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Background N6-methyladenosine (m6A) RNA methylation may play an important role in the process of malignant transformation of cells induced by environmental carcinogens. However, the specific roles and mechanisms need to be further explored. Objective To explore the role and mechanism of m6A binding protein insulin-like growth factor 2 mRNA-binding protein 3 (IGF2BP3) in the malignant transformation of human gastric mucosal epithelial cells GES-1 induced by N-methyl-N'-nitro-N-nitrosoguanidine (MNNG). Methods Based on the GES-1 malignant transformation cells MC-30, a stable knockdown IGF2BP3 MC-30 cell line (MC30-shIGF2BP3, abbreviated as MC30-shI3) was constructed by lentiviral transfection technology, and a negative control group (MC30-NC) was also prepared. Real-time quantitative polymerase chain reaction (qRT-PCR) and Western blotting were applied to detect the mRNA expression and protein levels of IGF2BP3. RNA binding protein immunoprecipitation (RIP-qPCR) was used to examine the combination between IGF2BP3 protein and MYC mRNA in malignant cells MC-30. Furthermore, the stability of MYC mRNA was detected by actinomycin D assay. CCK-8 and Transwell respectively were employed to detect cell proliferation, migration, and invasion. Western blotting was applied to detect the expression of EMT markers (N-cadherin, Vimentin, α-SMA, and Snail). The role of the downstream target gene MYC was further elucidated by a rescue assay in MC30-shI3 cells transfected with a plasmid overexpressing MYC to observe changes in cellular phenotypes (proliferation, migration, invasion) and expression of key EMT proteins. Results Compared with the control group, the expression of IGF2BP3 mRNA was up-regulated after 5, 10, 20, and 40 μmol·L−1 MNNG infection of GES-1 cells (P<0.05). After 20 μmol·L−1 MNNG infection, the expression level of IGF2BP3 mRNA increased with prolongation of exposure time (P<0.05). Compared with the control group, the mRNA and protein expression levels of IGF2BP3 were up-regulated in the 10th, 20th, and 30th generations of 5 μmol·L−1 MNNG malignant transformation (P<0.05). The results of qRT-PCR and Western blotting showed that, compared with the MC30-NC group, the IGF2BP3 and MYC mRNA expression and protein expression decreased in the MC30-shI3 group (P<0.01). The CCK8 and transwell assay results showed that, compared with the MC30-NC group, the cell proliferation, migration, and invasion abilities significantly reduced in the MC30-shI3 group (P<0.01). The results of the Western blotting showed that, compared with the MC30-NC group, the protein levels of EMT markers N-cadherin, Vimentin, α-SMA, and Snail decreased in the MC30-shI3 group (P<0.01). The results of RIP-qPCR showed that, compared with the IgG group, the mRNA level was higher for the enriched MYC in the IGF2BP3 group (P<0.01); the results of the actinomycin D assay showed that, compared with the MC30-NC group, the stability of MYC mRNA significantly reduced in the MC30-shI3 group (P<0.01). While the rescue experiment showed that, compared with the IGF2BP3 knock-down+vector group, the MYC protein level significantly increased in the IGF2BP3 knock-down + MYC over-expression group (P<0.01), the proliferation, migration, and invasion abilities significantly enhanced (P<0.01), and the EMT key proteins (N-cadherin, Vimentin, α-SMA, Snail) increased in the MC30-shI3+MYC group (P<0.01). Conclusion Exposure to MNNG could result in up-regulation of IGF2BP3 expression in GES-1 cells. IGF2BP3 may enhance the proliferation, migration, and invasion of malignantly transformed human gastric epithelial cells by binding to MYC mRNA and increasing its stability and expression level and thus promoting the EMT process, which in turn affects the progression of malignant transformation.
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Objective To investigate the relationship between IGF2BP3 hypomethylation with colon tumor differentia?tion. Methods Tissue samples from 41 colorectal cancer were collected from March 2011 to August 2011 in our hospital, among which 19 cases were well-differentiated adenocarcinoma, 12 cases were of moderately differentiated adenocarcinoma and 10 cases were of poorly differentiated adenocarcinoma. Meanwhile biopsy samples from 12 cases of colonic colitis were collected as a control. The expression of IGF2BP3 was assessed by immunohistochemistry and Western blot. An innovate of ELISA technique was used to examine global methylation levels while IGF2BP3 methylation level was tested by methylation specific PCR technique. Results The expressions of IGFBP3 are higher in all colon cancer groups than that in colitis (P<0.05). The expression of IGFBP3 in poorly differentiated adenocarcinoma is higher than that in all the other groups, but there is no significant difference between its expressions in the well differentiated group and in the moderately differentiated adeno?carcinoma group. The global DNA level and IGFBP3 methylation level of every colon cancer group is lower than those in coli?tis (P<0.05). Also, a tendency of decreasing global DNA and IGFBP3 methylation status was observed comparing well differ?entiated towards poorly differentiated carcinomas (P<0.05). Conclusion IGF2BP3 expression in colorectal cancer is asso?ciated with differentiation of colon cancer tissue. A lower global and IGF2BP3 DNA methylation suggest a worse differentia?tion of colon cancer. DNA hypomethylation may therefore play a regulatory role in the expression of IGF2BP3 in colon cancer tissue.