Spatial and single-cell explorations uncover prognostic significance and immunological functions of mitochondrial calcium uniporter in breast cancer.

The mitochondrial calcium uniporter (MCU) is a transmembrane protein facilitating the entry of calcium ions into mitochondria from the cell cytosol. Maintaining calcium balance is crucial for enhancing cellular energy supply and regulating cell death. The interplay of calcium balance through MCU and the sodium-calcium exchanger is known, but its regulation in the breast cancer tumor microenvironment remains elusive. Further investigations are warranted to explore MCU's potential in BRCA clinical pathology, tumor immune microenvironment, and precision oncology. Our study, employing a multi-omics approach, identifies MCU as an independent diagnostic biomarker for breast cancer (BRCA), correlated with advanced clinical status and poor overall survival. Utilizing public datasets from GEO and TCGA, we discern differentially expressed genes in BRCA and examine their associations with immune gene expression, overall survival, tumor stage, gene mutation status, and infiltrating immune cells. Spatial transcriptomics is employed to investigate MCU gene expression in various regions of BRCA, while spatial transcriptomics and single-cell RNA-sequencing methods explore the correlation between MCUs and immune cells. Our findings are validated through the analysis of 59 BRCA patient samples, utilizing immunohistochemistry and bioinformatics to examine the relationship between MCU expression, clinicopathological features, and prognosis. The study uncovers the expression of key gene regulators in BRCA associated with genetic variations, deletions, and the tumor microenvironment. Mutations in these regulators positively correlate with different immune cells in six immune datasets, playing a pivotal role in immune cell infiltration in BRCA. Notably, high MCU performance is linked to CD8 + T cells infiltration in BRCA. Furthermore, pharmacogenomic analysis of BRCA cell lines indicates that MCU inactivation is associated with increased sensitivity to specific small molecule drugs. Our findings suggest that MCU alterations may be linked to BRCA progression, unveiling new diagnostic and prognostic implications for MCU in BRCA. The study underscores MCU's role in the tumor immune microenvironment and cell cycle progression, positioning it as a potential tool for BRCA precision medicine and drug screening.

Deltex1 suppresses T cell function and is a biomarker for diagnosis and disease activity of systemic lupus erythematosus.

OBJECTIVE: Deletion of Deltex1 (DTX1) in mice caused hyperactivation of T cells and lupus-like autoimmune syndromes, however, the association of DTX1 with human autoimmune diseases is totally unknown. This study investigated the role of DTX1 in human T cell functions and its correlation with disease activity in patients with SLE. METHODS: The influence of DTX1 on T cell function was evaluated using human primary cells. DTX1 expression in peripheral blood mononuclear cells (PBMCs) from healthy controls and SLE patients was measured by quantitative real-time PCR and the SLEDAI was used to assess disease activity. RESULTS: After stimulation with anti-CD3 and anti-CD28, silencing of DTX1 expression enhanced IFN-γ secretion by human T cells. The expression of DTX1 in PBMCs was significantly lower in 100 SLE patients than in 50 age- and sex-matched healthy controls (DTX1/glyceraldehyde 3-phosphate dehydrogenase, 0.452 vs 1.269, P < 0.001). The area under the receiver operator characteristics curve of the model was 0.737 (95% CI 0.658, 0.815). Intriguingly, a low DTX1 level in T cells led to high IFN-γ production in SLE patients and had a correlation with severe disease activity. In addition, low DTX1 expression in SLE patients was associated with active LN, lung involvement or hypocomplementaemia. CONCLUSION: Knockdown DTX1 expression in human T cells reduced IFN-γ secretion. DTX1 expression in the PBMCs was significantly lower in SLE patients and had an inverse correlation with disease activity, indicating that the DTX1 level may be a good disease marker of SLE.

Deltex1 promotes protein kinase Cθ degradation and sustains Casitas B-lineage lymphoma expression.

