RPS6KB2

RPS6KB2 (S6K2) is a kinase that acts as a pro-tumorigenic effector within PI3K/AKT signaling, where its expression and activity promote cancer cell proliferation, migration, and survival (PMID:40886264, PMID:38281249). In B-cell non-Hodgkin lymphoma, its transcription is directly activated by the transcription factor USF1 binding to its promoter, and its loss is rescued by AKT activation, placing RPS6KB2 upstream of the AKT/HDM2/p53 axis; knockdown reduces proliferation, migration, and tumor growth while promoting apoptosis (PMID:40886264). Consistent functional dependencies are observed in hepatocellular carcinoma, where knockdown suppresses proliferation, invasion, and migration and alters apoptotic (Bax/Bcl-2) and matrix-remodeling (MMP2/MMP9) markers while enhancing proinflammatory cytokine output (PMID:38281249). Beyond these phenotypic and transcriptional-regulatory observations, no direct biochemical characterization of RPS6KB2 substrates, catalytic mechanism, or structure is present in the available corpus.

1. 2017 Low

   Established that rps6kb2 expression correlates spatiotemporally with active tissue transformation, providing the first developmental-context association for the gene.

   Evidence Genetic linkage mapping, qRT-PCR, and in situ hybridization in a Chinese tongue sole ortholog

   PMID:28779262

   Open questions at the time

   • Expression-only association in a fish ortholog with no functional manipulation
   • No demonstration of a causal role in metamorphosis
   • No connection to a defined signaling pathway
2. 2024 Low

   Showed that RPS6KB2 is functionally required for cancer cell proliferation, invasion, and migration, framing it as a survival/migration driver rather than a passive marker.

   Evidence siRNA knockdown with EdU, wound-healing, Transwell, and apoptosis/migration marker western blots in hepatocellular carcinoma cells

   PMID:38281249

   Open questions at the time

   • Single knockdown approach with phenotypic readouts only
   • No direct mechanistic pathway linkage
   • Marker changes do not establish direct substrates or upstream regulators
3. 2025 Medium

   Defined how RPS6KB2 is transcriptionally controlled and where it sits in oncogenic signaling, linking USF1-driven expression to the AKT/HDM2/p53 axis.

   Evidence Promoter analysis, RT-qPCR, IHC, siRNA knockdown, and AKT-activator (SC79) rescue with proliferation/migration/apoptosis assays in B-cell non-Hodgkin lymphoma

   PMID:40886264

   Open questions at the time

   • No in vitro reconstitution of the USF1–promoter interaction beyond binding inference
   • Connection to HDM2/p53 inferred from rescue rather than direct biochemistry
   • Kinase substrates mediating the phenotype not identified
4. 2025 Low

   Placed RPS6KB2 as a downstream readout of a lncRNA-controlled PI3K/AKT feed-forward circuit, expanding its upstream regulatory context.

   Evidence RNA-seq, CyKILRb knockdown/overexpression, and PI3K/AKT inhibitor treatment with proliferation and clonogenic assays (preprint)

   PMID:bio_10.1101_2025.10.13.682173

   Open questions at the time

   • Preprint, not peer-reviewed
   • RPS6KB2 measured as a downstream readout without direct manipulation
   • Mechanism linking CyKILRb/PIK3R2 to RPS6KB2 expression unresolved

• The direct biochemical activity of RPS6KB2 — its kinase substrates, catalytic regulation, and structural basis — remains uncharacterized in this corpus.
• No substrate identified
• No structural or biochemical kinase characterization
• Pathway placement rests on rescue/correlative rather than direct enzymatic evidence