GTF2I

Overview

GTF2I encodes TFII-I (Transcription Factor II-I), a multifunctional transcription factor involved in regulating gene expression downstream of receptor tyrosine kinase and immune receptor signaling. In thymic epithelial tumors (TETs), GTF2I harbors a highly recurrent hotspot missense mutation that defines an indolent subtype of thymoma.

Alterations observed in the corpus

  • Recurrent missense hotspot chr7:74146970 T>A (p.Leu404His in the β isoform; p.Leu383His in the δ isoform) occurs at high frequency in indolent thymomas (types A/AB, 78% combined) and represents the dominant driver in this disease subset; predicted deleterious by SIFT/PolyPhen-2; alters a noncanonical RXXL destruction box causing post-transcriptional TFII-I stabilization. Only 2/83 GTF2I-mutant patients died of tumor progression vs 26/121 (21%) wild-type (P<0.0001), establishing it as a favorable prognostic biomarker. PMID:24974848

Cancer types (linked)

  • THYM (thymoma/thymic epithelial tumors): The GTF2I p.Leu404His hotspot is the defining molecular alteration of indolent type A/AB thymomas (78% combined); markedly less frequent in aggressive thymic carcinomas, supporting a molecular dichotomy between these histologic subtypes. PMID:24974848

Co-occurrence and mutual exclusivity

  • GTF2I mutation is mutually exclusive with the aggressive thymic carcinoma molecular profile (TP53/CYLD/CDKN2A/BAP1/PBRM1 mutations, high copy-number burden). PMID:24974848
  • FOS mRNA is upregulated in GTF2I-mutant tumors, consistent with TFII-I-driven transcriptional regulation. PMID:24974848

Therapeutic relevance

  • The GTF2I mutation acts as a cell-growth–promoting (not strongly transforming) oncogene and is not directly druggable based on current characterization; its primary value is prognostic and diagnostic. A single targeted assay (chr7:74146970 T>A) can identify the favorable GTF2I-mutant subgroup. PMID:24974848

Open questions

  • Two non-mutually-exclusive models: (1) GTF2I mutation marks a distinct indolent lineage; (2) GTF2I mutation is a founder event lost via clonal evolution in aggressive tumors — cannot be distinguished without multiregion sampling. PMID:24974848
  • The precise molecular mechanism by which p.Leu404His stabilizes TFII-I beyond the proposed RXXL destruction-box disruption remains incompletely understood.
  • Findings require confirmation in an independent, well-annotated TET cohort.

Sources

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