XELOX (capecitabine plus oxaliplatin) plus bevacizumab (anti-VEGF-A antibody) with or without adoptive cell immunotherapy in the treatment of patients with previously untreated metastatic colorectal cancer: a multicenter, open-label, randomized, controlled, phase 3 trial.

Fluoropyrimidine-based combination chemotherapy plus targeted therapy is the standard initial treatment for unresectable metastatic colorectal cancer (mCRC), but the prognosis remains poor. This phase 3 trial (ClinicalTrials.gov: NCT03950154) assessed the efficacy and adverse events (AEs) of the combination of PD-1 blockade-activated DC-CIK (PD1-T) cells with XELOX plus bevacizumab as a first-line therapy in patients with mCRC. A total of 202 participants were enrolled and randomly assigned in a 1:1 ratio to receive either first-line XELOX plus bevacizumab (the control group, n = 102) or the same regimen plus autologous PD1-T cell immunotherapy (the immunotherapy group, n = 100) every 21 days for up to 6 cycles, followed by maintenance treatment with capecitabine and bevacizumab. The main endpoint of the trial was progression-free survival (PFS). The median follow-up was 19.5 months. Median PFS was 14.8 months (95% CI, 11.6-18.0) for the immunotherapy group compared with 9.9 months (8.0-11.8) for the control group (hazard ratio [HR], 0.60 [95% CI, 0.40-0.88]; p = 0.009). Median overall survival (OS) was not reached for the immunotherapy group and 25.6 months (95% CI, 18.3-32.8) for the control group (HR, 0.57 [95% CI, 0.33-0.98]; p = 0.043). Grade 3 or higher AEs occurred in 20.0% of patients in the immunotherapy group and 23.5% in the control groups, with no toxicity-associated deaths reported. The addition of PD1-T cells to first-line XELOX plus bevacizumab demonstrates significant clinical improvement of PFS and OS with well tolerability in patients with previously untreated mCRC.

N6-methyladenosine-modified VGLL1 promotes ovarian cancer metastasis through high-mobility group AT-hook 1/Wnt/ß-catenin signaling.

The main causes of death in patients with ovarian cancer (OC) are invasive lesions and the spread of metastasis. The present study aimed to explore the mechanisms that might promote OC metastasis. Here, we identified that VGLL1 expression was remarkably increased in metastatic OC samples. The role of VGLL1 in OC metastasis and tumor growth was examined by cell function assays and mouse models. Mechanistically level, METTL3-mediated N6-methyladenosine (m6A) modification contributed to VGLL1 upregulation in an IGF2BP2 recognition-dependent manner. Furthermore, VGLL1 directly interacts with TEAD4 and co-transcriptionally activates HMGA1. HMGA1 further activates Wnt/ß-catenin signaling to enhance OC metastasis by promoting the epithelial-mesenchyme transition traits. Rescue assays indicated that the upregulation of HMGA1 was essential for VGLL1-induced metastasis. Collectively, these findings showed that the m6A-induced VGLL1/HMGA1/ß-catenin axis might play a vital role in OC metastasis and tumor growth. VGLL1 might serve as a prognostic marker and therapeutic target against the metastasis of OC.

DNA of neutrophil extracellular traps binds TMCO6 to impair CD8+ T-cell immunity in hepatocellular carcinoma.

Neutrophil extracellular traps (NETs), formed by the extracellular release of decondensed chromatin and granules, have been shown to promote tumor progression and metastasis. Tumor-associated neutrophils in hepatocellular carcinoma (HCC) are prone to NET formation, highlighting the need for a more comprehensive understanding of the mechanisms of action of NETs in liver cancer. Here, we showed that DNA of NETs (NET-DNA) binds transmembrane and coiled-coil domains 6 (TMCO6) on CD8+ T cells to impair anti-tumor immunity and thereby promote HCC progression. TGF-ß1 induced NET formation, which recruited CD8+ T cells. Binding to NET-DNA inhibited CD8+ T cells function while increasing apoptosis and TGF-ß1 secretion, forming a positive feedback loop to further stimulate NET formation and immunosuppression. Mechanistically, the N-terminus of TMCO6 interacted with NET-DNA and suppressed T-cell receptor signaling and NF-κB p65 nuclear translocation. Blocking NET formation by inhibiting PAD4 induced potent antitumor effects in wild-type mice but not TMCO6-/- mice. In clinical samples, CD8+ T cells expressing TMCO6 had an exhausted phenotype. TGF-ß1-signaling inhibition or TMCO6 deficiency combined with anti-PD-1 abolished NET-driven HCC progression in vivo. Collectively, this study unveils the role of NET-DNA in impairing CD8+ T-cell immunity by binding TMCO6 and identifies targeting this axis as an immunotherapeutic strategy for blocking HCC progression.

