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Spoiler alert: As I start to write this, my intent is to delve into some basic science readers may find too detailed/complex and some speculation that has limited/no support and should NOT be taken as anything other than hypothesis generating. I fell in love with biology in about the 8th grade and with thinking about how to answer biology questions in medical school, so this is more self-indulgent writing rather than being written to inform.
Starting with the COVID-19 story, there have been so many excellent articles that if you haven’t read too many already, you can get a one minute overview from this video. Now for some more detailed science. This figure from an excellent article in Science shows the real details of how the virus works and some of the drugs that might be useful in stopping or slowing it down at the cellular level. If you use your best “Where’s Waldo” approach, (and if you are an avid follower of prostate cancer biology) you may find a very familiar protein hiding in the membrane where the virus binds to the exterior of the cell, TMPRSS2. This protein is an enzyme in the family of serine proteases, proteins that can cut peptide bonds at the site of the amino acid serine. Trypsin is another example of this category of enzymes we use in the lab to release cells from petri dishes, and you use various enzymes every day in your dishwasher to digest proteins stuck to your dishes. As shown in the figure, TMPRSS2 plays a crucial role in the entry of the SARS-CoV-2 virus into the respiratory epithelial cells leading to COVID-19 disease.
I first heard of TMPRSS2 several years ago in a lecture at the PCF annual scientific meeting. Investigators at the University of Michigan found that in a large percentage of prostate cancer, the androgen response elements in DNA that control the expression of TMPRSS2 have become fused to an oncogene, ERG. Every gene in our DNA is controlled by “upstream” segments of DNA called promoters or enhancers that regulate the expression of the gene. In the case of prostate cancer the androgen receptor, AR, binds to testosterone (or DHT) and then the is translocated to the nucleus where it binds to DNA at the sites of androgen response elements, leading to transcription and expression of the “downstream” genes. A reasonable analogy is to think of testosterone flipping a light switch to “on” and the AR being the wire going to the light bulb, TMPRSS2, in our case. You are familiar with this if you know about drugs like Lupron, Zytiga, or Xtandi that block testosterone signaling in various ways. Although taking any of these drugs turns off many genes related to prostate cancer development and progression, one of these genes is clearly ERG (if you have the TMPRSS2:ERG fusion), and of course you probably turn down expression of TMPRSS2 in normal cells.
So what does this have to do with COVID-19? As you may have seen, men have approximately twice the mortality of women from infection with SARS-CoV-2. There are no doubt many possible reasons. Men smoke more. Men may not practice social distancing as much. Men have more heart disease. But what if one reason is that they express higher levels of TMPRSS2 in their respiratory epithelium? The exact mechanism of TMPRSS2 in the infection can be found in this article. A cartoon from the article illustrates the several points in the viral infection cycle where TMPRSS2 (and other serine proteases) acts to facilitate the entry, replication and budding of the virion from a cell.
The article discusses several drugs that are being investigated to inhibit TMPRSS2 that could hopefully be effective in fighting COVID-19. One of them, camostat (seen in the first figure in this post), is already scheduled to begin clinical trial at the end of this month.
However, there is already a very interesting global “clinical trial” underway if you have followed the above (and necessarily complex …sorry!) story about TMPRSS2. If ADT, familiar to all men with metastatic or high risk prostate cancer, turns down the expression not only of ERG and other oncogenic pathways, but also the expression of TMPRSS2, it might reduce the infection rate or morbidity/mortality from COVID-19. Looking at large global databases, it may be possible to see whether men with a diagnosis of both “prostate cancer” and “COVID-19” can be extracted from the data, and then whether within this grouping, those men on ADT have a better outcome than those not on ADT. It would be complex, of course, since some of the men not on ADT might be on chemotherapy, or more sick in general, and thus more susceptible to dying from the infection. It might also be possible to see what the expression levels of TMPRSS2 in the pulmonary epithelium of men versus women are as a potential partial explanation of the differences in mortality. Finally, and this would be the most intriguing possibility of all, a clinical trial that combined some partially effective “drug X” from the list of drugs in the first figure with or without ADT could determine whether short term use of ADT could enhance the treatment. Proof that no one ever has a “unique” idea (and of the speed with which you can share ideas in today’s internet environment), in doing a minimal amount of literature research on this topic, I came across a preprint of a beautiful article looking at exactly the hypotheses I laid out above. It was submitted only 5 days ago! The authors have found very significant differences in the levels of expression of TMPRSS2 among adults using published databases and hypothesize that this could explain why some individuals may be more susceptible to bad outcomes. They also evaluate the potential of down regulation of the gene with ADT drugs like enzalutamide or estrogens and they conclude, “Together, these results identify existing drug compounds that can potentially be repurposed to transcriptionally inhibit TMPRSS2 expression, and suggest that the activation of estrogen pathways or inhibition of androgen pathways can be a promising modality for clinical intervention in SARS-CoV-2 infection.”
In summary, if you have prostate cancer and are on ADT, the well known side effects you put up with are unpleasant to say the least. But there is a “not-zero” possibility that your ADT is also protecting you. The best advice is still to practice social distancing, wash your hands, and be vigilant regarding your health, but maybe there is a silver lining in this story. I hope so, and there are already clinical and basic scientists exploring the hypotheses discussed above. Be well and my best wishes during these trying times!
10 responses to “COVID-19, ADT and Prostate Cancer”
Can you put this into a more simple report?
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Thank you for being on top of this. I have been reading that men are more likely to succumb to the virus than woman and I was wondering if testosterone was a food for the virus. This article seems to support this, so I would hope you continue to follow testing in this area and support further testing in this area
Here’s a try: The virus needs host machinery to enter cells. One of those machines is an enzyme, tmprss2. It so happens that this machine is controlled by testosterone which might be considered the gas pedal for how fast the machine runs. When that gas pedal gets attached to a cancer gene (which often happens in prostate cancer), it drives the machine to cause cancer. (which is why I had heard of tmprss2 in the first place – prostate cancer is caused in part by the gas pedal being attached to ERG, a cancer causing gene). But… normally, the gas pedal causes the machine to just make tmprss2. That would be irrelevant if it wasn’t for the chance thet the virus learned how to get into cells by attaching to tmprss2. Now if you take your foot off the gas, less tmprss2 and maybe less virus entry/infection. We know we can take the foot off the gas in prostate cancer by stopping testosterone (the foot). So it makes sense that in normal situation (like your normal lung) if you take foot off the gas, less tmprss2, the viral attachment sites. Hence, hopefully, less infection.
I suspect that’s still pretty complicated, but hope it helps
For what it’s worth, my case was over in about 36 hours. My testosterone is always low 130 with free of 11.
Mike Thank you for sending me your excellent article. Caren and I are self isolated. We are expecting our first grandchild anyday. Blessings, Heinie
Interesting info on TMPRSS2. I am on abiraterone acetate (Zytiga) so the fact that my T is being suppressed means that the AR pathway blockage you mentioned is present in me. It would cool to know if intend to follow up this linkage to SARS-CoV2 resistance. Thanks for article.
It will take large databases to determine if it worked/works – probably a month or two. I’ve heard from several colleagues that are working on the idea which is great. Apparently there was talk of this re influenza as long as 10 year ago or so.
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