SP1 as a negative regulator of ADAMTS-8 in colorectal cancer: Evidence from functional and molecular analyses.

Epigenetic silencing of ADAMTS-8 has been linked to increased tumor aggressiveness and poor prognosis; however, its transcriptional regulation in cancer remains largely undefined. Here, we comprehensively investigated the transcriptional regulation of ADAMTS-8 by SP1, which is associated with poor clinical outcomes in colorectal cancer (CRC). SP1 levels showed a marked upward trend in the clinical and molecular subtypes of CRC. Functional analyses demonstrated that SP1 overexpression in SW480 cells increased proliferation and migration; conversely, it significantly suppressed the ADAMTS-1 and ADAMTS-8 expressions. Furthermore, this suppressive effect was found to be reversible with Mitramycin A. Luciferase reporter assays confirmed the transcriptional repressive effect of SP1 on ADAMTS-8 promoter activity. ChIP-qPCR and EMSA demonstrated the specific binding of SP1 to the ADAMTS-8 promoter (-56/+17), indicating a direct regulatory mechanism. Clinical analyses revealed that ADAMTS-1 is significantly reduced in CRC, and low ADAMTS-1 levels are associated with poor survival. The regulatory relationship between SP1 and ADAMTS-8 was further examined in osteosarcoma, where SP1 expression was significantly elevated relative to osteoblasts, while ADAMTS-8 was markedly suppressed. The association of high ADAMTS-8 expression with better survival in the TCGA-SARC cohort supported its tumor-suppressive role in osteosarcoma. Consistently, qRT-PCR confirmed the inhibitory effect of SP1 on ADAMTS-8 in SAOS-2 cells. Overall, our findings identify SP1 as a central negative regulator of ADAMTS-1 and ADAMTS-8, contributing to tumor progression in CRC and osteosarcoma. The SP1-ADAMTS axis represents a potentially important molecular network in cancer biology and may provide a basis for developing novel biomarkers or targeted therapeutic strategies.