Targeted delivery of a PD-1-blocking scFv by CD133-specific CAR-T cells using nonviral Sleeping Beauty transposition shows enhanced antitumour efficacy for advanced hepatocellular carcinoma.

BACKGROUND: CD133 is considered a marker for cancer stem cells (CSCs) in several types of tumours, including hepatocellular carcinoma (HCC). Chimeric antigen receptor-specific T (CAR-T) cells targeting CD133-positive CSCs have emerged as a tool for the clinical treatment of HCC, but immunogenicity, the high cost of clinical-grade recombinant viral vectors and potential insertional mutagenesis limit their clinical application. METHODS: CD133-specific CAR-T cells secreting PD-1 blocking scFv (CD133 CAR-T and PD-1 s cells) were constructed using a sleeping beauty transposon system from minicircle technology, and the antitumour efficacy of CD133 CAR-T and PD-1 s cells was analysed in vitro and in vivo. RESULTS: A univariate analysis showed that CD133 expression in male patients at the late stage (II and III) was significantly associated with worse progression-free survival (PFS) (P = 0.0057) and overall survival (OS) (P = 0.015), and a multivariate analysis showed a trend toward worse OS (P = 0.041). Male patients with advanced HCC exhibited an approximately 20-fold higher PD-L1 combined positive score (CPS) compared with those with HCC at an early stage. We successfully generated CD133 CAR-T and PD-1 s cells that could secrete PD-1 blocking scFv based on a sleeping beauty system involving minicircle vectors. CD133 CAR-T and PD-1 s cells exhibited significant antitumour activity against HCC in vitro and in xenograft mouse models. Thus, CD133 CAR-T and PD-1 s cells may be a therapeutically tractable strategy for targeting CD133-positive CSCs in male patients with advanced HCC. CONCLUSIONS: Our study provides a nonviral strategy for constructing CAR-T cells that could also secrete checkpoint blockade inhibitors based on a Sleeping Beauty system from minicircle vectors and revealed a potential benefit of this strategy for male patients with advanced HCC and high CD133 expression (median immunohistochemistry score > 2.284).

Lenvatinib improves anti-PD-1 therapeutic efficacy by promoting vascular normalization via the NRP-1-PDGFRß complex in hepatocellular carcinoma.

Introduction: The limited response to immune checkpoint blockades (ICBs) in patients with hepatocellular carcinoma (HCC) highlights the urgent need for broadening the scope of current immunotherapy approaches. Lenvatinib has been shown a potential synergistic effect with ICBs. This study investigated the optimal method for combining these two therapeutic agents and the underlying mechanisms. Methods: The effect of lenvatinib at three different doses on promoting tissue perfusion and vascular normalization was evaluated in both immunodeficient and immunocompetent mouse models. The underlying mechanisms were investigated by analyzing the vascular morphology of endothelial cells and pericytes. The enhanced immune infiltration of optimal-dose lenvatinib and its synergistic effect of lenvatinib and anti-PD-1 antibody was further evaluated by flow cytometry and immunofluorescence imaging. Results: There was an optimal dose that superiorly normalized tumor vasculature and increased immune cell infiltration in both immunodeficient and immunocompetent mouse models. An adequate concentration of lenvatinib strengthened the integrity of human umbilical vein endothelial cells by inducing the formation of the NRP-1-PDGFRß complex and activating the Crkl-C3G-Rap1 signaling pathway in endothelial cells. Additionally, it promoted the interaction between endothelial cells and pericytes by inducing tyrosine-phosphorylation in pericytes. Furthermore, the combination of an optimal dose of lenvatinib and an anti-PD-1 antibody robustly suppressed tumor growth. Conclusions: Our study proposes a mechanism that explains how the optimal dose of lenvatinib induces vascular normalization and confirms its enhanced synergistic effect with ICBs.

Medical Consultations Option and Influencing Factors for SARS-CoV-2 Infected Individuals - Beijing Municipality, China, December 2022.

