HMGA1 correlates with advanced tumor grade and decreased survival in pancreatic ductal adenocarcinoma

Abstract

Although pancreatic ductal adenocarcinoma is a common and almost uniformly fatal cancer, little is known about the molecular events that lead to tumor progression. The high-mobility group A1 (HMGA1) protein is an architectural transcription factor that has been implicated in the pathogenesis and progression of diverse human cancers, including pancreatic ductal adenocarcinoma. In this study, we investigated HMGA1 expression in pancreatic ductal adenocarcinoma cell lines and surgically resected tumors to determine whether it could be a marker for more advanced disease. By real-time quantitative RT-PCR, we measured HMGA1a mRNA in cultured pancreatic ductal adenocarcinoma cell lines and found increased levels in all cancer cells compared with normal pancreatic tissue. To investigate HMGA1 in primary human tumors, we performed immunohistochemical analysis of 125 cases of pancreatic adenocarcinoma and 99 precursor lesions (PanIN 1-3). We found nuclear staining for HMGA1 in 98% of cases of pancreatic adenocarcinoma, but only 43% of cases of PanIN precursor lesions. Moreover, HMGA1 immunoreactivity correlates positively with decreased survival and advanced tumor and PanIN grade. These results suggest that HMGA1 promotes tumor progression in pancreatic ductal adenocarcinoma and could be a useful biomarker and rational therapeutic target in advanced disease.

Figure 1

HMGA1a mRNA expression in human pancreatic ductal adenocarcinoma cell lines. HMGA1a mRNA levels were measured by quantitative RT-PCR and normalized to human phosphoprotein. Normal human pancreatic tissue from a healthy 35-year-old donor was used as a control and assigned a value of 1. HMGA1a mRNA levels are significantly above control in all cell lines (4-fold ±0.08, p <0.0001 for MIA PaCa-2 cells; 7-fold ±0.3, p <0.0001 for XPA-3 cells and 14-fold ±0.4, p <0.0001 for PL-1 cells vs 1 ±0.05 for normal human pancreas). Three independent experiments were performed in triplicate; results represent the mean ±s.e. from independent experiments. Normalization to β-glucuronidase and β-actin as control genes produced similar results in separate experiments (not shown).

Figure 2

HMGA1 protein was detected in the majority of PDA by immunohistochemistry and increased levels of HMGA1 immunoreactivity correlated inversely with tumor differentiation (HMGA1 antibody, Gill hematoxylin counterstain). (A) Strong immunoreactivity in poorly-differentiated pancreatic ductal adenocarcinoma (magnification X 64, score 9). There is limited HMGA1 reactivity in benign pancreatic ducts (arrows). (B) Moderate immunoreactivity in moderately-differentiated pancreatic ductal adenocarcinoma (magnification X 100, score 6). (C) Weak immunoreactivity in well-differentiated pancreatic ductal adenocarcinoma (magnification X 160, score 2).

Figure 2

HMGA1 protein was detected in the majority of PDA by immunohistochemistry and increased levels of HMGA1 immunoreactivity correlated inversely with tumor differentiation (HMGA1 antibody, Gill hematoxylin counterstain). (A) Strong immunoreactivity in poorly-differentiated pancreatic ductal adenocarcinoma (magnification X 64, score 9). There is limited HMGA1 reactivity in benign pancreatic ducts (arrows). (B) Moderate immunoreactivity in moderately-differentiated pancreatic ductal adenocarcinoma (magnification X 100, score 6). (C) Weak immunoreactivity in well-differentiated pancreatic ductal adenocarcinoma (magnification X 160, score 2).

Figure 2

HMGA1 protein was detected in the majority of PDA by immunohistochemistry and increased levels of HMGA1 immunoreactivity correlated inversely with tumor differentiation (HMGA1 antibody, Gill hematoxylin counterstain). (A) Strong immunoreactivity in poorly-differentiated pancreatic ductal adenocarcinoma (magnification X 64, score 9). There is limited HMGA1 reactivity in benign pancreatic ducts (arrows). (B) Moderate immunoreactivity in moderately-differentiated pancreatic ductal adenocarcinoma (magnification X 100, score 6). (C) Weak immunoreactivity in well-differentiated pancreatic ductal adenocarcinoma (magnification X 160, score 2).

Figure 3

A Kaplan-Meier curve demonstrates that HMGA1 reactivity inversely related to mean survival. Patients with limited to no HMGA1 reactivity (score <3) had longer survival than those with moderate or strong HMGA1 reactivity (score 3–6 and score>6, respectively). Further, patients with the strongest HMGA1 reactivity (score >6) had the shortest survival (p =0.0175 by nonparametric rank sum test).

Figure 4

HMGA1 protein expression in PanIN determined by immunohistochemistry correlates with grade (HMGA1 antibody, Gill hematoxylin counterstain). (A) No HMGA1 immunoreactivity in a low grade PanIN lesion (PanIN-1B). (B) High HMGA1 immunoreactivity in a high grade PanIN lesion (PanIN-3).

Figure 4

HMGA1 protein expression in PanIN determined by immunohistochemistry correlates with grade (HMGA1 antibody, Gill hematoxylin counterstain). (A) No HMGA1 immunoreactivity in a low grade PanIN lesion (PanIN-1B). (B) High HMGA1 immunoreactivity in a high grade PanIN lesion (PanIN-3).