Carbonic anhydrase IX inhibitor S4 triggers release of DAMPs related to immunogenic cell death in glioma cells via endoplasmic reticulum stress pathway.

BACKGROUND: Immunogenic cell death (ICD), which releases danger-associated molecular patterns (DAMP) that induce potent anticancer immune response, has emerged as a key component of therapy-induced anti-tumor immunity. The aim of this work was to analyze whether the carbonic anhydrase IX inhibitor S4 can elicit ICD in glioma cells. METHODS: The effects of S4 on glioma cell growth were evaluated using the CCK-8, clonogenic and sphere assays. Glioma cell apoptosis was determined by flow cytometry. Surface-exposed calreticulin (CRT) was inspected by confocal imaging. The supernatants of S4-treated cells were concentrated for the determination of HMGB1and HSP70/90 expression by immunoblotting. RNA-seq was performed to compare gene expression profiles between S4-treated and control cells. Pharmacological inhibition of apoptosis, autophagy, necroptosis and endoplasmic reticulum (ER) stress was achieved by inhibitors. In vivo effects of S4 were evaluated in glioma xenografts. Immunohistochemistry (IHC) was performed to stain Ki67 and CRT. RESULTS: S4 significantly decreased the viability of glioma cells and induced apoptosis and autophagy. Moreover, S4 triggered CRT exposure and the release of HMGB1 and HSP70/90. Inhibition of either apoptosis or autophagy significantly reversed S4-induced release of DAMP molecules. RNA-seq analysis indicated that the ER stress pathway was deregulated upon exposure to S4. Both PERK-eIF2α and IRE1α- XBP1 axes were activated in S4-treated cells. Furthermore, pharmacological inhibition of PERK significantly suppressed S4-triggered ICD markers and autophagy. In glioma xenografts, S4 significantly reduced tumor growth. CONCLUSIONS: Altogether, these findings suggest S4 as a novel ICD inducer in glioma and might have implications for S4-based immunotherapy. Video Abstract.

UM-164, a Dual Inhibitor of c-Src and p38 MAPK, Suppresses Proliferation of Glioma by Reducing YAP Activity.

UM-164 is a dual inhibitor of c-Src and p38 MAPK, and has been a lead compound for targeting triple-negative breast cancer. UM-164 shows stronger binding to the active sites of Src compared with the conventional Src inhibitor Dasatinib. While Dasatinib has displayed some inhibitory effects on glioma growth in clinical trials, whether UM-164 can suppress glioma growth has not been reported. Here we show that UM-164 suppressed the proliferation, migration and spheroid formation of glioma cells, and induced cell cycle arrest in the G1 phase. Moreover, UM-164 triggered YAP translocation to the cytoplasm and reduced the activity of YAP, as evidenced by a luciferase assay. Accordingly, UM-164 markedly decreased the expression levels of YAP target genes CYR61 and AXL. Importantly, ectopic expression of wild-type YAP or YAP-5SA (YAP constitutively active mutant) could rescue the anti-proliferative effect induced by UM-164. Intriguingly, p38 MAPK appears to play a greater role than Src in UM-164-mediated inhibition of YAP activity. Furthermore, the in vitro anti-glioma effect mediated by UM-164 was confirmed in a xenograft glioma model. Together, these findings reveal a mechanism by which UM-164 suppresses the malignant phenotypes of glioma cells and might provide a rationale for UM-164-based anti-glioma clinical trials.

SUFU suppresses ferroptosis sensitivity in breast cancer cells via Hippo/YAP pathway.