What is already known about this topic?: In December 2022, China revised its epidemic prevention and control strategy, leading to an increase in coronavirus disease 2019 (COVID-19) cases and a peak in medical consultations. Government departments implemented relevant policies to coordinate and allocate medical resources throughout China. However, there is a scarcity of research on the status of medical consultations and the factors influencing them. What is added by this report?: In the study population, over 80% of individuals with COVID-19 chose not to pursue medical care, while more than 70% of patients who sought treatment opted for primary healthcare facilities. The decision to consult medical professionals was influenced by various factors, such as age, education level, employment status, urban-rural distribution, and the presence of symptoms following COVID-19 infection. What are the implications for public health practice?: The implementation of tiered diagnostic and treatment approaches, aligned with guidelines issued by governing bodies, is essential for mitigating the strain on medical resources. Primary healthcare institutions serve as "gatekeepers" for public health and should be further expanded in the future.

BMP9-induced vascular normalisation improves the efficacy of immunotherapy against hepatitis B virus-associated hepatocellular carcinoma.

BACKGROUND: In the past decade, the field of tumour immunotherapy has made a great progress. However, the efficacy of immune checkpoint blocking (ICB) in the treatment of hepatocellular carcinoma (HCC) remains limited. Cytotoxic lymphocyte trafficking into tumours is critical for the success of ICB. Therefore, additional strategies that increase cytotoxic lymphocyte trafficking into tumours are urgently needed to improve patient immune responses. METHODS: Paired adjacent tissue and cancerous lesions with HBV-associated HCC were subjected to RNA-seq analysis. Bone morphogenetic protein (BMP9), which reflects vessel normalisation, was identified through Cytoscape software, clinical specimens and Gene Expression Omnibus (GEO) datasets for HCC. The functional effects and mechanism of BMP9 on the tumour vasculature were evaluated in cells and animals. An ultrasound-targeted microbubble destruction (UTMD)-mediated BMP9 delivery strategy was used to normalise the vasculature and evaluate therapeutic efficacy mediated by cytotoxic lymphocytes (NK cells) in combination with a PD-L1 antibody in human cancer xenografts of immune-deficient mice. RESULTS: We discovered that hepatitis B virus (HBV) infection-induced downregulation of BMP9 expression correlated with a poor prognosis and pathological vascular abnormalities in patients with HCC. BMP9 overexpression in HBV-infected HCC cells promoted intra-tumoural cytotoxic lymphocyte infiltration via vascular normalisation by inhibiting the Rho-ROCK-myosin light chain (MLC) signalling cascade, resulting in enhanced efficacy of immunotherapy. Furthermore, UTMD-mediated BMP9 delivery restored the anti-tumour function of cytotoxic lymphocytes (NK cells) and showed therapeutic efficacy in combination with a PD-L1 antibody in human cancer xenografts of immune-deficient mice. CONCLUSIONS: HBV-induced BMP9 downregulation causes vascular abnormalities that inhibit intra-tumoural cytotoxic lymphocyte infiltration, providing a rationale for developing and combining immunotherapy with BMP9-based therapy to treat HBV-associated HCC.

Alarmin IL-33 orchestrates antitumoral T cell responses to enhance sensitivity to 5-fluorouracil in colorectal cancer.

Rationale: Resistance to 5-fluorouracil (5-FU) chemotherapy remains the main barrier to effective clinical outcomes for patients with colorectal cancer (CRC). A better understanding of the detailed mechanisms underlying 5-FU resistance is needed to increase survival. Interleukin (IL)-33 is a newly discovered alarmin-like molecule that exerts pro- and anti-tumorigenic effects in various cancers. However, the precise role of IL-33 in CRC progression, as well as in the development of 5-FU resistance, remains unclear. Methods: High-quality RNA-sequencing analyses were performed on matched samples from patients with 5-FU-sensitive and 5-FU-resistant CRC. The clinical and biological significance of IL-33, including its effects on both T cells and tumor cells, as well as its relationship with 5-FU chemotherapeutic activity were examined in ex vivo, in vitro and in vivo models of CRC. The molecular mechanisms underlying these processes were explored. Results: IL-33 expressed by tumor cells was a dominant mediator of antitumoral immunity in 5-FU-sensitive patients with CRC. By binding to its ST2 receptor, IL-33 triggered CD4+ (Th1 and Th2) and CD8+ T cell responses by activating annexin A1 downstream signaling cascades. Mechanistically, IL-33 enhanced the sensitivity of CRC cells to 5-FU only in the presence of T cells, which led to the activation of both tumor cell-intrinsic apoptotic and immune killing-related signals, thereby synergizing with 5-FU to induce apoptosis of CRC cells. Moreover, injured CRC cells released more IL-33 and the T cell chemokines CXCL10 and CXCL13, forming a positive feedback loop to further augment T cell responses. Conclusions: Our results identified a previously unrecognized connection between IL-33 and enhanced sensitivity to 5-FU. IL-33 created an immune-active tumor microenvironment by orchestrating antitumoral T cell responses. Thus, IL-33 is a potential predictive biomarker for 5-FU chemosensitivity and favorable prognosis and has potential as a promising adjuvant immunotherapy to improve the clinical benefits of 5-FU-based therapies in the treatment of CRC.