The generation of T cell anergy is associated with upregulation of ubiquitin E3 ligases including Casitas B-lineage lymphoma (Cbl-b), Itch, gene related to anergy in lymphocyte, and deltex1 (DTX1). These E3 ligases attenuate T cell activation by targeting to signaling molecules. For example, Cbl-b and Itch promote the degradation of protein kinase Cθ (PKCθ) and phospholipase C-γ1 (PLC-γ1) in anergic Th1 cells. How these anergy-associated E3 ligases coordinate during T cell anergy remains largely unknown. In the current study, we found that PKCθ and PLC-γ1 are also downregulated by DTX1. DTX1 interacted with PKCθ and PLC-γ1 and stimulated the degradation of PKCθ and PLC-γ1. T cell anergy-induced proteolysis of PKCθ was prevented in Dtx1(-/-) T cells, supporting the essential role of DTX1 in PKCθ downregulation. Similar to Cbl-b and Itch, DTX1 promoted monoubiquitination of PKCθ. Proteasome inhibitor did not inhibit DTX1-directed PKCθ degradation, but instead DTX1 directed the relocalization of PKCθ into the lysosomal pathway. In addition, DTX1 interacted with Cbl-b and increased the protein levels of Cbl-b. We further demonstrated the possibility that, through the downregulation of PKCθ, DTX1 prevented PKCθ-induced Cbl-b degradation and increased Cbl-b protein stability. Our results suggest the coordination between E3 ligases during T cell anergy; DTX1 acts with Cbl-b to assure a more extensive silencing of PKCθ, whereas DTX1-mediated PKCθ degradation further stabilizes Cbl-b.

Spatial and Single-Cell Investigations Illuminate Theragnostic value and Immune Landscape of Mitochondrial Dynamin-Like GTPase in Breast Cancer.

Background: As we delve into the intricate world of mitochondrial inner membrane proteins, particularly Optic Atrophy types 1 and 3 (OPA1/3), we uncover their pivotal role in maintaining mitochondrial dynamic equilibrium and fusion, crucial for cellular energy production and synthesis. Despite extensive scrutiny, the significance of OPA1/3 in breast cancer (BRCA) and its interplay with the immune microenvironment remain elusive. Materials and Methods: We meticulously sourced BRCA data from renowned repositories such as The Cancer Genome Atlas (TCGA), Genotype-Tissue Expression (GTEx), Gene Expression Omnibus (GEO), and the Human Protein Atlas (HPA), leveraging cutting-edge techniques including single-cell RNA-sequencing (scRNA-seq), spatial transcriptomics, and pharmacogenomics. Through multifaceted data analysis, we endeavored to unravel the intricate role and potential value of OPA1/3 in BRCA tumorigenesis and progression. Results: Our investigation reveals a conspicuous upregulation of OPA1/3 expression in BRCA, correlating with dismal prognoses. Kaplan-Meier plot analysis underscores that heightened OPA1/3 levels are associated with poor survival rates. Both clinical specimens and biobank biopsies corroborate the elevated expression of OPA1/3 in breast cancer patients. Moreover, scRNA-seq unveils a strong correlation between OPA1/3 and macrophage infiltration in the BRCA immune milieu, alongside its association with the cellular communication network involving CXCL, TGFb, VEGF, and IL16. Conclusion: In light of these findings, OPA1/3 emerges as a promising contender for therapeutic targeting and as a potential diagnostic, prognostic, and survival biomarker in BRCA. The implications of our study underscore the pressing need to explore these novel biomarkers to enhance patient outcomes.

Multi-omic profiling of breast tumor microenvironment uncovers a role of mitochondrial calcium gatekeepers.

In this study, we aimed to elucidate the role of mitochondrial calcium uptake 1/2 (MiCU1/2) in breast cancer (BRCA) by employing a comprehensive multi-omics approach. Unlike previous research, we utilized a novel web application tailored for whole tumor tissue, single-cell, and spatial transcriptomics analysis to investigate the association between MiCU1/2 and the tumor immune microenvironment (TIME). Our gene set enrichment analysis (GSEA) provided insights into the primary biological effects of MiCU1/2, while our CRISPR-based drug screening repository identified potential effective drugs. Our study revealed that high MiCU1/2 expression serves as an independent diagnostic biomarker, correlating with advanced clinical status and indicating poorer recurrence-free survival (RFS) rates in BRCA patients. Additionally, spatial transcriptome analysis highlighted the heightened expression of MiCU1/2 in tumors and its relevance in surrounding immune cells. Furthermore, using the CIBERSORT algorithm, we discovered a positive correlation between MiCU1/2 levels and macrophage infiltration, underscoring their potential impact on immune infiltration. We also identified expression patterns of immune-related genes associated with responses against various immune cell types, including CXCL, MIF, GDF, SPP1, and IL16. Finally, our pharmacogenomic screening identified potential small molecule drugs capable of effectively targeting breast cancer cells with elevated MiCU1/2 expression. Overall, our study establishes MiCU1/2 as a promising novel biomarker for BRCA diagnosis and prognostic prediction, as well as a potential therapeutic target, highlighting the importance of exploring these pathways to advance patient care and outcomes in BRCA treatment.

