Carfilzomib activates ER stress and JNK/p38 MAPK signaling to promote apoptosis in hepatocellular carcinoma cells.

Hepatocellular carcinoma (HCC) is one of the most prevalent and deadly cancers in the world, which is frequently diagnosed at a late stage. HCC patients have a poor prognosis due to the lack of an efficacious therapeutic strategy. Approved drug repurposing is a way for accelerating drug discovery and can significantly reduce the cost of drug development. Carfilzomib (CFZ) is a second-generation proteasome inhibitor, which is highly efficacious against multiple myeloma and has been reported to possess potential antitumor activities against multiple cancers. However, the underlying mechanism of CFZ on HCC is still unclear. Here, we show that CFZ inhibits the proliferation of HCC cells through cell cycle arrest at the G2/M phase and suppresses the migration and invasion of HCC cells by inhibiting epithelial-mesenchymal transition. We also find that CFZ promotes reactive oxygen species production to induce endoplasmic reticulum (ER) stress and activate JNK/p38 MAPK signaling in HCC cells, thus inducing cell death in HCC cells. Moreover, CFZ significantly inhibits HCC cell growth in a xenograft mouse model. Collectively, our study elucidates that CFZ impairs mitochondrial function and activates ER stress and JNK/p38 MAPK signaling, thus inhibiting HCC cell and tumor growth. This indicates that CFZ has the potential as a therapeutic drug for HCC.

LonP1 Links Mitochondria-ER Interaction to Regulate Heart Function.

Interorganelle contacts and communications are increasingly recognized to play a vital role in cellular function and homeostasis. In particular, the mitochondria-endoplasmic reticulum (ER) membrane contact site (MAM) is known to regulate ion and lipid transfer, as well as signaling and organelle dynamics. However, the regulatory mechanisms of MAM formation and their function are still elusive. Here, we identify mitochondrial Lon protease (LonP1), a highly conserved mitochondrial matrix protease, as a new MAM tethering protein. The removal of LonP1 substantially reduces MAM formation and causes mitochondrial fragmentation. Furthermore, deletion of LonP1 in the cardiomyocytes of mouse heart impairs MAM integrity and mitochondrial fusion and activates the unfolded protein response within the ER (UPRER). Consequently, cardiac-specific LonP1 deficiency causes aberrant metabolic reprogramming and pathological heart remodeling. These findings demonstrate that LonP1 is a novel MAM-localized protein orchestrating MAM integrity, mitochondrial dynamics, and UPRER, offering exciting new insights into the potential therapeutic strategy for heart failure.

N-glycosylation stabilizes MerTK and promotes hepatocellular carcinoma tumor growth.

Despite the evidences of elevated expression of Mer tyrosine kinase (MerTK) in multiple human cancers, mechanisms underlying the oncogenic roles of MerTK in hepatocellular carcinoma (HCC) remains undefined. We explored the functional effects of MerTK and N-Glycosylated MerTK on HCC cell survival and tumor growth. Here, we show that MerTK ablation increases reactive oxygen species (ROS) production and promotes the switching from glycolytic metabolism to oxidative phosphorylation in HCC cells, thus suppressing HCC cell proliferation and tumor growth. MerTK is N-glycosylated in HCC cells at asparagine 294 and 454 that stabilizes MerTK to promote oncogenic transformation. Moreover, we observed that nuclear located non-glycosylated MerTK is indispensable for survival of HCC cells under stress. Pathologically, tissue microarray (TMA) data indicate that MerTK is a pivotal prognostic factor for HCC. Our data strongly support the roles of MerTK N-glycosylation in HCC tumorigenesis and suggesting N-glycosylation inhibition as a potential HCC therapeutic strategy.

[Analysis of Risk in Production of MRI and Some Suggestions for Field Inspection].

In recent years, with the wide application of magnetic resonance imaging (MRI) equipment in clinical practice, the quality of the equipment causes adverse events, which put pressure on manufacturers, at the same time, it puts forward higher requirements for medical device supervisors. In order to help the medical device supervisors to clarify the key points of verification, this paper analyzes the main risk points in the production process of the product according to the medical device good manufacturing practice(GMP), and puts forward the suggestions for field verification, which has practical significance for the submission of verification efficiency.

Ciclopirox and bortezomib synergistically inhibits glioblastoma multiforme growth via simultaneously enhancing JNK/p38 MAPK and NF-κB signaling.

