Only for three out of five cell lines (colorectal HCT-116, glioblastoma LN-18 and neuroblastoma SH-SY5Y), 24 h serum starvation caused an expected decrease in ERK1/2 activity, while for embryonic HEK-293T cells and lung adenocarcinoma H1299 cells, ERK/12 activity was slightly increased after serum removal. Here, MAPK1 is linked to glioblastoma.