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LMTK3
LMTK3 Full Name
lemur tyrosine kinase 3
LMTK3 Introduction
LMTK3 encodes a serine/threonine protein kinase originally identified through kinome-wide screens for regulators of the estrogen receptor alpha (ERalpha), the central driver of the most common subtype of breast cancer. LMTK3 belongs to a small family of tyrosine kinases with unusual substrate preference, and its catalytic domain has been structurally modeled to guide the design of ATP-competitive compounds. Unlike many kinases, LMTK3 acts as a pleiotropic modulator of ERalpha rather than as a simple upstream activator. It phosphorylates ERalpha itself, protecting the receptor from proteasomal degradation, and it dampens protein kinase C and AKT signaling to increase forkhead box O3 binding at the ESR1 promoter, thereby reinforcing estrogen-responsive transcription. Intriguingly, the LMTK3 locus shows evidence of Darwinian positive selection in the human lineage, a pattern consistent with its proposed role in the distinctive human susceptibility to ERalpha-positive breast tumors. These properties immediately marked LMTK3 as both a candidate biomarker and a therapeutic target.
Figure 1. LMTK3 can act as a DNA binding protein that represses tumor suppressor-like genes. (Source: Xu Y, et al. 2015)
Subsequent work has expanded the oncogenic profile of LMTK3 well beyond endocrine pathways. Clinical studies across large breast cancer cohorts linked higher LMTK3 expression, both cytoplasmic and nuclear, to high tumor grade, advanced stage, and poorer disease-free and overall survival, validating it as a prognostic marker. Experimentally, LMTK3 overexpression confers resistance not only to endocrine therapies but also to cytotoxic chemotherapy such as doxorubicin, in part by blunting ataxia-telangiectasia mutated kinase activation and delaying DNA double-strand break formation. LMTK3 is upregulated after chemotherapy in patient tumor pairs, suggesting a selection pressure that favors survival of resistant clones. In ER-negative disease it instead promotes invasion through integrin beta1. These convergent activities have motivated chemical efforts to discover LMTK3 inhibitors, including sulfonamide-based compounds identified by high-throughput screening. Because LMTK3 signaling intersects with both hormone dependence and DNA-damage responses, it is increasingly regarded as a nodal point that links breast cancer subtypes through shared survival circuitry. As a kinase whose inhibition could dismantle both hormonal and cytotoxic resistance, LMTK3 remains an active frontier in breast cancer therapeutics.
Alternate Names for LMTK3
LMTK3; lemur tyrosine kinase 3; serine/threonine-protein kinase LMTK3; KIAA1883; LMR3; TYKLM3;
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