Hi,

I have been treated oral cancer cell lines with DEAB as a broad spectrum ALDH inhibitor. I assay for ALDH activity using an absorbance based assay for NADH at 340nm. I found that optimal inhibition is 12 h following addition of the drug, and this inhibition is no longer present 24 h following treatment.

I tried re-dosing the cells at 12 h for an *additional* 12 h to try sustain inhibition/extend the length of time ALDH activity is inhibited. However, this method of adding more DEAB halfway through does not reach the same level of inhibition. It increases inhibition compared to leaving the cells for 24 h, but it appears that the efficiency of DEAB lessens over time.

What would explain this 'exhaustion' of DEAB as such? I know its considered a slow substrate/reversible inhibitor depending on the ALDH isoform but unless other isoforms are upregulated over the 24 h to compensate for inhibition? How is the drug becoming less efficient?

Thanks in advance,

Isabel