Moon Chul Kang

Genome-wide analysis of DNA methylation and the gene expression change in lung cancer.

Introduction: The recent DNA methylation studies on cancers have revealed the necessity of profiling an entire human genome and not to restrict the profiling to specific regions of the human genome. It has been suggested that genome-wide DNA methylation analysis enables us to identify the genes that are regulated by DNA methylation in carcinogenesis. Methods: So, we performed whole-genome DNA methylation analysis for human lung squamous cell carcinoma (SCC), which is strongly related with smoking. We also performed microarrays using 21 pairs of normal lung tissues and tumors from patients with SCC. By combining these data, 30 hypermethylated and down-regulated genes, and 22 hypomethylated and up-regulated genes were selected. The gene expression level and DNA methylation pattern were confirmed by semiquantitative reverse-transcriptase polymerase chain reaction and pyrosequencing, respectively. Results: By these validations, we selected five hypermethylated and down-regulated genes and one hypomethylated and up-regulated gene. Moreover, these six genes were proven to be actually regulated by DNA methylation by confirming the recovery of their DNA methylation pattern and gene expression level using a demethylating agent. The DNA methylation pattern of the CYTL1 promoter region was significantly different between early and advanced stages of SCC. Conclusion: In conclusion, by combining the whole-genome DNA methylation pattern and the gene expression profile, we identified the six genes (CCDC37, CYTL1, CDO1, SLIT2, LMO3, and SERPINB5) that are regulated by DNA methylation, and we suggest their value as target molecules for further study of SCC.

Oncogenic role of protein tyrosine kinase 7 in esophageal squamous cell carcinoma

Esophageal squamous cell carcinoma (ESCC) is a common subtype of esophageal cancer that is particularly prevalent in East Asian countries. Our previous expression profile analysis showed that the gene encoding protein tyrosine kinase 7 (PTK7) is upregulated in ESCC tissues. Here, we aimed to validate PTK7 as a prognostic factor and a candidate target for molecular treatment of ESCC. Both RT‐PCR and Western blot analysis of tissues from ESCC patients revealed that PTK7 was significantly upregulated in tumor tissue samples of ESCC. Immunohistochemical staining of PTK7 showed that increased expression of PTK7 was inversely correlated with overall survival (P = 0.021). In vitro knockdown of PTK7 inhibited proliferation, survival, wound healing, and invasion of ESCC cells. In addition, PTK7 knockdown decreased phosphorylation of Akt, Erk, and focal adhesion kinase (FAK), important determinants of cell proliferation, survival, and migration. Therefore, our findings suggest that PTK7 has potential as a prognostic marker for ESCC and might also be a candidate for targeted therapy in the treatment of ESCC.

Protein tyrosine kinase 7 plays a tumor suppressor role by inhibiting ERK and AKT phosphorylation in lung cancer

Protein tyrosine kinase 7 (PTK7) is a catalytically inactive receptor tyrosine kinase that is also known as colon carcinoma kinase-4 (CCK-4). Recent reports have shown that PTK7 plays an important role in carcinogenesis, and it is known to be upregulated in gastric, colon and esophageal cancer, as well as in liposarcoma. However, the role of PTK7 in lung cancer has not been investigated. The aim of the present study was to investigate the expression levels and the role of PTK7 in lung cancer. We found that PTK7 expression was downregulated at the mRNA as well as protein levels in human lung squamous cell carcinoma (LSCC). Upon investigation of the functional role of PTK7 in LSCC, we found that overexpression of PTK7 in LSCC cells resulted in inhibition of cell proliferation, invasion and migration. Furthermore, we confirmed that these phenotypic changes are associated with the inactivation of AKT and ERK. Our findings suggest that PTK7 has different oncogenic roles in organs and target tumors.

Integrin alpha 6: A novel therapeutic target in esophageal squamous cell carcinoma

Esophageal squamous cell carcinoma (ESCC), the most common subtype of esophageal cancer in East Asian countries, is a devastating disease characterized by distinctly high incidence and mortality rates. Our previous expression profile analysis showed that integrin alpha 6 (ITGA6) is highly expressed in ESCC tissues. To validate cell surface expression of ITGA6 as a novel target in ESCC, we investigated ITGA6 expression in tumor tissue samples and cell lines of ESCC and found that ITGA6 was upregulated in these cells. In vitro knockdown of ITGA6 in ESCC cells resulted in inhibition of cell proliferation, invasion and colony formation. In addition, we demonstrated that ITGA6 associates with integrin beta 4 (ITGB4), and that this heterodimer complex is upregulated in both ESCC tissues and cell lines. Moreover, our biodistribution results in an ESCC xenograft model indicated that ITGA6 is a possible target for antibody-related diagnostic and therapeutic modalities in ESCC. Thus, our findings suggest that ITGA6 plays an important role in tumorigenesis in ESCC and represents a potential therapeutic target in the treatment of ESCC.

Epigenetic regulation of the novel tumor suppressor cysteine dioxygenase 1 in esophageal squamous cell carcinoma.

