Food-derived Compounds Apigenin and Luteolin Modulate mRNA Splicing of Introns with Weak Splice Sites

Cancer cells often exhibit extreme sensitivity to splicing inhibitors. We identified food-derived flavonoids, apigenin and luteolin, as compounds that modulate mRNA splicing at the genome-wide level, followed by proliferation inhibition. They bind to mRNA splicing-related proteins to induce a widespread change of splicing patterns in treated cells. Their inhibitory activity on splicing is relatively moderate, and introns with weak splice sites tend to be sensitive to them. Such introns remain unspliced, and the resulting intron-containing mRNAs are retained in the nucleus, resulting in the nuclear accumulation of poly(A)+ RNAs in these flavonoid-treated cells. Tumorigenic cells are more susceptible to these flavonoids than non-tumorigenic cells, both for the nuclear poly(A)+ RNA-accumulating phenotype and cell viability. This study illustrates the possible mechanism of these flavonoids to suppress tumor progression in vivo that were demonstrated by previous studies, and provides the potential of daily intake of moderate splicing inhibitors to prevent cancer development. U2OS cells were treated with DMSO or 75μM apigenin or 75μM luteolin for 24 h and then harvested. Total RNA was extracted from biological duplicate samples with Sepasol-RNA I super G. RNA-seq library was prepared using Truseq Stranded mRNA Library Prep Kit (Illumina, CA) and sequenced on an NextSeq Highoutput (Illumina, CA).