Hypoxia Enhanced Glioblastoma Resistance to Erastin-Induced Ferroptosis by Up-Regulating GPX4 via PI3K/AKT/HIF-1α Axis

Background Glioblastoma is the deadliest type of primary brain tumor with a high rate of recurrence and treatment resistance. Hypoxia contributed much to radiotherapy resistance and chemoresistance of cancer. Ferroptosis is a nonapoptotic, oxidative cell death and identified as a potential anticancer mechanism in recent years. Erastin acts as a ferroptosis activator and shows a potential role in tumor treatment but the relationship between hypoxia and erastin resistance in glioblastoma has not been explained. This study aimed to investigate the role and underlying mechanism of hypoxia in erastin-induced ferroptosis in glioblastoma. Methods Cell proliferation and viability were determined by Cell Counting Kit-8 (CCK-8) assay, flow cytometry, TUNEL assays, and clone formation assay. Lipid peroxides level was analyzed by Malondialdehyde (MDA) assay and flow cytometry using C11-BODIPY dye. The correlation between HIF-1α and GPX4 expression was detected in data from the TCGA database and was determined by ChIP-qPCR assay and luciferase reporter assay. Subcutaneous xenograft and orthotopic xenograft models were established to test our findings in vivo. Results Hypoxia for at least 16 hours significantly suppressed erastin-induced ferroptosis by up-regulating glutathione peroxidase 4 (GPX4) expression in U87 and U251 cells. Hypoxia promotes GPX4 expression via enhancing the PI3K/AKT/HIF-1α pathway. Mechanistically, HIF-1α directly bound to the GPX4 gene promoter region and promoted GPX4 transcription. AKT inhibitor MK-2206 and HIF-1α inhibitor PX-478 could significantly reverse the effect. Besides, under normoxia, PX-478 could induce a higher lipid peroxidation level by decreasing GPX4 expression in U87 and U251 cells but cannot induced cell death directly, and it could significantly enhance the tumor cell killing effect of erastin. In vivo, combination of PX-478 and erastin had a coordinated intensification effect on anticancer activity uncovered by subcutaneous xenograft and orthotopic xenograft mouse models. Conclusions Hypoxia enhanced glioblastoma resistance to erastin-induced ferroptosis by activating PI3K/AKT/HIF-1α pathway and promoting GPX4 expression in a transcriptional regulation way. Combination therapy of PX-478 and erastin may be a potential strategy against glioblastoma.

DDRE-30. CELL-PENETRATING PEPTIDE ANTAGONIST OF CCAAT/ENHANCER BINDING PROTEIN ß DISPLAYS POTENT ANTI-GLIOBLASTOMA ACTIVITY

CCAAT/Enhancer Binding Protein Beta (C/EBPß) is a transcription factor overexpressed in glioblastoma (GBM). Mechanistically, C/EBPß is a master regulator of mesenchymal transition in GBM, and its increased expression correlates with mesenchymal differentiation and predicts poor clinical outcome. C/EBPß activity requires dimerization with co-factors such as CREB/ATF family members via leucine zipper interactions. ST101 is a novel peptide antagonist of C/EBPß currently being evaluated in a Phase 1/2 clinical study in patients with advanced unresectable and metastatic solid tumors. ST101 binds to the C/EBPß leucine zipper, thereby preventing dimer formation and inhibiting its transcriptional activity, resulting in selective tumor cell cytotoxicity. Here, we describe ST101 non-clinical anti-tumor activity against GBM. In vitro studies in T98G and U251 cells demonstrate ST101 dose-dependent impact of cell viability (EC50 of 2.2 and 1.2 μM, respectively), accompanied by significant impact on C/EBPß-mediated gene expression as determined by qPCR analysis. In contrast, normal human mononuclear and epithelial cells were not sensitive to ST101 (EC50 > 80 μM). In vivo, ST101 displayed significant anti-tumor activity in a U251 GBM subcutaneous xenograft model, resulting in 81.4% tumor growth inhibition (TGI) vs. control and undetectable tumors in 50% of animals. Following ST101 exposure tumors displayed reduced BIRC3 and ID2 gene expression, and significantly increased cleaved caspase 3 immunostaining indicative of cell death induction. In U251 tumors, subtherapeutic ST101 (< 5% TGI) in combination with temozolomide (< 5% TGI) resulted in 52.8% TGI, significantly greater than either single-agent alone. Similarly, in a temozolomide-refractory T98G GBM subcutaneous xenograft model, ST101 (41.6% TGI) in combination with TMZ (< 5% TGI) resulted in significant anti-GBM response (72.4% TGI). These data emphasize the potential of ST101 as a potent peptide therapeutic for GBM.

