Recurrent RhoGAP gene fusion CLDN18-ARHGAP26 promotes RHOA activation and focal adhesion kinase and YAP-TEAD signalling in diffuse gastric cancer

OBJECTIVE

Genomic studies of gastric cancer have identified highly recurrent genomic alterations impacting RHO signalling, especially in the diffuse gastric cancer (DGC) histological subtype. Among these alterations are interchromosomal translations leading to the fusion of the adhesion protein CLDN18 and RHO regulator ARHGAP26. It remains unclear how these fusion constructs impact the activity of the RHO pathway and what is their broader impact on gastric cancer development. Herein, we developed a model to allow us to study the function of this fusion protein in the pathogenesis of DGC and to identify potential therapeutic targets for DGC tumours with these alterations.

DESIGN

We built a transgenic mouse model with LSL-CLDN18-ARHGAP26 fusion engineered into the Col1A1 locus where its expression can be induced by Cre recombinase. Using organoids generated from this model, we evaluated its oncogenic activity and the biochemical effects of the fusion protein on the RHOA pathway and its downstream cell biological effects in the pathogenesis of DGC.

RESULTS

We demonstrated that induction of CLDN18-ARHGAP26 expression in gastric organoids induced the formation of signet ring cells, characteristic features of DGC and was able to cooperatively transform gastric cells when combined with the loss of the tumour suppressor geneTrp53. CLDN18-ARHGAP26 promotes the activation of RHOA and downstream effector signalling. Molecularly, the fusion promotes activation of the focal adhesion kinase (FAK) and induction of the YAP pathway. A combination of FAK and YAP/TEAD inhibition can significantly block tumour growth.

CONCLUSION

These results indicate that the CLDN18-ARHGAP26 fusion is a gain-of-function DGC oncogene that leads to activation of RHOA and activation of FAK and YAP signalling. These results argue for further evaluation of emerging FAK and YAP-TEAD inhibitors for these deadly cancers.

RHOAL57V drives the development of diffuse gastric cancer through IGF1R-PAK1-YAP1 signaling

Cancer-associated mutations in the guanosine triphosphatase (GTPase) RHOA are found at different locations from the mutational hotspots in the structurally and biochemically related RAS. Tyr42-to-Cys (Y42C) and Leu57-to-Val (L57V) substitutions are the two most prevalent RHOA mutations in diffuse gastric cancer (DGC). RHOAY42C exhibits a gain-of-function phenotype and is an oncogenic driver in DGC. Here, we determined how RHOAL57V promotes DGC growth. In mouse gastric organoids with deletion of Cdh1, which encodes the cell adhesion protein E-cadherin, the expression of RHOAL57V, but not of wild-type RHOA, induced an abnormal morphology similar to that of patient-derived DGC organoids. RHOAL57V also exhibited a gain-of-function phenotype and promoted F-actin stress fiber formation and cell migration. RHOAL57V retained interaction with effectors but exhibited impaired RHOA-intrinsic and GAP-catalyzed GTP hydrolysis, which favored formation of the active GTP-bound state. Introduction of missense mutations at KRAS residues analogous to Tyr42 and Leu57 in RHOA did not activate KRAS oncogenic potential, indicating distinct functional effects in otherwise highly related GTPases. Both RHOA mutants stimulated the transcriptional co-activator YAP1 through actin dynamics to promote DGC progression; however, RHOAL57V additionally did so by activating the kinases IGF1R and PAK1, distinct from the FAK-mediated mechanism induced by RHOAY42C. Our results reveal that RHOAL57V and RHOAY42C drive the development of DGC through distinct biochemical and signaling mechanisms.

Conflicts of interest in electrophysiology and devices presentations

AIMS

Industry collaboration with arrhythmia and devices research is common. However, this results in conflicts of interest (CoI) for researchers that should be disclosed. This study aimed to examine the quality of CoI disclosures in arrhythmia and devices presentations.

METHODS

Recorded presentations from the Arrhythmia & Devices section of the ESC Annual Congress 2016-2020 were assessed. The number of words, conflicts, and time displayed was documented for CoI declarations. Meta-data including sponsorship by an industry partner, presenter sex, and institution were obtained.

RESULTS

Of 1153 presentations assessed, 999 were suitable for inclusion. CoI statements were missing from 7.2% of presentations, and 58% reported ≥1 conflict. Those with conflicts spent less time-per-word on their disclosures (median 150 ms, interquartile range [IQR] 83-273 ms) compared with those without conflicts (median 250 ms, IQR 125-375 ms). One-in-eight presentations were sponsored (12.8%, n = 128). CoI statements were more likely to be missing in sponsored presentations (14.8%, n = 19) compared with non-sponsored presentations (6.1%, n = 53), P = 0.0003. Sponsored presentations contained a greater median number of CoIs (10, IQR 6-18) compared with non-sponsored sessions (1, IQR 0-5), P < 0.0001. Time-per-word spent on COI disclosures was 50% lower in sponsored sessions (125 ms, IQR 75-231 ms) compared with non-sponsored sessions (250 ms, IQR 125-375 ms), P < 0.0001.

CONCLUSION

The majority of those presenting arrhythmia and devices research have CoIs to declare. Declarations were often missing or displayed for short periods of time. Presenters in sponsored sessions, while being more conflicted, had a lower standard of declaration suggesting a higher risk of potential bias which viewers had insufficient opportunity to assess.

Functional and biological heterogeneity of KRASQ61 mutations

Missense mutations at the three hotspots in the guanosine triphosphatase (GTPase) RAS-Gly12, Gly13, and Gln61 (commonly known as G12, G13, and Q61, respectively)-occur differentially among the three RAS isoforms. Q61 mutations in KRAS are infrequent and differ markedly in occurrence. Q61H is the predominant mutant (at 57%), followed by Q61R/L/K (collectively 40%), and Q61P and Q61E are the rarest (2 and 1%, respectively). Probability analysis suggested that mutational susceptibility to different DNA base changes cannot account for this distribution. Therefore, we investigated whether these frequencies might be explained by differences in the biochemical, structural, and biological properties of KRASQ61 mutants. Expression of KRASQ61 mutants in NIH 3T3 fibroblasts and RIE-1 epithelial cells caused various alterations in morphology, growth transformation, effector signaling, and metabolism. The relatively rare KRASQ61E mutant stimulated actin stress fiber formation, a phenotype distinct from that of KRASQ61H/R/L/P, which disrupted actin cytoskeletal organization. The crystal structure of KRASQ61E was unexpectedly similar to that of wild-type KRAS, a potential basis for its weak oncogenicity. KRASQ61H/L/R-mutant pancreatic ductal adenocarcinoma (PDAC) cell lines exhibited KRAS-dependent growth and, as observed with KRASG12-mutant PDAC, were susceptible to concurrent inhibition of ERK-MAPK signaling and of autophagy. Our results uncover phenotypic heterogeneity among KRASQ61 mutants and support the potential utility of therapeutic strategies that target KRASQ61 mutant-specific signaling and cellular output.

