Identification Of Natural Compound Derivative For Inhibition Of XLF And Overcoming Chemoresistance In Colorectal Cancer Cells

Current status and prospect of the DNA double-strand break repair pathway in colorectal cancer development and treatment

Colorectal cancer (CRC) is one of the most common malignancies worldwide. Double-strand break (DSB) is the most severe type of DNA damage. However, few reviews have thoroughly examined the involvement of DSB in CRC. Latest researches demonstrated that DSB repair plays an important role in CRC. For example, DSB-related genes such as BRCA1, Ku-70 and DNA polymerase theta (POLQ) are associated with the occurrence of CRC, and POLQ even showed to affect the prognosis and resistance for radiotherapy in CRC. This review comprehensively summarizes the DSB role in CRC, explores the mechanisms and discusses the association with CRC treatment. Four pathways for DSB have been demonstrated. 1. Nonhomologous end joining (NHEJ) is the major pathway. Its core genes including Ku70 and Ku80 bind to broken ends and recruit repair factors to form a complex that mediates the connection of DNA breaks. 2. Homologous recombination (HR) is another important pathway. Its key genes including BRCA1 and BRCA2 are involved in finding, pairing, and joining broken ends, and ensure the restoration of breaks in a normal double-stranded DNA structure. 3. Single-strand annealing (SSA) pathway, and 4. POLθ-mediated end-joining (alt-EJ) is a backup pathway. This paper elucidates roles of the DSB repair pathways in CRC, which could contribute to the development of potential new treatment approaches and provide new opportunities for CRC treatment and more individualized treatment options based on therapeutic strategies targeting these DNA repair pathways.

Gigantol protects retinal pigment epithelial cells against high glucose-induced apoptosis, oxidative stress and inflammation by inhibiting MTDH-mediated NF-kB signaling pathway

OBJECTIVE

As a frequent complication of diabetes mellitus (DM), diabetic retinopathy (DR) is now one of the major causes of blindness. Recent reports have shown that retinal pigment epithelial cell (RPEC) damage plays an essential part in DR development and progression. This work intended to explore the potential effects of Gigantol on high glucose (HG)-stimulated RPEC damage and identify potential mechanisms.

METHODS

Cell viability, cell damage, and cell apoptosis were evaluated by CCK-8, lactate dehydrogenase (LDH) and flow cytometry assays. The levels of oxidative stress biomarkers and pro-inflammatory cytokines were assessed using corresponding commercial kits and ELISA. Additionally, the levels of MTDH and NF-kB signaling pathway-related proteins were detected by western blotting.

RESULTS

Gigantol dose-dependently enhanced cell viability and decreased apoptosis in HG-challenged ARPE-19 cells. Also, Gigantol notably relieved oxidative stress and inflammatory responses in ARPE-19 cells under HG conditions. Gigantol dose-dependently suppressed MTDH expression. In addition, MTDH restoration partially counteracted the protective effects of Gigantol on ARPE-19 cells subject to HG treatment. Mechanically, Gigantol inactivated the NF-kB signaling pathway, which was partly restored after MTDH overexpression.

CONCLUSION

Our findings suggested that Gigantol protected against HG-induced RPEC damage by inactivating the NF-kB signaling via MTDH inhibition, offering a potent therapeutic drug for DR treatment.

Recent Updates on Mechanisms of Resistance to 5-Fluorouracil and Reversal Strategies in Colon Cancer Treatment

