ObjectiveThis paper aims to investigate the efficacy and related actions of Guizhi Fulingwan in intervening in the mice with colitis-associated colon cancer （CAC） based on the immunosuppressive microenvironment associated with myeloid-derived suppressor cells （MDSCs）. MethodsSixty male C57BL/6 mice were randomly assigned to a blank group， a model group， an aspirin group （0.04 g·kg^-1）， and low-， medium-， and high-dose Guizhi Fulingwan groups （4.87， 9.75， and 19.50 g·kg^-1）， with ten mice per group. The CAC mouse model was established via combined induction of azoxymethane （AOM）/dextran sulphate sodium （DSS）. Drug intervention commenced in week five， with continuous intragastric administration for nine weeks. The food intake， body weight， fecal characteristics， and haematochezia were observed and recorded， and disease activity index （DAI） scores were calculated according to scoring criteria. Hematoxylin and eosin （HE） staining was used to observe the histopathological changes in the colon tissues of the mice. Immunohistochemistry was used to determine proliferating cell nuclear antigen-67 （Ki67） expression in the colon tissues， and enzyme-linked immunosorbent assay （ELISA） was used to detect the contents of interleukin-6 （IL-6）， IL-1β， and tumor necrosis factor-α （TNF-α） in the serum of the mice. Flow cytometry was employed to determine the proportion levels of MDSCs， CD4⁺ T cells， and CD8⁺ T cells in the spleen tissues of the mice. The mRNA expressions of MDSC-associated effector molecules， including arginase 1 （Arg1） and inducible nitric oxide synthase （iNOS）， were detected by real-time quantitative polymerase chain reaction （Real-time PCR）. After that， an in vitro co-culture model of MDSCs and CD8⁺ T cells was established， and drug-containing serum of Guizhi Fulingwan was used for intervention. The Flow cytometry was employed to assess the effects of drug-containing serum of Guizhi Fulingwan with different concentrations on the levels of reactive oxygen species （ROS） and iNOS in MDSCs and the proliferation of CD8⁺ T cells. The levels of granzyme B （GZMB） and interferon-γ （IFN-γ） in cell supernatant were detected by ELISA. ResultsCompared with those in the control group， the mice in the model group exhibited significantly reduced body weight， elevated DAI scores， shortened colon length （P<0.01）， increased number of tumors and Ki67 expression （P<0.01）， and significantly elevated contents of IL-6， IL-1β， and TNF-α in the serum （P<0.01）. Significant increases in the number of MDSCs were observed in mouse spleens， alongside marked reductions in the levels of CD4⁺ T and CD8⁺ T cells （P<0.01）. Furthermore， the mRNA expressions of MDSC function-associated effector molecules Arg1 and iNOS were significantly upregulated （P<0.01）. Compared with those in the model group， the mice in the middle-dose Guizhi Fulingwan group exhibited increased body weight and significantly decreased DAI scores （P<0.05， P<0.01）. The mice in the middle- and high-dose Guizhi Fulingwan groups exhibited significantly improved colon shortening， significantly decreased number of tumors and Ki67 expression （P<0.05， P<0.01）， and significantly decreased contents of IL-6， IL-1β， and TNF-α in the serum （P<0.05， P<0.01）. Furthermore， administration of Guizhi Fulingwan markedly reduced MDSC infiltration in the spleen of the mice， with different degrees of increase in the levels of both CD4⁺ T and CD8⁺ T cells （P<0.05， P<0.01）， alongside significant decreases in the mRNA expressions of Arg1 and iNOS （P<0.05， P<0.01）. In vitro cell co-culture shows that administration of drug-containing serum of Guizhi Fulingwan significantly decreases the activity levels of ROS and iNOS in MDSCs and promotes the proliferation of CD8⁺ T cells and the secretion of GZMB and IFN-γ （P<0.05， P<0.01）. ConclusionGuizhi Fulingwan can reduce pro-inflammatory cytokine secretion and inhibit tumor proliferation in the colon tissues of CAC mice. Its potential mechanism may involve reducing MDSC infiltration， enhancing effector T cells， particularly CD8⁺ T cell response， and improving the tumor immunosuppressive microenvironment.

