Proteomic profiling of cholangiocarcinoma: Diagnostic potential of SELDI-TOF MS in malignant bile duct stricture

Abstract

Proteomic techniques promise to improve the diagnosis of cholangiocarcinoma (CC) in both tissue and serum as histological diagnosis and existing serum markers exhibit poor sensitivities. We explored the use of surface-enhanced laser desorption/ionization time-of-flight mass spectrometry (SELDI-TOF MS) to identify potential protein biomarkers of CC. Twenty-two resected CC samples were compared with adjacent noninvolved bile duct tissue. Serum from patients with CC (n ‫؍‬ 20) was compared with patients with benign disease (n ‫؍‬ 20), and healthy volunteers (n ‫؍‬ 25). Samples were analyzed on hydrophobic protein chips via SELDI-TOF MS, and classification models were developed using logistic regression and cross-validation analysis. Univariate analysis revealed 14 individual peaks differentially expressed between CC and bile duct tissue, 4 peaks between CC and benign disease, and 12 peaks between CC and sera of healthy volunteers. The 4,462 mass-to-charge serum peak had superior discriminatory ability to carbohydrate antigen 19.9 (CA19.9) and carcinoembryonic antigen ( C holangiocarcinoma (CC) is a rare but devastating neoplasm that accounts for 3% of all gastrointestinal cancers and 15% of all primary liver cancers worldwide. 1 Five thousand new cases are diagnosed on average per year in the United States, and the incidence is rising. 2 Northeast Thailand sees the highest incidence, with 96 cases per 100,000. 1 Surgical resection is the only current chance of cure, with no proven adjunctive therapy; however, this approach has a mortality rate of 5% to 10%. 3 Even with margin-free resection, 5-year survival figures only reach 20% to 40%. 3,4 Unresectable disease is usually fatal within 6 months to 1 year, and over one third of patients present at a stage too late for resection. 3 This confirms the need for earlier and more accurate diagnostic processes.At present, diagnosis of CC relies on imaging of the biliary tree with computed tomography or ultrasonography in the presence of high clinical suspicion. Tissue diagnostic confirmation is possible for intrahepatic tumors but is very difficult in more distal and more common (2/3 of cases) extrahepatic cases. These frequently present as a stricture of the common bile duct, which can be further characterized by means of endoscopic retrograde cholangio-pancreatography. 5

A combination of serum leucine-rich α-2-glycoprotein 1, CA19-9 and interleukin-6 differentiate biliary tract cancer from benign biliary strictures

“…However, relatively few proteomic studies of BTC using cell lines, bile or tissue have been performed, and only two have investigated circulating markers (Scarlett et al , 2006; Wang et al , 2009). In this rare cancer (Shaib and El-Serag, 2004), our discovery analysis of pooled serum samples using immunoaffinity depletion, 2D-DIGE and LC-MS/MS was able to detect differential protein expression between the BTC, benign and healthy groups, including upregulation of the putative marker LRG1.…”

Serum and bile biomarkers for cholangiocarcinoma

“…The proteomic profile of serum samples from CCA patients was also analysed by Scarlett et al [23] on hydrophobic protein chips using SELDI time-of-flight mass spectrometry (SELDI-TOF-MS). Serum from patients with CCA (n ¼ 20) was compared with patients with benign disease (n ¼ 20) and healthy volunteers (n ¼ 25).…”

Confounding Effects of Benign Lung Diseases on Non-Small Cell Lung Cancer Serum Biomarker Discovery

“…Nonmalignant disease controls have been included in a number of SELDI cancer biomarker studies and confounding effects have either not been reported (presumably because they were not investigated or found to be negligible) or have only partially obscured cancer specific effects, e.g., [19][20][21]. We now report that some benign conditions can mimic the effect of cancer, a significant finding when one considers that much of the SELDI-based biomarker discovery literature utilizes only healthy controls, potentially generating many false leads.…”