Lymphoma ... a sexually transmitted disease?

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Twice in the last month I've been asked if lymphoma could be passed through sexual contact, or even kissing. I worked hard to make sure that my quick answer—"No"—was correct. It wasn't.

Really? Is lymphoma an STD that can be transmitted through unprotected sex?

The hopelessly unsatisfying short answer is … you should know better, in cancer there are no short answers.

The longer answer is … yeah, kind of. To wit, three terms: Sexually Transmitted and Disease.

- Check off the D because lymphoma is one.
- Check off the T because a select few transferable creepy-crawlies exist that cause the D.
- And check off the S, because by way of unprotected S we T these D-causing microorganisms to one another.

COOTIES CANCER

The most recent estimate I've seen claimed that about 20 percent of all cancers are caused by the infection of some pathogen—either a virus or bacterium. Evolutionary biologist Paul Ewald thinks that by mid-century that figure will be as high as 95 percent.

We're not accustomed to thinking of cancer in terms of an infection, like we do the common cold, but we may have to start getting used to it. After all, a number of cancers have been pretty securely linked to a pathogen:

Cervical, laryngeal, anal cancers <> Human Pamplinovirus (HPV)
Liver cancer <> Hepatitis B virus (HBV)
Kaposi's sarcoma <> Human herpesvirus 8 (HHV8)
Mucosa-associated lymphoid tissue (MALT) lymphoma <> Helicobacter pylori bacterium
B-cell lymphomas (DLBCL, Burkitt's)<> Human immunodeficiency virus (HIV)
Primary CNS lymphoma <> Epstein-Barr Virus (human herpesvirus 4)
Adult T-cell Leukemia/Lymphoma <> Human T-cell Lymphotrophic Virus-1 (HTLV-1)

However, the only one that matters to this discussion is the last one. Sexual contact is one of the chief modes of transmission [1] for HTLV-1, a retrovirus believed to be responsible for Adult T-cell Leukemia/Lymphoma (ATLL), a super-rare form of highly aggressive lymphoma. In one of cancer’s many euphemisms, ATLL has a 'poor clinical outcome' [2]. In short, it’s deadly.

HTLV-1

Human T-cell Lymphotropic Virus-1 (there are four known HTLVs) is a retrovirus, which means that if the cell were a nightclub, a retrovirus uses its cellular connections to get into the genome through the back door, where it inserts its own fatalistic RNA into the existing DNA.

Retrovirus
Retrovirus by ~Velica on deviantART

The HTLV-1 retrovirus sneaks into your cell and edits the enormous code that defines how your body works. This minor edit has massive and paradoxical consequences: It instructs your DNA to start making T-cells with abandon. It's like sneaking into the National Archives and adding a few lines to the original draft of the US Constitution; tweaked and bizarre, the ensuing operation throws an otherwise functional system into terminal chaos.

VIRUS VS TUMOR

The paradox is that this instruction amounts to suicide for the retrovirus, right?

No, no, no. Solid tumors are self-defeating and stupid. They have all the foresight, patience and good sense of a hungry child sat square in front of his birthday cake. Devour—at an unsightly clip—is the name of its game. An hour later the kid's rolled up on the floor moaning about how he doesn't feel so good.

A virus is much smarter; a virus actually thinks about its legacy, about tomorrow, about generations from now. Not for nothing does HIV often have a long incubation period—where's the good in killing you right away? That's tumor mentality. The virus would rather rely on the irresistible nature of sex to ensure its legacy. It's counting on you to get laid, and often.

Although the National Cancer Institute is looking for ties between cancer and pathogens such as HTLV-1 and bacterium like Chlamydia pneumoniae, ATLL— as a result of HTLV-1 infection— is exceptionally rare in the US. Much of the significant research comes from Japan, where the concentration of infection is higher [3].

The good news is that ATLL doesn’t have the word ‘Adult’ in its name for nothing: According to a major source for this blog, HTLV-1 has a latency period of as long as 50 years [4]. Not only that, but only a small fraction of the people infected with HTLV-1 will even develop ATLL [5].

REPRISE: LYMPHOMA … AS AN STD?

So the REAL answer to the original question is that at least one subtype of non-Hodgkin's lymphoma can be transmitted sexually, but that it's really rare. Another reason to practice safe sex, as if we didn't already have plenty.

To draw the subject out further, you could even argue that primary central nervous system lymphoma (PCNSL) is an STD because it's been linked to the Epstein-Barr Virus (EBV), aka human herpesvirus 4 aka the cause of infectious mononucleosis aka the kissing disease. But EBV's implications are another story for another time.

GOOD NEWS ADDENDUM

Although some scientists don't even consider a retrovirus to be a living organism, it is currently smarter than all of us. But it's had hundreds of millions of years to evolve. It knows this game in and out—and that may be its downfall.

In gene therapy, scientists hitchhike their way into the genome by catching a ride with a retrovirus; once inside, they deliver therapeutic modifications to the genome. If the retrovirus can rewrite DNA by inserting its own code into the cell, why shouldn't we be able to rewrite that code too? And what more fitting or ironic way to do it than by mooching a lift with an oblivious retrovirus?

The sheer audacity of abusing retroviruses as treatment delivery vehicles against cancer is the kind of incongruity that I find thrilling. It bears little impact on the day-to-day life of most cancer patients, but it will almost surely have some role to play in the future of successful cancer treatments.

By Ross Bonander


Sources:
[1] Murphy EL, Hanchard B, Figueroa JP, et al. Modeling the risk of adult T-cell leukemia/lymphoma in persons infected with human T-lymphotropic virus type I. Int/ Cancer 1989;43:250-253.


[2] Suzumiya J et al. The International Prognostic Index predicts outcome in aggressive adult T-cell leukemia/lymphoma: analysis of 126 patients from the International Peripheral T-Cell Lymphoma Project. Annals of Oncology, 2009;20(4):715-21.


[3] Proietti FA, Carneiro-Proietti AB, Catalan-Soares BC, Murphy EL. Global epidemiology of HTLV-I infection and associated diseases. Oncogene. Sep 5 2005;24(39):6058-68.


[4] Szczypinska EM et al, Human T-Cell Lymphotrophic Viruses.


[5] Epidemiologic Notes and Reports Adult T-Cell Leukemia/Lymphoma Associated with Human T-Lymphotrophic Virus Type I Infection—North Carolina. MMWR Weekly. 1987;36(49);804-6, 812.

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