Artificial Downregulation of Ribosomal Protein L34 Restricts the Proliferation and Metastasis of Colorectal Cancer by Suppressing the JAK2/STAT3 Signaling Pathway

The highly conserved ribosomal protein L34 (RPL34) has been reported to play an essential role in the progression of diverse malignancies. RPL34 is aberrantly expressed in multiple cancers, although its significant in colorectal cancer (CRC) is currently unclear. Here, we demonstrated that RPL34 expression was higher in CRC tissues than in normal tissues. Upon RPL34 overexpression, the ability of proliferation, migration, invasion, and metastasis of CRC cells were significantly enhanced in vitro and in vivo. Furthermore, high expression of RPL34 accelerated cell cycle progression, activated the JAK2/STAT3 signaling pathway, and induced the epithelial-to-mesenchymal transition (EMT) program. Conversely, RPL34 silencing inhibited the CRC malignant progression. Utilizing immunoprecipitation assays, we identified the RPL34 interactor, the cullin-associated NEDD8-dissociated protein 1 (CAND1), which is a negative regulator of cullin-RING ligases. CAND1 overexpression reduced the ubiquitin level of RPL34 and stabilized RPL34 protein. CAND1 silencing in CRC cells resulted in a decrease in the ability of proliferation, migration, and invasion. CAND1 overexpression promoted CRC malignant phenotypes and induced EMT, and RPL34 knockdown rescued CAND1-induced CRC progression. In summary, our study indicates that RPL34 acts as a mediator, is stabilized by CAND1, and promotes proliferation and metastasis, in part, through the activation of the JAK2/STAT3 signaling pathway and induction of EMT in CRC.