Geospatial immune heterogeneity reflects the diverse tumor-immune interactions in intrahepatic cholangiocarcinoma

Intrahepatic cholangiocarcinoma (iCCA) exhibits extensive intratumoral heterogeneity and extremely high mortality rate. Here, we performed WES, RNA-seq, TCR-seq and multiplexed immunofluorescence on 207 tumor regions from 45 iCCA patients. Over half of iCCA displayed intratumoral heterogeneity of immune infiltration, and iCCA were classified into sparsely, heterogeneously, and highly infiltrated subgroups with distinct immunogenomic characteristics. Sparsely infiltrated tumors displayed active copy number loss of clonal neoantigens and heterogeneous immune infiltration played an important role in the subclonal evolution across tumor subregions. Highly infiltrated tumors were characterized by extensive immune activation and similar TCR repertoire across tumor subregions, but counteracted with T cell exhaustion and pervasive antigen presentation defects. Notably, FGFR2 mutations and fusions correlated with low mutation burden and reduced immune infiltration. Our work sculpted the dynamic tumor-immune interactions and developed a robust classification system to divide iCCA patients into high and low immune evasion groups with different prognosis.

Abstract 2537: Beta-glucan reprograms immunomodulatory metabolism in human macrophage and ex vivo in lung cancer tissues

We combined multiplex Stable Isotope-Resolved Metabolomics (mSIRM) with Reverse Phase Protein Array (RPPA) to map the time course changes of IM metabolic network and key protein regulators in four human donors’ MΦ’s in response to differential polarization and whole glucan particulates (WGP) treatments. We found consistent and plastic network responses to polarization durations and WGP treatments compared to those of the mouse counterparts. Consistent responses included enhanced 15N2-tryptophan catabolism to quinolinate, 2H2-glucose oxidation to ribose/ribulose-5-phosphate, and conversion of 13C5-glutamine to itaconate in response to pro-inflammatory (M1) versus anti-inflammatory (M2) stimuli. WGP robustly induced the buildup of 2H2-glucose-derived 6-phosphogluconate, -lactate, and -IMP, 13C5-glutamine-derived fructose-1,6-bisphosphate, and increased enrichment of 2H-labeled UDP-N-acetylglucosamine in M2-MΦ’s. However, the Krebs cycle activity was variably enhanced by M2 stimuli or WGP treatment. The consistent effects were related to increased release of proinflammatory IM effectors IL-1β/CXCL10/IFNγ/TNFα by M1-MΦ’s and enhanced release of IL-1β/TNFα to above M1-MΦ’s levels in WGP-treated M2-MΦ’s while boosting the latter in anti-inflammatory IL-10 release and maintenance of NAD+ synthesis. They were also related to lower phagocytosis in M1-MΦ’s and WGP-treated M2-MΦ’s versus M2-MΦ’s. Together with the expression changes of key protein regulators, we suggest enhanced tryptophan catabolism with blocked NAD+ and UTP synthesis to be key to the consistent changes in immune functions in response to M1 stimuli. Likewise, increased glucose utilization via glycolysis and the oxidative branch of the pentose phosphate pathway, and blockade of glutamine-fueled N-linked glycosylation could be linked to reversion of M2 to M1-type immune functions. Reprogrammed Krebs cycle and glutamine conversion to UTP occurred variably in WGP-treated ex vivo organotypic tissue cultures (OTCs) of human non-small cell lung cancer (NSCLC), which could reflect variable M1 repolarization of tumor associated MΦ’s. This in turn correlated with IL-1β/TNFα releases and compromised tumor status, making patient-derived OTCs a unique model for studying variable immunotherapeutic efficacy in cancer patients. In conclusion, consistent and variable IM metabolic responses were evident in four human donors’ MΦ’s. WGP repolarized some M2 to M1-type responses while boosting other M2-type responses. NSCLC OTCs from six patients showed variable M1 repolarization in response to WGP.

