RNA-binding protein RBM24 represses colorectal tumourigenesis by stabilising PTEN mRNA.

BACKGROUND: RNA-binding motif protein 24 (RBM24) functions as a splicing regulator, which is critical for organ development and is dysregulated in human cancers. Here, we aim to uncover the biological function of RBM24 in colorectal tumourigenesis. METHODS: Xenograft tumour model, Rbm24 knockout and Apcmin/+ mouse models were utilised. Colorectal cancer cells overexpressing or silencing RBM24 were established. RNA immunoprecipitation (RIP) assay was conducted to detect protein-RNA associations. Gene expression was measured by immunohistochemistry, western blotting, or quantitative PCR (qPCR). RESULTS: Rbm24-knockout mice developed spontaneous colorectal adenomas with lower expression of phosphatase and tensin homolog (PTEN). Immunohistochemical staining for the proliferation markers Ki-67 and pHH3 and BrdU assay showed intestinal hyperplasia in Rbm24-knockout mice compared to wild-type mice. RBM24 expression in colorectal adenoma tissues of Apcmin/+ mouse was downregulated compared with adjacent normal samples and was positively correlated with PTEN expression. In vitro, RBM24 overexpression suppressed cell proliferation, migration, invasion and increased sensitivity to 5-FU or cisplatin in CRC cells. Mechanistically, RBM24 maintained PTEN mRNA stability by directly binding to the GT-rich region at positions 8101-8251 in the 3'-UTR of PTEN mRNA, prolonging the half-life of PTEN mRNA, thereby increasing PTEN expression. Hence, low expression of RBM24 downregulated PTEN mRNA, causing the activation of PI3K-Akt signalling in CRC cells. Furthermore, RBM24 expression in CRC tissues was lower than adjacent normal samples. RBM24 expression was positively correlated with PTEN expression and negatively correlated with Ki-67 level. CRC patients with high RBM24 expression had a favourable outcome. CONCLUSIONS: Taken together, RBM24 expression is markedly lower in colorectal tumours than in para-carcinoma tissues. Rbm24-knockout mice develop spontaneous colorectal adenomas. RBM24 directly binds and stabilises PTEN mRNA, which could cause the suppression of CRC cell proliferation, migration and invasion, thereby repressing colorectal tumourigenesis. These findings support the tumour-suppressive role of RBM24. Targeting RBM24 holds strong promise for the diagnosis and treatment of CRC.

LHPP-Mediated Histidine Dephosphorylation Suppresses the Self-Renewal of Mouse Embryonic Stem Cells.

Self-renewal of embryonic stem cells (ESCs) is orchestrated by a vast number of genes at the transcriptional and translational levels. However, the molecular mechanisms of post-translational regulatory factors in ESC self-renewal remain unclear. Histidine phosphorylation, also known as hidden phosphorylation, cannot be detected by conventional experimental methods. A recent study defined phospholysine phosphohistidine inorganic pyrophosphate phosphatase (LHPP) as a histidine phosphatase, which regulates various biological behaviors in cells via histidine dephosphorylation. In this study, the doxycycline (DOX)-induced hLHPP-overexpressing mouse ESCs and mouse LHPP silenced mESCs were constructed. Quantitative polymerase chain reaction (qPCR), western blotting analysis, immunofluorescence, Flow cytometry, colony formation assays, alkaline phosphatase (AP) and bromodeoxyuridine (Brdu) staining were performed. We found that the histidine phosphorylation level was strikingly reduced following LHPP overexpression. Besides, the expression of Oct4 and Lefty1, indispensable genes in the process of ESCs self-renewal, was significantly down-regulated, while markers related to the differentiation were markedly elevated. Moreover, LHPP-mediated histidine dephosphorylation induced G0/G1 phase arrest in mESCs, suggesting LHPP was implicated in cell proliferation and cell cycle. Conversely, silencing of Lhpp promoted the self-renewal of mESCs and reversed the RA induced increased expression of genes associated with differentiation. Mechanistically, our findings suggested that the enzymatic active site of LHPP was the cysteine residue at position 226, not 53. LHPP-mediated histidine dephosphorylation lowered the expression levels of ß-catenin and the cell cycle-related genes CDK4 and CyclinD1, while it up-regulated the cell cycle suppressor genes P21 and P27. Taken together, our findings reveal that LHPP-mediated histidine dephosphorylation plays a role in the self-renewal of ESCs. LHPP-mediated histidine dephosphorylation inhibited the self-renewal of ESCs by negatively regulating the Wnt/ß-catenin pathway and downstream cell cycle-related genes, providing a new perspective and regulatory target for ESCs self-renewal.

Retroperitoneal teratoma resection assisted by 3-dimensional visualization and virtual reality: A case report.

BACKGROUND: Primary retroperitoneal tumor is a rare type of tumor with insidious onset, large tumor size at the time of diagnosis, and often extensive involvement of surrounding tissues and blood vessels in the retroperitoneum. Surgery for primary retroperitoneal tumors is technically challenging. Preoperative imaging evaluation is critical for the selection of the optimal surgical approach and can influence complete resection and recurrence rates. Three-dimensional model reconstruction combined with virtual reality is useful for preoperative assessment. CASE SUMMARY: A 17-year-old female patient was admitted for abdominal pain lasting for half a year that had been worsening for half a month. Abdominopelvic enhanced helical computed tomography revealed a retroperitoneal space-occupying lesion about 11.3 cm × 9.1 cm in size, with well-defined borders in the upper left quadrant of the abdomen. The lesion compressed the left renal artery and vein resulting in vascular displacement and deformation. A multidisciplinary team decided on the optimal treatment approach. Preoperative three-dimensional visualization and virtual reality technology were used to assess and simulate the surgical procedure. Then, retroperitoneal tumor resection along with renal artery reconstruction was decided as the treatment. Complete resection of the retroperitoneal tumor was performed. Stable blood flow was established after renal artery reconstruction. The tumor was diagnosed as mature cystic teratoma (retroperitoneal tumor) by postoperative pathologic analysis. The patient, who recovered well, was discharged after 2 wk and maintains regular follow-ups. CONCLUSION: A combination of three-dimensional reconstruction and virtual reality technology before surgery improves the rate of complete resection of retroperitoneal teratoma.