Differential DNMT, HDAC, and MicroRNA Expression Among Oral Cancers

Objectives: Dysregulations of DNA and histone methylation facilitated by DNA methyltransferase (DNMT)-1
and DNMT-3 are associated with the development and progression of oral cancers. Little is
known about how DNMT-1 and DNMT-3 alter epigenetic pathways including histone
deacetylases (HDACs) in oral cancers. This project evaluated DMNT and HDAC expression
among oral cancers compared with normal, non-cancerous cells.
Methods: Using commercially available oral squamous carcinoma cell lines and the non-cancerous normal
human gingival fibroblast (HGF-1), RNA was converted to cDNA and was used to screen for
mRNA expression using qPCR. Validated primers for DNMT1, DMNT3a, DNMT3b, HDAC1, and HDAC2 were used to evaluate the expression of mRNA specific to each gene.
Results: This screening revealed that the non-cancerous cell line HGF-1 expresses DNMT1
(homeostasis) and does not express any genes associated with dysregulation. Some of the oral
cancer cell lines continue to express DNMT1 (SCC9, SCC15), although this expression is lost
among SCC4, SCC25, and CAL27. However, all of the oral cancers expressed both DNMT3a/b,
as well as one or more of the HDACs.
Next, an analysis of microRNAs that regulate DNMT and HDAC expression was performed. This
revealed all oral cancers produced miR-21, although the normal cell line did not. In addition,
only the normal cell line and one cancer line with no chemotherapy resistance (SCC15)
produced miR-145.
Conclusions: These results show differences between the normal, non-cancerous cell line HGF-1 (expressing
DNMT1 but not DNMT3 or HDACs) and the oral cancers (expressing DNMT3 and some
expressing one or more HDACs). Preliminary results with microRNA appear to demonstrate
differential expression of miR-145 among the normal non-cancerous cell line and the single oral
cancer that do not display chemotherapy resistance (SCC15).