Citation Format: Teresa W. M. Fan, Saeed Daneshmandi, Teresa A. Cassel, Mohammad B. Uddin, James Sledziona, Patrick T. Thompson, Penghui Lin, Richard M. Higashi, Andrew N. Lane. Beta-glucan reprograms immunomodulatory metabolism in human macrophage and ex vivo in lung cancer tissues [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 2537.

Abstract 2324: Small-scale microwave-assisted acid hydrolysis method for glycogen determination and turnover in tumors using Stable Isotope Resolved Metabolomics

Introduction: Glycogen is a readily deployed intracellular energy storage macromolecule composed of branched chains of glucose. Although glycogen primarily occurs in the liver and muscle, it can be found in most tissues throughout the body, and its metabolism has been shown to be important in cancers and immune cells. Robust analysis of glycogen turnover requires stable isotope tracing plus a reliable means of quantifying total and labeled glycogen derived from precursors such as 13C6-glucose. Current methods for analyzing glycogen are time- and sample-consuming, at best semi-quantitative, and unable to measure stable isotope enrichment.

Methods: We have developed a microscale method for quantifying both intact and acid-hydrolyzed glycogen by ultra-high-resolution Fourier transform mass spectrometric (UHR-FTMS) and/or NMR analysis in stable isotope resolved metabolomics (SIRM) studies. Polar metabolites, including intact glycogen and their 13C positional isotopomer distributions were first measured in crude biological extracts by high resolution NMR, followed by rapid and efficient acid hydrolysis to glucose in 1 N HCl for 10 minutes at 110 °C under a N2 atmosphere in a microwave-assisted synthesis reactor. The resulting glucose and its 13C isotopologues were then analyzed by UHR-FTMS and/or NMR.

Results: We optimized the microwave digestion time, temperature, and oxygen purging in terms of recovery versus degradation and found 10 minutes at 110-115 °C to give > 90% recovery. The method was applied to track the fate of 13C6-glucose in primary human lung BEAS-2B cells, human macrophages, murine liver and patient-derived tumor xenograft (PDTX) in vivo, and the fate of 2H7-glucose in ex vivo lung organotypic tissue cultures of a lung cancer patient. We showed the incorporation of 13C6-glucose into glycogen and its metabolic intermediates, UDP-Glucose and glucose-1-phosphate, both in terms of the 13C levels and fractional enrichment, thereby demonstrating the utility of the method in tracing glycogen turnover in cells and tissues.

Conclusions: The method offers a quantitative, sensitive, and convenient means to analyze glycogen turnover in mg amounts of complex biological materials.

Keywords: glycogen turnover; 13C6-glucose, stable isotope resolved metabolomics (SIRM); microwave-assisted hydrolysis.

Citation Format: Andrew N. Lane, Timothy L. Scott, Juan Zhu, Teresa A. Cassel, Sara Vicente-Munoz, Penghui Lin, Richard M. Higashi, Teresa W-M Fan. Small-scale microwave-assisted acid hydrolysis method for glycogen determination and turnover in tumors using Stable Isotope Resolved Metabolomics [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 2324.

Who are the real high-risk patients with pathological T2N0M0 non-small-cell lung cancer that can benefit from adjuvant chemotherapy?

Background

Methods

Results

Conclusions

•

ACT could not improve long-term survival in pT2N0M0 NSCLC in general.

•

ACT could only improve OS and DFS in pT2N0M0 NSCLC >4 cm.

•

ACT could not improve CSS in any subgroup of pT2N0M0 NSCLC.

•

For patients with other high-risk factors, ACT failed to improve long-term survival.

