Research Article: Transcription Factor DLX5 As a New Target for Promising Antitumor Agents

Date Published: , 2011

Publisher: A.I. Gordeyev

Author(s): R.A. Timakhov, P.O. Fedichev, A.A. Vinnik, J.R. Testa, O.O. Favorova.

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Abstract

The crystal structure of the human transcription factor DLX5 has been used for
the screening of a library consisting of 106 compounds by the
molecular docking technique.In vitro testsof
the 14 top-rated ligands showed that compound Q12 displays the best ability to
inhibit the proliferation ofDlx5 positive mouse lymphoma cells,
which correlates with the down-regulation ofc-mycexpression.
Compound Q12 has low toxicity on normal human ovarian epithelial cells and mouse
lymphoma cells with absent expression ofDlx5, and can be used
for further chemical optimization and for the development of novel, highly
efficient cancer treatments.

Partial Text

A wide range of drugs have been used in modern clinical practice in order to control
cancer [1­­–3]. However, even if all
the available drugs were to be used, the proportion of patients who respond to the
therapy would remain rather small. For this reason is critically necessary to design
new efficient targeted methods for cancer treatment based on a deep comprehension of
the mechanisms of tumor growth.

Ligand preparation and molecular docking

Screening for the new ligand molecules specific to DLX5 has been carried out with The
QUANTUM software suite, based on the analysis of the protein crystal structure [14,
24–26]. This approach not only
enables the identification of the molecules with potential to bind with a certain
protein, but also allows us to minimize the quantity of false positive results, when
the molecules with a high binding energy predicted in  
silico manifested no functional activity in the experiment.
The search was made more complicated by the absence of preliminary data on the
binding of the known compounds with DLX5 protein; therefore, blind studies were
performed. The best molecules and all their structural analogues from the original
ENAMINE library were sorted on the basis of their predicted binding energy.
According to the results of molecular docking, 100 ligands were selected; 14 of
those with the best predicted binding energy of DLX5 protein were ordered and
synthesized at ENAMINE company; then, they were tested on cell cultures.
Fig. 1 shows an
example of molecular docking with an active DLX5 site of one of these
ligands.

With the aim of verifying the fundamental possibility of using the DLX5 transcription
factor as a target for anti-tumor agents and designing drugs that can suppress the
development of certain types of human tumors (T-lymphomas, lung and ovarian cancer),
a search for specific ligands of the DLX5 factor was performed based on the analysis
of its crystal structure. It was shown that more than 50% of compounds which were
selected by docking technique are capable at micro-molar concentrations to inhibit
the proliferation of mouse lymphoma cells expressing Dlx5 .
Moreover, most of the compounds active on Dlx5 positive lymphoma cells had no effect
on other types of cells that do not express this transcription factor, which serves
as evidence of the specificity of the selected molecules. Compounds Q12 and Q9 were
found to be the best in terms of the ratio between the parameter characterizing the
efficacy and the absence of nonspecific cytotoxicity. The observed decrease in the
expression of с-myc under the action of Q12 attests to
the inhibitory effect of this ligand on the transcriptional activity of the Dlx5.
The compounds discovered are the first described low-molecular-weight ligands of
DLX5 which can be used for subsequent chemical optimization and the development of
highly efficient anti-tumor agents.

 

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