Mitochondria as target to inhibit proliferation and induce apoptosis of cancer cells: the effects of doxycycline and gemcitabine, 2020, Dijk et al

[Hutan]

https://www.nature.com/articles/s41598-020-61381-9#Fig1

Doxycycline has anti-tumour effects in a range of tumour systems. The aims of this study were to define the role mitochondria play in this process and examine the potential of doxycycline in combination with gemcitabine. We studied the adenocarcinoma cell line A549, its mitochondrial DNA-less derivative A549 ρ° and cultured fibroblasts. Treatment with doxycycline for 5 days resulted in a decrease of mitochondrial-encoded proteins, respiration and membrane potential, and an increase of reactive oxygen species in A549 cells and fibroblasts, but fibroblasts were less affected. Doxycycline slowed proliferation of A549 cells by 35%. Cellular ATP levels did not change.

Doxycycline alone had no effect on apoptosis; however, in combination with gemcitabine given during the last 2 days of treatment, doxycycline increased caspase 9 and 3/7 activities, resulting in a further decrease of surviving A549 cells by 59% and of fibroblasts by 24% compared to gemcitabine treatment alone. A549 ρ° cells were not affected by doxycycline. Key effects of doxycycline observed in A549 cells, such as the decrease of mitochondrial-encoded proteins and surviving cells were also seen in the cancer cell lines COLO357 and HT29. Our results suggest that doxycycline suppresses cancer cell proliferation and primes cells for apoptosis by gemcitabine.

Open access

 

[Hutan]

I found this paper interesting because it found that doxycycline was knocking down the mitochondrial-encoded proteins, as other related antibiotics had been found to do.

Already in the 1980s, we investigated the potential anti-tumour properties of tetracyclines based on the notion that these antibiotics inhibit mitochondrial protein synthesis. Tetracyclines block bacterial protein synthesis by binding to the small ribosomal subunit, thus preventing the attachment of aminoacyl-tRNAs14. Since mitochondrial ribosomes are evolutionarily related to bacterial ribosomes, tetracyclines also interfere with mitochondrial protein synthesis

In the current in vitro study, we further examined the impact of doxycycline on cellular physiology to explain the in vivo observations. We compared the effects of doxycycline on the A549 human lung adenocarcinoma cell line and primary human dermal fibroblast. To confirm that the effects were indeed caused by inhibition of mitochondrial protein synthesis, we used the mtDNA-lacking A549 ρ° cell line as negative control.

Our experiments demonstrate that doxycycline-induced inhibition of mitochondrial protein synthesis decreases mitochondrial ATP generation, resulting in a slower proliferation rate of A549, COLO357 and HT29 cells. In addition, doxycycline treatment decreases the inner mitochondrial membrane potential (ΔΨm) and produces oxidative stress

Specifically, some of the proteins that are part of the electron transport chain are decreased:

Quantification of the signals of the co-migrating cytochrome-c oxidase subunits MTCO2 and MTCO3 from four independent experiments indicated that the synthesis of these polypeptides decreased by ~30% in doxycycline-treated fibroblasts and by ~50% in doxycycline-treated A549 cells, compared to vehicle-treated cells... In contrast to the diminished synthesis of most mtDNA-encoded polypeptides, the synthesis of the ATP synthase subunits MTATP6 and MTATP8 increased markedly in doxycycline-treated cells

My understanding of the following is that the cells can maintain ATP production levels so long as there is enough glucose. It makes me wonder how the cells would perform if put under stress, as is the case during exercise.

We found no difference in ATP levels in doxycycline-treated cells compared to vehicle-treated cells for any of the three cell types (Fig. 4). Addition of oligomycin A had no effect on ATP levels, implying that glycolysis is able to offset the loss of ATP production by oxidative phosphorylation under the high glucose culture conditions. On the other hand, addition of 2-deoxyglucose resulted in a fall of ATP levels, indicating that oxidative phosphorylation is not able to fully compensate the loss of glycolytic ATP production through oxidation of glutamine from the medium via the Krebs cycle37.

We found that ATP levels were not affected by doxycycline. We expect that cells will try to maintain their ATP levels and adjust their metabolic rate according to the ATP synthesis rate. Consequently, the decreased oxidative phosphorylation causes a deceased proliferation rate.

I thought it was relevant given the recent promotion of doxycycline as a treatment of ME/CFS. On the face of it, at least based on this paper, doxycycline treatment would seem to be exactly what you would not want to do, especially given recent findings suggesting that there are already lower levels of some ATP-production related proteins in people with ME/CFS. I know some people use tetracyclines for pain control - this paper might also suggest that that is not good for energy capacity in ME/CFS.