Ciclopirox (CPX) is an antifungal drug that has recently been reported to act as a potential anticancer drug. However, the effects and underlying molecular mechanisms of CPX on glioblastoma multiforme (GBM) remain unknown. Bortezomib (BTZ) is the first proteasome inhibitor-based anticancer drug approved to treat multiple myeloma and mantle cell lymphoma, as BTZ exhibits toxic effects on diverse tumor cells. Herein, we show that CPX displays strong anti-tumorigenic activity on GBM. Mechanistically, CPX inhibits GBM cellular migration and invasion by reducing N-Cadherin, MMP9 and Snail expression. Further analysis revealed that CPX suppresses the expression of several key subunits of mitochondrial enzyme complex, thus leading to the disruption of mitochondrial oxidative phosphorylation (OXPHOS) in GBM cells. In combination with BTZ, CPX promotes apoptosis in GBM cells through the induction of reactive oxygen species (ROS)-mediated c-Jun N-terminal kinase (JNK)/p38 mitogen-activated protein kinase (MAPK) signaling. Moreover, CPX and BTZ synergistically activates nuclear factor kappa B (NF-κB) signaling and induces cellular senescence. Our findings suggest that a combination of CPX and BTZ may serve as a novel therapeutic strategy to enhance the anticancer activity of CPX against GBM.

Artemisinin suppresses hepatocellular carcinoma cell growth, migration and invasion by targeting cellular bioenergetics and Hippo-YAP signaling.

The primary liver cancer (PLC) is one of the leading causes of cancer-related death worldwide. The predominant form of PLC is hepatocellular carcinoma (HCC), which accounts for about 85% of all PLC. Artemisinin (ART) was clinically used as anti-malarial agents. Recently, it was demonstrated to inhibit cell growth and migration in multiple cancer types. However, the molecular mechanism underlying these anti-cancer activity remains largely unknown. Herein, it is discovered that ART dramatically suppresses HCC cell growth in vitro through arresting cell cycle progression, and represses cell migration and invasion via regulating N-cadherin-Snail-E-cadherin axis. In addition, the disruption of cellular bioenergetics contributed to ART-caused cell growth, migration and invasion inhibition. Moreover, ART (100 mg/kg, intraperitoneally) substantially inhibits HCC xenograft growth in vivo. Importantly, Hippo-YAP signal transduction is remarkably inactivated in HCC cells upon ART administration. Collectively, these data reveal a novel mechanism of ART in regulating HCC cell growth, migration, and invasion, which indicates that ART could be considered as a potential drug for the treatment of HCC.

Targeting the functional interplay between endoplasmic reticulum oxidoreductin-1α and protein disulfide isomerase suppresses the progression of cervical cancer.

BACKGROUND: Endoplasmic reticulum (ER) oxidoreductin-1α (Ero1α) and protein disulfide isomerase (PDI) constitute the pivotal pathway of oxidative protein folding, and are highly expressed in many cancers. However, whether targeting the functional interplay between Ero1α and PDI could be a new approach for cancer therapy remains unknown. METHODS: We performed wound healing assays, transwell migration and invasion assays and xenograft assays to assess cell migration, invasion and tumorigenesis; gel filtration chromatography, oxygen consumption assay and in cells folding assays were used to detect Ero1α-PDI interaction and Ero1α oxidase activity. FINDINGS: Here, we report that elevated expression of Ero1α is correlated with poor prognosis in human cervical cancer. Knockout of ERO1A decreases the growth, migration and tumorigenesis of cervical cancer cells, through downregulation of the H2O2-correlated epithelial-mesenchymal transition. We identify that the conserved valine (Val) 101 of Ero1α is critical for Ero1α-PDI complex formation and Ero1α oxidase activity. Val101 of Ero1α is specifically involved in the recognition of PDI catalytic domain. Mutation of Val101 results in a reduced ER, retarded oxidative protein folding and decreased H2O2 levels in the ER of cervical cancer cells and further impairs cell migration, invasion, and tumor growth. INTERPRETATION: Our study identifies the critical residue of Ero1α for recognizing PDI, which underlines the molecular mechanism of oxidative protein folding for tumorigenesis and provides a proof-of-concept for cancer therapy by targeting Ero1α-PDI interaction. FUND: This work was supported by National Key R&D Program of China, National Natural Science Foundation of China, and Youth Innovation Promotion Association, CAS.

