Islet xenotransplantation using gal-deficient neonatal donors improves engraftment and function

Significant deficiencies in understanding of xenospecific immunity have impeded the success of preclinical trials in xenoislet transplantation. Although galactose-α1,3-galactose, the gal epitope, has emerged as the principal target of rejection in pig-to-primate models of solid organ transplant, the importance of gal-specific immunity in islet xenotransplant models has yet to be clearly demonstrated. Here, we directly compare the immunogenicity, survival and function of neonatal porcine islets (NPIs) from gal-expressing wild-type (WT) or gal-deficient galactosyl transferase knockout (GTKO) donors. Paired diabetic rhesus macaques were transplanted with either WT (n = 5) or GTKO (n = 5) NPIs. Recipient blood glucose, transaminase and serum xenoantibody levels were used to monitor response to transplant. Four of five GTKO versus one of five WT recipients achieved insulin-independent normoglycemia; transplantation of WT islets resulted in significantly greater transaminitis. The WT NPIs were more susceptible to antibody and complement binding and destruction in vitro. Our results confirm that gal is an important variable in xenoislet transplantation. The GTKO NPI recipients have improved rates of normoglycemia, likely due to decreased susceptibility of xenografts to innate immunity mediated by complement and preformed xenoantibody. Therefore, the use of GTKO donors is an important step toward improved consistency and interpretability of results in future xenoislet studies.

Alternative immunomodulatory strategies for xenotransplantation: CD40/154 pathway-sparing regimens promote xenograft survival

Immunosuppressive therapies that block the CD40/CD154 costimulatory pathway have proven to be uniquely effective in preclinical xenotransplant models. Given the challenges facing clinical translation of CD40/CD154 pathway blockade, we examined the efficacy and tolerability of CD40/CD154 pathway-sparing immunomodulatory strategies in a pig-to-nonhuman primate islet xenotransplant model. Rhesus macaques were rendered diabetic with streptozocin and given an intraportal infusion of ≈ 50 000 islet equivalents/kg wild-type neonatal porcine islets. Base immunosuppression for all recipients included maintenance therapy with belatacept and mycophenolate mofetil plus induction with basiliximab and LFA-1 blockade. Cohort 1 recipients (n = 3) were treated with the base regimen alone; cohort 2 recipients (n = 5) were additionally treated with tacrolimus induction and cohort 3 recipients (n = 5) were treated with alefacept in place of basiliximab, and more intense LFA-1 blockade. Three of five recipients in both cohorts 2 and 3 achieved sustained insulin-independent normoglycemia (median rejection-free survivals 60 and 111 days, respectively), compared to zero of three recipients in cohort 1. These data show that CD40/CD154 pathway-sparing regimens can promote xenoislet survival. Further optimization of these strategies is warranted to aid the clinical translation of islet xenotransplantation.

Trans-11 vaccenic acid improves insulin secretion in models of type 2 diabetes in vivo and in vitro

SCOPE

Trans-11 vaccenic acid (VA) is a fatty acid produced by ruminants entering the human food supply through meat and dairy products, which appears not to have the health risks associated with industrially produced trans-fatty acids. In this study, we investigated the effect of VA on insulin secretion in vivo in rats and in vitro in human and rat islets after diabetogenic insult.

METHODS AND RESULTS

Hyperglycemic clamp showed that VA dietary supplementation for 8 weeks significantly increased glucose turnover in rats with type 2 diabetes (T2D), accompanied by an elevated plasma C-peptide concentration, indicating improved insulin secretion. The β-cell area and proliferation rate were higher in T2D+VA than T2D group. Isolated islets from T2D+VA rats had higher glucose-stimulated insulin secretion (GSIS) than T2D group. In vitro, VA treatment for 24 and 48 h significantly enhanced GSIS in rat and human islets after diabetogenic challenges. The mRNA expression of G-protein-coupled receptor 40 (GPR40) and regenerating islet-derived 1α (REG-1α) were consistently increased by VA in both rat and human islets.

CONCLUSION

These results indicate that VA may improve insulin secretion and growth of islets in T2D, at least partly by altering GPR40 and REG-1α mRNA expression.

A comparison of the immunosuppressive effects of cyclosporine A and cyclosporine G in vivo and in vitro