Ferroptosis is a new kind of regulated cell death that is characterized by highly iron-dependent lipid peroxidation. Cancer cells differ in their sensitivity to ferroptosis. Here we showed that the Suppressor of fused homolog (SUFU), a critical component in Hedgehog signaling, regulates ferroptosis sensitivity of breast cancer cells. Ectopic SUFU expression suppressed, whereas depletion of SUFU enhanced the sensitivity of breast cancer cells to RSL3-triggered ferroptosis through deregulation of ACSL4. Moreover, SUFU depletion promoted the activation of Yes-associated protein (YAP), thereby increasing the expression of ACSL4. Mechanistically, SUFU is associated with LATS1. Deletion of a region comprising residues 174-385 in SUFU disrupted SUFU binding to LATS1, thus abrogating SUFU-mediated downregulation of the YAP-ACSL4 axis and sensitivity to ferroptosis. Noteworthy, we showed that vincristine downregulated SUFU, thus increasing breast cancer cell sensitivity to RSL3 in vitro and in vivo. Together, our findings uncover SUFU as a novel regulator in ferroptosis sensitivity.

SASH1 suppresses triple-negative breast cancer cell invasion through YAP-ARHGAP42-actin axis.

Triple-negative breast cancer (TNBC) is extremely aggressive and lacks effective therapy. SAM and SH3 domain containing1 (SASH1) has been implicated in TNBC as a candidate tumor suppressor; however, the mechanisms of action of SASH1 in TNBC remain underexplored. Here, we show that SASH1 was significantly downregulated in TNBC patients samples compared with other subtypes of breast cancer. Ectopic SASH1 expression inhibited, while depletion of SASH1 enhanced, the invasive phenotype of TNBC cells, accompanied by deregulated expression of MMP2 and MMP9. The functional effects of SASH1 depletion were confirmed in the chicken chorioallantoic membrane and mouse xenograft models. Mechanistically, SASH1 knockdown downregulated the phosphorylation levels of the Hippo kinase LATS1 and its effector YAP (Yes associated protein), thereby upregulating YAP accumulation together with its downstream target CYR61. Consistently, forced SASH1 expression exhibited opposite effects. Pharmacological inhibition of YAP or knockdown of YAP reversed the enhanced cell invasion of TNBC cells following SASH1 depletion. Furthermore, SASH1-induced YAP signaling was LATS1-dependent, which in reverse enhanced phosphorylation of SASH1. The SASH1 S407A mutant (phosphorylation deficient) failed to rescue the altered YAP signaling by SASH1 knockdown. Notably, SASH1 depletion upregulated ARHGAP42 levels via YAP-TEAD and the YAP-ARHGAP42-actin axis contributed to SASH1-regulated TNBC cell invasion. Therefore, our findings uncover a new mechanism for the tumor-suppressive activity of SASH1 in TNBC, which may serve as a novel target for therapeutic intervention.

FKBP9 promotes the malignant behavior of glioblastoma cells and confers resistance to endoplasmic reticulum stress inducers.

BACKGROUND: FK506-binding protein 9 (FKBP9) is amplified in high-grade gliomas (HGGs). However, the roles and mechanism(s) of FKBP9 in glioma are unknown. METHODS: The expression of FKBP9 in clinical glioma tissues was detected by immunohistochemistry (IHC). The correlation between FKBP9 expression levels and the clinical prognosis of glioma patients was examined by bioinformatic analysis. Glioblastoma (GBM) cell lines stably depleted of FKBP9 were established using lentiviruses expressing shRNAs against FKBP9. The effects of FKBP9 on GBM cells were determined by cell-based analyses, including anchorage-independent growth, spheroid formation, transwell invasion assay, confocal microscopy, immunoblot (IB) and coimmunoprecipitation assays. In vivo tumor growth was determined in both chick chorioallantoic membrane (CAM) and mouse xenograft models. RESULTS: High FKBP9 expression correlated with poor prognosis in glioma patients. Knockdown of FKBP9 markedly suppressed the malignant phenotype of GBM cells in vitro and inhibited tumor growth in vivo. Mechanistically, FKBP9 expression induced the activation of p38MAPK signaling via ASK1. Furthermore, ASK1-p38 signaling contributed to the FKBP9-mediated effects on GBM cell clonogenic growth. In addition, depletion of FKBP9 activated the IRE1α-XBP1 pathway, which played a role in the FKBP9-mediated oncogenic effects. Importantly, FKBP9 expression conferred GBM cell resistance to endoplasmic reticulum (ER) stress inducers that caused FKBP9 ubiquitination and degradation. CONCLUSIONS: Our findings suggest an oncogenic role for FKBP9 in GBM and reveal FKBP9 as a novel mediator in the IRE1α-XBP1 pathway.

