Glycosylated Alpha-1-acid glycoprotein 1 as a potential lung cancer serum biomarker.

Presently existing screening approaches for lung cancer are not being proving sufficient and sensitive, so a study was conducted to identify disease related biomarker proteins for diagnostic applications. A total of 100 lung cancer patients (88 non-small cell lung cancer and 12 small cell lung cancer) and 50 healthy controls were included in this study. Serum samples of patients and healthy controls were subjected to a series of proteomic approaches and as a result of two dimensional gel electrophoresis, a ∼ 43 kDa protein was found to be differentially expressed compared to healthy controls. Quantitative profiling of two dimensional gels by Dymension software analysis displayed 3.58 fold increased expression of ∼ 43 kDa protein in squamous cell carcinoma and 2.92 fold in case of adenocarcinoma. Mass spectrometric analysis resulted in identification of 8 differentially expressed proteins, out of which human Alpha-1-acid glycoprotein 1 was targeted for further validations. This candidate protein exhibited N-linked glycosylation at five amino acid residues; 33, 56, 72, 93, and 103 with significant score of 0.66, 0.78, 0.78, 0.53 and 0.66, respectively. Sandwich ELISA quantified high serum levels of Alpha-1-acid glycoprotein 1 in squamous cell carcinoma (2.93 g/l ± 1.22) and adenocarcinoma (2.39 g/l ± 1.13) when compared with healthy controls (0.83 g/l ± 0.21). One-way ANOVA analysis predicted highly significant variation of Alpha-1-acid glycoprotein 1, among all the study types (F-value 65.37, p-value 0.000). This study may prove as a non-invasive, cost effective and sensitive scheme for diagnosis of lung cancer, by passing the expensive and painful screening procedures.

Mass spectrometric identification, characterization and validation of the haptoglobin ß-chain protein as a lung cancer serum biomarker.

Lung cancer is the major contributor to overall cancer-related mortality. Biomarkers are important in early detection and prognosis, in addition to developing treatment regimes, which may improve the patient survival rates. Biomarkers may also assist in investigating the in depth metabolic pathways and in establishing a set of therapeutic agents leading to early detection of the disease. The present study was designed to identify and confirm a lung cancer protein biomarker and to correlate the differential expression of the protein to a particular histological disease type. A total of 100 lung cancer patients and 50 healthy controls were included in the present study and were categorized into the two main histological types of lung cancer; non­small cell lung cancer (NSCLC; n=88) and small cell lung cancer (SCLC; n=12). NSCLC was further subclassified into three histological types; adenocarcinoma (n=34), squamous cell carcinoma (n=48) and large cell carcinoma (n=6). The patient and control serum samples underwent sodium dodecyl sulphate polyacrylamide gel electrophoresis characterization followed by two­dimensional gel electrophoresis. Following mass spectrometry, human haptoglobin was identified with a mass of ~42­46 kDa and an isoelectric point (pI) of ~5.5­6.2. The experimental mass of the protein was found to be 45.8 kDa with a pI of 6.13. The matrix­assisted laser desorption/ionization time­of­flight/time­of­flight data exhibited spectral peaks of 1146.134, 1724.191, 1345.339 and 2210.319 m/z and Mascot search analysis identified these peaks as haptoglobin (accession no. P00738; Mascot score 87; sequence coverage 23%). This protein was significantly overexpressed in squamous cell carcinoma and adenocarcinoma, as compared with the control. The present study described differentially expressed human haptoglobin as a lung cancer serum protein biomarker, which may serve as a diagnostic and therapeutic target and set a standard criteria for the evaluation of histological types of lung cancer compared with other disease types.