Downregulation of ribosomal RNA (rRNA) genes in human head and neck squamous cell carcinoma (HNSCC) cells is linked to rDNA promoter hypermethylation

Eukaryotes carry hundreds of ribosomal RNA (rRNA) genes as tandem arrays, which generate rRNA for protein synthesis. Humans carry ~ 400 rRNA gene copies, which are epigenetically regulated. Dysregulation of rRNA synthesis and ribosome biogenesis are characteristic features of cancers. Targeting aberrant rRNA expression for cancer therapy is being explored. Head and neck squamous cell carcinoma (HNSCC) is among the most prevalent cancers globally. Using quantitative PCR and bisulfite sequencing, we show that rRNA genes are downregulated and their promoters are hypermethylated in HNSCC cell lines. These finding may have relevance for prognosis and diagnosis for HNSCC.