In breast cancer subgroup specific settings, significant correlations were found between caspase-3 and calpain-2 expression in the basal-like subgroup (r = 0.143, P = 0.045); caspase-3 and calpain-2 expression in the triple-negative subgroup (r = 0.194, P = 0.01); caspase-8 and calpain-9 (r = 0.25, P = 0.019), caspase-8 and calpastatin (r = 0.22, P = 0.009) in the HER2+ subgroup (Table 2) but, as before, are of marginal biological relevance due to the low r values. This evidence concerns the gene CAPN9 and breast cancer.