Tissue Proteomics Reveals Differential and Compartment-Specific Expression of the Homologs Transgelin and Transgelin-2 in Lung Adenocarcinoma and Its Stroma

Abstract

Discovery of tissue-specific biomarkers for human cancer is crucial for early diagnosis and molecular understanding of the disease. To overcome the limitations posed by the large dynamic concentration range and compositional complexity of tissue biomacromolecules, we applied heparin affinity fractionation for proteomic enrichment. Comparing the proteomes of five paired samples of normal lung and pulmonary adenocarcinoma tissue by 2-D difference gel electrophoresis, 14 spots were found to be differentially expressed. From these candidate spots, three proteins overexpressed in cancer were identified by mass spectrometry as transgelin (TAGLN, SM22-α, WS3-10), transgelin-2 (TAGLN2), and cyclophilin A (PPIA). Quantitative RT-PCR indicated that both TAGLN2 and PPIA were upregulated at transcriptional level. Differential protein expression levels were validated by Western blot analysis using an independent set of 10 paired lung adenocarcinoma samples. Using immunohistochemistry on human tissue sections, we discovered that overexpression of TAGLN was strictly localized to the tumor-induced reactive myofibroblastic stromal tissue compartment, whereas overexpression of TAGLN2 was exclusively localized to the neoplastic glandular compartment. Thus, the highly homologous protein pair TAGLN and TAGLN2 displayed mutually exclusive, compartment-specific cell type expression regulation in tumor stroma vs. neoplastic epithelial cells. Our data further suggest that TGLN may be a marker of active stromal remodeling in the vicinity of invasive carcinomas. It may shed light on mechanisms of tumor-stroma interaction and could be useful for early diagnosis, treatment guidance, and treatment response monitoring.

Identification of novel molecular targets regulated by tumor suppressive miR-1/miR-133a in maxillary sinus squamous cell carcinoma

“…The protein encoded by the TAGLN gene is an actinbinding protein like TAGLN2, found in fibroblasts and smooth muscle (32). Overexpression of TAGLN2 was observed in hepatocellular carcinoma, lung adenocarcinoma, and pancreatic cancer (33)(34)(35)(36). More recently, we also found overexpression of TAGLN2 in HNSCC and bladder cancer (14,24).…”

TAGLN2 regulates T cell activation by stabilizing the actin cytoskeleton at the immunological synapse

“…The family comprises three isoforms, namely TAGLN1 (also known as transgelin1 or SM22, highly expressed in smooth muscle cells; CamorettiMercado et al, 1998), TAGLN2 (also known as transgelin2 or SM22, associated with various types of cancers; Zhang et al, 2002Zhang et al, , 2010Rho et al, 2009), and TAGLN3 (also known as transgelin3 or NP25, abundant in brain tissues; Mori et al, 2004). The term "transgelin" was originally derived from the transformation-sensitive and rapid actin-gelling properties of these proteins (Shapland et al, 1993).…”

Secretomic analysis of large cell lung cancer cell lines using two-dimensional gel electrophoresis coupled to mass spectrometry

“…Twenty three of the identified proteins have been previously found in human body fluids or the in vivo tumor microenvironment in pathological conditions other than lung cancer (Table 1) [17][18][19][20][21][22][23][24][25][26][27][28][29][30][31][32][33][34][35], indicating that they might be products of cellular secretion. Among them, those known to be overexpressed in lung cancer such as 78-kDa glucose-regulated protein [14], epidermal fatty acid-binding protein [36], transgelin-2 [37], hsp27 [38], stress-induced phosphoprotein 1 [38], vimentin [39], and transketolase [40] may be more appropriate candidate biomarkers for further validation in body fluids from lung cancer patients.…”