To investigate whether PC5-2 would bind to NSCLC cells, we used immunohistochemistry to locate the phage particles in different cell types. Our results showed that PC5-2 bound specifically to NSCLC cell lines including CL1-5 and PC13 (Fig. 1B, arrowheads) . The control helper phage did not bind to CL1-5 cells. PC5-2 bound neither to other cancer cell lines, including oral cancer (SAS) and nasopharyngeal carcinoma cells (NPC-TW01), nor to normal epithelial cells (NNM) from nasal mucosa (Fig. 1B) .