question: Could DNA (cytosine-5-)-methyltransferases serve as tumour markers?
answer: Yes. It has been demonstrated in a number of experimental studies that DNA (Cytosine-5-)-methyltransferases (DNMT1, DNMT3A and DNMT3B) are deregulated in several types of cancer (invasive cervical cancer, colon cancer, esophageal squamous cell carcinoma (ESCC), gastric cancer, embryonal carcinoma, cervical cancer, adenoma, adenoid cystic carcinoma, salivary gland neoplasms). Moreover, three single nucleotide polymorphisms (SNPs) of the DNMT3B promoter region have been reported to be stratification markers that can predict an individual's susceptibility to cancers. Therefore,  DNA (Cytosine-5-)-methyltransferases can serve as tumour markers.