MRPL9

MRPL9 functions as an oncogenic driver across multiple epithelial cancers, where its activation promotes proliferation, migration, and survival (PMID:36233293, PMID:39761726). In vivo CRISPRa activation of Mrpl9 in mouse liver drives hepatocellular carcinoma and shortens survival, and transcriptomic profiling of the resulting tumors links Mrpl9 to altered expression of mitochondrial function-related genes, establishing it as a bona fide chromosome 1q HCC driver (PMID:39761726). At the molecular level, MRPL9 physically interacts with GGCT (γ-glutamylcyclotransferase), and this interaction activates MAPK/ERK signaling to promote proliferation and migration, with knockdown of either partner suppressing xenograft growth and lung metastasis (PMID:36233293). Beyond these findings, the mechanism by which MRPL9 connects to the oncogenic signaling pathways it influences has not been further characterized in the available corpus.

1. 2021 Low

   Whether MRPL9 contributes functionally to cancer cell survival was untested; knockdown established it as a determinant of clonogenic potential and chemosensitivity in triple-negative breast cancer.

   Evidence siRNA knockdown with colony-forming and paclitaxel sensitivity assays in TNBC cell lines

   PMID:34703883

   Open questions at the time

   • No molecular mechanism or pathway placement for MRPL9
   • Single method per readout from one lab
   • No in vivo validation
2. 2022 Medium

   The first direct molecular partner and signaling consequence of MRPL9 was defined: it binds GGCT and activates MAPK/ERK to drive proliferation and migration.

   Evidence Reciprocal co-immunoprecipitation, immunofluorescence, lentiviral overexpression/knockdown, and xenograft/metastasis assays in papillary thyroid cancer

   PMID:36233293

   Open questions at the time

   • Mechanism by which MRPL9-GGCT activates ERK not resolved
   • Single lab
   • Relationship to MRPL9's mitochondrial ribosomal role unaddressed
3. 2023 Low

   MRPL9's pro-tumorigenic activity was extended to lung cancer and the HCC, linking it to c-MYC/ZEB1-driven EMT and to G1/S cell cycle progression with elevated serum levels in patients.

   Evidence siRNA knockdown and overexpression with proliferation/migration assays, c-MYC interference with ZEB1 readout, flow cytometry cell cycle analysis, and ELISA of serum MRPL9

   PMID:36684217 PMID:37343379

   Open questions at the time

   • MRPL9-cMYC link inferred from expression correlation without direct biochemical assay
   • No mechanism establishing how MRPL9 acts upstream of c-MYC
   • Serum elevation is associative
4. 2025 Medium

   Whether MRPL9 is a causal cancer driver rather than a correlate was resolved by in vivo gain-of-function, establishing it as a chromosome 1q HCC driver that perturbs mitochondrial function-related gene expression.

   Evidence In vivo CRISPRa activation in mouse liver with survival analysis and RNA sequencing of tumors, validated in independent cohorts

   PMID:39761726

   Open questions at the time

   • How MRPL9 activation alters mitochondrial gene expression is undefined
   • Connection between transcriptomic changes and proliferation not mechanistically dissected
   • Single lab

• How MRPL9's canonical mitochondrial ribosomal role mechanistically connects to its GGCT/MAPK-ERK and c-MYC-linked oncogenic signaling remains unresolved.
• No structural or biochemical basis for MRPL9-GGCT-ERK activation
• No direct evidence linking ribosomal function to signaling outputs
• Mechanism of c-MYC regulation not established