A miR-205-5p/GGCT/CD44 axis controls the progression of papillary thyroid cancer

Background Papillary thyroid cancer (PTC) is the most common endocrine malignancy, despite marked achieves in recent decades, the mechanisms underlying the pathogenesis and progression for PTC are incomplete. Accumulating evidence shows that γ-glutamylcyclotransferase (GGCT), an enzyme participated in glutathione homeostasis that is elevated in multiple types of tumors, represents an attractive therapeutic target. Methods Bioinformatics, immunohistochemistry (IHC), qRT-PCR and western blot (WB) assays were used to determine the elevation of GGCT in PTC. The biological functions of GGCT were examined using CCK8, wound healing and transwell assays. Subcutaneous xenograft and tail vein pulmonary metastatic mouse models were constructed to determine the effect of GGCT on tumorigenicity and metastasis in vivo. The effect of miR-205-5p on GGCT and the relationship between these two molecules were examined by dual luciferase reporter assay, RNA-RNA pull down assay as well as the rescue experiments both in vitro and in vivo. The interaction between GGCT and CD44 was assessed by co-immunoprecipitation (Co-IP) and IHC assays. Results Our results showed that GGCT expression is upregulated in PTC, correlates with more aggressive clinicopathological characteristics and worse prognosis. GGCT knockdown inhibited the cell proliferation, migratory and invasion ability of PTC cells and reduced the expression of mesenchymal markers (N-cadherin, CD44, MMP-2 and MMP9) while increased epithelial marker (E-cadherin) in PTC cells. We confirmed binding of miR-205-5p on the 3’-UTR regions of GGCT and delivery of miR-205-5p reversed the pro-malignant capacity of GGCT both in vitro and in vivo. Lastly, we found GGCT interacted with and stabilized CD44 in PTC cells. Conclusions Our findings illustrate a novel signaling pathway, miR-205-5p/GGCT/CD44, that involves in the carcinogenesis and progression of PTC. Development of miR-205-mimics or GGCT inhibitors as potential therapeutics for PTC may have remarkable applications.

Long Non-Coding RNA SNHG12 Contributes to Cisplatin Resistance by Mediating WEE1 via miR-503-5p in Cervical Cancer

Background: Emerging evidences have indicated that the aberrant expression of long noncoding RNAs (lncRNAs) was responsible for drug resistance, which represents a major obstacle for chemotherapy failure. Our previous study has showed that small nuclear RNA host gene 12 (SNHG12) was increased and contributed to cell growth and invasion in cervical cancer. In the present study, we aimed to investigate the role of the lncRNA SNHG12 in cisplatin (DDP) resistance and elucidate its underlying mechanisms in cervical cancer.Methods: The expression and prognosis of SNHG12 in cervical cancer tissues were evaluated based on bioinformatics. MTT, colony formation assay and flow cytometer were performed to detect cell viability. Further, Molecular relationships among CTD-3252C9.4, IRF1 and IFI6 were investigated via luciferase reporter assay, western blot, and qRT-PCR. Finally, subcutaneous xenograft model was established to verify our findings.Results: In the present study, we evaluated the cell apoptosis and half maximal inhibitory concentration (IC50) of cervical cancer upon DDP treatment. Mechanically, we found that SNHG12 upregulated WEE1 expression to regulate cell and DDP resistance via sponging miR-503-5p. Moreover, SNHG12 silencing inhibited the growth of DDP-resistant cervical cancer tumors in vivo. Conclusions: Taken together, our findings suggested that a SNHG12/miR-503-5p/ WEE1 axis which modulated the chemoresistance of cervical cancer cell to DDP, and provided promising targets for dealing with the chemoresistance of cervical cancer.

