Suppression of AKT Activation Through LZK Inhibition Limits Tumor Growth in Esophageal and Head and Neck Cancers.

Esophageal squamous cell carcinoma (ESCC) is one of the deadliest cancers worldwide due to its aggressive nature and lack of knowledge of underlying oncogenic drivers, limiting treatment options. Approximately 60% of ESCC cases have amplification/overexpression of MAP3K13, which encodes the kinase LZK. Here, we found that MAP3K13-amplified ESCC exhibit therapeutic dependency on LZK, and that small-molecule inhibition of its catalytic function decreased the viability of ESCC cells with amplified MAP3K13. Inhibition of LZK suppressed tumor growth in MAP3K13-amplified ESCC patient-derived xenograft mice treated orally with a newly described LZK inhibitor. We discovered that LZK is required to sustain AKT activation in ESCC and HNSCC, where depletion, degradation, or treatment with the LZK inhibitor GNE-3511 or an improved inhibitor suppressed AKT activation. AKT activation could be rescued by expression of an LZK drug-resistant mutant, indicating suppression was specific to LZK. AKT and LZK co-localized and interacted in cells, and LZK enhanced AKT phosphorylation at S473 and T450 in vitro. This pattern of AKT phosphorylation reflected a non-catalytic scaffold function of LZK, as LZK inhibitors did not suppress AKT activation and a kinase-dead LZK mutant promoted AKT activation. AKT inhibitors reduced LZK-induced activation of AKT, indicating LZK facilitates AKT autophosphorylation. Furthermore, GNE-3511 inhibited the interaction of LZK with AKT in co-immunoprecipitation experiments. Molecular modeling supported a mechanism whereby LZK binds and dislodges AKT's PH domain to promote AKT autophosphorylation. Our findings demonstrate that MAP3K13-amplified tumors are dependent on LZK-mediated AKT scaffolding, supporting LZK inhibition as a therapeutic strategy in ESCC and HNSCC.