EBV-Upregulated B7-H3 Inhibits NK cell-Mediated Antitumor Function and Contributes to Nasopharyngeal Carcinoma Progression.

Nasopharyngeal carcinoma (NPC) is an Epstein-Barr virus (EBV)-associated epithelial malignancy characterized by the presence of prominent infiltration of lymphocytes, including natural killer (NK) cells. Although NK cells can directly target EBV-infected tumor cells without restriction by the MHC, EBV-positive (EBV+) NPC cells often develop resistance mechanisms that allow them to evade immune surveillance by NK cells. Elucidating the mechanisms involved in EBV-induced NK-cell dysfunction will contribute to the design of novel NK cell-based immunotherapies to treat NPC. Herein, we confirmed that the cytotoxic function of NK cells was impaired in EBV+ NPC tissues and found that EBV infection-induced expression of B7-H3 in NPC negatively correlated with NK-cell function. The inhibitory effect of EBV+ tumor expression of B7-H3 on NK-cell function was clarified in vitro and in vivo. Mechanistically, activation of the PI3K/AKT/mTOR signaling pathway via EBV latent membrane protein 1 (LMP1) was responsible for EBV infection-induced upregulation of B7-H3 expression. In an NPC xenograft mouse model with adoptive transfer of primary NK cells, deletion of B7-H3 on tumor cells in combination with anti-PD-L1 treatment restored NK cell-mediated antitumor activity and significantly improved the antitumor efficacy of NK cells. On the basis of our findings, we conclude that EBV infection can inhibit NK cell-mediated antitumor function by inducing upregulation of B7-H3 expression and provide a rationale for NK cell-based immunotherapies in combination of PD-L1 blockade and overcoming the immunosuppression of B7-H3 to treat EBV-associated NPC.

MELD 3.0 Score for Predicting Survival in Patients with Cirrhosis After Transjugular Intrahepatic Portosystemic Shunt Creation.

BACKGROUND AND AIMS: The selection of appropriate candidates for transjugular intrahepatic portosystemic shunt (TIPS) is important and challenging. To validate the Model for End-Stage Liver Disease (MELD) 3.0 in predicting mortality in patients with cirrhosis after TIPS creation. METHODS: A total of 855 consecutive patients with cirrhosis from December 2011 to October 2019 who underwent TIPS placement were retrospectively reviewed. The prognostic value of the MELD 3.0, MELD, MELD-Na, Child-Pugh and FIPS score was assessed using Harrell's C concordance index (c-index). The Hosmer-Lemeshow test was used to test the goodness of fit of all models and the calibration plot was drawn. RESULTS: The c-index of the MELD 3.0 in predicting 3-month mortality was 0.727 (0.645-0.808), which were significantly superior to the MELD (0.663 [0.565-0.761]; P = 0.015), MELD-Na (0.672 [0.577-0.768]; P = 0.008) and FIPS (0.582 [0.477-0.687]; P = 0.015). The Child-Pugh score reached c-indices of 0.754 (0.673-0.835), 0.720 (0.649-0.792), 0.705 (0.643-0.766) and 0.665 (0.614-0.716) for 3-month, 6-month, 1-year, and 2-year mortality, respectively, which seems comparable to MELD 3.0. A MELD 3.0 of 14 could be used as a cut-off point for discriminating between high- and low-risk patients. The MELD 3.0 could stratify patients with Child-Pugh grade B (log-rank P < 0.001). The Child-Pugh score could stratify patients defined as low risk by MELD 3.0 (log-rank P < 0.001). CONCLUSIONS: The MELD 3.0 was significantly superior to the MELD, MELD-Na and FIPS scores in predicting mortality in patients with cirrhosis after TIPS creation.

Adjuvant alternative cytokine-induced killer cell combined with natural killer cell immunotherapy improves the prognosis of post-mastectomy breast cancer.

