Abstract P1-08-11: UHRF1 promotes breast cancer progression via suppressing KLF17 expression
Authors: Gao S-P , Sun H-F , Li L-D , Jin W 
Published: March 2017

Background: UHRF1, also termed as ICBP90 or Np95, is reported to be an epigenetic regulator of DNA methylation and histone modifications, which takes pivotal functions in cell differentiation and tumorigenesis. Here, we show that UHRF1 is markedly increased in breast cancer tissues and cell lines. And patients with high UHRF1 expression have a poor prognosis compare with those in low UHRF1 expression as showed by Kaplan Meier plotter analysis. However, the underlying mechanisms of UHRF1 in breast cancer remain largely unknown. Thus, the aim of this study is to validate potential mechanisms of UHRF1 in breast cancer cells.

Methods: The stable cell lines were constructed using interference and overexpression methods and the efficiency was confirmed by western blot. Then cell proliferation and migration were evaluated by CCK8 and transwell assay. The MDA-MB-231 pCDH and pCDH-UHRF1 cells were inoculate into mouse left flank to further testify UHRF1 function in vivo. Furthermore, microarray and ChIP-seq were implemented to detect potential mechanisms and the candidate genes were assessed by ChIP and qPCR. The BSP or MSP primers were designed by the methprimer database. Genomic DNA was prepared from breast cancer cells and then the genomic DNA was bisulfite modified using EZ DNA Methylation-Gold Kit. The methylation PCR products were cloned into pMD-18T and ten positive clones were sequenced. The data were analyzed using the QUMA analyzer software.

Results: We found that UHRF1 was indeed increased in breast cancer tissues and cells. And patients with high levels of UHRF1 were likely to have a shorter disease-free survival than patients with low levels. UHRF1 overexpression can promote cell proliferation and migration while UHRF1 downregulation have inverse functions. In vivo, UHRF1 also accelerate tumor growth on mice. Mechanistic studies revealed that 9 candidate genes were obtained by analysis from ChIP-seq and microarray databases. The further verification showed that Krüppel-like factor 17 (KLF17) is the most significantly upregulated one when UHRF1 gene was depleted, with rich CpG islands on its promoter region. We also observed that an inverse relationship between the expression of UHRF1 and KLF17 both in breast cancer cell lines and tissues.What's more, cells proliferation and migration which were inhibited by UHRF1-depletion can be rescued by KLF17 silence, suggesting UHRF1 promote breast cancer proliferation and migration through downregulating KLF17 expression. Moreover, overexpression of UHRF1 increases the methylation of CpG nucleotides and reduces the expression of KLF17 while depletion of UHRF1 decreases the methylation of CpG nucleotides with elevating expression of KLF17.

Conclusion: Our results demonstrate that increased UHRF1 can promote breast cancer cell proliferation and migration by epigenetic silencing of KLF17 expression through CpG islands methylation in its promoter region. These results provide insight into the breast cancer progression process and suggest that making changes in this mechanism represent new therapeutic approaches to block breast cancer development.

Citation Format: Gao S-P, Sun H-F, Li L-D, Jin W. UHRF1 promotes breast cancer progression via suppressing KLF17 expression [abstract]. In: Proceedings of the 2016 San Antonio Breast Cancer Symposium; 2016 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2017;77(4 Suppl):Abstract nr P1-08-11.