Novel mechanistic targets of forkhead box Q1 transcription factor in human breast cancer cells

The transcription factor FOXQ1 in cancer

FOXQ1 is a member of the large forkhead box (FOX) family of transcription factors that is involved in all aspects of mammalian development, physiology, and pathobiology. FOXQ1 has emerged as a major regulator of epithelial-to-mesenchymal transition and tumour metastasis in cancers, especially carcinomas of the digestive tract. Accordingly, FOXQ1 induction is recognised as an independent prognostic factor for worse overall survival in several types of cancer, including gastric and colorectal cancer. In this review article, I summarise new evidence on the role of FOXQ1 in cancer, with a focus on molecular mechanisms that control FOXQ1 levels and the regulation of FOXQ1 target genes. Unravelling the functions of FOXQ1 has the potential to facilitate the development of targeted treatments for metastatic cancers.

The Role of MicroRNA-124-3p in Breast Cancer Stem Cell Inhibition by Benzyl Isothiocyanate

PURPOSE

We have shown previously that benzyl isothiocyanate (BITC) derived from cruciferous vegetables inhibits self-renewal of breast cancer stem-like cells (bCSC). The current study provides insights into the mechanism of bCSC inhibition by BITC.

METHODS

Quantitative real time-polymerase chain reaction and western blot analysis were performed to detect microRNAs (miRNAs) and Forkhead box Q1 (FoxQ1) protein expression, respectively. The bCSC were characterized by aldehyde dehydrogenase 1 activity and flow cytometric analysis of CD49f high/CD133high fraction.

RESULTS

BITC treatment resulted in induction of miR-124-3p expression in MDA-MB-231 and MCF-7 cells. miR-124-3p did not affect BITC-mediated inhibition of cell migration or cell proliferation but it significantly regulated bCSC in response to BITC. We also found that miR-124-3p directly targets the 3'untranslated regions (UTR) of FoxQ1 and negatively regulates its expression. The BITC-mediated inhibition of bCSC was partially attenuated by miR-124-3p inhibitor.

CONCLUSIONS

These findings indicate that miR-124-3p plays an important role in BITC-mediated inhibition of bCSC.

The role of transcription factor FOXA1/C2/M1/O3/P1/Q1 in breast cancer

Breast cancer is a common malignancy with the highest mortality rate among women worldwide. Its incidence is on the rise year after year, accounting for more than one-tenth of new cancers worldwide. Increasing evidence suggests that forkhead box (FOX) transcription factors play an important role in the occurrence and development of breast cancer. However, little is known about the relationship between the expression, prognostic value, function, and immune infiltration of FOX transcription factors in tumor microenvironment. We used bioinformatics to investigate expression and function of FOX factor in breast cancer. Our results revealed the expression levels of FOXA1 and FOXM1 were significantly higher in breast cancer tissues than in normal tissues. The high expression of mRNA in FOXA1 (P < .05), FOXM1 (P < .01), and FOXP1 (P < .05) groups was related to tumor stage. Survival analysis results showed that increased FOXP1 mRNA levels were significantly associated with overall survival (OS), recurrence-free survival (RFS), and distant metastasis-free survival (DMFS) in all patients with breast cancer (P < .05). Patients with the FOXA1 high-expression group had better RFS and DMFS than the low-expression group (P < .05), while patients with FOXM1 high-expression group had worse RFS, OS, and DMFS than the low-expression group (P < .05). Meanwhile, mutation analysis showed that genetic alterations in FOX transcription factors were significantly associated with shorter OS and progression-free survival (P < .05), but not with disease-free survival (P = .710) in patients with breast cancer. FOXP1, FOXA1, and FOXM1 may be used as potential biomarkers to predict the prognosis of patients with breast cancer. Functional enrichment indicated that FOX was mainly involved in cell division, cell senescence, cell cycle, and prolactin signaling pathway. In patients with breast cancer, FOXC2 expression was negatively correlated with the infiltration of B cells and positively correlated with the infiltration of neutrophils and dendritic cells. However, FOXM1 was negatively correlated with the infiltration of CD8 + T cells and macrophages and positively correlated with the infiltration of neutrophils and dendritic cells. These findings provided novel insights into the screening of prognostic biomarkers of the FOX family in breast cancer and laid a foundation for further research on the immune infiltration of the FOX transcription factor family members in tumors.