Esophageal squamous cell carcinoma (ESCC), the most common subtype of esophageal cancer in East Asian countries, is still associated with a poor prognosis because of the high frequency of lymph node metastasis and invasion. In our previous study, we identified a novel methylation gene, cysteine dioxygenase 1 (CDO1) that is involved in the conversion of cysteine to cysteine sulfinate, and plays a key role in taurine biosynthesis. Decreased expression of CDO1 was observed in ESCC cell lines and tumors derived from patient tissues, and CDO1 silencing could be reversed by treatment with 5-aza-2′-deoxycytidine in six ESCC cell lines. Forced expression of CDO1 in three different ESCC cell lines, TE-4, TE-6, and TE-14, significantly decreased tumor cell growth, cell migration, invasion, and the ability of colony formation. Although CDO1 expression was not found to significantly correlate with survival in ESCC patients, our results suggest that methylation-regulated CDO1 may represent a functional tumor suppressor and a potentially valuable diagnostic biomarker for ESCC.

PTK7 regulates radioresistance through nuclear factor-kappa B in esophageal squamous cell carcinoma.

Tumor radioresistance is a major reason for decreased efficiency of cancer radiation therapy. Although a number of factors involved in radioresistance have been identified, the molecular mechanisms underlying radioresistance of esophageal squamous cell carcinoma (ESCC) have not been elucidated. In this study, we investigated the role of oncogenic protein tyrosine kinase 7 (PTK7) in the resistance of ESCC to radiation therapy. ESCC cell lines with high PTK7 expression were more refractive to radiation than those with low PTK7 levels. In radioresistant ESCC cells, PTK7 knockdown by specific siRNAs decreased the survival of irradiated cells and increased radiation-induced apoptosis, while in radiosensitive ESCC cells, PTK7 overexpression promoted cell survival and inhibited radiation-induced apoptosis. We hypothesized that PTK7 could regulate the activation of transcription factor NF-kB known for its role in cancer radioresistance. Our results indicated that the inhibition of PTK7 suppressed nuclear translocation of NF-kB subunit p65 induced by radiation, suggesting relevance of PTK7 expression with NF-kB activation in radioresistant ESCC. Furthermore, the levels of inhibitor of apoptosis proteins (IAPs), XIAP, and survivin, encoded by NF-kB-regulated genes, were induced in irradiated radioresistant cells but not in radiosensitive cells, while PTK7 knockdown downregulated IAP expression. Our findings revealed a novel mechanism underlying radioresistance in ESCC, which is associated with PTK7 and NF-kB-dependent apoptosis. These results suggest that the manipulation of PTK7 expression can be instrumental in enhancing ESCC response to radiotherapy. This study demonstrates that PTK7 plays a significant role in ESCC radioresistance via the NF-kB pathway.

MiR-338-5p enhances the radiosensitivity of esophageal squamous cell carcinoma by inducing apoptosis through targeting survivin

Radioresistance is a challenge in the treatment of esophageal squamous cell carcinoma (ESCC). MicroRNAs (miRNAs) are known to play an important role in the functional modification of cancer cells and recent studies have reported miRNA-mediated radiotherapy resistance. However, further research is necessary to reveal the regulation mechanisms, and treatment strategies using miRNA are yet to be established for ESCC. We compared the miRNA expression profiles of ESCC parental (TE-4) and acquired radioresistance (TE-4R) cell lines using a miRNA microarray and qRT-PCR. Our data showed that miR-338-5p, one of the target miRNA biomarkers, was significantly downregulated in TE-4R. Ectopic overexpression of miR-338-5p induced apoptosis and sensitivity to radiation treatment by interfering with survivin, which is a known inhibitor of apoptosis. Overexpression of survivin reversed miR-338-5p-induced apoptosis. Tumor xenograft experiments indicated that therapeutic delivery of the miR-338-5p mimics via direct injection into tumor mass increased sensitivity to radiation therapy. In conclusion, our findings suggest that miR-338-5p is a potential radiosensitizer and may be a therapeutic biomarker for radioresistant in ESCC.

Pulmonary Metastasectomy in Adult Patients with Synovial Sarcoma: A Single-Center Experience

Background This study assessed the efficacy of pulmonary metastasectomy for synovial sarcoma in adult patients. Methods Fifty patients, diagnosed with pulmonary metastasis from June 1990 to August 2010, were reviewed retrospectively. Twenty-eight patients underwent complete pulmonary metastasectomy, and their survival was evaluated. Age, sex, time to metastatic progression, laterality, number of tumors, size of largest nodule, and number of metastasectomies were analyzed as potential prognostic factors. Results In all, 29 patients underwent at least one pulmonary metastasectomy, and 51 resections were performed. One intraoperative mortality occurred, and the 5-year survival rate was 58.4%. Bilateral metastases and early metastatic progression were associated with poor survival in multivariate analyses. Conclusion Surgical resection can be a good option for treating pulmonary metastasis in patients with synovial sarcoma. Repeated resection was feasible with low mortality and morbidity.