DDX3 interacts with USP9X and participates in deubiquitination of the anti-apoptotic protein MCL1

Here, we describe a novel interaction between the RNA helicase DDX3 and the deubiquitinase ubiquitin-specific peptidase 9 X-linked (USP9X) in human cells. Domain mapping studies reveal that the C-terminal region of DDX3 interacted with the N terminus of USP9X. USP9X was predominantly localized in the cytoplasm where the interaction between DDX3 and USP9X occurred. USP9X was not visibly enriched in cytoplasmic stress granules (SGs) under oxidative stress conditions, whereas overexpression of GFP-DDX3 induced SG formation and recruited USP9X to SGs in HeLa cells. Luciferase reporter assays showed that depletion of USP9X had no significant effect on DDX3-mediated translation. Given that DDX3 is not ubiquitinated upon ubiquitin overexpression, it is unlikely that DDX3 serves as a substrate of USP9X. Importantly, we found that ubiquitinated MCL1 was accumulated upon depletion of USP9X and/or DDX3 in MG132-treated cells, suggesting that USP9X and DDX3 play a role in regulating MCL1 protein stability and anti-apoptotic function. This study indicates that DDX3 exerts anti-apoptotic effects probably by coordinating with USP9X in promoting MCL1 deubiquitination.

Recurrent intracranial neurenteric cyst with malignant transformation: A case report and literature review

Neurenteric cysts (NCs) are uncommon congenital cystic lesions. Malignantly transformed NCs are extremely rare. The present study reports the case of a recurrent foramen magnum NC with a malignant transformation and reviews 8 previously reported cases. A 58-year-old woman with a 5-month history of occasional headaches, dizziness and vomiting presented to the Beijing Tiantan Hospital (Beijing, China) with palsy of the left cranial IX and X nerves, decreased sensation in the limbs on the right side and an ataxic gait. Magnetic resonance imaging (MRI) scans revealed a cystic mass in the left side of the foramen magnum, positioned anteriolaterally to the medulla oblongata. Surgery using a left suboccipital retrosigmoid approach was performed. The lesion was partially resected and was histopathologically diagnosed as an NC with focal hyperplasia of the epithelial cells. Additional MRI scans that were performed 25 months later revealed a solid lesion posterior to the medullar oblongata. Therefore, surgery using a suboccipital midline approach was performed. The solid lesion was sub-totally removed and was histopathologically diagnosed as a well-differentiated papillary adenocarcinoma. At 1 month post-surgery, the patient's condition worsened, eventually resulting in mortality due to respiratory failure. Based on the findings of the present case and previous literature, strict criteria for malignant-transformed NCs were created. The location distribution of malignant-transformed NCs does not coincide with the location distribution of all NCs, and malignantly transformed NCs usually occur in adult patients and present as atypical radiological features. Surgery is the optimal treatment for malignantly transformed NCs, and the effectiveness of adjuvant therapy requires additional studies.

BRCA1 regulates insulin-like growth factor 1 receptor levels in ovarian cancer

Breast cancer 1 (BRCA1) and insulin-like growth factor 1 receptor (IGF1R) are critical in ovarian cancer progression. However, the crosstalk between the BRCA1 and IGF1R signaling pathways in ovarian cancer remains largely unknown. The effects of BRCA1 on IGF1R were assessed in 121 serous ovarian cancer patients (BRCA1 mutation, n=30; non-BRCA1 mutation, n=32; hypermethylated BRCA1 promoter, n=28; and non-methylation, n=31). BRCA1 promoter methylation was analyzed via bisulfite sequencing using primers focused on the core promoter region. The expression levels of BRCA1 and IGF1R were assessed by immunohistochemistry and real-time polymerase chain reaction. Knockdown and overexpression of BRCA1 were achieved using a lentiviral vector in 293T and SKOV3 ovarian cancer cells, and primary non-mutated and BRCA1-mutated ovarian cancer cells. The present study demonstrated that IGF1R expression is increased in non-BRCA1-mutated ovarian cancer when compared with adjacent normal tissue. Furthermore, IGF1R levels are additionally significantly elevated in BRCA1 inactivation ovarian cancer (BRCA1 mutation or hypermethylated BRCA1 promoter). In addition, BRCA1 knockdown was found to be an effective method of activating IGF1R expression in non-BRCA1-mutated ovarian cancer cells. The observations of the current study indicate that BRCA1 may be a potential trigger that is involved in the transcriptional regulation of IGF1R in the development of ovarian cancer.