iPSC-Derived Glioblastoma Cells Have Enhanced Stemness Wnt/β-Catenin Activity Which Is Negatively Regulated by Wnt Antagonist sFRP4

A novel function of the Wnt antagonist secreted frizzled-related protein 4 as a transcriptional regulator of Dickkopf-1, another Wnt antagonist, in glioblastoma cell line U87MG

Wnt/β-catenin pathway dysregulation is associated with glioblastoma multiforme (GBM) pathogenesis and Wnt antagonists are downregulated in GBM. Wnt antagonist secreted frizzled-related protein 4 (sFRP4) has a tissue-specific, anti-metastatic and anti-stemness property. Our lab previously reported that gene silencing of sFRP4 in GBM cell line U87MG increases expression of another Wnt antagonist, Dickkopf-1 (Dkk1) and sFRP4 has a DNA binding ability. These findings in accordance with the nuclear localization of sFRP4 led to our present hypothesis that sFRP4 presumably negatively regulates Dkk1 and it probably interacts with the promoter region of Dkk1. Methylation-specific PCR (MSP), chromatin accessibility real-time PCR (ChART-PCR) assay, chromatin immunoprecipitation (ChIP), and quantitative DNA-protein interaction enzyme-linked immunosorbent assay (qDPI-ELISA) were carried out to test our hypothesis. We demonstrated that sFRP4 overexpression does not alter the methylation status of the Dkk1 promoter region. sFRP4 overexpression inhibits DNA-transcription factor interaction and enables chromatin accessibility to DNase I. Pertinently, sFRP4 has strong putative binding sites in the Dkk1 promoter region and its overexpression disrupts its interaction with the Dkk1 promoter. Interestingly, sFRP4 has the strongest affinity towards the -282 to +118 bp region. Downregulation of Dkk1 by overexpressed sFRP4 occurs by inhibition of the direct interaction of sFRP4 with the promoter region of Dkk1 as observed with low concentrations of sFRP4. We report for the first time a novel function of the Wnt antagonist sFRP4 acting as a transcription factor for another Wnt antagonist Dkk1, throwing open a new vista in the complex interplay between different antagonists of the Wnt pathway.

Decoding cancer etiology with cellular reprogramming

Cancer research remains clinically unmet in many areas due to limited access to patient samples and the lack of reliable model systems that truly reflect human cancer biology. The emergence of patient-derived induced pluripotent stem cells and engineered human pluripotent stem cells (hPSCs) has helped overcome these challenges, offering a versatile alternative platform for advancing cancer research. These hPSCs are already proving to be valuable models for studying specific cancer driver mutations, offering insights into cancer origins, pathogenesis, tumor heterogeneity, clonal evolution, and facilitating drug discovery and testing. This article reviews recent progress in utilizing hPSCs for clinically relevant cancer models and highlights efforts to deepen our understanding of fundamental cancer biology.

Genome-Wide Analysis Identifies Nuclear Factor 1C as a Novel Transcription Factor and Potential Therapeutic Target in SCLC

INTRODUCTION

Recent insights regarding mechanisms mediating stemness, heterogeneity, and metastatic potential of lung cancers have yet to be fully translated to effective regimens for the treatment of these malignancies. This study sought to identify novel targets for lung cancer therapy.

METHODS

Transcriptomes and DNA methylomes of 14 SCLC and 10 NSCLC lines were compared with normal human small airway epithelial cells (SAECs) and induced pluripotent stem cell (iPSC) clones derived from SAEC. SCLC lines, lung iPSC (Lu-iPSC), and SAEC were further evaluated by DNase I hypersensitive site sequencing (DHS-seq). Changes in chromatin accessibility and depths of transcription factor (TF) footprints were quantified using Bivariate analysis of Genomic Footprint. Standard techniques were used to evaluate growth, tumorigenicity, and changes in transcriptomes and glucose metabolism of SCLC cells after NFIC knockdown and to evaluate NFIC expression in SCLC cells after exposure to BET inhibitors.

RESULTS

Considerable commonality of transcriptomes and DNA methylomes was observed between Lu-iPSC and SCLC; however, this analysis was uninformative regarding pathways unique to lung cancer. Linking results of DHS-seq to RNA sequencing enabled identification of networks not previously associated with SCLC. When combined with footprint depth, NFIC, a transcription factor not previously associated with SCLC, had the highest score of occupancy at open chromatin sites. Knockdown of NFIC impaired glucose metabolism, decreased stemness, and inhibited growth of SCLC cells in vitro and in vivo. ChIP-seq analysis identified numerous sites occupied by BRD4 in the NFIC promoter region. Knockdown of BRD4 or treatment with Bromodomain and extra-terminal domain (BET) inhibitors (BETis) markedly reduced NFIC expression in SCLC cells and SCLC PDX models. Approximately 8% of genes down-regulated by BETi treatment were repressed by NFIC knockdown in SCLC, whereas 34% of genes repressed after NFIC knockdown were also down-regulated in SCLC cells after BETi treatment.

CONCLUSIONS

NFIC is a key TF and possible mediator of transcriptional regulation by BET family proteins in SCLC. Our findings highlight the potential of genome-wide chromatin accessibility analysis for elucidating mechanisms of pulmonary carcinogenesis and identifying novel targets for lung cancer therapy.

Interconversion of Cancer Cells and Induced Pluripotent Stem Cells

Cancer cells, especially cancer stem cells (CSCs), share many molecular features with induced pluripotent stem cells (iPSCs) that enable the derivation of induced pluripotent cancer cells by reprogramming malignant cells. Conversely, normal iPSCs can be converted into cancer stem-like cells with the help of tumor microenvironment components and genetic manipulation. These CSC models can be utilized in oncogenic initiation and progression studies, understanding drug resistance, and developing novel therapeutic strategies. This review summarizes the role of pluripotency factors in the stemness, tumorigenicity, and therapeutic resistance of cancer cells. Different methods to obtain iPSC-derived CSC models are described with an emphasis on exposure-based approaches. Culture in cancer cell-conditioned media or cocultures with cancer cells can convert normal iPSCs into cancer stem-like cells, aiding the examination of processes of oncogenesis. We further explored the potential of reprogramming cancer cells into cancer-iPSCs for mechanistic studies and cancer dependencies. The contributions of genetic, epigenetic, and tumor microenvironment factors can be evaluated using these models. Overall, integrating iPSC technology into cancer stem cell research holds significant promise for advancing our knowledge of cancer biology and accelerating the development of innovative and tailored therapeutic interventions.