Global and regional long-term survival following resection for HCC in the recent decade: A meta-analysis of 110 studies.

Surgical resection for HCC remains a major curative treatment option, but it is unclear whether there are differences in outcomes by region and whether outcomes have improved over time. We aimed to estimate pooled overall survival (OS), recurrence-free survival (RFS), and complication rates in patients with hepatocellular carcinoma (HCC) following curative surgical resection and to compare outcomes by region and by time period. In this systematic review and meta-analysis, we searched Pubmed, Embase, and Cochrane databases from inception to May 15, 2020. We selected studies reporting OS, RFS, and complications in adult patients with HCC undergoing curative surgical resection. Two authors independently searched the literature and extracted the data. We screened 6983 articles and included 110 eligible studies with 82,392 patients, with study periods spanning from 1980-2017. The global pooled 1-year and 5-year survival rates were 88.9% (95% confidence interval [CI] 87.1-90.4) and 56.2% (95% CI 52.8-59.6) for OS and 71.1% (95% CI 67.6-74.3) and 35.2% (95% CI 32.5-38.0) for RFS, respectively. Five-year OS was higher in Asia (57.03%) than in other regions (Europe 48.3%; North America 48.0%; and South America 49.5%); p = 0.002. Five-year RFS was higher in patients with hepatitis B virus versus patients with hepatitis C virus (34.8% vs. 24.1%; p = 0.02). There was no significant improvement in 5-year OS and RFS over time. The pooled rate for complications was 27.6% (95% CI 23.4-32.3), with 9.7% (95% CI 6.3-14.7) classified as major. One-year OS after surgical resection for HCC is excellent (~90%). However, 5-year OS (~55%) and RFS (~35%) are still poor, suggesting that long-term care is suboptimal. Greater efforts are required to improve survival through enhanced surveillance and preventing recurrence through antiviral therapy.

SLC7A11 Overexpression in Glioblastoma Is Associated with Increased Cancer Stem Cell-Like Properties.

System xc- is a sodium-independent electroneutral transporter, comprising a catalytic subunit xCT (SLC7A11), which is involved in importing cystine. Certain cancers such as gliomas upregulate the expression of system xc-, which confers a survival advantage against the detrimental effects of reactive oxygen species (ROS) by increasing generation of the antioxidant glutathione. However, ROS have also been shown to function as targeted, intracellular second messengers in an array of physiological processes such as proliferation. Several studies have implicated ROS in important cancer features such as migration, invasion, and contribution to a cancer stem cell (CSC)-like phenotype. The role of system xc- in regulating these ROS-sensitive processes in glioblastoma multiforme (GBM), the most aggressive malignant primary brain tumor in adults, remains unknown. Stable SLC7A11 knockdown and overexpressing U251 glioma cells were generated and characterized to understand the role of redox and system xc- in glioma progression. SLC7A11 knockdown resulted in higher endogenous ROS levels and enhanced invasive properties. On the contrary, overexpression of SLC7A11 resulted in decreased endogenous ROS levels as well as decreased migration and invasion. However, SLC7A11-overexpressing cells displayed actin cytoskeleton changes reminiscent of epithelial-like cells and exhibited an increased CSC-like phenotype. The enhanced CSC-like phenotype may contribute to increased chemoresistance and suggests that overexpression of SLC7A11 in the context of GBM may contribute to tumor progression. These findings have important implications for cancer management where targeting system xC- in combination with other chemotherapeutics can reduce cancer resistance and recurrence and improve GBM patient survival.

Increased Expression of System xc- in Glioblastoma Confers an Altered Metabolic State and Temozolomide Resistance.

Glioblastoma multiforme is the most aggressive malignant primary brain tumor in adults. Several studies have shown that glioma cells upregulate the expression of xCT (SLC7A11), the catalytic subunit of system xc-, a transporter involved in cystine import, that modulates glutathione production and glioma growth. However, the role of system xc- in regulating the sensitivity of glioma cells to chemotherapy is currently debated. Inhibiting system xc- with sulfasalazine decreased glioma growth and survival via redox modulation, and use of the chemotherapeutic agent temozolomide together with sulfasalazine had a synergistic effect on cell killing. To better understand the functional consequences of system xc- in glioma, stable SLC7A11-knockdown and -overexpressing U251 glioma cells were generated. Modulation of SLC7A11 did not alter cellar proliferation but overexpression did increase anchorage-independent cell growth. Knockdown of SLC7A11 increased basal reactive oxygen species (ROS) and decreased glutathione generation resulting in increased cell death under oxidative and genotoxic stress. Overexpression of SLC7A11 resulted in increased resistance to oxidative stress and decreased chemosensitivity to temozolomide. In addition, SLC7A11 overexpression was associated with altered cellular metabolism including increased mitochondrial biogenesis, oxidative phosphorylation, and ATP generation. These results suggest that expression of SLC7A11 in the context of glioma contributes to tumorigenesis, tumor progression, and resistance to standard chemotherapy. IMPLICATIONS: SLC7A11, in addition to redox modulation, appears to be associated with increased cellular metabolism and is a mediator of temozolomide resistance in human glioma, thus making system xC- a potential therapeutic target in glioblastoma multiforme. Mol Cancer Res; 14(12); 1229-42. ©2016 AACR.