Scaffold-based analogs of cinnamic acid benzyl amide (CABA) exhibit pleiotropic effects in cancer cells, and
their exact molecular mechanism of action is under investigation. The present study is part of our systemic analysis of
interactions of CABA analogs with their molecular targets. These compounds were shown to inhibit Janus kinase 2
(JAK2)/signal transducer and activator of transcription 3 (STAT3) and JAK2/signal transducer and activator of
transcription 5 (STAT5) signaling and thus are attractive scaffolds for anticancer drug design. To identify the potential
mechanisms of action of this class of compounds, direct interactions of the selected CABA analogs with JAK2 kinase
were examined. Inhibition of JAK2 enzymatic activity was assessed, and molecular modeling studies of selected
compounds—(E)-2-cyano-N-[(S)-1-phenylethyl]-3-(pyridin-2-yl)acrylamide (WP1065), (E)-2-cyano-N-[(S)-1-phenylbutyl]-
3-(3-bromopyridin-2-yl)acrylamide (WP1130), and (E)-2-cyano-N-[(S)-1,4-diphenylbutyl]-3-(3-bromopyridin-2-yl)acrylamide
(WP1702)—in the JAK2 kinase domain were used to support interpretation of the experimental data. Our results indicated
that the tested CABA analogs are nonclassical inhibitors of activated (phosphorylated) JAK2, although markedly weaker
than clinically tested ATP-competitive JAK2 inhibitors. Relatively small structural changes in the studied compounds
affected interactions with JAK2, and their mode of action ranged from allosteric-noncompetitive to bisubstratecompetitive.
These results demonstrated that direct inhibition of JAK2 enzymatic activity by the WP1065 (half-maximal
inhibitory concentration [IC50] = 14.8 µM), WP1130 (IC50 = 3.8 µM), and WP1702 (IC50 = 2.9 µM) potentially
contributes, albeit minimally, to suppression of the JAK2/STAT signaling pathways in cancer cells and that additional
specific structural modifications may amplify JAK2-inhibitory effects.
Keywords: Bisubstrate-competitive, CABA, cinnamic acid, inhibitor, JAK2, molecular modeling, noncompetitive, STAT3,
STAT5, WP1065, WP1130, WP1702.
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