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RAD18 is an E3 ubiquitin‑protein ligase that has a role in carcinogenesis and tumor progression owing to its involvement in error‑prone replication. Despite its significance, the function of RAD18 has not been fully examined in colorectal cancer (CRC). In the present research, by collecting clinical samples and conducting immunohistochemical staining, we found that RAD18 expression was significantly increased in the CRC tissue compared with that noted in the adjacent non‑cancerous normal tissues and that high expression of RAD18 was associated with lymph node metastasis and poor prognosis in CRC patients. In vitro, as determined by cell transfection, scratch, and Transwell experiments, it was also demonstrated that RAD18 increased the invasiveness and migration capacity of CRC cells (HCT116, DLD‑1, SW480). The signaling pathway was analyzed by western blotting and the clinical data were analyzed by immunohistochemical staining and RT‑PCR, indicating that the process of epithelial‑mesenchymal transition (EMT) may be involved in RAD18‑mediated migration and invasion of CRC cells. All of the above data indicate that RAD18 is a novel prognostic biomarker that may become a potential therapeutic target for CRC in the future.

The E3 ubiquitin ligase RAD18 has been identified as an oncoprotein that exhibits prometastatic properties in various types of cancer; however, the role of RAD18 in cervical cancer (CC) remains unclear. In the present study, it was revealed that increased expression of RAD18 was associated with worse prognosis of patients with CC. Knockdown of endogenous RAD18 suppressed the motility and invasiveness of CC cells, as evaluated by Transwell assays. mRNA sequencing revealed that silencing RAD18 altered the expression profile of proinflammatory mediators, such as interleukin‑1β (IL‑1β). Furthermore, exogenous IL‑1β treatment rescued RAD18‑mediated CC cell invasion. These findings indicated an underlying mechanism via which RAD18 promotes CC progression, suggesting that RAD18 may be a potential biomarker and therapeutic target for malignant CC.

Neoadjuvant chemoradiotherapy (nCRT) has been widely applied to improve the local control rate and survival rate in patients with locally advanced rectal cancer (LARC), yet only part of LARC patients would benefit from nCRT. Therefore, it is imperative to predict the therapeutic outcome of nCRT. Here, we showed that RAD18, an E3 ubiquitin-linked enzyme, played a fundamental role in predicting the response of LARC patients to nCRT. According to clinical data, patients with low RAD18 expression level in their pre-nCRT biopsies had a superior response to nCRT compared to those with high RAD18 expression. Inhibition of RAD18 expression in rectal cancer cells pronouncedly attenuated the proliferation and promoted apoptosis after exposing to irradiation or/and 5-fluorouracil (5-Fu). Downregulated RAD18 levels increased cell apoptosis by activating caspase-9-caspase-3-mediated apoptotic pathway, thus resulting in the enhancement of cell radiosensitivity and 5-Fu susceptibility. Furthermore, a xenograft nude mouse model showed that silencing RAD18 significantly slowed tumor growth after irradiation or/and 5-Fu in vivo. Collectively, these results implied that RAD18 could be a new biomarker to predict LARC patients who might benefit from nCRT and provide new strategies for clinical treatment of LARC., (© 2019 The Authors. Cancer Medicine published by John Wiley & Sons Ltd.)

As a key regulator of DNA translesion synthesis (TLS) pathway, RAD18 is error-prone and contributes to the accumulation of DNA mutations. We have recently shown that RAD18 is overexpressed in human esophageal squamous cell cancer (ESCC) and acts to promote ESCC progression. The current study aims to understand the molecular mechanism by which RAD18 enhances the invasiveness and metastasis of ESCC cells. We found that RAD18 expression is markedly higher in high T stage ESCCs compared to low T stage groups. Kaplan-Meier analysis showed an inverse correlation between RAD18 expression and patient prognosis. The expression of matrix metalloproteinase-2 (MMP-2) and matrix metalloproteinase-9 (MMP-9), two vital mediators of cell invasion and proliferation, positively correlated with RAD18 expression in ESCC tissues. Ectopic expression of RAD18 enhanced the motility and invasiveness of ESCC cells as evaluated by wound-healing assays and transwell assays. A xenograft nude mouse model showed that RAD18 promoted the colonization of ESCC cells in vivo. Signaling pathway analysis identified the JNK-MMP cascade as a mediator of RAD18-induced enhancement of ESCC progression. These data demonstrate the underlying mechanism by which RAD18 promotes ESCC progression, suggesting that RAD18 is a promising novel prognostic biomarker and therapeutic target against ESCC., (Copyright © 2018 Elsevier B.V. All rights reserved.)

