LRATD2

LRATD2 (FAM84B) is an oncogenic protein that promotes tumor cell proliferation, migration, and invasion across multiple cancer types including esophageal squamous cell carcinoma, prostate, pancreatic, glioma, breast, and colorectal cancers (PMID:26759717, PMID:32291380, PMID:33759248). Its oncogenic activity depends on an HRASLS domain bearing conserved catalytic histidines H23 and H35, deletion of which abolishes invasion and anchorage-independent growth; FAM84B molecules also self-associate through this region (PMID:31205500, PMID:32183428). A central mechanism is direct binding to the C-terminal domain (189–294 aa) of NPM1, which increases nuclear NPM1, suppresses CDKN2A, and drives cell-cycle progression (PMID:35396552). FAM84B further acts upstream of Wnt/β-catenin signaling, increasing nuclear β-catenin and c-Myc in PDAC and operating through an Akt/GSK-3β axis in glioma (PMID:32291380, PMID:33759248); in prostate cancer it sustains a β-catenin-dependent MYC→WWP1→CDKN1B feedforward loop in which WWP1 ubiquitinates and degrades p27 to relieve repression of MYC (PMID:38997648). In luminal breast cancer it promotes proliferation via death receptor signaling and NF-κB p65 nuclear entry (PMID:37651838), and across cancers it converges on cell-cycle control through cyclin D1/CDK2/4/6 and p53/p21 (PMID:36419094). Upstream, FAM84B mRNA is stabilized by KIAA1429-mediated m6A modification (PMID:41329451). Whether the HRASLS catalytic histidines confer an enzymatic activity, and the structural basis of NPM1 binding, have not been characterized in the available corpus.

1. 2016 Medium

   Established that FAM84B is functionally required for tumor cell growth and invasiveness rather than merely a cancer-associated marker.

   Evidence siRNA knockdown in ESCC cell lines with proliferation, migration, and invasion assays

   PMID:26759717

   Open questions at the time

   • No molecular mechanism identified
   • Single cancer type, single lab
   • No in vivo validation
2. 2019 Medium

   Mapped the oncogenic activity to the HRASLS domain and revealed FAM84B self-association, defining the protein region needed for transformation.

   Evidence HRASLS-domain deletion mutant with soft-agar/invasion assays plus co-IP and co-localization in DU145 prostate cancer cells

   PMID:31205500

   Open questions at the time

   • Functional consequence of self-association unknown
   • No catalytic activity demonstrated
   • Single cell line
3. 2020 Medium

   Identified conserved catalytic histidines H23 and H35 within the HRASLS domain as essential for oncogenic function, sharpening the domain requirement to specific residues.

   Evidence Comparative sequence analysis with domain-deletion functional assays

   PMID:32183428

   Open questions at the time

   • No direct point-mutant of H23/H35 tested
   • No enzymatic substrate identified
   • Catalytic activity inferred from homology, not measured
4. 2020 Medium

   Placed FAM84B upstream of Wnt/β-catenin signaling in PDAC, providing a first downstream pathway linking it to proliferation and metabolism.

   Evidence siRNA knockdown/overexpression with XAV939 inhibition and xenografts in PDAC cells

   PMID:32291380

   Open questions at the time

   • Mechanism connecting FAM84B to β-catenin not resolved
   • Direct vs indirect activation unclear
   • Single lab
5. 2021 Medium

   Resolved the FAM84B→Wnt link in glioma to an Akt/GSK-3β/β-catenin axis via pharmacological epistasis.

   Evidence siRNA knockdown with p-Akt/p-GSK-3β/active β-catenin Western blots, Akt inhibition, and xenograft

   PMID:33759248

   Open questions at the time

   • How FAM84B activates Akt is unknown
   • No direct binding partner in this axis identified
6. 2022 Medium

   Identified NPM1 as a direct FAM84B partner and defined the NPM1-CDKN2A-cell-cycle output, the most direct molecular mechanism established.

   Evidence Co-IP with NPM1 C-terminal domain mapping, nuclear fractionation, and cell-cycle analysis in ESCC

   PMID:35396552

   Open questions at the time

   • FAM84B region binding NPM1 not mapped
   • No structural data
   • Single lab, no reciprocal validation across cell types
7. 2022 Medium

   Linked FAM84B to canonical cell-cycle machinery, showing knockdown induces G0/G1 arrest with cyclin/CDK loss and p53/p21 induction in glioma.

   Evidence siRNA knockdown in U87/T98 cells with flow cytometry, MTT, and cell-cycle protein Western blots

   PMID:36419094

   Open questions at the time

   • Direct vs indirect effect on p53/p21 unclear
   • Connection to NPM1/Wnt mechanisms not integrated
8. 2023 Medium

   Demonstrated a context-specific mechanism in luminal breast cancer through death receptor signaling and NF-κB p65 nuclear entry, affecting proliferation but not invasion.

   Evidence Knockout/overexpression with RNA-seq, p65 immunofluorescence, pathway Western blots, and xenograft

   PMID:37651838

   Open questions at the time

   • Mechanism of NF-κB activation by FAM84B unknown
   • Tissue specificity of pathway choice unexplained
9. 2024 Medium

   Defined a β-catenin-dependent MYC→WWP1→CDKN1B feedforward loop, integrating FAM84B's Wnt and cell-cycle outputs into a self-reinforcing circuit in prostate cancer.

   Evidence ChIP-qPCR, dual-luciferase, co-IP for WWP1-mediated CDKN1B ubiquitination, and rescue assays with xenografts

   PMID:38997648

   Open questions at the time

   • How FAM84B drives MYC expression mechanistically unresolved
   • Generality of the loop beyond prostate cancer untested
10. 2025 Medium

    Established an upstream regulatory layer, showing KIAA1429-mediated m6A modification stabilizes FAM84B mRNA to drive Wnt/β-catenin activation in colorectal cancer.

    Evidence MeRIP, qRT-PCR/immunoblotting, and KIAA1429 knockdown with FAM84B rescue in vitro and in vivo

    PMID:41329451

    Open questions at the time

    • m6A reader mediating mRNA stabilization not identified
    • Specific m6A sites on FAM84B not mapped

• Whether the HRASLS domain catalytic histidines confer a genuine enzymatic activity and what the molecular substrate is remains unresolved.
• No enzymatic assay or substrate reported
• No structural model of FAM84B or its NPM1 interface
• Unified mechanism across cancer-type-specific pathways not established