Interactions Between the Versican Ig Sequence and the Link Sequence in G1, and the EGF Sequence in G3 Modulate Adenoviral-Mediated Transgene Expression

Versican, a hyaluronan-binding proteoglycan, has been implicated in enhancing adenoviral-mediated transgene expression in cancer cells. These studies investigate the roles of versican’s N-terminal G1 and C-terminal G3 domains in modulating gene expression. CD44-positive Y79 or CD44-negative SK-N-DZ cells were transduced with an adenoviral vector containing a luciferase reporter gene in the presence of peptides derived from G1 (rVNβ, Ig-LD/L1, Ig-LD) or G3 (EGF-LD). Dose-response curves showed that rVNβ and Ig-LD/L1 peptides increased luciferase expression, peaking at 100nM and 300nM. The addition of hyaluronan further enhanced luciferase expression at 300nM in Y79 but not in SK-N-DZ cells. The Ig-LD peptide only enhanced expression at 150nM, with no further effect by hyaluronan. The EGF-LD peptide also increased luciferase expression, peaking at 10nM and 25nM. Co-incubation with Ig-LD decreased transgene expression. Immunocytochemistry demonstrated direct binding of peptides to the cells. Co-incubation of Ig-LD with other G1 or G3 peptides interfered with all binding. These data support a hypothesis that the Ig-LD domain binds a cellular receptor first, allowing the hyaluronan-binding L1 and L2 domains to subsequently bind and result in further hyaluronan-independent and dependent enhancement of adenoviral-mediated transgene expression. The binding of Ig-LD interferes with EGF-LD's binding and enhancement of transgene expression.