Screening Of Thyroid Cancer Specific Hypermethylated Genes At The Protein Level

Objective: To conduct the immunohistochemistry screening study on thyroid gland pathological tissues by selecting the thyroid cancer specific hypermethylated candidate genes, and the relationship was detected between the occurrence of thyroid gland cancer and protein expression defect through analyzing the expression miss rate of thyroid gland cancer specific protein candidate indexes and find specific and sensitive index for gene methylated searching of thyroid gland cancer. Methods: 1) In this study, five kinds of abnormal gland cancer methylation genes such as CDH1, MLH1, TIMP3, ESR1 and MGMT were selected, which had already been confirmed in the preceding relevant literatures. 2) The method of immunohistochemistry was applied to screen the protein expression of thyroid cancer specific hypermethylated genes in 71 cases of thyroid cancers, 26 cases of thyroid adenomas, 15 cases of Hashimoto's thyroiditis, 10 cases of nodular goiters and 12 cases of normal thyroid tissues. 3) An approach to distill DNA of high quality from paraffin wax was established so as to optimize the condition of methylation PCR. Results: 1) The variances of protein expressions of CDH1 and MLH1 all had statistical significance in the thyroid gland various disease organizations (P<0.05), and there was a tendency of stepping up malignant degree of thyroid disease's that following expression degrade of the protein; there was statistical significance that CDH1 was to clinical stages and lymphnode metastasis in thyroid cancer (P<0.01). 2) The variances of protein expressions of ESR1 and MGMT had statistical significance in the thyroid various disease organizations (P<0.05), and there was a tendency that the protein expression stepped up following stepping up the malignant degrees of thyroid diseases. There was a statistical significance of ESR1 expression in the groups of histology types, clinical stages, lymphnode metastasis and prognosis indexes in thyroid cancer (P<0.05). 3) The variances of protein expression of TIMP3 had not statistical significance in the thyroid gland various disease organizations (P>0.05), but from total positives change tendency, protein expression of TIMP3 had degraded following the stepping up malignant degrees of thyroid diseases. 4) In the thyroid cancer, MLH1 had a certain correlation to the protein expression of CDH1, TIMP3, and MGMT with the protein expression of ESR1 was interrelated(P<0.05). 5) In 5 cases of MTC, protein of CDH1 all expressed and protein of ESR1 all did not express; in 3 cases of PUTC, protein of CDH1 and ESR1 all expressed protein of TIMP3 all did not express. 6) In the thyroid cancer, the protein expression of CDH1, MLH1, TIMP3, ESR1 and MGMT all had not statistical significance at gender, age and ethnic-group (P>0.05) . Conclusion: 1) The low protein expressions of CDH1, MLH1 and TIMP3 may be the cause of thyroid cancer developing. The low protein expression of CDH1 likely is an important factor at metastasis of thyroid neoplasm. 2) The high protein expression of ESR1 in thyroid cancer help the tumor cell to propagate, so block its function probably provide a new strategy for the therapy of thyroid cancer. 3) To may be connection with the malignant degrees of thyroid cancer, the high protein expression of MGMT in thyroid cancer will be used to the candidate index of clinic molecular diagnosis. 4) In the thyroid cancer, MLH1 has a certain correlation to the protein expression of CDH1, TIMP3, and MGMT with the protein expression of ESR1 is interrelated 5) The protein expression of 5 kinds of genes above will may be used as the common checking signs at gender, age and ethnic-group in thyroid cancer. 6) Screening of protein expression of CDH1, MLH1 and TIMP3 will be considered in methylation studies of thyroid cancer.