| BackgroundThe oncogene MYC and the anti-apoptotic gene BCL2 are two important driving genes for diffuse large B-cell lymphoma(DLBCL).DLBCL with MYC/IGH and BCL2/IGH rearrangement was classified as double-hit high-grade B-cell lymphoma(DHL)in the 2017 WHO lymphoma classification and such patients only accounted for 5%-10% of DLBCL.The effect of R-CHOP therapy was poor,and high-dose chemotherapy such as R-(DA)-EPOCH combined with autologous hematopoietic stem cell transplantation was needed to improve the prognosis.It was found that about 20%-30% of DLBCL patients had no MYC/IGH and BCL2/IGH rearrangement,but they still had MYC and BCL2 protein expression,which was called double-expression lymphoma(DEL).At present,the consensus of DEL interpretation is that the expression of MYC protein is more than 40% and BCL2 protein is more than 50%.DEL patients also showed poor prognosis,and could not benefit from high-dose chemotherapy combined with autologous hematopoietic stem cell transplantation.Clinical studies have shown that the BCL2 inhibitor venetoclax+RCHOP,the BTK inhibitor ibrutinib+RCHOP and selinexor nuclear transport factor inhibitor,the histone deacetylase inhibitor chidamide combined with R-CHOP may be effective for DEL,but the best treatment plan and the method of guiding precise treatment are still unclear.DEL patients often have some clinicopathological features with poor prognosis,including advanced age,multiple site involvement,late stage,high score of international prognosis index,but they cannot reveal the molecular mechanism of poor prognosis and potential precise treatment methods for DEL patients.In recent years,with the development of high-throughput gene sequencing technology,the research of genomics level has entered a new era,including the sequencing of whole genome,whole exon group,whole transcriptome and genome-wide association studies,etc,which is very important for further studying the pathogenesis of diseases,discovering driving genes and screening new therapeutic targets.Nowadays,next-generation sequencing has gradually been applied to the pathogenesis research,precise diagnosis and treatment,and prognosis evaluation of lymphoma.However,there are few researches on the driver genes of DEL,its mutation characteristics are not clear,and its relationship with poor clinical pathological prognostic factors is unclear.ObjectiveThis study is to analyze the characteristics of driver gene mutations in DEL patients and their correlation with clinicopathological and prognostic characteristics,and to provide a theoretical basis for precision treatment.MethodsWe collected the clinicopathological data of 228 DLBCL patients who were admitted to the Zhengzhou University Cancer Hospital from April 2006 to September2020 and met the enrollment criteria of this study,as well as the detailed information of 32 lymphoma-related hotspot driver gene mutations detected by second-generation sequencing.The statistical software SPSS 26.0 version was used to process and analyze the data.x±S is used to represent the measurement data that meets the normal distribution.The comparison between groups is performed by non-parametric test.If it did not conform to normal distribution,it was described by median,and nonparametric test was used for comparison between groups.Classification variables were tested by bilateral χ2 test.Logistic regression analysis was used for multivariate analysis.Survival analysis was performed by Kaplan-Meier method and log-rank test.P value less than 0.05 was considered statistically different.Results1.Among the 228 DLBCL patients,58 were in the DEL group and 170 were in the non-DEL group.There was no significant difference between the two groups in gender,number of extranodal involved sites,Ann Arbor stage,IPI score,Hans-guided cell origin classification and LDH level(P > 0.05).There were significant differences in clinicopathological features in age(P=0.02),ECOG behavioral state score(P=0.01)and TP53 protein positive(greater than 50%)(P=0.04).The results showed that age >60 years old,TP53 protein positive and ECOG > 1 were positively correlated with DEL patients.The median follow-up time was 22.1±1.49 months.The median progression-free survival(PFS)time was 19.23 ±12.02 months in DEL group and47.70 ±10.63 months in non-DEL group(χ 2 = 3.050,P = 0.081),and the median overall survival(OS)time was 70.1 ±35.62 months and not reached(χ 2 = 0.638,P =0.425).Although there was no statistical difference in survival time between the two groups,the median PFS and OS time of patients in DEL group were significantly lower than those in non-DEL group.2.Among the 228 DLBCL patients,MYC protein was positive in 69 patients.MYC gene abnormalities were found in 13 patients.There were 41 molecular events,including 35 gene point mutations,3 gene fragment abnormalities and 3 gene fusions.No dominant mutation site was found and all the gene fusions were IGH/MYC: 14q32.33/8q24.21.There was no correlation between abnormal MYC gene and MYC protein expression(χ2=2.976,P=0.085).BCL2 protein was positive in 147 patients.BCL2 gene abnormalities were found in 4 patients.There were 12 molecular events,including 9 gene point mutations and 3 gene fusions.No dominant mutation sites were found and all gene fusions were IGH/BCL2: 18q21.33/14q32.33.There was no correlation between abnormal BCL2 gene and BCL2 protein expression(P=0.607).3.32 lymphoma-related driving genes were detected.Univariate analysis showed that BCL6(P=0.005),CD79B(P=0.004)and PIM1(P=0.036)were positively correlated with DEL patients.The multivariate analysis of clinicopathological features including age,ECOG behavioral state score and TP53 protein positive showed that BCL6 mutation(OR=9.130,P=0.001),CD79 B mutation(OR=2.615,P=0.044),TP53 protein positive(OR=3.106,P=0.014)were independently positively correlated with DEL and the clinical characteristics including age and ECOG behavioral status score were not correlated with DEL.ConclusionPatients with DEL have poor clinicopathological and prognostic features.The positive expression of MYC protein and BCL2 protein was not related to gene abnormality.Mutations of the driving genes BCL6 and CD79 B and positivity of TP53 protein are characteristics of DEL patients.The results reveal the complex unfavorable molecular mechanism for DEL,and provide a theoretical support for precision therapy. |
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