Biology subjects

Lee, K.-W.

Publications and source records attributed to Lee, K.-W..

9 recordsLinked to original sources

bioRxiv2026

BARCS: beta-binomial regression for multivariate CRISPR screen design

Pooled CRISPR screens increasingly use longitudinal, donor-adjusted, and factorial designs, but beta-binomial screen methods have largely remained limited to pairwise comparisons. BARCS extends the library-total-conditional beta-binomial model to guide-level regression with an arbitrary design matrix, enabling direct estimation of time, covariate, and interaction effects. In four replicate-complete Cas13 screens, adding the intermediate time point modestly improved essential-gene recovery. Applying the same non-targeting-control scaling rule to BARCS, MAGeCK-MLE, edgeR-QL, DESeq2, and limma--voom produced similar calibration across all five methods, while the four alternatives ranked essential genes more strongly than BARCS. In an ordered-bin IL2RA screen, donor-adjusted BARCS recovered more validated regulators with fewer total calls than the matched four-bin MAGeCK-MLE fit, and cross-fitted controls exposed excess guide-level significance. Simulations showed gains from dispersion moderation and control-based denominators, but seed-specific results exposed denominator sensitivity and a null grid localized substantial gene-level error to correlated-guide aggregation rather than dispersion alone. Aggregation-matched control scaling reduced but did not eliminate this error. An external audit prompted by concerns about beta-binomial false discoveries showed that the reported CB2 null-discovery count disappeared when full-library totals were restored. This corrected one denominator-dependent result but did not refute the broader calibration concern; nominal-level calibration remained unresolved. BARCS therefore contributes a multivariable extension of the library-total-conditional beta-binomial model together with an explicit account of where its inference is valid: guide-level coefficients are supported by independent biological libraries, whereas gene-level summaries and partitioned-bin designs require correlation-aware aggregation or joint modelling that the present implementation provides diagnostically rather than generatively. We report this boundary because complex pooled designs make it consequential, not because it is unique to the beta-binomial model.

bioinformatics↗

bioRxiv2026

Cyclic-Phe-Pro Binds the ToxRS Interface to Promote Signal Transduction in Vibrio vulnificus

In Vibrio vulnificus, the quorum-sensing signal cyclo-(L-phenylalanine-L-proline) (cFP) binds the membrane receptor ToxRS to activate genes linked to oxidative-stress resistance and virulence. ToxR is a transmembrane transcription factor that pairs with ToxS to sense periplasmic signals, yet how V. vulnificus ToxRS recognizes cFP has remained undefined. AI-guided structure prediction revealed preferential ToxR/S heterodimer formation and a fold conserved with the V. cholerae crystal structure. Molecular docking placed cFP in a hydrophobic pocket at the ToxR-ToxS interface, where Phe279 stacked with its phenyl ring and Arg277 hydrogen-bonded its carbonyl oxygen. Introducing R277L and F279A substitutions lowered basal leuO expression and abolished cFP-dependent induction in a lacZ fusion assay. ChIP showed that cFP enhanced wild-type ToxR binding to the leuO promoter, whereas the mutant bound weakly and did not respond. Thus cFP bridges ToxR and ToxS to stabilize the heterodimer, facilitating ToxR recruitment to promoters and transcriptional activation in V. vulnificus.

biochemistry↗

bioRxiv2025

VEGFR2 blockade overcomes acquired KRAS G12D inhibitor resistance driven by PI3Kγ activation

KRAS G12D mutation is a key oncogenic driver in many solid tumors, including pancreatic, gastric, and colorectal cancers. While recent studies have characterized features associated with primary and acquired resistance to KRAS inhibitors, strategies to overcome such resistance, particularly in the context of gastrointestinal cancers, remain underexplored. Here, we have generated nine human gastrointestinal cancer models, including three patient-derived organoids (PDOs), with acquired resistance to the KRAS G12D-selective inhibitor MRTX1133. Using single-cell RNA sequencing analysis, we identified the enrichment of angiogenesis, hypoxia, and epithelial-to-mesenchymal transition (EMT) signatures in the resistant model compared to the parental PDO. Across all resistant models, VEGFA expression and VEGFR2 phosphorylation were uniformly elevated, which were driven by AKT activation and SP1 nuclear translocation. Mechanistic investigations uncovered increased PI3K{gamma} activity in MRTX1133-resistant models via complex formation of KRAS with p110{gamma} and p101. This leads to an autocrine VEGFA-VEGFR2 signaling loop formation and EMT induction. Therapeutically, the disruption of VEGFA-VEGFR2 signaling restored MRTX1133 sensitivity and inhibited EMT. Furthermore, cancer-endothelial paracrine signaling amplified angiogenesis, hypoxia, and EMT signatures in cancer cells and simultaneously promoted endothelial cell proliferation, reinforcing an adaptive feedback mechanism. In a mouse model of MRTX1133-resistant tumor xenograft, a combination of anti-VEGFR2 therapy and MRTX1133 more effectively reduced tumor growth, angiogenesis, and proliferation markers than monotherapy without significant body weight change. These findings establish VEGFA-VEGFR2 signaling by PI3K{gamma} activation as a key driver of acquired resistance to KRAS G12D inhibition and provide a rationale for combining VEGFA-VEGFR2 inhibition with KRAS blockade in KRAS-mutant cancers. HighlightO_LIVEGFA-VEGFR2 signaling activation is a common feature of MRTX1133 resistance in KRASG12D cancer cells C_LIO_LINuclear translocation of SP1 by AKT activation promotes VEGFA transcription in MRTX1133-resistant models C_LIO_LIInteraction of p110{gamma}-p101 with KRAS activates PI3K{gamma} in the resistant models C_LIO_LIVEGFA-VEGFR2 inhibition reverses MRTX1133 resistance in vitro and in vivo C_LI

