FoxO1/Rictor axis induces a nongenetic adaptation to ibrutinib via Akt activation in chronic lymphocytic leukemia
Laura Ondrisova, … , Jiri Mayer, Marek Mraz
Laura Ondrisova, … , Jiri Mayer, Marek Mraz
Published October 22, 2024
Citation Information: J Clin Invest. 2024;134(23):e173770. https://doi.org/10.1172/JCI173770.
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Research Article Hematology Oncology

FoxO1/Rictor axis induces a nongenetic adaptation to ibrutinib via Akt activation in chronic lymphocytic leukemia

Abstract

Bruton tyrosine kinase (BTK) inhibitor therapy induces peripheral blood lymphocytosis in chronic lymphocytic leukemia (CLL), which lasts for several months. It remains unclear whether nongenetic adaptation mechanisms exist, allowing CLL cells’ survival during BTK inhibitor–induced lymphocytosis and/or playing a role in therapy resistance. We show that in approximately 70% of CLL cases, ibrutinib treatment in vivo increases Akt activity above pretherapy levels within several weeks, leading to compensatory CLL cell survival and a more prominent lymphocytosis on therapy. Ibrutinib-induced Akt phosphorylation (pAktS473) is caused by the upregulation of Forkhead box protein O1 (FoxO1) transcription factor, which induces expression of Rictor, an assembly protein for the mTORC2 protein complex that directly phosphorylates Akt at serine 473 (S473). Knockout or inhibition of FoxO1 or Rictor led to a dramatic decrease in Akt phosphorylation and growth disadvantage for malignant B cells in the presence of ibrutinib (or PI3K inhibitor idelalisib) in vitro and in vivo. The FoxO1/Rictor/pAktS473 axis represents an early nongenetic adaptation to B cell receptor (BCR) inhibitor therapy not requiring PI3Kδ or BTK kinase activity. We further demonstrate that FoxO1 can be targeted therapeutically and its inhibition induces CLL cells’ apoptosis alone or in combination with BTK inhibitors (ibrutinib, acalabrutinib, pirtobrutinib) and blocks their proliferation triggered by T cell factors (CD40L, IL-4, and IL-21).

Authors

Laura Ondrisova, Vaclav Seda, Krystof Hlavac, Petra Pavelkova, Eva Hoferkova, Giorgia Chiodin, Lenka Kostalova, Gabriela Mladonicka Pavlasova, Daniel Filip, Josef Vecera, Pedro Faria Zeni, Jan Oppelt, Zuzana Kahounova, Rachel Vichova, Karel Soucek, Anna Panovska, Karla Plevova, Sarka Pospisilova, Martin Simkovic, Filip Vrbacky, Daniel Lysak, Stacey M. Fernandes, Matthew S. Davids, Alba Maiques-Diaz, Stella Charalampopoulou, Jose I. Martin-Subero, Jennifer R. Brown, Michael Doubek, Francesco Forconi, Jiri Mayer, Marek Mraz

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Figure 7

FoxO1 inhibition overcomes microenvironmental protection and blocks CLL cells’ proliferation induced by T cell factors.

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FoxO1 inhibition overcomes microenvironmental protection and blocks CLL ...
(A and B) Relative viability of primary CLL cells cocultured with HS5 cells. CLL cells were cocultured for 5 or 10 days on (A) WT HS5 or (B) HS5CD40L,IL-4,IL-21 and treated with ibrutinib (1 μM), acalabrutinib (acal, 1 μM), FoxO1 inhibitor (0.5 μM), or their combination. (C and D) Proliferation of primary CLL cells cocultured with stromal cells HS5CD40L,IL-4,IL-21 treated with ibrutinib (1 μM), FoxO1 inhibitor (0.5 μM), or their combination. (C) Representative CFSE staining histogram in 2 primary CLL samples. Proliferation rate quantified by dilution of CFSE signal. (D) Probability (calculated from precursor frequency) that cells will divide at least once (n = 10). (E) Cell cycle measured by propidium iodide (PI) staining in MEC1 cells treated with ibrutinib (1 μM), FoxO1 inhibitor (0.5 μM), or their combination for 96 hours (n = 5). P values are calculated for differences in percentages of cells in S phase. (F and G) Relative viability of primary CLL cells obtained for patients at the time of progression on BTK inhibitors and cocultured for 5 or 10 days on (F) WT HS5 or (G) HS5CD40L,IL-4,IL-21 and treated with FoxO1 inhibitor (0.5 μM). (H) Relative levels of cell-surface CD20 and CXCR4 levels in primary CLL cells (n = 9) treated with FoxO1 inhibitor (0.5 μM, 48 hours). For patient characteristics, see Supplemental Table 8. All P values in Figure 6 were calculated using paired t test.