CASP8 and fibrosarcoma: Our model was based on perturbation-response approach utilizing first-order response equations (1, 22–29), which was shown to successfully simulate the temporal experimental profiles IκB, JNK, p38, caspase-8 and -3 in wildtype, and four (FADD, RIP1, TRAF2, and caspase-8) knock-down (KD) conditions for human fibrosarcoma (30).