Abstract
Changes in the levels of N-acetylglucosaminyltransferase V (GnT-V) can alter the function of several types of cell surface receptors and adhesion molecules by causing altered N-linked glycan branching. Using a her-2 mammary tumor mouse model, her-2 receptor signaling was down-regulated by GnT-V knock-out, resulting in a significant delay in the onset of her-2-induced mammary tumors. To identify the genes that contributed to this GnT-V regulation of early events in tumorigenesis, microarray analysis was performed using her-2 induced mammary tumors from wild-type and GnT-V-null mice. We found that 142 genes were aberrantly expressed (>2.0-fold) with 64 genes up-regulated and 78 genes down-regulated after deletion of GnT-V. Among differentially expressed genes, the expression of a subgroup of the cadherin superfamily, the protocadherin β (Pcdhβ) cluster, was up-regulated in GnT-V-null tumors. Altered expression of the Pcdhβ cluster in GnT-V-null tumors was not due to changes in promoter methylation; instead, impaired her-2-mediated signaling pathways were implicated at least in part resulting from reduced microRNA-21 expression. Overexpression of Pcdhβ genes inhibited tumor cell growth, decreased the proportion of tumor-initiating cells, and decreased tumor formation in vivo, demonstrating that expression of the Pcdhβ gene cluster can serve as an inhibitor of the transformed phenotype. Our results suggest the up-regulation of the Pcdhβ gene cluster as a mechanism for reduced her-2-mediated tumorigenesis resulting from GnT-V deletion.
Highlights
Her-2-induced mammary tumor onset is significantly delayed in GnT-V knock-out mice
We found that deletion of GnT-V caused enhanced gene expression of the Pcdh cluster in GnT-V knock-out tumors that contributes to the reduced her-2-induced tumorigenesis
Microarray Analysis of Her-2-induced Mammary Tumors— We recently demonstrated that deletion of GnT-V reduces the size of the compartment of tumor-initiating cells in a her-2
Summary
Results: The gene expression of the Pcdh cluster is up-regulated in her-2-induced tumors with GnT-V deletion. Her-2-induced mammary tumor onset is significantly delayed in GnT-V knock-out mice coincident with the reversion of her2-induced deregulation of acinar morphogenesis and a significantly reduced population of tumor-initiating cells (cancer stem cells) in isolated tumor cells with GnT-V deletion, resulting in reduced ability to form secondary tumors in NOD/SCID mice [9]. These results indicate that GnT-V promotes mammary tumor development by regulating some early events during tumorigenesis.
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