These CTCs expressing IGFBP5 also had increased expression of stem cell associated genes aldehyde dehydrogenase 1A2 (ALDH1A2) and Kruppel-like factor 4 (Klf4) (66), which could indicate a cancer stem-like cell phenotype, a state thought to modulate the ability of cancer cells to seed new tumors. This evidence concerns the gene KLF4 and cancer.