GPCR-dependent pathways promote nanodomain-specific cAMP signaling in human cardiomyocytes, which is severely remodeled in atrial fibrillation

Funding Acknowledgements

Type of funding sources: Public grant(s) – National budget only. Main funding source(s): Deutsche Forschungsgemeinschaft, German Centre for Cardiovascular Research (DZHK)

Background

Cardiac arrhythmias, such as atrial fibrillation (AF), have been linked to the remodeling of membrane receptors and alterations in cAMP-dependent regulation of calcium handling mechanisms. For instance, decreased L-type calcium channel (LTCC) current density but upregulated ryanodine receptor 2 (RyR2) are major hallmarks of AF. Furthermore, adenosine A2A receptor (A2AR) stimulation increases calcium waves without affecting LTCC and serotonin (5-HT) receptors activation exerts stronger control over myofilaments than over RyR2 function. However, up to date no study has elucidated how the increase on cAMP upon different G-protein-coupled receptors (GPCR) stimulation can lead to different physiological compartmentalized responses. The aim of this study was to investigate the effects of various GPCRs on cAMP levels in different cellular compartments in human atrial myocytes from control patients in sinus rhythm (Ctl), and how these compartmentalized effects are altered in AF. Furthermore, alterations in downstream cAMP level control by phosphodiesterases (PDEs) between patient groups were investigated to further elucidate functional differences.

Methods

Atrial myocytes were isolated from tissues of 66 AF and 80 Ctl patients. Cells were then transduced with adenoviruses (Epac1-camps, pm-Epac1-camps and Epac1-JNC) and cultured for 48 hours to express the Förster-resonance energy transfer (FRET)-based cAMP sensor in the cytosolic, membrane and RyR2 nanodomains, respectively. FRET was then used to measure cAMP in 532 isolated human atrial myocytes. Stimulation with β-adrenergic agonist Isoprenaline (ISO, 100nM) was used and compared with 5-HT (100µM) and A2AR (with CGS, 200nM) stimulation. Additionally, a nonspecific PDE inhibitor (IBMX, 100µM) was applied, as well as PDE3 (Cilostamide, 1µM) and PDE4 (Ro 20-1724, 10µM) specific inhibitors.

Results

A desensitization to β-adrenergic receptor stimulation in AF myocytes was exclusively found in the cytosol, while no difference was seen in neither the RyR2 nor LTCC compartment in AF versus Ctl. Similar effects were observed upon 5-HT stimulation with a significant desensitization in the cytosol, and no difference in the RyR2 compartment. On the contrary, AF myocytes displayed a significantly higher increase in cAMP levels compared to Ctl myocytes in the cytosol upon A2ARs stimulation. Importantly, no effect on cAMP levels was observed in the LTCC compartment after A2ARs or 5-HT stimulation. However, PDE3 inhibition on top of 5-HT stimulation showed a significantly smaller effect on cAMP levels in AF myocytes within the LTCC compartment.

Conclusions

Collectively, our data show that cAMP levels are highly compartmentalized in human atrial myocytes and differentially regulated by different GPCRs. Furthermore, PDEs are to a certain extent responsible for the compartmentalized effects of the different GPCRs.

RHOA takes the RHOad less traveled to cancer

RAS and RHO GTPases function as signaling nodes that regulate diverse cellular processes. Whereas RAS mutations were identified in human cancers nearly four decades ago, only recently have mutations in two RHO GTPases, RAC1 and RHOA, been identified in cancer. RAS mutations are found in a diverse spectrum of human cancer types. By contrast, RAC1 and RHOA mutations are associated with distinct and restricted cancer types. Despite a conservation of RAS and RAC1 residues that comprise mutational hotspots, RHOA mutations comprise highly divergent hotspots. Whereas RAS and RAC1 act as oncogenes, RHOA may act as both an oncogene and a tumor suppressor. Thus, while RAS and RHO each take different mutational paths, they arrive at the same biological destination as cancer drivers.

Concurrent Inhibition of ERK and Farnesyltransferase Suppresses the Growth of HRAS Mutant Head and Neck Squamous Cell Carcinoma

Human papilloma virus (HPV)-negative head and neck squamous cell carcinoma (HNSCC) is a common cancer worldwide with an unmet need for more effective, less toxic treatments. Currently, both the disease and the treatment of HNSCC cause significant mortality and morbidity. Targeted therapies hold new promise for patients with HPV-negative status whose tumors harbor oncogenic HRAS mutations. Recent promising clinical results have renewed interest in the development of farnesyltransferase inhibitors (FTIs) as a therapeutic strategy for HRAS-mutant cancers. With the advent of clinical evaluation of the FTI tipifarnib for the treatment of HRAS-mutant HNSCC, we investigated the activity of tipifarnib and inhibitors of HRAS effector signaling in HRAS-mutant HNSCC cell lines. First, we validated that HRAS is a cancer driver in HRAS-mutant HNSCC lines. Second, we showed that treatment with the FTI tipifarnib largely phenocopied HRAS silencing, supporting HRAS as a key target of FTI antitumor activity. Third, we performed reverse-phase protein array analyses to profile FTI treatment-induced changes in global signaling, and conducted CRISPR/Cas9 genetic loss-of-function screens to identify previously unreported genes and pathways that modulate sensitivity to tipifarnib. Fourth, we determined that concurrent inhibition of HRAS effector signaling (ERK, PI3K, mTORC1) increased sensitivity to tipifarnib treatment, in part by overcoming tipifarnib-induced compensatory signaling. We also determined that ERK inhibition could block tipifarnib-induced epithelial-to-mesenchymal transition, providing a potential basis for the effectiveness of this combination. Our results support future investigations of these and other combination treatments for HRAS mutant HNSCC.

Outcomes of patients with severe mitral regurgitation treated with transcatheter mitral valve implantation or medical therapy

Funding Acknowledgements

Type of funding sources: None.

Background

Patients with severe mitral regurgitation (MR) unsuitable for standard therapy (i.e., open-heart surgery and transcatheter edge-to-edge repair [TEER]), often remain on medical therapy (MT) alone. Transcatheter mitral valve implantation (TMVI) may represent an alternative treatment option for these patients.

Purpose

We aimed to investigate differences in anatomical baseline characteristics and echocardiographic outcomes between MR patients unsuitable for standard therapy, that were either treated with TMVI or remained on MT.

Methods

Between 05/2016-02/2021, 121 high-risk patients with severe MR were evaluated for TMVI. Clinical, echocardiographic and functional outcomes between the subgroups of patients treated with TMVI and MT were compared. The primary combined endpoint was all-cause death or heart failure (HF) hospitalization at 1 year. Subgroup analyses were performed to define specific patient subsets favouring either TMVI or MT.