TP53-inducible putative long noncoding RNAs encode functional polypeptides that suppress cell proliferation

Polypeptides encoded by long non-coding RNAs (lncRNAs) are a novel class of functional molecules. However, whether these hidden polypeptides participate in the TP53 pathway and play a significant biological role is still unclear. Here, we discover that TP53-regulated lncRNAs encode peptides, two of which are functional in various human cell lines. Using ribosome profiling and RNA-seq approaches in HepG2 cells, we systematically identified more than 300 novel TP53-regulated lncRNAs and further confirmed that fifteen of these TP53-regulated lncRNAs encode peptides. Furthermore, several peptides were validated by multiple mass spectrometry measures. Ten of the novel translational lncRNAs were directly inducible by TP53 in response to DNA damage. Notably, we showed that the TP53-inducible peptides TP53LC02 and TP53LC04, but not their lncRNAs, could suppress cell proliferation. TP53LC04 peptide also had a function associated with cell proliferation by regulating the cell cycle in response to DNA damage. This study demonstrates that TP53-inducible lncRNAs encode new functional peptides, leading to the enlargement of the components of TP53 tumor suppressor network and providing novel potential targets for cancer therapy.

"Watch Me Grow- Electronic (WMG-E)" surveillance approach to identify and address child development, parental mental health, and psychosocial needs: study protocol

Background

The COVID-19 pandemic and the associated economic recession has increased parental psychosocial stress and mental health challenges. This has adversely impacted child development and wellbeing, particularly for children from priority populations (culturally and linguistically diverse (CALD) and rural/regional communities) who are at an already increased risk of health inequality. The increased mental health and psychosocial needs were compounded by the closure of in-person preventive and health promotion programs resulting in health organisations embracing technology and online services. Watch Me Grow- Electronic (WMG-E) – developmental surveillance platform- exemplifies one such service.

WMG-E was developed to monitor child development and guide parents towards more detailed assessments when risk is identified. This Randomised Controlled Trial (RCT) aims to expand WMG-E as a digital navigation tool by also incorporating parents’ mental health and psychosocial needs. Children and families needing additional assessments and supports will be electronically directed to relevant resources in the ‘care-as-usual’ group. In contrast, the intervention group will receive continuity of care, with additional in-person assessment and ‘warm hand over’ by a ‘service navigator’ to ensure their needs are met.

Methods

Using an RCT we will determine: (1) parental engagement with developmental surveillance; (2) access to services for those with mental health and social care needs; and (3) uptake of service recommendations. Three hundred parents/carers of children aged 6 months to 3 years (recruited from a culturally diverse, or rural/regional site) will be randomly allocated to the ‘care-as-usual’ or ‘intervention’ group. A mixed methods implementation evaluation will be completed, with semi-structured interviews to ascertain the acceptability, feasibility and impact of the WMG-E platform and service navigator.

Conclusions

Using WMG-E is expected to: normalise and de-stigmatise mental health and psychosocial screening; increase parental engagement and service use; and result in the early identification and management of child developmental needs, parental mental health, and family psychosocial needs. If effective, digital solutions such as WMG-E to engage and empower parents alongside a service navigator for vulnerable families needing additional support, will have significant practice and policy implications in the pandemic/post pandemic period.

Trial registration

The trial (Protocol No. 1.0, Version 3.1) was registered with ANZCTR (registration number: ACTRN12621000766819) on July 21st, 2021 and reporting of the trial results will be according to recommendations in the CONSORT Statement.

[To promote AIDS preventive health education in schools]

In recent years, the annual number of newly reported HIV/AIDS cases in young students remained to be 3 000 approximately, which has arisen a serious social concern. This paper focuses on the analysis on the epidemic characteristics of AIDS in young students in China and the weak points in preventive health education, and puts forward some thoughts on promoting the preventive health education in schools and introduces a WeChat applet for sexual health and HIV infection risk assessment in young students, which is called "Detective Bear" and developed based on self-categorization theory in Guangzhou to help young students to be aware of their own risks and specific problems and provide individualized intervention for the better implementation of AIDS prevention health education in schools in China in the new era.

Differentiating infected focal liver lesions from malignant mimickers: value of ultrasound-based radiomics

AIM

To establish an ultrasound-based radiomics model through machine learning methods and then to assess the ability of the model to differentiate infected focal liver lesions from malignant mimickers.

