Figure 4.

Co-cultivation showed increased cell death and suppression of AKT signal pathway of colorectal cancer cells under ionising irradiation. (A) Ionising irradiation could induce TNFα and IFN5 secretion by MSC in the co-cultivated system. (B) Colorectal cancer cell ERK and AKT signalling pathways were suppressed in the co-cultivated system, meanwhile, cleaved caspase 3, and p-Stat3 in CRC cells were activated in CRC+MSC co-culture group. (C) The same number of 3D spheroids (CRC cells and CRC cells+MSCs) were transferred into an ultra-low attachment plate and treated with 10 J cm⁻² irradiation for 1 h in every 6 h. Dark cores (red arrow), which were reported to be dead cells, could be observed in the co-culture group. Tumour organoids were co-cultivated with or without MSCs, the volumes of tumour organoids turned to be smaller in the cocultivation group (f, a single layer of MSC was seeded below the Matrigel layer) compared with CRC without MSCs feeding after irradiation. (D) To further confirm the cytotoxicity effect of MSC under irradiation, PI staining was performed on two co-culture models (direct CRC cells-MSCs contact and indirect co-cultivation), as well as colorectal cancer spheroids. the co-cultivation group, both direct co-cultivation and indirect co-cultivation showed more dead cells under irradiation even in 3D culture condition.