In the literature, there are numerous very high values. However, sometimes the duration of incubation is not mentioned. Thus, I have problems in comparing our values with the literature.
TMZ IC50 for U251 (72 hours ~ 200uM) and for U87 (72 hours ~950uM)
TMZ IC50 for U251 (72 hours ~ 200uM) and for U87 (72 hours ~950uM)
Dear Pawel,
thanks very much !!! This is in the range of what I found in the literature, so it is right that these values are really that high. Perfect,
best, Niels
Dear Pawel,
can you provide the papers where you found these values?
THANXXX A LOT!
Best, Niels
Hi, so using those values (nearly as high as 1mM), were you able to get a good result?
Hi, we slowly start to get results. It is somehow difficult to get the assay (XTT) reproducible. It is astonishing: in scientific literature, we find values ranging from app. 10 µM up to 1000µM. Now we systematically investigate what this might be due to. Do you have experience in this? Or do you know, why these extremely diverging values seem to be normal in scientific literature?
Hi Niels,
I have been working with U87 cells and using MTT assays to determine metabolic activity after incubations with a novel class of compounds but not temozolomide.
You may wish to refer to these publications for the metabolic activity of U87 treated with temozolomide:
Baer J 1993 Br J Cancer 67,6 p1299
Beier D 2008 Cancer Res 68,14 p5706.
Goodluck!
Ray
Sang Y. Lee did a review ( doi: 10.1016/j.gendis.2016.04.007 ) of reported TMZ IC50s in GBM cell lines, as well as those with experimentally acquired TMZ resistance.
Oddly, her review appears to consider U87 to be a "well-known TMZ sensitive" line, along with A172, U251 (and U373), despite reports of IC50s being all over the map. T98G on the other hand, appears to universally resist extremely high concentrations of TMZ. Torsvik et al. (doi 10.1002/cam4.219 ) suggest that only the low passage U251 cultures maintain a DNA copy number "resembling a typical GBM profile". They also note (as does ATCC) that most "U373" samples at cell banks were in fact contaminated/taken over by U251.
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