cancer biology↗

bioRxiv2024

Loss of p21-activated kinase 4 (PAK4) suppresses pancreatic tumor progression and metastasis through regulating E-cadherin

Pancreatic ductal adenocarcinoma (PDAC) is characterized by a poor prognosis with early and frequent metastasis. While p21-activated kinase 4 (PAK4) has been implicated in cell migration, and invasion, the molecular mechanisms in PDAC remain unknown. In this study, we found that PAK4 overexpression was correlated with poor survival in PDAC patients through analysis of TCGA data. PAK4-amplified PDAC cells showed enhanced mobility in contrast with wild-type. PAK4 knockdown in PAK4 amplified cells inhibited cell migration, invasion, and displacement by increased and stabilized E-cadherin, which was attributed to decreased activity of Cdc42. PAK4 knock-in in PAK4 wild-type models enhanced cell migration, invasion, and displacement by reduced E-cadherin through elevated Cdc42 activity. PAK4 bounded to E-cadherin, Cdc42, and p120ctn in immunoprecipitation. In confocal imaging, the colocalization of PAK4, E-cadherin, p120ctn, and Cdc42 was also identified. In an orthotopic PDAC mouse model, PAK4 knockdown decreased primary tumor size and occurrence of malignant ascites by activation of E-cadherin. Notably, in patients tissue specimens, inverse correlation on expression of PAK4 and E-cadherin were also shown. In conclusion, our study highlights that PAK4 promotes invasive and metastatic behavior by regulating E-cadherin in PDAC. PAK4 could be a potential therapeutic target for PDAC patients. Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=120 SRC="FIGDIR/small/594599v1_ufig1.gif" ALT="Figure 1"> View larger version (28K): org.highwire.dtl.DTLVardef@1755a23org.highwire.dtl.DTLVardef@170b2a1org.highwire.dtl.DTLVardef@1df96edorg.highwire.dtl.DTLVardef@2dc46b_HPS_FORMAT_FIGEXP M_FIG C_FIG

cancer biology↗

bioRxiv2022

Auxin Plays a Role in the Adaptation of Rice to Anaerobic Germination and Seedling Establishment

Auxin is well known to stimulate coleoptile elongation and rapid seedling growth in the air. However, its role in regulating rice germination and seedling establishment under submergence is largely unknown. Previous studies have shown that excessive levels of IAA frequently cause the inhibition of plant growth and development. In the present study, the high-level accumulation of endogenous IAA is observed under submergence in the dark, stimulating rice coleoptile elongation but limiting the root and primary leaf growth during anaerobic germination (AG). We found that oxygen and light can reduce IAA levels, promote the seedling establishment and enhance rice AG tolerance. miRNA microarray profiling and RNA gel blot analysis results show that the expression of miR167 is negatively regulated by submergence; it subsequently modulates the accumulation of free IAA through the miR167-ARF-GH3 pathway. The OsGH3-8 encodes an IAA-amido synthetase that functions to prevent free IAA accumulation. Reduced miR167 levels or overexpressing OsGH3-8 increase auxin metabolism, reduce endogenous levels of free IAA and enhance rice AG tolerance. The present study reveals that poor seed germination and seedling growth inhibition resulting from excessive IAA accumulation would cause intolerance to submergence in rice, suggesting that a certain threshold level of auxin is essential for rice AG tolerance.

plant biology↗

bioRxiv2022

Gallbladder adenocarcinomas undergo subclonal diversification and selection from precancerous lesions to metastatic tumors

