HEMATOTHESIS

Oncogenic co-operation in T-cell acute lymphoblastic leukaemia: The role of TLX3 and TCF7::SPI1

SUMMARY

T-cell acute lymphoblastic leukaemia (T-ALL) is a devastating disease, which mainly occurs in childhood. Despite an improvement of the overall survival, the current treatments have many side effects, and patients with relapsed or refractory disease continue to have a very poor prognosis. T-ALL arises from T-cell progenitors that have acquired multiple genomic lesions, which co-operate to drive leukaemia development. For some genetic alterations, such as the TCF7::SPI1 fusion or ectopic expression of TLX3, their role in driving leukaemia remains largely unknown. Therefore, we first investigated the co-operation between TCF7::SPI1 and NRAS(G12D). Using a mouse model, we were able to show that β-catenin is a crucial coactivator for the oncogenic function of the TCF7::SPI1 fusion protein. In the second part, we demonstrated that TLX3 and FLT3-ITD co-operate in driving leukaemia by activating the SPI1/PU.¹ transcriptional program in an ex vivo pro-T-cell model and mouse model. This oncogenic function of TLX3 was shown to be dependent on other cofactors. Together, these two models of oncogenic co-operation in T-ALL demonstrate that the interaction between oncogenic transcription factors and cofactors is paramount for their function. Thus, these data provide a rationale for developing treatments directed at these protein interactions in the future for leukaemia.

(BELG J HEMATOL 2022;13(8):325–7)

Novel therapeutic targets in juvenile myelomonocytic leukaemia: Are noncoding RNAs valuable treatment options?

SUMMARY

Juvenile myelomonocytic leukaemia is a rare and aggressive clonal disease of early childhood for which hematopoietic stem cell transplantation remains the only curative option, albeit with a high relapse rate and many associated toxicities. Long non-coding RNAs (lncRNAs) and circular RNAs (circRNAs) have recently been implicated in a variety of biological processes, including haematopoiesis and receive much research attention as they possess features interesting for treatment, such as tissue specificity, low overall expression and easy targetability with RNAi or gene editing technology. Within this dissertation, we aimed at deciphering the lncRNA and circRNA transcriptome of JMML and use this knowledge to develop novel treatments.

(BELG J HEMATOL 2021;12(4):173-6)

Faster to the fungus: rapid diagnostic and prognostic tests for invasive fungal diseases

SUMMARY

Invasive mould infections such as invasive aspergillosis or mucormycosis remain an important infectious complication in haematology patients, especially in those undergoing intensive chemotherapy for acute myeloid leukaemia or undergoing allogeneic stem cell transplantation. An early diagnosis and timely initiation of antifungal therapy improves outcomes. In this thesis, we therefore looked at new possible diagnostic tools to aid in a rapid diagnosis, such as lateral flow assays, PCR tests, or a novel beta-D-glucan assay. Furthermore, we explored how we could get the maximum out of existing tests such as galactomannan, by optimising their use after therapy in an effort to assess the response to therapy.

(BELG J HEMATOL 2020;12(3):138-40)

Non-substitutive strategies to improve haemophilia care in developing countries: Experience in Côte d’Ivoire

SUMMARY

In developing countries, the high rate of haemophilia-related mortality and morbidity is mainly caused by a lack of knowledge, underdiagnoses and very limited access to treatment. This work carried out in Côte d’Ivoire as a part of the World Federation of Hemophilia twinning program, aimed to evaluate the impact of non-substitutive strategies (not based on concentrates of coagulation factors) on the management of haemophilia. This project sought at developing and validating education materials to improve knowledge on haemophilia, implementing a self-physiotherapy program, and obtaining cross-cultural and validated tools to assess the quality of life of people with haemophilia. These initiatives were the starting point for haemophilia care in Côte d’Ivoire, by providing patients with low-cost measures and creating an environment favourable for the use of substitutive treatment issued from humanitarian aid. This thesis was defended at UCLouvain on September 01, 2020. The full manuscript of this these is available on dial.uclouvain.be.

(BELG J HEMATOL 2020;12(2):90-2)

A multicentric observational study on the management of hyperleukocytic acute myeloid leukaemia in Belgium

SUMMARY

INTRODUCTION

In hyperleukocytic acute myeloid leukaemia (AML) the risk of leukostasis is high due to the rapid increase in WBC count and the size of the myeloid blasts. It is associated with poor prognosis due to an increased risk of early death and relapse. Immediate initiation of cytoreductive treatment is essential to improve outcome, but evidence to prefer hydroxyurea, leukapheresis, intensive chemotherapy (IC) or a combination treatment, is lacking. Therefore, we decided to investigate the current approach of hyperleukocytic AML in Belgium.

