VLA-4 phosphorylation during tumor and immune cell migration relies on its coupling to VEGFR2 and CXCR4 by syndecan-1

Area of Science:

• Molecular Biology
• Cancer Research
• Cellular Signaling

Background:

• Tumor-promoting enzyme heparanase cleaves syndecan-1 (Sdc1), linking VEGFR2 to VLA-4 and promoting myeloma cell migration.
• The precise mechanism by which VEGFR2 activates VLA-4-mediated cell motility remained unclear.

Purpose of the Study:

• To elucidate the molecular mechanism by which VEGFR2 activates VLA-4-mediated tumor cell migration.
• To identify key signaling molecules involved in VLA-4 phosphorylation and activation.

Main Methods:

• Investigated the role of protein kinase A (PKA) in VLA-4 phosphorylation at S988.
• Utilized a syndecan-mimetic peptide (SSTN_VEGFR2) to block VEGFR2-VLA-4 interactions.
• Examined the involvement of chemokine receptor CXCR4, AC7 (adenylate cyclase 7), and PKA in the signaling pathway.

Main Results:

• VEGFR2 phosphorylates VLA-4 at S988 via PKA, enhancing tumor metastasis and suppressing cytotoxic immune cells.
• CXCR4, AC7, and PKA form a complex with VEGFR2, localized to VLA-4 by Sdc1.
• VEGFR2 phosphorylates CXCR4 at Y135, activating the signaling cascade leading to VLA-4 phosphorylation.
• SSTN_VEGFR2 peptide blocks this mechanism, inhibiting tumor cell migration and promoting leukocyte migration.

Conclusions:

• Discovered a novel signaling pathway where VEGFR2, CXCR4, AC7, and PKA cooperate to phosphorylate VLA-4, driving tumor cell migration and metastasis.
• Targeting this pathway with syndecan-mimetic peptides offers a potential therapeutic strategy to inhibit cancer progression and enhance anti-tumor immunity.