Human papillomavirus cancer research. Fluorescence light micrograph of a cell transfected with the HPV-16 E5 oncoprotein. Infection with certain types of human papillomavirus (HPV) is associated with various cancers. Research in this area is aimed at understanding the processes by which HPV can transform a healthy cell into a cancerous one. Here, the colours represent E5 (red), karypherin-beta-3 (green), and co-localization of both proteins (yellow). The E5-transfected cell (green) is demonstrated at top. The circular dark objects are cell nuclei. The cell used in this study is a COS cell, is a fibroblast-like cell line derived from monkey kidney tissue.