In this study we compared the immunosuppressive effects of cyclosporine (Cs) A and G, both in vitro (human and rabbit) and in vivo (rabbit). The 50% inhibitory concentration (IC50) of CsG was up to three times greater than that of CsA for mitogen and alloantigen-induced lymphocyte proliferation (IC50 CsA 1 degree MLC = 19 +/- 4 micrograms/L vs. IC50 CsG = 60 +/- 7 micrograms/L; P < 0.01). Kinetic studies in both human and rabbit systems showed that the effectiveness of both drugs was similarly reduced when added at later times after culture initiation. The effects of CsA and CsG in combination on immune responses appeared to be antagonistic at higher and additive at lower drug doses. We also compared the ability of CsA and CsG to displace 3H-CsA from PBMC. The 50% displacement concentration (DC50) for CsG was up to three times greater than that for CsA (DC50 CsA = 1.44 +/- 2.49 x 10(-7) M vs. DC50 CsG = 3.9 +/- 5.4 x 10(-7) M; P < 0.05), suggesting that CsG does not bind as well to PBMC as CsA. In vivo studies using skin allografts confirmed in vitro findings. Both CsA and CsG at 5 and 10 mg/kg/day significantly (P < 0.01) prolonged graft survival compared with control animals. However, at these doses and even at 15 mg/kg/day CsG, CsA was more efficacious at prolonging skin graft survival in rabbits (P < 0.01), e.g., mean survival time (MST, days) 10 mg/kg/day CsA = > 20.5 vs. MST 15 mg/kg/day CsG = 15.0. These results suggest that both in vitro and in vivo in rabbits CsG is less immunosuppressive than CsA.

Increased CD4/CD8 Lymphocyte ratio predicts favourable neoadjuvant treatment response in gastric cancer: A prospective pilot study

BACKGROUND

Despite optimal neoadjuvant chemotherapy only 40% of gastric cancer tumours achieve complete or partial treatment response. In the absence of treatment response, neoadjuvant chemotherapy in gastric cancer contributes to adverse events without additional survival benefit compared to adjuvant treatment or surgery alone. Additional strategies and methods are required to optimize the allocation of existing treatment regimens such as FLOT chemotherapy (5-Fluorouracil, Leucovorin, Oxaliplatin and Docetaxel). Predictive biomarkers detected using immunohistochemistry (IHC) methods may provide useful data regarding treatment response.

AIM

To investigate the utility of CD4, CD8, Galectin-3 and E-cadherin in predicting neoadjuvant FLOT chemotherapy tumour response in gastric adenocarcinoma.

METHODS

Forty-three adult patients with gastric adenocarcinoma, of which 18 underwent neoadjuvant chemotherapy, were included in a prospective clinical cohort. Endoscopic biopsies were obtained from gastric cancer and normal adjacent gastric mucosa. Differences in expression of Galectin-3, E-cadherin, CD4⁺ and CD8⁺ molecules between tumours with and without treatment response to neoadjuvant chemotherapy were assessed with IHC. Treatment response was graded by clinical pathologists using the Tumour Regression Score according to the College of American Pathologists criteria. Treatment response was defined as complete or near complete tumour response, whereas partial or poor/no response was defined as incomplete. Digital IHC images were annotated and quantitatively assessed using QuPath 0.3.1. Biomarker expression between responsive and incomplete response tumours was assessed using a two-sided Wilcoxon test. Biomarker expression was also compared between normal and cancer tissue and between 15 paired tumour samples before and after chemotherapy. We performed a preliminary multivariate analysis and power analysis to guide future study. Statistical analyses were completed using R 4.1.2.

RESULTS

The ratio between CD4⁺ and CD8⁺ lymphocytes was significantly greater in treatment responsive tumours (Wilcoxon, P = 0.03). In univariate models, CD4⁺/CD8⁺ ratio was the only biomarker that significantly predicted favourable treatment response (Accuracy 86%, P < 0.001). Using a glmnet multivariate model, high CD4⁺/CD8⁺ ratio and low Galectin-3 expression were the most influential variables in predicting a favourable treatment response. Analyses of paired samples found that FLOT chemotherapy also results in increased expression of CD4⁺ and CD8⁺ tumour infiltrating lymphocytes (Paired Wilcoxon, P = 0.002 and P = 0.008, respectively). Our power analysis suggests future study requires at least 35 patients in each treatment response group for CD8 and Galectin-3 molecules, whereas 80 patients in each treatment response group are required to assess CD4 and E-cadherin biomarkers.

CONCLUSION

We demonstrate that an elevated CD4⁺/CD8⁺ Ratio is a promising IHC-based biomarker to predict favourable treatment response to FLOT neoadjuvant chemotherapy in locally advanced gastric cancer.

A novel optical tracer for VMAT2 applied to live cell measurements of vesicle maturation in cultured human β-cells

The islet β-cells integrate external signals to modulate insulin secretion to better regulate blood glucose levels during periods of changing metabolic demand. The vesicular monoamine transporter type 2 (VMAT2), an important regulator of CNS neurotransmission, has an analogous role in the endocrine pancreas as a key control point of insulin secretion, with additional roles in regulating β-cell differentiation and proliferation. Here we report on the synthesis and biological characterisation of a fluorescent ligand for VMAT2 suitable for live cell imaging. Staining for VMAT2 and dopamine in live β-cell cultures show colocalisation in specific vesicles and reveal a heterogeneous population with respect to cell size, shape, vesicle number, size, and contents. Staining for VMAT2 and zinc ion, as a surrogate for insulin, reveals a wide range of vesicle sizes. Immunohistochemistry shows larger β-cell vesicles enriched for proinsulin, whereas smaller vesicles predominantly contain the processed mature insulin. In β-cell cultures obtained from nondiabetic donors, incubation at non-stimulatory glucose concentrations promotes a shift in vesicle diameter towards the more mature insulin vesicles at the expense of the larger immature insulin secretory vesicle population. We anticipate that this probe will be a useful reagent to identify living β-cells within complex mixtures for further manipulation and characterisation.