Tumor suppressor p53 mediates interleukin-6 expression to enable cancer cell evasion of genotoxic stress.

The tumor suppressor p53 primarily functions as a mediator of DNA damage-induced cell death, thereby contributing to the efficacy of genotoxic anticancer therapeutics. Here, we show, on the contrary, that cancer cells can employ genotoxic stress-induced p53 to acquire treatment resistance through the production of the pleiotropic cytokine interleukin (IL)-6. Mechanistically, DNA damage, either repairable or irreparable, activates p53 and stimulates Caspase-2-mediated cleavage of its negative regulator mouse double minute 2 (MDM2) creating a positive feedback loop that leads to elevated p53 protein accumulation. p53 transcriptionally controls the major adenosine triphosphate (ATP) release channel pannexin 1 (Panx1), which directs IL-6 induction via a mechanism dependent on the extracellular ATP-activated purinergic P2 receptors as well as their downstream intracellular calcium (iCa2+)/PI3K/Akt/NF-ĸB signaling pathway. Thus, p53 silencing impairs Panx1 and IL-6 expression and renders cancer cells sensitive to genotoxic stress. Moreover, we confirm that IL-6 hampers the effectiveness of genotoxic anticancer agents by mitigating DNA damage, driving the expression of anti-apoptotic Bcl-2 family genes, and maintaining the migratory and invasive properties of cancer cells. Analysis of patient survival and relevant factors in lung cancer and pan-cancer cohorts supports the prognostic and clinical values of Panx1 and IL-6. Notably, IL-6 secreted by cancer cells during genotoxic treatments promotes the polarization of monocytic THP-1-derived macrophages into an alternative (M2-like) phenotype that exhibits impaired anti-survival activities but enhanced pro-metastatic effects on cancer cells as compared to nonpolarized macrophages. Our study reveals the precise mechanism for genotoxic-induced IL-6 and suggests that targeting p53-mediated IL-6 may improve the responsiveness of cancer cells to genotoxic anticancer therapy.

Action mechanism of snake venom l-amino acid oxidase and its double-edged sword effect on cancer treatment: Role of pannexin 1-mediated interleukin-6 expression.

Snake venom l-amino acid oxidases (svLAAOs) have been recognized as promising candidates for anticancer therapeutics. However, multiple aspects of their catalytic mechanism and the overall responses of cancer cells to these redox enzymes remain ambiguous. Here, we present an analysis of the phylogenetic relationships and active site-related residues among svLAAOs and reveal that the previously proposed critical catalytic residue His 223 is highly conserved in the viperid but not the elapid svLAAO clade. To gain further insight into the action mechanism of the elapid svLAAOs, we purify and characterize the structural, biochemical, and anticancer therapeutic potentials of the Thailand elapid snake Naja kaouthia LAAO (NK-LAAO). We find that NK-LAAO, with Ser 223, exhibits high catalytic activity toward hydrophobic l-amino acid substrates. Moreover, NK-LAAO induces substantial oxidative stress-mediated cytotoxicity with the magnitude relying on both the levels of extracellular hydrogen peroxide (H2O2) and intracellular reactive oxygen species (ROS) generated during the enzymatic redox reactions, but not being influenced by the N-linked glycans on its surface. Unexpectedly, we discover a tolerant mechanism deployed by cancer cells to dampen the anticancer activities of NK-LAAO. NK-LAAO treatment amplifies interleukin (IL)-6 expression via the pannexin 1 (Panx1)-directed intracellular calcium (iCa2+) signaling pathway to confer adaptive and aggressive phenotypes on cancer cells. Accordingly, IL-6 silencing renders cancer cells vulnerable to NK-LAAO-induced oxidative stress together with abrogating NK-LAAO-stimulated metastatic acquisition. Collectively, our study urges caution when using svLAAOs in cancer treatment and identifies the Panx1/iCa2+/IL-6 axis as a therapeutic target for improving the effectiveness of svLAAOs-based anticancer therapies.

