CDK11B

CDK11B (CDC2L1) encodes a serine/threonine protein kinase that operates across signal transduction, cell-cycle progression, RNA splicing, and protein turnover, with context-dependent roles in development and cancer (PMID:18827223, PMID:41595181). In Hedgehog signaling it acts downstream of Smoothened and upstream of Gli, binding the negative regulator Suppressor of Fused (Sufu) and relieving its repression of Gli to activate the pathway in vivo (PMID:18827223). As a catalytically active kinase it exerts tumor-suppressive functions in breast cancer, inhibiting invasion by repressing integrin β3 through suppression of ERα signaling (PMID:25106495) and limiting growth and angiogenesis by suppressing VEGF expression (PMID:26470709); both effects require kinase activity. In hepatocellular carcinoma it instead drives malignancy by promoting ubiquitin-proteasome-dependent degradation of the transcription factor SPDEF, relieving the SPDEF–miR-448–DOT1L axis to sustain stem-cell self-renewal (PMID:33328586), and its own stability is controlled by USP22-mediated deubiquitination (PMID:40341781). CDK11B regulates G2/M progression and RNA splicing via SF3B1 phosphorylation, and its inhibition triggers caspase-3–dependent apoptosis (PMID:41595181). Transcriptionally, the gene is driven by a TATA-less GC-rich promoter requiring Ets-1 and Skn-1 binding sites (PMID:15656972), and promoter DNA methylation silences expression and reduces apoptosis in keloid fibroblasts (PMID:29204684).

1. 1998 Medium

   Before functional characterization, the genomic architecture and transcript diversity of the locus were unknown; this work established CDC2L1 as part of a duplicated 1p36.3 region producing many kinase isoforms from two promoters.

   Evidence Genomic sequencing, Southern blotting, RT-PCR transcript mapping in human genomic DNA

   PMID:9750192

   Open questions at the time

   • Does not assign function to individual transcripts
   • Does not distinguish CDC2L1 from the adjacent paralog CDC2L2 functionally
2. 2004 Medium

   It was unclear how CDC2L1 expression is controlled; this work mapped the basal promoter and identified the transcription factors that drive it.

   Evidence Deletion analysis, site-directed mutagenesis, luciferase reporters, and ChIP in cultured cells

   PMID:15656972

   Open questions at the time

   • Does not connect promoter usage to physiological signals
   • Does not address isoform-specific regulation
3. 2008 High

   The role of CDK11B in a defined signaling pathway was unknown; this work placed it between Smoothened and Gli in Hedgehog signaling via Sufu.

   Evidence Kinome siRNA screen, genetic epistasis, Co-IP with Sufu, overexpression rescue, and zebrafish in vivo assays

   PMID:18827223

   Open questions at the time

   • Does not identify a direct phosphorylation substrate within the pathway
   • Mechanism by which Sufu inhibition is relieved not resolved at the molecular level
4. 2014 Medium

   Whether CDK11B influences tumor cell behavior was unaddressed; this work showed kinase-dependent suppression of breast cancer invasion via ERα/integrin β3.

   Evidence Transwell invasion, dual-luciferase reporter, qRT-PCR, ERα siRNA, and kinase-dead mutant analysis in ERα-positive breast cancer cells

   PMID:25106495

   Open questions at the time

   • Direct substrate linking kinase activity to ERα repression not identified
   • Single lab, in vitro emphasis
5. 2015 Medium

   Building on the anti-invasion role, this work extended CDK11B's tumor-suppressive function to growth and angiogenesis through kinase-dependent VEGF suppression.

   Evidence Xenograft tumorigenicity, dual-luciferase reporter, real-time PCR, kinase-dead mutant, and IHC

   PMID:26470709

   Open questions at the time

   • Mechanism linking kinase activity to VEGF transcription not defined
   • Single lab
6. 2017 Medium

   It was unknown whether epigenetic silencing modulates CDK11p58 in disease; this work showed promoter methylation suppresses expression and reduces apoptosis in keloid fibroblasts.

   Evidence Bisulfite sequencing, methylation-specific PCR, 5-aza-dC demethylation, and apoptosis assays

   PMID:29204684

   Open questions at the time

   • Does not define the apoptotic effectors downstream of CDK11p58
   • Single tissue context
7. 2020 Medium

   In contrast to its breast-cancer tumor-suppressor role, this work revealed an oncogenic function in hepatocellular carcinoma via degradation of SPDEF.

   Evidence Co-IP, ubiquitination-IP, ChIP, sphere/colony formation, and xenograft assays in HCC stem cells

   PMID:33328586

   Open questions at the time

   • Whether SPDEF degradation requires CDK11B kinase activity not established
   • Direct ubiquitin ligase recruited not identified
8. 2025 Medium

   How CDK11B protein levels are maintained in HCC was unknown; this work identified USP22 as the deubiquitinase that stabilizes CDK11B to promote proliferation.

   Evidence Flag affinity purification/mass spectrometry, Co-IP, ubiquitination assay, proliferation assays, and tumor-bearing mouse experiments

   PMID:40341781

   Open questions at the time

   • Specific ubiquitin sites on CDK11B not mapped
   • Single lab
9. 2026 Medium

   The cell-cycle and splicing functions of CDK11B in tumors were unresolved; this work linked CDK11 inhibition to G2/M arrest, SF3B1 dephosphorylation, and apoptosis in rhabdoid tumor.

   Evidence OTS964 inhibitor, flow cytometry, immunoblotting, RT-PCR splicing readouts, and xenograft model

   PMID:41595181

   Open questions at the time

   • Inhibitor OTS964 is not CDK11B-specific
   • Does not isolate CDK11B from CDK11A activity functionally

• It remains unresolved how CDK11B's opposing tumor-suppressive (breast) and oncogenic (liver) roles are determined, and what direct phosphorylation substrates connect its kinase activity to Hedgehog, splicing, and transcriptional outputs.
• No unifying direct substrate identified across contexts
• Context-dependent switch between tumor suppressor and oncogene unexplained
• No structural model of kinase-substrate engagement