Small leucine zipper protein promotes the metastasis of castration-resistant prostate cancer through transcriptional regulation of matrix metalloproteinase-13

Matrix metalloproteinases (MMPs) function as central modulators of tissue remodeling. Abnormal expression and altered activity of MMPs result in excessive extracellular matrix degradation and increased tumor metastasis in various cancers. Small leucine zipper protein (sLZIP), belonging to the leucine zipper transcription factor family, functions as a transcriptional regulator of genes involved in various cellular processes. However, its role in MMP expression and castration-resistant prostate cancer (CRPC) metastasis remains unclear. In this study, we investigated the role of sLZIP in MMP-13 expression and its involvement in CRPC metastasis. sLZIP increased MMP-13 transcription by directly binding to its promoter in CRPC cells. We found that the expression levels of glucocorticoid receptor (GR), which represses MMP transcription, were elevated in CRPC cells. However, sLZIP suppressed the inhibitory effect of GR and enhanced the secretion of MMP-13 in CRPC cells. sLZIP promoted cell migration and invasion; however, a specific MMP-13 inhibitor blocked sLZIP-induced cell motility. Depletion of sLZIP using the CRISPR/Cas9 system downregulated MMP-13 messenger RNA expression in PC3 cells. Mice injected with sLZIP-depleted PC3 cells showed significantly reduced metastatic tumor volume in the lung compared with mice injected with control PC3 cells. Our findings suggest that sLZIP plays an important role in MMP-13 induction and CRPC metastasis. Therefore, sLZIP inhibition could be a novel therapeutic strategy for metastatic GR-enriched CRPC.