We detected the expression of Oct4 in progenitor epithelial cells. Oct4, a member of the POU family of transcription factors, is expressed in pluripotent stem cells such as embryonic stem cells, induced pluripotent stem cells, and lung stem cells where it regulates self-renewal and pluripotency [32, 33] . These Oct4 + colony cells also expressed other stem cell markers; SSEA-1, Ccsp and epithelial markers; pan-K, K-18, and occludin. Clara cells, airways progenitor cells in the lungs which have been involved in lung regeneration and repair, also express Ccsp and cytokeratins [14, 32, 34] . Importantly, these Oct4 + Ccsp + colony cells differentiated into cells possessing Aqua5 and SPC which are markers for type I and II like pneumocytes respectively. Expression of stem cell markers in progenitor epithelial cells may, therefore, be associated with differentiation potential of these cells.