O007 Pancreas and islet transplantation in the United Kingdom during the COVID-19 era

Introduction

Methods

Results

Conclusion

Take-home message

O002 Diabetes-associated HLA donor genotypes and pancreas transplant outcomes

Introduction

The genotypes HLA DR3/DR4, DR3/DR3, DR4/DR4 are associated with a predisposition to diabetes. This study evaluated UK recipient outcomes after pancreas transplantation from donors with a diabetes-associated genotypes.

Methods

Data on all UK pancreas transplants from 2004–2019 was obtained from the NHSBT-UK Registry, n=2,938. HLA-DR type was recorded for all organ donors. Re-transplants and those missing patient (PS) or graft (GS) survival were excluded, resulting in a final cohort of n=2,661. We further delineated our categories into SPK, PTA and PAK as a previous study suggested different recipient categories may be adversely affected. Univariate analyses were conducted using Kaplan-Meier plots and multi-variate analysis using Cox-regression models. Complications were analysed using chi-squared analyses.

Results

The majority of grafts were from donors not associated with diabetes genotypes (90.1%, n=2397) whereas 5.4%(n=145) came from HLA DR3/DR4 donors, 1.6%(n=43) from DR3/DR3 and (n=76)2.9% from DR4/DR4. Comparable outcomes for GS at 1yr (SPK p=0.980, PTA p=0.759, PAK p=0.244) and 3yrs (SPK p=0.708, PTA p=0.744, PAK p=0.275) and PS at 1yr (SPK p=0.553, PTA p=0.527, PAK p=0.756) and 3yrs (SPK p=0.728, PTA p=0.928, PAK p=0.424) were seen. Multivariate analysis also showed no statistically significant difference in GS (p=0.604, HR 1.041, 95%CI 0.895, 1.211) or PS (p=0.623, HR 1.045, 95%CI 0.876, 1.248). There were comparable complication rates.

Conclusion

This multicentre UK study has found comparable survival outcomes and complication rates within our donor-HLA-genotype groups. We do not believe that the presence or absence of a diabetes associated HLA-genotype influences outcomes for any category of pancreas transplant.

Take-home message

We do not believe that the presence or absence of a diabetes-associated HLA-genotype influences outcomes for any category of pancreas transplant.

Abstract 2195: A tissue atlas of oncogenic RAS mutation

Despite over 50 possible oncogenic RAS mutations, cancers tend to have a bias towards a specific subset unique to each cancer type. As RAS mutations could arise from selection of an ideal level (quantitative) or type (qualitative) of oncogenic signaling, we generated four conditional Kras alleles with different oncogenic mutations, G12D or Q61R, coded with native rare or common codons to induce low or high protein expression to separate these two types of signaling. These alleles were crossed into a Rosa26-CreER background and globally activated, revealing tissues sensitive to quantitative signaling regulated by the RAS biochemical activity, qualitative signaling regulated by the specific mutation, and either both or none of these two types of signaling. Bulk RNAseq analysis further revealed that each allele induced a different cellular response, with the weakest allele induce transcriptional features of a plastic state while the strongest allele had all the transcriptional hallmarks of high oncogenic signaling and a stress response. In conclusion, this approach provides a mutational atlas of tissues dependent upon quantitative signaling, qualitative signaling, or both forms of signaling for tumorigenesis, as well as tissues generally resistant to oncogenic RAS. This tissue atlas can thus serve to define how specific cancers are initiated, and in turn, how to prevent such initiation events from taking hold to lead a normal cell down the path of tumorigenesis, which has important clinical implications for early cancer detection and prevention measures.

Citation Format: Ozgun Erdogan, Christopher Counter. A tissue atlas of oncogenic RAS mutation [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 2195.

β-Cell and renal transplantation options for diabetes

Despite major advances in structured education, insulin delivery and glucose monitoring, diabetes self-management remains an unremitting challenge. Insulin therapy is inextricably linked to risk of dangerous hypoglycaemia and sustained hyperglycaemia remains a leading cause of renal failure. This review sets out to demystify transplantation for diabetes multidisciplinary teams, facilitating consideration and incorporation within holistic overall person-centred management. Deceased and living donor kidney, whole pancreas and isolated islet transplant procedures, indications and potential benefits are described, in addition to outcomes within the integrated UK transplant programme.

