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

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.