Combining Ibrutinib with Chk1 Inhibitors Synergistically Targets Mantle Cell Lymphoma Cell Lines
Mantle cell lymphoma (MCL) is an aggressive B cell lymphoma with an unfavorable clinical course. Besides deregulation of the cell cycle, B cell receptor (BCR) signaling, essential for MCL proliferation and survival, is also often deregulated due to constitutive activation of Bruton’s tyrosine kinase (BTK). The BTK inhibitor ibrutinib has been approved as a therapy for refractory MCL, and while it shows some clinical activity, patients frequently develop primary or secondary ibrutinib resistance and have very poor outcomes after relapsing following ibrutinib treatment.
To overcome ibrutinib resistance, new therapeutic approaches are needed. As checkpoint kinase 1 (Chk1) inhibitors have recently been shown to be effective as single agents in MCL, we assessed the combination of ibrutinib with Chk1 inhibitors.
We examined the activity of ibrutinib combined with the Chk1 inhibitor PF-00477736 in eight MCL cell lines and analyzed underlying cellular and molecular effects.
The combination was synergistic in all tested cell lines through different mechanisms. The treatment induced apoptosis in ibrutinib-sensitive cell lines, while in ibrutinib-resistant cells the effect was mainly cytostatic and occurred at micromolar concentrations of ibrutinib.
We thank J.D. Baggott who kindly edited the paper. This work is dedicated to the memory of Eugenio and Angela Filice.
Compliance with Ethical Standards
This work was supported by the Italian Association for Cancer Research (AIRC), Milan, Italy (MFAG14456 to Laura Carrassa), and partially supported by the Gelu Foundation (to Francesco Bertoni).
Conflict of Interest
The authors declare no competing financial interests.
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