ABSTRACT
Purpose@#Neoadjuvant chemotherapy (NAC) is widely used to treat breast cancer (BC). The prediction and evaluation of chemotherapy responses remains a significant challenge. @*Methods@#MicroRNAs (miRNAs) play a crucial role in cancer drug resistance. We used a miRNA microarray and identified that miR-638 is downregulated in chemoresistant cases.However, the exact role of miR-638 and the underlying mechanisms of chemoresistance remain unclear. Using real-time quantitative reverse transcription polymerase chain reaction, we found significant downregulation of miR-638 in chemoresistant patients compared with chemosensitive patients. To explore the function of miR-638, we overexpressed and inhibited miR-638 expression in MDA-MB-231 and MCF-7 cells by transfecting them with miR-638 mimics and miR-638 inhibitor, respectively. Cell proliferation and apoptosis were measured using MTS and flow cytometry, respectively. A minimal patient-derived xenograft (MiniPDX™) model was established to evaluate the chemosensitivity to different drugs. @*Results@#The results showed that cell proliferation decreased and cell apoptosis increased in cells transfected with the miR-638 mimic, and cell proliferation and apoptosis were reversed with transfection of miR-638 inhibitor compared with the control group. Among patients who received 5-fluorouracil (5-FU), miR-638 expression levels were lower in the chemoresistant group than in the chemosensitive group. The MiniPDX™ model showed that MDA-MB-231 cells overexpressing miR-638 were more susceptible to 5-FU treatment in vivo. @*Conclusion@#We provided evidence of acquired resistance to 5-FU caused by miR-638 deficiency. Alterations in miR-638 may be used with 5-FU chemotherapy during NAC for BC.
ABSTRACT
<p><b>OBJECTIVE</b>To investigate the expression of microRNA-100 (miR-100) in human gastric cancer cells and its role of miR-100 in migration, invasion and proliferation in gastric cancer cell line SGC7901.</p><p><b>METHODS</b>Total RNAs were extracted from formalin-fixed and paraffin-embedded tissue samples of SGC7901 cells, gastric cancer (50 cases), non-tumor (18 cases) and lymph nodes with metastases (18 cases). The expression of miR-100 was examined by reverse transcription (RT)-qPCR. Additionally, SGC7901 cells were transfected with Pre-miR-100 and negative control constructs, and then their ability of migration, invasion and proliferation in vitro was documented after 48 hours.</p><p><b>RESULTS</b>RT-qPCR showed that although miR-100 expressed in all samples, compared to non-tumour tissues, the expression was lower both in SGC7901 cells and gastric cancer tissues (P = 0.0077, P < 0.01). SGC7901 cells and primary gastric cancer tissues with lymph nodes metastasis had lower miR-100 expression than those of without lymph node metastasis (P = 0.0361, P = 0.0356). The migration ability and invasion of SGC7901 cells transfeced with pre-miR-100 decreased as compared with control cells (P = 0.0025, P = 0.0028 respectively). However, miR-100 expression had no significant effects on the cell proliferation.</p><p><b>CONCLUSIONS</b>Expression of miR-100 inhibits the migration and invasion of gastric cancer cells without significant alteration of proliferation. Therefore, miR-100 may play an inhibitory role in the progression of gastric carcinoma.</p>