CD44 and urinary bladder cancer: Prevalently, cell sorting by flow cytometry and accumulation through specific culture condition were the main two methods for CIC isolation.38, 39 Cell sorting substantially depends on cell surface markers, cytokeratins, side populations and aldehyde dehydrogenase.40 Cell surface proteins such as CD44 and its variant CD44v6 was developed as potential markers for CICs and cytokeratin 5 were reported to have properties of CICs.41, 42 Side population separated from bladder cancer cells showed self-renewal and differentiation characters.