BACKGROUND:Bone remodeling is the biological basis of orthodontic tooth movement.Type 2 diabetes mellitus leads to metabolic changes in the jaw and alveolar bone,so it is hypothesized that tooth mobility characteristics may be altered in a high-sugar environment.OBJECTIVE:To explore the impact of type 2 diabetes mellitus on orthodontic tooth movement in rats within one tooth movement cycle.METHODS:Seventy-two Sprague-Dawley rats were selected.Forty rats were randomly chosen and fed with a high-fat diet to construct a type 2 diabetes mellitus model.Thirty-two rats that were successfully modeled were randomly divided into a type 2 diabetes mellitus group(n=16)and a diabetic orthodontic group(n=16).The remaining 32 rats were randomly divided into a control group(n=16)and an orthodontic group(n=16).The rats in the orthodontic group and the diabetic orthodontic group were equipped with nickel-titanium coil spring orthodontic force application devices to move the unilateral maxillary first molars mesially with a force of 50 g.The rats were anesthetized and sacrificed on the 3rd,7th,14th,and 21st days after orthodontic treatment,and Micro-CT was used to measure the mesial displacement of the first molars and detect the changes in the bone microstructure parameters on the tension side.RESULTS AND CONCLUSION:There were significant differences in the tooth movement distances among the four groups of rats on the 3rd,7th,14th,and 21st days of orthodontic treatment(P＜0.05).There were significant differences in bone mineral density,bone volume fraction and trabecular bone separation on the tension side among the four groups on the 7th,14th,and 21st days of orthodontic treatment(P＜0.05).There were differences in the trabecular thickness among the four groups on the 3rd and 14th days of orthodontic treatment(P＜0.05).The diabetic orthodontic group had the smallest tension-side alveolar bone mineral density,bone volume fraction,and trabecular thickness,and the largest tooth movement distance and trabecular separation on the 21st day of orthodontic treatment.The above results indicate that type 2 diabetes mellitus adversely affects bone microstructural parameters on the tension side in orthodontic tooth movement in rats,suggesting the occurrence of an osteoporotic state.

BACKGROUND:Bone remodeling is the biological basis of orthodontic tooth movement.Type 2 diabetes mellitus leads to metabolic changes in the jaw and alveolar bone,so it is hypothesized that tooth mobility characteristics may be altered in a high-sugar environment.OBJECTIVE:To explore the impact of type 2 diabetes mellitus on orthodontic tooth movement in rats within one tooth movement cycle.METHODS:Seventy-two Sprague-Dawley rats were selected.Forty rats were randomly chosen and fed with a high-fat diet to construct a type 2 diabetes mellitus model.Thirty-two rats that were successfully modeled were randomly divided into a type 2 diabetes mellitus group(n=16)and a diabetic orthodontic group(n=16).The remaining 32 rats were randomly divided into a control group(n=16)and an orthodontic group(n=16).The rats in the orthodontic group and the diabetic orthodontic group were equipped with nickel-titanium coil spring orthodontic force application devices to move the unilateral maxillary first molars mesially with a force of 50 g.The rats were anesthetized and sacrificed on the 3rd,7th,14th,and 21st days after orthodontic treatment,and Micro-CT was used to measure the mesial displacement of the first molars and detect the changes in the bone microstructure parameters on the tension side.RESULTS AND CONCLUSION:There were significant differences in the tooth movement distances among the four groups of rats on the 3rd,7th,14th,and 21st days of orthodontic treatment(P＜0.05).There were significant differences in bone mineral density,bone volume fraction and trabecular bone separation on the tension side among the four groups on the 7th,14th,and 21st days of orthodontic treatment(P＜0.05).There were differences in the trabecular thickness among the four groups on the 3rd and 14th days of orthodontic treatment(P＜0.05).The diabetic orthodontic group had the smallest tension-side alveolar bone mineral density,bone volume fraction,and trabecular thickness,and the largest tooth movement distance and trabecular separation on the 21st day of orthodontic treatment.The above results indicate that type 2 diabetes mellitus adversely affects bone microstructural parameters on the tension side in orthodontic tooth movement in rats,suggesting the occurrence of an osteoporotic state.

