Application Of Epigenetic Sequencing Based On 5hmC And MRI In The Diagnosis And Therapeutic Evaluation Of Breast Cancer

Breast cancer is one of the most common malignant tumor in women and the leading cause of death in female cancer patients around the world.In recent years,the incidence of breast cancer has been on the rise,the age of onset also gradually tends to be younger,seriously endangering the physical and mental health of women.In addition,breast cancer is a highly heterogeneous disease,it can be divided into a variety of molecular subtypes which based on molecular expression profiles,the biological behavior,clinical characteristics and sensitivity to treatment among different molecular subtypes are significantly different.Therefore,early diagnosis and early evaluation or prediction of therapeutic efficacy are of great significance in improving the overall prognosis and quality of life of patients with breast cancer.[Objective] At present,the accuracy of existing examinations for early diagnosis and evaluation of the chemotherapeutic efficacy of breast cancer is limited.In this study,we studied the distribution of 5-hydroxymethylcytosine in the genome of patients with breast cancer,to explore the value of 5hm C in the diagnosis and typing prediction of breast cancer.The second purpose was to study the applied value of MRI in molecular classification and chemotherapy response evaluation of breast cancer by breast imaging reporting terminology.[Materials and methods] Part I: Collected the Blood samples and clinical data of 52 breast cancer patients who were treated in the PLA 307 Hospital from October 1,2017 to November 30,2018.The circulating free DNA,rich in 5hm C in blood samples was detected by 5hm C-Seal technique and high throughput sequencing,the Top100 gene with the most significant difference in 5hm C distribution on cf DNA was screened out between breast cancer group and control group by DEseq2.The same method was used to screen the Top100 gene with significant difference in 5hm C among several molecular subtypes.To explore the value of 5hm C biomarker in diagnosis and molecular subtype analysis of breast cancer.Part II: The breast MRI and clinical data of 175 breast cancer patients who underwent breast MRI examination in our hospital from January 1,2016 to December 28,2017 were collected retrospectively,the molecular subtypes of breast cancer were determined by the expression of estrogen receptor,progesterone receptor,human epidermal growth factor receptor-2 and Ki-67.The relationship between imaging features and molecular subtypes was analyzed by Chi-square test,Fisher's exact probability and cross-tabulation analysis.Part III: Collected and analyzed the MRI images and clinical data of 40 patients with breast cancer admitted to our hospital from October 2017 to November 2018.The objective evaluation criteria of RECIST 1.1 and the diagnostic criteria of Miller &Payne were used to evaluate tumors.According to the postoperative pathology,the patients were divided into complete response group and incomplete response group.Kolmogorov-Smirnov3 test,ANOVA analysis and t test were used to analyze the changes of MRI characteristics of breast cancer before and after chemotherapy.[Results] Part I: By comparing the distribution of 5hm C on cf DNA between breast cancer group and healthy control group,it was found that the 5hm C of cf DNA in breast cancer group basically maintained the distribution characteristic of less distribution at the initiation site of gene transcription.The difference peaks of 5hm C between the control group and the breast cancer group were mainly distributed in the intergenic region and intron region of the genome.Based on the criteria of P < 0.05 and Foldchange > 2,the selected Top100 genes(50 5hm C up-regulated genes and 50 5hm C down-regulated genes)could significantly distinguish the two groups.14 cases of breast cancer and 13 healthy controls were used as verification group to verify the 100 genes.The area under the receiver operating characteristic curve was 0.956.In different molecular subtypes of breast cancer,the screened Top100 gene can be used to distinguish any two groups of five molecular subtypes by the same method.Part II: There were 55 cases of luminal A type(31.4%),71 cases of luminal B type(40.6%),25 cases of HER-2 positive type(14.3%)and 24 cases of tri-negative type(13.7%)in the 175 cases of breast cancer.Most breast cancer with HER-2overexpression associated with lymph node metastasis,while other subtypes had less node metastasis,there was a low correlation between lymph node metastasis and molecular subtypes(C = 0.218,P < 0.05).The rim enhancement was the main pattern in the triple negative type breast cancer,and the other subtypes were mainly heterogeneous enhancement,the correlation between intratumoral enhancement patterns and molecular subtypes was low(C = 0.354,P < 0.05).There was no correlation between other imaging features and molecular subtypes.Part III: Postoperative pathology showed complete reaction in 13 cases and incomplete reaction in 27 cases.After chemotherapy,the tumor volume decreased,the contraction rate of the tumor was about 36.69%,the ADC value increased by 0.36 × 10-3 mm2/s,and the early enhancement rate decreased by 98.43%.The tumor contraction rate and the increase of ADC value after chemotherapy in the complete reaction group were higher than those in the non complete reaction group.The early enhancement rate of the complete reaction group was obviously lower than that of the incomplete reaction group(P < 0.05).[Conclusion] 5hm C has good biomarker characteristics in the diagnosis of breast cancer and the distinction of molecular subtypes,and it is a potential biological index for the diagnosis and classification of breast cancer.Some MRI description signs and measurement parameters of breast cancer can predict molecular subtypes and final chemotherapy effect to a certain extent.Therefore,further study of 5hm C and MRI signs can provide guidance for clinical treatment of tumor patients.