Therapeutic Potential of the Cyclin-Dependent Kinase Inhibitor Flavopiridol on c-Myc Overexpressing Esophageal Cancer

Tumors with elevated c-Myc expression often exhibit a highly aggressive phenotype, and c-Myc amplification has been shown to be frequent in esophageal cancer. Emerging data suggests that synthetic lethal interactions between c-Myc pathway activation and small molecules inhibition involved in cell cycle signaling can be therapeutically exploited to preferentially kill tumor cells. We therefore investigated whether exploiting elevated c-Myc expression is effective in treating esophageal cancer with the CDK inhibitor flavopiridol. We found frequent overexpression of c-Myc in human esophageal cancer cell lines and tissues. c-Myc overexpression correlated with accelerated esophageal cancer subcutaneous xenograft tumor growth. Esophageal cancer cells with elevated c-Myc expression were found preferentially more sensitive to induction of apoptosis by the CDK inhibition flavopiridol compared to esophageal cancer cells with lower c-Myc expression. In addition, we observed that flavopiridol alone or in combination with the chemotherapeutic agent nanoparticle albumin-bound paclitaxel (NPT) or in combinations with the targeted agent BMS-754807 significantly inhibited esophageal cancer cell proliferation and subcutaneous xenograft tumor growth while significantly enhancing overall mice survival. These results indicate that aggressive esophageal cancer cells with elevated c-Myc expression are sensitive to the CDK inhibitor flavopiridol, and that flavopiridol alone or in combination can be a potential therapy for c-Myc overexpressing esophageal cancer.

SMC1A promotes tumor growth in breast cancer by activation of the AKT/FOXM1/STMN1 Signaling Pathway

Background SMC1A (Structural maintenance of chromosomes 1) is overexpressed in various cancers and acts as an oncogene which has been implicated in critical biological functions (cell-cycle checkpoints regulation, cell division, and DNA repair). However, the mechanism and role of SMC1A in breast cancer are poorly understood. Methods TCGA database was utilized to explore the expression of SMC1A and the relationship between SMC1A and FOXM1 and STMN1. Subsequently, short hairpin RNA (shRNA) targeting SMC1A was used to examined the biological functions of it in MDA-MB-231 and MDA-MB-468 cells. Finally, subcutaneous xenograft model to verify the roles of SMC1A in vivo. Results In the present study, we demonstrated that SMC1A was significantly increased in breast cancer (BC) via TCGA database. Then loss and gain of function studies revealed that SMC1A contributed to BC cell survival, apoptosis, and invasion. Interestingly, we found that SMC1A triggered the AKT/FOXM1 cascade, which promoted BC cell proliferation. Furthermore, overexpression of FOXM1 abolished the inhibition of cell growth induced by SMC1A silencing in vitro. Clinically, the expression of SMC1A in BC tumor tissues is positively correlated with the expression of FOXM1. Conclusion Taken together, our findings not only enhanced our understanding of molecular mechanisms of SMC1A in BC, but also might provide a novel target for the development of therapeutic strategies.

WD40 repeat 43 mediates cell survival, proliferation, migration and invasion via vimentin in colorectal cancer

Background WD40 repeat (WDR)43 is an RNA-binding protein that belongs to the WDR domain protein family. Its biological function is largely unclear, particularly in colorectal cancer (CRC). Methods In the present study, we searched the TCGA database and found the correlation between WDR43 and CRC. Subsequently, the high expression of WDR43 in human clinical samples of CRC was validated and we further examined the biological functions of it in CRC cells. Finally, we explored potential downstream proteins or pathways and established subcutaneous xenograft model to verify our findings. Results Immunohistochemistry of 16 patient specimens confirmed that the expression of WDR43 was elevated in CRC. WDR43 knockdown was shown to increase apoptosis and inhibit the proliferation, migration and invasion of CRC cells in vitro and reduce tumorigenesis in animal models. In addition, it was found that WDR43 knockdown inhibited vimentin (VIM) expression in CRC cells and overexpression of VIM can partially reverse the effects of WDR43 both in vitro and in vivo. Conclusion In conclusion, the role of WDR43 in the occurrence and development of CRC was investigated in the present study. WDR43 may serve as a valuable biomarker and provide new options for the diagnosis and treatment of colorectal cancer.

MiR-103a promotes tumour growth and influences glucose metabolism in hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is a common and high-mortality cancer worldwide. Numerous microRNAs have crucial roles in the progression of different cancers. However, identifying the important microRNAs and the target biological function of the microRNA in HCC progression is difficult. In this study, we selected highly expressed microRNAs with different read counts as candidate microRNAs and then tested whether the microRNAs were differentially expressed in HCC tumour tissues, and we found that their expression was related to the HCC prognosis. Then, we investigated the effects of microRNAs on the cell growth and mobility of HCC using a real-time cell analyser (RTCA), colony formation assay and subcutaneous xenograft models. We further used deep-sequencing technology and bioinformatic analyses to evaluate the main functions of the microRNAs. We found that miR-103a was one of the most highly expressed microRNAs in HCC tissues and that it was upregulated in HCC tissue compared with the controls. In addition, high miR-103a expression was associated with poor patient prognosis, and its overexpression promoted HCC cell growth and mobility. A functional enrichment analysis showed that miR-103a mainly promoted glucose metabolism and inhibited cell death. We validated this analysis, and the data showed that miR-103a promoted glucose metabolism-likely function and directly inhibited cell death via ATP11A and EIF5. Therefore, our study revealed that miR-103a may act as a key mediator in HCC progression.

