The AMPK--HOXB9--KRAS axis regulates lung adenocarcinoma growth in response to cellular energy alteration.

Objective: HOXB9 is an important transcription factor associated with unfavorable outcomes in LUAD. However, natural degradation mechanism remains unclear. Methods: IHC, co-IP, gene knockout mice, Xenograft tumor formation assay, RT-qPCR, Transcriptome Sequencing, In vivo ubiquitination assays, Dual Luciferase Reporter Assay, Chromatin Immunoprecipitation, PET Imaging of Glucose Uptake in Mice and LC-MS/MS analysis. Results: Here, we showed that HOXB9 is a substrate of AMPKα and is phosphorylated at T133. Glucose deprivation and metformin treatment facilitated AMPKα-mediated HOXB9 phosphorylation, downregulating HOXB9 in AMPKα knockout mice and LUAD cells. Mechanistically, phosphorylated HOXB9 promoted E3 ligase Praja2-mediated HOXB9 degradation. Blocking HOXB9 phosphorylation by depleting AMPKα1/2 or using the HOXB9 T133A mutant promoted tumor cell growth in cell culture and mouse xenografts through upregulation of HOXB9 and KRAS, a newly identified target of HOXB9. Clinically, AMPK activation levels in LUAD samples were positively correlated with pHOXB9, and higher pHOXB9 indicated better survival of patients with LUAD. Conclusion: These findings reveal the degradation mechanism of HOXB9 and presence of an AMPK--HOXB9--KRAS axis linking glucose level-regulated AMPK activation to HOXB9 stability and KRAS gene expression, ultimately controlling LUAD progression. [ABSTRACT FROM AUTHOR]