Nanoscaled biphasic calcium phosphate modulates osteogenesis and attenuates LPS-induced inflammation.

Micron-scale structure biphasic calcium phosphate (BCP) materials have demonstrated promising clinical outcomes in the field of bone tissue repair. However, research on biphasic calcium phosphate materials at the nanoscale level remains limited. In this study, we synthesize granular-shaped biphasic calcium phosphate nanomaterials with multiple desirable characteristics, including negatively charged surfaces, non-cytotoxicity, and the capability to penetrate cells, using a nanogrinding dispersion process with a polymeric carboxylic acid as the dispersant. Our results reveal that treating human osteoblasts with 0.5 µg/mL biphasic calcium phosphate nanomaterials results in a marked increase in alkaline phosphatase (ALP) activity and the upregulation of osteogenesis-related genes. Furthermore, these biphasic calcium phosphate nanomaterials exhibit immunomodulatory properties. Treatment of THP-1-derived macrophages with BCP nanomaterials decreases the expression of various inflammatory genes. Biphasic calcium phosphate nanomaterials also mitigate the elevated inflammatory gene expression and protein production triggered by lipopolysaccharide (LPS) exposure in THP-1-derived macrophages. Notably, we observe that biphasic calcium phosphate nanomaterials have the capacity to reverse the detrimental effects of LPS-stimulated macrophage-conditioned medium on osteoblastic activity and mineralization. These findings underscore the potential utility of biphasic calcium phosphate nanomaterials in clinical settings for the repair and regeneration of bone tissue. In conclusion, this study highlights the material properties and positive effects of biphasic calcium phosphate nanomaterials on osteogenesis and immune regulation, opening a promising avenue for further research on inflammatory osteolysis in patients undergoing clinical surgery.

HIF-2α is indispensable for regulatory T cell function.

Hypoxia-inducible factor 1α (HIF-1α) and HIF-2α are master transcription factors that regulate cellular responses to hypoxia, but the exact function in regulatory T (Treg) cells is controversial. Here, we show that Treg cell development is normal in mice with Foxp3-specific knockout (KO) of HIF-1α or HIF-2α. However, HIF-2α-KO (but not HIF-1α-KO) Treg cells are functionally defective in suppressing effector T cell-induced colitis and inhibiting airway hypersensitivity. HIF-2α-KO Treg cells have enhanced reprogramming into IL-17-secreting cells. We show crosstalk between HIF-2α and HIF-1α, and that HIF-2α represses HIF-1α expression. HIF-1α is upregulated in HIF-2α-KO Treg cells and further deletion of HIF-1α restores the inhibitory function of HIF-2α-KO Treg cells. Mice with Foxp3-conditional KO of HIF-2α are resistant to growth of MC38 colon adenocarcinoma and metastases of B16F10 melanoma. Together, these results indicate that targeting HIF-2α to destabilize Treg cells might be an approach for regulating the functional activity of Treg cells.

Attenuation of cadmium-induced necrotic cell death by necrostatin-1: potential necrostatin-1 acting sites.

Cadmium (Cd) induces necrotic death in Chinese hamster ovary (CHO) K1 cells and we have established the responsible signaling pathway. Reportedly, necrostatin-1 (Nec-1) rescues cells from necrotic death by mediating through the death domain receptor (DR) signaling pathway. We show here that Nec-1 also effectively attenuates necrotic death triggered by Cd. Two other treatments that cause necrotic cell death, one can (z-VAD-fmk/TNF-alpha on U937 cells) and the other cannot (etherynic acid (EA) on DLD-1 cells) be rescued by Nec-1, were also studied in parallel for comparison. Results show that Nec-1 is ineffectual in modulating intracellular calcium contents, calpain activity (a downstream protease), or reactive oxygen species production. It can counteract the reduction in mitochondrial membrane potential (MMP) caused by treating CHO K1 or U937 cells with necrosis-inducing agent. However, this effect was not found in EA-treated DLD-1 cells. Notably, Nec-1 elevates NF-kappaB activity in the presence or absence of necrosis-inducing agents. Our study shows that, in addition to DR-mediated necrosis, Nec-1 is effective in attenuating Cd-induced necrosis. It rescues cells with reduced MMP implying that mitochondrion is its major acting site.

