Final answer:
Oncogenic viruses can cause cancer by interfering with cell regulation, while oncolytic viruses can be used to target and kill cancer cells.
Step-by-step explanation:
Oncogenic viruses are viruses that have the ability to cause cancer. They interfere with the normal regulation of the host cell cycle by introducing genes that stimulate unregulated cell growth (oncogenes) or by interfering with the expression of genes that inhibit cell growth. Examples of cancers associated with viral infections include cervical cancer caused by human papillomavirus (HPV), liver cancer caused by hepatitis B virus, and T-cell leukemia.
On the other hand, there are also viruses that can be harnessed for cancer treatment. Oncolytic viruses are engineered to specifically attack and kill cancer cells. For example, reoviruses can infect and kill cells with an activated Ras-signaling pathway, which is a common mutation in cancerous cells. Modified viruses like rubeola and herpesvirus can also be used to aggressively attack tumor cells.