Low energy X-ray (grenz ray) treatment of purified islets prior to allotransplant markedly decreases passenger leukocyte populations

Grenz rays, or minimally penetrating X-rays, are known to be an effective treatment of certain recalcitrant immune-mediated skin diseases, but their use in modulating allograft rejection has not been tested. We examined the capacity of grenz ray treatment to minimize islet immunogenicity and extend allograft survival in a mouse model. In a preliminary experiment, 1 of 3 immunologically intact animals demonstrated long-term acceptance of their grenz ray treated islet allograft. Further experiments revealed that 28.6% (2 of 7) grenz ray treated islet allografts survived >60 d. A low dose of 20Gy, was important; a 4-fold increase in radiation resulted in rapid graft failure, and transplanting a higher islet mass did not alter this outcome. To determine whether increased islet allograft survival after grenz treatment would be masked by immunosuppression, we treated the recipients with CTLA-4 Ig, and found an additive effect, whereby 17.5% more animals accepted the graft long-term versus those with CTLA-4 Ig alone. Cell viability assays verified that islet integrity was maintained after treatment with 20Gy. As well, through splenocyte infiltration analysis, donor CD4+ T cell populations 24-hours after transplant were decreased by more than16-fold in recipients receiving irradiated islets compared with control. Donor CD8+ T cell populations, although less prevalent, decreased in all treatment groups compared with control. Our results suggest that brief treatment of isolated islets with low energy grenz rays before allotransplantation can significantly reduce passenger leukocytes and promote graft survival, possibly by inducing donor dendritic cells to differentiate toward a tolerogenic phenotype.

A 107-gene Nanostring assay effectively characterizes complex multiomic gastric cancer molecular classification in a translational patient-derived organoid model

4049

Background: Multi-omics profiling of gastric cancer (GC) has produced numerous molecular classification systems. However, widespread clinical implementation and testing of molecular subtypes are currently limited. Here, we develop, validate and implement a custom Nanostring assay capable of allocating GC molecular subtypes to clinical specimens in a translational patient-derived organoid model. Methods: Using publicly available whole-transcriptome data, machine learning models were developed to predict GC molecular subtypes from 376 Cancer Genome Atlas (TCGA) and 1797 Tumour Microenvironment Score (TME) patients. Models were generated using feature selection with 10-fold nested cross-validation. GC biopsies from 10 local patients were preserved in paraffin (tumour) and established as an organoid culture (organoid). Gene expression was measured using Nanostring. The allocation of molecular subtypes was internally and externally validated using gold-standard reference features in public databases comprising 2202 GC patients and 10 tumour-organoid pairs, respectively. We evaluated the concordance of tumour-organoid molecular subtypes and explored the correlation between subtype scores and in-vitro chemotherapy response. Results: Classification models for TCGA (57 genes) and TME (50 genes) predicted subtypes with an accuracy ± standard deviation of 89.46% ± 0.04 and 89.33% ± 0.02, respectively. Subtype assignment of microsatellite instability (MSI) in reference to capillary electrophoresis was found to have 99.3% [95% CI 97.4-99.9, n = 277] internal and 100% [95% CI 83.2-100, n = 20] external accuracy. In reference to Epstein-Barr Virus (EBV) in-situ hybridization, EBV type internal and external accuracy was 98.7% [95% CI 97.4-99.5, n = 552] and 100% [95% CI 83.2-100, n = 20], respectively. TCGA Genomically Stable (GS) scores followed a previously characterized enrichment of diffuse-type histology compared to intestinal-type in internal and external cohorts (Dunn’s Test, p < 0.0001 and p < 0.05, n = 1471 and n = 15, respectively). Statistically similar subtype scores (Paired Wilcoxon, p > 0.05) were found for tumour-organoid pairs. Discordance occurred in three tumour-organoid pairs. In-vitro Drug Sensitivity Score was not statistically efficacious in any molecular subtype, but Pearson correlation identified increasing efficacy with increasing EBV and MSI scores. Conclusions: Patient-derived organoids generally recapitulate the molecular subtype of parent tumours; however, in specific cases, subtype discordance occurs. Although additional external validation is required, our 107 gene assay effectively captures multi-omics classification systems in GC and allows future inquiry into the prognostic and therapeutic implications of these molecular subtypes.