FIGURE 8.

TC-PTP regulates keratinocyte survival and proliferation after UVB irradiation by inhibiting STAT3 signaling. A, STAT3 transcriptional activity was assessed after UVB irradiation (5 and 10 mJ/cm²) in 3PC keratinocytes. Keratinocytes were cultured and transfected with control or TC-PTP siRNA. Cells were collected 24 h after UVB irradiation. Results are the mean ± S.D. (error bars) from three independent experiments. *, p < 0.05 by Student's t test for equality of means. B, analysis of STA-21 cytotoxicity on 3PC keratinocytes. Keratinocytes were plated and treated with different concentrations of STA-21 for 18 h. Cytotoxicity was determined by lactate dehydrogenase release in medium. C, keratinocytes were cultured and transfected with control or TC-PTP siRNA individually and irradiated with UVB at a dose of 2 mJ/cm². STA-21 or DMSO as a control was pretreated 1 h before UVB treatment. Cell viability was evaluated 48 h after UVB treatment. Results are the mean ± S.D. from three independent experiments. *, p < 0.05 by Student's t test for equality of means.