor inflammatory or immunosuppressive reactions mediated by the high activity of NF-κB or STAT3 can occur alone or simultaneously, and there is a certain connection between them. Inhibiting the NF-κB or STAT3 signaling pathway is likely to curb the growth of tumor cells, reduce the secretion of pro-inflammatory factors, and enhance the anti-tumor immune response.

CYLD Alterations in the Tumorigenesis and Progression of Human Papillomavirus-Associated Head and Neck Cancers

Genetic alterations of CYLD lysine 63 deubiquitinase (CYLD), a tumor-suppressor gene encoding a deubiquitinase (DUB) enzyme, are associated with the formation of tumors in CYLD cutaneous syndrome. Genome sequencing efforts have revealed somatic CYLD alterations in multiple human cancers. Moreover, in cancers commonly associated with human papillomavirus (HPV) infection (e.g., head and neck squamous cell carcinoma), CYLD alterations are preferentially observed in the HPV-positive versus HPV-negative form of the disease. The CYLD enzyme cleaves K63-linked polyubiquitin from substrate proteins, resulting in the disassembly of key protein complexes and the inactivation of growth-promoting signaling pathways, including pathways mediated by NF-κB, Wnt/β-catenin, and c-Jun N-terminal kinases. Loss-of-function CYLD alterations lead to aberrant activation of these signaling pathways, promoting tumorigenesis and malignant transformation. This review summarizes the association and potential role of CYLD somatic mutations in HPV-positive cancers, with particular emphasis on the role of these alterations in tumorigenesis, invasion, and metastasis. Potential therapeutic strategies for patients whose tumors harbor CYLD alterations are also discussed. IMPLICATIONS: Alterations in CYLD gene are associated with HPV-associated cancers, contribute to NF-κB activation, and are implicated in invasion and metastasis.