MATERIALS AND METHODS

A total of 104 patients with infected focal liver lesions and 485 patients with malignant hepatic tumours were included, consisting of hepatocellular carcinoma (HCC), cholangiocarcinoma (CC), combined hepatocellular-cholangiocarcinoma (cHCC-CC), and liver metastasis. Radiomics features were extracted from grey-scale ultrasound images. Feature selection and predictive modelling were carried out by dimensionality reduction methods and classifiers. The diagnostic effect of the prediction mode was assessed by receiver operating characteristic (ROC) curve analysis.

RESULTS

In total, 5,234 radiomics features were extracted from grey-scale ultrasound image of every focal liver lesion. The ultrasound-based radiomics model had a favourable predictive value for differentiating infected focal liver lesions from malignant hepatic tumours, with an area under the curve (AUC) of 0.887 and 0.836 (HCC group), 0.896 and 0.766 (CC group), 0.944 and 0.754 (cHCC-CC group), 0.918 and 0.808 (liver metastasis group), and 0.949 and 0.745 (malignant hepatic tumour group) for the training set and validation set, respectively.

CONCLUSIONS

Ultrasound-based radiomics is helpful in differentiating infected focal liver lesions from malignant mimickers and has the potential for use as a supplement to conventional grey-scale ultrasound and contrast-enhanced ultrasound (CEUS).

Endoscopic sinus surgery improves Eustachian tube function in patients with chronic rhinosinusitis: a multicenter prospective study

BACKGROUND

Patients with chronic rhinosinusitis (CRS) often have Eustachian tube dysfunction (ETD) symptoms. This study aimed to prospectively investigate the effect of endoscopic sinus surgery (ESS) on improvement of Eustachian tube function in CRS patients with ETD from a Chinese population and determine factors associated with improvement.

METHODS

A prospective study was performed in CRS patients with ETD who underwent ESS from 3 tertiary medical centers in south China. The Eustachian tube Dysfunction Questionnaire 7 (ETDQ-7), Sinonasal Outcome Test 22 (SNOT-22), tympanograms, endoscopic findings and Valsalva maneuver were recorded and analyzed preoperatively and postoperatively at 8-12 weeks.

RESULTS

A total of 70 CRS patients with ETD were included in this study. The ETDQ-7 score and the ability of positive Valsalva maneuver in CRS patients were significantly improved postoperatively at 8-12 weeks. The number of patients with type A tympanogram was increased postoperatively. Reduced Eustachian tube mucosal inflammation was also observed postoperatively. In addition, ESS appeared to reverse slight tympanic membrane atelectasis after 8-12 weeks. Moreover, improvement in tympanogram was presented in more than half of CRS patients with concomitant otitis media with effusion postoperatively at 8-12 weeks. Univariate and multivariate analysis revealed failure of normalization of ETDQ-7 postoperatively was associated with concomitant allergic rhinitis and higher preoperative SNOT-22 score.

CONCLUSIONS

This study confirms Eustachian tube function is often improved after ESS in CRS patients with ETD. Concomitant allergic rhinitis and higher preoperative SNOT-22 score are associated with failure of normalization of ETD symptoms.

Mid-treatment Fluorodeoxyglucose Positron Emission Tomography in Human Papillomavirus-related Oropharyngeal Squamous Cell Carcinoma Treated with Primary Radiotherapy: Nodal Metabolic Response Rate can Predict Treatment Outcomes

AIMS

To evaluate whether biomarkers derived from fluorodeoxyglucose positron emission tomography-computed tomography (FDG PET-CT) performed prior to (prePET) and during the third week (interim PET; iPET) of radiotherapy can predict treatment outcomes in human papillomavirus (HPV)-positive oropharyngeal squamous cell carcinoma (OPC).

