SDF-1/CXCR4 inhibition prevents paradoxical generation of cisplatin-induced pro-metastatic niches

Platinum-based chemotherapy remains widely used in advanced non-small cell lung cancer (NSCLC) despite its ineffectiveness in long-term control of metastasis. Here, we uncover the interconnected pathways subtending cisplatin-induced metastasis promotion. We report that cisplatin treatment of tumor-free mice results in bone-marrow expansion of CCR2+CXCR4+Ly6Chigh inflammatory monocytes (IM) concomitantly with increased levels in the lungs of stromal SDF-1, the CXCR4 ligand. In experimental metastasis assays, cisplatin-induced IM favor tumor cells extravasation and expansion of CD133+CXCR4+ metastasis initiating cells (MICs), facilitating lung metastasis formation. At the primary tumor, cisplatin reduces tumor size but induces tumor release of SDF-1 triggering MICs expansion and recruitment of pro-invasive CXCR4+ macrophages. Co-recruitment of MICs and CCR2+CXCR4+ IM at SDF-1-enriched distant sites also promotes spontaneous metastasis. Combination treatment with a CXCR4 inhibitor prevents cisplatin-induced IM/MICs recruitment and interaction thus precluding metastasis overgrowth. Finally, we observe in NSCLC patients’ specimens that SDF-1 levels are higher in platinum-treated samples and correlate with worse outcome. Our findings suggest a possible novel combination therapy based on CXCR4 blockade to control metastatic disease, paradoxically promoted by cisplatin.