Codon usage regulates human KRAS expression at both transcriptional and translational levels

KRAS and HRAS are highly homologous oncogenic Ras GTPase family members that are mutated in a wide spectrum of human cancers. Despite having high amino acid identity, KRAS and HRAS have very different codon usage biases: the HRAS gene contains many common codons, and KRAS is enriched for rare codons. Rare codons in KRAS suppress its protein expression, which has been shown to affect both normal and cancer biology in mammals. Here, using HRAS or KRAS expression in different human cell lines and in vitro transcription and translation assays, we show that KRAS rare codons inhibit both translation efficiency and transcription and that the contribution of these two processes varies among different cell lines. We observed that codon usage regulates mRNA translation efficiency such that WT KRAS mRNA is poorly translated. On the other hand, common codons increased transcriptional rates by promoting activating histone modifications and recruitment of transcriptional coactivators. Finally, we found that codon usage also influences KRAS protein conformation, likely because of its effect on co-translational protein folding. Together, our results reveal that codon usage has multidimensional effects on protein expression, ranging from effects on transcription to protein folding in human cells.

Copper chelation as targeted therapy in a genetic mouse model of oncogenic BRAF-driven thyroid cancer

e23148

Background: Over half of papillary thyroid cancers (PTC) contain the MAPK pathway activating, oncogenic BRAF V600E mutation. Early clinical trials using inhibitors to this mutant protein or its substrates, the MEK1/2 kinases, prolonged progression-free survival or stabilized disease in patients with advanced PTC. However, the toxicities of these inhibitors are uniquely highlighted in an indolent disease like PTC, which would require patients to endure toxicities long-term. Our goal was to determine if tetrathimoybdate (TM), a well-tolerated copper chelator we have previously shown to inhibit BRAF-mutated melanoma via MEK inhibition, can inhibit BRAF-driven PTC growth. Methods: We assessed TM in comparison to current standard of care (SOC), Lenvatinib and Sorafenib, and mutant BRAF inhibitor, Vemurafenib. Anchorage independent growth assays were used to test the inhibitory effect of these drugs on human BRAF-mutated PTC cell lines. We then confirmed these findings by treating a genetically engineered mouse model (GEMM) of aggressive BRAF-driven PTC. Results: TM inhibited 57.5% of colony growth in vitro, which was not significantly different from the 42.4% and 32.2% inhibition by Sorafenib and Lenvatinib, respectively. TM inhibition was less effective than the 70.3% inhibition by Vemurafenib ( p =0.04). We confirmed these results in vivo, where mice on the TM arm, on average, were observed to have 14.8% of their thyroid glands occupied by tumor, a statistically significant reduction from the mice in the control arm, whose tumor load averaged 23.6% ( p= 0.008). This 37.4% reduction in tumor burden was not statistically different from the 35.2% reduction measured in the Vemurafenib arm, where mice on average had 15.3% of their thyroid glands replaced by tumor. Conclusions: The copper chelator, TM, was as effective as the SOCs, Lenvatinib and Sorafenib, at inhibiting the growth of human PTC in vitro. Although TM was slightly less effective than Vemurafenib in vitro, TM was as effective as Vemurafenib at reducing tumor load in a GEMM of BRAF-driven PTC. Success of TTM in these PTC models may next inform a Phase I trial assessing TM in patients with advanced PTC.

Abstract B03: A whole genome screening platform to identify genes that overcome the poor translation of KRAS

We discovered that KRAS mRNA is highly enriched in rare codons, which limited translation of the encoded KRAS protein. Accumulating evidence suggests that there is a selective pressure during tumorigenesis to overcome the poor translation of KRAS imposed by rare codons to produce more oncogenic protein and promote more malignant phenotypes. To identify how cancer cells achieve this feat, we are screening whole genome gain- and loss-of-function libraries for genes capable of increasing the translation of a rare-codon enriched fluorescent reporter. More specifically, we have created a reporter cell line encoding a rare-codon enriched GFP and a common-codon enriched mCherry protein. Normalizing to mCherry expression, we further demonstrate that FACS can effectively isolate cells expressing a common-codon enriched GFP from those expressing the rare codon counterpart. Given this, the reporter line was stably infected with a CRISPR library targeting 19,050 genes and sorted by FACS for those expressing high levels of GFP, with these cells now being subjected to deep sequencing. A whole genome ORF library is being screened in an identical fashion. In the future, we will rescreen candidate CRISPRs or ORFs identified from these screens, and those that reproducibly increase the expression of the rare-codon enriched reporter will be analyzed further, especially with regards to the underlying mechanism and expression in cancer cells.

Citation Format: Jackson J. Peterson, Erin Kaltenbrun, Christopher Counter. A whole genome screening platform to identify genes that overcome the poor translation of KRAS. [abstract]. In: Proceedings of the AACR Special Conference on Translational Control of Cancer: A New Frontier in Cancer Biology and Therapy; 2016 Oct 27-30; San Francisco, CA. Philadelphia (PA): AACR; Cancer Res 2017;77(6 Suppl):Abstract nr B03.

