One in five malignant cancers in humans is directly linked to microbial infections caused by bacteria, parasites, and viruses. Why?, one might wonder. What do microbes have to do with cancer development?
Bacteria’s Role in Cancer Development
Certain bacteria can produce toxins, enzymes, and other molecules that alter normal cellular functions, interfere with cell cycle control, and disrupt the host’s immune response. This contributes to cancer’s appearance and progression. For instance, 89% of all gastric cancers are attributed to infection by the bacterium Helicobacter pylori, and eradicating this infection reduces the tumor’s incidence.
Viruses and Cancer: A Dangerous Partnership
Viruses can insert their genetic material into host cells, causing uncontrolled cell growth and chronic inflammation that damages DNA and promotes cancer development. Examples include oncogenic viruses like human herpesvirus 8 (VHH-8), Merkel cell polyomavirus (MCPyV), human T-cell leukemia virus type 1 (HTLV-1), Epstein-Barr virus (EBV), hepatitis B virus (VHB), hepatitis C virus (VHC), and human papillomavirus (HPV).
Sarcoma of Kaposi and Herpes
Human herpesvirus 8 (VHH-8) is the primary cause of Kaposi’s sarcoma, affecting skin, lymph nodes, oral mucosa, nose, and throat, as well as other body tissues. Transmission through saliva and genital secretions appears to be the main route of infection.
Individuals with compromised immune systems have a higher risk of developing VHH-8 associated diseases. Unprotected sex increases the likelihood of contracting the virus.
When Changes in Moles or Growths Signal Trouble
Merkel cell polyomavirus (MCPyV) has been linked to Merkel cell carcinoma, a rare and aggressive skin cancer. In recent years, the incidence of this condition has significantly increased.
Primary tumor sites for Merkel cell carcinoma are the face, head, and neck, followed by upper limbs and shoulders. Effective preventive measures include reducing sun exposure, avoiding peak UV radiation hours, and using sunscreen.
Early detection is crucial for successful treatment, so consult a doctor if any changes in mole size, shape, or color are noticed.
A Virus Causing Leukemias
Human T-cell leukemia virus type 1 (HTLV-1) is the first described human retrovirus and the causative agent of adult T-cell leukemia, a severe form of cancer. Lymphoma/leukemia of T cells, which can be considered either a lymphoma or an acute lymphocytic leukemia, accounts for 1% of all lymphomas and is more common in adolescents or young adults.
Individuals diagnosed with HTLV-1 infection should know that it’s a lifelong condition and they should not donate blood, semen, or other tissues. Mandatory HTLV-1 antibody testing for all blood donations has been implemented in 23 countries.
Cancer Following Mononucleosis
Epstein-Barr virus (EBV) causes infectious mononucleosis and is associated with various cancers, including Burkitt’s lymphoma, Hodgkin’s lymphoma, and nasopharyngeal carcinoma, among others. Although most of the population is infected with EBV, only a small fraction develops tumors related to it.
Recent research suggests that exposure to agents like tobacco, pollutants, food chemicals, and pesticides might be involved in EBV-associated cancers.
From Hepatitis to Liver Cancer
Hepatitis B (VHB) and C (VHC) viruses cause chronic hepatitis, liver inflammation that can lead to cirrhosis and eventually liver cancer (hepatocellular carcinoma). VHB infection is the leading risk factor for hepatocellular carcinoma, accounting for 50% of cases. VHB vaccination and hepatitis C treatment are crucial for preventing this cancer.
Estimates suggest that the HBV vaccine will prevent 38 million deaths among people born between 2000 and 2030 in 98 low- to middle-income countries.
If you have hepatitis B, maintaining a healthy lifestyle is essential to prevent the worsening of the disease. This includes avoiding alcohol and drugs, getting enough sleep, eating a balanced diet rich in fruits and vegetables, and exercising regularly.
Regular medical check-ups are also important to monitor the virus and liver health, follow specialist recommendations, and consult a doctor before taking any over-the-counter medication.
Human Papillomavirus and 5% of Cancers
Human papillomavirus (HPV) is associated with almost all cervical cancer cases. It’s also responsible for most anal, penile, vulvar, vaginal, and a significant proportion of oral and throat cancers. According to the World Health Organization (WHO), around 5% of cancers are caused by HPV infections.
HPV vaccination is one of the most important and effective strategies to reduce the incidence of various cancers and genital warts. Numerous studies have shown that this immunization has up to 95% efficacy in preventing HPV-related precancerous cervical lesions. The recommended vaccination schedule is two doses with a minimum interval of 5-6 months starting at age 12.
Fortunately, researchers from Mass General Brigham (US) have developed HPV-DeepSeek, an innovative and experimental blood test using artificial intelligence and complete HPV genome sequencing to detect HPV-associated head and neck cancer up to a decade before symptoms appear. This test, still in the experimental phase, promises to improve patient prognosis by enabling earlier, less invasive treatment.
Understanding the role, transmission methods, and mechanisms of oncogenic viruses is crucial for establishing preventive measures that reduce the social, economic, and health impacts caused by these pathogens.
