The combination of a nuclear HMGB1-positive and HMGB2-negative expression is potentially associated with a shortened survival in patients with pancreatic ductal adenocarcinoma

High-mobility group box (HMGB) proteins are ubiquitous, abundant nuclear non-histone chromosomal proteins that play a critical role in binding to distorted DNA structures and subsequently regulating DNA transcription, replication, repair, and recombination. Both HMGB1 and HMGB2 exhibit a high expression in several human cancers and are closely associated with tumor progression and a poor prognosis. However, the expression patterns of these molecules in pancreatic ductal adenocarcinoma (PDAC) remain to be elucidated. As most cases of postoperative relapse of PDAC occur within the first 2 years, the clinical significance of accurate biomarkers is needed. Therefore, we investigated the correlation between the immunohistochemical HMGB1 and HMGB2 expression and the clinicopathological characteristics and prognosis using 62 paraffin-embedded tumor samples obtained from patients with surgically resected PDAC. The HMGB1/2 expression was considered to be positive when 10 % or more of the cancer cells showed positive nuclear, not merely cytoplasmic, staining. Consequently, the expression of HMGB1/2 was observed in 54 (87.1 %) and 31 (50.0 %) patients, respectively. Unexpectedly, a positive HMGB1 expression was found to have a significantly close relationship with a negative HMGB2 expression. The univariate and multivariate analyses demonstrated that the patients with a HMGB1+ and HMGB2− status had markedly lower disease-specific survival rates, especially within the first 2 years postoperatively, whereas those with a HMGB1+ status alone did not. Therefore, the combination of a HMGB1+ and HMGB2− expression potentially predicts a poor prognosis in patients with PDAC, and these new biomarkers may be useful parameters for clinical management in the early postoperative phase.