Identification of a nucleoside analog active against adenosine kinase–expressing plasma cell malignancies
Utthara Nayar, … , Kenneth M. Kaye, Ethel Cesarman
Utthara Nayar, … , Kenneth M. Kaye, Ethel Cesarman
Published May 15, 2017
Citation Information: J Clin Invest. 2017;127(6):2066-2080. https://doi.org/10.1172/JCI83936.
View: Text | PDF
Research Article Oncology

Identification of a nucleoside analog active against adenosine kinase–expressing plasma cell malignancies

Abstract

Primary effusion lymphoma (PEL) is a largely incurable malignancy of B cell origin with plasmacytic differentiation. Here, we report the identification of a highly effective inhibitor of PEL. This compound, 6-ethylthioinosine (6-ETI), is a nucleoside analog with toxicity to PEL in vitro and in vivo, but not to other lymphoma cell lines tested. We developed and performed resistome analysis, an unbiased approach based on RNA sequencing of resistant subclones, to discover the molecular mechanisms of sensitivity. We found different adenosine kinase–inactivating (ADK-inactivating) alterations in all resistant clones and determined that ADK is required to phosphorylate and activate 6-ETI. Further, we observed that 6-ETI induces ATP depletion and cell death accompanied by S phase arrest and DNA damage only in ADK-expressing cells. Immunohistochemistry for ADK served as a biomarker approach to identify 6-ETI–sensitive tumors, which we documented for other lymphoid malignancies with plasmacytic features. Notably, multiple myeloma (MM) expresses high levels of ADK, and 6-ETI was toxic to MM cell lines and primary specimens and had a robust antitumor effect in a disseminated MM mouse model. Several nucleoside analogs are effective in treating leukemias and T cell lymphomas, and 6-ETI may fill this niche for the treatment of PEL, plasmablastic lymphoma, MM, and other ADK-expressing cancers.

Authors

Utthara Nayar, Jouliana Sadek, Jonathan Reichel, Denise Hernandez-Hopkins, Gunkut Akar, Peter J. Barelli, Michelle A. Sahai, Hufeng Zhou, Jennifer Totonchy, David Jayabalan, Ruben Niesvizky, Ilaria Guasparri, Duane Hassane, Yifang Liu, Shizuko Sei, Robert H. Shoemaker, J. David Warren, Olivier Elemento, Kenneth M. Kaye, Ethel Cesarman

×

Figure 6

Expression of ADK and sensitivity to 6-ETI in plasma cell tumors.

Options: View larger image (or click on image) Download as PowerPoint
Expression of ADK and sensitivity to 6-ETI in plasma cell tumors. (A) BC...
(A) BC3 cells’ ADK expression was evaluated by immunohistochemistry in the BC3 cell line, hyperplastic tonsils, and PEL, MM, and plasmablastic lymphoma primary tumors (original magnification, ×60). Inset: In the image of a tonsil section, a positive cell with morphological features of a plasma cell is enlarged. Two-color immunohistochemistry showing a high-power image of plasma cells expressing both ADK and CD138. (B) LC50s for MM cell lines treated with 6-ETI for 48 hours were determined by CellTiter-Glo assay. BC3 was used as a positive control and IBL1 as a negative control for drug sensitivity. Shown is the mean ± SEM of 2 independent experiments, where each condition was performed in duplicate in each experiment. (C) U266 cells were treated with DMSO or 5 μM 6-ETI for 24 hours, then labeled with 10 μM EdU for 2 hours. EdU incorporation into the newly synthesized DNA was visualized using Click-iT EdU assay. The immunofluorescence images are representative of 2 independent experiments. Original magnification, ×100. (D) MM patient specimens (n = 9) were treated with increasing concentrations of 6-ETI ex vivo, followed by analysis for ATP content by CellTiter-Glo assay at 24 hours. LC50s were determined using GraphPad Prism. (E) Flow cytometry analysis showing the number of normal plasma cells isolated from human tonsils (CD19–, CD138+) before and after 6-ETI treatment. Data are representative of 2 independent experiments.