ABCG2 and nasopharyngeal carcinoma: In a study by Wang et al., afatinib, a tyrosine kinase inhibitor, has been found to increase DNMT activity, resulting in hypermethylation of the ABCG2 promoter and lower ABCG2 mRNA levels in several ABCG2 overexpressing cell lines: MCF7-FLV1000, a flavopiridol-resistant subline of the breast cancer cell line MCF7; S1-M1-80, a mitoxantrone-selected subline of the colon carcinoma cell line S1; CNE-2-s18, a high-metastatic clone of the nasopharyngeal carcinoma cell line CNE2 [190].