Fig. 1: YY1 highly expressed in the tongue cancer and knockdown of YY1 enhanced cisplatin-induced inhibition of cell proliferation, migration and invasion, and cisplatin-induced inhibition of xenograft tumor growth

. a YY1 mRNA expression in tongue cancer specimens. The mRNA expressions of YY1 in the tumor tissue and adjacent normal tissue of 37 cases were assessed by real-time PCR, *P < 0.05 (t-test, n = 37), NT, adjacent normal tissue; T, tumor. b, c Knockdown of YY1 enhanced cisplatin-induced cell proliferation inhibition. b CAL27 cells stably transfected with Tet-on YY1 shRNA were exposed to either doxycycline (100 nM) or cisplatin (10 μM) or both for 48 h and subjected to CCK-8 assay, n = 4; Microphotographs of CAL27 cells after different treatment, scale bar: 100 μm. c CAL27 cells stably transfected with YY1 shRNA or scramble shRNA were exposed to 10 μM cisplatin or not for 48 h and subjected to CCK-8 assay, n = 4. d Knockdown of YY1 enhanced cisplatin-induced cell apoptosis. CAL27 cells stably transfected with Tet-on YY1 shRNA were exposed to either doxycycline (100 nM) or cisplatin (10 μM) or both for 48 h and subjected to DAPI, scale bar: 100 μm. Cell counting of apoptotic cells from four separated fields and the rate of apoptotic cells was quantified, n = 4. e, f Knockdown of YY1 enhanced cisplatin-induced inhibition of cell migration and invasion. CAL27 Cells stably transfected with Tet-on YY1 shRNA were exposed to either doxycycline (100 nM) or cisplatin (10 μM) or both for 48 h. Transwell migration (e) or invasion (f) of the cells were photographed under a light microscope, scale bar: 100 μm. Migrated cells were counted from four separated fields, n = 4. g–j Knockdown of YY1 enhanced cisplatin-induced inhibition of xenograft tumor growth. Photograph and weights of xenograft tumors. g, h We injected nude mice with twice the amount of CAL27 cells stably transfected with YY1 shRNA lentivirus compared with CAL27 cells stably transfected with scramble shRNA lentivirus at groin and to make sure that the initial size of xenografts was equal before intraperitoneal injection of cisplatin, n = 4. i, j We injected nude mice with equal CAL27 cells stably transfected with Tet-on YY1 shRNA at axilla. We supplied with normal water or Dox (1 mg/ml) containing water and injected cisplatin or not, n = 5. All data (mean ± SD of four separated experiments) were presented as folds of the control group. b–j One-way ANOVA: *P < 0.05 vs. control group, ^#P < 0.05 vs. YY1 knockdown or cisplatin group