Improving nelarabine efficacy in T cell acute lymphoblastic leukemia by targeting aberrant PI3K/AKT/mTOR signaling pathway

Abstract

BackgroundAlthough in recent years, the introduction of novel chemotherapy protocols has improved the outcome of T cell acute lymphoblastic leukemia (T-ALL) patients, refractory and/or relapsing disease remains a foremost concern. In this context, a major contribution was provided by the introduction of the nucleoside analog nelarabine, approved for salvage treatment of T-ALL patients with refractory/relapsed disease. However, nelarabine could induce a life-threatening, dose-dependent neurotoxicity. To improve nelarabine efficacy, we have analyzed its molecular targets, testing selective inhibitors of such targets in combination with nelarabine.MethodsThe effectiveness of nelarabine as single agent or in combination with PI3K, Bcl2, and MEK inhibitors was evaluated on human T-ALL cell lines and primary T-ALL refractory/relapsed lymphoblasts. The efficacy of signal modulators in terms of cytotoxicity, induction of apoptosis, and changes in gene and protein expression was assessed by flow cytometry, western blotting, and quantitative real-time PCR in T-ALL settings.ResultsTreatment with nelarabine as a single agent identified two groups of T-ALL cell lines, one sensitive and one resistant to the drug. Whereas sensitive T-ALL cells showed a significant increase of apoptosis and a strong down-modulation of PI3K signaling, resistant T-ALL cells showed a hyperactivation of AKT and MEK/ERK1/2 signaling pathways, not caused by differences in the expression of nelarabine transporters or metabolic activators. We then studied the combination of nelarabine with the PI3K inhibitors (both pan and dual γ/δ inhibitors), with the Bcl2 specific inhibitor ABT199, and with the MEK inhibitor trametinib on both T-ALL cell lines and patient samples at relapse, which displayed constitutive activation of PI3K signaling and resistance to nelarabine alone. The combination with the pan PI3K inhibitor ZSTK-474 was the most effective in inhibiting the growth of T-ALL cells and was synergistic in decreasing cell survival and inducing apoptosis in nelarabine-resistant T-ALL cells. The drug combination caused AKT dephosphorylation and a downregulation of Bcl2, while nelarabine alone induced an increase in p-AKT and Bcl2 signaling in the resistant T-ALL cells and relapsed patient samples.ConclusionsThese findings indicate that nelarabine in combination with PI3K inhibitors may be a promising therapeutic strategy for the treatment of T-ALL relapsed patients.Electronic supplementary materialThe online version of this article (doi:10.1186/s13045-016-0344-4) contains supplementary material, which is available to authorized users.

Targeting Wnt/β‐catenin and PI3K/Akt/mTOR pathways in T‐cell acute lymphoblastic leukemia

“…Results were normalized to the level of the ubiquitously expressed RNA 18S ribosomal 1 gene, while the Universal Human Reference RNA (Agilent) was used as control. Results were expressed as (Δ C t = [(CT gene of interest − CT internal control) to compare the relative gene expression among samples, and as (ΔΔ C t = [(CT gene of interest − CT internal control) sample − (CT gene of interest − CT internal control) universal]) to compare gene expression of the treated cell lines with that of untreated control (Lonetti et al, ).…”

Tanshinone IIA enhances the inhibitory effect of imatinib on proliferation and motility of acute leukemia cell line TIB‑152 in�vivo and in�vitro by inhibiting the PI3K/AKT/mTOR signaling pathway

“…Cell biological functions, such as cell proliferation, apoptosis and metastasis, are regulated by various signal transduction pathways in the cell. PI3K/AKT/mTOR is one of the most important signal transduction pathways and its abnormal activation is closely associated with the occurrence and development of malignant tumors (44). This pathway is recognized as a key point in tumor regulation and is an important target for anticancer drug selection (19,44).…”

“…PI3K/AKT/mTOR is one of the most important signal transduction pathways and its abnormal activation is closely associated with the occurrence and development of malignant tumors (44). This pathway is recognized as a key point in tumor regulation and is an important target for anticancer drug selection (19,44). The PI3K/AKT/mTOR signaling pathway is abnormally activated in various tumors, such as leukemia, lymphoma and breast cancer (44).…”

“…This pathway is recognized as a key point in tumor regulation and is an important target for anticancer drug selection (19,44). The PI3K/AKT/mTOR signaling pathway is abnormally activated in various tumors, such as leukemia, lymphoma and breast cancer (44). In leukemia, multiple targets in the PI3K/AKT/mTOR signaling pathway are abnormally activated and these constitute important targets for the development of therapeutic drugs (45,46).…”

Metronomic combination chemotherapy using everolimus and etoposide for the treatment of non‐Hodgkin lymphoma

“…Previous studies demonstrated that RAD001 alone had anti‐proliferative effects in various malignancies, including renal cancer, breast cancer, non‐small cell lung cancer, and pancreatic neuroendocrine tumors . Moreover, studies showed that mTOR inhibitors in combination with other traditional chemotherapeutic agents (cyclophosphamide, doxorubicin, vincristine，prednisone) presented better efficacy in treating NHL …”