Deferoxamine suppresses esophageal squamous cell carcinoma cell growth via ERK1/2 mediated mitochondrial dysfunction.

Deferoxamine (DFO) was found to modulate multiple cellular pathways involved in the growth of breast cancer, hepatocellular carcinoma, lung cancer and bladder cancer. However, the effect of DFO on esophageal squamous cell carcinoma (ESCC) remains unclear. Here, we report that DFO-treated ESCC cells show strong anti-tumorigenic properties, such as inhibition of cell proliferation, induction of cell cycle arrest, and promotion of apoptosis. Mechanistically, DFO significantly activated ERK1/2 signaling, which is reactive oxygen species (ROS)-dependent. ERK1/2 activation suppressed mitochondrial respiration and aerobic glycolysis in ESCC cells, resulting in reduced production of ATP and key precursor metabolites. Cell proliferation was functionally rescued by the ROS scavenger N-acetyl-l-cysteine (NAC) and the ERK1/2 inhibitor SCH7 72984. Additionally, our data showed that activated ERK1/2 was partially translocated to the mitochondria, which indicated that DFO-activated ERK1/2 may suppress tumor formation through inhibition of mitochondrial respiration. Moreover, the decreased c-Myc expression caused by DFO resulted in the inhibition of cell migration. Taken together, our study demonstrate that DFO activates ERK1/2 and downregulates c-Myc to perturb mitochondrial homeostasis and promote apoptosis, resulting in the novel anti-neoplastic activity of DFO in ESCC.

Human Elongation Factor 4 Regulates Cancer Bioenergetics by Acting as a Mitochondrial Translation Switch.

Mitochondria regulate cellular bioenergetics and redox states and influence multiple signaling pathways required for tumorigenesis. In this study, we determined that the mitochondrial translation elongation factor 4 (EF4) is a critical component of tumor progression. EF4 was ubiquitous in human tissues with localization to the mitochondria (mtEF4) and performed quality control on respiratory chain biogenesis. Knockout of mtEF4 induced respiratory chain complex defects and apoptosis, while its overexpression stimulated cancer development. In multiple cancers, expression of mtEF4 was increased in patient tumor tissues. These findings reveal that mtEF4 expression may promote tumorigenesis via an imbalance in the regulation of mitochondrial activities and subsequent variation of cellular redox. Thus, dysregulated mitochondrial translation may play a vital role in the etiology and development of diverse human cancers.Significance: Dysregulated mitochondrial translation drives tumor development and progression. Cancer Res; 78(11); 2813-24. ©2018 AACR.

Oxidative stress regulates cellular bioenergetics in esophageal squamous cell carcinoma cell.

The aim of the present study was to explore the effects of oxidative stress induced by CoCl2 and H2O2 on the regulation of bioenergetics of esophageal squamous cell carcinoma (ESCC) cell line TE-1 and analyze its underlying mechanism. Western blot results showed that CoCl2 and H2O2 treatment of TE-1 cells led to significant reduction in mitochondrial respiratory chain complex subunits expression and increasing intracellular reactive oxygen species (ROS) production. We further found that TE-1 cells treated with CoCl2, a hypoxia-mimicking reagent, dramatically reduced the oxygen consumption rate (OCR) and increased the extracellular acidification rate (ECAR). However, H2O2 treatment decreased both the mitochondrial respiration and aerobic glycolysis significantly. Moreover, we found that H2O2 induces apoptosis in TE-1 cells through the activation of PARP, Caspase 3, and Caspase 9. Therefore, our findings indicate that CoCl2 and H2O2 could cause mitochondrial dysfunction by up-regulation of ROS and regulating the cellular bioenergy metabolism, thus affecting the survival of tumor cells.

Tetramethylpyrazine blocks TFAM degradation and up-regulates mitochondrial DNA copy number by interacting with TFAM.