5-Fluorouracil (5-FU) plus leucovorin (LV) remain as the mainstay standard adjuvant chemotherapy treatment for early stage colon cancer, and the preferred first-line option for metastatic colon cancer patients in combination with oxaliplatin in FOLFOX, or irinotecan in FOLFIRI regimens. Despite treatment success to a certain extent, the incidence of chemotherapy failure attributed to chemotherapy resistance is still reported in many patients. This resistance, which can be defined by tumor tolerance against chemotherapy, either intrinsic or acquired, is primarily driven by the dysregulation of various components in distinct pathways. In recent years, it has been established that the incidence of 5-FU resistance, akin to multidrug resistance, can be attributed to the alterations in drug transport, evasion of apoptosis, changes in the cell cycle and DNA-damage repair machinery, regulation of autophagy, epithelial-to-mesenchymal transition, cancer stem cell involvement, tumor microenvironment interactions, miRNA dysregulations, epigenetic alterations, as well as redox imbalances. Certain resistance mechanisms that are 5-FU-specific have also been ascertained to include the upregulation of thymidylate synthase, dihydropyrimidine dehydrogenase, methylenetetrahydrofolate reductase, and the downregulation of thymidine phosphorylase. Indeed, the successful modulation of these mechanisms have been the game plan of numerous studies that had employed small molecule inhibitors, plant-based small molecules, and non-coding RNA regulators to effectively reverse 5-FU resistance in colon cancer cells. It is hoped that these studies would provide fundamental knowledge to further our understanding prior developing novel drugs in the near future that would synergistically work with 5-FU to potentiate its antitumor effects and improve the patient's overall survival.

Inhibition of DNA Repair in Cancer Therapy: Toward a Multi-Target Approach

Alterations in DNA repair pathways are one of the main drivers of cancer insurgence. Nevertheless, cancer cells are more susceptible to DNA damage than normal cells and they rely on specific functional repair pathways to survive. Thanks to advances in genome sequencing, we now have a better idea of which genes are mutated in specific cancers and this prompted the development of inhibitors targeting DNA repair players involved in pathways essential for cancer cells survival. Currently, the pivotal concept is that combining the inhibition of mechanisms on which cancer cells viability depends is the most promising way to treat tumorigenesis. Numerous inhibitors have been developed and for many of them, efficacy has been demonstrated either alone or in combination with chemo or radiotherapy. In this review, we will analyze the principal pathways involved in cell cycle checkpoint and DNA repair focusing on how their alterations could predispose to cancer, then we will explore the inhibitors developed or in development specifically targeting different proteins involved in each pathway, underscoring the rationale behind their usage and how their combination and/or exploitation as adjuvants to classic therapies could help in patients clinical outcome.

Dual Targeting of Cell Growth and Phagocytosis by Erianin for Human Colorectal Cancer

Objective

To investigate the effect of erianin on tumor growth and immune response in human colorectal cancer cells (CRC).

Methods

The effect of erianin on tumor growth was determined by CCK8 and colony formation assay. Western blotting was used to evaluate the expression levels of relevant proteins and qRT-PCR was used to evaluate the mRNA level of the relevant gene. The transcriptional activity of β-catenin was determined by dual-luciferase reporter assay. Cellular thermal shift assay was used to quantify drug–target interactions. The cell surface CD47 was assessed by flow cytometry. The enrichment of H3K27 acetyl marks on CD47 promoter was evaluated by chromatin immunoprecipitation assay. Phagocytosis assay was used to determine the phagocytic activity of macrophage. In vivo role of erianin was studied on xenograft models.

Results

We found that erianin significantly decreased cell survival, colony formation, induced cell cycle arrest, and led to cell apoptosis in SW480 and HCT116 cells. Mechanism analysis demonstrated that erianin inhibited the nuclear translocation and transcriptional activity of β-catenin, which might result from erianin-β-catenin interaction. In addition, the downstream gene expressions, such as c-Myc and cyclin D1, was decreased. More interestingly, erianin decreased the expression of CD47 by regulating H3K27 acetyl marks enrichment on CD47 promoter. Consequently, macrophage-mediated phagocytosis was increased. Our in vivo experiments further confirmed the inhibitory effect of erianin on tumor growth.

Conclusion

In summary, erianin could inhibit CRC cells growth and promoted phagocytosis, which suggested erianin as a potential therapeutic strategy for CRC patients.