High-Throughput Computer Screen Aids Discovery of Methotrexate as miR-20b Inhibitor to Suppress Nonsmall Cell Lung Cancer Progression

MicroRNAs (miRNAs) play a significant role in tumor progression,
and regulating miRNA expression with small molecules may offer a new
approach to cancer therapy. Among them, miRNA-20b has been found to
be dysregulated in several cancers, including nonsmall cell lung cancer
(NSCLC). Herein, an in silico high-throughput computer screen was
conducted to identify small molecules that downregulate miR-20b using
the three-dimensional structure of the Dicer binding site on pre-miR-20b.
Among 1058 small molecule compounds, Methotrexate (MTX), was discovered
to be a potential miR-20b-specific inhibitor, which has been found
to suppress miR-20b by specifically blocking Dicer processing in p53
wild-type A549 NSCLC cells but not in H1299 cells with p53 depletion.
MTX effectively inhibited the proliferation, survival, migration,
and invasion of A549 cells in a dose-dependent manner. Furthermore,
the treatment of MTX up-regulated the expression of miR-20b target
genes PTEN, STAT3, and HIF1α. Notably, MTX also significantly
inhibited tumor growth in a mouse xenograft tumor model of NSCLC,
with no observed tissue toxicity. Our findings indicate that MTX may
have a novel role as an established drug in p53 wild-type NSCLC tumor
therapy by down-regulating miR-20b expression. These findings are
expected to provide preclinical evidence for miR-20b-targeting NSCLC
therapeutic strategies.