It also makes me wonder if repeated treatment with tetracycline-type antibiotics (as is the case for people taking doxycycline prophylactically for months against malaria) might somehow prime the body for ME/CFS (although this paper doesn't suggest a mechanism for any lasting action of the drug).

 

[duncan]

It also makes me wonder if repeated treatment with tetracycline-type antibiotics (as is the case for people taking doxycycline prophylactically for months against malaria) might somehow prime the body for ME/CFS (although this paper doesn't suggest a mechanism for any lasting action of the drug).

Lots of conflicting data out there. Lots. I seem to recall a 2011 or so study which suggested tetracyclines were helpful in some MS cases. But I don't recall if it was ever replicated.

And forget about Lyme disease.

I've eaten boatloads of doxy and mino. Distressing to think I may have paved the way for ME/CFS.

Who knows who to believe anymore?

 

[Simbindi]

I'm finding this discussion about doxycycline very interesting. I've been prescribed it a number of times for ongoing 1ung infections a1ong with ora1 steroids over the 1ast 18 months. The steroids were on1y prescribed because I have asthma, so each time my 1ung issues f1ared I've been given 10 days of steroids a1ong with 14 days of antibiotics.

Each time I'd start getting worse after the 10 day course of steroids finished and I was on the doxycyc1ine by itse1f. So ear1ier this year I decided I'd see what happens if I just take the ora1 steroids without the prescribed antibiotic. I did this without my GPs approva1 because the pattern was so obvious to me but my conversation with her about this was patronising and point1ess (she to1d me I had to take antibiotics with the ora1 steroids due to 'bugs being everywhere...').

Anyway, it turned out that the steroids a1one c1eared the puru1ent sputum and chronic breath1essness (it gets very severe, I can't even speak a sentence or stand up without fee1ing 1ike I'm drowning etc.). Unfortunate1y the improvement on1y 1asts for a few weeks when I finish the course though.

So then when I had the next f1are up I experimented with the doxycyc1ine course to see if they wou1d c1ear my 1ungs without the steroid medication. It turned out that it made my breathing even worse and a1so did not c1ear my 1ungs of the puru1ent sputum. When on it without the ora1 steroids I cou1d bare1y breathe, it got very scary. I improved a 1itt1e after stopping taking it.

So on her 1ast visit I to1d my GP about this and she was confused. Her response was that this is the antibiotic with the most 'evidence' for 1ung infections. I had to keep repeating that in my case it makes the condition worse.

I'm actua11y wondering whether I have a missed or misdiagnosis as I have a11 the symptoms of Myasthenia gravis and have in fact tried to convey severa1 of them to various GPs going back over 15 years. A few of the symptoms I noticed in the first coup1e of years of the ME.

On 1ooking up doxycyc1ine it's actua11y contra-indicated for Myasthenia gravis patients as it can make their condition worse.

When on Predniso1ene a1one it's 1ike a switch has been f1ipped in my body. I don't get PEM, I actua11y can remember what it's 1ike to have 'refreshing s1eep', my brain fog disappears, the rapid musc1e fatigabi1ity significant1y improves, I can ho1d my head up etc. (N.B. ora1 steroids are one of the fina1 medications given for Myasthenia gravis if the first stage ones don't work).

 

[duncan]

So on her 1ast visit I to1d my GP about this and she was confused. Her response was that this is the antibiotic with the most 'evidence' for 1ung infections. I had to keep repeating that in my case it makes the condition worse.

I have found that the math is not a neat math. It's more or less guilt or success by association.

My ire is pretty much directed at diagnostics, but I've plenty to go around. There's more than enough for clinicians and researchers who ascribe binary diagnoses to phantom culprits based on little more than a hunch and a primed ideology.

This study parses, and that's going in the right direction I think. I still wonder if micro-sleuthing medicine leaves broader-picture blind spots, though. Medicine should have a discipline dedicated to sewing together disparate patches of research. It's a reckless omission, one that affects boots on the ground.

 

[Simbindi]

I have found that the math is not a neat math. It's more or less guilt or success by association.

My ire is pretty much directed at diagnostics, but I've plenty to go around. There's more than enough for clinicians and researchers who ascribe binary diagnoses to phantom culprits based on little more than a hunch and a primed ideology.

I get that as a GP her know1edge and time are 1imited. What rea11y irks me is the impossibi1ity of getting GPs to even take a detai1ed c1inica1 history or record symptoms accurate1y, do appropriate b1ood tests and onward referra1s to any specia1ist. There's no interest in ensuring accurate diagnosis, much 1ess any c1inica1 curiosity when a patient isn't fitting into an obvious 'tick box'.