Expression of a Candidate Ataxia-telangiectasia Group D Gene in Cultured Fibroblast Cell Lines and Human Tissues

Identification of Novel Diagnostic Markers for Malignant Pleural Mesothelioma Using a Reverse Translational Approach Based on a Rare Synchronous Tumor

Although the routine use of immunohistochemistry has improved the accuracy of histopathologic diagnosis in clinical practice, new methods for discovering novel diagnostic markers are still needed. We sought new diagnostic markers for malignant pleural mesothelioma (MPM) using a reverse translational approach with limited archival tissues from a very rare case. Total RNA extracted from formalin-fixed paraffin-embedded (FFPE) tissues of a synchronous collision tumor consisting of MPM and pulmonary adenocarcinoma (PAC) was employed for gene expression profiling (GEP) analysis. Among the 54 genes selected by GEP analysis, we finally identified the following two candidate MPM marker genes: PHGDH and TRIM29. Immunohistochemical analysis of 48 MM and 20 PAC cases showed that both PHGDH and TRIM29 had sensitivity and specificity almost equivalent to those of calretinin (sensitivity 50% and 46% vs. 63%, and specificity 95% and 100% vs. 100%, respectively). Importantly, of the 23 epithelioid MMs, all 3 calretinin-negative cases were positive for TRIM29. These two markers may be diagnostically useful for immunohistochemical distinction between MPMs and PACs. This successful reverse translational approach based on FFPE samples from one very rare case encourages the further use of such samples for the development of novel diagnostic markers.

Oncogenic function of ATDC in pancreatic cancer through Wnt pathway activation and beta-catenin stabilization

Pancreatic cancer is a deadly disease characterized by late diagnosis and resistance to therapy. Much progress has been made in defining gene defects in pancreatic cancer, but a full accounting of its molecular pathogenesis remains to be provided. Here, we show that expression of the ataxia-telangiectasia group D complementing gene (ATDC), also called TRIM29, is elevated in most invasive pancreatic cancers and pancreatic cancer precursor lesions. ATDC promoted cancer cell proliferation in vitro and enhanced tumor growth and metastasis in vivo. ATDC expression correlated with elevated beta-catenin levels in pancreatic cancer, and beta-catenin function was required for ATDC's oncogenic effects. ATDC was found to stabilize beta-catenin via ATDC-induced effects on the Disheveled-2 protein, a negative regulator of glycogen synthase kinase 3beta in the Wnt/beta-catenin signaling pathway.

Suppression of anchorage-independent growth by expression of the ataxia-telangiectasia group D complementing gene, ATDC

The ataxia-telangiectasia group D complementing gene, ATDC, is located at 11q23, where loss of heterozygosity (LOH) is frequently observed in many kinds of cancers including breast cancer. Underexpression of ATDC in breast and prostate cancer has been reported using serial analysis of gene expression (SAGE) and DNA microarray analysis. We previously reported that SV-40-transformation down-regulates the expression of ATDC. In the present study, we investigated the roles of ATDC in carcinogenesis. First, we investigated the expression of ATDC in 11 cancer cell lines. No detectable transcript was observed in 4 tumor cell lines, and no ATDC protein was detected in 8 tumor cell lines. We transfected ATDC expression vector into Saos-2 and BT-549 that lacked detectable mRNA and protein expression of ATDC. Colony-forming efficiency in soft agar was significantly suppressed in all of the ATDC transfectants. These results suggest that suppressed ATDC expression is associated with malignant phenotype.

Expression of the ATDC (ataxia telangiectasia group D-complementing) gene in A431 human squamous carcinoma cells

The ATDC gene was originally identified by its ability to complement the radiosensitivity defect of an ataxia telangiectasia (AT) fibroblast cell line. Because hypersensitivity to ionizing radiation is an important feature of the AT phenotype, we reasoned that ATDC may function generally in the suppression of radiosensitivity. Previous work in our laboratory focused on radiosensitization mechanisms in human squamous carcinoma (SC) cells, especially A431 cells. To establish a basis for investigating the role of ATDC in radiation-responsive signaling pathways in human SC cells, we characterized ATDC message and protein expressions in A431 cells. ATDC message expression was also compared among human epidermoid cells (A431 cells, HaCaT spontaneously immortalized human keratinocytes and normal human epidermal keratinocytes) and a normal human fibroblast cell line (LM217). We made the following major observations: (i) the relative abundance of ATDC message is substantially higher in the epidermoid cells than in the fibroblast cell line, which has a message level comparable to those reported for other fibroblast lines; (ii) ATDC is constitutively phosphorylated on serine/threonine in A431 cells; (iii) in A431 cells, ATDC is a substrate for the serine/threonine protein kinase C (PKC) but not the epidermal growth factor (EGF) receptor tyrosine kinase; and (iv) EGF decreases ATDC message and protein expressions in A431 cells after a 24-hr exposure. The phosphorylation studies suggest that the ability of ATDC to modulate cellular radiosensitivity may be mediated in part through a PKC signaling pathway.