| Hashimoto’s thyroiditis(HT) was first described and named by Hashimoto Hakaru in 1912, which is the most common organ-specific autoimmune disease. It is thought that HT could lead to permanent hypothyroidism and be also associated with thyroid carcinoma and lymphoma, especially papillary thyroid carcinoma(PTC). The critical pathological characters of HT include significant infiltration of plenty of lymphocytes and plasma cells, and lymphoid follicle formation, as well as thyroid follicular epithelial degeneration and destruction until fibrosis in the end. Although HT has been focused more than a century, its etiology and pathogenesis remain unclear. Currently, HT is considered to be caused by both environmental and genetic factors, and it is believed that viral infection might be involve with unknown mechanism.Human parvovirus PVB19(PVB19, B19V) is a single-stranded DNA virus and belongs to Parvoviridae, which could only cause an infection in humans. PVB19 infection is very common in population and associated with a variety of autoimmune diseases, but there is no report about the relationship between PVB19 and HT or PTC until our works. Our group is committed to demonstrate the function of PVB19 in thyroid diseases, and the possible roles of PVB19 in HT pathogenesis and HT-PTC malignant transformation.Positive regulatory domain zinc finger protein 1(PRDM1) is an inhibitory protein with zinc finger domains, and has main function in early embryonic development and plasma cell differentiation. PRDM1 also expressed in T cells and macrophages. Given that the cells mentioned above are all major components of lymphoid follicles, it is suggesting that PRDM1 might play an important role in the lymphoid follicles formation and immune regulation.Based on the above information, we planed to know the answers of the following questions. Does PRDM1 express in HT tissues? In addition, where does it localize in HT? Does PRDM1 have a function in the malignant transformation from HT to PTC and what is the molecular mechanism during the process? At the same time, what is the relationship between PVB19 infection and PRDM1 expression in view of that PVB19 has taken part in HT and PTC pathogenesis? It has been about a century since HT was first reported, and the answers to these questions will undoubtedly not only has important theoretical significance to further clarify the pathogenesis and transformation mechanisms of HT, but also provide new methods for the prevention and treatment of HT and PTC.In this study, we firstly used two tissue arrays to explore the expression of PRDM1 in human and to clarify its tissue-specific protein expression profiles. Chip Ⅰ is containing 16 human tumors and their normal control tissues including esophagus, stomach, colon, rectum, liver, lung, kidney, breast, cervical, ovarian, bladder, lymph nodes, skin, brain, prostate and pancreas(each tissue have 3 cases); ChipⅡ is containing thyroid cancers and adjacent tissues including PTC(23 cases), FTC(16 cases) and normal tissue(8 cases). Secondly, we detected and contrasted PRDM1 expression in surgical specimens including 30 cases of normal thyroid, 20 cases of nodular goiter, 86 cases of HT, 42 cases of thyroid adenoma, 54 cases of PTC, 6 cases of thyroid follicular carcinoma and 9 cases of medullary thyroid carcinoma to ensure its expression pattern in lesions of thyroid. We also semi-quantitated the expression of it in order to investigate its role in HT pathogenesis and development. Then, a paired comparison was performed on 4 cases of fresh HT and 4 cases of fresh PTC to analyze the correlation between PVB19 and PRDM1 gene and protein expression. We also detected the gene changes in the primary human thyroid follicle epithelial cells after transfected with PRDM1 and PVB19 to explore the potential function of PRDM1 in HT pathogenesis. Finally, we analyzed the biological functions of PRDM1 in papillary thyroid cancer cell SW579 by observing the changes of morphology and growth before and after silencing PRDM1 RNA. The main results and findings are as follows:1. In most tissues of chipⅠ, PRDM1 was expressed in the scattered cells in different tissue. We found positive cytoplasmic expression of PRDM1 in 22 cases of PTC and 9 cases of FTC cells but all normal tissues were negative in chipⅡ. Meanwhile, we performed a Spearman correlation analysis between PRDM1 expression and the TNM stage, and the results showed that PRDM1 expression had no significant association with direct invasive ability(T P=0.464) and lymphatic metastasis(N P=0.064). Furthermore, from the analysis of the enlarged samples, we found that the positive rate of PRDM1 expression in HT, TA, PTC, FTC and MTA were 96.5%, 35.7%, 79.6%, 83.3% and 77.8% respectively, while in all normal thyroid tissues and NG were negative. For the positive cases, the intensity of PRDM1 expression varied with different tissues. Statistical analysis showed its positive rates in HT and PTC have a significant difference(HT P= 0.000, PTC P= 0.000) to others.2. The chips of 81 cases of HT and 54 cases of PTC were detected by digital measurement, and the results were analyzed by paired tests. We found PRDM1 and PVB19 expression were significantly correlated in two diseases(HT P= 0.000, PTC P= 0.002). Furthermore, PRDM1 and PVB19 were coexisted in both gene and protein level in 2 cases of fresh HT and 1 case of fresh PTC. Immunofluorescence confocal analysis proved the two proteins were co-localized in the HT and PTC lesions. Moreover, the immunoprecipitation result confirmed their interactions.3. Analysis showed that PRDM1 and nuclear factor kappa B(NFκB) transcription are upregulated in primary human thyroid follicle epithelial cells after transient transfected with PVB19 NS1, and PRDM1 respectively. No significant change of PRDM1 expression was detected in cells transfected with PVB19 VP1. There were significant differences in the changes in the expression of the two genes at each time point between PVB19 NS1 and PVB19 VP1 treatment groups(PRDM1 P=0.017; NFκB P=0.040). The expression of PRDM1 and NFκB reached the peak at 36 h and 24 h after transfection respectively, which indicate NFκB play an important role in the expression of PRDM1 via PVB19 NS1 in HT.4. We detected the effect of PRDM1 on growth of papillary thyroid carcinoma cell SW579 by PRDM1 RNA interference. After knockdown PRDM1 by RNA interference, the apoptosis of SW579 cells increased significantly. And the proportion of G1, G2 and S phase cells were changed to 69.5%, 6.92% and 23.6% from 53.9%, 36.4% and 9.71%, with significant statistical difference(G1 phase, P = 0.030; G2 phase, P = 0.000; S phase,P = 0.006).Based on above results, we can draw conclusions. PRDM1 expresses in many human tissues with different expression pattern. PRDM1 plays an important role in thyroid diseases, especially in the pathogenesis of HT and PTC. PRDM1 is closely related to PVB19 virus infection, and its expression may be induced by PVB19 virus infection. NFκB may involve in the process. PRDM1 expression has no association with invasion and metastasis in thyroid cancer, but its expression is associated with cell proliferation. PRDM1 can also regulate cell cycle and inhibit the apoptosis in PTC cells. |
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