Biology subjects

Ashokkumar, C.

Publications and source records attributed to Ashokkumar, C..

6 recordsLinked to original sources

bioRxiv2026

Spatially resolved tumor-microenvironment architecture defines therapeutic response in unresectable hepatoblastoma

Background: Hepatoblastoma exhibits variable therapeutic response that is not fully explained by current risk stratification. While prior studies have characterized tumor composition, the role of spatial organization in determining outcome, particularly in unresectable disease requiring transplantation under immunosuppression, remains unclear. Methods: We integrated spatial transcriptomics using the 10x Genomics Visium platform (n = 11 tumors) with single-cell spatial molecular imaging using NanoString CosMx (n = 3 tumors) on post-chemotherapy explant specimens across clinically defined groups (relapse-prone unresectable, non-relapse unresectable, and resectable hepatoblastoma). Spatial deconvolution, module scoring, spatial co-localization, and cell-cell interaction analyses were used to define region-level transcriptional programs and their underlying cellular organization. Results: We identified three spatial architectures associated with clinical outcome. Relapse-prone tumors exhibited a centralized, TME-dominated organization enriched for progenitor-like, cycling, and stress-responsive tumor cell states co-localized with SPP1+ TAMs and CAFs, with enrichment of hypoxia response, extracellular matrix remodeling, and Midkine (MDK-LRP1) signaling. Non-relapse tumors displayed a distributed architecture with compartmentalized tumor-immune interactions, increased immune engagement, and preserved epithelial differentiation, including inflammatory hepatocyte-like states. Resection samples showed reduced tumor cell state heterogeneity and more uniform TME-immune organization. Conclusions: Integration of regional and single-cell spatial transcriptomics across two platforms reveals that the chemo-remodeled tumor architecture of hepatoblastoma encodes spatially organized tumor cell-TME interactions as central determinants of therapeutic response.

cancer biology↗

bioRxiv2026

Spatial landscape of pretransplant liver disease and post-transplant immune outcomes in children

Defining molecular patterns underlying pediatric end-stage liver disease and its treatment with liver transplantation requires rich datasets spanning a multitude of diagnoses and transplant outcomes. Here, we describe the spatial molecular landscape of approximately five million liver cell profiles from 98 liver tissue samples. The samples span donor liver, used here as a reference tissue, and end-stage diseases including biliary atresia, progressive familial intrahepatic cholestasis, hepatoblastoma, acute liver failure, and gestational alloimmune liver disease. Post-transplant liver allograft biopsies include those without and with T-cell-mediated and antibody-mediated rejection, mixed pathology, and outcome groups from immunosuppression withdrawal studies. Samples were profiled using the CosMx Human Universal Cell Characterization RNA Panel (1K) and the CosMx Human 6K Discovery Panel (6K). Preliminary exploratory analyses include cellular composition and gene abundance and variability across clinical cohorts. A twelve-gene signature comprising the genes with the highest variance implicates acute-phase response genes (e.g., SAA1) and profibrotic genes (e.g., COL1A1) as a shared link across these otherwise distinct conditions. This injury-repair-remodeling gene network warrants further investigation through higher-resolution, zone-specific spatial mapping to help clarify disease pathogenesis.

genomics↗

bioRxiv2025

Liver transplant rejection features memory cell priming, spatially differentiated networks and novel drug targets.

Acute T-cell-mediated transplant rejection, the earliest contributor to immunological graft failure responds variably to T-cell suppression. Early rejection can co-exist with donor-specific antibodies which also shorten graft survival, without affecting graft histology visibly. Here, during early liver transplant rejection, blood leukocytes manifest primed T-cells with heat shock protein (HSP) signaling and transcriptional programs for memory cell expansion. Corresponding biopsies demonstrate upregulated immune synapse and proteasomal genes in T-cell-infiltrated portal and central regions of the liver lobule. With donor-specific antibodies, the intervening intralobular region demonstrates a germinal-center-like allograft response with upregulated CD40, chemokine, T-follicular and complement signaling, which intensifies along the direction of sinusoidal blood flow from portal to central regions. Proteasomal and HSP90 inhibitors suppress donor-specific alloresponses of T- and B-cells in blood samples from patients with early rejection. The molecular injury spectrum of early rejection is complex, spatially differentiated and reveals novel early immunosuppressive strategies to extend graft survival.

immunology↗

bioRxiv2022

Enhanced donor antigen presentation by B-cells predicts acute cellular rejection and late outcomes after transplantation.

