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I was asked for my thoughts on a new paper by Seralini: Cytotoxicity on human cells of Cry1Ab and Cry1Ac Bt insecticidal toxins alone or with a glyphosate-based herbicide. I don't have the patience right now to turn my results into a blog post, so here are my thoughts as I posted them on Facebook:

Well, first thing that pops up is the fact that Dr. Séralini is funded by an anti-biotech organization (Greenpeace). So, there's that. He's also had some sketchy articles in the past that had, to be blunt, huge statistical mistakes and poor conclusions based on those mistakes (we've talked about some of this on Biofortified). This makes me question his ability to do sound science more than his potential bias due to funding. While any paper must be judged on its own merits, the frame of the authors (the PI in this case) does matter.

I was able to find a free PDF of the paper here:

Hm, the citations are a little suspicious. Most are of Seralini himself, and I notice a few others that have problems (like Rosi-Marshall).

Hm. They cite a Paul 2010, saying digestion is never a complete process and insecticide toxins cannot be fully degraded in vivo" but the abstract of the paper says "The results of the present study indicate that the recombinant Cry1Ab protein from MON810 is increasingly degraded into a small fragment during dairy cow digestion." These two are not the same thing. Hm. Other papers have shown digestion as well.

So, I've read the whole thing. Here's my conclusion:

I agree with their general idea that it's not scientific to call all Bt the same (this is not something I've ever disputed). The truncated and/or modified proteins do have differing toxicity levels with respect to target insects so it stands to reason that they may have different toxicity levels for non-target organisms or other different properties.

It may be appropriate to test pure protein as done in this study, but I believe it is more valuable to test a transgenic protein in the transgenic plant material or at least to extract the protein from the plant rather than producing in bacteria. Producing the protein in bacteria then trypsinizing may not give the same product as is found in the plant. They didn't sequence the protein to see if is the same as what is produced in a plant with a given construct. So, they may have tested something that didn't exist. We don't know if the protein they have is similar enough to the protein produced in plants to say that this study can be applied to biotech plants.

It may also be appropriate to test the Bt protein in combination with various pesticides that are expected to be used on a given Bt crop. Although, I do question the value in testing a pesticides at LC50 rather than at a realistic exposure level, such as the estimated residue at x time after spraying.

Feeding studies have been and are done for Bt crops. These studies compare plants expressing Bt to isogenic (genetically similar) plants without Bt. The companies do it before releasing the products to the market as part of deregulation risk assessment and independent scientists do additional feeding studies. Many of these studies are done in a "real world" environment or as much as possible for a controlled study. One of my favorites is this one with Mon810 that has the Cry1Ab protein:

Are these whole animal studies more or less valuable than a petri dish study? They are different, and tell us different things. The petri dish studies can only give us a hint of what will happen in a whole organism, and this study complicates the in vitro aspect even more by not using the actual plant-produced protein.

There have not been many in vitro studies of Bt toxicity. One that I found that was not cited by Seralini (that should have been included, in my opinion) used sheep rumen epithelial cells (known to be a good indicator for what will happen in vivo and found that even high concentrations of Cry1Ab didn't have an effect on the cells I do feel that this study has a flawed literature review, which concerns me greatly. If the authors don't have a firm grasp of the literature, and instead cite papers that are known to be flawed, what does that say about their ability to do good science?

I'm also worried about the sentence "the experiments were repeated at least three times" in the methods. Did they keep doing it until they got the results they wanted? Regardless, for the Bt only part, the experiment showed that the only significant difference was for the highest concentration of Bt, a concentration that wouldn't be found in the real world. The 10 ppm concentration had no difference from the control.

For the Bt+Roundup part, I won't even make conclusions because as I said earlier, that concentration isn't realistic.

Hm. Maybe I should turn all of this research into a blog post. I wish I had more time :( I spent way too long looking at this, although it was interesting.

Probably more than you wanted, but here you go! :)
Anastasia Bodnar's profile photoJeff Seale's profile photoMary Mangan's profile photoDavid Tribe's profile photo
+Mary Mangan provided a little more info. Here's my interpretation.

Human cells need serum in cell culture experiments. There are times when it's appropriate to use serum free media (I used serum free when testing iron bioavailability of maize because serum has iron) but in most cases serum needs to be in there or the cells get funky and any results are suspect (see: Seralni explains this away by saying that serum delayed cell necrosis, but if the cells died sooner, that sort of proves that removal of serum did bad things to the cells, doesn't it? Hm. Lots to think about.
Yeah--serum starvation can be a technique that's appropriate sometimes. But in this case--he claimed he was using these HEK293s because they were so like a kidney. Well, a kidney has fact, that's sorta how it works.

But still, say the serum starvation doesn't destabilize these cells and make them more susceptible to dumping huge volumes of protein on them: are the levels here even in the ballpark of that other paper that claimed to detect proteins in human serum? I'm sure someone will check on that, I didn't have a chance to.
Also too: First of all, we confirmed that the buffer was not cytototoxic for the cells. Ok, you know how to make buffer. But how come there's no control protein (not Bt) used for any of the data I can see? Give me albumin. Give me some corn protein. What does it look like if you dump huge amounts of plain old protein on starved cells?
Yeah--so even at the barely detectable (and questionable at that) level--this isn't even in the same ballpark. (I knew someone would do that calculation!) Thanks.
You may not post here often but wow! When you do you certainly help me grow my vocabulary & understanding of science. Thanks!
Happy to help, Janice! I was trying to avoid getting on yet another social media site but the advantages of a public forum with unlimited post size is too tempting. Plus I know a lot of you guys post on here a lot and I want to learn what you have to say :)

Karl - I am glad he asked but I hope my answer wasn't too know it all scientisty, if that makes sense.
If a Bt toxin that kills Spodoptera does not kill a Spodoptera-derived cell line (sf9), then how am I supposed to interpret the treatment of a human cell line with a Bt toxin? What about the converse - a Bt toxin that does not kill Spodoptera, but does kill an sf9 cell culture?
+Jeff Seale : did you try 67,000 times the usual level? I don't think you tried hard enough :)
+Anastasia Bodnar Re your comment about Mesnages claim that Bt is resistant to complete degradation , This is the final sentence in the paper they cite Paul 2010: "In comparison with total protein in feed, the relative amount of Cry1Ab protein in feces is markedly reduced indicating that Cry1Ab protein is not more stable than other proteins in the feed." Quite different from Seralini's representation
There is another point further confirming that removal of serum from the medium is making the cells sensitive to stress. This is in figure 2B. Here it can be seen that the addition of both Bt proteins PROTECTS the cells against killing triggered by Roundup (most likely the detergent in the Roundup). This is the opposite to a toxic effect. As you guys already pointed out they had noticed this with serum in other studies with this in vivo system
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