Results

At baseline, there were no differences between the TMVI group (n = 38) and the MT group (n = 44) regarding age (all TMVI vs. MT: 77.0 years [IQR 72.9, 80.1] vs. 79.0 [IQR 76.0, 81.7], p = 0.13), gender (42.1% female vs. 56.8% female, p = 0.27) and estimated surgical risk (EuroSCORE II 4.4% [IQR 2.8, 13.6] vs. 6.4 [IQR 3.4, 10.1], p = 0.72). Patients undergoing TMVI were more frequently treated for secondary MR (68.4%), while primary MR was the most prevalent MR etiology in patients remaining on medical therapy (50.0%). Left ventricular (LV) end-diastolic diameters (LVEDD) were larger and LV ejection fraction (LVEF) was lower in the TMVI group (LVEDD 58.0mm [IQR 51.4, 65.0], LVEF 37.0% [IQR 31.4, 51.2]) compared to the MT group (LVEDD 52.0mm [IQR 46.2, 58.8], LVEF 54.5% [IQR 40.8, 60.0]) (p = 0.02 for LVEDD, p &lt; 0.001 for LVEF). MR was effectively reduced to ≤ mild MR in all patients undergoing TMVI. In the MT group, MR remained severe in 90% of patients after 1 year. The primary composite endpoint occurred numerically more often in the MT group (72.2%) compared to the TMVI group (51.6%, p = 0.061). Regarding the primary endpoint, the subgroups of patients with LVEF 30-49% (HR 0.28 [95%-CI 0.11-0.67], p = 0.004), effective regurgitant orifice area (EROA) &lt;0.4 cm2 (HR 0.30 [95%-CI 0.13-0.71], p = 0.006), tricuspid annular plane systolic excursion (TAPSE) ≥17mm (HR 0.27 [95%-CI 0.11-0.67], p = 0.005) and New York Heart Association functional class III (HR 0.38 [95%-CI 0.18-0.81], p = 0.012) were more likely to benefit from TMVI compared to MT.

Conclusions

In patients with severe MR unsuitable for standard therapy, TMVI represents a reasonable therapeutic alternative yielding effective elimination of MR. While most patients eligible for TMVI suffer from secondary MR, the majority of patients remaining on MT has primary MR. The primary endpoint occurred numerically, yet not statistically, more often in patients on MT. Baseline echocardiography was able to identify subgroups of patients with beneficial outcome after TMVI.

Aberrant Expression and Subcellular Localization of ECT2 Drives Colorectal Cancer Progression and Growth

ECT2 is an activator of RHO GTPases that is essential for cytokinesis. In addition, ECT2 was identified as an oncoprotein when expressed ectopically in NIH/3T3 fibroblasts. However, oncogenic activation of ECT2 resulted from N-terminal truncation, and such truncated ECT2 proteins have not been found in patients with cancer. In this study, we observed elevated expression of full-length ECT2 protein in preneoplastic colon adenomas, driven by increased ECT2 mRNA abundance and associated with APC tumor-suppressor loss. Elevated ECT2 levels were detected in the cytoplasm and nucleus of colorectal cancer tissue, suggesting cytoplasmic mislocalization as one mechanism of early oncogenic ECT2 activation. Importantly, elevated nuclear ECT2 correlated with poorly differentiated tumors, and a low cytoplasmic:nuclear ratio of ECT2 protein correlated with poor patient survival, suggesting that nuclear and cytoplasmic ECT2 play distinct roles in colorectal cancer. Depletion of ECT2 reduced anchorage-independent cancer cell growth and invasion independent of its function in cytokinesis, and loss of Ect2 extended survival in a Kras G12D Apc-null colon cancer mouse model. Expression of ECT2 variants with impaired nuclear localization or guanine nucleotide exchange catalytic activity failed to restore cancer cell growth or invasion, indicating that active, nuclear ECT2 is required to support tumor progression. Nuclear ECT2 promoted ribosomal DNA transcription and ribosome biogenesis in colorectal cancer. These results support a driver role for both cytoplasmic and nuclear ECT2 overexpression in colorectal cancer and emphasize the critical role of precise subcellular localization in dictating ECT2 function in neoplastic cells. SIGNIFICANCE: ECT2 overexpression and mislocalization support its role as a driver in colon cancer that is independent from its function in normal cell cytokinesis.

Diagnostic value and prognostic impact of various invasively derived hemodynamic parameters in patients with severe aortic stenosis undergoing TAVI

Background

Ejection time (ET) and Acceleration time (AT) have been described as echocardiographic markers for aortic stenosis (AS).1 Moreover, in a recent study time between invasively measured left ventricular and aortic systolic pressure peaks (T-LVAo) was associated with anatomic AS severity.2 However, the diagnostic value of these parameters has not been validated in a larger patient cohort and their prognostic impact in AS patients undergoing transcatheter aortic valve implantation (TAVI) remains unknown.

Purpose

We aimed to assess the diagnostic value and prognostic impact of ET, AT, and T-LVAo as assessed by invasive measurements in patients undergoing TAVI for severe AS.

Methods

This retrospective single-centre analysis studied 1478 patients undergoing TAVI from 2014 to 2019 for severe AS. All patients received echocardiographic, multislice computed tomography (MSCT) and invasive hemodynamic evaluation with simultaneous pressure measurements in left ventricle and aorta prior to TAVI. Anatomic AS severity was assessed according to MSCT-derived aortic valve calcification density (AVCd) defined as calcium volume per annulus area. All hemodynamic parameters were calculated offline using a dedicated software.

Results

Median patients' age was 81.2 (76.8–84.7) years and 807 (54.6%) were women. Predicted operative risk for mortality was 3.8 (2.6–5.7)% according to STS Score. Medians of invasively derived parameters were 70.0 ms (46.0–98.0) for T-LVAo, 308.0 ms (276.0–336.0) for ET, 180.0 ms (146.0–206.0) for AT. In spline analysis correlation of T-LVAo (Spearman: r=0.35; p&lt;0.001) and ET (Spearman: r=0.18; p&lt;0.001) with AVCd was significant but weak. AT showed negligible correlation with ACVd (Spearman: r=−0.05; p=0.089). The optimal cutoff for death (CD) according to C-statistic was 274 ms for ET and 158 ms for AT. Patients with ET or AT ≥ CD showed lower short and mid-term mortality rates compared to patients with ET or AT &lt; CD (ET ≥ vs. &lt; CD: mortality at 1-year: 14.5 vs. 31.9%, 3-years: 28.3 vs. 53.5%, all p&lt;0.001; AT ≥ vs &lt; CD: mortality at 1-year: 15.5 vs. 25.9%, p&lt;0.001, 3-years: 34.0 vs. 41.0%, p=0.0032). Moreover, multivariate analysis for mortality identified ET (HR 0.58 [95% CI 0.43–0.77; p&lt;0.001]) and AT (HR 0.65 [95% CI 0.49–0.86; p=0.0027]) to be associated with beneficial outcome after TAVI, independent from clinical risk factors and echocardiography-derived parameters like LVEF, mean gradient or stroke volume index. In contrast, T-LVAo showed no prognostic impact according to uni- or multivariate analyses.

