American Association for Cancer Research
15357163mct111021-sup-fig4.pdf (653.12 kB)

Supplementary Figure 4 from Characterization of the Mechanism of Action of the Pan Class I PI3K Inhibitor NVP-BKM120 across a Broad Range of Concentrations

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journal contribution
posted on 2023-04-03, 13:41 authored by Saskia M. Brachmann, Julia Kleylein-Sohn, Swann Gaulis, Audrey Kauffmann, Marcel J.J. Blommers, Malika Kazic-Legueux, Laurent Laborde, Marc Hattenberger, Fabian Stauffer, Juliane Vaxelaire, Vincent Romanet, Chrystèle Henry, Masato Murakami, Daniel Alexander Guthy, Dario Sterker, Sebastian Bergling, Christopher Wilson, Thomas Brümmendorf, Christine Fritsch, Carlos Garcia-Echeverria, William R. Sellers, Francesco Hofmann, Sauveur-Michel Maira

PDF file, 653KB, MDA-MB231 (left) and U87MG (right) cells grown on coverslips were treated for 24 h either with BKM120 (5 μM) or Nocodazole (100 nM) and the effects of compound treatment on microtubule dynamics and G2/M arrest was monitored by immuno-fluorescence staining of alpha-tubulin (microtubules), gamma tubulin (centrosomes) and DAPI (DNA). Pictures were taken with a 100X objective.



The pan-phosphoinositide 3-kinase (PI3K) inhibitor BKM120 was found, at high concentrations, to cause cell death in various cellular systems, irrespective of their level of PI3K addiction. Transcriptional and biochemical profiling studies were used to identify the origin of these unexpected and apparently PI3K-independent effects. At 5- to 10-fold, the concentration needed to half-maximally inhibit PI3K signaling. BKM120 treatment caused changes in expression of mitotic genes and the induction of a robust G2–M arrest. Tubulin polymerization assays and nuclear magnetic resonance-binding studies revealed that BKM120 inhibited microtubule dynamics upon direct binding to tubulin. To assess the contribution of this off-target activity vis-à-vis the antitumor activity of BKM120 in PI3K-dependent tumors, we used a mechanistic PI3K-α–dependent model. We observed that, in vivo, daily treatment of mice with doses of BKM120 up to 40 mg/kg led to tumor regressions with no increase in the mitotic index. Thus, strong antitumor activity can be achieved in PI3K-dependent models at exposures that are below those necessary to engage the off-target activity. In comparison, the clinical data indicate that it is unlikely that BKM120 will achieve exposures sufficient to significantly engage the off-target activity at tolerated doses and schedules. However, in preclinical settings, the consequences of the off-target activity start to manifest themselves at concentrations above 1 μmol/L in vitro and doses above 50 mg/kg in efficacy studies using subcutaneous tumor–bearing mice. Hence, careful concentration and dose range selection is required to ensure that any observation can be correctly attributed to BKM120 inhibition of PI3K. Mol Cancer Ther; 11(8); 1747–57. ©2012 AACR.