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.
View: Text | PDF
Research Article Hematology Oncology Article has an altmetric score of 12

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

×

Figure 1

CLL cells induce Akt phosphorylation during ibrutinib treatment.

Options: View larger image (or click on image) Download as PowerPoint
CLL cells induce Akt phosphorylation during ibrutinib treatment. (A) Rep...
(A) Representative pAktS473 immunoblots in primary CLL samples (n = 2) obtained before and during ibrutinib treatment in vivo. (B) Densitometric quantification of relative pAktS473 protein levels in primary CLL samples obtained before and during ibrutinib treatment in vivo (n = 31). P value for trend calculated with linear mixed-effect model; other P values were calculated using paired t test. Black lines indicate samples with pAktS473 upregulation (n = 22) or stable levels (n = 2); blue lines indicate samples with pAktS473 downregulation (n = 7). The pAktS473 levels were normalized to both total Akt and GAPDH (loading control) to obtain precise quantification. For patient characteristics, see Supplemental Table 8. (C) Representative immunoblot of MEC1 cells treated with ibrutinib (2 μM, 1–5 days). (D) Densitometric quantification of relative pAktS473 protein levels in MEC1 cells treated with ibrutinib (2 μM) for 1–5 days (n = 4). The pAktS473 levels at day 0 were set as 1. Fresh ibrutinib was added to culture media each day. P values were calculated using paired t test. (E) Relative absolute lymphocyte count (ALC) in patients treated with ibrutinib in vivo that had upregulated/stable (n = 23) or downregulated (n = 6) levels of pAktS473 in the first 12 weeks of the therapy (stratification according to B). All samples with available clinical data were analyzed. P values were calculated using Mann-Whitney U test. (F) Relative viability of CLL samples (n = 4) obtained from patients before and after 4 weeks (n = 2), 6 weeks (n = 1), or 8 weeks (n = 1) of ibrutinib therapy in vivo and treated (72 hours) with Akt inhibitor MK-2206 (1.25, 2.5, 5, and 10 μM) or a combination of ibrutinib (ibr, 1 μM) and MK-2206 (1.25, 2.5, 5, and 10 μM), or vehicle. Statistical difference was tested using 2-way ANOVA with Geisser-Greenhouse correction. For patient characteristics, see Supplemental Table 8.