G-CSF and its receptor in myeloid malignancy

Abstract

Granulocyte colony-stimulating factor (G-CSF) has been used in the clinic for more than 2 decades to treat congenital and acquired neutropenias and to reduce febrile neutropenia before or during courses of intensive cytoreductive therapy. In addition, healthy stem cell donors receive short-term treatment with G-CSF for mobilization of hematopoietic stem cells. G-CSF has also been applied in priming strategies designed to enhance the sensitivity of leukemia stem cells to cytotoxic agents, in protocols aimed to induce their differentiation and accompanying growth arrest and cell death, and in severe aplastic anemia and myelodysplastic syndrome (MDS) to alleviate anemia. The potential adverse effects of G-CSF administration, particularly the risk of malignant transformation, have fueled ongoing debates, some of which can only be settled in follow-up studies extending over several decades. This specifically applies to children with severe congenital neutropenia who receive lifelong treatment with G-CSF and in which the high susceptibility to develop MDS and acute myeloid leukemia (AML) has now become a major clinical concern. Here, we will highlight some of the controversies and chal- G-CSF and its receptorThe growth factor granulocyte colony-stimulating factor (G-CSF), now referred to as CSF3, is the major regulator of neutrophil production under basal conditions of hematopoiesis, as is evident from the fact that CSF3 or CSF3 receptor-deficient mice are severely neutropenic. 1,2 CSF3 is also essential for "emergency" granulopoiesis in response to bacterial infections and enhances multiple neutrophil functions. 3 CSF3 exerts its role by inducing proliferation and survival of myeloid progenitor cells, followed by a cell-cycle arrest and neutrophilic differentiation. 4 The receptor for CSF3 (CSF3R) belongs to the cytokine receptor type I superfamily, which engages the canonical Janus kinase (Jak)/signal transducer and activator of transcription (STAT), Ras/Raf/MAP kinase, and PKB/Akt pathways. When CSF3R mutants were expressed in differentiation competent factor-dependent myeloid cell lines, the distal cytoplasmic region of the CSF3R of approximately 100 amino acids was crucial for CSF3-induced neutrophilic differentiation of these cells. 5 Although originally being considered as "differentiation domain," later studies demonstrated that this C-terminal region exerts a negative role in STAT5 activation and proliferation signaling in vivo. 6,7 Negative regulators of CSF3 signaling linked to the distal C-terminus of CSF3R include the protein tyrosine phosphatases SHP-1 and the suppressor of cytokine signaling (SOCS) protein SOCS3. The SOCS protein family is characterized by a so-called SOCS box, a domain involved in the recruitment of ubiquitin (E3) ligase activity. The negative action of SOCS3 and more specifically of its SOCS box on CSF3 signaling has been demonstrated in conditional knockout models. 8,9 A mechanism for receptor down-regulation has been proposed in which SOCS3 drives ubiquitination of a conserved ju...

Therapy-related myeloid neoplasms following fludarabine, cyclophosphamide, and rituximab (FCR) treatment in patients with chronic lymphocytic leukemia/small lymphocytic lymphoma

“…Prolonged growth factor treatment has been shown to facilitate selection of neoplastic clone and have a role in the development of myelodysplastic syndrome or acute myeloid leukemia. 18,19,21 In this study, we confirmed that therapy-related myeloid neoplasms after FCR therapy have morphological characteristics and cytogenetic abnormalities similar to therapy-related myeloid neoplasms caused by typical alkylating agents, evidenced by a more frequent therapy-related myelodysplastic syndrome rather than by therapy-related acute myeloid leukemia presentation, and frequent unbalanced loss of chromosome 5 and/or 7, or a complex karyotype. However, therapy-related myeloid neoplasms associated with FCR have a shorter latency interval, with median 35 months in our series, as compared with 5-7 years generally known for therapy-related myeloid neoplasms secondary to typical alkylating agents.…”

Chronic neutrophilic leukemia 2016: Update on diagnosis, molecular genetics, prognosis, and management

“…Over the last few years, exponential progress in understanding the molecular basis of CNL has been made, with the discovery of likely disease-defining mutations in CSF3R, the gene for receptor for colony-stimulating factor 3(CSF3), the primary growth factor of neutrophil production [9]. A landmark publication by Maxson et al ushered in a new vision regarding the pathogenesis of CNL [1].…”

“…An unexpectedly high frequency of mutations in the CSF3R were found in 59% (16 of 27) patients with CNL and aCML, compared to only 1% of patients with AML (n 5 292). Two types of mutations were found; most were in the membrane proximal region which mediates proliferative and survival signals: CSF3R T618I (n 5 12) and CSF3R T615A (n 5 2) [1,9,10]. These occurred alone or in association with nonsense mutations that truncate cytoplasmic tail (a region important in transduction of maturation and suppression of proliferation) [1,9,10].…”

Use of G-CSF to hasten neutrophil recovery after auto-SCT for AML is not associated with increased relapse incidence: a report from the Acute Leukemia Working Party of the EBMT

“…23 It was previously shown that AML cell lines and AML patient samples express increased relative amounts of the class IV isoform G-CSF receptor. 24,25 These data suggest that despite the lack of evidence for an increased risk of relapse associated with G-CSF administration in general, there may be particular AML patient subsets susceptible to this effect. In our study, the number of cases with standard-risk AML was relatively small, so we were able to analyze it separately only in the PB-auto-SCT group.…”