Abstract
1703
Objectives As a potential tumor suppressor, the expression of GRIM-19 has been reported to decrease in tumors of the lung, prostate, kidney, and breast. However, the role of GRIM-19 in the differentiated thyroid cancer (DTC) is still unknown, thus in this present study, we aimed (1) to detect the location and expression levels of GRIM-19 in thyroid cancer tissue and adjacent normal thyroid tissues; (2) to evaluate the correlation between expression level of the GRIM-19 and clinicopathologic characteristics such as etiology, pathological type, differentiation degree.
Methods Thyroid cancer samples were obtained from 48 patients (female 40, male 8) who underwent surgical resection because of thyroid cancer at West China Hospital between April 2012 and May 2013. At the same time, the matched nontumorous tissues (normal tissues adjacent to malignant lesions) were also obtained. All tissue specimens were confirmed by pathological examination, and all cases had not received any anti-tumor therapy radiotherapy and chemotherapy before surgery. All tissues were divided into two parts, with one fixed in fixed with 4 % formaldehyde for immunohistochemical analysis and the other stored at -80°C for western blot analysis. The score of IHC staining was determined by staining intensity and the proportion of stained cells. The former was scored as the average intensity of staining in positive cells (0, none; 1, weak; 2, intermediate; 3, strong); and the latter, representing the percentage of cells positively stained in each section, was categorized as following: 0, ≤10%; 1, 11-25%; 2, 26-50%; 3, >50%. If a total score, obtained by multiplying both scores, was higher than 2, the GRIM-19 expression was considered positive, otherwise it was negative. We further investigated whether the gender, age, histological type, stage, risk assessment, capsular invasion and lymph nodal metastasis influence the expression of GRIM-19.
Results There were 13 patients categorized as stage I, 17 as stage II, 12 as stage III, and 6 as stage IV. They were also categorized as high risk in 16 patients, intermediate risk in 12 patients, and low risk in 20 patients. In addition, 30 patients have metastatic lymph nodes and 34 patients have capsular invasion. By IHC, GRIM-19 expression in normal thyroid tissue was considered positive in 43 patients (89.6%), while in tumor tissue, positive expression was detected in 26 patients (54.1%). The protein was overexpressed in thyroid cancer tissues with respect to matched nontumorous tissues (P<0.05). With regard to location, the GRIM-19 was located in both the nucleus and in the cytoplasm. Based on western blot analysis of 18 thyroid cancer samples and corresponding normal tissues, the GRIM-19 expression level of tumor tissues was lower than that of normal tissues (Figure 1), which is agreement with the IHC studies. We found that the expression level of GRIM-19 in DTC stages I-II was significantly higher than that of stages III-IV (66.7% vs. 33.3%; p<0.05). In addition, DTC patients with lymph node metastases showed lower positive rate of GRIM-19 expression compared to those without nodal metastases (31.6% vs. 69.0%, p=0.012). The absence of expression of GRIM-19 was significant more frequent in patients with high risk features compared to those with low or intermediate risk (p<0.001). There was no significant difference between groups based on other clinicopathologic features (Table 1).
Conclusions The GRIM-19 expression level was significantly lower in thyroid cancer tissues compared to that in nontumorous tissues, and a significant correlation was revealed between the expression level in tumor tissues and the clinicopathologic features. However, the mechanism of GRIM-19 and its relevant proteins in DTC development need to be further evaluated. This study was supported by National Natural Science Foundation of China (Grant No. 81471692 and 81201118)