MATERIALS AND METHODS

This retrospective analysis included 46 patients with newly diagnosed OPC treated with definitive (chemo)radiation and all patients had confirmed positive HPV status (HPV+OPC) based on p16 immunohistochemistry. The maximum standardised uptake value (SUV_max), metabolic tumour volume (MTV) and total lesional glycolysis (TLG) of primary, index node (node with the highest TLG) and total lymph nodes and their median percentage (≥50%) reductions in iPET were analysed, and correlated with 5-year Kaplan-Meier and multivariable analyses (smoking, T4, N2b-3 and AJCC stage IV), including local failure-free survival, regional failure-free survival, locoregional failure-free survival (LRFFS), distant metastatic failure-free survival (DMFFS), disease-free survival (DFS) and overall survival.

RESULTS

There was no association of outcomes with prePET parameters observed on multivariate analysis. A complete metabolic response of primary tumour was seen in 13 patients; the negative predictive value for local failure was 100%. More than a 50% reduction in total nodal MTV provided the best predictor of outcomes, including LRFFS (88% versus 47.1%, P = 0.006, hazard ratio = 0.153) and DFS (78.2% versus 41.2%, P = 0.01, hazard ratio = 0.234). More than a 50% reduction in index node TLG was inversely related to DMFFS: a better nodal response was associated with a higher incidence of distant metastatic failure (66.7% versus 100%, P = 0.009, hazard ratio = 3.0).

CONCLUSION

The reduction (≥50%) of volumetric nodal metabolic burden can potentially identify a subgroup of HPV+OPC patients at low risk of locoregional failure but inversely at higher risk of distant metastatic failure and may have a role in individualised adaptive radiotherapy and systemic therapy.

NMR Analysis of Carboxylate Isotopomers of 13C-Metabolites by Chemoselective Derivatization with 15N-Cholamine

A substantial fraction of common metabolites contains carboxyl functional groups. Their ¹³C isotopomer analysis by nuclear magnetic resonance (NMR) is hampered by the low sensitivity of the ¹³C nucleus, the slow longitudinal relaxation for the lack of an attached proton, and the relatively low chemical shift dispersion of carboxylates. Chemoselective (CS) derivatization is a means of tagging compounds in a complex mixture via a specific functional group. ¹⁵N₁-cholamine has been shown to be a useful CS agent for carboxylates, producing a peptide bond that can be detected via ¹⁵N-attached H with high sensitivity in heteronuclear single quantum coherence experiments. Here, we report an improved method of derivatization and show how ¹³C-enrichment at the carboxylate and/or the adjacent carbon can be determined via one- and two-bond coupling of the carbons adjacent to the cholamine ¹⁵N atom in the derivatives. We have applied this method for the determination of ¹³C isotopomer distribution in the extracts of A549 cell culture and liver tissue from a patient-derived xenograft mouse.

NMR Methods for Determining Lipid Turnover via Stable Isotope Resolved Metabolomics

Lipids comprise diverse classes of compounds that are important for the structure and properties of membranes, as high-energy fuel sources and as signaling molecules. Therefore, the turnover rates of these varied classes of lipids are fundamental to cellular function. However, their enormous chemical diversity and dynamic range in cells makes detailed analysis very complex. Furthermore, although stable isotope tracers enable the determination of synthesis and degradation of complex lipids, the numbers of distinguishable molecules increase enormously, which exacerbates the problem. Although LC-MS-MS (Liquid Chromatography-Tandem Mass Spectrometry) is the standard for lipidomics, NMR can add value in global lipid analysis and isotopomer distributions of intact lipids. Here, we describe new developments in NMR analysis for assessing global lipid content and isotopic enrichment of mixtures of complex lipids for two cell lines (PC3 and UMUC3) using both 13C6 glucose and 13C5 glutamine tracers.

