Accumulating studies have demonstrated increased expression of the four Yamanaka factors OCT3/4, SOX2, KLF4, and c-MYC (collectively referred to as OSKM) in the CICs of various cancers, including glioma, lung cancer, prostate cancer, and bone sarcoma; and this upregulation is associated with a poor prognosis for cancer patients [14–16]. Here, KLF4 is linked to cancer.