Reader Comments

Post a new comment on this article

Praise, questions, and one criticism.

Posted by DCSweet on 11 Mar 2010 at 21:37 GMT

Your comprehensive study of the antiangiogenic effects of hyperforin and eight of its derivatives is admirable in the multiple types of evidence and replications you present in favor of tetrahydrohyperforin and octahydrohyperforin acting in vitro as antiangiogenic agents. I hope you continue your work, and that someone eventually moves on to primate safety studies of tetrahydrohyperforin and octahydrohyperforin at functional blood concentrations. In vivo functional studies for both compounds would also be easily facilitated through tumor-prone rat studies.

I'm sorry for dedicating so much space to my one criticism, because overall this looks like excellent and meaningful work, and I want that to be my main point.

I have a few questions for the authors. Please excuse any ignorance in these as I'm not an oncology researcher, nor have I done cell culture work. (I'm a neuroscientist who works mostly with rats.)

1) Is there a tissue type or bodily function that normally depends on intact angiogenesis, perhaps high turnover epithelial tissues (e.g., alimentary lumen), and what might be the expected side effects of shutting angiogenesis down systemically?

2) Is it the eventual goal of this type of research to completely shut down angiogenesis, or will partial inhibition suffice to prevent or sufficiently limit tumor growth?

3) In your cell migration study of octahydrohyperforin, you said it showed the same effect as hyperforin and tetrahydrohyperforin, but at half the concentration. However, in a previous section showing cell migration results for compounds 1-8, it was only compounds 3 and 6 that you say showed a clear effect. Am I to understand that octahydrohyperforin can only replicate the minuscule, if existent at all, effects of compounds 1 and 8, but at half the concentration? Of what value is that? Have I misunderstood something?

Finally I have a criticism concerning your cell migration study. Is it possible that the greater separation at t0 of sample 6 was related to its poorer migration? (Questions from my own ignorance: Is this migration cytokine-mediated, and therefore vulnerable to proximity differences related to the sharp drop-off in cytokine concentrations as distance increases from the cell? Or is the migration signal somehow contained completely within the medium?)

Your methods indicate you measured acellular surface (just "surface," not surface area or linear surface distance between cell fronts), but did not clarify what was measured or compared. If you measured and compared acellular surface area (2 dimensional, which reduces the observed impact of the migration velocity by factoring the meaningless dimension of length along the gap), the cell front closing velocity would be highly diluted. If you measured percent of linear gap closure, again, you'll dilute the results because initial gap distance is not standardized for all samples. In my opinion, the dependent variable needed to measure the effect of cell migration is the (single dimension) cell front closure velocity.

To my naked eye, it seems like the cell fronts for compound 6 moved toward each other, but the width of the original gap was so great that the cell front migration might have been masked by one of the factors I described above.

Taking a simple linear measurement of the average gap width (as it appears on my computer screen) from t0 and 4h on samples 1 and 6, the gap closure velocity, or cell front migration velocity, ([gap width at t0]-[gap width at 4h]) is nearly identical. Granted this is a crude method, it depends entirely on the magnification scales being equal between photos, and the quantification of these results is only valid as these figures appear on my computer screen, but it seems clear to me, using only these photos and a ruler, that the migration velocity of the advancing cell fronts were approximately the same for samples 1 and 6 (3.5 and 3.8 mm/4h on my computer screen, respectively).

In any case, it seems to me that sample 6 did not halt cell migration, nor did it slow it down as compared to hyperforin. For these reasons, I question the validity of your assertion that compound 6 inhibited migration.

I only compared samples 1 and 6 and found this apparent conflict. If your lab initially compared changes in acellular surface area to determine your results, perhaps your lab might find more meaningful data by comparing gap closure velocity (not closure percentage). Changes in acellular surface area introduce an unnecessary dimension and are highly vulnerable to differences in initial gap width.

Best wishes in your future work!

No competing interests declared.