In this study, PFOS induced proliferation of severalcancer cell lines by greater than 2-fold, and the fold induction ofothers varied from <2-fold to minimal induction of cell proliferationeffects (Figure 3).The variable responsiveness of these cell lines to the growth-promotingeffects of PFOS is not uncommon for other growth-promoting substances;we hypothesized that the variability may be due to PFOS-mediated growthinhibition by activating PPARγ since PFOS binds PPARγ.However, this is unlikely since PPARγ inhibitors do not enhancePFOS-induced cancer cell growth (Figure S1). Here, PPARG is linked to cancer.