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.
|Publication status||Published - Jan 2012|
- Chronic Myeloid Leukaemia
- Quantitative Phosphoproteomics
- 8-plex iTRAQ