Biology subjects

Phuong, D. J.

Publications and source records attributed to Phuong, D. J..

7 recordsLinked to original sources

bioRxiv2026

Cross-species analysis links cell-cell communication rewiring to NOTCH2 during serous endometrial carcinogenesis

Cell-cell interactions shape the fate of mutant cells during cancer initiation but how these interactions evolve during progression to pathologically recognizable lesions remain poorly understood. Here, we investigated cell-cell communication during serous endometrial carcinoma (SEC; also known as uterine serous carcinoma) development using a lineage-traceable mouse model and cross-species analyses of the mouse and human neoplastic endometrium. In mice, the early, pre-dysplastic stage was marked by a global decrease in inferred cell-cell interactions, followed by extensive communication network rewiring during neoplastic progression. Pathway-specific analysis revealed a similar pattern for NOTCH signaling, with NOTCH2 emerging as the dominant NOTCH receptor in Trp53/Rb1-mutant immature epithelial cells. Functionally, NOTCH2 promoted the outgrowth of more proliferative mutant organoids. Cross-species transcriptomic analysis identified conserved immature epithelial states in mouse and human neoplastic endometrial epithelium. In human tissues, NOTCH2 was overexpressed in serous endometrial intraepithelial carcinoma, a precursor of SEC, and in overt SEC. Furthermore, elevated NOTCH2 expression was associated with poor patient survival. These findings link cell-cell communication rewiring during experimental SEC development to conserved neoplastic epithelial states and identify NOTCH2 as an early marker and a potential target of disease interception.

cancer biology↗

bioRxiv2025

Embryonic Stem Cell-Specific Responses to DNA Replication Stress

Genome maintenance is of the utmost importance in stem cells, as mutations can be propagated and cause defects in derivative tissues. Many stem cell types display low mutation rates, with embryonic stem cells (ESCs) being a notable example. The bases for this property are unclear but may be achieved by optimization of various processes including high-fidelity DNA repair, cell cycle checkpoint controls, and hypersensitivity to genotoxic insults that trigger cell death. Here, we investigate the mechanisms underlying the unique responses of mouse ESCs (mESCs) to replication stress (RS) using an array of small molecule inhibitors and genotoxins. We find that whereas mESCs survive under acute RS in an ATR- and CHK1-dependent manner similar to somatic cells, they lack a strong G2/M checkpoint and fail to repair DNA crosslinks in the absence of ATR signaling. Despite the lack of a strong G2/M checkpoint, mESCs maintain a spindle assembly checkpoint (SAC). We posit that mESCs preferentially repair DNA crosslinks in S phase via homology-directed mechanisms, and cells that fail to complete repair before mitosis undergo mitotic catastrophe and cell death. These findings shed light on mutation avoidance mechanisms in ESCs that may extend to other stem cell types.

cell biology↗

bioRxiv2025

Gene combinations driving transformation of tubal epithelial organoids and differential sensitivity to high-grade serous ovarian carcinoma drugs

High-grade serous ovarian carcinoma (HGSC) is the sixth leading cause of cancer-related death among women. Many cases arise from the Fallopian tubal epithelium (TE), exhibit numerous mutations, and present heterogenous pathological features. However, the contribution of specific mutation combinations to cellular transformation, pathological phenotype and chemotherapeutic response remains poorly understood. Here, we used a Trp53-deficient mouse TE-derived organoid platform to perform combinatorial CRISPR mutagenesis of 20 candidate HGSC driver genes. Mutations in Nf1, Cdkn2a and Map2k4 were most frequently observed in transformed organoids. Upon transplantation into mice, those containing Map2k4 mutations predominantly gave rise to papillary-glandular histology, whereas those containing Nf1 mutations formed more mesenchymal-like carcinomas. Transcriptomic analysis revealed that Nf1-mutant tumors of all pathological phenotypes overexpressed the long non-coding RNA Pvt1, a marker associated with poor prognosis in HGSC patients. Map2k4-mutant organoids were more sensitive to paclitaxel and niraparib, while Nf1-mutant combinations responded better to trametinib. Notably, the removal of Rho kinase inhibitor (ROCKi) reduced trametinib sensitivity in both Map2k4- and Nf1-mutant organoids, underscoring the importance of culture conditions and potential antagonistic drug interactions in organoid-based drug screens. Collectively, our results demonstrate that TE-derived organoids coupled with combinatorial CRISPR mutagenesis provide a powerful system to unravel the genetic and phenotypic complexity of HGSC. In particular, we found that Map2k4 functions as a tumor suppressor that shapes distinct tumor histology and chemosensitivity, suggesting it as a potential therapeutic target in select HGSC cases.

