SCIENTIFIC PROGRAMME
SESSION I
BIOLOGY OF B-CELL
PRECURSOR ALL
SESSION II
BIOLOGY OF T-CELL ALL
SESSION III
MINIMAL RESIDUAL
DISEASE MONITORING
SESSION IV
INDIVIDUALIZED
MANAGEMENT OF ALL
SESSION V
NEW ADVANCES IN ALL
SESSION VI
CAR T-CELLS &
ALLOGENEIC HSCT
SESSION VII
FRONTLINE
INCORPORATION OF
BITES AND ADCS
SESSION VIII
T-CELL ALL AND
LYMPHOBLASTIC
LYMPHOMA
SESSION IX
PH AND PH-LIKE ALL
SELECTED ABSTRACTS
FOR AN ORAL
PRESENTATION
SELECTED ABSTRACTS
AS E-POSTERS
DISCLOSURES
CO-TARGETING BCL-2- AND PI3K/AKT-PATHWAYS REVEALS SYNERGISTIC EFFECTS
IN ACUTE B-LYMPHOBLASTIC LEUKEMIA CELLS
Anna Richter, Clemens Holz, Anett Sekora, Sandra Lange and Christian Junghanss
Department of Medicine, Clinic III – Hematology, Oncology, Palliative Medicine, Rostock University
Medical Center, Rostock, Germany
Introduction: Dysregulated cell proliferation and prevention of apoptosis are fundamental
principles of cancer pathogenesis frequently represented by aberrant PI3K/AKT and BCL-2
signaling in hematological neoplasms. Based on biological functions and recent data which
indicates interactions between both pathways co-targeting appears rational. We therefore
characterized the effects of previously untested combinatorial approaches involving the BCL-2
inhibitor venetoclax and various PI3K/AKT pathway inhibitors in acute B-lymphoblastic
leukemia (B-ALL) cells.
Methods: B-ALL cell lines (SEM, RS4;11) were incubated with PI3K inhibitors (idelalisib,
buparlisib) or AKT inhibitors (MK-2206, perifosine) alone and in combination with venetoclax
for up to 72 h. Investigation of potential cytotoxicity in healthy cells were conducted using
hemolysis and Calcein-AM assays. Effects on metabolic activity, proliferation and apoptosis
were evaluated using WST-1 assay, trypan blue and annexin V-FITC/PI staining, respectively.
Detailed investigation of functional BCL-2 pathway-mediated apoptosis induction was
determined by Bax translocation assay. Immunofluorescent co-staining of Bax and
mitochondria allows the calculation of Pearson´s coefficients to assess colocalization. We
further examined simultaneous and sequential application regimes. To analyze synergistic
effects IC20/30 concentrations were chosen and synergism was calculated using the Bliss
independence model.
Results: In both B-ALL cell lines all inhibitors reduced cell count and metabolism after
monoapplication. SEM cell proliferation and metabolic activity were significantly decreased
by simultaneous treatment with venetoclax and PI3K inhibitors idelalisib or buparlisib as well
as AKT inhibitor perifosine (p<0.05 vs DMSO, ANOVA). The combined approach with AKT
inhibitor MK-2206, albeit not significant, showed similar results. Positive Bliss values
indicating synergism were calculated for all combinations. Interestingly, while the
combination of MK-2206 and venetoclax showed the weakest effect in SEM cells it was the
strongest in RS4;11. Here, all combinatorial approaches were superior to the single substances
but no significant improvement was detected. Still, mild anti-proliferative synergistic effects
were observed. While all combinations resulted in relevant tumor cell abrogation there was
no influence on healthy blood cells.
Further evaluation of sequential application regimes revealed no significant changes in anti-leukemic
efficacy. In SEM cells the exposure of venetoclax followed by PI3K/AKT inhibition
was comparable to the simultaneous application. Anti-metabolic effects were slightly weaker
when venetoclax was added after the PI3K/AKT inhibitor. Contrarily, RS4;11 cells were most
sensitive to simultaneous incubation or prior PI3K/AKT inhibition.
As expected, venetoclax induced cell death in both cell lines. Single PI3K/AKT inhibition hardly
induced apoptosis with only perifosine increasing apoptosis rates. Adding venetoclax
resembled the effect of the monoapplication of the BCL-2 inhibitor. An exceptional case is the
combination of venetoclax and perifosine which resulted in a prominent increase of apoptosis
in both cell lines. Colocalization of Bax and mitochondria indicating BCL-2 pathway-mediated
apoptosis induction was increased after monoapplication in SEM cells. Combined application
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