Reduced Cyld Expression Is An Independent Prognostic Factor In Breast Cancer: A Possible Link With Rankl-Rank Signaling

Proceedings: AACR 103rd Annual Meeting 2012‐‐ Mar 31‐Apr 4, 2012; Chicago, IL Background: Deubiquitinase CYLD plays an important role in tumorigenesis and immune response. RANKL-RANK system is required for osteoclast development and is also involved in bone metastasis in various malignancies while it has been also implicated in tumorigenesis, metastasis to distant organs other than bone in breast cancer through unknown mechanisms. Importantly, a recent study has reported that CYLD negatively regulated RANKL-RANK signaling in osteoclastogenesis. However, not only the role of CYLD but also its involvement in RANKL-RANK signaling in breast cancer is largely unknown. The purpose of this study was to elucidate clinical and biological significance of CYLD as well as its association with RANKL-RANK signaling in breast cancer. Materials and Methods: We assessed CYLD mRNA expression in 305 primary invasive breast cancer tissues including 26 matched-pair of tumoral and adjacent non-tumoral tissues, and 9 breast cancer cell lines as well as a nonmalignant breast epithelial cell line, HMEC by quantitative real-time RT-PCR. In addition, effect of CYLD knockdown by using siRNA on cell proliferation, migratory activity and the biological activity of RANKL in MDA-MB-231 cells. Results: Expression levels of CYLD mRNA were lower in tumoral lesion than the matched non-tumoral lesion in all of 26 cases. Our statistical analysis revealed that lower CYLD mRNA expression was significantly associated with reduced disease free survival rate (rog-rank, p = 0.025), irrespectively of breast cancer subtype. Multivariate analyses for disease free survival confirmed that low CYLD mRNA expression (Hazard ratio: HR 2.23, 95% CI 1.09 - 4.36, p = 0.029) in addition to estrogen receptor status (HR 0.15, 95% CI 0.05 - 0.44, p = 0.0003) and lymph node metastasis (HR 2.21, 95% CI 1.10 - 4.62, p = 0.026) were significant factors. Consistent with our clinical data, CYLD gene expression was reduced in all the breast cancer cell lines compared with HMEC cells. Repression of CYLD gene expression led to increased cell number in MDA-MB-231 cells. Interestingly, combination of CYLD knockdown and RANKL stimulation promoted cell migration while no change was observed in the setting of each alone. Conclusion: Downregulation of CYLD was common and an independent poor prognostic factor in invasive breast cancer. CYLD repression may promote breast cancer development and/ or progression in coordination with RANKL-RANK signaling. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 700. doi:1538-7445.AM2012-700