FOXQ1 inhibits breast cancer ferroptosis and progression via the circ_0000643/miR-153/SLC7A11 axis

Dysregulation of ferroptosis is involved in breast cancer progression and therapeutic responses. Inducing ferroptosis can be a potential therapeutic strategy for breast cancer treatment. Forkhead box Q1 (FOXQ1) is an oncogenic transcription factor that highly expressed and related with poor outcomes in various tumors. However, the specific effects of FOXQ1 on ferroptosis in breast cancer is unclear. In this study, we intended to explore the functions and potential mechanisms of FOXQ1 in breast cancer ferroptosis. By CCK-8, colony formation, wound healing, transwell and ferroptosis related assays, we explored the functions of FOXQ1 in breast cancer ferroptosis and progression. Through bioinformatics analysis of public database, luciferase reporter assay, RIP and ChIP assay, we investigated the potential mechanisms of FOXQ1 in breast cancer ferroptosis and progression. We found that FOXQ1 was overexpressed in breast cancer and associated with worse survival. Additionally, inhibition of FOXQ1 suppressed breast cancer ferroptosis and progression. Mechanically, we confirmed that FOXQ1 could bind to the promoter of circ_0000643 host gene to increase the levels of circ_0000643, which could sponge miR-153 and enhance the expression of SLC7A11, leading to reduced cell ferroptosis in breast cancer cells. Targeting the FOXQ1/circ_0000643/miR-153/SLC7A11 axis could be a promising strategy in breast cancer treatment.

Forkhead Box Q1 is a novel regulator of autophagy in breast cancer cells

Forkhead Box Q1 (FoxQ1) transcription factor is overexpressed in luminal-type and basal-type human breast cancers when compared to normal mammary tissue. This transcription factor is best known for its role in promotion of breast cancer stem-like cells and epithelial to mesenchymal transition. The present study documents a novel function of FoxQ1 in breast cancer cells. Overexpression of FoxQ1 in basal-like SUM159 cells and luminal-type MCF-7 cells resulted in increased conversion of microtubule-associated protein light chain 3 beta-I (LC3B-I) to LC3B-II, which is a hallmark of autophagy. Autophagy induction by FoxQ1 overexpression was confirmed by visualization of LC3B puncta as well as by transmission electron microscopy. Expression profiling for genes implicated in autophagy regulation revealed upregulation of many genes, including ATG4B, ATG16L1, CTSS, CXCR4 and so forth but downregulation of BCL2L1, DRAM1, TNF, ULK2 and so forth by FoxQ1 overexpression in SUM159 cells. Western blot analysis confirmed upregulation of ATG4B and CXCR4 proteins by FoxQ1 overexpression in both SUM159 and MCF-7 cells. Chromatin immunoprecipitation assay revealed recruitment of FoxQ1 at the promoter of ATG4B. Pharmacological inhibition of ATG4B using S130 significantly increased apoptosis induction by DOX in empty vector transfected as well as FoxQ1 overexpressing SUM159 and MCF-7 cells but this effect was statistically significantly lowered by FoxQ1 overexpression indicating the protective role of FoxQ1 on apoptosis. Treatment of SUM159 cells with S130 and DOX enhanced LC3B-II level in both empty vector transfected cells and FoxQ1 overexpressing SUM159 cells but not in FoxQ1 overexpressing MCF-7 cells. In conclusion, FoxQ1 is a novel regulator of autophagy.

Monocarboxylate transporter 1 is a novel target for breast cancer stem like-cell inhibition by diallyl trisulfide

Diallyl trisulfide (DATS) is a promising small molecule phytochemical that exhibits in vitro and in vivo activity in multiple preclinical solid tumor models including breast cancer, but the underlying mechanism is not fully understood. We have shown previously that forkhead box Q1 (FoxQ1) transcription factor is a novel target for breast cancer stem-like cells (bCSC) inhibition by DATS. Analysis of the breast TCGA (The Cancer Genome Atlas) data revealed that FoxQ1 expression was positively associated with that of SLC16A1/monocarboxylate transporter 1 (MCT1). Western blot analysis confirmed increased expression of MCT1 protein in SUM159 (basal-like) and MCF-7 cells (luminal-type) stably transfected to overexpress FoxQ1. Furthermore, FoxQ1 was recruited to the promoter of SLC16A1/MCT1. Treatment of SUM159 and MCF-7 cell lines with DATS resulted in suppression of MCT1 protein level that was accompanied by a decrease in intracellular and secreted levels of lactate. Overexpression or knockdown of MCT1 protein failed to alter DATS-mediated inhibition of colony formation or cell migration when compared to corresponding control cells. On the other hand, overexpression of MCT1 protein conferred partial but statistically significant protection against DATS-mediated inhibition of bCSC fraction (CD49f^high /CD44^high and aldehyde dehydrogenase 1 activity). The size of the mammospheres was relatively smaller in the DATS-treated group compared to control group. Inhibition of bCSC upon DATS treatment was augmented by knockdown of the MCT1 protein. In conclusion, the present study reveals that MCT1 is a novel target for bCSC inhibition by DATS treatment.

