Human Cancer Biology HIC1 Modulates Prostate Cancer Progression by Epigenetic Modification

Purpose: Prostate cancer is the second leading cause of cancer deaths among men in Western counties, which has also occurred in Chinese male with markedly increasing incidence in recent years. Although the mechanism underlying its progression still remains unclear, epigenetic modifications are important ethological parameters. The purpose of this study is to determine the methylation status and function of hypermethylatioted in cancer 1 (HIC1) in prostate cancer progression. Experimental Design: The methylation status of HIC1 promoter was assayed in cell lines, tissues, and plasma of patients with prostate cancer by using methylation-specific PCR and bisulfate sequencing PCR. The ability of HIC1 to regulate proliferation, migration, and invasion was assessed by MTT, scratch-healing assay, and reconstituted extracellular matrices in porous culture chambers. Tumorigenesis, metastases, and bone destruction were analyzed in mice bearing prostate cancer cells restoring HIC1 by using Xenogen IVIS with radiographic system and small-animal positron emission tomography computed tomographic images.Microarrayswere searched for genes that had correlated expressionwithHIC1mRNA. Reporter gene assays were used to determine whether HIC1 affected the expression of CXCR7, and chromatin immunoprecipitation was used to determine whether HIC1 bound to CXCR7 promoters. All P values were determined using 2-sided tests. Results:Themethylation status of 11CpG siteswithinHIC1promoterwas abundantlymethylated in cell lines, tissues, and plasma of patients with prostate cancer compared with those of respective normal controls. Restoring HIC1 expression in prostate cancer cells markedly inhibited proliferation, migration, and invasion and induced the apoptosis in these cells. Moreover, mice bearing prostate cancer–restoring HIC1 cells had amarked effect on reducing tumor growth,multiple tissuemetastases, and bone destruction. Notably, we also identified that the chemokine receptor CXCR7 is a direct downstream target gene of HIC1. Finally,we showed thatCXCR7promoter in prostate cancer cells is negatively regulated byHIC1,whichmay be responsible for prostate cancer progression. Conclusions:Our data show for the first time that hypermethylation of HIC1 promoter results in loss of its repressive function, responsible for prostate cancer progression and invasion. These findings suggest that therapies targeting epigenetic events regulating HIC1 expression may provide a more effective strategy for prostate cancer treatment. Clin Cancer Res; 19(6); 1400–10. 2012 AACR.