Objective To observe the expressions of DNA methyltransferases (DNMTs) 1, 3a and 3b in retinoblastoma (RB). Methods Sixty-two RB samples and six normal retinas were studied, including 17 poorly differentiated and 45 well differentiated samples; 16 invasive and 46 non-invasive samples. The expressions of DNMT1, 3a, and 3b, and Ki-67 were detected using immunohistochemical analysis. Brown staining of nuclei was considered to represent the positive stain for DNMT1, 3a and 3b, and ki-67, blue staining as negative. The level of high expression of nuclear staining was, positive cells in DNMT1ge;65%, in DNMT3age;60% and in DNMT3bge;40%. The correlations of DNMT1, 3a and 3b expression in RB samples, and MIB-1 labeling index were analyzed. Results Viewed under the light microscope, negative expressions of DNMT1, 3a and 3b were demonstrated in normal retinas, however, positive expression was observed in RB samples, with 100% in DNMT1, 98% in DNMT3a and 92% in DNMT3b. Comparing well differentiated RB samples with poorly differentiated samples, significant differences were found in high expression of DNMT1 (chi;2=12.57,P＜0.05) and DNMT3a (chi;2=10.54,P＜0.05); also in the positive cells of DNMT1 (U=179,P＜0.05) and DNMT3a (U=198,P＜0.05). No significant difference was found comparing high expression (chi;2=1.5,P＞0.05) and positive cells (U=307,P＞0.05) of DNMT3b. When comparing invasive tumor tissues with non-invasive tumors, significant differences were shown between high expression (chi;2=4.72,P＜0.05) and positive cells comparing DNMT1 (U=236,P＜0.05). No significant difference was shown in high expression (chi;2=3.53,0.84; P＞0.05) in DNMT3a and DNMT3b, or in comparison with positive cells (U=338,257;P＞0.05). The expression of DNMTs was positively correlated with the MIB-1 labeling index in RB tissues (R2=0.554,0.376,0.219;P＜0.05). Conclusion There are high expressions of DNMT1,3a,and 3b in RB.
Objective To observe the expression and relationship of high-mobility group A(HMGA)1, HMGA2, MIB-1 labeling index (LI) and let-7 in retinoblastoma (RB). Methods Forty-four RB samples were studied, including 11 poorly-differentiated samples, 33 well-differentiated samples; eight invasive and 36 non-invasive samples. The expression of HMGA1, HMGA2 and MIB-1 LI in RB were analyzed by immunohistochemitry. The HMGA1, HMGA2 were scored on a scale of 0 to high expression. 0: no expression; low: 1%-10%; medium: 11%-50%; high: ＞50%. The MIB LI were scored on a scale of 0 to high expression. 0: no expression; low: 1%-40%; high: ＞40%. Semiquantitative reverse transcription-polymerase chain reaction was used to assay the let-7 expression level: ge;80% showed no significantly decreased expression; 60%-79% showed medium decrease in expression; ＜60% highly decreased in expression. ResultsIn 44 RB samples, there were 14 cases with no HMGA1 expression (32%), 11 cases with low expression (25%), 10 cases with medium expression (23%), and nine cases with high expression (20%). Expression level of HMGA1 was significantly higher in poorly differentiated RB than in well-differentiated RB (chi;2=11.3,P＜0.01); however, no statistically significant difference was found between invasive tumors and noninvasive tumors (chi;2=5.9,P＞0.05). There were 11 cases with no HMGA2 expression (25%), 11 cases with low expression (25%), nine cases with medium expression (20%), and 13 cases with high expression (30%). Expression level of HMGA2 was significantly higher in poorly differentiated and invasive RB than in well-differentiated and noninvasive RB respectively (chi;2=20.9, 8.7;P＜0.05). There were 4 cases with no MIB-1 LI expression (9%), 18 cases with low expression (41%), and 22 cases with high expression (50%). Expression level of MIB-1 LI was significantly higher in poorly differentiated RB than in well-differentiated RB (t=5.2,P＜0.05). Higher expression of MIB-1 LI was found in invasive tumors than in noninvasive tumors, with no significant difference (t=-1.1,P＞0.05). Twenty-seven cases had no significantly decreased expression of let-7 (61%). There were eight cases with medium decreased expression (18%) and nine cases with highly decreased expression (21%). Correlation analyses revealed that MIB-1 LI expression significantly correlated with HMGA1and HMGA2 proteins (r=0.327, 0.602;P＜0.05). A significantly inverse correlation existed between let-7 expression and HMGA1, HMGA2 proteins and MIB-1 LI respectively (r=-0.247,-0.310,-0.392;P＜0.05). Conclusions Overexpression of HMGA1, HMGA2 and MIB-1 LI and down regulation of let-7 were demonstrated in RB. Supplying let-7 to RB cells can possibly inhibit HMGA1 and HMGA2 expression.