Restoring KLF4 expression by treating the cells with the demethylating agent 5-Aza inhibited the proliferation of SiHa and C33A cells. Our results support the hypothesis that KLF4 promoter methylation inactivates the gene’s function as a tumor suppressor in cervical carcinogenesis. Epigenetic gene silencing through DNA methylation has been suggested to be one of the important steps in cervical carcinogenesis. Promoter hypermethylation of P16, DKAP, CDH1 and other related tumor suppressor genes was linked to clinical pathological parameters in cervical cancer. In contrast, methylated carcinogenic HPV DNA was a predictive and/or diagnostic biomarker for risk of cervical cancer among HPV-positive women. KLF4 has been shown to interact with a number of pathways with well-documented links to cervical cancer biology. KLF4 transactivates the expression of the cell cycle inhibitor p27Kip, which is associated with malignant transformation and aggressive phenotypes of cervical neoplasms. KLF4 represses the Wnt signaling pathway, which was shown to be hyperactivated in a subset of cervical cancer. Notch signaling represses KLF4 in the gastrointestinal tract. Epithelial transformation by KLF4 requires CX-4945 side effects Notch1 but not canonical Notch1 signaling, and Notch signaling plays an important role in the development and progression of cervical cancer. This result prompted us to further explore the mechanism of action of KLF4 in cervical cancer. Here, we determined that KLF4 promoter methylation was 4- fold higher in cancer samples and also markedly higher in some cervical cancer cell lines, compared with control samples. KLF4 expression was inversely related to methylation status. Moreover, the expression of KLF4 protein and mRNA was restored upon treatment of cervical cancer cell lines with 5-Aza, which inhibited the cell proliferation and increased the chemosensitivity for cisplatin. These findings indicate that promoter methylation suppresses KLF4 gene transcription and thus contributes to inactivating KLF4’s tumor suppressor function in cervical carcinogenesis. Although mutation of the KLF4 gene was shown to cause a defect in the proliferation and differentiation of gastric mucosal epithelium, it was concluded that a genetic alteration of the KLF4 gene might play a minor role in gastric carcinogenesis. KLF4 is inactivated by either genetic or epigenetic mechanisms in a large subset of medulloblastomas, and it likely functions as a tumor suppressor gene in the pathogenesis of medulloblastoma. The methylation of the KLF4 promoter region in cervical cancer was different from that of other type of tumors. Further studies should focus on identifying the key region influencing KLF4 gene expression, by using KLF4 genome-wide methylation scanning. In summary, by using the BSQ technology, we uncovered a change in the methylation status of the KLF4 gene in cervical cancer.