Virus and Cancer : An Overview

Introduction

Viruses are small organisms, and many cannot be seen through a normal microscope. When a virus enters a living cell, it crosses the membrane and releases the genome to replicate itself. Some take over the living cell by inserting DNA or RNA into the living cell. The virus inserts itself into the host cells' proteins, replicating itself when the conditions are right. The virus's DNA or RNA affects the host cell's gene, which can lead to cancer.

How Can a Virus Disrupt Cell Behavior?

In addition to chemicals and radiation, which lead to cancer, the virus is another important source of mutation. Humans are more prone to many viral infections. Viruses are not similar to bacteria, even though both can cause infections. Viruses disrupt cell behavior in many ways; some are:

1. Mutations and damage to the living DNA are caused by inserting the virus genome into the DNA of the living cell. This can destroy significant regulatory genes.

2. The virus may have genes that destroy cell regulation. This is beneficial to the virus as it enhances the production of progeny, which may disrupt the host cell.

3. Some viruses may have altered gene versions from the previous host. As a result, these genes do not function properly, and when they enter the host cell, they cause dysregulation and cancerous growth.

Through their mutational behavior, viruses play an important role in cancer development in many animals and humans.

How Does Human Papillomavirus (HPV) Cause Cancer?

The human papillomavirus has more than 150 types, called papillomas. These viruses cause papilloma, which is called a wart. Certain types of this virus develop only on the skin, while others develop on mucus membranes like the mouth, throat, or vagina. All forms of HPV can spread through contact, whereas 40 types transmit from one person to another through sexual contact. Dozens of these virus types result in cancer. Infections caused by HPV viruses are very common, but cancer caused by these viruses is not. Those affected by the infection caused by this virus do not develop cancer, but long-term infection due to certain types of HPV virus may result in cancer.

HPV virus and cervical cancer: Cervical cancer is the most common cancer seen among women, and some types of HPV viruses are the main cause. The PAP test (Papanicolaou test) reveals pre-cancerous cells in the cervix that HPV infections may cause. If any are present, this pre-cancerous cell can be eliminated or destroyed, which prevents cancer from developing. Most individuals affected by cervical cancer show HPV infections. There is no proper treatment for a cervix infected with HPV, but a vaccine can prevent it. In cases where HPV causes the growth of abnormal cells, it can be eliminated by removal or destroyed.

HPV virus also plays a significant role in some cancers affecting:

1. Penis.

2. Anus.

3. Vaginal.

4. Vulva.

5. Mouth.

6. Throat.

Vaccine against HPV virus: Vaccines are available which prevent HPV infections in children and young adults. This vaccine prevents almost 90% of cancers caused by the HPV virus. This can be used only as a preventive measure and does not stop or treat the existing infection caused by the HPV virus.

How Does Epstein-Barr Virus (EBV) Cause Cancer?

EBV is a herpes virus known to cause the 'kissing disease.' EBV transmits from one person to another through sharing utensils, coughing, or sneezing. Compared with other herpes viruses, EBV is lifelong, even though affected people do not show symptoms after the initial few weeks. EBV infects the host cell and retains some WBCs (white blood cells) in the body. No proper treatment, medication, or vaccine exists to treat or prevent EBV infections, but these viruses do not cause serious problems.

EBV infections enhance the risk of:

1. Nasopharyngeal cancer.

2. Fast-growing lymphomas like Burkitt lymphomas.

3. Hodgkin lymphomas.

4. Stomach cancer.

How Do Hepatitis B Virus (HBV) And Hepatitis C Virus (HCV) Cause Cancer?

Both HBV and HCV cause liver infections. These cause long-term infections that may result in liver cancer. Long-term HCV infection can also result in non-Hodgkin's lymphoma. They get transmitted from one person to another, similar to the HIV (human immunodeficiency) virus, through needles, unprotected sex, childbirth, or blood transfusion.

HBV infection causes symptoms like flu or jaundice, and adults recover completely from this virus in a few months. However, the infection is prolonged in very few people, increasing cancer risk. At the same time, HCV infection causes fewer symptoms than HCV but results in prolonged infection, enhancing the risk of liver cancer. Once hepatitis B and C are diagnosed, the person is treated with medications; in severe and prolonged infections, they are treated with a combination of drugs that help get rid of HCV infections. In the case of HBV infections, there is no permanent cure, but medications can be used to reduce the risk of liver damage and liver cancer. In addition, a vaccine is available to prevent HBV infection, whereas no vaccine for HCV infection exists.

How Does Human Immunodeficiency Virus (HIV) Cause Cancer?

HIV causes acquired immunodeficiency syndrome and does not cause cancer directly, but infections caused by HIV enhance cancer risk. HIV attacks the T-cells, the helper cells, and weakens the immune system. This allows the HPV to thrive and may result in cancer. Some of the cancers associated with HIV are:

1. Kaposi sarcoma.

2. Cervical cancer.

3. Non-Hodgkin lymphomas.

4. Anal cancer.

5. Lung cancer.

6. Cancer of mouth or throat.

7. Liver cancer.

8. Skin cancer.

9. HIV infections take a long time to show symptoms, and there are no vaccines to prevent them.

How Does Human Herpesvirus 8 (HHV 8) Cause Cancer?

The HHV-8 virus is found in all Kaposi's sarcoma patients; the infection causes this virus to multiply in large numbers and live longer than it should. These, in the long run, change into cancerous cells. These viruses are transmitted through sex, blood transfusions, and saliva. This virus infection is lifelong but does not cause major problems in healthy people with good immune systems. HHV-8 has also been linked to some types of blood cancer.

How Does Human T-Lymphocytic Virus 1 (HTLV-1) Cause Cancer?

HTLV-1 is associated with lymphocytic leukemia and non-Hodgkin's lymphoma. The HTLV-1 virus is a retrovirus used for genetic code. To multiply, they should be converted to DNA. This DNA can become part of the chromosome of the infected human cell.

Conclusion

Viruses are small organisms that cause many diseases in humans. They cause infections by affecting the cell's genetic makeup and potentially leading them to become cancerous. However, not all viruses cause cancer. Instead, some increase the risk of cancer by suppressing the immune system. Some of these infections can be treated through medication and prevented through vaccines. In contrast, others cannot be eradicated but can reduce cancer risk through medication and treatment.