The natural small molecule compound: 2,3,5,6-tetramethylpyrazine (TMP), is a major component of the Chinese medicine Chuanxiong, which has wide clinical applications in dilating blood vessels, inhibiting platelet aggregation and treating thrombosis. Recent work suggests that TMP is also an antitumour agent. Despite its chemotherapeutic potential, the mechanism(s) underlying TMP action are unknown. Herein, we demonstrate that TMP binds to mitochondrial transcription factor A (TFAM) and blocks its degradation by the mitochondrial Lon protease. TFAM is a key regulator of mtDNA replication, transcription and transmission. Our previous work showed that when TFAM is not bound to DNA, it is rapidly degraded by the ATP-dependent Lon protease, which is essential for mitochondrial proteostasis. In cultured cells, TMP specifically blocks Lon-mediated degradation of TFAM, leading to TFAM accumulation and subsequent up-regulation of mtDNA content in cells with substantially low levels of mtDNA. In vitro protease assays show that TMP does not directly inhibit mitochondrial Lon, rather interacts with TFAM and blocks degradation. Pull-down assays show that biotinylated TMP interacts with TFAM. These findings suggest a novel mechanism whereby TMP stabilizes TFAM and confers resistance to Lon-mediated degradation, thereby promoting mtDNA up-regulation in cells with low mtDNA content.

Paclitaxel induces apoptosis of esophageal squamous cell carcinoma cells by downregulating STAT3 phosphorylation at Ser727.

Paclitaxel induces apoptosis in a variety of cancer cells. However, the mechanism of paclitaxel inducing apoptosis in human esophageal squamous cell carcinoma (ESCC) remains to be defined. In this study, we found that paclitaxel-induced apoptosis by increasing the relevant apoptosis protein expression and the release of cytochrome c via downregulation of signal transducer and activator of transcription 3 (STAT3) and phospho-STAT3 (Ser727). In addition, paclitaxel treatment of ESCC cells EC-1 and Eca-109 led to marked mitochondrial membrane potential depolarization and significantly increasing of reactive oxygen species. Moreover, paclitaxel treatment resulted in the inhibition of mitochondrial respiration. In conclusion, our findings reveal that paclitaxel induced apoptosis in both EC-1 and Eca-109 cells through the reduction of STAT3 and phospho­STAT3 (Ser727) level, and suggest that paclitaxel may be of therapeutic potential in the treatment of ESCC through the induction of mitochondrial apoptosis in ESCC cells.

Downregulation of TFAM inhibits the tumorigenesis of non-small cell lung cancer by activating ROS-mediated JNK/p38MAPK signaling and reducing cellular bioenergetics.

Mitochondrial transcription factor A (TFAM) is essential for the replication, transcription and maintenance of mitochondrial DNA (mtDNA). The role of TFAM in non-small cell lung cancer (NSCLC) remains largely unknown. Herein, we report that downregulation of TFAM in NSCLC cells resulted in cell cycle arrest at G1 phase and significantly blocked NSCLC cell growth and migration through the activation of reactive oxygen species (ROS)-induced c-Jun amino-terminal kinase(JNK)/p38 MAPK signaling and decreased cellular bioenergetics. We further found that TFAM downregulation in NSCLC cells led to increased apoptotic cell death and enhanced the sensitivity of NSCLC cells to cisplatin. Tissue microarray (TMA) data showed that elevated expression of TFAM was related to the histological grade and TNM stage of NSCLC patients. We also demonstrated that TFAM is an independent prognostic factor for overall survival of NSCLC patients. Taken together, our findings suggest that TFAM could serve as a potential diagnostic biomarker and molecular target for the treatment of NSCLC, as well as for prediction of the effectiveness of chemotherapy.

Reciprocal regulation of Abl kinase by Crk Y251 and Abi1 controls invasive phenotypes in glioblastoma.

Crk is the prototypical member of a class of Src homology 2 (SH2) and Src homology 3 (SH3) domain-containing adaptor proteins that positively regulate cell motility via the activation of Rac1 and, in certain tumor types such as GBM, can promote cell invasion and metastasis by mechanisms that are not well understood. Here we demonstrate that Crk, via its phosphorylation at Tyr251, promotes invasive behavior of tumor cells, is a prominent feature in GBM, and correlating with aggressive glioma grade IV staging and overall poor survival outcomes. At the molecular level, Tyr251 phosphorylation of Crk is negatively regulated by Abi1, which competes for Crk binding to Abl and attenuates Abl transactivation. Together, these results show that Crk and Abi1 have reciprocal biological effects and act as a molecular rheostat to control Abl activation and cell invasion. Finally, these data suggest that Crk Tyr251 phosphorylation regulate invasive cell phenotypes and may serve as a biomarker for aggressive GBM.

Mitochondrial Lon protease at the crossroads of oxidative stress, ageing and cancer.

