miR-34a mimic or pre-mir-34a, which is the better option for cancer therapy? KatoIII as a model to study miRNA action in human gastric cancer cells

Background Aberrantly expressed microRNAs play important roles in gastric tumorigenesis. However, use of miRNAs as a therapeutic option in gastric cancer still remains as a challenging problem. Methods We performed transient transfection of miR-34a-5p mimic and stable transfection of pre-mir-34a into KatoIII cells. Then, we evaluated the effect of transfected miRNAs on numerous cellular and molecular processes. Results Following transient transfection of miR-34a-5p mimic at 25 nM-a commonly used concentration-into KatoIII cells, inhibition of two target genes expression, namely Notch1 and beta-catenin, was not observed, but a non-significant marginal increase of these genes was detected. No changes were detected in the percentage of apoptotic cells as well as in CD44 + and EpCAM + cells after 25 nM miR-34a-5p mimic transfection. Interestingly, stable transfection of pre-mir-34a into KatoIII cells (named as KatoIII-pGFPC1-34a cells) caused a significant repression in beta-catenin protein and Notch1 mRNA levels (p < 0.05 and p < 0.01, respectively) relative to equivalent control (KatoIII- pGFPC1-empty cells). The percentage of CD44 + cells in the KatoIII-pGFPC1-34a cells (< 40%) was significantly lower than that in control cells (similar to 95%) (p < 0.05). An increase of similar to 3.5% in apoptotic cells and a slower proliferation rate were detected in KatoIII-pGFPC1-34a cells. Conclusions Our study revealed that the effect of miR mimic in target gene repression can be dependent to its concentration as well as to the cell type. Meanwhile, our findings further support a regulatory function for pre-miRNAs in target repression and will help to develop effective therapeutic strategies in cancer treatment.

Automated summary

The study revealed that the effect of miR mimic in target gene repression may depend on its concentration and cell type, while pre-miRNAs may have a regulatory function in target repression. These findings will help to develop effective therapeutic strategies in cancer treatment.