MITF regulates autophagy and extracellular vesicle cargo in gastrointestinal stromal tumors.

The role of Microphthalmia-associated Transcription Factor (MITF) in gastrointestinal stromal tumors (GISTs) remains unclear, although previous studies suggest it contributes to tumor growth regulation. Previously, we demonstrated that MITF depletion reduces GIST cell proliferation and viability, accompanied by decreased expression of BCL-2 and CDK2. To elucidate the mechanisms underlying MITF function in GISTs, we performed chromatin immunoprecipitation and sequencing (ChIP-seq) as well as RNA sequencing. Integrated analyses revealed that MITF directly regulates genes involved in lysosome biogenesis, vesicle trafficking, autophagy, and the mTOR signaling pathway. Transcriptomic profiling following MITF silencing further demonstrated enrichment of differentially expressed genes in PI3K/ mTOR signaling, with downstream effects on tumor growth and autophagy. We next examined the functional consequences of MITF loss on mTOR inhibition-induced autophagy and on extracellular vesicle (EV) content and secretion, given their known interplay in tumor progression. MITF depletion reduced LC3-II levels and impaired autophagy flux, confirming its role in regulating autophagy in GISTs. EV size and number remained unaffected; however, silencing MITF altered EV cargo and notably decreased KIT expression in both cells and EVs. As KIT-containing EVs have been implicated in GIST invasion, these findings suggest that MITF contributes to tumor progression through coordinated regulation of autophagy and EV-mediated signaling. Collectively, our results identify MITF as a key regulator of GIST biology, highlighting its potential as a therapeutic target to limit tumor growth and metastasis.