Abstract
The emerging significance of ubiquitin-specific peptidase 21 (USP21) in stabilizing Fra-1 (FOSL1) has shed light on their involvement in promoting colorectal cancer (CRC) metastasis. Additionally, EGFR signaling has been linked reciprocally with Fra-1 activation in an MMP-dependent manner. However, the functional implications of the USP21-EGFR signaling axis in metastatic CRC (mCRC) remain incompletely understood. RNA-Seq data from tumor tissues (n = 27) and matched normal tissues (n = 27) from 27 mCRC patients were analyzed to investigate the clinical correlation between USP21 and EGFR expression. Functional studies including CRISPR/Cas9 gene editing method to generate USP21-knockout (USP21-KO) CRC cells, in vitro cancer progression and tumor formation assays, in vivo xenograft assays in NSG mice, and therapeutic assays with the USP21 inhibitor, BAY-805, were conducted. Elevated levels of USP21 and EGFR expression in mCRC patients correlated with poorer survival outcomes. Mechanistically, USP21 was found to enhance EGFR stability by deubiquitinating EGFR, resulting in reduced EGFR levels in USP21-KO colon cancer cells. USP21-KO colon cancer cells exhibited significantly attenuated cell proliferation, migration, colony formation, and 3D tumor spheroid formation in response to EGF. Furthermore, tumorigenic activity in vivo was notably diminished in NSG mice xenografted with USP21-KO colon cancer cells. Notably, the USP21 inhibitor, BAY-805, demonstrated a remarkable inhibitory effect on the formation of 3D tumor spheroids in colorectal cancer cells stimulated with EGF. These findings provide valuable insights into the potential of USP21 as both a therapeutic target and a predictive biomarker for intervening in mCRC induced by EGF.