Published OnlineFirst May 9, 2012; DOI: 10.1158/1055-9965.EPI-11-1079 Cancer Epidemiology, Research Article Biomarkers & Prevention Expression of Kallikrein-Related Peptidase 7 Predicts Poor Prognosis in Patients with Unresectable Pancreatic Ductal Adenocarcinoma Vladimir Iakovlev1, Eric R. Siegel3, Ming-Sound Tsao2, and Randy S. Haun4 Abstract Background: Kallikrein-related peptidase 7 (KLK7) is overexpressed in pancreatic ductal adenocarcinomas (PDAC). The aims of this study were to examine the expression of KLK7 during progression of pancreatic intraepithelial neoplasia (PanIN) to invasive PDAC and to assess its prognostic significance for PDAC. Methods: Immunohistochemistry was used to assess KLK7 expression using a tissue microarray (TMA) and full sections of pancreatic tissue containing normal tissue, PanIN, and invasive adenocarcinoma, and the association between KLK7 expression and prognosis was examined by a population-based pancreatic cancer TMA. Results: Normal pancreatic epithelium was negative for KLK7 in either TMAs or full sections. Analysis by TMAs showed that 91% of cases showed KLK7 positivity in the adenocarcinoma component, which was significantly higher than PanIN 2/3. In full tissue sections of PDAC, KLK7 expression was detected in less than 1% of cells among PanIN 1A lesions, and increased with grade among PanIN 1B and PanIN2/3 lesions before reaching 69% in the invasive PDAC. In patients with unresected PDAC, KLK7 positivity was significantly associated with shorter overall survival. Conclusions: Aberrant KLK7 expression starts in intermediate-to-late stages of PanIN progression, and KLK7-positive staining is associated with almost a three-fold increase in mortality rate of patients with unresected PDAC. Impact: The association of KLK7 expression and poor outcome of patients with unresectable PDAC suggests that inhibiting either KLK7 expression and/or activity could be a therapeutic strategy. Because the vast majority of patients present with unresectable disease, such an intervention could have a significant impact upon the overall survival of this patient population. Cancer Epidemiol Biomarkers Prev; 21(7); 1135–42. Ó2012 AACR. Introduction during progression of low-grade pancreatic intraepithe- Pancreatic cancer is the fourth most common cause of lial neoplasms (PanIN) to infiltrating adenocarcinomas cancer-related deaths in men and women in the United has increased substantially in the past decade, prognosis States (1). Similar to other epithelial cancers, the devel- of patients upon diagnosis remains extremely poor. Most opment of pancreatic ductal adenocarcinomas (PDAC) is patients present with inoperable, locally advanced or multistep, with intermediate steps being defined by a metastatic disease; thus, median survival times for series of morphologic changes and molecular alterations patients diagnosed with locally advanced disease ranges during progression from intraepithelial lesions to inva- between 6 and 10 months, compared with only 3 to 6 sive carcinoma (reviewed in refs. 2, 3). Although our months for patients with metastatic disease (4). Even understanding of the genetic changes that accumulate patients who undergo resection of localized adenocarci- noma of the head of pancreas without metastatic spread Authors' Affiliations: 1Keenan Research Centre of the Li Ka Shing Knowl- have a median survival of only 13 to 15 months and a 15% edge Institute of St. Michael's Hospital, 2University Health Network, to 20% rate of long-term survival (5). Thus, numerous Princess Margaret Hospital/Ontario Cancer Centre and Department of prognostic factors have been assessed for their impact on Laboratory Medicine and Pathobiology, University of Toronto, Toronto, Ontario, Canada; and Departments of 3Biostatistics and 4Pharmaceutical survival following surgical resection of pancreatic ade- Sciences, Colleges of 3Medicine and 4Pharmacy, Winthrop P. Rockefeller nocarcinoma, and several have been shown to correlate Cancer Institute, University of Arkansas for Medical Sciences, and 4Central Arkansas Veterans Healthcare System, Little Rock, Arkansas with patient outcome, including clinicopathologic staging (e.g., tumor size, lymph node status), tumor biology, Corresponding Author: Randy S. Haun, Department of Pharmaceutical Sciences, University of Arkansas for Medical Sciences, 4301 W. Markham intraoperative factors, adjuvant chemoradiation therapy, St., #753, Little Rock, AR 72205. Phone: 501-686-8594; Fax: 501-686- and immunohistochemical markers such as VEGF, Bcl-2, 6517; E-mail: [email protected] p16, and p53 (6–9). doi: 10.1158/1055-9965.EPI-11-1079 We previously generated an expression profile of Ó2012 American Association for Cancer Research. serine proteases expressed in both normal and www.aacrjournals.org 