As TRAIL-induced cancer cell apoptosis could mediate by either caspase cascade pathway or mitochondria pathway [15], firstly we checked the change of cascade pathway, and we found that the levels of activation forms of apoptotic-related proteins, cleaved caspase 8, and cleaved caspase 3, were all increased in MSC-sTRAIL- or rhTRAIL- treated Nalm-6 cells, compared with control or MSC-EV group (Figure 3C). Here, CASP8 is linked to cancer.