8-amino-adenosine is a potential therapeutic agent for multiple myeloma.
Multiple myeloma (MM) is a malignancy of clonal B-cells that accounts for 10% of all hematologic malignancies. We have shown previously that a novel purine analogue, 8-chloro-adenosine, has significant activity for MM in preclinical studies.


OBJECTIVE
Using MM cell lines, we investigated the molecular mechanism of related congener of adenosine, 8-amino-adenosine (8-NH2-Ado).


METHODS
We employed biological and biochemical assays in MM cell lines to evaluate the clinical potential of 8-NH2-Ado.


RESULTS
In MM cell lines both sensitive and resistant to conventional chemotherapies, 8-NH2-Ado is cytotoxic, with IC50 ranging from 300 nmol/L to 3 micromol/L. A mouse leukemic cell line lacking adenosine kinase activity was resistant to 8-NH2-Ado, indicating that phosphorylation of 8-NH2-Ado to its triphosphate form is required for cytotoxicity. A 4-hour incubation of MM cells with 10 micromol/L analogue resulted in an accumulation of >7 mmol/L 8-NH2-ATP with a parallel decline in the endogenous ATP levels. Accumulation of 8-NH2-ATP was dependent on both exogenous concentration of 8-NH2-Ado and incubation time. The accumulation of 8-NH2-ATP was accompanied by a decrease in both RNA and DNA synthesis. The mechanism of 8-NH2-Ado-mediated cytotoxicity was due to apoptosis as measured by an increase in Annexin V binding, a decrease in mitochondrial membrane potential, an increase in caspase activity, cleavage of caspase substrates, and an increase in cells with a sub-G1 DNA content.


CONCLUSIONS
Based on these results, we conclude that 8-NH2-Ado may hold great potential as a therapeutic agent for the treatment of MM.
Krett
Nancy L
NL
Division of Hematology Oncology, Department of Medicine, Robert H. Lurie Comprehensive Cancer Center, Feinberg School of Medicine, Northwestern University Medical School, Chicago, IL 60611, USA. n-krett@northwestern.edu
Davies
Katharine M
KM
Ayres
Mary
M
Ma
Chunguang
C
Nabhan
Chadi
C
Gandhi
Varsha
V
Rosen
Steven T
ST
D000241:Adenosine / Q000031:analogs & derivatives* / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology* / Q000633:toxicity; D017209:Apoptosis / Q000187:drug effects; D020169:Caspases / Q000378:metabolism; D045744:Cell Line, Tumor; D004247:DNA / Q000096:biosynthesis; D004305:Dose-Response Relationship, Drug; D004789:Enzyme Activation / Q000187:drug effects; D006801:Humans; D015394:Molecular Structure; D009101:Multiple Myeloma / Q000201:enzymology / Q000235:genetics / Q000378:metabolism / Q000473:pathology*; D010766:Phosphorylation / Q000187:drug effects; D011122:Polyphosphates / Q000737:chemistry; D012313:RNA / Q000096:biosynthesis
D011122:Polyphosphates; C010533:8-aminoadenosine; D012313:RNA; D004247:DNA; D020169:Caspases; D000241:Adenosine; C005692:triphosphoric acid