Fig 2: Differential expression of P16INK4A in tumor samples. (A) Representative images of P16INK4A positivity in USC, P16INK4A negativity in UEC and P16INK4A negativity in normal endometrium. The normal tissue was obtained from 8 patients with leiomyoma who receiving hysterectomy procedures. Scale bar, 50 µm. (B) Percentage of P16INK4A-positive cases among 33 USC and 88 UEC samples. **P<0.01 (?2 test). (C) Western blot analysis of 6 endometrial cell lines (AN3CA, Hec1A, Hec108, Nou-1, EFE-184 and ETN-1). Vinculin was used as a loading control. (D) The reverse transcription-quantitative polymerase chain reaction results of the 6 endometrial cell lines (AN3CA, Hec1A, Hec108, Nou-1, EFE-184 and ETN-1) were analyzed and shown as relative P16INK4A mRNA level of the Hec1A values, which were then converted as fold change. *P<0.05 and **P<0.01 [analysis of variance and a post hoc test (Student-Newman-Keuls)]. (E) Response of different endometrial cell lines to the CDK4/6 inhibitor palbociclib. The viability of ETN-1, EFE-184, Hec-1A, AN3CA, Hec108 and Nou-1 cells was measured with a Cell Counting Kit-8 assay following treatment with vehicle (dimethyl sulfoxide) and palbociclib (0.5, 1, 2.5, 5 and 10 µM) for 72 h. The IC50 are depicted. P16INK4A, cyclin-dependent kinase inhibitor 2A; CDK4, cyclin-dependent kinase 4; UEC, uterine endometroid carcinoma; USC, uterine serous carcinoma; H3K27, histone 3 lysine 27; KDM6B, histone lysine demethylase 6B; IC50, half-maximal inhibitory concentration; RB, retinoblastoma.

Fig 3: Graphical summary of the present study. (A) When USC is left untreated, P16INK4A serves an oncogenic role promoting endometrial cancer progression. (B) When USC is treated with GSK-J4, cancer progression is suppressed by P16INK4A through targeting KDM6B. USC, uterine serous cancer; P16INK4A, cyclin-dependent kinase inhibitor 2A; H3K27, histone 3 lysine 27; KDM6B, histone lysine demethylase 6B.