In 10 seconds? Human Immunodeficiency Virus (HIV) is one of the most notorious cancer-causing viruses… which –weirdly– messes with our immune system and makes us more susceptible to other cancer-causing viruses.
What? HIV can make us more susceptible to cancer? Tell me more! Yes, unfortunately. HIV terrified the world in the 1980s when it was discovered to cause Acquired Immunodeficiency Syndrome (AIDS), which made those infected much more susceptible to a range of rare and deadly diseases… and cancers. In this Cancer Gone Viral digest, we are going to break down the mechanics of how that happens and the steps people with HIV can take to minimize their risk of cancer.
Listen to Sparrow's Senior Editor talking to the Expert about HIV and cancer risk. Click the player button above.
So, how does HIV cause cancer? HIV is a virus that can be transmitted sexually, by blood-to-blood contact, or from mother to child. Unlike viruses, such as Human Papilloma Virus (HPV), whose viral proteins are directly responsible for increasing a person’s risk for cancer, HIV messes with our immune system to increase cancer risk. HIV infects and kills important immune cells called helper T cells (AKA CD4+ T cells, close relatives of killer T cells) that strongly boost our immune system’s danger-fighting capacity, causing those who are infected with HIV to become immunocompromised (AKA having damaged immune systems).
And that opens the gates for cancer? Sort of! If you recall our Immunity vs. Cancer series, you’ll know that our immune system plays an important role in preventing cancer. Immunodeficiency (in this case, having no helper T cells) itself is not lethal, but nothing will make you realize how much your immune system works daily to protect us from diseases until it is damaged. And on that note, compared to the general population in the USA, people with HIV are more likely to develop certain cancers. And many types of cancers associated with HIV infection are cancers caused by other viruses because they have an enhanced ability to infect and wreak havoc in immunocompromised individuals.
For example? Well, people with HIV are about 500 times more likely to develop a cancer called Kaposi sarcoma (caused by a virus called Kaposi’s Sarcoma Herpes Virus), 12 times more likely to develop non-Hodgkin lymphoma (caused by a virus called Epstein-Barr Virus), and 3 times more likely to develop cervical cancer (caused by HPV).
But doesn’t the immune system protect against non-viral cancers as well? You’re absolutely right! So, on that note, in the US, people with HIV have a 19-fold greater risk of developing anal cancer and are twice as likely to develop lung and oral cancer. What's worse is people with HIV are also more likely to die from cancer than HIV-uninfected individuals. (A great moment to thank your helper T cells for all the work they do without us realizing it!)
Well, what about if individuals with HIV are being treated? Great question. The treatment for HIV is called combined antiretroviral therapy (cART), which is a mix of drugs that can help people with HIV rebound their immune systems and suppress HIV replication to such an extent that those successfully treated can no longer transmit the virus to others (although unfortunately because of the way HIV hides in our bodies it can’t cure their infection).
And how do antiretrovirals affect cancer in HIV+ people? Good news! A large study following about 450K people with HIV found that cancer risk was significantly lowered for multiple types of cancer after the introduction of cART in the mid-1990s. Even so, the risk was still elevated compared to the general population.
Why is the risk still elevated even though most people have access to treatment? Because many of those in this cohort were diagnosed with HIV before effective cART was available, it's thought that the increased risk may be due to the consequences of immunosuppression before they were treated. However, the data from this study can’t confirm this directly; since these treatments are relatively new and cancer often takes decades to develop, we must await further studies that can compare cancer rates among people with HIV who were diagnosed and treated early to those who were delayed in receiving cART treatment.
Prevention, prevention, prevention
Although the quest for a cure rages on in research institutions all over the world, prevention remains the best method for managing HIV-related cancer risk.
The CDC recommends HIV testing at least once for all adults and yearly testing for those at higher risk (including people who inject drugs, and who are sexually active). Regular testing can ensure that if you do become infected that you can start cART treatment as soon as possible and mitigate any potential long-term impacts of immunosuppression (like cancer)!
Once infected, it is also recommended that people make sure they are vaccinated against HPV (to prevent cervical and anal cancer), stop smoking (to prevent lung cancer) and refrain from injecting drugs (to prevent transmission of HCV which often leads to liver cancer) to keep themselves as healthy as possible for years to come!
Dr. Talia Henkle has distilled 2 research papers saving you 7 hours of reading time.