Knockdown of CDC2 expression inhibits proliferation, enhances apoptosis, and increases chemosensitivity to temozolomide in glioblastoma cells

Policosanol suppresses tumor progression in a gastric cancer xenograft model

Gastric cancer (GC) is the most common cancer worldwide and the third leading cause of cancer death, with the fifth highest incidence. The development of effective chemotherapeutic agents is needed to decrease GC mortality. Policosanol (PC) extracted from Cuban sugar cane wax is a healthy functional food ingredient that helps improve blood cholesterol levels and blood pressure. Its various physiological activities, such as antioxidant, anti-inflammatory, and anticancer activities, have been reported recently. Nevertheless, the therapeutic efficacy of PC in gastric xenograft models is unclear. We aimed to investigate the anticancer effect of PC on human GC SNU-16 cells and a xenograft mouse model. PC significantly inhibited GC cell viability and delayed tumor growth without toxicity in the SNU-16-derived xenograft model. Therefore, we investigated protein expression levels in tumor tissues; the expression levels of Ki-67, a proliferation marker, and cdc2 were decreased. In addition, we performed proteomic analysis and found thirteen differentially expressed proteins. Our results suggested that PC inhibited GC progression via cdc2 suppression and extracellular matrix protein regulation. Notably, our findings might contribute to the development of novel and effective therapeutic strategies for GC.

OUP accepted manuscript

BACKGROUND

Glioblastoma stem cells (GSCs) and their interplay with tumor-associated macrophages (TAMs) are responsible for malignant growth and tumor recurrence of glioblastoma multiforme (GBM), but the underlying mechanisms are largely unknown.

METHODS

Cell viability, stemness, migration, and invasion were measured in GSCs after the knockdown of upstream stimulating factor 1 (USF1). Luciferase assay and chromatin immunoprecipitation qPCR were performed to determine the regulation of CD90 by USF1. Immunohistochemistry and immunofluorescent staining were used to examine the expression of USF1 and GSC markers, as well as the crosstalk between GSCs and TAMs. In addition, the interaction between GSCs and TAMs was confirmed using in vivo GBM models.

RESULTS

We show that USF1 promotes malignant glioblastoma phenotypes and GSCs-TAMs physical interaction by inducing CD90 expression. USF1 predicts a poor prognosis for glioma patients and is upregulated in patient-derived GSCs and glioblastoma cell lines. USF1 overexpression increases the proliferation, invasion, and neurosphere formation of GSCs and glioblastoma cell lines, while USF1 knockdown exerts an opposite effect. Further mechanistic studies reveal that USF1 promotes GSC stemness by directly regulating CD90 expression. Importantly, CD90 of GSCs functions as an anchor for physical interaction with macrophages. Additionally, the USF1/CD90 signaling axis supports the GSCs and TAMs adhesion and immunosuppressive feature of TAMs, which in turn enhance the stemness of GSCs. Moreover, the overexpression of CD90 restores the stemness property in USF1 knockdown GSCs and its immunosuppressive microenvironment.

CONCLUSIONS

Our findings indicate that the USF1/CD90 axis might be a potential therapeutic target for the treatment of glioblastoma.

CDK1 is up-regulated by temozolomide in an NF-κB dependent manner in glioblastoma

The alkylating agent, temozolomide (TMZ), is the most commonly used chemotherapeutic for the treatment of glioblastoma (GBM). The anti-glioma effect of TMZ involves a complex response that includes G2-M cell cycle arrest and cyclin-dependent kinase 1 (CDK1) activation. While CDK1 phosphorylation is a well-described consequence of TMZ treatment, we find that TMZ also robustly induces CDK1 expression. Analysis of this pathway demonstrates that CDK1 is regulated by NF-κB via a putative κB-site in its proximal promoter. CDK1 was induced in a manner dependent on mature p50 and the atypical inhibitor κB protein, BCL-3. Treatment with TMZ induced binding of NF-κB to the κB-site as assessed by gel shift analysis and chromatin immunoprecipitation. Examination of a CDK1 promoter-reporter demonstrated the functional relevance of the κB-site and underlined the requirement of p50 and BCL-3 for activation. Targeted knockdown of CDK1 or chemical inhibition with the selective CDK1 inhibitor, RO-3306, potentiated the cytotoxic effect of TMZ. These results identify CDK1 as an NF-κB target gene regulated by p50 and BCL-3 and suggest that targeting CDK1 may be a strategy to improve the efficacy of TMZ against GBM.

Accumulation of cytoplasmic Cdk1 is associated with cancer growth and survival rate in epithelial ovarian cancer

Cyclin dependent kinase 1 (Cdk1) have previously reported correlation with cancer growth and a key regulator for cell cycle. Mostly, Cdk1′s function of nucleus for cell cycle is well known to be associated with cancer, but cytoplasmic Cdk1′s traits are not clearly identified, yet. We revealed that tissue microarray blocks of epithelial ovarian cancer (n = 249) showed increased level of cytoplasmic Cdk1 (p < 0.001), but not in nucleus (p = 0.192) of histologic cell type independently. On survival analysis, Cdk1 overexpression conferred a significantly worse prognosis in 5-year overall survival (Log-rank p = 0.028, Hazard ratio = 2.016, 95% CI = 1.097 to 4.635). Also, the expression of Cdk1 was increased in ovarian cancer cell lines and Gene Expression Omnibus datasets. When the expression and activity of Cdk1 were inhibited by si-Cdk1 or RO-3306 which is a potent Cdk1 inhibitor, the growth of ovarian cancer was diminished. Moreover, combined treatment with RO-3306 and cisplatin in ovarian cancer significantly elevated anti-cancer effects than single-agent treatment. In conclusion, cytoplasmic Cdk1 expression which was elevated in ovarian cancer predicts a poor overall survival. The inhibition of Cdk1 expression and activity reduced ovarian cancer growth.

Astrocytes protect glioma cells from chemotherapy and upregulate survival genes via gap junctional communication

Gliomas are the most common type of primary brain tumor. Using current standard treatment regimens, the prognosis of patients with gliomas remains poor, which is predominantly due to the resistance of glioma cells to chemotherapy. The organ microenvironment has been implicated in the pathogenesis and survival of tumor cells. Thus, the aim of the present study was to test the hypothesis that astrocytes (the housekeeping cells of the brain microenvironment) may protect glioma cells from chemotherapy and to investigate the underlying mechanism. Immunofluorescent and scanning electron microscopy demonstrated that glioma cells were surrounded and infiltrated by activated astrocytes. In vitro co-culture of glioma cells with astrocytes significantly reduced the cytotoxic effects on glioma cells caused by various chemotherapeutic agents, as demonstrated by fluorescein isothiocyanate-propidium iodide flow cytometry. Transwell experiments indicated that this protective effect was dependent on physical contact and the gap junctional communication (GJC) between astrocytes and glioma cells. Microarray expression profiling further revealed that astrocytes upregulated the expression levels of various critical survival genes in the glioma cells via GJC. The results of the present study indicated that the organ microenvironment may affect the biological behavior of tumor cells and suggest a novel mechanism of resistance in glioma cells, which may be of therapeutic relevance clinically.