NR1D1 and gastric cancer: In another study, an evaluation of the expression levels of RORα and REV-ERBα with immunohistochemistry and quantitative reverse transcription-polymerase chain reaction (qRT-PCR) revealed decreased expression in gastric cancer tissues compared with normal gastric tissues (p < 0.001) and the levels were associated with clinicopathological parameters, including histological grade, TNM stage, and preoperative carcinoembryonic antigen (CEA) levels [47].