Krüppel-like Factor 4-Deficient Cells Are Sensitive to Etoposide-Induced DNA Damage

Krüppel-like factor 4 (KLF4) is a highly conserved zinc-finger transcription factor involved in cellular processes such as development, differentiation, and cell cycle regulation. Previous studies show that mouse embryonic fibroblasts (MEFs) null for Klf4 exhibit increased genomic instability. While KLF4 is regarded as a tumor suppressor in many human cancers, its role in DNA repair mechanisms remains unknown. In this study, cultured MEFs wild type (+/+) and null (-/-) for Klf4 and human carcinoma colorectal (RKO) cells were studied as a model for human colorectal cancer. Etoposide, a chemotherapeutic topoisomerase II poison, was employed to investigate KLF4's role in DNA damage repair. Following etoposide treatment, immunostaining and Western blotting revealed cells expressing Klf4 exhibited lower levels of γ-H2AX, a biomarker for DNA damage, compared to cells without Klf4. Moreover, after DNA damage, cells expressing Klf4 exhibited increased levels of BRCA1 and Rad51, known tumor suppressor genes. Finally, genes involved in DNA damage response (DDR), ATR, and Chk1 were upregulated in cells containing functional KLF4, offering a possible mechanism for KLF4's role in mediating DDR. Our results indicate that KLF4 plays a crucial role in maintaining genetic stability by enhancing cell DDR, supporting previous findings that KLF4 functions as a tumor suppressor.