title: Cardiac troponin I is abnormally expressed in non-small cell lung cancer tissues and human cancer cells.
abstract: Cardiac troponin I (cTnI) is the only sarcomeric protein identified to date that is expressed exclusively in cardiac muscle. Its expression in cancer tissues has not been reported. Herein, we examined cTnI expression in non-small cell lung cancer (NSCLC) tissues, human adenocarcinoma cells SPCA-1 (lung) and BGC 823 (gastric) by immunohistochemistry, western blot analysis and real-time PCR. Immunopositivity for cTnI was demonstrated in 69.4% (34/49) NSCLC tissues evaluated, and was strong intensity in 35.3% (6/17) lung squamous cell carcinoma cases. The non-cancer-bearing lung tissues except tuberculosis (9/9, 100%) showed negative staining for cTnI. Seven monoclonal antibodies (mAbs) against human cTnI were applied in immunofluorescence. The result showed that the staining pattern within SPCA-1 and BGC 823 was dependent on the epitope of the cTnI mAbs. The membrane and nucleus of cancer cells were stained by mAbs against N-terminal peptides of cTnI, and cytoplasm was stained by mAbs against the middle and C-terminal peptides of cTnI. A ~25 kD band was identified by anti-cTnI mAb in SPCA-1 and BGC 823 extracts by western blot, as well as in cardiomyocyte extracts. The cTnI mRNA expressions in SPCA-1 and BGC 823 cells were about ten thousand times less than that in cardiomyocytes. Our study shows for the first time that cTnI protein and mRNA were abnormally expressed in NSCLC tissues, SPCA-1 and BGC 823 cells. These findings challenge the conventional view of cTnI as a cardiac-specific protein, enabling the potential use of cTnI as a diagnostic marker or targeted therapy for cancer.
authors.affiliation: Research Institute of Cardiovascular Disease, The First Affiliated Hospital of Nanjing Medical University 300 Guangzhou Road, Nanjing 210029, China.
authors.forename: Chao
authors.initials: C
authors.lastname: Chen
authors.affiliation: Department of Cardiology, The First Affiliated Hospital of Nanjing Medical University 300 Guangzhou Road, Nanjing 210029, China.
authors.forename: Jia-Bao
authors.initials: JB
authors.lastname: Liu
authors.affiliation: Research Institute of Cardiovascular Disease, The First Affiliated Hospital of Nanjing Medical University 300 Guangzhou Road, Nanjing 210029, China.
authors.forename: Zhi-Ping
authors.initials: ZP
authors.lastname: Bian
authors.affiliation: Department of Cardiology, The First Affiliated Hospital of Nanjing Medical University 300 Guangzhou Road, Nanjing 210029, China.
authors.forename: Jin-Dan
authors.initials: JD
authors.lastname: Xu
authors.affiliation: Department of Cardiology, The First Affiliated Hospital of Nanjing Medical University 300 Guangzhou Road, Nanjing 210029, China.
authors.forename: Heng-Fang
authors.initials: HF
authors.lastname: Wu
authors.affiliation: Research Institute of Cardiovascular Disease, The First Affiliated Hospital of Nanjing Medical University 300 Guangzhou Road, Nanjing 210029, China.
authors.forename: Chun-Rong
authors.initials: CR
authors.lastname: Gu
authors.affiliation: Department of Respiratory and Critical Care Medicine, Jinling Hospital, School of Medicine, Nanjing University 305 Zhongshan East Road, Nanjing 210002, China.
authors.forename: Yi
authors.initials: Y
authors.lastname: Shi
authors.affiliation: Research Institute of Cardiovascular Disease, The First Affiliated Hospital of Nanjing Medical University 300 Guangzhou Road, Nanjing 210029, China.
authors.forename: Ji-Nan
authors.initials: JN
authors.lastname: Zhang
authors.affiliation: Research Institute of Cardiovascular Disease, The First Affiliated Hospital of Nanjing Medical University 300 Guangzhou Road, Nanjing 210029, China.
authors.forename: Xiang-Jian
authors.initials: XJ
authors.lastname: Chen
authors.affiliation: Department of Cardiology, The First Affiliated Hospital of Nanjing Medical University 300 Guangzhou Road, Nanjing 210029, China.
authors.forename: Di
authors.initials: D
authors.lastname: Yang
mesh_terms: D000230:Adenocarcinoma / Q000378:metabolism* / Q000473:pathology; D002289:Carcinoma, Non-Small-Cell Lung / Q000378:metabolism* / Q000473:pathology; D002294:Carcinoma, Squamous Cell / Q000378:metabolism / Q000473:pathology; D045744:Cell Line, Tumor; D005753:Gastric Mucosa / Q000378:metabolism; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D007150:Immunohistochemistry; D008168:Lung / Q000378:metabolism / Q000473:pathology; D008175:Lung Neoplasms / Q000378:metabolism* / Q000473:pathology; D032383:Myocytes, Cardiac / Q000378:metabolism / Q000473:pathology; D060888:Real-Time Polymerase Chain Reaction; D013270:Stomach / Q000473:pathology; D013274:Stomach Neoplasms / Q000378:metabolism* / Q000473:pathology; D019210:Troponin I / Q000235:genetics / Q000378:metabolism*
chemical_list: D019210:Troponin I
keywords: Cardiac troponin I; human gastric adenocarcinoma cell line BGC 823; human lung adenocarcinoma cell line SPCA-1; non-small cell lung cancer