As reported previously, the dysregulation of the PI3K/Akt pathway was relevant to acne vulgaris (55), which is consistent with our observation that the expression of PI3K and Akt was significantly up-regulated after the infection of C. acnes. We also found a pronounced reduction of the expression of BAD and its downstream apoptosis-related proteins: caspase-9 and caspase-3, after the infection of C. acnes. Here, CASP9 is linked to infection.