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Oncogenetic (L.D., O.U., T.T, S.Y., M.L., M.L.) and Hematology (H.S., J.R.) Laboratories and Department of Medicine (M.L., M.L.), Sapir Medical Center, Kfar-Saba, Israel; and Tel-Aviv University, Tel-Aviv, Israel (M.L., M.L.)
Thalidomide (Thd), a potent teratogen, was shown to have therapeutic
potential in cancer, primarily in multiple myeloma (MM), yet its mechanism of
action has not been elucidated. It was recently suggested that its
teratogenicity is derived from interference in expression of genes regulated
by GC-rich promoters by blocking the binding of SP1 transcription factor to
its motif. We explored the validation of the proposed model by focusing on
potential molecular targets associated with MM pathogenesis. Cell lines RPMI
8226, U266, and ARH-77 were exposed for 24 h to racemic Thd and analyzed for
apoptosis, membranal expression of CD29 and CD63, transcript level of hTERT,
CD63, and IGFI-R (characterized by GC-rich motifs) and telomerase activity.
Analysis of an hTERT core promoter reporter gene expression [enhanced green
fluorescent protein (EGFP)] in transiently transfected RPMI 8226 incubated
with racemic and steric (±)-enantiomers of Thd was performed. A
consistent reduction (
1040%) in transcript levels of all three
assayed genes in all three cell lines was demonstrated in the presence of
racemic Thd. Significant reduction of EGFP was demonstrated in cells
transfected with hTERT reporter gene and treated with racemic and
(S)-Thd. Our results show that Thd's antimyeloma activity can be
ascribed to the same mechanism responsible for its teratogenic effect and that
the inhibition of GC-rich promoter genes is mostly attributed to the
S-racemate. Indeed, this selectivity delineates GC-rich promoter
genes as a unique group eligible for specific drug targeting.
Address correspondence to: Dr. Liat Drucker, Oncogenetic Laboratory, Sapir Medical Center, Meir Hospital, Kfar Sava, 44281, Israel. E-mail: druckerl{at}clalit.org.il
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