Introduction: Mesenchymal stem cells (mMSCs) migrate to, and preferentially integrate into growing tumors providing stroma, and potentially serving as delivery vehicles for apoptosis inducing molecules. The present study was performed to investigate the role of FGF2 and VEGF in the migration of mMSCs toward melanoma, and breast cancer.
Methods: To evaluate the chemotactic effect of melanoma on mMSCs, 25 x 103 mMSCs were suspended in low melting agar and cocultured adjacent to either acellular agar droplets (control) or agar droplets containing 25 x 103 B16 melanoma cells. Migration of mMSCs was quantitated after 24 hours. Serum free media (Group I), Sarkar breast cancer conditioned media (Grp II), serum free media plus FGF2 (Grp III), serum free media + VEGF (Grp IV) serum free media+FGF2+VEGF (Grp V), FGF2 depleted Sarkar conditioned media (Grp VI), VEGF depleted Sarkar conditioned medium, (Grp VII), and VEGF and FGF2 depleted Sarkar conditioned medium, (Grp VIII) were placed in target wells, and 25x103 mMSCs were placed in the upper wells of modified Boyden chambers. Migration was quantitated after 24 hours of incubation. RT-PCR and Western blot analysis were performed on appropriate specimens.
Results: 73.7% +/- 14% of mMSCs cocultured with B16 migrated, as compared with 1.1% for the control. Percent migration by transwell assay Grp I: 1.1%, +/- 0.50, Grp II: 23.9%, +/- 0.56, Grp III: 14.3%, +/- 13, GrpIV: 11.1%, +/- 11, Grp V: 11.9%, +/- 12, Grp VI: 13.3%, +/-7.3, GrpVII: 15.5 +/- 1.1, Grp VIII: 10.3 +/- 1.2 (N=6, +/- SD). RT-PCR demonstrated VEGFR, FGFR1, and FGFR4 on mMSCs. Western blot analysis demonstrated the presence of FGF2 and VEGF in the conditioned media. Identification of mMSC was performed using anti-CD11b, and anti-Sca-1 monoclonal antibodies.
Conclusion: Tumor cells secrete FGF2, and VEGF. mMSCs express receptors for VEGF and FGF2. VEGF and FGF2 enriched media induce migration. Antibody depletion of VEGF and FGF2 of tumor conditioned media reduces its migratory effect. VEGF, and FGF2, play key roles in the migration of mMSCs to cancer cells.