miR-193b-3p suppresses lung cancer cell migration and invasion through PRNP targeting

Tumor metastasis is responsible for approximately 90% of mortality in lung cancer. Understanding the molecular mechanisms of lung cancer metastasis is crucial for developing new treatment strategies. Cellular prion protein (PrPc), encoded by PRNP gene, was previously found to enhance lung cancer invasiveness. However, research on the post-transcriptional regulation of PRNP remains limited.

Dual-luciferase reporter assays identified miRNAs targeting the PRNP 3'-UTR, and RNA immunoprecipitation (RIP) confirmed the interaction between miR-193b-3p and PRNP mRNA. Promoter deletions and chromatin immunoprecipitation (ChIP) assays established c-Jun as a transcriptional repressor of miR-193b-3p. Functional validation of the c-Jun-miR-193b-3p-PrPc axis was conducted using transwell assays, LNA-in situ hybridization, RT-PCR, Western blot, and immunohistochemistry. Subcutaneous mouse xenograft models assessed the anti-tumor effects of miR-193b-3p in vivo.

We demonstrated that miR-193b-3p downregulates PrPc expression by directly targeting the 3'-UTR of PRNP. Overexpression of miR-193b-3p significantly suppressed PRNP expression at both mRNA and protein levels, and reduced lung cancer cell migration, invasion and proliferation, which was reversed by PrPc overexpression. Conversely, miR-193b-3p silencing enhanced PRNP expression as well as those oncogenic properties, which were mitigated by PRNP knockdown. Spearman correlation analysis revealed a significant negative association between miR-193b-3p and PrPc expression in lung cancer tissues (p = 0.017), and Kaplan-Meier survival analysis demonstrated that high PrPc (p = 0.039) or low miR-193b-3p (p = 0.027) expression correlated with poorer overall survival. Intra-tumoral injection of the miR-193b-3p mimic in mouse xenograft models significantly reduced tumor volume. In addition, c-Jun was identified as a transcriptional repressor of miR-193b-3p. Functional studies revealed that c-Jun knockdown inhibited lung cancer cell migration, invasion, and proliferation, effects that were reversed by either PrPc overexpression or miR-193b-3p inhibitor treatment. A significant association between PrPc and c-Jun expression in lung cancer tissues (p = 0.004) was observed. High expression of PrPc and/or c-Jun was found to be associated with poor overall survival of patients (p < 0.05).

This study is the first to uncover a novel regulatory pathway where c-Jun acts as a transcriptional repressor of miR-193b-3p, leading to PRNP upregulation, which promotes lung cancer migration and invasion. This previously unrecognized c-Jun-miR-193b-3p-PrPc axis also provides valuable insights for the potential development of new therapeutic strategies against lung cancer metastasis through RNA-targeting technology.