Inflammatory Activation of Astrocytes Facilitates Melanoma Brain Tropism via the CXCL10-CXCR3 Signaling Axis

Summary: Melanoma is the deadliest skin cancer due to its high rate of metastasis, frequently to the brain. Brain metastases are incurable; therefore, understanding melanoma brain metastasis is of great clinical importance. We used a mouse model of spontaneous melanoma brain metastasis to study the interactions of melanomas with the brain microenvironment. We find that CXCL10 is upregulated in metastasis-associated astrocytes in mice and humans and is functionally important for the chemoattraction of melanoma cells. Moreover, CXCR3, the receptor for CXCL10, is upregulated in brain-tropic melanoma cells. Targeting melanoma expression of CXCR3 by nanoparticle-mediated siRNA delivery or by shRNA transduction inhibits melanoma cell migration and attenuates brain metastasis in vivo. These findings suggest that the instigation of pro-inflammatory signaling in astrocytes is hijacked by brain-metastasizing tumor cells to promote their metastatic capacity and that the CXCL10-CXCR3 axis may be a potential therapeutic target for the prevention of melanoma brain metastasis. : Melanoma brain metastases are incurable. Doron et al. find that astrocyte-secreted CXCL10 is functional in melanoma chemoattraction to the brain. CXCR3, the CXCL10 receptor, is upregulated in brain-seeking melanoma cells. Silencing CXCR3 expression attenuates brain metastasis, suggesting that the CXCL10-CXCR3 axis may be a therapeutic target for melanoma brain metastasis. Keywords: melanoma, brain metastasis, astrocytes, CXCL10, CXCR3, brain tropis