Accumulating evidence shows that elevated levels of reactive oxygen species (ROS) are associated with cancer initiation, growth, and response to therapies. As concentrations increase, ROS influence cancer development in a paradoxical way, either triggering tumorigenesis and supporting the proliferation of cancer cells at moderate levels of ROS or causing cancer cell death at high levels of ROS. Thus, ROS can be considered an attractive target for therapy of cancer and two apparently contradictory but virtually complementary therapeutic strategies for the regulation of ROS to treat cancer. Despite tremendous resources being invested in prevention and treatment for cancer, cancer remains a leading cause of human deaths and brings a heavy burden to humans worldwide. Chemotherapy remains the key treatment for cancer therapy, but it produces harmful side effects. Meanwhile, the process of de novo development of new anticancer drugs generally needs increasing cost, long development cycle, and high risk of failure. The use of ROS‐based repurposed drugs may be one of the promising ways to overcome current cancer treatment challenges. In this review, we briefly introduce the source and regulation of ROS and then focus on the status of repurposed drugs based on ROS regulation for cancer therapy and propose the challenges and direction of ROS‐mediated cancer treatment.

Neddylation is a process in which a ubiquitin-like molecule NEDD8 is conjugated to a lysine residue of the substrate protein via successive enzymatic cascade reactions. Inactivation of neddylation pathway triggers tumor cell apoptosis or senescence to suppress the tumor growth. So far, there has been limited research on the role of the neddylation pathway (NEDD8-UBE2M-RBX1 axis) in the immune response. In this study, we investigated the association between the neddylation pathway and immune function in HCC by comprehensively analyzing transcriptome and clinical data of HCC samples from TCGA database. The analysis showed that the mRNA expression of neddylation pathway components was up-regulated in HCC and increased with disease severity. Moreover, we observed that activated neddylation pathway was associated with enriched infiltration of T helper 2 (Th2) cells in HCC, while transactivation of STAT5A signaling may mediate this association. On the contrary, no significant correlation between the neddylation pathway and Th1 cells infiltration was identified. Taken together, these findings suggest a potential role of the neddylation pathway in promoting a shift in Th1/Th2 balance toward Th2-dominant immunosuppression. Hence, targeting neddylation pathway could serve as an attractive immunotherapy strategy for suppressing the development of Th2 cells.

Immunosuppressive cells play important roles in generating an immunosuppressive tumor microenvironment and facilitating tumor immune escape. However, the molecular mechanisms underlying their immunosuppressive effects remain unclear. UBA3, the sole catalytic subunit of the neural precursor cell expressed developmentally down-regulated protein 8 (NEDD8)-activating enzyme E1, is highly expressed in various human malignancies, along with an activated neddylation pathway. In this study, we investigated the relationships between the UBA3-dependent neddylation pathway and the infiltration of several immunosuppressive cell populations in lung adenocarcinoma (LUAD). We explored the regulatory mechanisms of UBA3 in LUAD cells by using mRNA sequencing and functional enrichment analyses. Correlations between neddylation and immune infiltrates were assessed by Western blotting, real-time PCR, and analyses of public databases. We found elevated levels of UBA3 expression in LUAD tissues compared to adjacent normal tissues. Blocking UBA3 and the neddylation pathway promoted the accumulation of the phosphorylated nuclear factor of kappa light polypeptide gene enhancer in B-cells inhibitor (p-IκBα), inhibiting the gene expression of tumor cell-derived cytokines such as C–C motif chemokine ligand (CCL) 2, C-X-C motif ligand (CXCL)1, CXCL2, colony-stimulating factor (CSF) 1, CSF2 interleukin (IL)-6, and IL-1B. Moreover, the overexpression of UBA3 in LUAD cells was associated with the secretion of these cytokines, and the recruitment and infiltration of immunosuppressive cells including tumor-associated macrophages (TAMs), plasmacytoid dendritic cells (pDCs), Th2 cells and T-regulatory cells (Tregs). This could facilitate the tumor immune escape and malignant progression of LUAD. Our findings provide new insights into the role of UBA3 in establishing an immunosuppressive tumor microenvironment by modulating nuclear factor kappa B (NF-кB) signaling and the neddylation pathway.

Background: Malignant tumor cells often develop metastatic nodules at distant organs through circulation in blood flow and result in poor prognosis. Detection of circulating tumor cells (CTCs) is clinically an important issue to evaluate the metastatic potential of primary tumors in cancer patients. Furthermore, confirmation of genetic alterations in CTCs provides us the critical information to clarify the molecular mechanism in the acquisition of metastatic capability of tumor cells and to treat tumor metastasis by molecular targeted therapy. We recently developed a telomerase-specific replication-selective adenovirus (OBP-401; TelomeScan) expressing the green fluorescence protein (GFP). OBP-401-mediated GFP induction method was a simple and highly sensitive imaging system to detect a small population of viable CTCs in the peripheral blood. In this study, we assessed the potential of OBP-401-mediated CTC detection system to analyze the genetic alterations in CTCs. Methods: We used two types of human colon cancer cell lines SW480 and HCT116 that have the mutations in codon 12 and 13, respectively, of the K-ras gene. The detection method involved a 4-step procedure, including the lysis of red blood cells, the subsequent addition of OBP-401 to the cell pellets, the isolation of GFP-positive tumor cells using a fluorescence-activated cell sorting (FACS), and a confirmation of genetic mutations by direct sequencing. DNA was extracted from the captured cells using FACS and we investigated the mutation status in the K-ras gene by direct sequencing. Results: When only 10 cells of SW480 or HCT116 cells were added in a 5 ml of blood obtained from healthy volunteer, a total of 2-12 GFP-positive cells were captured from OBP-401-infected blood samples using FACS Aria. We confirmed the mutations in codon 12 and 13 of the K-ras gene in the FACS-captured cells from blood samples containing SW480 and HCT116 cells, respectively, by direct sequencing. Conclusion: These results suggest that OBP-401-mediated GFP induction and FACS-based capture system are useful methods to isolate small population of CTCs from peripheral blood samples and to evaluate the genetic alterations in CTCs. The combination method using OBP-401 and FACS would be a reliable strategy for the surveillance of genetic alterations in CTCs. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 2385. doi:1538-7445.AM2012-2385