Final answer:
Cancer can be caused by viruses when they carry oncogenes or interfere with tumor suppressor genes. Hepatitis C and HPV are examples of oncogenic viruses associated with liver and cervical cancer, respectively. Viruses influence cell growth regulation, leading to uncontrolled proliferation and cancer.
Step-by-step explanation:
Two mechanisms by which viruses can cause cancer are as follows:
- The virus carries genes that stimulate unregulated cell growth, known as oncogenes, which can lead to cancer.
- Viral proteins interfere with the expression of genes that inhibit cell growth, leading to cancer.
Oncogenic viruses can be either DNA or RNA viruses and are linked to cancers such as cervical cancer (HPV), liver cancer (hepatitis B virus), T-cell leukemia, and various types of lymphoma. For instance, the hepatitis C virus (HCV) functions as an oncogenic virus capable of causing liver cancer. HCV carries genetic material that either disrupts normal cell cycle regulation by introducing oncogenes or impairs genes that would normally inhibit cell growth.
Viral mechanisms of inducing cancer are complex as they can involve the direct introduction of oncogenes by acutely transforming viruses or the insertion of viral genome near proto-oncogenes by slowly-transforming viruses. The latter results in long tumor latency as the viral integration is not always near oncogene regions. Regardless, both mechanisms ultimately promote uncontrolled cell proliferation and tumor growth.