[Effects of vestibular spontaneous nystagmus on visual smooth pursuit function]

Objective: The aim of the study is to analyze the effects of vestibular spontaneous nystagmus(SN) on the smooth pursuit function of visual ocularmotor system. Methods: A total of 46 patients with acute unilateral peripheral vestibular syndrome with SN (26 cases of vestibular neuritis, 6 cases of Ramsay Hunt Syndrome (RHS) with vertigo, 14 cases of sudden deafness with vertigo) were included in this work. In the study group, the results of SPT and SN test with videonystagmography(VNG) were also reviewed. Taking SPT parameters, the influence of SN intensity on SPT gain, asymmetry and waveform and their correlation were analyzed.SPSS19.0 software was used for statistical analysis. Results: Among the 46 patients, there were 36 cases of SN pointing to the healthy side(SN intensity range of 2.68°/s-32.53°/s), and 10 cases of SN pointing to the affected side (SN intensity range of 2.66°/s-16.54°/s). SN intensity was divided into 3 groups, including light(0.50°/s-5.00°/s), medium(5.01°/s-10.00°/s) and strong(>10.01°/s), accounting for 14 cases(30.4%), 18 cases(39.1%) and 14 cases(30.4%), respectively. The differences of the gain of SPT to the fast phase and slow phase direction in the overall groups and light, medium and strong groups of SN intensity respectively were statistically significant(t_total=13.338, t_light=6.184, t_medium=8.436, t_strong=8.477, all of P<0.001). The difference of SPT gain in SN fast phase direction between groups with different SN intensity was statistically significant(F=9.639, P<0.001),there was no statistically significant difference in SPT gain between the groups on the SN slow phase direction(F=1.137, P=0.330).The SN intensity significantly negatively correlated with the SPT gain of the fast phase direction of SN (r=-0.433, P=0.003), that was, the SPT gain on the fast phase direction of SN decreased with the increase of SN intensity. There was no significant correlation between SN intensity and the gain of SPT on the slow phase direction of SN (r=-0.061, P=0.687). SPT waveform analysis showed that type I, type II and type III accounted for 8 cases(17.4%), 21 cases(45.6%) and 17 cases(37.0%), respectively. The corresponding mean values of SN intensity were (3.71±0.69)°/s, (7.44±1.88)°/s, (20.04±5.53)°/s, respectively, without type IV wave. The intensity of SN was positively correlated with the asymmetric value of the gain of SPT left and right(r=0.450,P=0.002). That was, with the increase of SN strength, the asymmetric value also increased, and the worse the asymmetry of the gain of SPT left and right pursuit was, the worse the SPT waveform was. Conclusion: SPT gain, asymmetry and SPT waveforms are all affected by SN, and the greater the intensity of SN, the greater the influence on the three. When SN is strong, type III waves may occur, suggesting that acute peripheral vestibular syndrome can also affect the visual ocularmotor systems.

Blockade of 6-phosphogluconate dehydrogenase generates CD8+ effector T cells with enhanced anti-tumor function

Although T cell expansion depends on glycolysis, T effector cell differentiation requires signaling via the production of reactive oxygen species (ROS). Because the pentose phosphate pathway (PPP) regulates ROS by generating nicotinamide adenine dinucleotide phosphate (NADPH), we examined how PPP blockade affects T cell differentiation and function. Here, we show that genetic ablation or pharmacologic inhibition of the PPP enzyme 6-phosphogluconate dehydrogenase (6PGD) in the oxidative PPP results in the generation of superior CD8+ T effector cells. These cells have gene signatures and immunogenic markers of effector phenotype and show potent anti-tumor functions both in vitro and in vivo. In these cells, metabolic reprogramming occurs along with increased mitochondrial ROS and activated antioxidation machinery to balance ROS production against oxidative damage. Our findings reveal a role of 6PGD as a checkpoint for T cell effector differentiation/survival and evidence for 6PGD as an attractive metabolic target to improve tumor immunotherapy.