cancer biology↗

bioRxiv2023

Pre-ciliated tubal epithelial cells are prone to initiation of high-grade serous ovarian carcinoma

The distal region of the uterine (Fallopian) tube is commonly associated with high-grade serous carcinoma (HGSC), the predominant and most aggressive form of ovarian or extra-uterine cancer. Specific cell states and lineage dynamics of the adult tubal epithelium (TE) remain insufficiently understood, hindering efforts to determine the cell of origin for HGSC. Here, we report a comprehensive census of cell types and states of the mouse uterine tube. We show that distal TE cells expressing the stem/progenitor cell marker Slc1a3 can differentiate into both secretory (Ovgp1+) and ciliated (Fam183b+) cells. Inactivation of Trp53 and Rb1, whose pathways are commonly altered in HGSC, leads to elimination of targeted Slc1a3+ cells by apoptosis, thereby preventing their malignant transformation. In contrast, pre-ciliated cells (Krt5+, Prom1+, Trp73+) remain cancer-prone and give rise to serous tubal intraepithelial carcinomas and overt HGSC. These findings identify transitional pre-ciliated cells as a previously unrecognized cancer-prone cell state and point to pre-ciliation mechanisms as novel diagnostic and therapeutic targets.

cancer biology↗

bioRxiv2020

Identification of an antiretroviral small molecule that appears to be a host-targeting inhibitor of HIV-1 assembly

Given the projected increase in multidrug resistant HIV-1, there is an urgent need for development of antiretrovirals that act on virus life-cycle stages that are not targeted by antiretrovirals currently in use. Host-targeting drugs are of particular interest because they can offer a high barrier to resistance. Here we report identification of two related small molecules that inhibit HIV-1 late events, a stage of the HIV-1 life cycle for which potent and specific inhibitors are lacking. This chemotype was discovered using cell-free protein synthesis and assembly systems that recapitulate intracellular host-catalyzed viral capsid assembly pathways. These compounds inhibit replication of HIV-1 in human T cell lines and PBMCs and are effective against a primary isolate. They reduce virus production, likely by inhibiting a post-translational step in HIV-1 Gag assembly. Notably, the compound colocalizes with HIV-1 Gag in situ; however, unexpectedly, selection experiments failed to identify compound-specific resistance mutations in gag or pol, even though known resistance mutations developed in a parallel nelfinavir selection. Thus, we hypothesized that instead of binding to Gag directly, these compounds might localize to assembly intermediates, the intracellular multiprotein complexes containing Gag and host factors that are formed during immature HIV-1 capsid assembly. Indeed, imaging of infected cells showed colocalization of the compound with two host enzymes found in assembly intermediates, ABCE1 and DDX6. While the exact target and mechanism of action of this chemotype remain to be determined, these findings suggest that these compounds represent first-in-class, host-targeting inhibitors of intracellular events in HIV-1 assembly. IMPORTANCEThe success of antiretroviral treatment for HIV-1 is at risk of being undermined by the growing problem of drug resistance. Thus, there is a need to identify antiretrovirals that act on viral life cycle stages not targeted by drugs in use, such as the events of HIV-1 Gag assembly. To address this gap, we developed a compound screen that recapitulates the intracellular events of HIV-1 assembly, including viral-host interactions that promote assembly. This effort led to identification of a new chemotype that inhibits HIV-1 replication at nanomolar concentrations by inhibiting virus production. This compound colocalized with Gag and two host enzymes that facilitate capsid assembly but resistance selection did not result in compound-specific mutations in gag, suggesting that the chemotype does not directly target Gag. We hypothesize that this chemotype may represent a first-in-class inhibitor of virus production that acts by targeting a viral-host complex important for HIV-1 Gag assembly.

microbiology↗

bioRxiv2017

The ABCE1 capsid assembly pathway is conserved between primate lentiviruses and the non-primate lentivirus feline immunodeficiency virus

