Simultaneous Inhibition of PI3Kδ and PI3Kα Induces ABC-DLBCL Regression by Blocking BCR-Dependent and -Independent Activation of NF-κB and AKT

Publication date: 9 January 2017
Source:Cancer Cell, Volume 31, Issue 1
Author(s): Juliane Paul, Maurice Soujon, Antje M. Wengner, Sabine Zitzmann-Kolbe, Andrea Sturz, Katja Haike, Koh Hui Keng Magdalene, Sze Huey Tan, Martin Lange, Soo Yong Tan, Dominik Mumberg, Soon Thye Lim, Karl Ziegelbauer, Ningshu Liu
Compared with follicular lymphoma, high PI3Kα expression was more prevalent in diffuse large B cell lymphoma (DLBCL), although both tumor types expressed substantial PI3Kδ. Simultaneous inhibition of PI3Kα and PI3Kδ dramatically enhanced the anti-tumor profile in ABC-DLBCL models compared with selective inhibition of PI3Kδ, PI3Kα, or BTK. The anti-tumor activity was associated with suppression of p-AKT and a mechanism of blocking nuclear factor-κB activation driven by CD79^mut, CARD11^mut, TNFAIP3^mut, or MYD88^mut. Inhibition of PI3Kα/δ resulted in tumor regression in an ibrutinib-resistant CD79B^WT/MYD88^mut patient-derived ABC-DLBCL model. Furthermore, rebound activation of BTK and AKT was identified as a mechanism limiting CD79B^mut-ABC-DLBCL to show a robust response to PI3K and BTK inhibitor monotherapies. A combination of ibrutinib with the PI3Kα/δ inhibitor copanlisib produced a sustained complete response in vivo in CD79B^mut/MYD88^mut ABC-DLBCL models.

Graphical abstract

Teaser

Paul et al. reveal that ABC-DLBCL expresses high levels of PI3Kα and PI3Kδ, leading to downstream activation of both NF-κB and AKT signaling. Treatment with the dual PI3Kα/δ inhibitor copanlisib has strong anti-tumor activity and synergizes with the BTK inhibitor ibrutinib, causing tumor remission in DLBCL models.


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