Supplementary Material for: A Lentiviral CXCR4 Overexpression and Knockdown Model in Colorectal Cancer Cell Lines Reveals Plerixafor-Dependent Suppression of SDF-1α-Induced Migration and Invasion

<i>Background:</i> The development of distant metastasis is associated with poor outcome in patients with colorectal cancer (CRC). The stromal cell-derived factor-1 (SDF-1) and its receptor CXC chemokine receptor 4 (CXCR4) have pivotal roles in the chemotaxis of migrating tumor cells during metastasis. Thus, hampering the SDF-1/CXCR4 cross-talk is a promising strategy to suppress metastasis. <i>Methods:</i> We investigated the invasive behavior of the lentivirally CXCR4overexpressing CRC cell lines SW480, SW620 and RKO in chemotaxis and invasion assays toward an SDF-1α gradient. Low endogenous CXCR4 expression levels were determined by quantitative realtime polymerase chain reaction (PCR) and fluorescence-activated cell sorting (FACS) analyses. <i>Results:</i> A lentiviral CXCR4 overexpression and knockdown model was established in these CRC cells. In transwell migration assays, CXCR4 overexpression favored chemotaxis and invasion of cells in all 3 lines depending on an SDF-1α gradient (p < 0.001 vs. untransduced cells). Functional CXCR4 knockdown using lentiviral short hairpin RNA (shRNA) vectors significantly decreased the migration behavior in CRC cell lines (p < 0.001), confirming a CXCR4-specific effect. Pharmacologic inhibition of the SDF-1α/CXCR4 interaction by the bicyclam Plerixafor<sup>TM</sup> at 100 µM significantly abrogated CXCR4-dependent migration and invasion through Matrigel<sup>TM</sup> (SW480, SW620, RKO; p < 0.05). Conclusion: Our results indicate that a CXCR4-antagonistic therapy might prevent tumor cell dissemination and metastasis in CRC patients, consequently improving survival.