ObjectiveTo explore the mechanism by which Qifu Lizhong decoction restores intestinal mucosal barrier function in ulcerative colitis （UC） by regulating the myosin light chain kinase （MLCK）/phosphorylated myosin light chain （p-MLC） signaling pathway. MethodsA rat model of UC with spleen-kidney Yang deficiency syndrome and an in vitro intestinal barrier injury model were established. In vivo experiments were conducted to evaluate the body weight， disease activity index （DAI） scores， and changes in colonic pathological morphology in each group of rats. Enzyme-linked immunosorbent assay （ELISA） was used to measure the levels of tumor necrosis factor-α （TNF-α）， interleukin-1β （IL-1β）， and myeloperoxidase （MPO）. Transmission electron microscopy （TEM） was employed to observe the morphology and structure of tight junctions （TJ） in rat colonic epithelium. In vitro experiments were conducted to observe the morphology of F-actin in human colon adenocarcinoma cell line-2（Caco-2） cells by phalloidin staining. Combining both in vivo and in vitro approaches， immunohistochemistry （IHC）， immunofluorescence （IF）， and Western blot were applied to detect the expression and phosphorylation levels of TJ proteins ［zonula occludens-1 （ZO-1）， Occludin， Claudin-1］ as well as key proteins in the MLCK/p-MLC signaling pathway. ResultsIn vivo experiments demonstrated that， compared with the normal group， the model group exhibited significant body weight loss， elevated DAI scores and histopathological scores （P<0.01）， increased colonic TNF-α， IL-1β， and MPO levels （P<0.01）. TJ structures were disrupted， and the expression of ZO-1， Occludin， and Claudin-1 was significantly reduced （P<0.05， P<0.01）. The protein expression levels of myosin light chain （MLC）， MLCK， phosphorylated （p）-MLC， and p-MLCK significantly increased （P<0.01）. Compared with the model group， all Qifu Lizhong decoction dose groups exhibited increased body weight， as well as significantly decreased DAI scores and histopathological scores （P<0.05， P<0.01）. The colonic levels of MPO， TNF-α， and IL-1β were significantly reduced （P<0.05， P<0.01）. In the Qifu Lizhong decoction + inhibitor group， the expression of TJ proteins ZO-1， Occludin， and Claudin-1 significantly increased （P<0.01）， while the protein expression levels of MLC， MLCK， p-MLC， and p-MLCK were significantly reduced （P<0.01）. In vitro experiment results showed that， compared with the normal group， the TNF-α group exhibited disordered cytoskeletal architecture， weakened fluorescence signals of ZO-1， Occludin， and Claudin-1， and significantly elevated protein expression levels of MLC， MLCK， p-MLC， and p-MLCK （P<0.01）. Compared with the TNF-α group， the Qifu Lizhong decoction + inhibitor group restored the ordered arrangement of the F-actin cytoskeleton， normalized the expression and localization of TJ proteins ZO-1， Occludin， and Claudin-1， and significantly decreased the protein expression levels of MLC， MLCK， p-MLC， and p-MLCK （P<0.01）. ConclusionQifu Lizhong decoction may exert its therapeutic effects on UC by inhibiting the MLCK/p-MLC signaling pathway， thereby stabilizing TJ structure and repairing intestinal barrier integrity.