Cyclovirobuxine D Induced-Mitophagy through the p65/BNIP3/LC3 Axis Potentiates Its Apoptosis-Inducing Effects in Lung Cancer Cells

Mitophagy plays a pro-survival or pro-death role that is cellular-context- and stress-condition-dependent. In this study, we revealed that cyclovirobuxine D (CVB-D), a natural compound derived from Buxus microphylla, was able to provoke mitophagy in lung cancer cells. CVB-D-induced mitophagy potentiates apoptosis by promoting mitochondrial dysfunction. Mechanistically, CVB-D initiates mitophagy by enhancing the expression of the mitophagy receptor BNIP3 and strengthening its interaction with LC3 to provoke mitophagy. Our results further showed that p65, a transcriptional suppressor of BNIP3, is downregulated upon CVB-D treatment. The ectopic expression of p65 inhibits BNIP3 expression, while its knockdown significantly abolishes its transcriptional repression on BNIP3 upon CVB-D treatment. Importantly, nude mice bearing subcutaneous xenograft tumors presented retarded growth upon CVB-D treatment. Overall, we demonstrated that CVB-D treatment can provoke mitophagy and further revealed that the p65/BNIP3/LC3 axis is one potential mechanism involved in CVB-D-induced mitophagy in lung cancer cells, thus providing an effective antitumor therapeutic strategy for the treatment of lung cancer patients

Antitumor efficacy of 2-(6,8-dimethyl-5-nitro-4-chloroquinoline-2-yl)-5,6,7-trichloro-1,3-tropolone in lung cancer xenografts.

e15008 Background: Lung cancer is the most common cancer worldwide. The efficacy of chemotherapy for this tumor does not exceed 40%. Moreover, all cytotoxic agents cause many side effects. The search for new substances with an antitumor effect seems to be relevant. Tropolone alkaloids, which are seven-membered non-benzenoid aromatic compounds, are promising inhibitors of tumor growth. The purpose of the study was to evaluate the antitumor efficacy of 2-(6,8-dimethyl-5-nitro-4-chloroquinoline-2-yl)-5,6,7-trichloro-1,3-tropolone in subcutaneous xenografts of lung cancer A549 cells in immunodeficient Balb/c Nude mice. Methods: The study was performed on a PDX model of lung cancer created by subcutaneous injection of A549 cell suspension, 5x106 cells in 0.2 ml of a solution of serum-free nutrient medium 199 and Matrigel (1:1). Animals were equally divided into 5 groups (each n = 5). Experimental groups 1, 2, 3 and 4 received 2-(6,8-dimethyl-5-nitro-4-chloroquinoline-2-yl)-5,6,7-trichloro-1,3-tropolone at doses of 0.0055, 0.055, 0.55 and 2.75 mg/g, respectively; the control group received 1% starch gel. The dynamics of the growth of a subcutaneous xenograft was evaluated by measuring tumor nodes. The volumes of tumor nodes were calculated using the Shrek’s formula for the ellipsoid: V = a×b×c×p/6, where V is the tumor volume (mm3), and a, b, c are the maximum dimensions of the ellipsoid in three planes (mm). The data were statistically analyzed using the Exel and Medstatistic progams. Results: The dynamics of subcutaneous xenograft growth in groups 1, 2, 3 and 4 significantly differed from the control group (p = 0.023). The average tumor volumes on the 39th day after the implantation in the control group and in experimental groups 1, 2, 3 and 4 were 1159.2, 895.3, 565.8, 80.7 and 76.7 mm3, respectively. The inhibition of tumor growth (ITG) was in direct proportion to the dose of the administered substance. Lower ITG(%) (32.4, 23.2 and 10.3% in experimental groups 2, 3 and 4, respectively) was associated with lower concentrations of О154 (0.55 mg/g, 0.055 mg/g and 0.0055 mg/g, respectively). Conclusions: The study demonstrated statistically significant differences in xenograft volume indices in all experimental groups compared to the control group.