ZBTB33/RBM15 Axis Upregulates MACC1 to Promote the Malignant Progression of Colorectal Cancer

Extensive clinical evidence has identified metastasis-associated colon cancer 1 (MACC1) as a pivotal cancer-promoting gene that actively fuels the advancement of neoplasms. However, the upstream transcriptional regulators of MACC1 and the specific posttranscriptional mechanisms involving N6-methyladenosine (m6A) modification that govern its expression remain largely undefined. This study aims to elucidate the regulatory network controlling MACC1 expression and its impact on colorectal cancer (CRC) progression.

MACC1 expression and its potential regulators were systematically analyzed using public databases, including GEPIA, TCGA, and TIMER2, alongside clinical tissue samples and cell lines (SW480, HCT-116, and SW620). Functional experiments were conducted to assess cell viability, proliferation, invasion, and ferroptosis. These methodological approaches encompassed chromatin immunoprecipitation (ChIP), RNA immunoprecipitation (RIP), methylated RNA immunoprecipitation (MeRIP), as well as dual-luciferase reporter systems. Furthermore, in vivo validation was performed using a nude mouse xenograft model.

MACC1 was significantly upregulated in CRC tissues and cell lines, and its high expression correlated with an unfavorable prognosis. Functional assays revealed that silencing MACC1 inhibited CRC cell proliferation and invasion while inducing ferroptosis. Mechanistically, RNA binding protein 15 (RBM15) was identified as a key m6A methyltransferase component that stabilized MACC1 mRNA in an insulin-like growth factor 2 mRNA-binding protein 1 (IGF2BP1)- dependent manner. Furthermore, zinc finger and BTB domain-containing 33 (ZBTB33) was found to transcriptionally activate RBM15 by binding to its promoter region. Knockdown of RBM15 inhibited CRC cell invasion and proliferation and induced ferroptosis; these effects were notably reversed by MACC1 overexpression. Moreover, ZBTB33 silencing inhibited the key malignant phenotypes of CRC cells and induced ferroptosis by regulating RBM15. Further, RBM15 depletion suppressed tumor growth, which was attenuated by the restoration of MACC1.

Our study unveils a novel ZBTB33/RBM15/MACC1 signaling axis that drives CRC progression. Clinically, these findings not only deepen the understanding of m6A-mediated posttranscriptional regulation in CRC but also identify this axis as a promising therapeutic target for overcoming ferroptosis resistance and improving patient outcomes.

These findings uncover a novel ZBTB33/RBM15/MACC1 regulatory axis in CRC, where ZBTB33 transcriptionally activates RBM15 to enhance MACC1 mRNA stability, ultimately suppressing ferroptosis and promoting tumor progression.