Activity of the vascular-disrupting agent 5,6-dimethylxanthenone-4-acetic acid against human head and neck carcinoma xenografts

Head and neck squamous cell carcinomas (HNSCC) constitute a majority of the tumors of the upper aero-digestive tract and continue to present a significant therapeutic challenge. To explore the potential of vascular-targeted therapy in HNSCC, we investigated the antivascular, antitumor activity of the potent vascular-disrupting agent (VDA) 5,6-dimethylxanthenone-4- acetic acid (DMXAA) against two HNSCC xenografts with markedly different morphologic and vascular characteristics. Athymic nude mice bearing subcutaneous FaDu (human pharyngeal squamous cell carcinoma) and A253 (human submaxillary gland epidermoid carcinoma) tumors were administered a single dose of DMXAA (30 mg/kg, i.p). Changes in vascular function were evaluated 24 hours after treatment using contrast-enhanced magnetic resonance imaging (MRI) and immunohistochemistry (CD31). Signal enhancement ( E) and change in longitudinal relaxation rates (Delta R1) were calculated to measure alterations in vascular perfusion. MRI showed a 78% and 49% reduction in vascular perfusion in FaDu and A253 xenografts, respectively. CD31-immunostaining of tumor sections revealed three-fold (FaDu) and two-fold (A253) reductions in microvessel density (MVD) 24 hours after treatment. DMXAA was equally effective against both xenografts, with significant tumor growth inhibition observed 30 days after treatment. These results indicate that DMXAA may be beneficial in the management of HNSCC, alone or in combination with other treatments.