Abstract:
Background and purpose: PDCD4 may be inhibited by miR-21 to regulate the malignant behaviors of colon cancer such as invasion and migration. This study aimed to explore the function of colon cancer HT-29 cell lines by downregulating miR-21 expression and discuss the mechanisms and relationship between miR-21 and PDCD4 in colon cancer malignant behaviors. Methods: simiR-21 was transfected into colon cancer cell line HT- 29 to downregulate the expression of miR-21. Proliferation, apoptosis, migration and invasion were detected by MTT, flow cytometry and Transwell assay after transfection. PDCD4 expression was detected by Western blot and qRTPCR.  Results: The qRT-PCR analysis result proved that the transfection efficiency was 60%-65%. MTT analysis result showed that the proliferations of HT-29 cells were inhibited after the transfection of miR-21 for 72, 96, 120 h (t=1.276, P<0.05; t=3.276, P<0.01; t=4.523, P<0.01). Comparing with si-negative control and miR-21 groups, flow cytometry result showed that the apoptosis rate was increased after miR-21 expression downregulated (t=2.132, P<0.05; t=3.524, P<0.05). Transwell assay result showed that migration (t=2.423, P<0.05; t=3.153, P<0.05) and invasion(t=3.245, P<0.05; t=5.236, P<0.05) were inhibited; Western blot result showed that PDCD4 expression was up-regulated at protein level(t=2.342, P<0.05; t=4.215, P<0.05); qRT-PCR result showed that PDCD4 expression was up-regulated at mRNA level(t=2.261, P<0.05; t=3.492, P<0.05). Conclusion: The proliferation, migration and invasion are the inhibited, and apoptosis is attenuated after miR-21 downregulated by simiR-21 transfection, PDCD4 expression is up- regulated. miR-21 may enhance the malignant behavior of cancer cells by downregulating the PDCD4 expression, miR- 21 might be a target gene for colon cancer therapy.

Key words: Colon cancer, Proliferation, Apoptosis, miR-21, HT-29