Objective: To investigate the effect of RAD18-siRNA on cell proliferation and chemotherapy sensitivity of esophageal squamous cell carcinoma (ESCC) ECA-109 cells. Methods: RAD18-siRNA was transfected into human ECA-109 cells by Lipofectamine 3000. Quantitative PCR and Western blot were performed to detect RAD18 and CyclinD1 expression; CCK-8 assay was used to determine cell proliferation and chemotherapy drug sensitivity; flow cytometry was used to determine cell cycle. Correlation between RAD18 and CyclinD1 mRNA expression was analyzed by Pearson's correlation. Results: Compared with non-transfected cells, the expression of RAD18 in RAD18-siRNA group was significantly decreased ( P <0.05). The cell proliferation was inhibited ( P <0.05) and the cell number of G1 phase was increased, G2/M phase cells decreased ( P <0.05) in RAD18-siRNA group. After treatment with different concentrations of cisplatin or 5-FU, the survival rate of the two cell groups was reduced (all P <0.05), and the IC50 of RAD18-siRNA group was significantly lower than that of non-transfected group ( P <0.05). The mRNA expression of RAD18 was positively correlated with CyclinD1 expression in ESCC tissues( r =0.478, P <0.01). Conclusion: Down-regulated expression of RAD18 can decrease the cell proliferation and increase chemo-sensitivity of ESCC cells, and CyclinD1 may participate in the process.

Protein reversionless 3-like (REV3L), the catalytic subunit of DNA polymerase (pol) ζ, is well known to participate in error-prone translesion synthesis (TLS) with less stringent and lower processivity. Recent evidence has demonstrated that REV3L is involved in carcinogenesis and tumor progression. However, the function of REV3L remains unclear in esophageal squamous cell carcinoma (ESCC). In the present study, we examined REV3L expression in ESCC tissues and its association with clinicopathological parameters. REV3L was found to be significantly upregulated and correlated with lymph node metastasis and clinical stage in the ESCC tissues. To further investigate the potential role of REV3L in esophageal cancer, stable ESCC cell lines with suppression of REV3L expression were established. Downregulation of REV3L expression led to a decrease in cell proliferation and invasive capacity partly through suppression of cyclin D1 and survivin expression, and an increase in cellular sensitivity to 5-fluorouracil (5-FU) by induction of G1 phase arrest and apoptosis. Therefore, REV3L plays an important role in ESCC progression and chemoresistance, and is a potential diagnostic marker and therapeutic target for ESCC.

Lung cancer remains the leading cause of cancer-related mortality worldwide and non-small cell lung cancer (NSCLC) accounts for approximately 80-85% of all cases of lung cancer. Cisplatin plays a significant role in the management of human lung cancer. Translesion DNA synthesis (TLS) is involved in DNA damage repair. DNA polymerase ζ (Pol ζ) is able to mediate the DNA replication bypass of DNA damage, which is suggested to be involved in chemoresistance. REV3L is the catalytic subunit of Pol ζ. Due to its critical role in translesion DNA synthesis, whether REV3L modulates cisplatin response in NSCLC cells remains unknown. In this study, REV3L overexpression and silencing H1299 cell lines were established. The reports showed that cisplatin induced the expression of REV3L by recruiting Sp1 to its promoter. Similar results were obtained when the ability of the cells to express luciferase from a platinated plasmid was measured. Co-transfection of the reporter with the REV3L overexpression vector or REV3L plus REV7L significantly enhanced the reporter activity. Nuclear condensation and fragmentation of shRNA-REV3L H1299 cells were more pronounced than shRNA-NC H1299 cells after cisplatin exposure, indicating that REV3L overexpression abolished cisplatin-induced DNA damage. Moreover, a forced expression of REV3L conferred the resistance of H1299 cells to cisplatin, whereas the knockdown of REV3L sensitized cisplatin efficacy in H1299 cells. Taken together, we demonstrated that inhibition of REV3L sensitized lung cancer H1299 cells to cisplatin treatment. Thus, REV3L may be a novel target for the chemotherapy of NSCLC.