RB1 and neoplasm: The early region encodes viral proteins involved in replication and amplification of the viral DNA genome that are referred to as tumor antigens (T antigens) based on early studies that determined analogous viral proteins in SV40 and mouse polyomavirus were expressed in tumors arising in rodent species and facilitated tumorigenesis, in part, through the ability of LT to bind and inactivate the tumor suppressors, p53 and pRb [17,18].