ABSTRACT
Although aberrant expression of miR-34a, an essential tumor suppressor miRNA, has been frequently observed in colon cancer (CCa), whether miR-34a can regulate CCa progression by modulating other facets of this malignancy (such as multidrug resistance, MDR) remains unknown. Here, we report for the first time that miR-34a expression was significantly downregulated in clinical CCa samples from oxaliplatin-resistant patients and in experimentally established multidrug-resistant CCa cells. By using histoculture drug response assay, we further confirmed that clinical CCa samples with lower miR-34a expression appeared to be more resistant to chemotherapy. Functionally, ectopic expression of exogenous miR-34a resensitized multidrug-resistant HCT-8/OR cells to oxaliplatin treatment, whereas miR-34a inhibition augmented the oxaliplatin resistance in chemosensitive HCT-8 cells. Mechanistically, miR-34a positively regulated the mRNA stability of the ornithine decarboxylase antizyme 2 (OAZ2) by directly targeting its three prime untranslated region (3'UTR). Consequently, suppression of the expression of miR-34a/OAZ2 signaling by chemotherapeutic agents significantly enhanced the activation of MDR-associated ATP-binding cassette (ABC) transporters and antiapoptosis pathways, thus leading to MDR development in CCa cells. Collectively, our combined analysis reveals a critical role of miR-34a/OAZ2 cascade in conferring a proper cellular response to CCa chemotherapy.
Subject(s)
Carrier Proteins/metabolism , Colon/physiology , Colonic Neoplasms/genetics , Drug Resistance, Multiple/genetics , MicroRNAs/genetics , 3' Untranslated Regions/genetics , Antineoplastic Agents/pharmacology , Carcinogenesis , Carrier Proteins/genetics , Cell Line, Tumor , Colonic Neoplasms/drug therapy , Colonic Neoplasms/pathology , Gene Expression Regulation, Neoplastic , Humans , Intracellular Signaling Peptides and Proteins , Organoplatinum Compounds/pharmacology , Oxaliplatin , RNA Stability , RNA, Messenger/genetics , Signal TransductionABSTRACT
OBJECTIVE: To investigate the effects of intercellular adhesion molecule-1(ICAM-1) on the adherence between mesenchymal stem cells (MSC) and endothelial progenitor cells (EPC). METHODS: MSC and EPC were isolated, cultured and expanded from the 6-8 weeks aged C57BL/6 murine bone marrow by in vitro. Immuno-fluorescence was used to detect the expression of ICAM-1 in MSC group, EPC group and co-cultured MSC and EPC group. The mRNA and protein levels of ICAM-1 were detected by RT-PCR and Western blot respectively, then, the ICAM-1 adherence between MSC and EPC was observed by adding different concentration of neutralizing antibody. RESULTS: The expression of ICAM-1 on surface of MSC and EPC could be detected by cell immunofluorescence method. According to results of the semiquantitative fluorescene detection, the fluorescence strength of MSC+EPC co-cultured group (89.02 ± 24.52) was higher than that of MSC group (31.25 ± 2.95) and EPC group (34.32 ± 5.02), and there was statistical difference between them (P < 0.01), but there was no obvious difference between MSC group and EPC group (P > 0.05). RT-PCR detection showed that the expression levels of ICAM-1 in MSC+EPC co-cultured group were higher than that in MSC group and that in EPC group (P < 0.01), and expression level of ICAM in EPC group was higher than that in MSC group (P < 0.01). Western blot detection showed that the expression level of ICAM-1 protein in MSC+EPC co-cultured group (0.33 ± 0.4) was higher than that in MSC group (0.11 ± 0.01) (P < 0.05) and than that in EPC group (0.19+0.02) (P < 0.05), However, the expression level of ICAM-1 protein in EPC group was higher than that in MSC group (P < 0.05). The test of different concentrations against neutralizing antibody showed that with the increasing of concentration of ICAM-1 neutralizing antibody, the adhesion capability of MSC and EPC was gradually decreasing. CONCLUSION: The ICAM-1 can mediate the adherence process between MSC and EPC.