Comparison of organic and inorganic germanium compounds in cellular radiosensitivity and preparation of germanium nanoparticles as a radiosensitizer.

PURPOSE: The aim of this work is to compare the radiosensitizing effect between organic and inorganic germanium compounds and to investigate whether nanometer-sized germanium particles can act as radiosensitizers. MATERIALS AND METHODS: Bis (2-carboxyethylgermanium) sesquioxide (Ge-132), germanium oxide (GeO(2)) and germanium nanoparticles were used in this study. Cell viability was determined by clonogenic survival assay. Cellular DNA damage was evaluated by alkaline comet assay, confocal microscopy and the cellular level of phospho-histone H2AX (gamma-H2AX). RESULTS: Nanometer-sized germanium particles were fabricated. They have a similar radiosensitizing effect as that of GeO(2). Conversely, Ge-132 did not enhance the radiosensitivity of cells. Comet assay was employed to evaluate the level of DNA damage and confirmed that inorganic germanium compounds enhanced cellular radiosensitivity. Notably, the comet assay indicated that the nanoparticle itself caused a higher level of DNA damage. The possibility that germanium nanoparticles per se caused DNA damage was ruled out when the cellular level of gamma-H2AX was examined. CONCLUSIONS: We demonstrated that inorganic but not organic germanium compounds exerted radiosensitizing effect in cells. Nanometer-sized germanium particles were fabricated and were able to enhance the radiosensitivity of cells. Confounding effect may occur when comet assay is used to estimate the level of DNA damage in the presence of germanium nanoparticles.

7-Chloro-6-piperidin-1-yl-quinoline-5,8-dione (PT-262), a novel synthetic compound induces lung carcinoma cell death associated with inhibiting ERK and CDC2 phosphorylation via a p53-independent pathway.

BACKGROUND: The derivatives of 5,8-quinolinedione have been shown to exert anticancer activities. A new synthetic compound 7-chloro-6-piperidin-1-yl-quinoline-5,8-dione (designed as PT-262) derived from 6,7-dichloroquinoline-5,8-dione on its anticancer activity was investigated in this study. MATERIALS AND METHODS: PT-262 was synthesized as the following: triethylamine (0.56 ml, 5.1 mmol) was added dropwise to a solution of 6,7-dichloroquinoline-5,8-dione (1.00 g, 4.4 mmol) and piperidine (0.50 ml, 5.1 mmol) in 150 ml of benzene with stirring at room temperature for 5 min, and the solvent was removed using rotary evaporator to give a dark brown solid. PT-262 was purified by flash chromatography using 50% ethyl acetate/hexanes to elute that displayed as brown solids. To examine the induction of apoptosis following PT-262 treatment, the lung cancer cells were subjected to apoptotic cell observation, caspase activation, and mitochondrial functional assays. The protein levels of phosphorylated ERK and CDC2 after treatment with PT-262 were analyzed by Western blot. RESULTS: Treatment with 1-20 microM PT-262 for 24 h induced cytotoxicity via a concentration-dependent manner in human lung cancer cells. PT-262 induced the loss of mitochondrial membrane potential and elevated the caspase-3 activation and apoptosis. Interestingly, the phosphorylation of ERK was inhibited by PT-262. The IC50 value of ERK phosphorylation inhibition was approximate around 5 microM. Treatment with a specific MEK1/2 (the upstream of ERK) inhibitor, PD98059, increased the PT-262-induced cytotoxicity in lung cancer cells. Moreover, PT-262 did not alter the protein expression of tumor suppressor p53. PT-262 elicited the cytotoxicity and accumulated the G2/M fractions in both the p53-wild type and p53-null lung cancer cells. The mitosis-regulated protein levels of cyclin B1 and phospho-CDC2 at Thr14, Tyr15, and Thr161 were repressed by PT-262 in these cells. CONCLUSION: PT-262 suppresses the phosphorylation of ERK and CDC2 associated with proliferation inhibition via a p53-independent pathway in human lung cancer cells.

Regulation of gamma-H2AX and securin contribute to apoptosis by oxaliplatin via a p38 mitogen-activated protein kinase-dependent pathway in human colorectal cancer cells.