Abstract A52: KRAS: The Rarefied Ras Oncogene

The Ras family of small GTPases is comprised of three isoforms, HRAS, NRAS and KRAS, which are mutated in up to a third of all human cancers to promote tumorigenesis. Despite nearly identical amino acid sequence, we discovered divergent codon usage between isoform mRNA sequences. Specifically, KRAS is enriched in underrepresented (rare) codons relative to mammalian transcripts, whereas HRAS is characterized by common codons and NRAS is composed of an intermediate codon mixture. Rare codons can limit protein expression, and we tested and found that successively changing rare to common codons increased KRAS protein expression. To determine the impact of rare codon bias on KRAS-driven carcinogenesis, we converted rare to common codons in exon 3 of the endogenous Kras gene, then treated heterozygous Krasex3op/wt mice with the carcinogen urethane to induce Kras mutation-positive lung tumors. We now report that the multiplicity of tumors in these Krasex3op/wt mice was significantly reduced, and only weaker oncogenic mutations were detected in the Krasex3op allele compared to the Kraswt allele. Since high oncogenic RAS expression can induce a senescent growth arrest instead of transformation to a tumorigenic state, we hypothesized that converting rare to common codons in Kras to increase protein expression may augment senescence in response to activating mutations. Indeed, ectopic expression of oncogenic Krasex3op induced a stronger growth arrest in cultured cells than the oncogenic version of the native Kras. In summary, we have identified a novel regulatory mechanism hard-wired into the RAS genes that has a direct impact on tumorigenesis.

Citation Format: Nicole L. Pershing, Benjamin Lampson, Christopher Counter. KRAS: The Rarefied Ras Oncogene. [abstract]. In: Proceedings of the AACR Special Conference on RAS Oncogenes: From Biology to Therapy; Feb 24-27, 2014; Lake Buena Vista, FL. Philadelphia (PA): AACR; Mol Cancer Res 2014;12(12 Suppl):Abstract nr A52. doi: 10.1158/1557-3125.RASONC14-A52

Abstract 1573: An inducible transgenic porcine model for human cancer

Common rodent-based models have limitations in terms of modeling human cancers. Given that pigs share many genetic and physiological similarities with humans, we investigated the potential of developing genetic porcine models of cancer. In this regard, we previously reported that activation of oncogenes like Ras in conjunction with inhibiting tumor suppressor pathways like p53 were required, in part, to convert normal porcine cells to a tumorigenic state. Based on this, we chose to generate transgenic pigs that can be induced to express oncogenic Kras and dominant-negative p53. First, porcine Kras and p53 wild-type genes were cloned, sequenced and aligned with porcine, human and murine homologues to identify porcine-specific mutation sites corresponding to those commonly found in human cancers. Porcine Kras mutation occurs at the 12th glycine (G) to aspartic acid (D), whereas p53 arginine (R) at 167th position was mutated to histidine (H). KrasG12D and p53R167H mutants were linked by internal ribosome entry sites (IRES) for their simultaneous expression and then inserted into a vector following the LoxP-polyA(STOP)-LoxP sequence (LSL). Porcine fetal fibroblasts were transfected in vitro with this vector construct and infected by adenovirus (Ad) vectors encoding Cre recombinase (Ad-Cre-GFP), which deletes the LSL sequence and permits transgene expression, or control Ad vectors without the inserted Cre transgene (Ad-GFP). Cre recombinase-mediated KrasG12D and p53R167H expression was significantly induced in porcine fibroblasts transfected with Ad-Cre-GFP virus compared with Ad-GFP control, which provides an in vitro proof of functional test of the “oncopig” construct. We then transfected porcine fibroblasts with the aforementioned “oncopig” construct to produce donor cell lines for nuclear transfer cloning. Transgenic fibroblast cell lines generated from the cloned pig were subjected to a wound assay through which we observed a statistically significant difference of in vitro migration capability between Ad-Cre-GFP cells and Ad-GFP control cells. In a migration time of 24h, the number of cells in the wound area for the Ad-Cre-GFP cells was 184 as for the Ad-GFP cells was only 67 (p-value ≤ 0.01). A statistically significant difference was also observed between the cell cycle length for these cell lines by flow cytometry. Ad-Cre-GFP cells went through a greater number of cell divisions compared with Ad-GFP cells. Within a 73h time period, Ad-Cre-GFP cells divided twice as many times than Ad-GFP cells (p-value ≤ 0.01). Present results demonstrate that induction of the transgenes in these porcine cells triggered a transformed phenotype. In the future, these cells will be tested for growth in soft agar, tumor growth in mice, and then the pigs will be monitored for tumor incidence following site-specific transgene induction. Such an approach could provide a porcine model to cancer etiology and the development of anti-cancer therapy.

