Dear Gaurav,

You are perfectly right!

"Antiproliferative" and "cytotoxic" are used as synonymas while they are actually not!

When using a colorimetric assay (MTT, SRB, XTT, etx...) you cannot speak about "cytotoxicity" by only about "growth inhibitory effects" because a concentration that reduces by 50% the growth of your cell population of interest with your compounds of interest does not mean that 50% of the cells were killed. The possibility remains that indeed 50% of the cells were killed (cytotoxic effects), but also that 50% of the cells faced growth arrest (during the time of the test; cytostatic effects) or that 50% of the cells detached from the bottom of the flask (anti-adhesive (anti-metastatic?) effects), or a mix of these three biological processes.

You have to use the GI50, the LC50 and the TGI indices as validated by the US NCI (see their publicly available website) to make the difference between a cytotoxic (induced cell death) and a cytostatic (inducing "antiproliferative effects".

If you are using a colorimetric assay, simple observations with phase-contrast microscopy (that you are routinely used when you perform cell cultures) can more or less easily inform you about cytotoxic versus cytostatic effects.

You can also use vital dyes in addition to the colorimetric assay.

Hoping that it can be of help.

Robert

I agree with Robert's response and would like to add that, in general, when treatment of cancer cells with chemotherapeutic drugs results in cytotoxicity, it usually results in cell death (although the mechanisms may differ). However, when the treatment of cancer cells results in anti-proliferative action, it usually results in permanent cell cycle arrest and cellular senescence. Both effects have been documented in vitro and in vivo studies.

Cytotoxic means cell leads to death owing to severe stress while antiproliferation results for cell cycle arrest or delay and DNA degradations upto a level.