FOXJ3 Regulates Cell Proliferation and Motility Through Modulating Snail Expression in Breast Cancer Cells

BACKGROUND/AIM

Breast cancer is the most common cancer among women and the leading cause of cancer-related deaths worldwide. Despite various therapeutic strategies, its impact on the survival rate and quality of life of patients remains limited. The Forkhead Box J3 (FOXJ3) transcription factor has been implicated in various cancers, including lung cancer, tongue squamous cell carcinoma, prostate cancer, and colorectal cancer. However, the role of FOXJ3 in breast cancer has not been elucidated. This study aimed to investigate the role of FOXJ3 in breast cancer development, migration, and invasion.

MATERIALS AND METHODS

FOXJ3 expression was analyzed in patient tissues and breast cancer cell lines. Loss-of-function and gain-of-function studies were performed using MDA-MB-231 and MCF7 cell lines, respectively. Cell proliferation, migration, and invasion assays were conducted, and the effects of FOXJ3 on Snail expression were examined.

RESULTS

FOXJ3 is over-expressed in breast cancer tissues compared to normal counterparts and in various breast cancer cell lines. By modulating FOXJ3 expression in breast cancer cell lines, we observed its influence on cell proliferation, migration, and invasion. Microarray analysis and subsequent validation showed that FOXJ3 modulates Snail expression, a well-known transcription factor involved in epithelial-mesenchymal transition.

CONCLUSION

FOXJ3 plays a role in cell proliferation, migration, and the regulation of Snail expression and may be a potential therapeutic target for breast cancer treatment.

Circular RNA circSLC8A1 inhibits the proliferation and invasion of non-small cell lung cancer cells through targeting the miR-106b-5p /FOXJ3 axis

Circular RNA derived from the SLC8A1 gene (circSLC8A1) has been implicated in the pathogenesis of several types of cancers. However, the role of circSLC8A1 in non-small cell lung cancer (NSCLC) remains unclear. In the present study, the expression levels of circSLC8A1 in NSCLC tissues and cell lines were determined by qRT-PCR analysis. Function-gain-assays were then carried out to further validate the role of circSLC8A1 in NSCLC in vitro. Online prediction software and the subsequent luciferase reporter assay were used to identify the target genes of circSLC8A1 and microRNA (miR)-106b-5p. CircSLC8A1 was found to be downregulated in NSCLC tissues and cell lines. Overexpression of circSLC8A1 significantly inhibited the proliferation and invasion of NSCLC cells. Further investigations shown that circSLC8A1 was able to bind to miR-106b-5p as well as inhibit the expression of miR-106b-5p in NSCLC cells. MiR-106b-5p mimics reversed the inhibitory effects of circSLC8A1 overexpression on cell proliferation and invasion. Furthermore, we found that forkhead box J3 (FOXJ3) to be a target gene of miR-106b-5p in NSCLC cells. Knockdown of FOXJ3 reversed the inhibitory effects of miR-106b-5p inhibitor on cell proliferation and invasion. Collectively, these findings indicate that circSLC8A1 exhibits anti-tumor activity in NSCLC, which might be mediated by the miR-106b-5p/FOXJ3 axis. The circSLC8A1/miR-106b-5p/FOXJ3 axis may thus represent a promising therapeutic target for the management of NSCLC.

The miR-27a/FOXJ3 Axis Dysregulates Mitochondrial Homeostasis in Colorectal Cancer Cells

Simple Summary

Cellular and mitochondrial metabolism can be dysregulated during tumorigenesis. miR-27a plays a central role in redirecting cell metabolism in colorectal cancer. In this study, we searched for new miR-27a targets that could influence mitochondria and identified FOXJ3 a master regulator of mitochondrial biogenesis. We validated FOXJ3 as an miR-27a target in an in vitro cell model system that was genetically modified for miR-27a expression and showed that the miR-27a/FOXJ3 axis down-modulates mitochondrial biogenesis and regulates other members of the pathway. The miR-27a/FOXJ3 axis also influences mitochondrial dynamics, superoxide production, respiration capacity, and membrane potential. A mouse xenograft model confirmed that miR-27a downregulates FOXJ3 in vivo and a survey of the TCGA-COADREAD dataset supported the inverse relationship of FOXJ3 with miR-27a and the impact on mitochondrial biogenesis. The miR-27a/FOXJ3 axis is a major actor in regulating mitochondrial homeostasis, and its discovery may contribute to therapeutic strategies aimed at restraining tumor growth by targeting mitochondrial activities.

Abstract

miR-27a plays a driver role in rewiring tumor cell metabolism. We searched for new miR-27a targets that could affect mitochondria and identified FOXJ3, an apical factor of mitochondrial biogenesis. We analyzed FOXJ3 levels in an in vitro cell model system that was genetically modified for miR-27a expression and validated it as an miR-27a target. We showed that the miR-27a/FOXJ3 axis down-modulates mitochondrial biogenesis and other key members of the pathway, implying multiple levels of control. As assessed by specific markers, the miR-27a/FOXJ3 axis also dysregulates mitochondrial dynamics, resulting in fewer, short, and punctate organelles. Consistently, in high miR-27a-/low FOXJ3-expressing cells, mitochondria are functionally characterized by lower superoxide production, respiration capacity, and membrane potential, as evaluated by OCR assays and confocal microscopy. The analysis of a mouse xenograft model confirmed FOXJ3 as a target and suggested that the miR-27a/FOXJ3 axis affects mitochondrial abundance in vivo. A survey of the TCGA-COADREAD dataset supported the inverse relationship of FOXJ3 with miR-27a and reinforced cellular component organization or biogenesis as the most affected pathway. The miR-27a/FOXJ3 axis acts as a central hub in regulating mitochondrial homeostasis. Its discovery paves the way for new therapeutic strategies aimed at restraining tumor growth by targeting mitochondrial activities.

7SK Acts as an Anti-tumor Factor in Tongue Squamous Cell Carcinoma

Increasing evidence has shown the mechanistic insights about non-coding RNA 7SK in controlling the transcription. However, the biological function and mechanism of 7SK in cancer are largely unclear. Here, we show that 7SK is down-regulated in human tongue squamous carcinoma (TSCC) and acts as a TSCC suppressor through multiple cell-based assays including a migration assay and a xenograft mouse model. The expression level of 7SK was negatively correlated with the size of tumors in the 73 in-house collected TSCC patients. Through combined analysis of 7SK knockdown of RNA-Seq and available published 7SK ChIRP-seq data, we identified 27 of 7SK-regulated genes that were involved in tumor regulation and whose upstream regulatory regions were bound by 7SK. Motif analysis showed that the regulatory sequences of these genes were enriched for transcription factors FOXJ3 and THRA, suggesting a potential involvement of FOXJ3 and THRA in 7SK-regulated genes. Interestingly, the augmented level of FOXJ3 in TSCC patients and previous reports on THRA in other cancers have suggested that these two factors may promote TSCC progression. In support of this idea, we found that 21 out of 27 aforementioned 7SK-associated genes were regulated by FOXJ3 and THRA, and 12 of them were oppositely regulated by 7SK and FOXJ3/THRA. We also found that FOXJ3 and THRA dramatically promoted migration in SCC15 cells. Collectively, we identified 7SK as an antitumor factor and suggested a potential involvement of FOXJ3 and THRA in 7SK-mediated TSCC progression.