Here we observed that the IL-6 levels were extremely high in nicotine-treated hUC-MSCs compared to untreated hUC-MSCs (Figure 7E), indicating that IL-6 might be involved in driving lung cancer cells and breast cancer cells into more aggressive and invasive phenotypes after coculture with nicotine-treated hUC-MSCs and promoting tumor formation and growth. Here, IL6 is linked to breast cancer.