Conclusion

T-LVAo provides the highest diagnostic value among the investigational hemodynamic parameters, however correlation with AVCd was weak. ET and AT are strong independent outcome predictors beyond clinical risk factors and standard echocardiographic parameters in AS patients following TAVI. Accordingly, use of ET and AT might improve risk assessment in patients scheduled for TAVI.

Funding Acknowledgement

Type of funding sources: None.

Targeting p130Cas- and microtubule-dependent MYC regulation sensitizes pancreatic cancer to ERK MAPK inhibition

To identify therapeutic targets for KRAS mutant pancreatic cancer, we conduct a druggable genome small interfering RNA (siRNA) screen and determine that suppression of BCAR1 sensitizes pancreatic cancer cells to ERK inhibition. Integrative analysis of genome-scale CRISPR-Cas9 screens also identify BCAR1 as a top synthetic lethal interactor with mutant KRAS. BCAR1 encodes the SRC substrate p130Cas. We determine that SRC-inhibitor-mediated suppression of p130Cas phosphorylation impairs MYC transcription through a DOCK1-RAC1-β-catenin-dependent mechanism. Additionally, genetic suppression of TUBB3, encoding the βIII-tubulin subunit of microtubules, or pharmacological inhibition of microtubule function decreases levels of MYC protein in a calpain-dependent manner and potently sensitizes pancreatic cancer cells to ERK inhibition. Accordingly, the combination of a dual SRC/tubulin inhibitor with an ERK inhibitor cooperates to reduce MYC protein and synergistically suppress the growth of KRAS mutant pancreatic cancer. Thus, we demonstrate that mechanistically diverse combinations with ERK inhibition suppress MYC to impair pancreatic cancer proliferation.

Does industry funding differ between men and women in electrophysiology and devices research?

Funding Acknowledgements

Type of funding sources: None.

Background

A significant gender bias has been identified in cardiology. Industry funding may be important developing electrophysiology (EP) and devices research. Such funding leads to potential conflicts of interest (COI) which must be disclosed on research presentations. There is limited evidence whether the gender bias in cardiology extends to industry funding of research.

Purpose

To assess whether COI disclosures in EP and devices presentations at the ESC Annual Congress differ between men and women.

Methods

Recorded presentations from the Arrhythmia & Devices section of ESC Annual Congresses 2016-2020 were assessed. Presentations were excluded if the original presentation contained no slides, it was a panel discussion, it was a non-scientific presentation, or part of the presentation was missing. Presentations with multiple speakers were also excluded. Chi-squared and Mann-Whitney U tests were used to assess differences between groups for dichotomous and continuous data respectively.

Results

Of 1,153 presentations assessed, 999 were suitable for inclusion. Women made up 22% (n = 221) of presenters. There was no difference in whether COI declaration slides were missing between women (5.9%, n = 13) and men (7.6%, n = 56), p = 0.38. In those with COI disclosure slides (n = 927), women declared significantly lower median number of COIs (0, IQR 0-3) compared with men (2, IQR 0-8), p &lt; 0.0001. In contrast, women spent a greater time-per-word on their COI disclosure slides (250ms, IQR 125-375ms) compared with men (200ms, IQR 118-333ms), p &lt; 0.0001.

Conclusions

Women made up a minority of presenters in EP/devices talks at the ESC annual congress. Women were less likely to have COIs which may suggest that they are less likely to receive industry funding. Despite this, women spent a greater amount of time-per-word on their COI slides. The lower number of declared COIs in women highlights another potential area of gender bias in cardiology that needs further investigation so that it can be addressed.

Prevalence and prognostic impact of left ventricular outflow tract calcification in patients with severe aortic stenosis undergoing transfemoral TAVI using second-generation devices

Introduction

Left ventricular outflow tract (LVOT) calcification is known to be associated with adverse outcomes after TAVI in patients receiving first-generation transcatheter heart valves (THV). Second-generation THV have been shown to improve outcomes of TAVI patients. Thus, aim of this study is to assess the prevalence of LVOT calcification as well as its impact on procedural and clinical outcomes in patients with severe aortic stenosis undergoing transfemoral TAVI with second-generation THV in a real-world patient cohort.

Methods

In this retrospective single-center analysis patients receiving transfemoral TAVI with second-generation THV for the treatment of aortic stenosis (AS) between 05/2012 and 06/2018 and with adequate CT data were included (n=836). Amount of LVOT calcification was measured quantitatively from contrast-enhanced multislice CT using a dedicated software. Baseline characteristics and outcomes were compared according to presence of significant LVOT calcification (none/≤10 mm3 vs. &gt;10 mm3). Procedural and clinical outcome were assessed in accordance with VARC-2 criteria. All-cause mortality was assessed by Kaplan-Meier method, median follow-up was 1.4 years.

Results

Significant LVOT calcification was present in 37.0% of patients. Patients with LVOT calcification were older (all results as follows without (w/o) vs. with (w) LVOT calcification: 81.4 (77.1, 84.8) vs. 82.3 (78.0, 86.3) years, p=0.006), but presented similar STS scores compared to those without LVOT calcification (5.4±4.7 vs. 5.4±3.5%, p=0.94). Moreover, patients with LVOT calcification had higher mean transvalvular gradients at baseline (30.0 (21.0, 41.0) vs. 37.0 (25.7, 47.0) mmHg, p&lt;0.001) and higher aortic valve calcium volume (380.7 (226.8, 632.1) vs. 663.6 (364.5, 1070.3) mm3, p&lt;0.001). There were no significant differences in rate of device success (97.0 vs. 94.2%, p=0.11), renal failure (2.6 vs. 2.3%, p=1.00), myocardial infarction (0.9 vs. 1.2%, p=1.00) or rate of permanent pacemaker implantation at 30 days after TAVI (16.6 vs. 17.2%, p=0.91). However, rate of TIA/stroke was significantly higher in patients with LVOT calcification (2.1 vs. 6.2%, p=0.0098). Furthermore, patients with LVOT calcification had a higher rate of more than mild paravalvular leakage at discharge (3.8 vs. 7.6%, p=0.033). Rate of 1 year all-cause mortality (17.8 vs. 21.2%, p=0.23) was not significantly different between both groups.

Conclusions

Significant LVOT calcification is present in a substantial proportion of patients receiving TAVI. In such patients, higher rates of cerebrovascular events and more than mild PVL occurred compared to those without significant LVOT calcification even with currently available second-generation THV. Although these findings did not translate into higher mortality rates in the present study, they underline the need for further optimization of THV technology in order to improve outcomes among all TAVI patients.

Figure 1. 1-year mortality

Funding Acknowledgement

Type of funding source: None

RAS and RHO family GTPase mutations in cancer: twin sons of different mothers?