Oxaliplatin, a chemotherapeutic drug, induces DNA strand breaks leading to apoptosis in colorectal cancer cells. gamma-H2AX is a phosphorylated histone H2AX that can act as a marker of DNA double-strand breaks (DSBs). It has been shown that securin proteins were over-expressed in a variety of cancer cells. However, the roles of gamma-H2AX and securin on the oxaliplatin-induced apoptosis in human colorectal cancer cells remain unclear. Treatment of oxaliplatin (1-10 microM for 6-24h) persistently induced gamma-H2AX formation and inhibited securin protein expression via a time- and concentration-dependent manner in HCT116 securin-wild type colorectal cancer cells. Compared with HCT116 securin-wild type cells, the induction of apoptosis and persistent gamma-H2AX formation by oxaliplatin was reduced in the HCT116 securin-null colorectal cancer cells. Furthermore, the blockage of caspases by specific caspase inhibitors reduced the levels of gamma-H2AX proteins and cytotoxicity but increased securin protein expression in the oxaliplatin-exposed cells. The gene knockdown of H2AX by transfection with a short interfering RNA of H2AX enhanced the oxaliplatin-induced cell death. Interestingly, the phosphorylation of p38 mitogen-activated protein kinase (MAPK) was markedly increased by oxaliplatin. Pre-treatment of a specific p38 MAPK inhibitor SB202190 reduced gamma-H2AX proteins and increased securin protein expression in the oxaliplatin-treated cells. Our findings suggest that p38 MAPK may oppositely regulate securin protein expression and gamma-H2AX formation in the oxaliplatin-induced apoptosis of human colorectal cancer cells.

Hypoxia-inducible factor 1α plays a predominantly negative role in regulatory T cell functions.

Hypoxia-inducible factor 1α (HIF-1α) regulates cellular responses to hypoxia. However, conflicting roles for HIF-1α in the functions of regulatory T cells (Tregs) have been reported. In this review, we summarize observations on the requirement for HIF-1α for FOXP3 expression and Tregs development, as well as for HIF-1α-mediated downregulation of FOXP3 and Tregs destabilization. We also examine the association of HIF-1α with Tregs under pathogenic conditions. Based on these findings, we suggest that HIF-1α mainly plays a detrimental role in the function and stability of Tregs and that HIF-1α is disposable for the development and suppressive function of Tregs.

IL-6 receptor blockade corrects defects of XIAP-deficient regulatory T cells.

X-linked lymphoproliferative syndrome type-2 (XLP-2) is a primary immunodeficiency disease attributed to XIAP mutation and is triggered by infection. Here, we show that mouse Xiap-/- regulatory T (Treg) cells and human XIAP-deficient Treg cells are defective in suppressive function. The Xiap-/- Treg cell defect is linked partly to decreased SOCS1 expression. XIAP binds SOCS1 and promotes SOCS1 stabilization. Foxp3 stability is reduced in Xiap-/- Treg cells. In addition, Xiap-/- Treg cells are prone to IFN-γ secretion. Transfer of wild-type Treg cells partly rescues infection-induced inflammation in Xiap-/- mice. Notably, inflammation-induced reprogramming of Xiap-/- Treg cells can be prevented by blockade of the IL-6 receptor (IL-6R), and a combination of anti-IL-6R and Xiap-/- Treg cells confers survival to inflammatory infection in Xiap-/- mice. Our results suggest that XLP-2 can be corrected by combination treatment with autologous iTreg (induced Treg) cells and anti-IL-6R antibody, bypassing the necessity to transduce Treg cells with XIAP.

c-FLIP is a target of the E3 ligase deltex1 in gastric cancer.

The ubiquitin E3 ligase DELTEX1 (DTX1) is specifically downregulated in gastric cancer tissues, and expression of DTX1 is linked to better prognoses and survival in gastric cancer. Cellular FLICE inhibitory protein (c-FLIP) is known for its pivotal role in the resistance of cancer cells to death receptor-induced cell death. Here, we show that DTX1 is an E3 ligase for c-FLIP in gastric cancer cells. DTX1 promoted c-FLIP downregulation. Overexpression of DTX1 sensitized gastric cancer cells to TRAIL-induced apoptosis, whereas DTX1-knockdown attenuated apoptosis induction. DTX1 binds c-FLIPL and directs it into the endosome-lysosomal pathway for proteasome-independent degradation. Moreover, induction of DTX1 in AGS cells by geldanamycin conferred susceptibility of those cells to TRAIL-induced apoptosis. Our results reveal a tumor-suppressive role for DTX1 and suggest a new approach to increasing TRAIL efficacy by raising DTX1 levels in gastric cancer therapy. DTX1 also enhanced c-FLIP degradation and FasL-induced and TRAIL-induced apoptosis in T cells, suggesting that DTX1 constitutes one of the physiological mechanisms regulating c-FLIP stability.

