KLF4 and prostate cancer: Interestingly, KLF4 has been reported as a direct target of the NF-kappaB/p65, as the Toll-like Receptor 9 (TLR9) signaling was shown to be essential for propagation and self-renewal characteristics of prostate cancer cells, and could induce the transcription factors NF-kappaB/RELA and STAT3 to co-regulate KLF4 and NKX3.1 gene expression by directly binding to their promoters21.