Fig. 1: The phosphorylation level of PA28γ at T23 is highly expressed in various cancers and is associated with AJCC stage and patient prognosis.

a Determination of PA28γ phosphorylation sites by liquid chromatography-tandem mass spectrometry (LC-MS/MS) analysis. The LC-MS/MS spectrum of modified “IT_(phos)SEAEDLVANFFPK” is shown. b Immunoblot (IB) analysis of immunoprecipitation (IP) products and whole-cell lysates (WCLs) derived from HNSCC cells transduced with empty vector (EV), Flag-PA28γ WT, T23A, or T23D. c Human HNSCC tumors and paired adjacent normal tissues were extracted and collected to IB analysis (n = 4). Statistical analysis of the normalized level of PA28γ-pT23 is shown. A, adjacent tissue; T, tumor tissue. d–f IHC analyses of PA28γ-pT23 in the tissue microarray (TMA) containing 81 HNSCC patients with paired tumors and adjacent tissues. Assessment of their levels in tumors and adjacent tissues (d) as well as in different AJCC stages (e). Survival analysis with Kaplan-Meier curves was performed on their high and low levels (f). Scale bars, 100 μm. g, h IHC analyses of PA28γ-pT23 in the TMA containing 13 types of cancer with paired tumors and adjacent tissues. Representative samples (g) and statistical analysis (h) of PA28γ-pT23 levels in tumors and adjacent tissues are shown. Scale bars, 100 μm. i IHC analyses of PA28γ-pT23 in rectal cancer TMA (n = 90), pancreatic cancer TMA (n = 89), and breast cancer TMA (n = 130). Survival analysis with Kaplan-Meier curves was performed on PA28γ-pT23 high and low levels. Statistical significance was assessed by two-sided paired t-test in (c, d) unpaired t-test in (e, h) and log-rank (Mantel-Cox) test in (f, i). Source data are provided as a Source Data file.