Expression of securin promotes colorectal cancer cell death via a p53-independent pathway after radiation.

Securin has been shown to regulate genomic stability; nevertheless, the role of securin on the cytotoxicity after radiation is still unclear. Exposure to 1-10 Gy X-ray radiation induced cell death in RKO colorectal cancer cells. The protein levels of securin, p53, and p21 were elevated by radiation. The proteins of phosphorylation of p53 at serine-15, which located on the nuclei of cancer cells, were highly induced by radiation. However, radiation increased securin proteins, which located on both of nuclei and cytoplasma in RKO cells. The p53-wild type colorectal cancer cells were more susceptible on cytotoxicity than the p53-mutant cells following exposure to radiation. Besides, the existence of securin in colorectal cancer cells induced higher apoptosis than the securin-null after radiation. Securin proteins were elevated by radiation in the p53-wild type and -mutant cells; furthermore, radiation raised the p53 protein expression in both the securin-wild type and -null cells. As a whole, these findings suggest that the existence of securin promotes apoptosis via a p53-indpendent pathway after radiation in human colorectal cancer cells.

Opposing securin and p53 protein expression in the oxaliplatin-induced cytotoxicity of human colorectal cancer cells.

Oxaliplatin, a clinical anticancer drug, has been used to treat colorectal cancer. Securin and p53 have been shown to regulate the cell cycle arrest and apoptosis. However, roles of securin and p53 on the oxaliplatin-induced cytotoxicity in human colorectal cancer cells remain unclear. Treatment with 1-10 microM oxaliplatin for 24 h induced the cell death, growth inhibition, and cell cycle arrest in RKO colorectal carcinoma cells. The phospho-p53 (Ser-15), total p53, and p21 proteins were elevated by oxaliplatin in RKO cells; conversely, oxaliplatin decreased the securin protein expression. The p53-functional RKO cells were higher on the cytotoxicity and cell cycle arrest at the G1 and G2/M phases than the p53-mutational SW480 cells after treatment with oxaliplatin. Oxaliplatin inhibited the securin protein expression in the p53-functional cells but not in the p53-mutational cells. The securin-wild type cells were more sensitive than the securin-null cells on the increases of cytotoxicity and sub-G1 fractions following treatment with oxaliplatin. Nevertheless, oxaliplatin elevated the activation of p53 in both securin-wild type and securin-null cells. As a whole, it is the first time to demonstrate that oxaliplatin inhibits the securin protein expression via a p53-dependent pathway, and p53 and securin may modulate the oxaliplatin-induced cytotoxicity in human colorectal cancer cells.

Tumour suppressor death-associated protein kinase targets cytoplasmic HIF-1α for Th17 suppression.

Death-associated protein kinase (DAPK) is a tumour suppressor. Here we show that DAPK also inhibits T helper 17 (Th17) and prevents Th17-mediated pathology in a mouse model of autoimmunity. We demonstrate that DAPK specifically downregulates hypoxia-inducible factor 1α (HIF-1α). In contrast to the predominant nuclear localization of HIF-1α in many cell types, HIF-1α is located in both the cytoplasm and nucleus in T cells, allowing for a cytosolic DAPK-HIF-1α interaction. DAPK also binds prolyl hydroxylase domain protein 2 (PHD2) and increases HIF-1α-PHD2 association. DAPK thereby promotes the proline hydroxylation and proteasome degradation of HIF-1α. Consequently, DAPK deficiency leads to excess HIF-1α accumulation, enhanced IL-17 expression and exacerbated experimental autoimmune encephalomyelitis. Additional knockout of HIF-1α restores the normal differentiation of Dapk(-/-) Th17 cells and prevents experimental autoimmune encephalomyelitis development. Our results reveal a mechanism involving DAPK-mediated degradation of cytoplasmic HIF-1α, and suggest that raising DAPK levels could be used for treatment of Th17-associated inflammatory diseases.