Aberrant phosphorylation of human LRH1 at serine 510 is predictable of hepatocellular carcinoma recurrence

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Abstract We previously identified the AKT-phosphorylation sites in nuclear receptors and showed that phosphorylation of S379 in mouse retinoic acid γ and S518 in human estrogen receptor α regulate their activity independently of the ligands. Since this site is conserved at S510 in human liver receptor homolog 1 (hLRH1), we developed a monoclonal antibody (mAb) that recognized the phosphorylation form of hLRH1S510 (hLRH1pS510) and verified its clinicopathological significance in hepatocellular carcinoma (HCC). We generated the anti-hLRH1pS510 mAb and assessed its selectivity. We then evaluated the hLRH1pS510 signals in 157 cases of HCC tissues by immunohistochemistry because LRH1 contributes to the pathogenesis of diverse cancers. The developed mAb specifically recognized hLRH1pS510 and worked for immunohistochemistry of formalin-fixed paraffin-embedded tissues. hLRH1pS510 was exclusively localized in the nucleus of HCC cells, but the signal intensity and positive rates varied among the subjects. According to the semi-quantification, 45 cases (34.9%) showed hLRH1pS510-high, and the remaining 112 cases (65.1%) exhibited hLRH1pS510-low. There were significant differences in the recurrence-free survival (RFS) between the two groups, and the 5-year RFS rates in the hLRH1pS510-high and hLRH1pS510-low groups were 26.5% and 46.1%, respectively. In addition, high hLRH1pS510 was significantly correlated with portal vein invasion, hepatic vein invasion, and high levels of serum alpha-fetoprotein (AFP). Furthermore, multivariable analysis revealed that hLRH1pS510-high was an independent biomarker for HCC recurrence. We conclude that aberrant phosphorylation of hLRH1S510 is a predictor of poor prognosis for HCC. The anti-hLRH1pS510 mAb could provide a powerful tool to validate the relevance of hLRH1pS510 in pathological processes such as tumor development and progression.

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