When they cultured liver cells with different cytochrome P450 (CYP) subtypes and glioblastoma multiforme (GBM) brain cancer cells in two separate chambers which were connected in tandem on a 3-D TE scaffold (biodegradable polylactic acid/PLA), they were able to test the cytotoxicity of anti-cancer drugs, including temozolomide (TMZ) and ifosfamide (IFO). Here, PPIG is linked to glioblastoma.