MSX1 induces G0/G1 arrest and apoptosis by suppressing Notch signaling and is frequently methylated in cervical cancer

PURPOSE: The objectives of this study were to investigate the expression of MSX1 in cervical cells and tissues, the methylation status of the MSX1 promoter, the influence of overexpression of gene MSX1 on the proliferation, migration, and invasion of HeLa and SiHa cells, and finally the possible molecular mechanisms responsible for the suppressive effects of MSX1 upon cervical cancer cells. PATIENTS AND METHODS: Semi-quantitative and quantitative reverse transcription-polymerase chain reactions were used to investigate the expression levels of MSX1, and methylation-specific polymerase chain reaction (MSP) was performed to investigate promoter methylation status in cervical cancer cell lines, primary cervical tissues, and normal cervical tissues. Clone formation, Cell Counting Kit-8 (CCK-8), cell wound scratch, and transwell assays were performed to verify whether MSX1 could inhibit the proliferation and migration of cervical cancer cells. Western blot was used to analyze the effect of MSX1 upon Notch1, Jagged1, c-Myc, cleaved PARP, cleaved caspse-3, and cyclin D1 (CCND1). RESULTS: MSX1 was frequently downregulated or silenced in 60.0% (3/5) of cervical cancer cell lines. The promoter methylation of MSX1 was detected in 42.0% (42/100) of primary tumor tissues, while no methylation was observed in normal cervical tissues. Pharmacological demethylation reduced MSX1 promoter methylation levels and restored the expression of MSX1. The overexpression of MSX1 in cervical cancer cells thus inhibited the proliferation and migration of cervical cancer cells. The overexpression of MSX1 in cervical cancer cells downregulated the expression levels of Notch1, Jagged1, and c-Myc but upregulated the expression levels of CCND1, cleaved PARP, and cleaved caspase-3. CONCLUSION: MSX1 appears to be a functional tumor suppressor that regulates tumorigenesis in cervical cancer by antagonizing Notch signaling.