Shariful Islam's Abstracts
Shariful Islam
Ph.D. Student
Cancer Biology
Conference Summary
American Association for Cancer Research
Washington D.C.
Lay Abstract
Inhibition of Polyploidy and Senescence induces intrinsic Apoptosis in double
hit or double expresser Diffuse Large B-cell Lymphomas
Shariful Islam, Cancer Biology GIDP, University of Arizona Cancer Center, AZ
Wenqing Qi, West Cancer Center and UT Health Sciences Center, Memphis, TN
Carla Morales, West Cancer Center and UT Health Sciences Center, Memphis. TN
Laurence Cooke, Department of Medicine, University of Arizona Cancer Center, AZ
Catherine Spier, Department of Pathology, University of Arizona, AZ
Daruka Mahadevan, Department of Medicine, University of Arizona, Cancer Center, AZ
Background
Diffuse Large B-cell Lymphoma (DLBCL) especially the double-hit (DH)/ double-expresser
(DE) DLBCL is an aggressive subtype of Non-Hodgkin Lymphoma (NHL). A majority of
patients will fail frontline R-CHOP-like therapy and novel agents targeting MYC/BCL2 are
needed. Aurora kinases (AKs) are important regulators of mitosis, frequently over expressed
and strongly associated with MYC expression in human cancers including DLBCL. Preclinical
research and clinical studies have shown that aurora kinase inhibitors have a ~25-
30% response rate in B- and T- NHL. Here, we showed that alisertib-induced aneuploid and
senescence cells (AASCs) are responsible for treatment failure and can be overcome by
implementing a synthetic lethal approach by targeting Bruton’s Tyrosine kinase (Btk) with
ibrutinib and CD20 with rituximab.
Methods
SWOG 0515 DLBCL samples were assessed for AK and BTK expression by IHC. We
investigated U2932, U2904, OCI-Ly18 and VAL cell lines, where U2932 is a representative
of DE-DLBCL that over-expresses MYC, BCL2; and remaining are representative of DHDLBCL
that carries a three-way-translocation t(8;14;18) and over-expresses BCL2 and MYC.
AASCs were detected using cell permeable dye Hoechst-33342 and C12FDG with flow.
Phospho-kinase profiling was done with Proteome Profiler Human Phospho-Kinase Array kit
(R&D System). TUNEL assay was used to detect DNA breaks. Apoptosis was detected both
by flow using Caspase-3/7 and Annexin-V staining along side with PI and western blotting
for PARP cleavage. Cellular signaling pathways were investigated by Western blotting
analyses. Expression profiling of U2932 cells with alisertib elicits an enhanced proteasome
stress-response. Finally, to establish safety and efficacy of the triple combination, we tested
a DE-DLBCL SCID mouse U2932 xenograft model.
Results
AK and BTK are expressed in DLBCL patients and all 4-cell lines. AK inhibition with alisertib
in DH/DE-DLBCL induces cell death in ~30%, while ~70% are AASCs, a mitotic escape
mechanism contributing to drug resistance. These AASCs elaborated a high metabolic rate
by increased AKT/mTOR and ERK/MAPK activity via BTK signaling through the chronic
active B-cell receptor (BCR) pathway. Combinations of alisertib + ibrutinib or alisertib +
ibrutinib + rituximab significantly reduced AASCs with enhanced intrinsic cell death.
Inhibition of AK + BTK reduced phosphorylation of AKT/mTOR and ERK-1/2, up-regulated
phospho-H2A-X and Chk-2 (DNA damage), reduced Bcl-6 and decreased Bcl-2 and Bcl-xL
and induction of apoptosis by PARP cleavage. In a DE-DLBCL SCID mouse xenograft
model ibrutinib alone was inactive, while alisertib + ibrutinib was additive with a tumor growth
inhibition (TGI) rate of ~25%. However, TGI for ibrutinib + rituximab was ~50-60%. In
contrast, triple therapy showed a TGI rate of >90%. Kaplan-Meier survival analysis showed
67% of mice were alive at day-89 with triple therapy versus 20% with ibrutinib + rituximab.
All treatments were well tolerated with no changes in body weights. Harvested tumors
showed loss of expression Myc and Bcl2 by Western blotting in the triple combination.
Conclusion
A novel triple therapy consisting of alisertib + ibrutinib + rituximab inhibits AASCs induced by
AK inhibition in DH/DE-DLBCL leading to a significant anti-proliferative