The FoxQ1 transcription factor is a novel regulator of electron transport chain complex I subunits in human breast cancer cells

The FoxQ1 is an oncogenic transcription factor that is overexpressed in basal-like and luminal-type human breast cancers when compared to the normal mammary tissue. The FoxQ1 is implicated in mammary tumor progression. However, the mechanism by which FoxQ1 promotes mammary tumorigenesis is not fully understood. In this study, we present experimental evidence for a novel function of FoxQ1 in the regulation of complex I activity of the electron transport chain. The RNA-seq data from FoxQ1 overexpressing basal-like SUM159 cells revealed a statistically significant increase in the expression of complex I subunits NDUFS1 and NDUFS2 when compared to the empty vector (EV) transfected control cells. Consistent with these results, the basal and ATP-linked oxygen consumption rates were significantly increased by FoxQ1 overexpression in SUM159 and luminal-type MCF-7 cells. The FoxQ1 overexpression in both cell lines resulted in increased intracellular levels of pyruvate, lactate, and ATP that was associated with overexpression of pyruvate dehydrogenase and pyruvate carboxylase proteins. Activity and assembly of complex I were significantly enhanced by FoxQ1 overexpression in SUM159 and MCF-7 cells that correlated with increased mRNA and/or protein levels of complex I subunits NDUFS1, NDUFS2, NDUFV1, and NDUFV2. The chromatin immunoprecipitation assay revealed the recruitment of FoxQ1 at the promoters of both NDUFS1 and NDUFV1. The cell proliferation of SUM159 and MCF-7 cells was increased significantly by overexpression of NDUFS1 as well as NDUFV1 proteins. In conclusion, we propose that increased complex I-linked oxidative phosphorylation is partly responsible for oncogenic role of FoxQ1 at least in human breast cancer cells.

Tepoxalin increases chemotherapy efficacy in drug-resistant breast cancer cells overexpressing the multidrug transporter gene ABCB1

•

The COX-2 encoding gene PTGS2 is up-regulated upon ABCB1 overexpression in mammary epithelial cells.

•

The 5-LOX, COX-1/2 inhibitor tepoxalin plus chemotherapy improves treatment efficacy in ABCB1-expressing cells.

•

Tepoxalin reduces chemotherapy-induced selection for drug-resistant ABCB1-expressing cells.

Effective cancer chemotherapy treatment requires both therapy delivery and retention by malignant cells. Cancer cell overexpression of the multidrug transmembrane transporter gene ABCB1 (MDR1, multi-drug resistance protein 1) thwarts therapy retention, leading to a drug-resistant phenotype. We explored the phenotypic impact of ABCB1 overexpression in normal human mammary epithelial cells (HMECs) via acute adenoviral delivery and in breast cancer cell lines with stable integration of inducible ABCB1 expression. One hundred sixty-two genes were differentially expressed between ABCB1-expressing and GFP-expressing HMECs, including the gene encoding the cyclooxygenase-2 protein, PTGS2. Several breast cancer cell lines with inducible ABCB1 expression demonstrated sensitivity to the 5-lipoxygenase, cyclooxygenase-1/2 inhibitor tepoxalin in two-dimensional drug response assays, and combination treatment of tepoxalin either with chemotherapies or with histone deacetylase (HDAC) inhibitors improved therapeutic efficacy in these lines. Moreover, selection for the ABCB1-expressing cell population was reduced in three-dimensional co-cultures of ABCB1-expressing and GFP-expressing cells when chemotherapy was given in combination with tepoxalin. Further study is warranted to ascertain the clinical potential of tepoxalin, an FDA-approved therapeutic for use in domesticated mammals, to restore chemosensitivity and improve drug response in patients with ABCB1-overexpressing drug-resistant breast cancers.

The Role of Forkhead Box Q1 Transcription Factor in Anticancer Effects of Withaferin A in Breast Cancer

Elimination of both rapidly dividing epithelial mammary cancer cells as well as breast cancer stem-like cells (bCSC) is essential for maximizing antitumor response. Withaferin A (WA), a small molecule derived from a medicinal plant (Withania somnifera), is highly effective in reducing burden and/or incidence of breast cancer in vivo in various preclinical models. We have shown previously that suppression of breast cancer incidence by WA administration in a rat model is associated with a decrease in self-renewal of bCSC but the underlying mechanism is still elusive. This study investigated the role of forkhead box Q1 (FoxQ1) transcription factor in antitumor responses to WA. Exposure of MDA-MB-231 and SUM159 cells to WA resulted in downregulation of protein and mRNA levels of FoxQ1 as well as inhibition of its transcriptional activity. FoxQ1 overexpression in SUM159 and MCF-7 cells resulted in a marked protection against WA-mediated inhibition of bCSC as judged by flow cytometric analysis of CD49f^high population and mammosphere assay. RNA-sequencing analysis revealed upregulation of many bCSC-associated genes by FoxQ1 overexpression in SUM159 cells, including IL8 whose expression was decreased by WA treatment in SUM159 and MCF-7 cells. FoxQ1 was recruited to the promoter of IL8 that was inhibited significantly by WA treatment. On the other hand, WA-mediated inhibition of cell proliferation or migration was not affected by FoxQ1 overexpression. The FoxQ1 overexpression partially attenuated WA-mediated G₂-M phase cell cycle arrest in SUM159 cells only. These results indicate that FoxQ1 is a target of WA for inhibition of bCSC fraction. PREVENTION RELEVANCE: Withaferin A (WA) is highly effective in reducing burden and/or incidence of breast cancer in various preclinical models. However, the mechanism underlying breast cancer prevention by WA is not fully understood. This study shows a role for FoxQ1 in antitumor response to WA.