BioScience Trends. 2016;10(3):202-209. (DOI: 10.5582/bst.2016.01097)

Promoter hypomethylation of RAR-related orphan receptor α 1 is correlated with unfavorable clinicopathological features in patients with colorectal cancer.

Kano H, Takayama T, Midorikawa Y, Nagase H

Retinoic acid receptor-related orphan receptor α (RORA) is a tumor-specific differentially methylated region. RORA mRNA expression is frequently downregulated in colorectal cancer (CRC) due to promoter methylation, and this methylation is correlated with the development of CRC. Here we investigated the correlation between the methylation status of the RORA promoter region and clinical CRC stages. The methylation status of RORA isoform 1 (RORA1) and isoform 4 (RORA4) promoters was investigated in 43 paired CRC specimens and adjacent normal tissues by quantitative DNA methylation analysis using the Sequenom MassARRAY system and bisulfite sequencing. The relationship between the methylation status of the RORA1 promoter and the CRC pathological stage was analyzed. RORA1 expression was evaluated using quantitative PCR. Sixteen of 43 CRC specimens (37%) and three CRC cell lines (Caco2, HT29, and HCT116) showed increased levels of methylation in the RORA1 promoter region compared with adjacent normal tissues, whereas no methylation was observed in the RORA4 promoter. Quantitative PCR showed downregulation of RORA1 expression both in CRC samples and cell lines. Furthermore, the RORA1 promoter hypomethylation status showed a significant correlation with unfavorable CRC stages (stages III and IV) compared with favorable stages (stages I and II, p = 0.014). Hypomethylation of the RORA1 promoter may have important clinical implications in unfavorable CRC development, and therefore, the methylation status of the RORA1 promoter may constitute a useful biomarker to determine an indication for postoperative therapy such as adjuvant chemotherapy in highly advanced CRC patients.

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