Breast cancer is one of the most common cancers in women. Triple-negative breast cancer (TNBC) has a significantly worse prognosis due to the lack of endocrine receptors including estrogen receptor (ER), progesterone receptor (PR) and human epidermal growth factor receptor 2 (HER2). In this study, we investigated adjuvant cellular immunotherapy (CIT) in patients with post-mastectomy breast cancer. We enrolled 214 post-mastectomy breast cancer patients, including 107 patients in the control group (who received chemotherapy/radiotherapy/endocrine therapy) and the other 107 patients in the CIT group (who received chemotherapy/radiotherapy/endocrine therapy and subsequent immune cell infusion). Of these 214 patients, 54 had TNBC, including 26 patients in the control group and 28 patients in the CIT group. Survival analysis showed that the overall survival rate of patients treated with cellular immunotherapy was higher than that of patients who were not treated with CIT. Compared to those who received cytokine-induced killer (CIK) cells alone, the patients who received CIK combined with natural killer (NK) cell immunotherapy showed the best overall survival rate. In subgroup analyses, adjuvant CIT significantly improved the overall survival of patients in the TNBC subgroup and the patients who were aged over 50 years. Our study indicates that adjuvant CIK cell combined with NK cell treatment is an effective therapeutic strategy to prolong the survival of post-mastectomy patients, particularly for TNBC patients and those who are aged over 50 years.

OTUD4-mediated GSDME deubiquitination enhances radiosensitivity in nasopharyngeal carcinoma by inducing pyroptosis.

BACKGROUND: Radioresistance is the primary cause of nasopharyngeal carcinoma (NPC) treatment failure. Previous studies have focused on the deficits in cellular apoptosis as a mechanism for radioresistance; however, additional potential death modes involved in modulating radiosensitivity of NPC have not been explored. METHODS: Pyroptosis was assessed by phase-contrast imaging, LDH release assays, live cell imaging, and Western blotting. In vitro and in vivo assays were used to investigate the function of gasdermin E (GSDME) and ovarian tumor family deubiquitinase 4 (OTUD4). NPC tissues were analyzed using Western blotting, immunohistochemistry, and real-time PCR. The molecular mechanism was determined using immunoprecipitation assays and mass spectrometry. RESULTS: Live cell imaging revealed that 40-75% of irradiation-induced dead NPC cells were pyroptotic cells. Furthermore, irradiation-induced pyroptosis is triggered by GSDME, which are cleaved by activated caspase-3 in the intrinsic mitochondrial pathway. Additionally, GSDME was significantly downregulated in radioresistant NPC specimens. Low GSDME expression was a predictor of worse prognosis and conferred NPC radioresistance both in vitro and in vivo. Mechanistically, OTUD4 deubiquitinated and stabilized GSDME, enhancing radiosensitivity of NPC cells by promoting pyroptosis. Clinically, OTUD4 was significantly correlated with GSDME in NPC biopsies, and patients with low expression of both OTUD4 and GSDME suffered the worst radiotherapy response and survival. CONCLUSIONS: GSDME-dependent pyroptosis is a critical determinant of radiosensitivity in NPC, and is modulated by OTUD4 via deubiquitinating and stabilizing GSDME. These findings reveal a promising novel direction to investigate radioresistance and suggest potential therapeutic targets for sensitizing NPC to radiotherapy.

SPC25 promotes proliferation and stemness of hepatocellular carcinoma cells via the DNA-PK/AKT/Notch1 signaling pathway.

The imbalance of kinetochore-microtubule attachment during cell mitosis is a response to the initiation and progression of human cancers. Spindle component 25 (SPC25) is indispensable for spindle apparatus organization and chromosome segregation. SPC25 plays an important role in the development of malignant tumors, but its role in hepatocellular carcinoma (HCC) is yet to be determined. In this study, we aimed to preliminarily investigate the role of SPC25 in HCC progression and the molecular mechanisms underlying the process. We identified SPC25 as a clinically notable molecule significantly correlated with the grade of malignancy and poor survival in both The Cancer Genome Atlas (TCGA) cohort and the HCC patient cohort from our center. Mechanistically, SPC25 promoted the incidence of DNA damage and activated the DNA-PK/Akt/Notch1 signaling cascade in HCC cells; the NICD/ RBP-Jκ complex directly targeted SOX2 and NANOG in a transcriptional manner to regulate the proliferation and self-renewal of HCC cells. Our study suggests that HCC-intrinsic SPC25/DNA-PK/Akt/Notch1 signaling is an important mechanism to promote carcinogenesis by regulating the proliferation and stemness program, which provides possible biomarkers for predicting HCC progression and poor survival, as well as potential therapeutic targets for HCC patients.

