CPEB1 orchestrates a fine-tuning of miR-145-5p tumor-suppressive activity on TWIST1 translation in prostate cancer cells

Pro-tumorigenic role of lnc-ZNF30-3 as a sponge counteracting miR-145-5p in prostate cancer

BACKGROUND

Prostate cancer remains one of the deadliest neoplasms in developed countries. Identification of new molecular markers that predict the onset and progression of the disease could improve its clinical management. Low miR-145-5p expression is consistently found in primary tumors and metastases, but the regulatory mechanisms governing its functions remain largely unknown.

METHODS

Bioinformatics analysis was conducted to identify [1] a set of novel potential competing endogenous lncRNAs for sponging of miRNA-145-5p in prostate cancer and [2] miR-145-5p and other EMT-related miRNAs response elements in lnc-ZNF30-3. Quantification of miR-145-5p, lnc-ZNF30-3, and TWIST1 expression levels in tumor tissues in RNA sequencing datasets of our and TCGA PRAD cohorts revealed a correlation with clinical outcome of prostate cancer patients. Biochemical and cell biology approaches, such as RNA pull-down, western blot, immunostaining, and wound healing assays were used for evaluation of the impact of TWIST1/miR-145/ lnc-ZNF30-3 interactions in prostate cancer cells altered in miRNA and lncRNA expression.

RESULTS

We identified a few potential lncRNA sponges of miR-145-5p, including lnc-ZNF30-3. It contains five response elements for miR-145-5p, but also other miRNAs targeting EMT transcription factors. Lnc-ZNF30-3 is significantly upregulated in prostate cancer cell lines and tumor tissues, and its high expression is correlated with poor patient prognosis. We demonstrated that lnc-ZNF30-3 is associated with AGO2 and specifically interacts with the miR-145-5p seed region. Knockdown of lnc-ZNF30-3 results in decreased migration of prostate cancer cells and downregulation of EMT drivers such as TWIST1 and ZEB1 at both the RNA and protein levels. These phenotypic and molecular features of lnc-ZNF30-3-depleted cells are partially rescued by miR-145-5p inhibition.

CONCLUSIONS

Collectively, our results point to lnc-ZNF30-3 as a novel competing endogenous lncRNA for miR-145-5p and other miRNAs that target TWIST1 as well as other EMT transcription factors. Prostate cancer patients with high lncRNA expression in primary tumors show lower survival rate suggesting that lnc-ZNF30-3 may contribute to prostate cancer progression and metastasis.

miR-145-5p Inhibits Neuroendocrine Differentiation and Tumor Growth by Regulating the SOX11/MYCN Axis in Prostate cancer

Recent studies have shown that the downregulation of miR-145-5p in prostate cancer (PCa) is significantly associated with poor differentiation and prognosis. We aimed to investigate the biological role of miR-145-5p in the neuroendocrine differentiation (NED) of PCa. In this study, TheCancer Genome Atlas was used to identify the association of miR-145-5p with PCa. The functions of miR-145-5p were evaluated using the Cell Counting Kit-8 (CCK-8) assay and cell cycle analysis. We validated changes in cell cycle control by testing the expression of cyclin-related genes by western blot. The luciferase reporter assay was performed to test miR-145-5p-targeting genes and direct transcriptional targets of SOX11. The expression of miR-145-5p was found to be significantly downregulated in castration-resistant PCa, and this was correlated with higher Gleason score and prostate-specific antigen. We confirmed these results using PC3 and LNCaP cell lines depicted a gradual decline of miR-145-5p while the cells were cultured under androgen depletion conditions. Moreover, the knockdown of miR-145-5p significantly promoted NED and proliferation of LNCaP cells, whereas overexpression of miR-145-5p significantly inhibited NED and proliferation of LNCaP cells. Mechanistically, we found that SOX11 was a direct target of miR-145-5p, which regulates MYCN might mediate induction of NED and proliferation of LNCaP cells. Furthermore, knockdown of miR-145-5p promoted tumor growth in vivo. Our findings suggest that miR-145-5p can inhibit NED and tumor growth by targeting SOX11, which regulates the expression of MYCN, and that this could be a novel therapeutic strategy for preventing the progression of PCa.

RNA-binding proteins and cancer metastasis

RNA-binding proteins (RBPs) can regulate gene expression through post-transcriptionally influencing all manner of RNA biology, including alternative splicing (AS), polyadenylation, stability, and translation of mRNAs, as well as microRNAs (miRNAs) and circular RNAs (circRNAs) processing. There is accumulating evidence reinforcing the perception that dysregulation or dysfunction of RBPs can lead to various human diseases, including cancers. RBPs influence diverse cancer-associated cellular phenotypes, such as proliferation, apoptosis, senescence, migration, invasion, and angiogenesis, contributing to the initiation and development of tumors, as well as clinical prognosis. Metastasis is the leading cause of cancer-related recurrence and death. Therefore, it is necessary to elucidate the molecular mechanisms behind tumor metastasis. In fact, a growing body of published research has proved that RBPs play pivotal roles in cancer metastasis. In this review, we will summarize the recent advances for helping us understand the role of RBPs in tumor metastasis, and discuss dysfunctions and dysregulations of RBPs affecting metastasis-associated processes including epithelial-mesenchymal transition (EMT), migration, and invasion of cancer cells. Furthermore, we will discuss emerging RBP-based strategy for the treatment of cancer metastasis.

Bone Marrow Mesenchymal Stem Cells (BMSCs) Restrain the Malignant Behaviors of A549 Lung Cancer Cells Under Hypoxia via miR-145

Deriving from bone marrow, the bone marrow mesenchymal stem cells (BMSCs) possess multipolar chemotaxis, proliferation potential, along with the capability to differentiate into various types of cells. Moreover, the hypoxic stimulation can effectively induce BMSCs differentiation. This study intends to explore the impediment of BMSCs on malignant behaviors of lung cancer stem cells under hypoxia. A co-culture system of BMSCs with A549 cells was established and then assigned into normoxia group, hypoxia group (50, 100, and 200 nmol/L) followed by analysis of cell viability by CCK-8 assay and miR-145 expression by qRT-PCR. In addition, A549 cells were grouped into NC group, miR-145-mimics group, and miR-145-inhibitors group followed by analysis of cell invasion and levels of miR-145 and Oct4. Hypoxia group exhibited a reduced cell viability and higher miR-145 expression (146.01±21.23%) compared to normoxia group (P < 0.05). Transfection of miR-145-mimic significantly upregulated miR-145 and decreased cell invasion (7.49±1.43%) compared with miR-145-inhibitors group or NC group (P < 0.05). Meanwhile, Oct4 level in miR-145-mimics group (0.934±2.98) was significantly decreased (P < 0.05). In conclusion, under hypoxia condition, the co-culture with BMSCs can upregulated miR-145 level, effectively reduce the viability of lung cancer stem cells and restrain proliferation capability.