The RAS and RHO family comprise two major branches of the RAS superfamily of small GTPases. These proteins function as regulated molecular switches and control cytoplasmic signaling networks that regulate a diversity of cellular processes, including cell proliferation and cell migration. In the early 1980s, mutationally activated RAS genes encoding KRAS, HRAS and NRAS were discovered in human cancer and now comprise the most frequently mutated oncogene family in cancer. Only recently, exome sequencing studies identified cancer-associated alterations in two RHO family GTPases, RAC1 and RHOA. RAS and RHO proteins share significant identity in their amino acid sequences, protein structure and biochemistry. Cancer-associated RAS mutant proteins harbor missense mutations that are found primarily at one of three mutational hotspots (G12, G13 and Q61) and have been identified as gain-of-function oncogenic alterations. Although these residues are conserved in RHO family proteins, the gain-of-function mutations found in RAC1 are found primarily at a distinct hotspot. Unexpectedly, the cancer-associated mutations found with RHOA are located at different hotspots than those found with RAS. Furthermore, since the RHOA mutations suggested a loss-of-function phenotype, it has been unclear whether RHOA functions as an oncogene or tumor suppressor in cancer development. Finally, whereas RAS mutations are found in a broad spectrum of cancer types, RHOA and RAC1 mutations occur in a highly restricted range of cancer types. In this review, we focus on RHOA missense mutations found in cancer and their role in driving tumorigenesis, with comparisons to cancer-associated mutations in RAC1 and RAS GTPases.

The molecular basis for immune dysregulation by the hyperactivated E62K mutant of the GTPase RAC2

The RAS-related C3 botulinum toxin substrate 2 (RAC2) is a member of the RHO subclass of RAS superfamily GTPases required for proper immune function. An activating mutation in a key switch II region of RAC2 (RAC2E62K) involved in recognizing modulatory factors and effectors has been identified in patients with common variable immune deficiency. To better understand how the mutation dysregulates RAC2 function, we evaluated the structure and stability, guanine nucleotide exchange factor (GEF) and GTPase-activating protein (GAP) activity, and effector binding of RAC2E62K Our findings indicate the E62K mutation does not alter RAC2 structure or stability. However, it does alter GEF specificity, as RAC2E62K is activated by the DOCK GEF, DOCK2, but not by the Dbl homology GEF, TIAM1, both of which activate the parent protein. Our previous data further showed that the E62K mutation impairs GAP activity for RAC2E62K As this disease mutation is also found in RAS GTPases, we assessed GAP-stimulated GTP hydrolysis for KRAS and observed a similar impairment, suggesting that the mutation plays a conserved role in GAP activation. We also investigated whether the E62K mutation alters effector binding, as activated RAC2 binds effectors to transmit signaling through effector pathways. We find that RAC2E62K retains binding to an NADPH oxidase (NOX2) subunit, p67phox, and to the RAC-binding domain of p21-activated kinase, consistent with our earlier findings. Taken together, our findings indicate that the RAC2E62K mutation promotes immune dysfunction by promoting RAC2 hyperactivation, altering GEF specificity, and impairing GAP function yet retaining key effector interactions.

Low-Dose Vertical Inhibition of the RAF-MEK-ERK Cascade Causes Apoptotic Death of KRAS Mutant Cancers

We address whether combinations with a pan-RAF inhibitor (RAFi) would be effective in KRAS mutant pancreatic ductal adenocarcinoma (PDAC). Chemical library and CRISPR genetic screens identify combinations causing apoptotic anti-tumor activity. The most potent combination, concurrent inhibition of RAF (RAFi) and ERK (ERKi), is highly synergistic at low doses in cell line, organoid, and rat models of PDAC, whereas each inhibitor alone is only cytostatic. Comprehensive mechanistic signaling studies using reverse phase protein array (RPPA) pathway mapping and RNA sequencing (RNA-seq) show that RAFi/ERKi induced insensitivity to loss of negative feedback and system failures including loss of ERK signaling, FOSL1, and MYC; shutdown of the MYC transcriptome; and induction of mesenchymal-to-epithelial transition. We conclude that low-dose vertical inhibition of the RAF-MEK-ERK cascade is an effective therapeutic strategy for KRAS mutant PDAC.

Abstract A29: The gastric cancer-associated mutations R5W and Y42C in the RAS homologous RHOA protein cause distinct biochemical alterations, exhibit gain-of-function signaling and oncogenic activities

Missense mutations of the RAS homologous RHOA gene have recently been identified in ~25% of diffuse gastric cancer (DGC). Unexpectedly, in contrast to the gain-of-function hotspot mutations found in RAS in cancer, DGC-associated RHOA mutations (e.g., R5W, Y42C) are localized at different hotspots that instead suggest loss-of-function alterations. First, we utilized bacterially expressed recombinant proteins and determined the biochemical consequences of these mutations on RHOA function. We found that RHOA WT and Y42C, but not R5W nucleotide exchange, was catalyzed by the ECT2 RhoGEF. Similarly, WT and Y42C, but not R5W GTP hydrolysis activity, was stimulated by the p190RhoGAP. Surprisingly, Y42C and to a lesser degree R5W exhibited impaired intrinsic GTP hydrolysis activity. Interestingly, Y42C showed both loss- and gain-of-function interaction with effectors. Second, we ectopically expressed WT and mutant RHOA proteins in NIH/3T3 fibroblast, and surprisingly, found that Y42C and R5W, similar to the lab-generated constitutively GTP-bound Q63L mutant (analogous to RAS Q61L), stimulated actin stress fiber formation and focal adhesion assembly. Finally, when ectopically expressed in beta-catenin-deficient (another mutation found in gastric cancer) mouse gastric organoids, Y42C disrupted the 3D architecture and induced a DGC-like phenotype in vitro and in vivo. In summary, our studies suggest mutation-specific biochemical defects that act as gain-of-function oncogenic RHOA mutations.

Citation Format: Antje Schaefer, Richard G. Hodge, Devon R. Blake, Haisheng Zhang, Adam J. Bass, Channing J. Der. The gastric cancer-associated mutations R5W and Y42C in the RAS homologous RHOA protein cause distinct biochemical alterations, exhibit gain-of-function signaling and oncogenic activities [abstract]. In: Proceedings of the AACR Special Conference on Targeting RAS-Driven Cancers; 2018 Dec 9-12; San Diego, CA. Philadelphia (PA): AACR; Mol Cancer Res 2020;18(5_Suppl):Abstract nr A29.

Gain-of-Function RHOA Mutations Promote Focal Adhesion Kinase Activation and Dependency in Diffuse Gastric Cancer

Diffuse gastric cancer (DGC) is a lethal malignancy lacking effective systemic therapy. Among the most provocative recent results in DGC has been that of highly recurrent missense mutations in the GTPase RHOA. The function of these mutations has remained unresolved. We demonstrate that RHOA^Y42C, the most common RHOA mutation in DGC, is a gain-of-function oncogenic mutant, and that expression of RHOA^Y42C with inactivation of the canonical tumor suppressor Cdh1 induces metastatic DGC in a mouse model. Biochemically, RHOA^Y42C exhibits impaired GTP hydrolysis and enhances interaction with its effector ROCK. RHOA ^Y42C mutation and Cdh1 loss induce actin/cytoskeletal rearrangements and activity of focal adhesion kinase (FAK), which activates YAP-TAZ, PI3K-AKT, and β-catenin. RHOA^Y42C murine models were sensitive to FAK inhibition and to combined YAP and PI3K pathway blockade. These results, coupled with sensitivity to FAK inhibition in patient-derived DGC cell lines, nominate FAK as a novel target for these cancers. SIGNIFICANCE: The functional significance of recurrent RHOA mutations in DGC has remained unresolved. Through biochemical studies and mouse modeling of the hotspot RHOA^Y42C mutation, we establish that these mutations are activating, detail their effects upon cell signaling, and define how RHOA-mediated FAK activation imparts sensitivity to pharmacologic FAK inhibitors.See related commentary by Benton and Chernoff, p. 182.This article is highlighted in the In This Issue feature, p. 161.

