Amplification-driven BCL6-suppressed cytostasis is mediated by transrepression of FOXO3 and post-translational modifications of FOXO3 in urinary bladder urothelial carcinoma

Abstract

Muscle-invasive urinary bladder urothelial carcinoma (UBUC) is a lethal disease for which effective prognostic markers and potential therapy targets are still lacking. Previous array comparative genomic hybridization identified that 3q27 is frequently amplified in muscle-invasive UBUCs, one candidate proto-oncogene, B-cell CLL/lymphoma 6 (BCL6), mapped to this region. We therefore aimed to explore its downstream targets and physiological roles in UBUC progression.Methods: Specimens from UBUC patients, NOD/SCID mice and several UBUC-derived cell lines were used to perform quantitative RT-PCR, fluorescence in situ hybridization immunohistochemistry, xenograft, gene stable overexpression/knockdown and a series of in vitro experiments.Results: Amplification of the BCL6 gene lead to upregulation of BCL6 mRNA and protein levels in a substantial set of advanced UBUCs. High BCL6 protein level significantly predicted poor disease-specific and metastasis-free survivals. Knockdown of the BCL6 gene in J82 cells inhibited tumor growth and enhanced apoptosis in the NOD/SCID xenograft model. In vitro experiments demonstrated that BCL6 inhibited cytostasis, induced cell migration, invasion along with alteration of the expression levels of several related regulators. At molecular level, BCL6 inhibited forkhead box O3 (FOXO3) transcription, subsequent translation and upregulation of phosphorylated/inactive FOXO3 through phosphoinositide 3-kinase (PI3K)/AKT serine/threonine kinase (AKT) and/or epidermal growth factor receptor (EGFR)/mitogen-activated protein kinase 1/2 (MAP2K1/2) signaling pathway(s). Two BCL6 binding sites on the proximal promoter region of the FOXO3 gene were confirmed.Conclusion: Overexpression of BCL6 served a poor prognostic factor in UBUC patients. In vivo and in vitro studies suggested that BCL6 functions as an oncogene through direct transrepression of the FOXO3 gene, downregulation and phosphorylation of the FOXO3 protein.

EGFR/FOXO3A/LXR-α Axis Promotes Prostate Cancer Proliferation and Metastasis and Dual-Targeting LXR-α/EGFR Shows Synthetic Lethality

“…Our conclusion is supported by the following lines of evidence: (1) Among 59 tumor TMA samples, the high EGFR staining group is largely associated with the low staining group of LXR-α, and vice versa; (2) Among prostate cell lines tested, there is a general tendency of inversed protein levels between EGFR and FOXO3A. FOXO3A could induce cholesterol regulation and lipid management (52), and be regulated by EGFR (44)(45)(46); (3) EGFR inhibitor Afatinib inhibited p-AKT and increased FOXO3A and LXR-α, as did AKT inhibitor LY294002; (4) The levels of endogenously expressed LXR-α were increased upon FOXO3A transfection, while they were reduced by FOXO3A knockdown; and (5) Overexpression of FOXO3A elevated the level of LXR-α mRNA, and vice versa.…”

“…We found 54 potential transcription factors that may regulate LXR-α ( Figure 3B), including FOXO3A (Forkhead box-containing protein class O3a). Some papers reported that FOXO3A is a transcriptional regulator, which can be regulated by EGFR (44)(45)(46). We therefore measured FOXO3A and EGFR expression in prostate cancer cell lines by IB.…”

SLC14A1 prevents oncometabolite accumulation and recruits HDAC1 to transrepress oncometabolite genes in urothelial carcinoma

“…One specific probe targeting the SLC14A1 transcript was designed for QuantiGene™ Sample Processing Kit, formalin-fixed paraffin-embedded (FFPE) samples (QS0107, ThermoFisher, USA) and QuantiGene™ Plex Assay Kit (QP1013, ThermoFisher) based on the user guides ( Supplementary materials ). Immunohistochemical (IHC) staining was performed on representative tissue sections cut from FFPE tissues at 4-µm thickness as in our previous study 14 by probing specific anti-human antibodies ( Supplementary materials ).…”

A Pan-Cancer Analysis of Transcription Factor Forkhead Box O-3: FOXO3

“…FOXO3, as reported in all the available literature above, played an inhibitory role in CESC [26][27][28]. we also found that FOXO3 was a tumor suppressor gene via inducing cell cycle arrest and apoptosis, and there was no evidence that FOXO3 played a role in promoting the progression of BLCA [29][30][31][32][33][34][35] after reading all the available literature. Therefore, whether FOXO3 at a higher level having a cancer-promoting effect in CESC and BLCA needs our further studies.…”