OVOL2 Maintains the Transcriptional Program of Human Corneal Epithelium by Suppressing Epithelial-to-Mesenchymal Transition.

ヒト角膜上皮分化を規定している新分子を発見－OVOL2は角膜上皮における上皮性恒常維持に関与－. 京都大学プレスリリース. 2016-05-09.In development, embryonic ectoderm differentiates into neuroectoderm and surface ectoderm using poorly understood mechanisms. Here, we show that the transcription factor OVOL2 maintains the transcriptional program of human corneal epithelium cells (CECs), a derivative of the surface ectoderm, and that OVOL2 may regulate the differential transcriptional programs of the two lineages. A functional screen identified OVOL2 as a repressor of mesenchymal genes to maintain CECs. Transduction of OVOL2 with several other transcription factors induced the transcriptional program of CECs in fibroblasts. Moreover, neuroectoderm derivatives were found to express mesenchymal genes, and OVOL2 alone could induce the transcriptional program of CECs in neural progenitors by repressing these genes while activating epithelial genes. Our data suggest that the difference between the transcriptional programs of some neuroectoderm- and surface ectoderm-derivative cells may be regulated in part by a reciprocally repressive mechanism between epithelial and mesenchymal genes, as seen in epithelial-to-mesenchymal transition

Srf destabilizes cellular identity by suppressing cell-type-specific gene expression programs

Multicellular organisms consist of multiple cell types. The identity of these cells is primarily maintained by cell-type-specific gene expression programs; however, mechanisms that suppress these programs are poorly defined. Here we show that serum response factor (Srf), a transcription factor that is activated by various extracellular stimuli, can repress cell-type-specific genes and promote cellular reprogramming to pluripotency. Manipulations that decrease β-actin monomer quantity result in the nuclear accumulation of Mkl1 and the activation of Srf, which downregulate cell-type-specific genes and alter the epigenetics of regulatory regions and chromatin organization. Mice overexpressing Srf exhibit various pathologies including an ulcerative colitis-like symptom and a metaplasia-like phenotype in the pancreas. Our results demonstrate an unexpected function of Srf via a mechanism by which extracellular stimuli actively destabilize cell identity and suggest Srf involvement in a wide range of diseases

Human Pluripotent Stem Cell-Derived Tumor Model Uncovers the Embryonic Stem Cell Signature as a Key Driver in Atypical Teratoid/Rhabdoid Tumor

ヒトiPS細胞を使った小児脳腫瘍の病態解明 --新しい治療標的を同定--. 京都大学プレスリリース. 2019-03-06.Atypical teratoid/rhabdoid tumor (AT/RT), which harbors SMARCB1 mutation and exhibits a characteristic histology of rhabdoid cells, has a poor prognosis because of the lack of effective treatments. Here, we establish human SMARCB1-deficient pluripotent stem cells (hPSCs). SMARCB1-deficient hPSC-derived neural progenitor-like cells (NPLCs) efficiently give rise to brain tumors when transplanted into the mouse brain. Notably, activation of an embryonic stem cell (ESC)-like signature confers a rhabdoid histology in SMARCB1-deficient NPLC-derived tumors and causes a poor prognosis. Consistently, we find the activation of the ESC-like gene expression signature and an ESC-like DNA methylation landscape in clinical specimens of AT/RT. Finally, we identify candidate genes that maintain the activation of the ESC-like signature and the growth of AT/RT cells. Collectively, SMARCB1-deficient hPSCs offer the human models for AT/RT, which uncover the role of the activated ESC-like signature in the poor prognosis and unique histology of AT/RT

Palliative radiotherapy for tumor bleeding in patients with unresectable pancreatic cancer: a single-center retrospective study

Abstract Background Patients with unresectable pancreatic cancer (PC) sometimes experience gastrointestinal bleeding (GIB) due to tumor invasion of the gastrointestinal tract (tumor bleeding); no standard treatment has been established yet for this complication. Palliative radiotherapy (PRT) could be promising, however, there are few reports of PRT for tumor bleeding in patients with unresectable PC. Therefore, we evaluated the outcomes of PRT for tumor bleeding in patients with unresectable PC. Methods We reviewed the medical records of patients with unresectable PC diagnosed at our institution between May 2013 and January 2022, and identified patients with endoscopically confirmed tumor bleeding who had received PRT. PRT was administered at a total dose of 30 Grays (Gy) in 10 fractions, 20 Gy in 5 fractions, or 8 Gy in a single fraction, and the dose selection was left to the discretion of the attending radiation oncologists. Results During the study period, 2562 patients were diagnosed as having unresectable PC at our hospital, of which 225 (8.8%) developed GIB. Among the 225 patients, 63 (2.5%) were diagnosed as having tumor bleeding and 20 (0.8%) received PRT. Hemostasis was achieved in 14 of the 20 patients (70%) who received PRT, and none of these patients developed grade 3 or more adverse events related to the PRT. The median time to hemostasis was 8.5 days (range 7–14 days). The rebleeding rate was 21.4% (3/14). The median hemoglobin level increased significantly (p < 0.001) from 5.9 to 9.1 g/dL, and the median volume of red blood cell transfusion tended (p = 0.052) to decrease, from 1120 mL (range 280–3360 mL) to 280 mL (range 0–5560 mL) following the PRT. The median overall survival (OS) was 52 days (95% confidence interval [CI] 39–317). Of the 14 patients in whom hemostasis was achieved following PRT, chemotherapy could be started/resumed in seven patients (50%), and the median OS in these patients was 260 days (95% CI 76–not evaluable [NE]). Three patients experienced rebleeding (21.4%), on days 16, 22, and 25, after the start of PRT. Conclusion This study showed that PRT is an effective and safe treatment modality for tumor bleeding in patients with unresectable PC

Premature Termination of Reprogramming In Vivo Leads to Cancer Development through Altered Epigenetic Regulation

SummaryCancer is believed to arise primarily through accumulation of genetic mutations. Although induced pluripotent stem cell (iPSC) generation does not require changes in genomic sequence, iPSCs acquire unlimited growth potential, a characteristic shared with cancer cells. Here, we describe a murine system in which reprogramming factor expression in vivo can be controlled temporally with doxycycline (Dox). Notably, transient expression of reprogramming factors in vivo results in tumor development in various tissues consisting of undifferentiated dysplastic cells exhibiting global changes in DNA methylation patterns. The Dox-withdrawn tumors arising in the kidney share a number of characteristics with Wilms tumor, a common pediatric kidney cancer. We also demonstrate that iPSCs derived from Dox-withdrawn kidney tumor cells give rise to nonneoplastic kidney cells in mice, proving that they have not undergone irreversible genetic transformation. These findings suggest that epigenetic regulation associated with iPSC derivation may drive development of particular types of cancer