Infliximab therapy together with tyrosine kinase inhibition targets leukemic stem cells in chronic myeloid leukemia

Abstract

Background Expression of Bcr-Abl in hematopoietic stem cells is sufficient to cause chronic myeloid leukemia (CML) and tyrosine kinase inhibitors (TKI) induce molecular remission in the majority of CML patients. However, the disease driving stem cell population is not fully targeted by TKI therapy, and leukemic stem cells (LSC) capable of re-inducing the disease can persist. Single-cell RNA-sequencing technology recently identified an enriched inflammatory gene signature with TNFα and TGFβ being activated in TKI persisting quiescent LSC. Here, we studied the effects of human TNFα antibody infliximab (IFX), which has been shown to induce anti-inflammatory effects in mice, combined with TKI treatment on LSC function. Methods We first performed GSEA-pathway analysis using our microarray data of murine LSK cells (lin − ; Sca-1 + ; c-kit + ) from the SCLtTA/Bcr-Abl CML transgenic mouse model. Bcr-Abl positive cell lines were generated by retroviral transduction. Clonogenic potential was assessed by CFU (colony forming unit). CML mice were treated with nilotinib or nilotinib plus infliximab, and serial transplantation experiments were performed. Results Likewise to human CML, TNFα signaling was specifically active in murine CML stem cells, and ectopic expression of Bcr-Abl in murine and human progenitor cell lines induced TNFα expression. In vitro exposure to human (IFX) or murine (MP6-XT22) TNFα antibody reduced clonogenic growth of CML cells. Interestingly, TNFα antibody treatment enhanced TKI-induced effects on immature cells in vitro. Additionally, in transplant and serial transplant experiments, using our transgenic CML mouse model, we could subsequently show that IFX therapy boosted TKI-induced effects and further reduced the proportion of malignant stem cells in vivo. Conclusion TNFα signaling is induced in CML stem cells, and anti-inflammatory therapy enhances TKI-induced decline of LSC, confirming that successful targeting of persisting CML stem cells can be enhanced by addressing their malignant microenvironment simultaneously. Electronic supplementary material The online version of this article (10.1186/s12885-019-5871-2) contains supplementary material, which is available to authorized users.

Treatment-Free Remission in Chronic Myeloid Leukemia and New Approaches by Targeting Leukemia Stem Cells

“…TNF-a inhibitor combined with TKI induced significantly higher levels of apoptosis of LSCs compared to either treatment alone, as TNF-a inhibitor showed no off-target inhibition of BCR-ABL kinase activity (99). In another study, TNFa antibody infliximab combined with TKI impaired LSCs growth (100). Moreover, TNF-a signaling was found to mediate expansion and increased expression of CXCL1 in 6C3+ stromal progenitors, and higher expression CXCL1 signaling through CXCR2 enhanced growth capacity and self-renewal of LSCs.…”

The Bone Marrow Immune Microenvironment in CML: Treatment Responses, Treatment-Free Remission, and Therapeutic Vulnerabilities

“…Monoclonal antibody (mAb) targeting of TNF-α with infliximab enhanced the effect of TKIs against LSCs, although IFN-γ-modulating effects of infliximab may be contributing to the observed effects [43]. Alternatively, CXCR2 signalling in CML may function via mTOR and c-Myc [44], identifying other therapeutic possibilities.…”

Perspective: Pivotal translational hematology and therapeutic insights in chronic myeloid hematopoietic stem cell malignancies

“…43 Research is also assessing different TKIs being used sequentially or in combination with other drugs such as ruxoltinib or venetoclax (VEN), to target CML stem cells. [44][45][46] Additionally, activation of BTK has been shown to depend on the expression of the ITIM receptor Fc-γ receptor IIb (FcγRIIb, CD32b)…”

“…Indeed, a phase I trial incorporating natural killer (K‐NK003) cells for patients with CML and MRD after TKI therapy is currently ongoing 43 . Research is also assessing different TKIs being used sequentially or in combination with other drugs such as ruxoltinib or venetoclax (VEN), to target CML stem cells 44–46 . Additionally, activation of BTK has been shown to depend on the expression of the ITIM receptor Fc‐ γ receptor IIb (Fc γ RIIb, CD32b) and dual BCR‐ABL1/BTK‐targeting significantly enhanced apoptosis in TKI resistant non‐proliferating CML stem cells 47 (Figure 1).…”