Apolipoprotein E genotype-dependent nutrigenetic effects to prebiotic inulin for modulating systemic metabolism and neuroprotection in mice via gut-brain axis

OBJECTIVE

The goal of the study was to identify the potential nutrigenetic effects to inulin, a prebiotic fiber, in mice with different human apolipoprotein E (APOE) genetic variants. Specifically, we compared responses to inulin for the potential modulation of the systemic metabolism and neuroprotection via gut-brain axis in mice with human APOE ϵ3 and ϵ4 alleles.

METHOD

We performed experiments with young mice expressing the human APOE3 (E3FAD mice and APOE4 gene (E4FAD mice). We fed mice with either inulin or control diet for 16 weeks starting from 3 months of age. We determined gut microbiome diversity and composition using16s rRNA sequencing, systemic metabolism using in vivo MRI and metabolomics, and blood-brain barrier (BBB) tight junction expression using Western blot.

RESULTS

In both E3FAD and E4FAD mice, inulin altered the alpha and beta diversity of the gut microbiome, increased beneficial taxa of bacteria and elevated cecal short chain fatty acid and hippocampal scyllo-inositol. E3FAD mice had altered metabolism related to tryptophan and tyrosine, while E4FAD mice had changes in the tricarboxylic acid cycle, pentose phosphate pathway, and bile acids. Differences were found in levels of brain metabolites related to oxidative stress, and levels of Claudin-1 and Claudin-5 BBB tight junction expression.

DISCUSSION

We found that inulin had many similar beneficial effects in the gut and brain for both E3FAD and E4FAD mice, which may be protective for brain functions and reduce risk for neurodegeneration. . E3FAD and E4FAD mice also had distinct responses in several metabolic pathways, suggesting an APOE-dependent nutrigenetic effects in modulating systemic metabolism and neuroprotection.

Solvent-cast 3D printing of magnesium scaffolds

Biodegradable porous magnesium (Mg) scaffolds are promising for application in the regeneration of critical-sized bone defects. Although additive manufacturing (AM) carries the promise of offering unique opportunities to fabricate porous Mg scaffolds, current attempts to apply the AM approach to fabricating Mg scaffolds have encountered some crucial issues, such as those related to safety in operation and to the difficulties in composition control. In this paper, we present a room-temperature extrusion-based AM method for the fabrication of topologically ordered porous Mg scaffolds. It is composed of three steps, namely (i) preparing a Mg powder loaded ink with desired rheological properties, (ii) solvent-cast 3D printing (SC-3DP) of the ink to form scaffolds with 0 °/ 90 °/ 0 ° layers, and (iii) debinding and sintering to remove the binder in the ink and then get Mg powder particles bonded by applying a liquid-phase sintering strategy. A rheological analysis of the prepared inks with 54, 58 and 62  vol% Mg powder loading was performed to reveal their viscoelastic properties. Thermal-gravimetric analysis (TGA), Fourier transform infrared spectroscopy (FTIR), carbon/sulfur analysis and scanning electron microscopy (SEM) indicated the possibilities of debinding and sintering at one single step for fabricating pure Mg scaffolds with high fidelity and densification. The resulting scaffolds with high porosity contained hierarchical and interconnected pores. This study, for the first time, demonstrated that the SC-3DP technique presents unprecedented possibilities to fabricate Mg-based porous scaffolds that have the potential to be used as a bone-substituting material. STATEMENT OF SIGNIFICANCE: Biodegradable porous magnesium scaffolds are promising for application in the regeneration of critical-sized bone defects. Although additive manufacturing (AM) carries the promise of offering unique opportunities to fabricate porous magnesium scaffolds, current attempts to apply the AM approach to fabricating magnesium scaffolds still have some crucial limitations. This study demonstrated that the solvent-cast 3D printing technique presents unprecedented possibilities to fabricate Mg-based porous scaffolds. The judicious chosen of formulated binder system allowed for the negligible binder residue after debinding and the short-time liquid-phase sintering strategy led to a great success in sintering pure magnesium scaffolds. The resulting scaffolds with hierarchical and interconnected pores have great potential to be used as a bone-substituting material.