Abstract
This study aimed to investigate the relationship between the expression of microRNA (miR)‐181b, protein inhibitor of activated STAT3 (PIAS3) and STAT3, and to examine the function of the miR‐181b/PIAS3/STAT3 axis on the Warburg effect and xenograft tumour growth of colon cancer. Moreover, a positive feedback loop between miR‐181b and STAT3 that regulated the Warburg effect in colon cancer was explored. A luciferase reporter assay was used to identify whether PIAS3 was a direct target of miR‐181b. The gain‐of‐function and loss‐of‐function experiments were performed on HCT 116 cells to investigate the effect of miR‐181b/PIAS3/STAT3 on the Warburg effect and xenograft tumour growth of colon cancer, as determined by commercial kits and xenograft experiments. The relationship between the expression of miR‐181b, PIAS3 and STAT3 in HCT 116 and HT‐29 cells was determined using RT‐qPCR and Western blot. We found miR‐181b was a direct regulator of PIAS3. miR‐181b promoted the Warburg effect and the growth of colon cancer xenografts; however, these effects could be reversed by PIAS3. miR‐181b expression interacted with STAT3 phosphorylation in a positive feedback loop in colon cancer cells via regulating PIAS3 expression. In conclusion, this study for the first time demonstrated that miR‐181b contributed to the Warburg effect and xenograft tumour growth of colon cancer by targeting PIAS3. Moreover, a positive feedback loop between miR‐181b and STAT3 that regulated the Warburg effect in colon cancer was also demonstrated. This study suggested miR‐181b/PIAS3/STAT3 axis as a novel target for colon cancer treatment.
Highlights
Colon cancer is a leading cause of cancer death in the worldwide.[1,2] About 1 million people suffer colon cancer every year, and it causes 0.6 million deaths annually around the world.[3]
The results from luciferase reporter assay revealed that compared with the cells transfected with the miR‐181b negative control (miR NC), the luciferase activity of pGL‐protein inhibitor of activated Signal transducer and activator of transcription 3 (STAT3) (PIAS3) 3′untranslated region (3′UTR) wt was significantly suppressed in the cells transfected with the miR‐181b mimic; there was no significant difference in the luciferase activity of pGL‐PIAS3 3′UTR mut between miR NC and miR‐181b mimic ‐ transfected cells (Figure 1C)
We found miR‐181b mimic was able to suppress luciferase activity encoded by a reporter gene fused to the PIAS3 3′UTR
Summary
Colon cancer is a leading cause of cancer death in the worldwide.[1,2] About 1 million people suffer colon cancer every year, and it causes 0.6 million deaths annually around the world.[3]. It is necessary to investigate the molecular mechanisms underlying colon cancer development so as to contrive novel strategies for colon cancer treatment. Cancer cells rewire their metabolism to promote cancer progression. It has been shown that ectopic expression of PIAS3 in cancer cells can suppress the transcriptional activity of STAT3 and inhibit tumour growth.[17,18]. We explored the relationship between miR‐ 181b (miR‐181b‐5p), PIAS3 and STAT3, and investigated the function of miR‐181b/PIAS3/STAT3 axis on the Warburg effect and xenograft tumour growth of colon cancer. A miR‐181b‐ STAT3 positive feedback loop that contributed to the Warburg effect in colon cancer cells was demonstrated as well
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