Sirtuin1 activator SRT2183 suppresses glioma cell growth involving activation of endoplasmic reticulum stress pathway.

BACKGROUND: Glioblastoma (GBM) is an extremely deadly form of brain cancer with limited treatment options and thus novel therapeutic modalities are necessary. Histone deacetylase inhibitors (HDACi) have demonstrated clinical and preclinical activities against GBM. (Silent mating type information regulation 2 homolog, Sirt1) abbreviated as Sirtuin 1, has been implicated in GBM. We explored the activity of the Sirt1 activator SRT2183 in glioma cell lines in terms of biological response. METHODS: The effects of SRT2183 on glioma cell growth and neurosphere survival were evaluated in vitro using the CCK-8, clonogenic and neurosphere assays, respectively. Glioma cell cycle arrest and apoptosis were determined by flow cytometry. SRT2183-induced autophagy was investigated by detection of GFP-microtubule-associated protein 1 light chain 3 (GFP-LC3) puncta, conversion of the nonlipidated form of LC3 (LC3-I) to the phosphatidylethanolamine-conjugated form (LC3-II). Acetylation of STAT3 and NF-κB in SRT2183-treated glioma cells was examined using immunoprecipitation. The expression levels of anti-apoptotic proteins were assayed by immunoblotting. RESULTS: SRT2183 suppressed glioma cell growth and destroyed neurospheres in vitro. Furthermore, SRT2183 induced glioma cell cycle arrest and apoptosis, accompanying by upregulation of the pro-apoptotic Bim and downregulation of Bcl-2 and Bcl-xL. Notably, ER stress was triggered in glioma cells upon exposure to SRT2183 while the pre-exposure to 4-PBA, an ER stress inhibitor, significantly antagonized SRT2183-mediated growth inhibition in glioma cells. In addition, SRT2183 induced autophagy in glioma cells and pharmacological modulation of autophagy appeared not to affect SRT2183-inhibited cell growth. Of interest, the acetylation and phosphorylation of p65 NF-κB and STAT3 in glioma cells were differentially affected by SRT2183. CONCLUSIONS: Our data suggest the ER stress pathway is involved in SRT2183-mediated growth inhibition in glioma. Further investigation in vivo is needed to consolidate the data.

MLN4924 neddylation inhibitor promotes cell death in paclitaxel-resistant human lung adenocarcinoma cells.

Acquired resistance to first-line chemotherapeutics, including paclitaxel (PTX), is a primary factor contributing to chemotherapy failure in non-small cell lung cancer (NSCLC) patients. Previous studies have identified that targeting NEDD8-activating enzyme (NAE) with MLN4924 effectively overcomes platinum resistance in preclinical models of ovarian cancer. However, the underlying mechanisms are yet to be fully elucidated. The present study demonstrates that the inhibition of the neddylation pathway with MLN4924 an NAE inhibitor inhibited protein neddylation, inactivated cullin-RING E3 ligase and exhibited a potent antiproliferative effect on PTX-resistant A549 and H460 cells (A549/PTX and H460/PTX). The application of MLN4924 promotes apoptosis and DNA damage in A549/PTX and H460/PTX cells. Additionally, MLN4924 abrogated the 3-dimensional growth potential of these cells and inhibited the formation of the A549/PTX and H460/PTX spheroids. Notably, combining MLN4924 with PTX did not exhibit synergy in PTX-resistant NSCLC cells. Taken together, the results of the current study suggest that MLN4924 may be utilized as an effective strategy for the treatment of PTX-resistant NSCLC.