PUF60-Regulated Isoform Switching of MAZ Modulates Gastric Cancer Cell Migration.

[BACKGROUND] As an essential transcription factor, Myc-associated zinc-finger protein (MAZ) is frequently upregulated in many human tumors and is a well-documented oncogene. However, we found high expression of MAZ was closely associated with good survival outcomes in patients with stomach adenocarcinoma (STAD), and the underlying mechanism involved remains to be elucidated. We hypothesize that alternative splicing of MAZ plays an important role.

[METHODS] Pan-cancer analysis of MAZ expression and prognostic significance was performed using The Cancer Genome Atlas (TCGA) data, with emphasis on its divergent prognostic impact in gastric cancer (GC). MAZ protein levels were further validated in 356 GC tissue samples via immunohistochemistry. Functional investigations encompassed MAZ knockout (KO) and isoform-specific rescue experiments to assess GC cell migration, alongside quantification of MAZ alternative splicing rates (PSI). Additionally, RNA immunoprecipitation sequencing (RIP-seq) identified PUF60-mediated regulation of MAZ isoforms.

[RESULTS] MAZ was upregulated in GC but served as an independent protective prognostic factor. MAZ-KO enhanced GC cell migration, while isoform-specific re-expression revealed divergent roles: MAZ-2 promoted migration, whereas MAZ-1 and MAZ-3 suppressed it. Notably, MAZ-2 is highly expressed in GC and is associated with poor survival prognosis of patients. Lower PSI values of MAZ-2 were detected in GC. MAZ transcripts were directly bound by PUF60. PUF60 knockdown caused MAZ splice isoform switch, thereby enhancing GC cell migration.

[CONCLUSION] The prognostic difference of MAZ in GC stems from isoform-specific functional antagonism, with cell migration phenotypes governed by the MAZ-1/3 versus MAZ-2 ratio. Targeting MAZ alternative splicing, particularly via PUF60 modulation, represents a novel therapeutic strategy.