ABSTRACT
Oral cancer is one of the highest-incidence malignancies worldwide, with the occurrence of oral squamous cell carcinoma (OSCC) being the most frequently diagnosed form. A barrier for oral cancer management may arise from tumor cells that possess properties of cancer stemness, which has been recognized as a crucial factor in tumor recurrence and metastasis. As such, understanding the molecular mechanisms underlying these tumor cells may provide insights for improving cancer treatment. MRE11 is the core protein of the RAD50/MRE11/NBS1 complex with a primary role in DNA damage repair, and it has been diversely associated with tumor development including OSCC. In this study, we aimed to investigate the engagement of CD44, a cancer stemness marker functioning in the control of cell growth and motility, in OSCC malignancy under the influence of MRE11. We found that overexpression of MRE11 enhanced CD44 expression and tumorsphere formation in OSCC cells, whereas knockdown of MRE11 reduced these phenomena. In addition, the MRE11-promoted tumorsphere formation or cell migration ability was compromised in OSCC cells carrying siRNA that targets CD44, as was the MRE11-promoted AKT phosphorylation. These were further supported by analyzing clinical samples, where higher CD44 expression was associated with lymph node metastasis. Additionally, a positive correlation between the expression of MRE11 and CD44, or that of CD44 and phosphorylated AKT, was observed in OSCC tumor tissues. Finally, the expression of CD44 was found to be higher in the metastatic lung nodules from mice receiving tail vein-injection with MRE11-overexpressing OSCC cells compared with control mice, and a positive correlation between CD44 and phosphorylated AKT was also observed in these metastatic lung nodules. Altogether, our current study revealed a previously unidentified mechanism linking CD44 and AKT in MRE11-promoted OSCC malignancy, which may shed light to the development of novel therapeutic strategies in consideration of this new pathway in OSCC.
ABSTRACT
MRE11, the nuclease component of RAD50/MRE11/NBS1 DNA repair complex which is essential for repair of DNA double-strand-breaks in normal cells, has recently garnered attention as a critical factor in solid tumor development. Herein we report the crucial role of MRE11 in oral cancer progression in a nuclease-independent manner and delineate its key downstream effectors including CXCR4. MRE11 expression in oral cancer samples was positively associated with tumor size, cancer stage and lymph node metastasis, and was predictive of poorer patient survival and radiotherapy resistance. MRE11 promoted cell proliferation/migration/invasion in a nuclease-independent manner but enhanced radioresistance via a nuclease-dependent pathway. The nuclease independent promotion of EMT and metastasis was mediated by RUNX2, CXCR4, AKT, and FOXA2, while CXCR4 neutralizing antibody mitigated these effects in vitro and in vivo. Collectively, MRE11 may serve as a crucial prognostic factor and therapeutic target in oral cancer, displaying dual nuclease dependent and independent roles that permit separate targeting of tumor vulnerabilities in oral cancer treatment.
Subject(s)
Core Binding Factor Alpha 1 Subunit/metabolism , DNA Repair Enzymes/metabolism , Deoxyribonucleases/metabolism , Hepatocyte Nuclear Factor 3-beta/metabolism , MRE11 Homologue Protein/metabolism , Mouth Neoplasms/metabolism , Receptors, CXCR4/metabolism , Animals , Cell Line, Tumor , Cell Movement/physiology , Cell Proliferation/physiology , Female , Heterografts , Humans , MRE11 Homologue Protein/genetics , Male , Mice , Mice, Inbred NOD , Mice, SCID , Mouth Neoplasms/genetics , Mouth Neoplasms/pathology , Mouth Neoplasms/radiotherapy , Prognosis , Proto-Oncogene Proteins c-akt/metabolism , Radiation Tolerance , Signal Transduction , Survival Rate , ZebrafishABSTRACT
BACKGROUND: Oral cancer is a common cancer with a high mortality rate. While surgery is the most effective treatment for oral cancer, it frequently causes deformity and dysfunction in the orofacial region. In this study, methyl aminolevulinate photodynamic therapy (MAL-PDT) as a prevention tool against progression of precancerous lesion to oral cancer was explored. METHODS: For in vitro studies, we evaluated the effects of MAL-PDT on viability of DOK oral precancerous cells by XTT, cell morphology by TEM, and intracellular signaling pathways by flow cytometry, Western blotting, and immunofluorescence. For in vivo study, DMBA was used to induce oral precancerous lesions in hamsters followed by MAL-PDT treatment. We measured tumor size and body weight weekly. After sacrifice, buccal pouch lesions were processed for H&E stain and immunohistochemistry analysis. RESULTS: MAL-PDT induced autophagic cell death in DOK oral precancerous cells. The autophagy-related markers LC3II and p62/SQSTM1 and autophagosome formation in DOK cells were increased after MAL-PDT treatment. In vivo, Metvix® -PDT treatment decreased tumor growth and enhanced LC3II expression in hamster buccal pouch tumors induced by DMBA. CONCLUSIONS: Our in vitro and in vivo results suggest that MAL-PDT may provide an effective therapy for oral precancerous lesions through induction of autophagic cell death.
Subject(s)
Autophagy/drug effects , Mouth Neoplasms/drug therapy , Mouth Neoplasms/pathology , Photochemotherapy , Precancerous Conditions/drug therapy , Precancerous Conditions/pathology , 9,10-Dimethyl-1,2-benzanthracene , Aminolevulinic Acid/analogs & derivatives , Aminolevulinic Acid/therapeutic use , Animals , Autophagosomes , Body Weight , Cell Line, Tumor , Cell Survival/drug effects , Cricetinae , Humans , Male , Microtubule-Associated Proteins/metabolism , Photochemotherapy/methods , Photosensitizing Agents/therapeutic use , Precancerous Conditions/chemically induced , Sequestosome-1 Protein/metabolism , Signal Transduction , Tumor BurdenABSTRACT
PURPOSE: The ß-nitrostyrene family has been previously reported to possess anticancer property. However, the biological effects of ß-nitrostyrenes on ovarian cancer and the underlying mechanisms involved remain unclear. In the present study, we synthesized a ß-nitrostyrene derivative, CYT-Rx20 3'-hydroxy-4'-methoxy-ß-methyl-ß-nitrostyrene), and investigated its anticancer effects and the putative pathways of action in ovarian cancer. METHODS: The effects of CYT-Rx20 were analyzed using cell viability assay, reactive oxygen species (ROS) generation assay, FACS analysis, annexin V staining, immunostaining, comet assay, immunoblotting, soft agar assay, migration assay, nude mice xenograft study and immunohistochemistry. RESULTS: CYT-Rx20 induced cytotoxicity in ovarian cancer cells by promoting cell apoptosis via ROS generation and DNA damage. CYT-Rx20-induced cell apoptosis, ROS generation and DNA damage were reversed by thiol antioxidants. In addition, CYT-Rx20 inhibited ovarian cancer cell migration by regulating the expression of epithelial to mesenchymal transition (EMT) markers. In nude mice, CYT-Rx20 inhibited ovarian tumor growth accompanied by increased expression of DNA damage marker γH2AX and decreased expression of EMT marker Vimentin. CONCLUSIONS: CYT-Rx20 inhibits ovarian cancer cells in vitro and in vivo, and has the potential to be further developed into an anti-ovarian cancer drug clinically.