For example, studies show that small cell lung carcinoma cells, which are more prone to spontaneous apoptosis, are deficient in mRNA expression of extrinsic pro-caspases-1, -4, -8, and -10 [52] but no differences were observed between NSCLC and SCLC after examining the expression of intrinsic pro-caspases-2, -3, -6, -7, -9 [55]. Here, CASP2 is linked to small cell lung carcinoma.