Validating the prognostic value of Freiburg index of posttransjugular intrahepatic portosystemic shunt survival score and classic scores in Chinese patients with implantation of transjugular intrahepatic portosystemic shunt.

BACKGROUND AND AIMS: It is important and challenging to evaluate the survival of cirrhotic patients undergoing transjugular intrahepatic portosystemic shunt (TIPS). We aimed to validate the Freiburg index of post-TIPS survival (FIPS) score and classic scores for predicting mortality in Chinese patients after TIPS creation. METHODS: A total of 709 consecutive patients with cirrhosis from December 2011 to July 2018 who underwent TIPS placement were retrospectively reviewed. The prognostic value of the FIPS score, the model for end-stage liver disease (MELD) score, Child-Pugh score and Chronic Liver Failure Consortium Acute Decompensation score was validated with the receiver operating characteristic (ROC) curve and DeLong et al. test. RESULTS: The MELD-Na score was superior to the FIPS score in predicting 1-month mortality [AUROC, 0.727 (0.692-0.759) vs. 0.588 (0.551-0.625); P = 0.048]. The MELD and MELD-Na scores were significant superior to the FIPS score in predicting 3-month mortality [AUROC, 0.730 (0.696-0.762) vs. 0.598 (0.561-0.634); P = 0.044 and 0.740 (0.706-0.772) vs. 0.598 (0.561-0.634); P = 0.028]. Subgroup analyses revealed that Child-Pugh score was better than FIPS score in predicting 3-month mortality [AUROC, 0.797 (0.745-0.843) vs. 0.578 (0.517-0.637); P = 0.049] in nonviral cirrhosis group. CONCLUSION: Classic scores still had good risk stratification and predictive ability of post-TIPS mortality. The FIPS score was not superior to the classic scores in the current Chinese cohort. The MELD and MELD-Na scores were significantly superior to the FIPS score in predicting 3-month mortality.

Protective anti-gB neutralizing antibodies targeting two vulnerable sites for EBV-cell membrane fusion.

Epstein-Barr virus (EBV) infects more than 90% of the world's adult population and accounts for a significant cancer burden of epithelial and B cell origins. Glycoprotein B (gB) is the primary fusogen essential for EBV entry into host cells. Here, we isolated two EBV gB-specific neutralizing antibodies, 3A3 and 3A5; both effectively neutralized the dual-tropic EBV infection of B and epithelial cells. In humanized mice, both antibodies showed effective protection from EBV-induced lymphoproliferative disorders. Cryoelectron microscopy analyses identified that 3A3 and 3A5 bind to nonoverlapping sites on domains D-II and D-IV, respectively. Structure-based mutagenesis revealed that 3A3 and 3A5 inhibit membrane fusion through different mechanisms involving the interference with gB-cell interaction and gB activation. Importantly, the 3A3 and 3A5 epitopes are major targets of protective gB-specific neutralizing antibodies elicited by natural EBV infection in humans, providing potential targets for antiviral therapies and vaccines.

Performance and mechanisms exploration of nano zinc oxide (nZnO) on anaerobic decolorization by Shewanella oneidensis MR-1.

Although the ecological safety of nanomaterials is of widespread concern, their current ambient concentrations are not yet sufficient to cause serious toxic effects. Thus, the nontoxic bioimpact of nanomaterials in wastewater treatment has attracted increasing attention. In this study, the effect of nano zinc oxide (nZnO), one of the most widely used nanomaterials, on the anaerobic biodegradation of methyl orange (MO) by Shewanella oneidensis MR-1 was comprehensively investigated. High-dosage nZnO (>0.5 mg/L) caused severe toxic stress on S. oneidensis MR-1, resulting in the decrease in decolorization efficiency. However, nZnO at ambient concentrations could act as nanostimulants and promote the anaerobic removal of MO by S. oneidensis MR-1, which should be attributed to the improvement of decolorization efficiency rather than cell proliferation. The dissolved Zn2+ was found to contribute to the bioeffect of nZnO on MO decolorization. Further investigation revealed that low-dosage nZnO could promote the cell viability, membrane permeability, anaerobic metabolism, as well as related gene expression, indicating that nZnO facilitated rather than inhibited the anaerobic wastewater treatment under ambient conditions. Thus, this work provides a new insight into the bioeffect of nZnO in actual environment and facilitates the practical application of nanomaterials as nanostimulants in biological process.