Interpretation of M30/M65 ratios

Death mode can be determined by measuring "M30" and "M65" values and by calculating a ratio. However, such experiments must be carefully controlled. CK18 is generally not completely cleaved by caspases during apoptosis. The extent of cleavage varies between different cell systems and can be as low as 20-25% after treatment with an apoptotic stimulus.

It is advised that epithelial/carcinoma cells are treated with an apoptotic agent (e.g. staurosporine) and a necrotic agent (e.g. H2O2) to provide reference values for the agent that is going to be tested.

Interpreting "M30/M65 ratios" in situations where no references can be established is difficult (i.e. in serum samples from patients) and ratios between caspase-cleaved to total CK18 must therefore be interpreted with caution.

IMPORTANT: it is not appropriate to interpret a ratio of "M30" to "M65" of 0.3 in a serum sample as 30% apoptosis and 70% necrosis. An almost total absence of caspase-cleaved CK18 (i.e. a ratio of < 5%) in a serum sample containing high levels of CK18 indicates a major component of necrotic cell death; ratios of > 20% indicate apoptosis.