Epigenetic inactivation and tumor-suppressor behavior of NGFR in human colorectal cancer.

UNLABELLED: The nerve growth factor receptor (NGFR/p75) is a potential tumor suppressor, but its role in colorectal cancer is unknown. Here, the hypermethylation status, biologic function, and clinical relevance were determined for p75NGFR in colorectal cancer. The methylation status and expression of p75NGFR were assessed in colorectal cancer cell lines and clinical tissues by bisulfite genomic sequencing (BGS), qRT-PCR, and immunoblot assay. Methylation of p75NGFR was frequently found in colorectal cancer, leading to its silencing or downregulation, and it was effectively restored by a demethylation agent. The overexpression of p75NGFR in multiple colorectal cancer cell model systems significantly inhibited cell proliferation (concomitant with G1-phase arrest), invasion, and colony formation and induced cell apoptosis. In contrast, p75NGFR knockdown significantly promoted proliferative and invasive phenotypes. Importantly, p75NGFR methylation was observed in the majority of primary colorectal cancer specimens and was associated with histologic grade and preoperative serum CA19-9 levels. Multivariate analysis indicated that patients who lack p75NGFR have reduced overall survival (64% vs. 75%, P = 0.028) and disease-free survival (61% vs. 72%, P = 0.034) compared with p75NGFR-positive patients. In conclusion, p75NGFR is predominantly silenced or downregulated in colorectal cancer, and its biologic activities are consistent with it being a relevant tumor suppressor. IMPLICATIONS: p75NGFR is a candidate tumor suppressor and has independent prognostic potential in colorectal cancer. ©2014 American Association for Cancer Research.