P962Follow-up of protected high-risk percutaneous coronary intervention with microaxial Impella pump. Results from the retrospective German Impella Registry

Background

Percutaneous coronary intervention (PCI) presents a relevant alternative to coronary bypass surgery for the treatment of patients with complex coronary artery disease and high perioperative risk. By temporary implantation of a percutaneous ventricular assist devices (pVAD) interventionalists attempt to anticipate the hemodynamic risk of those high-risk patients in a so-called protected PCI. The Impella® system presents the currently most common device for protected PCI and could show hemodynamic stability in earlier trials.

Methods

This study is a retrospective, observational multi-center registry of ten hospitals in Germany. We included patients undergoing protected high-risk PCI with Impella® support. The primary endpoint was defined as major adverse cardiac events (MACE) during a 180-day follow-up and consisted of all-cause mortality, myocardial infarction (MI) and stroke.

Results

Six of the participating hospitals performed a follow-up. In total, 157 patients (80.3% male; mean age 71.8±10.8 years) were included in the present study. Prior to PCI, median left ventricular ejection fraction was 39.0% (25.0%-50.0%) and median SYNTAX-Score I was 33.0 (24.0–40.5). The 180-day follow-up was available for 149 patients (94.9%). Eight patients (5.1%) were lost to follow-up. During the follow-up period, 34 patients (22.8%) suffered from a MACE. A total of 27 patients (18.1%) died. Nine patients (6.0%) sustained a MI, while 4 patients (2.7%) had a stroke.

Kaplan-Meier curves for primary endpoint

Conclusions

Patients undergoing protected high-risk PCI with Impella® support show a good 180-day clinical outcome regarding rates of MACE and mortality. However, a head-to-head comparison of Impella supported patients to protected PCI with other pVADs is pending.

Acknowledgement/Funding

S.B., N.W., F.A.-R., J.-M.S., A.S., R.S., I.A. receive consulting fees/honoraria from Abiomed (Danvers, MA, USA).

P1706Neurological outcome in patients with out-of-hospital cardiac arrest undergoing a standardised protocol including therapeutic hypothermia and routine coronary angiography

Purpose

To establish cut-offs for neuromarkers such as neuron-specific enolase (NSE) and S-100 predicting good neurological outcome for patients treated with therapeutic hypothermia with out-of-hospital cardiac arrest (OHCA) and return of spontaneous circulation (ROSC) as current cut-offs had been derived from normothermic cohorts.

Methods

Consecutive data of all patients with OHCA admitted to our institution between 01/2011 and 12/2016 were collected in a database. Patient received standard intensive care according to the Hannover Cardiac Resuscitation Algorithm (HaCRA) including mandatory hypothermia. Neurological markers such as neuron-specific enolase (NSE) and S-100 have been used to assess neurological damage following OHCA.

Results

Mean age of overall patient population (n=302) was 63±14 [54–74] years with a male predominance (77%). Cardiac arrest was witnessed in 81% and bystander cardiopulmonal resuscitation (CPR) was performed in 67%. Initial rhythm was ventricular fibrillation in 69%. ROSC had been achieved after 24±17 minutes. Hypothermia was applied in all patients. In 95% percutaneous coronary angiography and in 57% of them coronary intervention was performed. After ROSC, STEMI was present in 44%. Mechanical support was required in 19%. 30 day mortality was 44% in the total cohort. Mean NSE was 27±69 μg/l, mean NSE with good neurological outcome was 20±8.7 μg/l, highest NSE with good neurological outcome was 46 μg/l. Mean S-100 was 0.114±2.037μg/l, mean S-100 with good neurological outcome was 0.068±0.067 μg/l, highest S-100 with good neurological outcome was 0.360 μg/l.

Conclusion

Even when using a strict protocol for OHCA patients and routinely applying therapeutic hypothermia, the cut-offs for NSE and S-100 regarding good neurological outcome are similar to those reported before without therapeutic hypothermia, but they must not be used solitary to withdraw life support as even very high markers can be associated with goof neurological outcome in individual patients.

P5736Mortality in infarct-related cardiogenic shock patients treated with an microaxial pump: influence of timing and predicted risk

Background

In-hospital mortality in acute myocardial infarction-related cardiogenic shock (AMI-CS) remains high at ∼40%. No prospective trials have been finished investigating the influence of mechanical support in AMI-CS. We compared observed to individually predicted mortality using CardShock-, Shock II-, and SAVE-scores in AMI-CS patients treated between 2013 and 2017 with an Impella microaxial pump, who met the IABP-Shock II-trials inclusion/exclusion criteria in order to determine whether standardised use of an Impella microaxial flow-pump in AMI-CS is associated with lower than predicted mortality rates and whether timing of implantation or selecting patients based on predicted risk is meaningful.

Methods

We analyzed data from 166 consecutive AMI-CS patients meeting the inclusion/exclusion criteria of the IABP-Shock II-trial (age 65±12 years), who received an Impella microaxial pump and compared observed vs. individually predicted mortality using CardShock-, Shock II-, and SAVE-scores. 39% (n=65) had been resuscitated before Impella implantation.

Results

Overall 30-day mortality was 43%. Mortality was higher in resuscitated patients (50% vs. 36%, p=0.0324) and when Impella was implanted post-PCI (Impella-pre-PCI: 29%, Impella-post-PCI: 50%, p=0.0130). In all score systems predicted mortality was significantly higher than observed mortality on Impella support for individuals with highest predicted risk (IABP-Shock II predicted 77% vs observed 44%, p=0.010; CardShock predicted 77% vs observed 51%, p=0.017; SAVE predicted 81% vs observed 56%, p<0.001).

Conclusion

In the absence of prospective trials, our retrospective analysis encourages the use of active mechanical circulatory support by Impella microaxial pumps in high-risk patients with AMI-CS and supports the concept of early implantation prior to PCI.

