RHOXF2

RHOXF2 (also called PEPP2/THG-1) is an X-linked homeobox transcriptional repressor that functions as an oncogenic driver of proliferation and tumor progression across multiple cancer types (PMID:21874235). Its transforming capacity was established by its ability to render IL-3-dependent hematopoietic cells factor-independent and induce leukemia in mice, while its knockdown impairs gastric cancer cell growth (PMID:21874235). Mechanistically, RHOXF2 sustains a stemness program in esophageal squamous cell carcinoma by competitively binding NRBP1, thereby blocking NRBP1-mediated ubiquitination and degradation of the stemness factor SALL4 and maintaining NANOG and OCT4 expression (PMID:31864704). In triple-negative breast cancer it physically interacts with HOXC13 to activate Wnt2/β-catenin signaling, driving proliferation, invasion, and migration and suppressing apoptosis; its own promoter is activated by H3K27ac histone acetylation (PMID:38697448). Beyond these defined oncogenic interactions, the direct DNA-binding targets of RHOXF2 as a transcription factor have not been characterized in the available corpus.

1. 2011 Medium

   Established that RHOXF2 is an oncogenic transcriptional repressor capable of driving factor-independent growth and tumorigenesis, defining its core cancer-promoting role.

   Evidence Retroviral expression cloning rendering IL-3-dependent HF6 cells factor-independent, in vivo leukemia induction in mice, and shRNA knockdown in HGC27 gastric cancer cells

   PMID:21874235

   Open questions at the time

   • No direct transcriptional target genes of the repressor identified
   • Mechanism by which it confers factor independence not resolved at the molecular level
2. 2019 Medium

   Defined a post-translational mechanism by which RHOXF2 sustains cancer stemness, showing it stabilizes SALL4 by competing with NRBP1-mediated degradation.

   Evidence siRNA/shRNA knockdown in TE13 ESCC cells, Co-IP of THG-1–NRBP1 and NRBP1–SALL4, ubiquitination assay, and SALL4 rescue of tumorsphere formation

   PMID:31864704

   Open questions at the time

   • Stoichiometry and binding interface of the RHOXF2–NRBP1 competition not defined
   • Whether this mechanism operates outside ESCC unknown
3. 2020 Low

   Placed RHOXF2 as a downstream effector in a regulatory RNA axis, showing it is a direct miR-3128 target whose restoration reverses LOXL1-AS1 knockdown phenotypes.

   Evidence Luciferase reporter and RNA pull-down confirming miR-3128 binding, with overexpression rescue and proliferation/invasion assays in NSCLC cells

   PMID:32636639

   Open questions at the time

   • Molecular function of RHOXF2 in NSCLC not characterized beyond pathway placement
   • Single-lab correlative axis without direct mechanistic dissection
4. 2024 Medium

   Identified a transcription-factor partnership through which RHOXF2 activates oncogenic signaling, and revealed epigenetic control of its own expression.

   Evidence Reciprocal Co-IP and GST pull-down of RHOXF2–HOXC13, siRNA knockdown with HOXC13 rescue, ChIP-PCR and luciferase showing H3K27ac at the RHOXF2 promoter, and xenograft model in TNBC

   PMID:38697448

   Open questions at the time

   • Direct genomic binding sites of the RHOXF2–HOXC13 complex not mapped
   • How RHOXF2 mechanistically activates Wnt2 transcription unresolved

• The direct DNA-binding targets and the unifying transcriptional logic of RHOXF2 as a homeobox repressor remain undefined across these distinct cancer contexts.
• No genome-wide binding or transcriptomic map of RHOXF2 targets
• Unclear whether stemness, Wnt, and factor-independence mechanisms converge on shared targets
• No structural data on RHOXF2 protein interactions