Objective·To investigate the changes in transcriptome and chromatin accessibility during the differentiation of human embryonic stem cells(hESCs)into neural progenitor cells(NPCs)using in vitro differentiation models and high-throughput multi-omics sequencing technologies.Methods·hESCs were first induced to differentiate into NPCs in vitro using the embryoid body formation method,and cells at both stages were collected.The cell phenotypes were identified by reverse transcription-quantitative real-time PCR(RT-qPCR)and immunofluorescence(IF)staining.Transcriptome sequencing(RNA-seq)was conducted to detect and analyze the differentially expressed genes(DEGs)between hESCs and NPCs.The assay for transposase-accessible chromatin with high-throughput sequencing(ATAC-seq)was employed to assess chromatin accessibility changes between hESCs and NPCs.Motif enrichment analysis was performed on differentially accessible chromatin regions to discover potential regulatory transcription factors.Finally,an integrated analysis of RNA-seq and ATAC-seq data and the protein-protein interaction(PPI)network were performed to identify key genes and regulatory pathways involved in the early stages of neural differentiation in vitro.Results·Both RT-qPCR and IF results indicated that the expression levels of pluripotency markers(NANOG and POU5F1)were high at the hESC stage but significantly decreased at the NPC stage,while early neural differentiation markers(PAX6,SOX1,and NES)were minimally expressed at the hESC stage but markedly upregulated at the NPC stage.RNA-seq analysis revealed that compared to the hESC stage,there were 5 597 genes upregulated and 3 654 genes downregulated at the NPC stage.Gene function enrichment analysis showed that the upregulated genes at the NPC stage were enriched in the functions related to neural development.ATAC-seq analysis demonstrated a total of 27 491 genomic regions had significant changes in chromatin accessibility during the differentiation from hESC to NPC,with 12 381 regions showing increased accessibility and 15 110 regions showing decreased accessibility.Motif enrichment analysis revealed that transcription factor genes such as DLX1 and LHX2 might play an important role in the differentiation process from hESCs into NPCs.Integrated analysis of RNA-seq and ATAC-seq data revealed that overlapping genes with high expression at the NPC stage were mainly enriched in axon guidance,forebrain development,and neuron migration.After neural differentiation,the expression levels of CTNND2 and LHX2 genes increased,and the chromatin accessibility of related genomic regions also increased.PPI network analysis indentified candidate downstream genes including PRKACA,CDH2,and ERBB4.Conclusion·The in vitro differentiation model of hESCs combined with high-throughput multi-omics sequencing technologies can be used to depict the changes in transcriptome and chromatin accessibility during the differentiation of hESCs into NPCs.In this process,the expression levels of genes related to axon guidance,forebrain development,and neuronal migration pathways increase and related chromatin accessibility is enhanced.

Objective·To investigate the changes in transcriptome and chromatin accessibility during the differentiation of human embryonic stem cells(hESCs)into neural progenitor cells(NPCs)using in vitro differentiation models and high-throughput multi-omics sequencing technologies.Methods·hESCs were first induced to differentiate into NPCs in vitro using the embryoid body formation method,and cells at both stages were collected.The cell phenotypes were identified by reverse transcription-quantitative real-time PCR(RT-qPCR)and immunofluorescence(IF)staining.Transcriptome sequencing(RNA-seq)was conducted to detect and analyze the differentially expressed genes(DEGs)between hESCs and NPCs.The assay for transposase-accessible chromatin with high-throughput sequencing(ATAC-seq)was employed to assess chromatin accessibility changes between hESCs and