Defect-Induced Water Bilayer Growth on Anatase TiO2(101)

Preparing an anatase TiO₂(101) surface with a high density of oxygen vacancies and associated reduced Ti species in the near-surface region results in drastic changes in the water adsorption chemistry compared to adsorption on a highly stoichiometric surface. Using synchrotron radiation excited photoelectron spectroscopy, we observe a change in the water growth mode, from layer-by-layer growth on the highly stoichiometric surface to bilayer growth on the reduced surface. Furthermore, we have been able to observe Ti³⁺ enrichment at the surface upon water adsorption. The Ti³⁺ enrichment occurs concomitant with effective water dissociation into hydroxyls with a very high thermal stability. The water bilayer on the reduced surface is thermally more stable than that on the stoichiometric surface, and it is more efficient in promoting further water dissociation upon heating. The results thus show how the presence of subsurface defects can alter the wetting mechanism of an oxide surface.

Human Cerebellar Sub-millimeter Diffusion Imaging Reveals the Motor and Non-motor Topography of the Dentate Nucleus

The reciprocal cortico-cerebellar loops that underlie cerebellar contributions to motor and cognitive behavior form one of the largest systems in the primate brain. Work with non-human primates has shown that the dentate nucleus, the major output nucleus of the cerebellum, contains topographically distinct connections to both motor and non-motor regions, yet there is no evidence for how the cerebellar cortex connects to the dentate nuclei in humans. Here we used in-vivo sub-millimeter diffusion imaging to characterize this fundamental component of the cortico-cerebellar loop, and identified a pattern of superior motor and infero-lateral non-motor connectivity strikingly similar to that proposed by animal work. Crucially, we also present first evidence that the dominance for motor connectivity observed in non-human primates may be significantly reduced in man - a finding that is in accordance with the proposed increase in cerebellar contributions to higher cognitive behavior over the course of primate evolution.

Analysis of Minimally Invasive Left Thoracotomy HVAD Implantation – A Single-Center Experience

Background Minimally invasive left ventricular assist device (LVAD) implantation may reduce peri-/postoperative complications and risks associated with resternotomies. In this study, we describe our first results using a minimally invasive LVAD implantation technique (lateral thoracotomy [LT] group). These results were compared with LVAD implantations done via full median sternotomy (STX group).

Methods HVAD (HeartWare, Framingham, Massachusetts, United States) implantations in 70 patients (LT group n = 22, 52 ± 15 years old; STX group n = 48, 59 ± 11 years old) were retrospectively analyzed. Minimally invasive access via left thoracotomy was feasible in 22 patients. Peri- and postoperative analyses of survival and adverse events were performed.

Results No survival differences were observed between the LT and STX group (p = 0.43). LT patients without temporary right ventricular assist device (tRVAD) showed a significantly better survival rate compared to LT patients with concomitant tRVAD implantation (p = 0.02), which could not be demonstrated in the STX group (p = 0.11). Two LT and four STX patients were successfully bridged to heart transplantation and three STX patients were successfully weaned with subsequent LVAD explantations. LVAD-related infections (n = 4 LT group vs n = 20 STX group, p = 0.04) were less likely in the LT group. No wound dehiscence occurred in the LT group, whereas five were observed in the STX group (p = 0.17). The amount of perioperative blood transfusions (within the first 7 postoperative days) did not differ in both study groups (p = 0.48).

Conclusion The minimally invasive approach is a viable alternative with the possibility to reduce complications and should be particularly considered for bridge-to-transplant patients.

A randomized, controlled, double-blind, multi-center trial to evaluate the efficacy and safety of a liquid containing ivy leaves dry extract (EA 575®) vs. placebo in the treatment of adults with acute cough

This randomized, placebo-controlled, double-blind trial was conducted to assess the efficacy and safety of ivy leaves cough liquid in the treatment of acute cough. A total of 181 adult patients with acute cough were treated with either ivy leaves cough liquid containing EA 575® or with placebo three times a day for one week. The primary efficacy outcome was cough severity (CS) assessed by Visual Analogue Scale (VAS) over the whole treatment period (area-under-the-curve (AUC0-168 h) over 7 days (visit (V)1, V2, V3, V4, and V5). The secondary endpoints were defined as the CS assessed by VAS over the whole observation period (V1 - V6) and by Bronchitis Severity Score (BSS) and Verbal Category Descriptive (VCD) score. The evaluation of the VAS, BSS and VCD score revealed that subjects treated with ivy leaves cough liquid showed statistically significant and clinically relevant reductions in CS, severity of symptoms associated with cough and bronchitis compared to the placebo group. Furthermore, a remarkable early onset of efficacy was observed as significant reductions of cough severity were detected within 48 hours after the first drug intake. At all following visits and even 7 days after the end of treatment (V6) this significant treatment advantage was detected in comparison to placebo. All adverse events (AEs) in this clinical trial were non-serious, mild or of moderate severity and not drug-related. This clinical trial proved consistent superiority of the ivy leaves cough liquid treatment versus placebo and confirmed the EA 575® preparation to be a safe and efficacious option for the treatment of acute cough.

Die Strahlenexposition des Patienten durch die Transmissionsmessung bei der Myokardperfusions-SPECT

Ziel: Ziel war die Bestimmung der Strahlenexposition des Patienten durch die Transmissionsmessung bei der Myokardperfusions-SPECT. Methode und Material: Simultan zur Emissionsmessung (Tc-99m-MIBI, A = 500 MBq) erfolgt bei der Myokardperfusions-SPECT eine Transmissionsmessung mit Hilfe einer Am-241-Linienquelle (A = 5550 MBq). Bei der Simulation der Myokardperfusions-SPECT (ohne Tc-99m-MIBI) wurden Dosismessungen mit Thermolumineszenzdosimetem unter Verwendung eines Thoraxphantoms durchgeführt. Ergebnisse: Bei einer Aufnahmedauer von 20 min ergaben sich folgende Energiedosen: Oberfläche (Xyphoid) 30 μGy, Herz 25 μGy, Lunge 14 μGy, 2. BWK 16 μGy, oberes anteriores Mediastinum 16 μGy, Leber 0 μGy. Eine Abschätzung des Verhältnisses zwischen den effektiven Dosen durch Transmissions- und Emissionsmessung (3,6 x 10-3 bzw. 4,1 mSv) ergab einen Wert von 9 x 10-4. Schlußfolgerung: Die Strahlenexposition des Patienten durch die Transmissionsmessung ist vernachlässigbar gering und damit kein limitierender Faktor im Hinblick auf die generelle Anwendung der Transmissionsmessung bei der klinischen Myokardperfusions-SPECT.