Lon protease is a nuclear DNA-encoded mitochondrial enzyme highly conserved throughout evolution, involved in the degradation of damaged and oxidized proteins of the mitochondrial matrix, in the correct folding of proteins imported in mitochondria, and in the maintenance of mitochondrial DNA. Lon expression is induced by various stimuli, including hypoxia and reactive oxygen species, and provides protection against cell stress. Lon down-regulation is associated with ageing and with cell senescence, while up-regulation is observed in tumour cells, and is correlated with a more aggressive phenotype of cancer. Lon up-regulation contributes to metabolic reprogramming observed in cancer, favours the switch from a respiratory to a glycolytic metabolism, helping cancer cell survival in the tumour microenvironment, and contributes to epithelial to mesenchymal transition. Silencing of Lon, or pharmacological inhibition of its activity, causes cell death in various cancer cells. Thus, Lon can be included in the growing class of proteins that are not responsible for oncogenic transformation, but that are essential for survival and proliferation of cancer cells, and that can be considered as a new target for development of anticancer drugs.

Inhibition of Lon blocks cell proliferation, enhances chemosensitivity by promoting apoptosis and decreases cellular bioenergetics of bladder cancer: potential roles of Lon as a prognostic marker and therapeutic target in baldder cancer.

ATP-dependent Lon protease within mitochondrial matrix contributes to the degradation of abnormal proteins. The oxidative or hypoxic stress which represents the stress phenotype of cancer leads to up-regulation of Lon. However, the role of Lon in bladder cancer remains undefined. Here, we found that Lon expression in bladder cancer tissues was significantly higher than those in noncancerous tissues; down-regulation of Lon in bladder cancer cells significantly blocked cancer cell proliferation via suppression c-Jun N-terminal kinase (JNK) phosphorylation due to decreased reactive oxygen species (ROS) production and enhanced the sensitivity of bladder cancer cells to chemotherapeutic agents by promoting apoptosis. We further found that Lon down-regulation in bladder cancer cells decreased cellular bioenergetics as determined by measuring aerobic respiration and glycolysis using extracellular flux analyzer. The tissue microarray (TMA) results showed that high expression of Lon was related to the T and TNM stage, as well as histological grade of bladder cancer patients. We also demonstrated that Lon was an independent prognostic factor for overall survival of bladder cancer. Taken together, our data suggest that Lon could serve as a potential diagnostic biomarker and therapeutic target for treatment of bladder cancer, as well as for prediction of the effectiveness of chemotherapy.

Association of p53/p21 expression and cigarette smoking with tumor progression and poor prognosis in non-small cell lung cancer patients.

Non-small cell lung cancer (NSCLC) accounts for approximately 80-85% of all lung cancer cases. Cigarette smoking is the number one risk factor which is attributed to more than four out of five cases of lung cancers. The prognostic impact of cell cycle regulation-associated tumor suppressors including p53 and p21 for NSCLC is still controversial. In the present study, we examined p53 and p21 expression using immunoblotting in tumor and adjacent non-cancerous tissues from NSCLC patients. Moreover, tissue microarrays (TMAs) including 150 specimens was used to examine p53 and p21 expression by immunohistochemical staining (IHC). The association between p53/p21 and various clinicopathological characteristics was evaluated. Kaplan-Meier overall survival was used to analyze the association between p53/p21 expression and prognosis of NSCLC patients, as well as the association of cigarette smoking with p53/p21 expression and prognosis. The results of the immunoblotting showed that expression of p53 and p21 in tumor tissues was significantly higher than that in the matched adjacent non-cancerous tissues (P<0.001 and P<0.05, respectively). The IHC results showed that 50.67% of the cases had high expression of p21; however, the percentage of patients having high expression of p53 was 31.3%. Univariate and Cox regression models were used to evaluate the factors related to prognosis with p53 and p21 expression. Multivariate analysis indicated that p53 expression was an independent prognostic factor for NSCLC (P=0.005), while p21 could not serve as an independent prognostic factor (P=0.123). In addition, smoking history was closely related to lung cancer risk (P=0.041), but could not be an independent assessment factor (P=0.740). In this study, we further demonstrated the association of p53/p21 expression and cigarette smoking. Our results suggest that cigarette smoking and overexpression of p53 or p21 are associated with poor prognosis. The combination of p53/p21 expression and smoking history may be a useful biomarker for tumor progression and prognosis of NSCLC patients.