NPCs.Motif enrichment analysis was performed on differentially accessible chromatin regions to discover potential regulatory transcription factors.Finally,an integrated analysis of RNA-seq and ATAC-seq data and the protein-protein interaction(PPI)network were performed to identify key genes and regulatory pathways involved in the early stages of neural differentiation in vitro.Results·Both RT-qPCR and IF results indicated that the expression levels of pluripotency markers(NANOG and POU5F1)were high at the hESC stage but significantly decreased at the NPC stage,while early neural differentiation markers(PAX6,SOX1,and NES)were minimally expressed at the hESC stage but markedly upregulated at the NPC stage.RNA-seq analysis revealed that compared to the hESC stage,there were 5 597 genes upregulated and 3 654 genes downregulated at the NPC stage.Gene function enrichment analysis showed that the upregulated genes at the NPC stage were enriched in the functions related to neural development.ATAC-seq analysis demonstrated a total of 27 491 genomic regions had significant changes in chromatin accessibility during the differentiation from hESC to NPC,with 12 381 regions showing increased accessibility and 15 110 regions showing decreased accessibility.Motif enrichment analysis revealed that transcription factor genes such as DLX1 and LHX2 might play an important role in the differentiation process from hESCs into NPCs.Integrated analysis of RNA-seq and ATAC-seq data revealed that overlapping genes with high expression at the NPC stage were mainly enriched in axon guidance,forebrain development,and neuron migration.After neural differentiation,the expression levels of CTNND2 and LHX2 genes increased,and the chromatin accessibility of related genomic regions also increased.PPI network analysis indentified candidate downstream genes including PRKACA,CDH2,and ERBB4.Conclusion·The in vitro differentiation model of hESCs combined with high-throughput multi-omics sequencing technologies can be used to depict the changes in transcriptome and chromatin accessibility during the differentiation of hESCs into NPCs.In this process,the expression levels of genes related to axon guidance,forebrain development,and neuronal migration pathways increase and related chromatin accessibility is enhanced.

Objective To compare the efficacy of recombinant human interleukin-11(rhIL-11)and herombopag olamine tablets on chemotherapy-induced thrombocytopenia(CIT)in breast cancer.Methods Eighty-six prospectively selected breast cancer patients with CIT were randomly divided into the control group(administered rhIL-11)and the study group(administered herombopag olamine tablets),with 43 cases in each group.Before treatment and 14 days after treatment,platelet parameters[platelet count(PLT),plateletcrit(PCT),platelet distribution width(PDW)and mean platelet volume(MPV)]and flow cytometry were measured by automated hematology analyzer.Cellular immune indicators(CD3+,CD4+,CD8+and CD4+/CD8+)were detected by flow cytometer.Enzyme-linked immunosorbent assay was used to determine the levels of thrombopoietin(TPO)and interleukin-11(IL-11).The above parameters were compared between the two groups,and the incidence of adverse reactions in the two groups was recorded.Results After treatment,PLT,PCT,CD3+,CD4+,CD4+/CD8+,TPO and IL-11 in both groups were higher than before treatment,and which was higher in the study group than the control group(P＜0.05).After treatment,PDW,MPV and CD8+of both groups were lower than before treatment,and the study group was lower than the control group(P＜0.05).There was no significant difference in the overall incidence of adverse reactions between the two groups(P＞0.05).Conclusion Both rhIL-11 and herombopag olamine tablets are effective in treating breast cancer with CIT.Compared with rhIL-11,herombopag olamine tablets have more advantages in improving platelet parameters,cellular immune indicators,TPO and IL-11,and do not increase the adverse reactions.

