Abstract 2890: A novel interaction between 12-lipoxygenase and integrin subunit Beta4 plays a role in tumor migration, invasion and metastasis
Authors: Joshi Sangeeta , Tang Keqin , Cai Yinlong , Guo Yande , Dilly Ashok Kumar , Tucker Stephanie , Honn Kenneth V. 
Published: June 2012

Abstract
This study has the potential to establish a new paradigm in adhesion-mediated control of eicosanoid production and could be relevant to tumor migration, invasion, and metastasis. 12-Lipoxygenase metabolizes arachidonic acid to form 12(S)-HETE, a metabolite known to play a significant role in the process of tumor-induced angiogenesis and metastasis. The role of 12-LOX in proliferation, survival, and motility of tumor cells as well as in angiogenesis has been described for a variety of cancers. Similarly Alpha6Beta4 integrin also plays a role in both angiogenesis and tumorigenesis in addition to having a role in the formation of hemidesmosomes (HD). Evidence suggests a correlation between 12-LOX and integrin Beta4 since they play a similar role in cancer progression. The physical interaction between 12-LOX and Beta4 was first identified by a yeast two-hybrid screen using 12-LOX as bait against a library made from A431 cells that are known to have endogenous expression of both proteins. We verified this interaction by co-immunoprecipitation from A431 cells, and recapitulated it in CHO and PC-3 cells ectopically expressing 12-LOX and the cytoplasmic tail of Beta4 integrin. Additionally our data shows that ligation or clustering of Alpha6Beta4 integrin by the natural ligand laminin or an antibody mimic of laminin, 3E1, caused an increase in translocation of 12-LOX from the cytosol to membrane and an increase in 12-LOX enzymatic activities as assayed by immunofluorescence and 12(S)-HETE measurements respectively. 3E1-stimulated A431 cells showed increased cell migration but there was 40% decrease in presence of 12-LOX inhibitor BMD122 which confirms the role of 12-LOX in cell invasion. Here we describe for the first time the interaction domains that unite Beta4 integrin and 12-LOX. We mapped the domains in the cytoplasmic tail of Beta4 critical for interacting with 12-LOX and found that the 1126-1157 domain in the cytoplasmic tail of Beta4 is important for binding of 12-LOX. Also we have shown the mutant fragment (1126-1315) interacts with 12-lipoxygenase in the cytosol and prevent its binding to native, full-length membrane-associated Beta4 and thereby prevents 12-LOX activation. This physical interaction has functional implications with regard to decreased cell survival and migration. Determination of the structural basis for protein-protein interaction may provide potential means to manipulate or block such interaction, which may yield therapeutic benefits. We propose that the results obtained from these studies will provide a novel, and important dimension to both integrin and eicosanoid biology.
Acknowledgements: This project is supported by NIH: NCI, 2 R01 CA029997-17A1
Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 2890. doi:10.1158/1538-7445.AM2011-2890