Malignant melanoma typically metastasizes to lymph nodes (LNs) as a primary or in-transit lesion before<br>secondary metastasis occurs, and LN biopsy is a common procedure to diagnose melanoma progression.<br>Since cancer metastasis is a complex process where various interactions between tumor cells and the<br>stroma play key roles in establishing metastatic lesions, the exact mechanisms underlying melanoma<br>metastasis to LNs remains unknown. It has been known that focal adhesion kinase (FAK) activity promotes<br>the expression of proinflammatory vascular cell adhesion molecule-1 (VCAM-1). As VCAM-1 is a<br>major receptor for a4 integrin and plays a key role in leukocyte recruitment, we reasoned that inhibition<br>of FAK activity may reduce VCAM-1 expression within LNs and thus reduce metastasis of a4 integrinexpressing<br>melanoma to LNs. First, we found that a pharmacological FAK inhibitor, PF-271, blocked tumor<br>necrosis factor-a (TNF-a)-mediated VCAM-1 expression on human dermal lymphatic endothelial<br>cells (HDLECs). In vitro, PF-271 significantly decreased B16F10 melanoma adhesion to and transmigration<br>through HDLECs compared to TNF-a treated cells. Furthermore, in vivo FAK inhibition by oral PF-271<br>administration reduced VCAM-1 expression in inguinal, cervical, and popliteal LNs compared to<br>vehicle treated mice. Finally, in a footpad metastasis model, B16F10 melanoma cells were injected into<br>the right footpad of C57BL/6 mice, and PF-271 (50 mg/kg, twice daily for 6 days) was orally administrated<br>after 1 week of tumor transplantation. While untreated mice exhibited significant metastatic melanoma<br>lesions in popliteal LNs, PF-271 treated mice showed only marginal melanoma metastasis. These results<br>support the possibility that FAK inhibitors may be a novel preventative option in melanoma metastasis<br>by blocking VCAM-1 expression in LNs.