Radiation exposure to the patient caused by single-photon transmission measurement for 3D whole-body PET

Aim: The aim of the study was the determination of the radiation exposure to the patient caused by singlephoton transmission mesasurement for 3D whole-body PET. Material and Method: Single-photon-transmission measurement is performed using two Cs-137 pointsources (Eγ = 662 keV, A = 2*614 MBq) on a 3D PET scanner (ECAT ART). During a simulation of a whole body transmission scan (axial length: 75 cm, 6 contigous bed positions) dose measurements with thermoluminescent dosimeters were carried out using a thorax and an abdomen phantom. Following the guidelines of the ICRU report No. 60 an estimation of the effective dose caused by a single-photon transmission measurement was calculated. Results: For a total acquisition time of 360 min (6 beds with an acquisition time of 60 min per bed) the absorbed doses amounted to: surface (xyphoid) 189 μGy, heart 196 μGy, lungs 234 μGy, vertebra 240 μGy, liver 204 μGy, gonads 205 μGy, thyroid 249 μGy and bladder 185 μGy resulting in a conversion factor of 1.7*10–4 mSv/( h*MBq). The estimation of the effective dose for a patient’s transmission (acquisition time of 3.2 min per bed) yields a value of 11 μSv. An estimation of the ratio of the conversion factors for transmission measurements in single-photonand in coincidence mode (two Ge-68/Ga-68 rod sources of 40 MBq each), respectively, resulted in a value of 0.18. The comparison of the effective doses caused by single-photon transmission and by emission measurement (injection of 250 MBq of FDG) yields a ratio of 2.3*10–3. Conclusion: The radiation exposure of the patient caused by the transmission measurement for 3D whole-body-PET can be neglected. In comparison with the coincidence-transmission using uncollimated line sources of low activity the radiation exposure is still reduced using single photon transmission with collimated point sources of high activity.

Inflammation-Sensitive Myosin-X Functionally Supports Leukocyte Extravasation by Cdc42-Mediated ICAM-1-Rich Endothelial Filopodia Formation

Leukocyte transendothelial migration is key to inflammation. Leukocytes first start rolling over the inflamed endothelium, followed by firmly adhering to it. Under inflammatory conditions, endothelial cells express small finger-like protrusions that stick out into the lumen. The function and regulation of these structures are unclear. We present evidence that these ICAM-1- and F-actin-rich endothelial finger-like protrusions are filopodia and function as adhesive structures for leukocytes to transit from rolling to crawling but are dispensable for diapedesis. Mechanistically, these structures require the motor function of myosin-X, activity of the small GTPase Cdc42, and p21-activated kinase 4. Moreover, myosin-X expression is under control of TNF-α-mediated c-Jun N-terminal kinase activity and is upregulated in human atherosclerotic regions. To our knowledge, this is the first study to identify that regulation of endothelial filopodia is crucial for leukocyte extravasation, in particular for the initiation of leukocyte adhesion under flow conditions.

Physical aspects of scintigraphybased dosimetry for nuclear medicine therapy

In nuclear medicine therapy the treatment of tumours by radiation exposure from internally deposited labelled antibodies or labelled peptides is currently an active field of investigation. To permit the efficient delivery of high amounts of radiation dose to tumours while limiting the radiation dose to critical organs dosimetry calculations have to be performed. These are relying on scintigraphic data being input to the well known MIRD formalism.

This paper focuses on the methods and the difficulties associated with the scintigraphic determination of organ kinetics. The physical properties of the well-known scintigraphic imaging modalities, PET, SPECT and planar scintigraphy, are discussed thereby taking into account the properties of the appropriate radionuclides currently being available for therapy and dosimetry. Several arguments are given and disputed for the limited clinical use of PET and SPECT in dosimetry and the ongoing preference of planar whole-body imaging as the method of choice. The quantitative restrictions still inherent to this method are also discussed in detail. Procedural recommendations are proposed covering all processes related to data acquisition, data correction and data analysis which finally lead to reliable estimations of organ dose.

Para-[123I]iodo-L-phenylalanine in patients with pancreatic adenocarcinoma

Recently, p-[123I]iodo-L-phenylalanine (IPA) was clinically validated for brain tumour imaging. Preclinical studies demonstrated uptake of IPA into pancreatic adenocarcinoma suggesting its diagnostic application in patients with pancreatic tumours. The aim was to study the tumour uptake of IPA in patients with pancreatic adenocarcinoma and to analyse its biodistribution and dosimetry to assess the radiation dose resulting from its diagnostic use. Patients, methods: Seven patients with pancreatic adenocarcinoma underwent whole-body scintigraphies and SPECT up to 24 h after administration of 250 MBq of IPA. Tumour uptake of IPA was assessed visually. Time activity curves and the corresponding residence times were determined for whole-body, kidneys, liver, spleen, lung, heart content, brain, and testes. Mean absorbed doses for various organs and the effective dose were assessed based on the MIRD formalism using OLINDA/EXM. Results: IPA exhibited no accumulation in proven manifestations of pancreatic adenocarcinomas. IPA was exclusively eliminated by the urine and showed a delayed clearance from blood. Residence times were 0.26 ± 0.09 h for kidneys, 0.38 ± 0.19 h for liver, 0.15 ± 0.07 h for spleen, 0.51 ± 0.20 h for lungs, 0.22 ± 0.07 h for heart content, 0.11 ± 0.05 h for brain, 0.014 ± 0.005 h for testes and 6.4 ± 2.2 h for the remainder. The highest absorbed doses were determined in the urinary bladder wall and in the kidneys. According to the ICRP 60 the effective dose resulting from 250 MBq IPA was 3.6 ± 0.7 mSv. Conclusion: Para-[123I]iodo-L-phenylalanine can be used in diagnostic nuclear medicine with acceptable radiation doses. Besides its proven validity for brain tumour imaging, IPA does not appear to be suitable as tracer for pancreatic cancer.

Integration of Murine and Human Studies for Mapping Periodontitis Susceptibility

Periodontitis is one of the most common inflammatory human diseases with a strong genetic component. Due to the limited sample size of available periodontitis cohorts and the underlying trait heterogeneity, genome-wide association studies (GWASs) of chronic periodontitis (CP) have largely been unsuccessful in identifying common susceptibility factors. A combination of quantitative trait loci (QTL) mapping in mice with association studies in humans has the potential to discover novel risk loci. To this end, we assessed alveolar bone loss in response to experimental periodontal infection in 25 lines (286 mice) from the Collaborative Cross (CC) mouse population using micro-computed tomography (µCT) analysis. The orthologous human chromosomal regions of the significant QTL were analyzed for association using imputed genotype data (OmniExpress BeadChip arrays) derived from case-control samples of aggressive periodontitis (AgP; 896 cases, 7,104 controls) and chronic periodontitis (CP; 2,746 cases, 1,864 controls) of northwest European and European American descent, respectively. In the mouse genome, QTL mapping revealed 2 significant loci (-log P = 5.3; false discovery rate = 0.06) on chromosomes 1 ( Perio3) and 14 ( Perio4). The mapping resolution ranged from ~1.5 to 3 Mb. Perio3 overlaps with a previously reported QTL associated with residual bone volume in F2 cross and includes the murine gene Ccdc121. Its human orthologue showed previously a nominal significant association with CP in humans. Use of variation data from the genomes of the CC founder strains further refined the QTL and suggested 7 candidate genes ( CAPN8, DUSP23, PCDH17, SNORA17, PCDH9, LECT1, and LECT2). We found no evidence of association of these candidates with the human orthologues. In conclusion, the CC populations enabled mapping of confined QTL that confer susceptibility to alveolar bone loss in mice and larger human phenotype-genotype samples and additional expression data from gingival tissues are likely required to identify true positive signals.