Role Of MAP4K4 Research Articles

MAP4K4 is Involved in the Neuronal Development of Retinal Photoreceptors

Differentiated from multipotent neural progenitors, the development of retinal photoreceptors is under sophisticated programming of multiple genes. Mitogen-activated protein kinase kinase kinase kinase-4 (MAP4K4) is one of the upstream regulators in the mitogen-activated protein kinase (MAPK) signaling pathway, associated to neurodegeneration. However the role of MAP4K4 in retina—an extension of neural system—remains unknown. In the present study, we generated knockout models of C57BL/6j mice in vivo and 661W cells in vitro to unfold the mechanism of MAP4K4 during neuronal development of retinal photoreceptors. We identified the linkage between the Map4k4 ablation induced murine homozygous lethality and neural tube malformation during the embryonic phase from EM9.5 to EM10.5, providing a collateral evidence for the involvement of MAP4K4 in early stage embryonic neural formation. To further clarify the participation of MAP4K4 in neurogenesis of photoreceptors, we subjected 661W cells of both Map4k4 +/+ and Map4k4 -/- to staurosporine. Later, spatiotemporal development and remodeling of photoreceptor cells were detected. Ablation of Map4k4 leaded to vulnerability of photoreceptor nerites during induced neuronal development. By monitoring transcriptional and protein variation of MAPK signaling pathway targeted factors, we discovered the imbalanced neurogenesis factors occurring in Map4k4 -/- cells. MAP4K4 promoted jun proto-oncogene (c-JUN) phosphorylation and recruited other factors related to nerve growth, convoying the photoreceptors to robust formation of neurites. Together, MAP4K4 showed decisiveness in the programming fate of retinal photoreceptors through molecular modulations, which may be providing a new insight into the blueprint of visual formation. Funding Statement: This study was supported by the National Natural Science Foundation of China (81670874 and 81670885), the Natural Science Foundation of Gurangdong Province of China (2020A1515010144), the Fundamental Research Funds and the Open Research Funds of the State Key Laboratory of Ophthalmology. Declaration of Interests: The authors declare no conflicts of interest. Ethics Approval Statement: All animal experiments in this study were approved by and in compliance with the guides of the Animal Experimentation Ethics Committee of State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangzhou, China (Approval Number: 2017-083). All animal experiments were performed in accordance with the Association for Research in Vision and Ophthalmology (ARVO) Statement for the Use and Care of Animals in Ophthalmic and Vision Research.

Abstract LB-344: MAP4K4 as a therapeutic target and novel biomarker for NSCLC

Abstract Introduction: Biomarker-guided personalized targeted therapies have improved lung cancer treatment; however, non-small cell lung cancer (NSCLC) targets such as KRAS — where activated mutations occur in ∼30% of cases — have so far eluded attempts at therapeutic targeting. There continues to be an urgent need to identify molecular mechanisms driving the disease and new targeted therapies. Mitogen-Activated Protein Kinase Kinase Kinase Kinase 4 (MAP4K4) overexpression promotes migration and invasion in several cancer types and correlates with poor prognosis in lung cancer. We investigated the role of MAP4K4 in NSCLC and tested whether MAP4K4 could serve as a biomarker on circulating tumor cells (CTCs) to monitor pre-metastatic and late stage disease. Methods: We used a novel class of highly selective small molecule inhibitor of MAP4K4, represented by SRI-28731, as a tool to further elucidate the role of MAP4K4 in NSCLC. We measured the expression of MAP4K4 and signaling changes following compound inhibition in lung cancer cell lines by immunoblotting and immunofluorescence. Clonogenic and wound healing assays were performed using our selective compound to assess proliferation and migration. To determine if MAP4K4 could be used as a biomarker in liquid biopsies we used FASTcell™, a non-enrichment optical scanning technology that enables identification and characterization of 1 tumor cell in 25 million blood cells. Results: We confirmed high expression of MAP4K4 in 4 out of 7 lung cancer cell lines, including A549 cells, and 3 of these harbored KRAS mutations. By clonogenic assay, A549 cell proliferation was inhibited by 51% and 99% with 2.5 nM and 5 nM of SRI-28731, respectively. In addition, lung cancer cell migration was impaired in the presence of 10 or 20 nM SRI-28731. Smad 1/5/8 phosphorylation was decreased in cells treated with the MAP4K4 inhibitor. Compound treated cells displayed a change in their actin cytoskeleton compared to DMSO treated cells. To explore whether MAP4K4 could be used as a biomarker on CTCs of metastatic NSCLC patients, we utilized the FASTcell™ platform and detected MAP4K4 expression on A549 cells mixed into normal blood. We are in the process of testing the assay with additional lung cancer cell lines and also testing MAP4K4 expression on CTCs from lung cancer patients. Conclusions: Our preliminary data suggest a role for MAP4K4 in proliferation, migration and signaling in lung cancer. Inhibition of MAP4K4 may be a valid therapeutic approach and the expression of MAP4K4 may serve as a biomarker in liquid biopsies. We showed that high levels of MAP4K4 in human lung cancer cell lines was concomitant to KRAS mutations, suggesting a possible correlation between the two markers. This novel biomarker could provide an opportunity to detect KRAS-positive cancers earlier and our new selective inhibitor could lead to life-saving, personalized treatment options for NSCLC cancer patients. Citation Format: Claire E. Repellin, Xiaohe Liu, Mary R. Stofega, Janey C.L. Snider, Zheng Ao, Ling Jong, Lidia C. Sambucetti. MAP4K4 as a therapeutic target and novel biomarker for NSCLC. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr LB-344.