Biological Characteristics And Clinical Significance Of TET2 Deficiency Myeloid Sarcoma

Objective: Myeloid sarcoma（Myeloid Sarcoma,MS）is a malignant tumor formed by primitive or naive myeloid cells infiltrating organs or tissues other than the bone marrow.It often occurs with various hematological diseases and can also be the first symptom.Epigenetics plays an important role in the occurrence and development of hematological malignancies.As an epigenetic regulatory gene,TET2 regulates gene expression by regulating DNA methylation status.TET2 mutations or deletions are involved in the development of multiple hematopoietic tumors such as Myelodysplastic syndromes（MDS）,acute myeloid leukemia（AML）,myeloproliferative neoplasms（MPN）Plays an important role.Information on epigenetic modifications and treatments related to MS is currently very limited.The purpose of this study is to investigate whether TET2 deletion(TET2^-/-)is associated with the occurrence of myeloid sarcoma,and whether demethylated drugs have potential therapeutic value for MS.method: 1.A 2-year follow-up study was conducted on 214 TET2^-/-mice and 67 wild-type（WT）mice.Blood cells analysis,blood smear,flow cytometry,and observation of liver and spleen were used to identify the stuation of mice.2.Build a mouse model after sublethal dose（800 cGy）irradiation,sarcoma cells from TET2^-/-MS mice,bone marrow cells from TET2^-/-Non-MS mice and WT mice were injected into the recipients respectively.A 7-month study was followed.Flow cytometry analysis,blood cell analysis,and pathological examination were ued to evaluate the malignant nature of the abnormally infiltrating MS cells in TET2^-/-and to determine the transplantability of sarcoma cells.3.The TET2^-/-mice were divided into an experimental group and a control group.The experimental group was treated with 5-Aza-dC.The control group was injected with an equal volume of PBS,followed by a 6-month follow-up study.The survival,Observe the spleen were analyzed to evaluate the efficacy of 5-Aza-dC.4.A total of 436 MDS and 354 a ML patients with complete follow-up information were recruited to this study between 2001 and 2018.The patients were recruited from several clinical centers: The Second Hospital of Tianjin Medical University,the Oncology Hospital of Tianjin Medical University,the Union Hospital of Tongji Medical College of Huazhong University of Science and Technology and the First Affiliated Hospital of Chongqing Medical University.MDS patients were classified according to the WHO 2016 classification.Collect the bone marrow blood samples of these patients,and detect the 112 hematological malignant tumor-related genes in the samples,including TET2,by second-generation sequencing.Patients with TET2^-/-were given a regimen containing decitabine to evaluate the efficacy.5.Statistical software programs,including SPSS 21.0（IBM Corp.）and Graph Pad Prism 5.0（Graph Pad Software,Inc.）were used for data analysis.Quantitative variables were expressed as mean ± standard deviation or median and interquartile range,which were analyzed using a Student’s t-test（for normally distributed variables）,Welch’s t-test（for data with unequal variance）or one?way ANOVA followed by a Bonferroni post hoc test.Qualitative variables were reported as the number of cases and percentages and compared using a χ² test or the Fisher’s exact test.Kaplan?Meier analysis and the log-rank test were adopted to compare differences in survival time.Survival plots were generated using Graph Pad Prism 5.0.P<0.05 was considered to indicated statistically significant differences.Results: 1 All TET2^-/-mice developed spontaneous lethal hematologic malignancies.A total of 93%（n=199）of the TET2^-/-mice developed myeloid malignancies,and MS accounted for 5.5%（n=11）of myeloid malignancies.2.Compared with WT mice and Non-MS mice,MS mice exhibited an increased WBC counts,lower RBC counts and hemoglobin level,morphologic analysis of blood smears from the TET2^-/-MS mice showed dramatically increased leukocytes compared with WT mice,with increased monocytes and/or neutrophils seen in the majority,Flow cytometric analysis of the blood cells revealed dominant populations of Mac1 + /Gr1 + myeloid cells.Compared with WT mice,the survival time of TET2^-/-mice was shorter,but there was no significant difference in the survival time between MS and non-MS mice of TET2^-/-.3.Kaplan-meier survival analysis showed that compared with WT and Non-MS mice,the prognosis of MS mice was poor.The MS mice exhibited high WBC counts,low RBC counts,the normal architecture of spleen and liver was effaced and replaced by diffuse atypical granulocyte,Flow cytometry indicated that the recipient mice in the MS group expressedCD45.2 Mac1 Gr1,suggesting myeloid malignant tumor.4.Among TET2^-/-mice,the proportion of mice with myeloid malignancy in the 5-aza-dc treatment group was significantly lower than that in the control group.At the same time,a mouse with MS in the liver was found in the control group,while no myeloid sarcoma occurred in the 5-aza-dc treatment group.The spleen size and weight of the 5-aza-dc treatment group were significantly smaller than the control group.5.TET2^-/-MDS or AML patients may be accompanied by MS;The demethylated drug desitabine may be an effective and safe treatment option for MDS or AML with MS.Conclusion: 1.TET2^-/-myeloid malignancy can be accompanied by MS in mice.2.ET2^-/-was a poor prognostic factor for hematologic malignancies,but there was no significant difference in survival between TET2^-/-MS and non-ms mice.3.TET2^-/-MS cells of mice are malignant tumor cells and can be transplanted.4.5-aza-dc was effective in the treatment of TET2^-/-myeloid malignancy,and could reduce the occurrence of TET2^-/-myeloid malignancy.5.Desitabine monotherapy may be an effective and safe treatment option for TET2^-/-MS patients.