Introduction: Chronic myeloid leukaemia is a blood cancer which progresses from a chronic phase to an acute blast crisis if untreated. Disease progression and treatment resistance may be precipitated by the mutator action of BCR/ABL protein tyrosine kinase (PTK), but only few protein phosphosites involved in the DNA damage response have been investigated with respect to BCR/ABL action. Aim: The aim of this PhD project was to demonstrate that BCR/ABL PTK expression can affect the response to genotoxic stress signalling at the protein phosphorylation level. Methodology: Etoposide-induced DNA damage response has been studied in control and BCR/ABL PTK-expressing Ba/F3 cells using apoptosis and γH2AX assays. Quantitative phosphoproteomics was performed with iTRAQ peptide labelling to discover putative modulated phosphorylation sites. Absolute quantification (AQUA ) performed with selected reaction monitoring was used to validate discovery phosphoproteomics. The effect of genotoxic stress on the THO complex protein Thoc5/Fmip was studied using western blots. Results: The expression of BCR/ABL PTK induced γH2AX phosphorylation after etoposide exposure. This was associated with the modulation of H2AX tyrosine 142 phosphorylation, MDC1 (serines 595 and 1053) and Hemogen serine 380 phosphorylation among proteins regulated by both BCR/ABL PTK and etoposide. We identified that leukaemogenic PTKs mediate Thoc5/Fmip phosphorylation on tyrosine 225 via Src proto-oncogene and oxidative stress, while ATM and MEK1/2 may control its phosphorylation. Human CD34+ CD38- leukaemic stem cells showed pronounced level of THOC5/FMIP tyrosine phosphorylation. Expression of phosphomutant Thoc5/Fmip Y225F might reduce apoptosis mediated by etoposide and H2O2. Conclusion: BCR/ABL PTK can sustain, create, block and change the intensity of protein phosphorylation related to genotoxic stress. Modulation of H2AX, MDC1, Hemogen and Thoc5/Fmip post-translational modifications by BCR/ABL PTK might promote unfaithful DNA repair, genomic instability, anti-apoptotic signalling or abnormal cell differentiation, resulting in leukaemia progression.

Chronic myeloid leukaemia (CML) is characterised by the constitutively active tyrosine kinase BCR-ABL. Standard treatment with tyrosine kinase inhibitors (TKI) in the chronic phase (CP) of CML conveys excellent long-term prognosis but is associated with side effects and costs. Treatment free remission (TFR) is possible in a proportion of patients discontinuing treatment after obtaining deep treatment responses but it is not fully known how to select the right patients for stopping attempts. Treatment of accelerated phase (AP) and blast crisis (BC) is more complicated and the prognosis more dismal. In this thesis, we have studied factors of importance for outcome in CML patients with focus on immunological factors and clinical management. In a cohort of 32 newly diagnosed CP-CML patients, evidence of active immune escape mechanisms were found. These declined with the course of TKI treatment and at the same time, effector lymphocyte responses were elicited. These anti-leukaemia immune responses might help in the long-term control of CML. Multiple plasma protein markers were also measured with three multiplex platforms in a smaller cohort of patients (n=14). Inflammatory cytokines and other plasma proteins were affected by TKI treatment and multiplexing seems useful for finding potential biomarkers with biologic or prognostic significance in CML. Patients progressing to AP/BC were studied in a population-based material from the Swedish CML register. Approximately 4% of TKI-treated CP-CML patients transformed to AP/BC within 2 years of diagnosis. Monitoring of treatment responses was suboptimal in 1/3 of these patients and the median survival was 1.4 years after diagnosis of AP/BC. Thus, minimising the risk of disease progression through strict adherence to guidelines for monitoring and treatment is essential. In a cohort of patients (n=50) discontinuing TKI treatment within a large European trial, musculoskeletal pain was reported by 30% of patients, starting within 1- 6 weeks of TKI discontinuation and spontaneously resolving over time in most cases. Patients (n=56) were also evaluated with a multiplex platform with a total of 162 inflammation- and cancer-related plasma proteins. No predictive protein biomarkers for successful TKI discontinuation could be found. However, profound effects of TKI-treatment were seen and plasma proteomics could be useful for understanding effects of long-term TKI-treatment.

Wir berichten über einen 48-jährigen multimorbiden Patienten, der vor 26 Jahren eine allogene Knochenmarktransplantation aufgrund einer chronischen myeloischen Leukämie erhielt; 24 Jahre lang litt der Patient an einer sklerodermiformen chronischen Graft-versus-Host-Disease (GVHD) der Haut und der Lunge mit partieller Lungenresektion und immunsuppressiver Therapie. An den Unterschenkeln entwickelten sich rezidivierende Ulzerationen an den von der kutanen GVHD betroffenen Stellen. Der Patient stellte sich mit einem größenprogredienten Ulkus mit Therapieresistenz in unserer Klinik vor. Histologisch konnte ein Plattenepithelkarzinom diagnostiziert werden. Die Magnetresonanztomographie zeigte eine Knochenbeteiligung und eine kutane In-Transit-Metastase, und die Computertomographie ergab eine Metastase im Os sacrum. Bevor die Therapie eingeleitet wurde, verstarb der Patient plötzlich an den Folgen seiner Vorerkrankungen. Die Entwicklung einer kutanen GVHD ist häufig bei Patienten mit allogener Stammzelltransplantation. Hierbei ist das Risiko für die Entwicklung von Plattenepithelkarzinomen erhöht. Patienten sollten unter engmaschiger dermatologischer Kontrolle stehen. Bei Verdacht auf ein Plattenepithelkarzinom bei vorbestehender GVHD sollte zeitnah eine bioptische Sicherung erfolgen, um das Risiko einer Metastasierung zu senken.

Introduction: Discontinuation of tyrosine kinase inhibitor (TKI) treatment is emerging as the main therapy goal for Chronic Myeloid Leukemia (CML) patients. The DESTINY trial showed that TKI dose reduction prior to cessation can lead to an increased number of patients achieving sustained treatment free remission (TFR). However, there has been no systematic investigation to evaluate how dose reduction regimens can further improve the success of TKI stop trials. Methods: Here, we apply an established mathematical model of CML therapy to investigate different TKI dose reduction schemes prior to therapy cessation and evaluate them with respect to the total amount of drug used and the expected TFR success. Results: Our systematic analysis confirms clinical findings that the overall time of TKI treatment is a major determinant of TFR success, while highlighting that lower dose TKI treatment for the same duration is equally sufficient for many patients. Our results further suggest that a stepwise dose reduction prior to TKI cessation can increase the success rate of TFR, while substantially reducing the amount of administered TKI. Discussion: Our findings illustrate the potential of dose reduction schemes prior to treatment cessation and suggest corresponding and clinically testable strategies that are applicable to many CML patients.