Clinical significance of CYLD downregulation in breast cancer

Abstract

Cylindromatosis (CYLD) is a tumor suppressor gene that is mutated in familial cylindromatosis, a rare autosomal dominant disorder associated with numerous benign skin adnexal tumors. CYLD is now known to regulate various signaling pathways, including transforming growth factor-β signaling, Wnt/β-catenin signaling, and NF-κB signaling by deubiquitinating upstream regulatory factors. Downregulation of CYLD has been reported in several malignancies; however, the clinical significance of CYLD expression in many malignancies, including breast cancer, remains to be elucidated. This study investigated the clinical significance of CYLD in breast cancer and its roles in tumor progression. We evaluated CYLD expression in matched normal breast tissue samples and tumor breast tissue samples from 26 patients with breast cancer and in a series of breast cancer cell lines. In addition, by means of immunohistochemistry, we investigated CYLD protein expression and its clinical significance in 244 breast cancer cases. We also analyzed the effects of CYLD repression or overexpression on breast cancer cell viability, cell migration, and NF-κB activity with or without receptor activator of NF-κB ligand (RANKL) stimulation. Breast cancer tissues demonstrated significantly reduced CYLD mRNA expression compared with normal breast tissues. Downregulation of CYLD promoted cell survival and migratory activities through NF-κB activation, whereas CYLD overexpression inhibited those activities in MDA-MB-231 cells. As an important finding, CYLD overexpression also inhibited RANKL-induced NF-κB activation. Our immunohistochemical analysis revealed that reduced CYLD protein expression was significantly correlated with estrogen receptor negativity, high Ki-67 index, high nuclear grade, decreased disease-free survival, and reduced breast cancer-specific survival in primary breast cancer. Moreover, reduced CYLD expression was an independent factor for poor prognosis in breast cancer. CYLD downregulation may promote breast cancer metastasis via NF-κB activation, including RANKL signaling.

Down-regulation of the Tumor Suppressor CYLD Enhances the Transformed Phenotype of Human Breast Cancer Cells

“…Most importantly we have demonstrated for the first time, that CYLD down-regulation enhances the ability of basal and luminal types of breast cancer cells to grow in an anchorage independent manner. Anchorageindependent growth is a hallmark of aggressive cancer cells and our findings are consistent with the correlation of patient poor prognosis with down-regulated CYLD expression (3).…”

“…However, the causative role of CYLD down-regulation in the deregulation of homeostatic mechanisms of various cell types that lead to transformation has not been established. Previous studies have indicated that increased expression of CYLD in two basal-type breast cancer cell lines (BT-549 and MDA-MB-231) promotes their apoptosis whereas down-regulation of CYLD in MDA-MB-231 inhibits apoptosis and promotes cell migration (3,16,17). In the present study we demonstrated for the first time, that the direct growth and migratory-suppressive role of CYLD is also evident in a luminal type breast cancer cell line (MCF7) and an additional basal type breast cancer cell line (HCC1937).…”

“…Down-regulation of CYLD expression has been associated with the resistance of breast cancer to chemotherapeutic agents in patients (3). In order to determine whether down-regulation of CYLD can confer chemoresistance to breast cancer cells the effect of chemotherapeutic agents doxorubicin and etoposide on the survival of control and CYLD-deficient HCC1937 cells was evaluated.…”

“…Furthermore, a correlation between down-regulation of CYLD by the overexpression of miR182-5p and enhanced oncophenotypic characteristics of human breast cancer MCF7 cells was reported, although it was not demonstrated whether CYLD down-regulation is responsible for the observed phenotype (18). Finally, it has been shown that exogenous expression of CYLD in the MDA-MB-231 breast cancer cell line increased apoptosis and reduced their migratory ability, whereas down-regulation of CYLD in the same cell line has the opposite effects (3).…”

Downregulation of miR-362-5p inhibits proliferation, migration and invasion of human breast cancer MCF7 cells

“…CYLD has been revealed to play a central role in regulating various signaling pathways, including transforming growth factor-β, Wnt/β-catenin, c-Jun N-terminal kinase and nuclear factor-κB (NF-κB) signaling, and thus regulates the promotion of cancer development and progression (13)(14)(15)(16). Furthermore, the downregulation of CYLD has been reported in several malignancies (17)(18)(19)(20). Previous studies have revealed that CYLD expression is downregulated in breast cancer tissues compared with normal breast tissues (2,17).…”