METHODS

A brief questionnaire on the management of hyperleukocytic AML was sent to all Belgian centres currently treating AML with IC and was replied by ten centres. Four centres agreed to a more detailed retrospective analysis. All newly diagnosed AML patients presenting with hyperleukocytosis between January 2013 and April 2019 were included. Patient and disease characteristics were collected, as well as treatment choice and outcome parameters.

RESULTS

We included 121 patients with a median WBC count of 116,360/µL. Mortality at day 21 was 20% and overall mortality was 64% at a median follow-up of six months. Twenty percent received leukapheresis, which was started within 24 hours. There was no difference in age distribution, treatment intensity or time to start IC between patients receiving leukapheresis or not. Although the leukapheresis group had a more severe presentation with a higher median WBC and blast count and a worse performance status, there was no difference in response to therapy, early or long-term mortality. In a multivariate analysis, age at diagnosis and treatment modality (IC vs non-IC) were the only independent parameters that significantly affected early death.

CONCLUSION

Evidence on optimal treatment options in hyperleukocytic AML is lacking. We could not demonstrate any added value of leukapheresis. To improve the prognosis of this dramatic presentation, national or even European databases should be used to document and learn from the outcome of current practice.

(BELG J HEMATOL 2020;11(7):325-34)

In search of novel working mechanisms of proteasome inhibitors in multiple myeloma

SUMMARY

Proteasome inhibitors (PIs) constitute one of the cornerstones of the treatment of multiple myeloma (MM), with bortezomib, carfilzomib and ixazomib being approved for clinical use. Due to the relatively recent introduction of PIs to clinical practice, many aspects of the pleiotropic effects of PIs still remain unexplored, particularly for the second-generation PIs carfilzomib and ixazomib. Since MM still remains incurable and many patients will eventually develop treatment-refractory disease, the search for validated biomarkers to predict treatment response is of great clinical importance. In the first aim of this project, we evaluated the effect of proteasome inhibitors on erythropoiesis. During the follow-up of MM patients treated with PIs in the first part of this project, we observed a consistent and highly significant increase in the reticulocyte count during treatment with carfilzomib-based regimens in patients with relapsed multiple myeloma. This observation was not made in a matched cohort of bortezomib-treated patients. In subsequent ex vivo experiments, we demonstrated that carfilzomib exposure significantly impaired terminal erythroid maturation, independent of erythroid commitment, expansion or differentiation. Our results therefore report the first pharmacologically induced delay in erythroid maturation as a mechanism for carfilzomib-induced reticulocytosis in patients with multiple myeloma. These findings might therefore lead to new therapeutic applications for carfilzomib in disorders of mature erythrocytes, such as sickle cell anaemia. In the second part of this project, we evaluated proteasome activity as a potential biomarker for PI drug sensitivity. For this purpose, we measured proteasome activity in primary myeloma cells, purified from the bone marrow of patients with MM. Baseline proteasome activity was not significantly different in myeloma cells derived from treatment-responsive or –refractory MM patients. The degree of proteasome inhibition by PIs was similar in both groups. As a result, the clinical applicability of proteasome activity as a biomarker for drug sensitivity in MM currently remains limited. Nevertheless, these data also suggest that drug sensitivity to PIs is in part proteasome-independent, indicating that our understanding of PI drug resistance should be further improved. In a follow-up project to the present thesis, we have designed several genome-wide screening experiments using CRISPR-Cas9 technology to gain novel insights in the mechanisms driving drug resistance to PIs in MM.

(BELG J HEMATOL 2020;11(3):133–5)

Erythropoiesis and iron metabolism after haematopoietic stem cell transplantation

After haematopoietic stem cell transplantation (HCT), many patients present anaemia, which can persist for months due to an inadequate erythropoietin production for the degree of the anaemia. In this thesis, we performed two randomised studies with erythropoiesis-stimulating agents therapy after allogeneic (including myeloablative and non-myeloablative conditioning) and autologous transplantation. We showed a great efficacy of this growth factor to ensure full erythroid reconstitution when initiated soon after engraftment and not immediately after the transplant. Furthermore, as iron parameters are quite disturbed following HCT, we sought to study iron metabolism after HCT (which has not been much investigated), integrating the role of hepcidin, the key regulator in iron metabolism. Hence, we demonstrated that hepcidin levels prior to and following autologous HCT were influenced by iron stores and changes in erythropoietic activity.

(BELG J HEMATOL 2019;10(2):89–95)