During immature capsid assembly in cells, the Gag protein of HIV-1 and other primate lentiviruses co-opts a host RNA granule, forming a pathway of assembly intermediates that contains host components, including two cellular enzymes shown to facilitate assembly, ABCE1 and DDX6. Here we asked whether a non-primate lentivirus, feline immunodeficiency virus (FIV), also forms such RNA-granule-derived intracellular capsid assembly intermediates. First, we found that, unlike for HIV-1, the FIV completed immature capsid and the largest putative assembly intermediate are unstable during analysis. Next, we identified in situ cross-linking conditions that overcame this problem and revealed the presence of FIV Gag complexes that correspond in size to early and late HIV-1 assembly intermediates. Because assembly-defective HIV-1 Gag mutants are arrested at specific intracellular assembly intermediates, we asked if a similar arrest is also observed for FIV. We analyzed four FIV Gag mutants, including three not previously studied that we identified based on sequence and structural similarity to HIV-1 Gag, and found that each is assembly-defective and arrested at the same intermediate as the corresponding HIV-1 mutant. Further evidence that these FIV Gag-containing complexes correspond to assembly intermediates came from co-immunoprecipitation studies demonstrating that FIV Gag is associated with ABCE1 and DDX6, as shown previously for HIV-1. Finally, we validated these co-immunoprecipitations with a proximity ligation assay that revealed co-localization between assembly-competent FIV Gag and ABCE1 in situ. Together, these data offer novel structure-function insights and indicate that primate and non-primate lentiviruses form intracellular capsid assembly intermediates derived from ABCE1-containing RNA granules.\n\nImportanceLike HIV-1, FIV Gag assembles into immature capsids; however, it is not known whether FIV Gag progresses through a pathway of immature capsid assembly intermediates derived from host RNA granules, as shown for HIV-1 Gag. Here we asked whether FIV Gag forms complexes similar in size to HIV-1 assembly intermediates and if FIV Gag is associated with ABCE1 and DDX6, two host enzymes that facilitate HIV-1 immature capsid assembly that are found in HIV-1 assembly intermediates. Our studies identified FIV Gag-containing complexes that closely resemble HIV-1 capsid assembly intermediates, showed that known and novel assembly-defective FIV Gag mutants fail to progress past these putative intermediates, and utilized biochemical and imaging approaches to demonstrate association of FIV Gag with ABCE1 and DDX6. Thus, we conclude that viral-host interactions important for immature capsid assembly are conserved between primate and non-primate lentiviruses, and could yield important targets for future antiviral strategies.

microbiology↗

bioRxiv2017

HIV-1 initiates genomic RNA packaging in a unique subset of host RNA granules

How HIV-1 genomic RNA (gRNA) is packaged into assembling virus remains unclear. Here, we use biochemical and in situ approaches to identify the complex in which the capsid protein Gag first associates with gRNA, termed the packaging initiation complex. First, we show that in the absence of assembling Gag, non-nuclear non-translating gRNA is nearly absent from the soluble fraction of provirus-expressing cells, and is found instead primarily in complexes >30S. When we express a Gag mutant known to be arrested at packaging initiation, we find only one complex containing Gag and gRNA; thus, this complex corresponds to the packaging initiation complex. This [~]80S complex also contains two cellular facilitators of assembly, ABCE1 and the RNA granule protein DDX6, and therefore corresponds to a co-opted host RNA granule and a previously described capsid assembly intermediate. Additionally, we find this granule-derived packaging initiation complex in HIV-1-infected H9 T cells, and demonstrate that wild-type Gag forms both the packaging initiation complex and a larger granule-derived complex corresponding to a late packaging/assembly intermediate. We also demonstrate that packaging initiation complexes are far more numerous than P bodies in situ. Finally, we show that Gag enters the [~]80S granule to form the packaging initiation complex via a two-step mechanism. In a step that is independent of a gRNA-binding domain, Gag enters a broad class of RNA granules, most of which lack gRNA. In a second step that is dependent on the gRNA-binding nucleocapsid domain of Gag or a heterologous gRNA-binding domain, Gag enters a gRNA-containing subset of these granules. Thus, we conclude that packaging in cells does not result from random encounters between Gag and gRNA; instead our data support a fundamentally different model in which Gag is directed to gRNA within a unique host RNA granule to initiate this critical event in HIV-1 replication.\n\nNontechnical SummaryTo form infectious virus, the HIV-1 capsid protein Gag must associate with and package the viral genomic RNA (gRNA) during the virus assembly process. HIV-1 Gag first associates with gRNA in the cytoplasm, forming a complex termed the packaging initiation complex; this complex subsequently targets to the plasma membrane where Gag completes the assembly and packaging process before releasing the virus from the cell. Although the packaging initiation complex is critical for infectious virus formation, its identity and composition, and the mechanism by which it is formed, remain unknown. Here we identify the packaging initiation complex, and demonstrate that it corresponds to a host RNA granule that is co-opted by the virus. RNA granules are diverse complexes utilized by host cells for all aspects of RNA storage and metabolism besides translation. Our study also defines the mechanism by which HIV-1 Gag enters this host RNA granule to form the packaging initiation complex, and reveal that it involves two steps that depend on different regions of Gag. Our finding that Gag co-opts a poorly studied host complex to first associate with gRNA during packaging provides a new paradigm for understanding this critical event in the viral life cycle.

microbiology↗