Glutamine synthase 2 (GLS2) is a key regulator of glutaminolysis and has been previously implicated in activities consistent with tumor suppression. Here we generated Gls2 knockout (KO) mice that develop late-occurring B-cell lymphomas and hepatocellular carcinomas (HCC). Further, Gls2 KO mice subjected to the hepatocarcinogenic Stelic Animal Model (STAM) protocol produce larger HCC tumors than seen in wild-type (WT) mice. GLS2 has been shown to promote ferroptosis, a form of cell death characterized by iron-dependent accumulation of lipid peroxides. In line with this, GLS2 deficiency, either in cells derived from Gls2 KO mice or in human cancer cells depleted of GLS2, conferred significant resistance to ferroptosis. Mechanistically, GLS2, but not GLS1, increased lipid reactive oxygen species (ROS) production by facilitating the conversion of glutamate to α-ketoglutarate (αKG), thereby promoting ferroptosis. Ectopic expression of WT GLS2 in a human hepatic adenocarcinoma xenograft model significantly reduced tumor size; this effect was nullified by either expressing a catalytically inactive form of GLS2 or by blocking ferroptosis. Furthermore, analysis of cancer patient datasets supported a role for GLS2-mediated regulation of ferroptosis in human tumor suppression. These data suggest that GLS2 is a bona fide tumor suppressor and that its ability to favor ferroptosis by regulating glutaminolysis contributes to its tumor suppressive function. Significance: This study demonstrates that the key regulator of glutaminolysis, GLS2, can limit HCC in vivo by promoting ferroptosis through αKG-dependent lipid ROS, which in turn might lay the foundation for a novel therapeutic approach.

Iijima M, et al. J Gynecol Oncol. 2019 Jun;31:e19. https://doi.org/10.3802/jgo.2020.31.e19

With the advent of immune checkpoint inhibitors (ICIs), a better understanding of tumor microenvironment (TME) is becoming crucial in managing esophageal squamous cell carcinoma (ESCC) patients. We investigated the survival impact of TME status and changes in patients with ESCC who underwent neoadjuvant chemotherapy (NAC) followed by surgery (n = 264). We examined immunohistochemical status (CD4⁺, CD8⁺, CD20⁺, Foxp3⁺, HLA class‐1⁺, CD204⁺, and programmed death ligand‐1 [PD‐L1⁺]) on 264 pre‐NAC and 204 paired post‐NAC specimens. Patients were classified by their pre‐ and post‐NAC immune cell status and their changes following NAC. Our findings showed that pre‐NAC TME status was not significantly associated with survival outcomes. In contrast, post‐NAC TME status, such as low level of T cells, CD4⁺ T cells, and high PD‐L1 combined positive score (CPS), were significantly associated with poor overall survival (OS). Notably, TME changes through NAC exerted significant survival impacts; patients with consistently low levels of T cells, low levels of CD4⁺ T cells, or high levels of PD‐L1 (CPS) had very poor OS (3‐year OS: 35.5%, 40.2%, and 33.3%, respectively). Tumor microenvironment changes of consistently low T cells, low CD4⁺ T cells, and high PD‐L1 were independent predictors of poor OS in multivariate Cox hazards analyses, while factors indicating post‐NAC status (T cells, CD4⁺, and PD‐L1 [CPS]) alone were not. Therefore, we suggest that the consistently low T/high PD‐L1 group could benefit from additional therapies, such as ICIs, and the importance of stratification by the TME, which has recently been recognized.

Background: Enterotoxigenic Bacteroides fragilis (ETBF) carries the bft toxin gene, which influences the host immune response and inflammatory pathways and promotes colorectal cancer (CRC). This study investigated the potential role of ETBF in CRC liver metastasis. Methods: We reviewed the records of 226 consecutive patients who underwent curative-intent (R0) resection of CRC liver metastases. ETBF DNA in fresh-frozen metastasis specimens was quantified using droplet digital PCR (ddPCR). Patients were grouped into very-low (≤80%; N = 178), low (80–90%; N = 24), and high (>90%; N = 24) ETBF-DNA groups. Three tissue cores per specimen were stained for CD8, CD4, CD20, FOXP3, CD68, and CD163, and immune-cell densities were measured digitally (cells/mm²). Results: ETBF DNA was detected in 219 of 226 lesions (96.9%). The densities of cytotoxic CD8⁺ T-cells, effector CD4⁺ T-cells, CD20⁺ B-cells, and CD163⁺ macrophages did not differ significantly by ETBF-DNA group (P_trend all > 0.12). FOXP3⁺ regulatory T-cells (Tregs) decreased (P_trend = 0.010), and CD68⁺ macrophages increased (P_trend = 0.020) as ETBF-DNA levels increased. ETBF-DNA levels in CRC liver metastases were not associated with disease-free survival or overall survival or serum C-reactive protein levels. Conclusions: ETBF was present in almost all CRC liver metastases. Higher ETBF levels were associated with a tumor-immune microenvironment enriched in CD68⁺ macrophages and deficient in FOXP3⁺ Tregs, suggesting that ETBF facilitates immune evasion without loss of effector lymphocytes. Although ETBF-DNA levels did not predict survival in this single-center cohort, the potential role of ETBF in immune remodeling and as a candidate biomarker and therapeutic target in metastatic CRC warrants further study.