Human fucosyltransferase 6 enables prostate cancer metastasis to bone

Department of Urology andPathology Laboratory Medicine, University of Rochester Medical Center, Rochester, NY 14642, USABackground: The interaction between human prostate cancer (PCa) cells and bone marrow (BM) endothelium follows a rolling-and-adhesion cascade mediated by E-selectin ligand (ESL): E-selectin. This adhesion is enabled by elevated expression of a-1,3-fucosyltransferases (FTs), enzymes responsible for ESL-mediated bone metastasis in humans. In contrast, the incidence of bonemetastasis in mice is rare.Methods: FT 3, 6 and 7 were overexpressed in mouse PCa cells. The rolling cell number, cell-rolling velocity and transendothelialmigration were characterised in vitro. Fucosyltransferases-transduced mouse PCa cells expressing luciferase were inoculated intomice via left ventricle to compare the capability of bone metastasis. Mass spectrometry and immunoprecipitation were utilised foridentification of ESLs.Results: Overexpression of FT3, FT6 or FT7 restored ESLs and enabled mouse PCa cells to roll and adhere in E-selectin-functionalised microtubes, similar to trafficking of circulating PCa cells in BM vessels. Following intracardiac inoculation,FT6-transduced cells induced robust bone metastasis in mice. Inhibition of FT6 by a fucose mimetic significantly reduced bonemetastasis. Importantly, comparison of FT3, FT6 and FT7 gene expression in existing clinical samples showed significantupregulation of FT6 in PCa-distant metastases.Conclusion: FT6 is a key mediator of PCa cells trafficking to the BM. It may serve as a viable drug target in preclinical tests oftherapeutics for reduction of PCa bone metastasis.Prostate cancer (PCa) is the leading cause of cancer death amongAmerican men, second only to lung cancer in 2012. When detectedat an early stage, the 5-year survival rate is close to 100%.In contrast, if diagnosed at a late stage with advanced metastaticdisease, the 5-year survival decreases to 33% (Siegel et al, 2012).The most common metastatic sites of PCa are lymph nodes, bones,lung and liver (Wilt and Ahmed, 2013). Among these sites, bone isthe most challenging organ for therapeutic intervention as bonemetastasis can cause severe skeleton-related diseases such as bonepain, hypercalcemia, fractures and nerve compression syndromes(Saad et al, 2006; Sturge et al, 2011).Metastasis to bone is a multistep cascade. Prostate cancercells detached from the primary site must first invade a bloodvessel, a process called intravasation. Through hematogenousdissemination, a sub-population of cells attach to bone marrow(BM) endothelial cells. This process is mediated by multiplereceptor–ligand interactions under shear stress, referred to as arolling-and-adhesion cascade (Li and King, 2012). This cascadefurther facilitates PCa cells to breach the bone endothelial layer(transendothelial migration; TEM) to establish micrometastases inthe bone microenvironment (Barthel et al, 2013).Bone marrow endothelial cells constitutively express E-selectin,which enables homing of hematopoietic stem cells expressingE-selectin ligands (ESLs) to the BM (Sackstein, 2012; Winkler et al,2012). Recent studies have indicated that human PCa cells alsoexpress similar ESLs to interact and traverse the vasculature of theBM (Dimitroff et al, 2004, 2005; Barthel et al, 2013). E-selectinligands comprise the tetrasaccharide sialyl Lewis X (sLe