Kaposi sarcoma virus and Merkel cell polyoma virus cause skin cancers. Here Py is the abbreviation of polyoma and MT is the abbreviation for middle T. They next turned their attention to cancer causing viruses, beginning with the polyoma virus. The polyoma middle T-antigen is taken from the polyoma virus. In human breast cancer the polyoma middle T- antigen was not found. There he started his studies about animal oncoviruses, especially of polyoma family. The polyoma virus affects tyrosine kinase activity inside the nuclear matrix. The virus was named the Stewart-Eddy or SE polyoma virus, after their respective surnames.