This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Genetic Basics Of Carcinogenesis, Subject name: Pathology
Cancers are usually associated with: 
Select and explain. 
A. Mutations in intronic genes, B. Hypomethylation of oncogenes, C. Methylation of tumor suppressor genes, D. Loss of heterogenicity
C: Methylation of tumor suppressor genes
Answer: C: Methylation of tumor suppressor genes 
Explanation: Epigenetic changes include:- alterations of chromatin structure mediated by methylation of cytosine residues in CpG dinucleotides modification of histones by acetylation or methylation. The transcriptional regulatory regions of active genes often contain a high frequency of CpG dinucleotides (referred to as CpG islands), which are normally unmethylated. Acetylation of the amino terminus of the core histones H3 and H4 induces an open chromatin conformation that promotes transcription initiation. Hypermethylation of promoter region is common mechanism by which tumor-supressor loci are epigentically silenced in cancer cells.