Final answer:
Oncogenic viruses are viral infections that can lead to tumors by influencing genes responsible for cell growth, and include well-known viruses like HPV and hepatitis B and C viruses.
Step-by-step explanation:
In relation to causes of cancer, oncogenic viruses are viral infections that can lead to tumors by introducing cancer-causing genes or by altering the normal expression of cellular genes. Oncogenic viruses can interfere with the normal regulation of the host cell cycle, either by introducing genes that stimulate unregulated cell growth (oncogenes) or by interfering with the expression of genes that inhibit cell growth. For example, cervical cancer is associated with human papillomavirus (HPV), liver cancer with hepatitis B virus, T-cell leukemia, and different types of lymphoma with other viruses.
It's crucial to understand that these viruses can be either DNA or RNA viruses. Some well-known oncogenic viruses include HPV, Epstein Barr Virus (EBV), human immunodeficiency virus (HIV), Hepatitis B and C viruses (HBV, HCV), and human herpes virus 8 (HHV-8). Their ability to cause cancer makes them a significant area of study in medical science, as they contribute to a considerable percentage of cancer cases worldwide.