We aimed to elucidate the evolutionary trajectories of gallbladder adenocarcinoma (GBAC) using multi-regional and longitudinal tumor samples. Using whole-exome sequencing data, we constructed phylogenetic trees in each patient, and analyzed mutational signatures. A total of 11 patients including 2 rapid autopsy cases were enrolled. The most frequently altered gene in primary tumors was ERBB2 (54.5%), followed by TP53 (45.5%), and FBXW7 (27.3%). Most mutations in frequently altered genes in primary tumors were detectable in concurrent precancerous lesions (biliary intraepithelial neoplasia, BilIN), but some of them were subclonal. Subclonal diversity was common in BilIN (n=4). However, among subclones in BilIN, a certain subclone commonly shrank in concurrent primary tumors. In addition, selected subclones underwent linear and branching evolution, maintaining subclonal diversity. In combined analysis with metastatic tumors (n=11), branching evolution was identified in 9 (81.8%) patients. Of these, 8 patients (88.9%) had a total of 11 subclones expanded at least 7-fold during metastasis. These subclones harbored putative metastasis-driving mutations in tumor suppressor genes such as SMAD4, ROBO1, and DICER1. In mutational signature analysis, 6 mutational signatures were identified: 1, 3, 7, 13, 22, and 24 (cosine similarity >0.9). Signatures 1 (age) and 13 (APOBEC) decreased during metastasis while signatures 22 (aristolochic acid) and 24 (aflatoxin) were relatively highlighted. Subclonal diversity arose early in precancerous lesions and the clonal selection was a common event during malignant transformation in GBAC. However, selected cancer clones continued to evolve and thus maintained subclonal diversity in metastatic tumors.

genetics↗

bioRxiv2021

Insights into the genetic architecture of complex traits in Napier grass (Cenchrus purpureus) and QTL regions governing forage biomass yield, water use efficiency and feed quality traits

Napier grass is the most important perennial tropical grass native to Sub-Saharan Africa and widely grown in tropical and subtropical regions around the world, primarily as a forage crop for animal feed, but with potential as an energy crop and in a wide range of other areas. Genomic resources have recently been developed for Napier grass that need to be deployed for genetic improvement and molecular dissection of important agro-morphological and feed quality traits. From a diverse set of Napier grass genotypes assembled from two independent collections, a subset of 84 genotypes that best represents the genetic diversity of the collections were selected and evaluated for two years in dry (DS) and wet (WS) seasons under three soil moisture conditions: moderate water stress in DS (DS-MWS); severe water stress in DS (DS-SWS) and, under rainfed (RF) conditions in WS (WS-RF). Data for agro-morphological and feed quality traits, adjusted for the spatial heterogeneity in the experimental blocks, were collected over a two-year period from 2018 to 2020. A total of 135,706 molecular markers were filtered, after removing markers with missing values > 10% and a minor allele frequency (MAF) < 5 %, from the high-density genome-wide markers generated previously using the genotyping by sequencing (GBS) method of the DArTseq platform. A genome-wide association study (GWAS), using two different mixed linear model algorithms, identified more than 58 QTL regions and markers associated with agronomic, morphological and water-use efficiency traits. QTL regions governing purple pigmentation and feed quality traits were also identified. The identified markers will be useful in the genetic improvement of Napier grass through the application of marker-assisted selection and for further characterization and map-based cloning of the QTLs.

genetics↗

bioRxiv2019

JuLI: accurate detection of DNA fusions in clinical sequencing for precision oncology

Accurate detection of genomic fusions by high-throughput sequencing in clinical samples with inadequate tumor purity and formalin-fixed paraffin embedded (FFPE) tissue is an essential task in precise oncology. We developed the fusion detection algorithm Junction Location Identifier (JuLI) for optimization of high-depth clinical sequencing. We implemented novel filtering steps to minimize false positives and a joint calling function to increase sensitivity in clinical setting. We comprehensively validated the algorithm using high-depth sequencing data from cancer cell lines and clinical samples and whole genome sequencing data from NA12878. We showed that JuLI outperformed state-of-the-art fusion callers in cases with high-depth clinical sequencing and rescued a driver fusion from false negative in plasma cell-free DNA. JuLI is freely available via GitHub (https://github.com/sgilab/JuLI).

bioinformatics↗

bioRxiv2017

Multi-dimensional genomic analysis of myoepithelial carcinoma identifies prevalent oncogenic gene fusions

Myoepithelial carcinoma (MECA) is an aggressive type of salivary gland cancer with largely unknown molecular features. MECA may arise de novo or result from oncogenic transformation of a pre-existing pleomorphic adenoma (MECA ex-PA). We comprehensively analyzed the molecular alterations in MECA with integrated genomic analyses. We identified a low mutational load (0.5/MB), but a high prevalence of fusion oncogenes (28/40 tumors; 70%). We found FGFR1-PLAG1 in 7 (18%) cases, and the novel TGFBR3-PLAG1 fusion in 6 (15%) cases. TGFBR3-PLAG1 was specific for MECA de novo tumors or the malignant component of MECA ex-PA, was absent in 723 other salivary gland tumors, and promoted a tumorigenic phenotype in vitro. We discovered other novel PLAG1 fusions, including ND4-PLAG1, which is an oncogenic fusion between mitochondrial and nuclear DNA. One tumor harbored an MSN-ALK fusion, which was tumorigenic in vitro, and targetable with ALK inhibitors. Certain gene fusions were predicted to result in neoantigens with high MHC binding affinity. A high number of copy number alterations was associated with poorer prognosis. Our findings indicate that MECA is a fusion-driven disease, nominate TGFBR3-PLAG1 as a hallmark of MECA, and provide a framework for future steps of diagnostic and therapeutic research in this lethal cancer.

cancer biology↗