Biology subjects

Bondoc, A.

Publications and source records attributed to Bondoc, A..

5 recordsLinked to original sources

bioRxiv2025

Primitive Hepatoblasts Driving Early Liver Development

The embryonic development of the liver is initiated by the emergence of hepatoblasts, originating from the ventral foregut endoderm adjacent to the heart. Here, we identify and characterize a previously unrecognized population of early hepatoblasts at the ventroposterior part of the emerging liver bud, traced from Cdx2-positive endoderm progenitors, which we term primitive hepatoblasts. Mouse and human single-cell transcriptomics reveals the expression of both canonical hepatoblast markers TBX3, FGB, and KRT8/18 and primitive-specific mesenchymal markers ID3, VIM, and GATA4. Lineage tracing revealed the notable contribution up to 12.6% of LIV2+ hepatoblasts at E11.5 but diminishes in late fetal and postnatal development. Epigenetic and functional perturbation studies further uncover that primitive hepatoblast emergence is primed by WNT-suppression on RA-permissive CDX2+FOXA2+ progenitors. Furthermore, human pluripotent stem cell-derived primitive hepatoblast-like cells secrete pleiotrophin and midkine to amplify hepatoblast populations and develop epithelial-mesenchymal hybrid tissues in vivo. Our results provide a new framework for understanding lineage heterogeneity during early hepatogenesis and offer revised insights into strategies to model normal and abnormal liver development.

developmental biology↗

bioRxiv2025

Efficacy of DNA Methyltransferase Inhibitor Immune Priming Therapy in Combination with PD-1 Inhibitors to Treat High-Risk Pediatric Brain Tumors

BackgroundDespite intensive therapies, outcomes for high-risk pediatric brain tumors (PBTs) remain dismal, prompting the search for novel treatments. DNA methyltransferase inhibitors (DNMTi) have been shown to prime tumors to improve response to checkpoint inhibition. The aim of this study was to investigate the potential of decitabine (DAC), in combination with a PD-1 inhibitor, to improve survival in pediatric high-risk brain tumor models. MethodsAnalysis of human PBT datasets was performed to determine gene expression levels of immune cell associated markers. Tumor response to DAC, with or without a PD-1 inhibitor, was tested in murine models representing H3-wildtype diffuse intrinsic pontine glioma (DIPG), H3K27-mutant diffuse midline glioma (DMG), atypical teratoid rhabdoid tumor (ATRT), and medulloblastoma (MB). CyTOF analysis of allograft tumors was performed to characterize changes within the tumor microenvironment. ResultsAnalysis of PBT subtypes revealed heterogeneous expression of immune cell markers, checkpoint receptors, and MHC molecules. DAC treatment decreased DNA methylation and increased neoantigen expression in human and mouse tumor cells. DAC alone or in combination with a PD-1 inhibitor resulted in prolonged survival in syngeneic mouse models of DIPG and ATRT but not DMG and MB models. CyTOF analysis of mouse tumors revealed changes in local immune cell infiltration upon combination treatment. ConclusionsDAC in combination with a PD-1 inhibitor can alter the immune microenvironment in mouse tumor models. Changes were observed in H3-wildtype DIPG and ATRT models, suggesting that certain tumor subtypes may respond to checkpoint blockade after immune augmentation with DNMTi. Key PointsO_LIPBTs show heterogenous expression of immune cell infiltrates C_LIO_LIDAC or DAC plus a PD-1 inhibitor shows extension of survival in H3-wildtype DIPG and ATRT mouse models C_LIO_LIMyeloid-derived suppressor cell abundance could be a major contributing factor to treatment response C_LI Importance of the StudyChildren with high-risk PBTs face dismal outcomes. Immune checkpoint inhibitor (ICI) successes have been demonstrated in a variety of adult malignancies; however, such beneficial outcomes have not been realized in PBTs. Here we investigate single and combination treatment of DNMTi and PD-1 checkpoint inhibition in syngeneic mouse models of high-risk PBTs. Our results suggest that some H3-wildtype DIPG and ATRT tumor types may be responsive to checkpoint therapy post immunomodulation and warrant further investigation.

immunology↗

bioRxiv2024

Self-Assembled Generation of Multi-zonal Liver Organoids from Human Pluripotent Stem Cells