Citation Format: Fernanda M. Rodrigues, Wenping Hu, Laurie Rund, Ying Liang, Christopher Counter, Lawrence Schook. An inducible transgenic porcine model for human cancer. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 1573. doi:10.1158/1538-7445.AM2013-1573

How safe is it to transplant organs from deceased donors with primary intracranial malignancy? An analysis of UK Registry data

Patients dying from primary intracranial malignancy are a potential source of organs for transplantation. However, a perceived risk of tumor transfer to the organ recipient has limited their use. We evaluated the risk of tumor transmission by reviewing the incidence in patients transplanted in the UK. Information from the UK Transplant Registry was combined with that from the national cancer registries of England, Wales and Northern Ireland to identify all organ donors between 1985 and 2001 inclusive with a primary intracranial malignancy and to identify the occurrence of posttransplant malignancy in the recipients of the organs transplanted. Of 11,799 organ donors in the study period, 179 were identified as having had a primary intracranial malignancy, including 33 with high-grade malignancy (24 grade IV gliomas and 9 medulloblastomas). A total of 448 recipients of 495 organs from 177 of these donors were identified. No transmission of donor intracranial malignancy occurred. Organs from patients dying from primary intracranial malignancy, including those with high-grade tumors, should be considered for transplantation and the small risk of tumor transmission should be balanced against the likely mortality for potential recipients who remain on the transplant waiting list.

The MEK pathway is required for stimulation of p21(WAF1/CIP1) by transforming growth factor-beta

Transforming growth factor-beta (TGF-beta)can induce the cyclin-dependent kinase inhibitors p21 and p15 in a variety of cell types. We have shown previously that Smad3 is required for the growth inhibitory activity of TGF-beta, whereas overexpression of Smads is not sufficient to activate the expression of p21 in HaCaT cells. These data suggest that an additional signaling pathway may be involved in stimulating p21 in HaCaT cells. Given the recent finding that the mitogen-activated protein kinase (MAPK) pathway can cause p21 induction and arrest cells, we examined the involvement of this pathway for p21 and p15 induction by TGF-beta. We found that TGF-beta can regulate the MAPK pathway, leading to the increased transactivation ability of transcription factor Elk. Constitutively active components in the MAPK pathway activate p21 expression, and inhibitors or dominant negative constructs for the MAPK pathway significantly decrease p21 induction by TGF-beta. Both constitutively active MEK and inhibitors for MEK have no effect on Smad activity, including DNA binding, localization, and interaction with coactivator p300/CBP. These findings suggest that the MAPK pathway may be an independent pathway that is involved in p21 and p15 induction by TGF-beta.

Characterization of the repeat-tract instability and mutator phenotypes conferred by a Tn3 insertion in RFC1, the large subunit of the yeast clamp loader

The RFC1 gene encodes the large subunit of the yeast clamp loader (RFC) that is a component of eukaryotic DNA polymerase holoenzymes. We identified a mutant allele of RFC1 (rfc1::Tn3) from a large collection of Saccharomyces cerevisiae mutants that were inviable when present in a rad52 null mutation background. Analysis of rfc1::Tn3 strains indicated that they displayed both a mutator and repeat-tract instability phenotype. Strains bearing this allele were characterized in combination with mismatch repair (msh2Delta, pms1Delta), double-strand break repair (rad52), and DNA replication (pol3-01, pol30-52, rth1Delta/rad27Delta) mutations in both forward mutation and repeat-tract instability assays. This analysis indicated that the rfc1::Tn3 allele displays synthetic lethality with pol30, pol3, and rad27 mutations. Measurement of forward mutation frequencies in msh2Delta rfc1:Tn3 and pms1Delta rfc1:Tn3 strains indicated that the rfc1::Tn3 mutant displayed a mutation frequency that appeared nearly multiplicative with the mutation frequency exhibited by mismatch-repair mutants. In repeat-tract instability assays, however, the rfc1::Tn3 mutant displayed a tract instability phenotype that appeared epistatic to the phenotype displayed by mismatch-repair mutants. From these data we propose that defects in clamp loader function result in DNA replication errors, a subset of which are acted upon by the mismatch-repair system.

Telomeres and telomerase in human cancer (review)

Telomerase has recently come into the limelight as one of the most prevalent tumour markers, due to its nearly ubiquitous presence in malignant tissues and absence from most somatic tissues. The essential role of telomeres in unlimited cell proliferation and that of the enzyme in telomere maintenance have suggested that telomerase inhibitors may be effective in cancer therapy. We provide here a compendium and an evaluation of the available data relating to this hypothesis.