Objective To investigate changes and clinical significance of serum cytokine signaling inhibitor-1(SOCS-1),soluble myeloid triggering receptor-2(sTREM-2)and ATP citrate lyase(ACLY)in patients with pulmonary Klebsiella pneumoniae infection.Methods A total of 100 patients infected with Klebsiella pneumoniae were selected as the infection group,and 70 healthy subjects in our hospital were selected as the control group.According to the pneumonia severity index(PSI)score,patients of the infection group were divided into the severe group(PSI>90,32 cases)and the mild group(PSI≤90,68 cases).The expression levels of SOCS-1,sTREM-2 and ACLY in the infection group and the control group were detected by enzyme-linked immunosorbent assay.Pearson method was used to analyze the relationship between serum levels of SOCS-1,sTREM-2,ACLY and PSI scores in the infection group.Multivariate Logistic regression analysis was performed to analyze factors affecting the disease status of patients with pulmonary Klebsiella pneumoniae infection.The diagnostic value of serum levels of SOCS-1,sTREM-2 and ACLY in patients with Klebsiella pneumoniae infection was analyzed by receiver operating characteristic curve(ROC).Results The levels of white blood cell(WBC)count,procalcitonin(PCT),C-reactive protein(CRP),serum SOCS-1,sTREM-2 and ACLY were higher in the infection group than those in the control group(P＜0.01).In infection group,serum levels of SOCS-1,sTREM-2 and ACLY were positively correlated with PSI scores(r=0.419,0.373,0.391,P＜0.05).Serum levels of SOCS-1,sTREM-2 and ACLY were higher in the severe group than those in the mild group(P＜0.01).The elevated serum SOCS-1,sTREM-2 and ACLY were risk factors for severe disease in patients with pulmonary Klebsiella pneumoniae infection(P＜0.05).The areas under the curve(AUC)of SOCS-1,sTREM-2 and ACLY alone and in combination for the diagnosis of severe pulmonary Klebsiella pneumoniae infection were 0.787,0.837,0.847 and 0.929,respectively,and the combined diagnostic efficiency was the highest.Conclusion Serum SOCS-1,sTREM-2 and ACLY are elevated in patients with pulmonary Klebsiella pneumoniae infection,and their expression levels are related to the condition of patients with pulmonary Klebsiella pneumoniae infection.The combined detection of the three is better than testing alone for severe pulmonary Klebsiella pneumoniae infection.

Objective:To explore the clinical features, genetic characteristics in a child with Miller-McKusick-Malvaux syndrome (3MS) type 1 caused by CUL7 gene variant. Methods:A child diagnosed with 3MS type 1 at the Children′s Hospital Affiliated to Zhengzhou University in February 2021 was selected as the subject of this study. Peripheral blood samples were collected from the child and her parents for genomic DNA extraction. Whole exome sequencing (WES) was performed on the child, and Sanger sequencing was used to validate the candidate variants and analyze their pathogenicity. A literature search was conducted using the keywords "3M syndrome" in the China National Knowledge Infrastructure, Wanfang Data Knowledge Service Platform, and PubMed databases from inception to December 2024. The clinical data of Chinese children with 3MS reported in the literature were summarized. This study was approved by the Medical Ethics Committee of the Children′s Hospital Affiliated to Zhengzhou University (Ethics No. 2024-K-020).Results:①The child was a 6-year-old and 2-month-old female with facial dysmorphism, skeletal abnormalities, and growth and developmental delay. ②WES revealed compound heterozygous variants in the CUL7 gene: c. 2686G>T (p.E896*) and c. 1200delT (p.R401Gfs66). Sanger sequencing confirmed that these two variants were inherited from the child′s father and mother, respectively. According to the American College of Medical Genetics and Genomics (ACMG) Standards and Guidelines for the Interpretation of Sequence Variants, c. 2686G>T (p.E896) was classified as a pathogenic (PVS1+ PM2_Supporting+ PM3), and c. 1200delT (p.R401Gfs*66) was classified as a likely pathogenic (PVS1+ PM2_Supporting). ③ Based on the literature search strategy, 18 relevant articles were identified, including a total of 32 Chinese cases of 3MS, of which 8 were fetuses. A total of 32 Chinese 3MS cases were included in the literature review, of which 8 were fetuses. The majority of these cases carried variants in the CUL7 gene (20/32, 62.5%) and OBSL1 gene (12/32, 37.5%). The main clinical manifestations included intrauterine or postnatal growth and developmental delay (32/32, 100.0%), triangular facies (27/32, 84.3%), and skeletal abnormalities (21/32, 65.6%). Conclusion:The compound heterozygous variants c.2686G>T (p.E896*) and c. 1200delT (p.R401Gfs*66) in the CUL7 gene are likely the genetic cause of 3MS type 1 in the child. For children presenting with facial dysmorphism, skeletal abnormalities, and intrauterine or postnatal growth and developmental delay, 3MS should be considered as a differential diagnosis.

