DNA damage response and its clinicopathological relationship in appendiceal tumors

Differential expression profile analysis of DNA damage repair genes in CD133+/CD133- colorectal cancer cells

The present study examined differential expression levels of DNA damage repair genes in COLO 205 colorectal cancer cells, with the aim of identifying novel biomarkers for the molecular diagnosis and treatment of colorectal cancer. COLO 205-derived cell spheres were cultured in serum-free medium supplemented with cell factors, and CD133⁺/CD133^- cells were subsequently sorted using an indirect CD133 microbead kit. In vitro differentiation and tumorigenicity assays in BABA/c nude mice were performed to determine whether the CD133⁺ cells also possessed stem cell characteristics, in addition to the COLO 205 and CD133^- cells. RNA sequencing was employed for the analysis of differential gene expression levels at the mRNA level, which was determined using reverse transcription-quantitative polymerase chain reaction. The mRNA expression levels of 43 genes varied in all three types of colon cancer cells (false discovery rate ≤0.05; fold change ≥2). Of these 43 genes, 30 were differentially expressed (8 upregulated and 22 downregulated) in the COLO 205 cells, as compared with the CD133^- cells, and 6 genes (all downregulated) were differentially expressed in the COLO 205 cells, as compared with CD133⁺ cells. A total of 18 genes (10 upregulated and 8 downregulated) were differentially expressed in the CD133^- cells, as compared with the CD133⁺ cells. By contrast, 6 genes were downregulated and none were upregulated in the CD133⁺ cells compared with the COLO 205 cells. These findings suggest that CD133⁺ cells may possess the same DNA repair capacity as COLO 205 cells. Heterogeneity in the expression profile of DNA damage repair genes was observed in COLO 205 cells, and COLO 205-derived CD133^- cells and CD133⁺ cells may therefore provide a reference for molecular diagnosis, therapeutic target selection and determination of the treatment and prognosis for colorectal cancer.

The Expression and Clinical Outcome of pCHK2-Thr68 and pCDC25C-Ser216 in Breast Cancer

Checkpoint kinase 2 (CHK2) and cell division cycle 25C (CDC25C) are two proteins involved in the DNA damage response pathway, playing essential roles in maintaining genome integrity. As one of the major hallmarks of abnormal cellular division, genomic instability occurs in most cancers. In this study, we identified the functional expression of pCHK2-Thr68 and pCDC25C-Ser216 in breast cancer, as well as its association with breast cancer survival. Tissue microarray analysis using immunohistochemistry was constructed to identify the expression of pCHK2-Thr68 and pCDC25C-Ser216 in 292 female breast cancer patients. The relationship among protein expression, clinicopathological factors (e.g., human epidermal growth factor receptor 2 (HER 2), tumor size, tumor-node-metastasis (TNM) classification), and overall survival of the breast cancer tissues were analyzed using Pearson’s χ-square (χ²) test, Fisher’s exact test, multivariate logistic regression and Kaplan–Meier survival analysis. Significantly higher expressions of pCHK2-Thr68 and pCDC25C-Ser216 were observed in the nucleus of the breast cancer cells compared to the paracancerous tissue (pCHK2-Thr68, 20.38% vs. 0%; pCDC25C-Ser216, 82.26% vs. 24.24%). The expression of pCHK2-Thr68 and pCDC25C-Ser216 in breast cancer showed a positive linear correlation (p = 0.026). High expression of pCHK2-Thr68 was associated with decreased patient survival (p = 0.001), but was not an independent prognostic factor. Our results suggest that pCHK2-Thr68 and pCDC25C-Ser216 play important roles in breast cancer and may be potential treatment targets.