Probes for FOXO1

Gastric cancer (GC) is a major of cause of cancer-related death and is characterized by its heterogeneity and molecular complexity. FOXO1 is a transcription factor that plays a key role in GC growth and metastasis. However, the implication of FOXO1 in GC cell stemness has been elusive. This study, for the first time, demonstrates that FOXO1 regulates GC cell stemness in association with LGR5. FOXO1 expression was significantly lower in GC tumorsphere cells than in adherent GC cells. FOXO1 silencing and overexpression promoted and inhibited the tumorsphere formation capacity of GC cells, respectively. Additionally, there was an inverse correlation between FOXO1 and GC stem cell marker LGR5 in human GC specimens. Further in vitro and in vivo experiments showed that negative crosstalk between these two molecules exists and that LGR5 silencing reversed the FOXO1 shRNA-induced tumorsphere formation even without FOXO1 restoration. Taken together, our results suggest that FOXO1 inhibits the self-renewal capacity of GC cells through interaction with LGR5. Thus, FOXO1/LGR5 signaling pathway may provide a novel targeted therapy for GC.

Successful embryo implantation requires a receptive endometrium. Poor uterine receptivity can account for implantation failure in women who experience recurrent pregnancy loss or multiple rounds of unsuccessful in vitro fertilization cycles. Here, we demonstrate that the transcription factor Forkhead Box O1 (FOXO1) is a critical regulator of endometrial receptivity in vivo. Uterine ablation of Foxo1 using the progesterone receptor Cre (PgrCre) mouse model resulted in infertility due to altered epithelial cell polarity and apoptosis, preventing the embryo from penetrating the luminal epithelium. Analysis of the uterine transcriptome after Foxo1 ablation identified alterations in gene expression for transcripts involved in the activation of cell invasion, molecular transport, apoptosis, β-catenin (CTNNB1) signaling pathway, and an increase in PGR signaling. The increase of PGR signaling was due to PGR expression being retained in the uterine epithelium during the window of receptivity. Constitutive expression of epithelial PGR during this receptive period inhibited expression of FOXO1 in the nucleus of the uterine epithelium. The reciprocal expression of PGR and FOXO1 was conserved in human endometrial samples during the proliferative and secretory phase. This demonstrates that expression of FOXO1 and the loss of PGR during the window of receptivity are interrelated and critical for embryo implantation.

In the central nervous system, endothelial cells (ECs) and pericytes (PCs) of blood vessel walls cooperatively form a physical and chemical barrier to maintain neural homeostasis. However, in diabetic retinopathy (DR), the loss of PCs from vessel walls is assumed to cause breakdown of the blood-retina barrier (BRB) and subsequent vision-threatening vascular dysfunctions. Nonetheless, the lack of adequate DR animal models has precluded disease understanding and drug discovery. Here, by using an anti-PDGFRβ antibody, we show that transient inhibition of the PC recruitment to developing retinal vessels sustained EC-PC dissociations and BRB breakdown in adult mouse retinas, reproducing characteristic features of DR such as hyperpermeability, hypoperfusion, and neoangiogenesis. Notably, PC depletion directly induced inflammatory responses in ECs and perivascular infiltration of macrophages, whereby macrophage-derived VEGF and placental growth factor (PlGF) activated VEGFR1 in macrophages and VEGFR2 in ECs. Moreover, angiopoietin-2 (Angpt2) upregulation and Tie1 downregulation activated FOXO1 in PC-free ECs locally at the leaky aneurysms. This cycle of vessel damage was shut down by simultaneously blocking VEGF, PlGF, and Angpt2, thus restoring the BRB integrity. Together, our model provides new opportunities for identifying the sequential events triggered by PC deficiency, not only in DR, but also in various neurological disorders.