1135 Downloaded from cebp.aacrjournals.org on September 28, 2021. © 2012 American Association for Cancer Research. Published OnlineFirst May 9, 2012; DOI: 10.1158/1055-9965.EPI-11-1079 Iakovlev et al. adenocarcinoma pancreatic tissues and found that Immunohistochemical staining kallikrein-related peptidase 7 (KLK7) is overexpressed Immunohistochemical staining was carried out as pre- in PDACs (10). KLK7, a chymotryptic-like serine pro- viously described (10). Briefly, formalin-fixed, paraffin- tease, was initially purified and characterized from embedded sections were deparaffinized and rehydrated human skin extracts and is thought to play a role in in xylene followed by graded ethanol. Following antigen desquamation of human skin (11, 12). Increasingly, retrieval, endogenous peroxidase activity was quenched however, the KLK7 transcript and/or KLK7 protein by hydrogen peroxide treatment followed by a protein have been found to be overexpressed in human cancers. block (Dako serum-free protein block). Sections were Other laboratories have showed that it is overexpressed incubated with a goat anti-hKLK7 antibody (R&D Sys- in ovarian (13, 14), squamous cervical (15), and breast tems, diluted 1:800) overnight in a humidified chamber at cancers (16). In the current study, we used immunohis- 4C. Immunoreactive staining was detected using a þ tochemistry to examine the expression of KLK7 in DAKO LSAB peroxidase system followed by hematox- lesions representing stages of PDAC development and ylin counterstain. to determine whether there is a correlation between KLK7 expression and overall survival (OS) in patients Evaluation of immunohistochemical analysis with pancreatic adenocarcinoma. In the initial analysis of the TMAs, each spot was assessed for the presence of the following components: normal pancreatic ducts, 3 grades of PanIN, or invasive Materials and Methods adenocarcinoma. KLK7 staining was recorded as positive Tissue samples in each component when there was unequivocal staining The study was approved by the Research Ethics Board in any number of cells. The number and percentage of at the University Health Network and Institutional spots with positivity in each component was calculated. Review Board at the University of Arkansas for Medical This TMA analysis showed higher frequency of KLK7 Sciences. For the initial analysis of KLK7 expression dur- positivity in more advanced lesions, so our next step was ing pancreatic adenocarcinoma tumorigenesis, tissue to quantify KLK7 expression using larger samples. Full microarrays (TMA) assembled by sampling of paraffin tissue sections of the blocks used for the TMA sampling blocks of 36 cases of resected PDACs were used (17). were visually assessed for the percentage of KLK7-posi- Normal, PanIN, and adenocarcinoma components were tive cells in each component. Then, after confirming that identified in TMA spots and assessed for KLK7 staining. KLK7 expression correlates with morphologic steps of Because of the nature of TMAs, individual spots contained disease progression, population-based TMAs were ana- one, several, or no targeted components (normal, PanIN, lyzed for associations between KLK7 positivity and clin- or adenocarcinoma); thus, 49 spots from 22 cases con- ical outcome. These TMAs were analyzed digitally using tained adenocarcinoma component, 17 spots from 17 previously described techniques (19, 20). Briefly, the cases contained PanIN 1 lesions, 46 spots from 35 cases KLK7-stained slide was scanned using an Aperio Scan- contained PanIN 2/3 lesions, and 32 spots contained Scope scanning system (Aperio Technologies). Each TMA normal ducts from 21 cases. After the initial analysis of spot was saved as a separate file, then all parts of the tissue the TMAs, full sections were prepared from PDAC tumor except for the component of interest were erased using blocks obtained following surgical resection and 22 cases "Photoshop CS3" (Adobe Systems). Then, the images were were found to contain the targeted components: normal processed to generate 2 sets of files: tissue masks to limit pancreatic ducts, invasive cancer, and at least one grade of analysis within the selected areas and signal images to PanIN in the same section. These full sections of 22 cases assess KLK7 staining intensity. The tissue masks were were evaluated for KLK7 immunoreactivity quantitative- obtained by thresholding through a value separating the ly. The full sections were chosen to reduce the biases of the clear background of histologic slides from the tissue. The TMA, such as small areas subject to heterogeneity effects signal images were generated by collecting the range of and unbalanced representation of cases by a different KLK7 brown color, erasing nonbrown pixels, and con- number of cores