Background: Hepatocellular carcinoma (HCC) is a frequently diagnosed cancer and a leading cause of cancer-related death worldwide. Its rapid progression, combined with the limited treatment options at late stages, imposes the need for early detection and aggressive intervention. Based on the knowledge that hepatocarcinogenesis is significantly influenced by histone acetylation, we directed our search for novel HCC therapeutics among histone deacetylation inhibitors (HDACi). The aim of the present study was to investigate the effect of HDAC1/2 inhibitor Romidepsin in the well-established mouse model of diethylnitrosamine (DEN)-induced HCC. Materials and Methods: C56BL/6 mice were treated with Romidepsin at the critical point of 10 months after DEN challenge and their livers were examined 2 months later using histopathology and morphometry. Protein levels were assessed in serum using ELISA and in liver tissues using Western blot and immunohistochemistry (in-situ detection). Gene expression was quantified using real-time PCR. Results: Romidepsin suppressed cancer progression. This effect was associated with decreased proliferation and increased apoptosis of cancer cells. The cell cycle regulator CK2a, the anti-inflammatory molecule PPAR-γ, and the tumor suppressors PTEN and CYLD were upregulated in treated HCC. By contrast, the expression of PI3K, NF-κB p65 and c-Jun was reduced. In line with this result, the levels of two major apoptosis regulators, ie, BAD and the multifunctional protein c-Met, were lower in the blood serum of treated mice compared to the untreated mice with HCC. Conclusion: These findings suggest that Romidepsin, a drug currently used in the treatment of lymphoma, could also be considered in the management of early-stage HCC.

Downregulation of the cylindromatosis (CYLD) tumor suppressor has been associated with breast cancer development and progression. Here, we report a critical role for CYLD in maintaining the phenotype of mammary epithelial cells in vitro and in vivo. CYLD downregulation or inactivation induced an epithelial to mesenchymal transition of mammary epithelial cells that was dependent on the concomitant activation of the transcription factors Yes-associated protein (YAP)/transcriptional coactivator with PDZ-binding motif (TAZ) and transforming growth factor beta (TGFβ)signaling. CYLD inactivation enhanced the nuclear localization of YAP/TAZ and the phosphorylation of Small Mothers Against Decapentaplegic (SMAD)2/3 proteins in confluent cell culture conditions. Consistent with these findings were the hyperplastic alterations of CYLD-deficient mouse mammary epithelia, which were associated with enhanced nuclear expression of the YAP/TAZ transcription factors. Furthermore, in human breast cancer samples, downregulation of CYLD expression correlates with enhanced YAP/TAZ-regulated target gene expression. Our results identify CYLD as a critical regulator of a signaling node that prevents the coordinated activation of YAP/TAZ and the TGFβ pathway in mammary epithelial cells, in order to maintain their phenotypic identity and homeostasis. Consequently, they provide a novel conceptual framework that supports and explains a causal implication of deficient CYLD expression in aggressive human breast cancers.

Background/Aim: The cylindromatosis tumor suppressor (CYLD) has been implicated in the inhibition of human breast cancer development by virtue of the poor prognosis of patients with down-regulated CYLD expression. In order to investigate the mechanism of breast cancer suppression by CYLD, in the present study, cellular and molecular aspects of CYLD-dependent phenotypic regulation of different types of human breast cancer cell lines were analyzed. Materials and Methods: CYLD expression was down-regulated by RNA interference in human breast cancer cell lines. Parental and CYLD-deficient cell lines were evaluated for their viability, migratory capacity, anchorage-independent growth and chemoresistance. Wild-type and mutated forms of CYLD were also evaluated for their ability to suppress the clonogenic potential of breast cancer cells. Results: CYLD down-regulation enhanced the survival and migratory properties of basal and luminal breast cancer cell lines. In addition, down-regulation of CYLD expression enhanced the ability of human breast cancer cells to grow in an anchorage-independent manner and could be associated with resistance to chemotherapeutic drugs. The growth-suppressive properties of CYLD on breast cancer cell lines were dependent on its de-ubiquitinating activity and its amino terminal cytoskeleton-interacting region. Conclusion: Our results establish a broad range of tumor-suppressive properties that are conferred by CYLD in basal and luminal human breast cancer cells and support the significance of targeted de-ubiquitination by CYLD in breast cancer cell growth suppression.

CYLD is a tumor suppressor gene coding for a deubiquitinating enzyme that has a critical regulatory function in a variety of signaling pathways and biological processes involved in cancer development and progression, many of which are also key modulators of somatic cell reprogramming. Nevertheless, the potential role of CYLD in this process has not been studied. With the dual aim of investigating the involvement of CYLD in reprogramming and developing a better understanding of the intricate regulatory system governing this process, we reprogrammed control (CYLD^WT/WT) and CYLD DUB-deficient (CYLD^Δ9/Δ9) mouse embryonic fibroblasts (MEFs) into induced pluripotent stem cells (iPSCs) through ectopic overexpression of the Yamanaka factors (Oct3/4, Sox2, Klf4, c-myc). CYLD DUB deficiency led to significantly reduced reprogramming efficiency and slower early reprogramming kinetics. The introduction of WT CYLD to CYLD^Δ9/Δ9 MEFs rescued the phenotype. Nevertheless, CYLD DUB-deficient cells were capable of establishing induced pluripotent colonies with full spontaneous differentiation potential of the three germ layers. Whole proteome analysis (Data are available via ProteomeXchange with identifier PXD044220) revealed that the mesenchymal-to-epithelial transition (MET) during the early reprogramming stages was disrupted in CYLD^Δ9/Δ9 MEFs. Interestingly, differentially enriched pathways revealed that the primary processes affected by CYLD DUB deficiency were associated with the organization of the extracellular matrix and several metabolic pathways. Our findings not only establish for the first time CYLD’s significance as a regulatory component of early reprogramming but also highlight its role as an extracellular matrix regulator, which has profound implications in cancer research.