Programmed cell death 4 (PDCD4) is a RNA-binding protein that acts as a tumor suppressor in many cancer types, including colorectal cancer (CRC). During CRC carcinogenesis, PDCD4 protein levels remarkably decrease, but the underlying molecular mechanism for decreased PDCD4 expression is not fully understood. In this study, we performed bioinformatics analysis to identify miRNAs that potentially target PDCD4. We demonstrated miR-181b as a direct regulator of PDCD4. We further showed that activation of IL6/STAT3 signaling pathway increased miR-181b expression and consequently resulted in downregulation of PDCD4 in CRC cells. In addition, we investigated the biological effects of PDCD4 inhibition by miR-181b both in vitro and in vivo and found that miR-181b could promote cell proliferation and migration and suppress apoptosis in CRC cells and accelerate tumor growth in xenograft mice, potentially through targeting PDCD4. Taken together, this study highlights an oncomiR role for miR-181b in regulating PDCD4 in CRC and suggests that miR-181b may be a novel molecular therapeutic target for CRC.

The nuclear paraspeckle assembly transcript 1 (abbreviated as NEAT1), a nuclear sufficient long noncoding RNA (abbreviated as lncRNA), has aroused a rising concern in recent years. As uncovered by reports, the increase in NEAT1 is related to the deteriorated prognosis of lung cancer, breast cancer, hepatocellular cancer, and colorectal cancer (abbreviated as CRC). Thus far, the mechanism of NEAT1 has not been elucidated by the existing researches. The impact of knockdown of both NEAT1 and its predicted downstream miR-193a-3p in CRC cells was examined here to delve into their interactions and mechanisms. Additionally, the target of miR-193a-3p, Kirsten rat sarcoma viral oncogene homolog (abbreviated as KRAS), was also predicted by bioinformatics algorithms. Small interfering RNA and antisense oligonucleotides that inhibit NEAT1, as well as overexpression or knockdown of miR-193a-3p, were adequately drawn upon to confirm that NEAT1 serves as a miR-193a-3p sponge or competing endogenous RNA, to impact miR-193a-3p's further functions, including modulating KRAS proteins, both in vitro and in vivo. Generally, lncRNA NEAT1/hsa-miR-193a-3p/KRAS axis was substantiated in CRC cells and could provide novel insight into both diagnostic and therapeutic advancement in CRC.

Protein-tyrosine phosphatase MEG2 (MEG2) is a classic tyrosine-specific protein tyrosine phosphatase (PTP). It has been reported that MEG2 participates in the carcinogenesis of the breast and liver. However, functions of MEG2 in gastric cancer remain poorly understood.

Programmed cell death 4 (PDCD4) is a novel tumor suppressor gene and a promising target for anticancer therapies. PDCD4 is frequently downregulated in various human cancers; however, the molecular mechanism accounting for the loss expression of PDCD4 in cancers is not fully understood. In this study, we identified specific targeting sites for miR-208a-3p in the 3'-untranslated region (3'-UTR) of the PDCD4 gene which regulated PDCD4 expression. We demonstrated that miR-208a-3p suppressed apoptosis in gastric cancer cells by targeting PDCD4. We also showed that miR-208a-3p promoted the development of tumor growth in xenograft mice by negatively regulating PDCD4. Taken together, this study revealed a critical role for miR-208a-3p as an oncogenic miRNA in gastric carcinogenesis and it may provide a potential novel target for gastric cancer diagnosis and therapy.

miR-214 is an important oncomiRNA and is upregulated in various types of cancer, including gastric cancer. However, the molecular mechanism underlying the ectopic expression and function of miR-214 in gastric cancer is largely undefined. In this study, we found that miR-214 induces the Warburg effect and promotes the migration and proliferation of human gastric cancer cells. According to the mechanistic analysis, miR-214 expression is induced by environmental hypoxia, and miR-214 mediates hypoxia-induced functions. We then explored the molecular mechanism by which miR-214 enhances the Warburg effect in gastric cancer cells and identified the adenosine A2A receptor (A2AR) and PR/SET domain 16 (PRDM16) genes as the direct targets of miR-214. In conclusion, miR-214 inhibits A2AR and PRDM16 expression and enhances the Warburg effect in gastric cancer cells, thus promoting the proliferation and migration of gastric cancer cells. This study highlights an important role for the hypoxia-miR-214-PRDM16/A2AR pathway in the tumourigenesis of gastric cancer and may facilitate the development of new therapeutics against hypoxic tumours.