TNFa-induced alterations in stromal progenitors in CML BM result in enhanced LSC growth via CXCL1-CXCR2 signaling

Leukemia stem cells (LSC) are not eradicated in chronic myeloid leukemia (CML) patients responding to tyrosine kinase inhibitor treatment. Bone marrow (BM) mesenchymal niches play an essential role in hematopoietic stem cell (HSC) maintenance. Here, we examined leukemia-induced alterations in mesenchymal progenitor populations using a murine CML model. 6C3+ stroma-forming progenitors were increased in CML BM, and demonstrated enhanced LSC but reduced HSC support compared to their normal counterparts. CML 6C3 cells showed enhanced TNFa-related gene signatures, and upregulated CXCL1 expression. TNFa signaling contributed to expansion and increased CXCL1 expression by 6C3 cells in CML BM. The CXCL1 receptor CXCR2 was upregulated in in LSC, and CXCR2 inhibition significantly reduced LSC growth both in vitro and in vivo. In conclusion, TNFa-induced alterations in stromal progenitors in CML BM result in enhanced CML LSC growth via CXCL1-CXCR2 signaling. Targeting this axis represents a novel therapeutic strategy to inhibit BM niche-protected LSC. Overall design: Various esenchymal progenitors and long-term hematopoietic stem cells were sorted from the bone marrow of wild-type healthy adult (Normal) and SCL-tTA-BCR-ABL CML mice (CML) directly into RLT buffer and RNA prepared, with four biological replicates from each group.