I am currently doing MTT assay on MDA-MB 231s and I treat the cells with 0.2% of DMSO (vehicle control). the problem is that the DMSO seems to increase cell viability (above 100% as compared to my untreated cells). I have done this assays a number of times and I keep getting the same results. I encountered the same problem previously when I was using CasKi cervical cancer cells. What could be the reason for this and how can i fix it. please help!
DMSO concentration in your experiment was too much. Less of 0.1%DMSO did not inhibite cell growth.
MTT is based on a metabolic activity measurement of the cells that we extrapolate (in my opinion, incorrectly), to cell viability. It is possible DMSO induces a nasal change on the metabolism of the cells, and thereby you see even more activity.
I would follow one of these strategies:
1) Normalize the result of the assay of your treatment directly to vehicle (DMSO) treated cells.
2) Check other parameters related to proliferation and cell survival: count cells using Tripan Blue or perform a quick FACS using Annexin or just Dapi to measure apoptosis or cell death. Think MTT assay sometimes gives you a wrong message: if ur cells do not die but proliferate less or more, you will also observe s difference in the colorimetric assay.
3) try to concentrate more your drug in DMSO and try 0.15% or below.
Good luck!
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