PurposeEnhanced B-cell presentation of donor alloantigen relative to presentation of HLA-mismatched reference alloantigen is associated with acute cellular rejection (ACR), when expressed as a ratio called the antigen presenting index (API) in an exploratory cohort of liver and intestine transplant (LT, IT) recipients. MethodsTo test clinical performance, we measured the API using the previously described 6-hour assay in 84 LT and 54 IT with median age 3.3 years (0.05-23.96). Recipients experiencing ACR within 60 days after testing were termed rejectors. ResultsWe first confirmed that B-cell uptake and presentation of alloantigen induced and thus reflected the alloresponse of T-helper cells, which were incubated without and with cytochalasin and primaquine to inhibit antigen uptake and presentation, respectively. Transplant recipients included 76 males and 62 females. Rejectors were tested at median 3.6 days before diagnosis. The API was higher among rejectors compared with non-rejectors (2.2 {+/-} 0.2 vs 0.6 {+/-} 0.04, p-value=1.7E-09). In logistic regression and ROC analysis, API [≥] 1.1 achieved sensitivity, specificity, positive and negative predictive values for predicting ACR in 99 training set samples. Corresponding metrics ranged from 80-88% in 32 independent post-transplant samples, and 73-100% in 20 independent pre-transplant samples. In time-to-event analysis, API [≥] 1,1 predicted higher incidence of late DSA after API measurements in LT (p=0.011) and graft loss in IT recipients (p=0.008), compared with recipients with API<1.1, respectively. ConclusionEnhanced donor antigen presentation by circulating B-cells predicts rejection after liver or intestine transplantation as well as higher incidence of DSA and graft loss late after transplantation

immunology↗

bioRxiv2022

The role of dynamic DNA methylation in liver transplant rejection in children

BackgroundTranscriptional regulation of liver transplant (LT) rejection may reveal novel predictive and therapeutic targets. PurposeTo test the role of differential DNA methylation in children with biopsy-proven acute cellular rejection (rejectors, R) after LT. MethodsPaired peripheral blood DNA samples were obtained before and after LT from 17 children, including 4R and 13 non-rejector (NR), and assayed with MethylC capture sequencing (MCC-Seq) approach covering 5 million CpGs in immune-cell specific regulatory elements. Differentially methylated CpGs (DMCs) were identified using generalized linear regression models adjusting for sex and age and merged into differentially methylated regions (DMR) comprising 3 or more DMCs. ResultsContrasting R vs NR, we identified 2238 DMCs in post-LT and 2620 DMCs in pre-LT samples, which clustered in 216 and 282 DMRs respectively. DMCs associated with R were enriched in enhancers and depleted in promoters. The proportion of hypomethylated versus hypermethylated DMRs increased from 22% to 48% (p<0.0001) in pre-LT vs. post-LT DMCs, respectively. The highest-ranked biological processes enriched in post-LT DMCs were antigen processing and presentation via MHC class I, MHC class I complex, and peptide binding (p<7.92E-17), respectively. Top-ranked DMRs mapped to genes which mediate B-cell receptor signaling (ADAP1) or regulate several immune cells (ARRB2) (p<3.75E-08). DMRs in MHC class I genes were enriched for SNPs which bind TFs, affect gene expression and splicing, or alter peptide-binding amino acid sequences. ConclusionsDynamic methylation in distal regulatory regions reveals known transplant-relevant MHC-dependent rejection pathways, and identifies novel loci for future mechanistic evaluations in pediatric transplant subcohorts.

genomics↗

bioRxiv2021

Impaired T-cell and antibody immunity after COVID-19 infection in chronically immunosuppressed transplant recipients

Assessment of T-cell immunity to the COVID-19 coronavirus requires reliable assays and is of great interest, given the uncertain longevity of the antibody response. Some recent reports have used immunodominant spike (S) antigenic peptides and anti-CD28 co-stimulation in varying combinations to assess T-cell immunity to SARS-CoV-2. These assays may cause T-cell hyperstimulation and could overestimate antiviral immunity in chronically immunosuppressed transplant recipients, who are predisposed to infections and vaccination failures. Here, we evaluate CD154-expressing T-cells induced by unselected S antigenic peptides in 204 subjects-103 COVID-19 patients and 101 healthy unexposed subjects. Subjects included 72 transplanted and 130 non-transplanted subjects. S-reactive CD154+T-cells co-express and can thus substitute for IFN{gamma} (n=3). Assay reproducibility in a variety of conditions was acceptable with coefficient of variation of 2-10.6%. S-reactive CD154+T-cell frequencies were a) higher in 42 healthy unexposed transplant recipients who were sampled pre-pandemic, compared with 59 healthy non-transplanted subjects (p=0.02), b) lower in Tr COVID-19 patients compared with healthy transplant patients (p<0.0001), c) lower in Tr patients with severe COVID-19 (p<0.0001), or COVID-19 requiring hospitalization (p<0.05), compared with healthy Tr recipients. S-reactive T-cells were not significantly different between the various COVID-19 disease categories in NT recipients. Among transplant recipients with COVID-19, cytomegalovirus co-infection occurred in 34%; further, CMV-specific T-cells (p<0.001) and incidence of anti-receptor-binding-domain IgG (p=0.011) were lower compared with non-transplanted COVID-19 patients. Healthy unexposed transplant recipients exhibit pre-existing T-cell immunity to SARS-CoV-2. COVID-19 infection leads to impaired T-cell and antibody responses to SARS-CoV-2 and increased risk of CMV co-infection in transplant recipients.

immunology↗