Cancer stem cells (CSCs) are a key target for reducing tumor growth, metastasis, and recurrence. Redox status is a critical factor in the maintenance of CSCs, and the antioxidant enzyme Peroxiredoxin 2 (Prdx2) plays an important role in the development of colon cancer. Therefore, we investigated the contribution of Prdx2 to the maintenance of stemness of colon CSCs. Here, we used short-hairpin RNAs and a Prdx2-overexpression vector to determine the effects of Prdx2. We demonstrated that knockdown of Prdx2 reduced the self-renewal and sphere formation and resulted in increased 5-FU-induced apoptosis in human colon CSCs. Prdx2 overexpression induced reversion of the self-renewal and sphere formation. Furthermore, the effects of Prdx2 resulted in an altered expression of stemness associated with the Hh/Gli1 signaling pathway. Finally, knockdown of Prdx2 in CD133+ cells reduced the volume of xenograft tumors in BALB/c-nu mice. Taken together, colon CSCs overexpress Prdx2, which promotes their stem cell properties via the Hh/Gli1 signaling pathway. The results suggest that Prdx2 may be an effective therapeutic target for the elimination of CSCs in colorectal cancer.

Studies investigating association between tumor necrosis factor (TNF) gene polymorphisms and silicosis susceptibility report conflicting results. The aim of this meta-analysis was to assess association between TNF gene polymorphisms and silicosis susceptibility. A systematic literature search was conducted to find relevant studies. Pooled odds ratios (ORs) with 95% confidence intervals (CIs) were used to estimate the strength of association. Finally, a total of 12 articles, involving 1990 silicosis patients and 1898 healthy controls were included in the meta-analysis. Overall, meta-analysis revealed a significant association between the TNF −308A allele and silicosis (OR = 1.348, 95%CI = 1.156–1.570, P<0.001). A significant association of AA+AG genotype of the TNF −308 A/G polymorphism with susceptibility to silicosis was also found (OR = 1.466, 95%CI = 1.226–1.753, P<0.001). After stratification by ethnicity, significant associations were detected under the genetic models (A allele and AA+AG genotype) for TNF −308A/G polymorphisms in the Asian population (P<0.05). Similarly, meta-analysis of the TNF −238A/G polymorphism revealed the same pattern as that shown by meta-analysis of TNF −308A/G. The meta-analysis suggests that the TNF −308A/G and −238A/G polymorphisms are associated with susceptibility to silicosis, especially in Asians.

Background:A number of studies have attempted to determine the prognostic significance of proliferating cell nuclear antigen (PCNA) in patients with colorectal cancer (CRC), but the reports are controversial and inconsistent. Thus, we conducted a meta-analysis to clarify the value of PCNA in CRC prognosis.Methods:A systematic search of relevant studies was performed in 4 electronic databases including PubMed, Cochrane Library, Embase, and Web of Science until February 2018. Hazard ratios (HRs) combined with 95% confidence intervals (95% CIs) were used to evaluate the relationship of PCNA expression with overall survival (OS), cancer-specific survival (CSS), and disease-free survival (DFS).Results:A total of 1372 CRC patients in 14 studies were identified eventually in our meta-analysis. The pooled HRs demonstrated that CRC patients with high PCNA expression was significantly correlated with poor OS (HR = 1.81; 95% CI: 1.51–2.17; P = .000), CSS (HR = 1.99; 95% CI: 1.04–3.79; P = .037); but not significantly with DFS (HR = 2.48; 95% CI: 0.98–6.26; P = .055). Sensitivity analysis showed the pooled HRs for OS, CSS, and DFS were stable when the included studies were removed one by one.Conclusion:Our meta-analysis suggested that high PCNA expression was associated with poor prognosis, and it could serve as a reliable and prognostic biomarker in CRC patients. More large-scale studies are needed to further support the conclusion.

Colon cancer stem cells (CCSCs) play an important role in facilitating colon cancer occurrence, metastasis and drug resistance. The results of our previous studies confirmed that the well-studied antioxidant gene peroxiredoxin-2 (PRDX2) promotes colon cancer progression. However, the underlying function and mechanisms associated with PRDX2 remodeling in the context of CCSCs have remained poorly studied. In our present study, we demonstrated that PRDX2 is highly expressed in CD133/CD44-positive colon cancer tissues and spheroid CD133+CD44+ CCSCs. PRDX2 overexpression was shown to be closely correlated with CD133+CD44+ CCSCs in colon cancer. Furthermore, PRDX2 depletion markedly suppressed CD133+CD44+ CCSC stemness maintenance, tumor initiation, migration and invasion and liver metastasis. Furthermore, the expression of various EMT markers and Wnt/β-catenin signaling proteins was altered after PRDX2 inhibition. In addition, PRDX2 knockdown led to increased ROS production in CD133+CD44+ CCSCs, sensitizing CCSCs to oxidative stress and chemotherapy. These results suggest that PRDX2 could be a possible therapeutic target in CCSCs.

Long-term tumor-initiating cells (LT-TICs) are viewed as a quantifiable target for colon cancer therapy owing to their extensive self-renewal and tumorigenic and metastatic capacities. However, it is unknown which subpopulation of colon cancer cells contains LT-TICs. Here, based on the methods for isolating and identifying cancer stem cells (CSCs) and the functional features of LT-TICs, we aimed to identify a subpopulation of LT-TICs. Among the six cell lines assessed, our results showed that CD133 and CD44 coexpression was only detected in HCT116 and HT29 cell lines. In HCT116 and HT29 cells, CD133+CD44+ cells not only shared the extensive tumorigenic potential of LT-TICs but also functionally reproduced the behaviors of LT-TICs that drive tumor metastasis formation, suggesting that CD133+CD44+ cells are a typical representation of LT-TICs in colon cancer. Mechanistically, the enhanced capacity of CD133+CD44+ cells to drive metastasis involves the upregulated expression of Wnt-, EMT-, and metastasis-related genes in these cells. Additionally, CD133+CD44+ cells presented significant chemoresistance compared with corresponding nontumorigenic CD133-CD44- cells following exposure to oxaliplatin or 5-FU. Accordingly, CD133+CD44+ cells contained lower ROS levels than CD133-CD44- cells, and the low ROS levels in CD133+CD44+ cells were related to the enhancement of antioxidant defense systems. More importantly, CD133+CD44+ cells developed less DNA damage after exposure to chemotherapeutics than CD133-CD44- cells. In conclusion, we identified a subpopulation of LT-TICs in colon cancer.