Objective:To investigate the efficacy and safety of trastuzumab deruxtecan (T-DXd) in the treatment of metastatic breast cancer.Methods:A retrospective case series study was conducted. The clinical data of 38 breast cancer patients with metastasis in other parts who received T-DXd treatment in Xi'an International Medical Center Hospital from August 2021 to August 2024 were analyzed. The clinical efficacy and incidence of adverse reactions in patients were recorded, comparison of clinical efficacy in stratified patients based on clinical characteristics was performed, and the progression-free survival (PFS) was analyzed using Kaplan-Meier method.Results:All 38 patients were female, with a median age [ M ( Q1, Q3)] of 55 (42, 60) years; according to the guidelines of the American Society of Clinical Oncology/College of American Pathologists, 13 cases (34.2%) were positive for human epidermal growth factor receptor 2 (HER2) and 25 cases (65.8%) were low in HER2 expression; the Eastern Cooperative Oncology Group (ECOG) physical status scores of 23 cases (60.5%) were 0-2 points and 15 cases (39.5%) were 3-4 points; the median number of T-DXd treatment lines was 4 (2,16) lines. According to the Response Evaluation Criteria in Solid Tumors 1.1, the objective response rate (ORR) of T-DXd treatment was 34.2% (13/38), and the disease control rate (DCR) was 78.9% (30/38); the ORR of patients aged ≤ 50 years old was higher than that of patients aged >50 years old [56.3% (9/16) vs. 18.2% (4/22)], patients with HER2 positive was lower than that of patients with low HER2 expression [100.0 (13/13) vs. 68.0% (17/25)], patients with previous tyrosine kinase inhibitor (TKI) treatment was higher than that of patients without TKI treatment [100.0% (12/12) vs. 69.2% (18/26)], and the DCR of patients with T-DXd treatment for ≥ 4 cycles was higher than that of patients with T-DXd treatment for 1-3 cycles [100.0% (25/25) vs. 38.5% (5/13)], and the differences were statistically significant (all P < 0.05). Among the 38 patients, 19 (50.0%) stopped medication due to disease progression, 11 (28.9%) stopped medication due to economic reasons, 1 (0.8%) stopped medication due to grade 3 nausea and vomiting, and 1 (0.8%) stopped medication due to grade 2 interstitial lung disease (ILD), while the remaining 6 (15.8%) were undergoing T-DXd treatment. The median follow-up time was 9.5 (3.9, 17.8) months, and 16 cases (42.1%) progressed and died; the median PFS time was 5.9 months (95% CI: 3.1-8.7 months). Adverse reactions were mostly grade 1-2; common hematological adverse reactions included leukopenia [18 cases (47.3%)], neutropenia [16 cases (42.1%)], thrombocytopenia [11 cases (28.9%)], and anemia [15 cases (39.5%)]. Non-hematological adverse reactions included nausea [28 cases (73.7%)], vomiting [15 cases (39.5%)], decreased appetite [20 cases (52.6%)], fatigue [22 cases (57.9%)], alopecia [22 cases (57.5%)], elevated aspartate aminotransferase [20 cases (52.6%)], and elevated alanine aminotransferase [15 cases (39.5%)] were more common. Two cases developed interstitial lung disease (ILD), classified as grade 1 and grade 2, respectively. After discontinuation of medication and treatment with methylprednisolone, they returned to normal. Conclusions:T-DXd ≥ 2 line therapy has good efficacy and safety in the treatment of HER2 positive or low expression metastatic breast cancer. Bone marrow suppression and gastrointestinal adverse reactions are the most common, and the occurrence of ILD should be noted in the treatment.