Distinct hepatocyte subpopulations are spatially segregated along the portal-central axis and critical to understanding metabolic homeostasis and liver injury. While several bioactive molecules have been described to play a role in directing zonal fates, including ascorbate and bilirubin, in vitro replication of zonal liver architecture has not been achieved to date. In order to evaluate hepatic zonal polarity, we developed a self-assembling zone-specific liver organoid culture by co-culturing ascorbate and bilirubin enriched hepatic progenitors derived from human induced pluripotent stem cells. We found that preconditioned hepatocyte-like cells exhibited zone-specific functions associated with urea cycle, glutathione synthesis and glutamate synthesis. Single nucleus RNA sequencing analysis of these zonally patterned organoids identifies hepatoblast differentiation trajectory that mimics periportal-, interzonal-, and pericentral human hepatocytes. Epigenetic and transcriptomic analysis showed that zonal identity is orchestrated by ascorbate or bilirubin dependent binding of histone acetyltransferase p300 (EP300) to methylcytosine dioxygenase TET1 or hypoxia-inducible factor 1-alpha (HIF1). Transplantation of the self-assembled zonally patterned human organoids improved survival of immunodeficient rats who underwent bile duct ligation by ameliorating the hyperammonemia and hyperbilirubinemia. Overall, this multi-zonal organoid system serves as an in vitro human model to better recapitulate hepatic architecture relevant to liver development and disease.

bioengineering↗

bioRxiv2021

A Developmentally Prometastatic Niche to Hepatoblastoma in Neonatal Liver mediated by the Cxcl1/Cxcr2 Axis

Background and RationaleHepatoblastoma (HB) is the most common pediatric liver cancer. Its predominant occurrence in very young children led us to investigating whether the neonatal liver provides a protumorigenic niche to HB development. MethodsHB development was compared between orthotopic transplantation models established in postnatal day 5 and 60 mice (P5Tx and P60Tx models). Single-cell RNA-sequencing was performed using tumor and liver tissues from both models and the top candidate cell types and genes identified are investigated for their roles in HB cell growth, migration, and survival. ResultsWe found that various HB cell lines including HepG2 cells were consistently and considerably more tumorigenic and metastatic in the P5Tx model than in the P60Tx models. Sc-RNAseq of the P5Tx and P60Tx HepG2 models revealed that the P5Tx tumor was more hypoxic and had a larger number of activated hepatic stellate cells (aHSCs) in the tumor-surrounding liver which express significantly higher levels of Cxcl1 than those from the P60Tx model. We found these differences were developmentally present in normal P5 and P60 liver. We showed that the Cxcl1/Cxcr2 axis mediated HB cell migration and was critical to HB cell survival under hypoxia. Treating HepG2 P60Tx model with recombinant CXCL1 protein induced intrahepatic and pulmonary metastasis and CXCR2 knockout in HepG2 cells abolished their metastatic potential in the P5Tx model. Lastly, we showed that in metastatic HB patient tumors there was a similar larger population of aHSCs in the tumor-surrounding liver than in localized tumors, and tumor hypoxia was uniquely associated with HB patient prognosis among pediatric cancers. ConclusionWe demonstrated that the neonatal liver provides a prometastatic niche to HB development via the Cxcl1/Cxcr2 axis.

cancer biology↗

bioRxiv2021

Isoform-specific functions of Numb in breast cancer progression, metastasis and proteome remodeling.

Deregulated alternative splicing of the endocytic adaptor NUMB resulting in high expression of Exon9in (exon 9-containing) isoforms has been reported in several cancer types. However, the role of Numb isoform expression in tumor progression and the underlying mechanisms remain elusive. Here, we report greater exon 9 inclusion in multiple cancer types including all subtypes of breast cancer, and correlation of higher exon 9 inclusion in patients with worse prognosis. Deletion of Exon9in in breast cancer cells leads to reduced cell growth and a significant decrease of lung metastasis in orthotopic xenograft experiments. Quantitative mass spectrometry revealed downregulation of proteins involved in EMT and ECM organization and remodeling of the endocytic protein network in cells lacking the Exon9in Numb isoforms. Exon 9 deletion also results in reduced surface levels of ITG{beta}5, and downstream signaling to ERK and SRC, consistent with enhance lysosomal targeting mediated by the remaining Exon9sk (exon 9 skipping) Numb isoforms. SIGNIFICANCEExpression of NUMB Exon9in protein isoforms correlate with worse progression free survival, particularly in breast cancer. Our findings also reveal that Exon9in isoforms promote breast cancer progression by relieving Numb mediated down regulation of integrins and implicate Numb alternative splicing as a progression factor in multiple cancer types.

cancer biology↗