Predictive Potential of PD-L1, TYMS, and DCC Expressions in Treatment Outcome of Colorectal Carcinoma

Colorectal carcinoma (CRC) is a malignancy of epithelial origin in the large bowel. The elucidation of the biological functions of programmed cell death ligand-1 (PD-L1), thymidylate synthase (TYMS), and deleted in colorectal cancer (DCC) biomarkers including their roles in the pathophysiology of CRC - has led to their applications in diagnostic and chemo-pharmaceutics. We investigated whether PD-L1, TYMS, and DCC protein expression in CRC tumors are predictive biomarkers of treatment outcome for CRC patients. The expressions of PD-L1, TYMS, and DCC were evaluated by immunohistochemistry (IHC) in 91 paraffin-embedded samples from patients who underwent colectomy procedure in Hospital Serdang, Selangor, Malaysia. There was high expression of DCC in most cases: 84.6% (77/91). PD-L1 showed low expression in 93.4% (86/91) of cases and high expression in 6.6% (5/91) of cases. Low and high expressions of TYMS were detected in 53.8% (49/91) and 46.2% (42/91) of the CRC cases, respectively. There was a significant association between the TYMS expression and gender (P < 0.05); the expression of TYMS was observed at a high level in 76.2% of males and in 23.8% of females. The mean overall survival (OS) was 100 months for the CRC patients evaluated. The OS for patients with high expression of PD-L1 was 22 months. Patients with high expression of TYMS and DCC showed OS of 90 and 96 months, respectively. The results from this study suggest that PD-L1, TYMS, and DCC expression could be used as biomarkers to stratify CRC patients who could benefit from adjuvant therapy.

Semaphorin 5A suppresses the proliferation and migration of lung adenocarcinoma cells

Semaphorin 5A (SEMA5A), a member of the semaphorin family, plays an important role in axonal guidance. Previously, the authors identified another possible role of SEMA5A as a prognostic biomarker for non-smoking women with lung adenocarcinoma in Taiwan, and this phenomenon has been validated in other ethnic groups. However, the functional significance of SEMA5A in lung adenocarcinoma remains unclear. Therefore, we assessed the function of SEMA5A in three lung adenocarcinoma cell lines in this study. Kaplan-Meier Plotter for lung cancer was conducted for survival analyses. Reverse transcription-quantitative PCR (RT-qPCR) and western blot analysis were performed to investigate the expression and post-translational regulation of SEMA5A in lung adenocar-cinoma cell lines. A pre-designed PyroMark CpG assay and 5-aza-2′-deoxycytidine treatment were used to measure the methylation levels of SEMA5A. The biological functions of lung adenocarcinoma cells overexpressing SEMA5A were investigated by microarrays, and validated both in vitro (proliferation, colony formation and migration assays) and in vivo (tumor xenografts) experiments. The results revealed that the hypermethylation of SEMA5A and the cleavage of the extracellular domain of SEMA5A were responsible for the downregulation of the SEMA5A levels in lung adenocarcinoma cells (A549 and H1299) as compared to the normal controls. Functional analysis of SEMA5A-regulated genes revealed that they were involved in cellular growth and proliferation. The overexpression of SEMA5A in A549 and H1299 cells significantly decreased the proliferation (P<0.01), colony formation (P<0.001) and migratory ability (P<0.01) of the cells. The suppressive effects of SEMA5A on the proliferative and migratory ability of the cells were also observed in both in vitro and in vivo experiments using brain metastatic Bm7 lung adenocarcinoma cells. On the whole, the findings of this study suggest a suppressive role for SEMA5A in lung adenocarcinoma involving the inhibition of the proliferation and migration of lung transformed cells.

Identification of Methylation-Driven, Differentially Expressed STXBP6 as a Novel Biomarker in Lung Adenocarcinoma

DNA methylation is an essential epigenetic marker associated with the silencing of gene expression. Although various genome-wide studies revealed aberrantly methylated gene targets as molecular biomarkers for early detection, the survival rate of lung cancer patients is still poor. In order to identify methylation-driven biomarkers, genome-wide changes in DNA methylation and differential expression in 32 pairs of lung adenocarcinoma and adjacent normal lung tissue in non-smoking women were examined. This concurrent analysis identified 21 negatively correlated probes (r ≤ −0.5), corresponding to 17 genes. Examining the endogenous expression in lung cancer cell lines, five of the genes were found to be significantly down-regulated. Furthermore, in tumor cells alone, 5-aza-2′-deoxycytidine treatment increased the expression levels of STXBP6 in a dose dependent manner and pyrosequencing showed higher percentage of methylation in STXBP6 promoter. Functional analysis revealed that overexpressed STXBP6 in A549 and H1299 cells significantly decreased cell proliferation, colony formation, and migration, and increased apoptosis. Finally, significantly lower survival rates (P < 0.05) were observed when expression levels of STXBP6 were low. Our results provide a basis for the genetic etiology of lung adenocarcinoma by demonstrating the possible role of hypermethylation of STXBP6 in poor clinical outcomes in lung cancer patients.