Biological characterization of Philadelphia chromosome-positive acute lymphoblastic leukemia

Helena Hohtari

Forskningsoutput: AvhandlingDoktorsavhandlingSamling av artiklar

Sammanfattning

The prognosis of Philadelphia chromosome-positive (Ph+) acute lymphoblastic leukemia (ALL) has significantly improved with the introduction of tyrosine kinase inhibitors (TKIs). As the incidence of Ph-positivity increases with age, a substantial number of elderly Ph+ ALL patients are ineligible for intensive treatment modalities. Currently, a proportion of patients experience prolonged survival with TKI-based therapies only, and many succumb eventually to non leukemia-related causes. The aim of this thesis was to identify potential predictive biomarkers for more personalized risk stratification in Ph+ ALL, including characterization of the immune microenvironment in ALL bone marrow (BM). We also wanted to assess the drug sensitivity of primary patient samples to identify potential novel or repurposed drugs, with especially non-fit patients in mind, and to study the prevalence of copy number alterations and other secondary mutations. In study I, we collected archived formalin-fixed and paraffin-embedded BM biopsies from Ph+ (n = 31) and Philadelphia chromosome-negative (Ph−; n = 21) ALL patients and non-leukemic controls (n = 14). The samples were constructed to tissue microarrays and analyzed with multiplex immunohistochemistry and automated image analysis. The immune contexture of Ph+ and Ph− ALL BM did not differ significantly. Instead, ALL BM was characterized by an increased amount of immune cells associated with immunosuppression when compared to healthy controls. Further, the higher proportion of CD4+PD1+TIM3+ T cells, older age, and lower platelet count at diagnosis segregated a group with poor survival. In study II, we analyzed the drug sensitivity of 18 primary B-ALL BM samples (Ph+ n=10, Ph− n=8) to a selection of 64 drugs by using a well-established drug sensitivity and resistance testing assay. The results were combined with whole transcriptome sequencing and publicly available gene expression data. Apoptosis-modulating BCL2 inhibitors and MDM2 inhibitors were widely effective. BCL2-selective venetoclax was more effective in Ph− samples, whereas BCL2, BCL-W, and BCL-XL targeting navitoclax showed uniform potency. BCL2 expression was significantly higher in Ph− ALL, whereas BCL-W and BCL-XL were overexpressed in Ph+ ALL, explaining the differential drug responses. In addition, the sequencing strategies recognized three previously undiagnosed Ph-like patients with a sensitivity to TKIs. In study III, we investigated the frequency and significance of copy number alterations (CNAs) and other secondary mutations in Ph+ ALL by applying targeted next-generation sequencing (NGS) gene panel and multiplex ligation-dependent probe amplification to diagnostic (n=40) and relapse-phase (n=11) BM samples. We also assessed the prevalence of subclonal T315I kinase domain mutations. The results were combined with clinical registry data. Deletions of IKZF1 together with deletions in CDKN2A/B and/or PAX5 were common, and they stratified a group with dismal outcome. Other secondary mutations at diagnosis were rare. In conclusion, this thesis shows Ph+ ALL BM immune contexture did not differ from Ph− ALL. Instead, ALL BM immune microenvironment differs from healthy controls, and immune profiling can serve as a tool in identifying novel prognostic biomarkers. Copy number alterations (CNA) defined a subset in Ph+ ALL with dismal outcome, and we recommend incorporating CNA analysis to routine diagnostic procedures. In addition, with ex vivo drug testing, we identified several potential compounds to be further tested in clinical trials.
Originalspråkengelska
Handledare
  • Porkka, Kimmo, Handledare
  • Mustjoki, Satu, Handledare
UtgivningsortHelsinki
Förlag
Tryckta ISBN978-951-51-9030-7
Elektroniska ISBN978-951-51-9031-4
StatusPublicerad - 2023
MoE-publikationstypG5 Doktorsavhandling (artikel)

Bibliografisk information

M1 - 104 s. + liitteet

Vetenskapsgrenar

  • 3122 Cancersjukdomar

Citera det här