Because they grow faster than your control cultures and have more cells, more Formazan conversion, and thus signal, if your substance or condition increases cell proliferation, you will generally get over 100% values on those cultures. Values significantly over 100% will be evidence of significantly increased cell proliferation. It is a perfectly valid outcome of the MTT assay.
Dear Professor,
There may be an interfering effect of the test compound with the MTT reagent.
In such a case, you may test your candidate compound in a cell-free culture system. You may try adding the MTT compound to the test solution without cells and then incubate for 4 hours. If the absorbance value of the test compound is higher than the blank (which is the usual cell culture medium only + MTT), the effect of the test compound may be observed at the higher concentrations, it would clearly demonstrate the existence of interference of test compound with MTT reagent.
So, even though there would be cell death because of the effect of the test compound, it may still give rise to increase in viability due to the interfering (reducing) activity of the test compound with the MTT reagent.
Regards,
Malcolm Nobre
Hi Dr. Zunika Amit
I agree with Dr Anton Lennikov .
There are many compounds which show increase in the cell proliferation above the control cells. This increase in proliferation at the optimal drug concentration sometimes leads to increase in the cell number more than the control number. In this case you will observe the % cell viability of the treated cells above 100% which is quite common in many experiments. I have observed similar effects in compounds against highly proliferative cells such as RAW 264.7, N9 microglia, HMC-3 and many other cells.
Hope it helps,
Thanks,
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