Because of the theoretical relationship between gene promoter hypermethylation as an epigenetic modification with the downregulation of gene transcription, we analyzed HLA-B, TAP1, TAP2, LMP2, LMP7, ERAP1, tapasin, and ERp57, due to the downregulation of these genes in cervical cancer or precursor lesions, for methylation status of CpG islands at the promoter region in SiHa cervical carcinoma cells by bisulfite-sequencing approach. The gene discussed is PDIA3; the disease is cervical cancer.