Biology subjects

Tsui, S. K. W.

Publications and source records attributed to Tsui, S. K. W..

4 recordsLinked to original sources

bioRxiv2026

Functional and sensitivity profiling of theKITMutation Landscape in Melanoma

Melanoma in Asia presents a unique epidemiological profile, with a higher prevalence of acral and mucosal subtypes compared to Western populations. While KIT mutations are found in up to 15% of Asian melanoma cases, clinical outcomes with KIT inhibitors have been modest due to heterogeneous mutation profiles and a lack of specific patient selection criteria. This study characterizes the landscape of KIT mutations in melanoma using the GENIE database, identifying 86 recurrent hotspots, many of which are variants of unknown significance (VUS). We validated drug sensitivities for key mutations using in vitro and in vivo models. Our results indicate that while the L576P mutation is highly sensitive to multiple inhibitors, the N822K mutation shows resistance to imatinib but responds to sunitinib, nilotinib, and nintedanib. These findings highlight the necessity of genotype-guided therapeutic strategies and provide a rationale for future clinical trials combining broad-spectrum KIT inhibitors with immune checkpoint inhibitors. Translational SignificanceMelanoma subtypes prevalent in Asia, specifically acral and mucosal melanoma, frequently harbor KIT mutations but show poor response rates (23-26%) to the standard-of-care inhibitor, imatinib. This study challenges the current clinical practice of treating all KIT-mutated melanomas uniformly. We demonstrate that specific recurrent mutations, such as N822K, are intrinsically resistant to imatinib but highly sensitive to broad-spectrum inhibitors like sunitinib and nintedanib. By establishing a comprehensive "lookup table" of drug sensitivities for both common and previously uncharacterized KIT variants, this work provides the evidence base required to transition from a "one-size-fits-all" approach to a genotype-guided precision medicine strategy. Furthermore, validating these targets informs the design of next-generation clinical trials, particularly those combining optimal KIT inhibitors with immune checkpoint blockade to improve survival in currently underserved patient populations.

cancer biology↗

bioRxiv2026

Mutation-Resolved Drug Sensitivity Atlas Reveals Broad RAS(ON) Inhibitor Vulnerabilities and a STAT3 Co-Dependency in NRAS-Mutant Melanoma

NRAS-mutated melanoma remains a major unmet clinical need, with no approved targeted therapy and rapid progression on standard treatment. Tri-complex RAS(ON) inhibitors such as daraxonrasib (RMC-6236) and RMC-7977 have shown early clinical activity, but the mutation-specific sensitivity landscape and adaptive resistance programs in melanoma remain undefined. To address this, we generated an isogenic 3D melanoma platform and performed a saturation mutagenesis screen across 95 NRAS missense variants (>99% of clinically recurrent variants), profiling oncogenic fitness and responses to six RAS-targeting agents in spheroids and xenografts. RMC-6236 and RMC-7977 showed the broadest activity and stratified recurrent NRAS mutants into hypersensitive (G12 variants and Q61R/K/L; [~]95% of cases), moderately sensitive (G13D/R/V; [~]4%), and resistant (G60E and Q61P; [~]1%) classes. Structural analyses supported distinct mechanisms underlying reduced susceptibility in a restricted subset of variants. In sensitive genotypes, RAS(ON) inhibition elicited an adaptive cytokine- and RTK-associated survival program converging on STAT3. Co-inhibition of STAT3 enhanced apoptosis, suppressed MYC, and induced tumor regression in NRAS-mutant melanoma models. Together, these findings define a mutation-resolved therapeutic landscape for NRAS-mutant melanoma and identify adaptive STAT3 signaling as a rational target for combination therapy. Statement of Translational SignificanceNRAS-mutated melanoma lacks effective targeted treatments, and clinical responses to immunotherapy are suboptimal. This study presents the first comprehensive drug sensitivity map across 95 NRAS mutations in melanoma, identifying the pan-RAS(ON) inhibitors RMC-6236 and RMC-7977 as broadly effective agents. Multiple mutants with reduced susceptibility are identified, providing mutation-informed guidance for patient selection and clinical trial stratification. Mechanistic analyses reveal that RTK/cytokine-driven STAT3 activation functions as a key survival pathway under RAS(ON) blockade, and its inhibition markedly enhances the efficacy of pan-RAS(ON) inhibitors. These findings support mutation-guided use of RAS(ON) inhibition and highlight STAT3 co-targeting as a rational strategy to strengthen and prolong therapeutic responses in NRAS-mutated melanoma. Highlights- A functional and therapeutic atlas defines 95 recurrent and nonrecurrent NRAS missense variants in melanoma - RMC-6236 and RMC-7977 show broad but genotype-selective activity across major NRAS mutations - A restricted subset of recurrent NRAS mutants shows reduced susceptibility to RAS(ON) inhibition - RAS(ON) inhibition induces an adaptive STAT3 survival program that is therapeutically targetable

cancer biology↗

bioRxiv2025

Human trunk embryoids with patterned anterior-posterior and dorsal-ventral body axes: utility for understanding human development and disease

Human embryoid models enable mechanistic studies of development and disease. We generated trunk embryoids from human pluripotent stem cells that recapitulate posterior trunk formation at Carnegie stage (CS) 8-10, with patterned anterior-posterior (A-P) and dorsal-ventral (D-V) axes. These self-organizing structures comprise a ventral notochord, dorsal neural tube, floor plate and bilateral somites. Genetic and chemical perturbations of SHH signaling confirmed the notochords central role in D-V patterning. Moreover, VANGL1/2 loss-of-function mutations recapitulated mouse phenotypes, including axial truncation and somite segmentation failure. This model enables detailed study of key developmental events that underlie posterior trunk formation and provides a promising platform for human disease modeling.

developmental biology↗

bioRxiv2017

Systematic selection of reference genes for normalization of circulating RNA transcripts in pregnant women based on RNA-seq data

RNA transcripts circulating in peripheral blood represent an important source of non-invasive biomarkers. To accurately quantify the levels of a circulating transcript, one needs to normalize the data with internal control reference genes, which are detected at relatively constant levels across different blood samples. A few stably-expressed reference gene candidates have to be selected from transcriptome data before validation of their stable expression by reverse-transcription quantitative polymerase chain reaction. However, there is a lack of transcriptome, let alone whole-transcriptome, data from maternal blood. To overcome this shortfall, we performed RNA-seq on blood samples from women presented with preterm labor. Of 11215 exons detected in the maternal blood whole-transcriptome, we systematically identified a panel of 395 genes comprising exons that were detected at a coefficient of variation (CV) ranging from 7.75%-17.7%. Their levels were considerably less variable than any GAPDH exon (minimum CV, 27.3%). Upon validation, selected genes from this panel remained as more stably expressed than GAPDH in maternal blood. This panel is over-represented with genes involved with actin cytoskeleton, macromolecular complex and the integrin signaling pathway. This groundwork provides a starting point for systematically selecting reference gene candidates for normalizing the levels of circulating RNA transcripts in maternal blood.

genomics↗