Elevated p53 expression levels correlate with tumor progression and poor prognosis in patients exhibiting esophageal squamous cell carcinoma.

Esophageal squamous cell carcinoma (ESCC) is the most common histological subtype of esophageal cancer and one of the most aggressive types of malignancy, with a high rate of mortality. Early diagnosis and treatment may improve the prognosis of ESCC and, thus, survival rates. As a significant tumor suppressor, p53 is closely associated with apoptosis and the differentiation of cancer cells. The present study evaluated the expression levels of the p53 protein and the clinical significance in patients presenting with ESCC. The p53 protein expression level of 64 paired ESCC and tumor-adjacent normal tissues was evaluated using western blot analysis. In addition, immunohistochemistry (IHC) was performed to detect the p53 expression level in specimens from 118 paraffin-embedded cancerous tissues. The correlation of the p53 expression level with the clinicopathological parameters and prognosis of the ESCC patients was also analyzed. The p53 protein was identified to be highly expressed in the ESCC tissue, with western blot analysis demonstrating that the expression level of p53 in the cancerous tissue was 1.89 times that of the tumor-adjacent normal tissue (P<0.001); furthermore, IHC indicated that there was a marked positive expression of p53 in the ESCC tissue (49.15%). The expression level of p53 protein was identified to be significantly correlated with the tumor grade (P<0.001), N stage (P=0.010). Additionally, the higher level of p53 expression was found to be associated with a poor survival rate in the ESCC patients (P=0.0404). The univariate analysis showed that the survival time of patients was significantly correlated with the T stage (RR=3.886, P<0.001), N stage (lymph node metastasis; RR=3.620, P<0.001) and TNM stage (RR=3.576, P<0.001). Furthermore, the multivariate analysis revealed that the T stage (RR=3.988, P<0.001) and N stage (RR=4.240, P=0.004) significantly influenced the overall survival of the ESCC patients.

Overexpression of MERTK receptor tyrosine kinase in epithelial cancer cells drives efferocytosis in a gain-of-function capacity.

MERTK, a member of the TAM (TYRO3, AXL, and MERTK) receptor tyrosine kinases, has complex and diverse roles in cell biology. On the one hand, knock-out of MERTK results in age-dependent autoimmunity characterized by failure of apoptotic cell clearance, while on the other, MERTK overexpression in cancer drives classical oncogene pathways leading to cell transformation. To better understand the interplay between cell transformation and efferocytosis, we stably expressed MERTK in human MCF10A cells, a non-tumorigenic breast epithelial cell line devoid of endogenous MERTK. While stable expression of MERTK in MCF10A resulted in enhanced motility and AKT-mediated chemoprotection, MERTK-10A cells did not form stable colonies in soft agar, or enhance proliferation compared with parental MCF10A cells. Concomitant to chemoresistance, MERTK also stimulated efferocytosis in a gain-of-function capacity. However, unlike AXL, MERTK activation was highly dependent on apoptotic cells, suggesting MERTK may preferentially interface with phosphatidylserine. Consistent with this idea, knockdown of MERTK in breast cancer cells MDA-MB 231 reduced efferocytosis, while transient or stable expression of MERTK stimulated apoptotic cell clearance in all cell lines tested. Moreover, human breast cancer cells with higher endogenous MERTK showed higher levels of efferocytosis that could be blocked by soluble TAM receptors. Finally, through MERTK, apoptotic cells induced PD-L1 expression, an immune checkpoint blockade, suggesting that cancer cells may adopt MERTK-driven efferocytosis as an immune suppression mechanism for their advantage. These data collectively identify MERTK as a significant link between cancer progression and efferocytosis, and a potentially unrealized tumor-promoting event when MERTK is overexpressed in epithelial cells.

Prevalence of antibody to Toxoplasma gondii in black-headed gulls (Chroicocephalus ridibundus), Dianchi Lake, China.

Sera from 659 Black-headed Gulls (Chroicocephalus ridibundus) in Dianchi Lake, China were assayed for Toxoplasma gondii antibodies using the modified agglutination test (MAT). Specific T. gondii antibodies were detected in 131 (19.9%) Black-headed Gulls (MAT titer ≥ 1 ∶ 5). These results indicate that T. gondii infection is common in Black-headed Gulls.