Zell- und molekularbiologische Charakterisierung neuartiger Zell-Zell-Verbindungsarten in Glioma-Zellen und mesenchymalen Stammzellen

Zell-Zell-Verbindungen ("Junctions") der Adhaerens-Kategorie sind durch zelltypische Kombinationen von Transmembran-Glykoproteinen der Cadherin-Großfamilie und damit assoziierten cytoplasmatischen Plaque-Proteinen bestimmt, die meist Actin-Mikrofilamente verankern. Sie stellen Hauptstrukturelemente des spezifischen Gewebe-Aufbaus und Zusammenhalts dar und sind darüberhinaus auch an vielen dynamischen Zellfunktionen beteiligt. In den letzten Jahren hatte sich zunehmend deutlicher herausgestellt, dass viele "Adhering Junction" (AJ) besonderer Zelltypen nicht unter die bisher bekannten Klassen bzw. Typen von AJ subsumieren lassen, sondern aufgrund ihrer Struktur, vor allem aber ihrer besonderen molekularen Zusammensetzung eigene Strukturtypen sui generis darstellen. Im Rahmen dieser Arbeit sind zwei AJ-Typen menschlicher Zellen und Gewebe in ihrer molekularen Zusammensetzung bestimmt worden, wobei Untersuchungen an Zellkulturen sowie zellbiologische, biochemische, immunologische und molekularbiologische Methoden benutzt wurden. Astrocytom-Zellen, auch Astrocyten, und Glioblastom-Zellen bilden viele AJ unterschiedlicher Größe aus, die durch einen recht kompakten Plaque ausgezeichnet sind und die Cadherine N-Cadherin, Cadherin-11 sowie in einigen Zellkolonien immer wieder auch VE-Cadherin enthalten, die auf der Binnenseite mit den Plaque-Proteinen alpha- und beta-Catenin, den weiteren armadillo-Proteinen p120ctn, ARVCF und Plakoglobin sowie - überraschenderweise - dem von Desmosomen her bekannten Protein Plakophilin 2 und den - von "Tight Junctions" bekannten - Plaque-Proteinen ZO-1, ZO-2 und Cingulin komplexiert sind und zusammen mit Afadin und dem Actin-bindenden Protein Vinculin Mikrofilament-Bündel des Actin-Typs verankern. Molekulare Interaktionen innerhalb dieser Struktur werden aufgrund erster Immunpräzipitations-Ergebnisse ebenso diskutiert wie die mögliche Bedeutung dieses AJ-Typs, dem der Name Colligatio permixta gegeben wurde, in Embryologie, Histologie und Pathologie. Dabei ist das spontane klonale Auftreten einer Unterform, die das - erstmals außerhalb von Gefäß-Endothelien nachgewiesene - VE-Cadherin enthält, auch deshalb von besonderem Interesse, weil der Astrocyt - gewissermaßen seiner natürlichen Position nach - oft eine räumliche wie funktionale Beziehung zu Blutgefäßen, besonders Kapillaren erkennen lässt. Neue tumordiagnostischen Möglichkeiten wie entwicklungsbiologischen Implikationen der Entdeckung dieses neuen Junction-Typs werden besprochen. Gleichzeitig ist in Kulturen bestimmter menschlicher Knochenmarkzellen, sogenannter "mesenchymaler Stammzellen", ein anderer - in seiner molekularen Zusammensetzung äußerst schlichter - AJ-Typ entdeckt worden, der ebenfalls N-Cadherin und Cadherin-11 in Verbindung mit signifikanten Mengen der Plaque-Proteine alpha- und beta-Catenin, Protein p120ctn und Afadin enthält und vielfach auch Actinfilament-Bündel verankert. Dieser AJ-Typ erscheint in der Regel in Form kleiner Puncta adhaerentia (Durchmesser meist im Bereich 30-200 nm), wobei diese sowohl am eigentlichen zentralen Zellkörper als auch auf tentakel-artigen Zellausläufern verschiedener, teils sehr großer Länge (bis über 400 µm lang) vorkommen, die einerseits durch Actinfilament-Bündel in Verbindung mit Ezrin, alpha-Actinin und Myosin stabilisiert sind, andererseits aber auch Mikrotubuli enthalten. Solche Zellausläufer (Processus adhaerentes) können dabei sowohl über durch Puncta hergestellte Brückenstrukturen mit Ausläufern anderer Zellen verbunden sein, andererseits aber auch tief und eng in entsprechenden, z.T. sehr häufigen und langen (bis über 40 µm) Invaginationen von Nachbarzellen verankert sein, wobei die AJ-Regionen der Puncta beider Zellen gewissermaßen zu einer riesigen Doppelhülle (Manubrium adhaerens) fusioniert sein können. Hinweise auf ein Vorkommen solcher Processus adhaerentes in der Embryogenese und mögliche biologische Funktionen solcher Strukturen werden ebenso besprochen wie Einsatzmöglichkeiten und mögliche Bedeutung in der Diagnostik

Overall survival after reirradiation of spinal metastases – independent validation of predictive models

Background: It is unknown if survival prediction tools (SPTs) sufficiently predict survival in patients who undergo palliative reirradiation of spinal metastases. We therefore set out to clarify if SPTs can predict survival in this patient population. Methods: We retrospectively analyzed spinal reirradiations performed (n = 58, 52 patients, 44 included in analysis). SPTs for patients with spinal metastases were identified and compared to a general palliative score and to a dedicated SPT to estimate prognosis in palliative reirradiation independent of site (SPT-Nieder). Results: Consistently in all tests, SPT-Nieder showed best predictive performance as compared to other tools. Items associated with survival were general condition (KPS), liver metastases, and steroid use. Other factors like primary tumor site, pleural effusion, and bone metastases were not correlated with survival. We adapted an own score to the data which performed comparable to SPT-Nieder but avoids the pleural effusion item. Both scores showed good performance in identifying long-term survivors with late recurrences. Conclusions: Survival prediction in case of spinal reirradiation is possible with sufficient predictive separation. Applying SPTs in case of reirradiation helps to identify patients with good life expectancy who might benefit from dose escalation or longer treatment courses

Correspondence on rajyaguru et al

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Phantom-based evaluation of dose exposure of ultrafast combined kV-MV-CBCT towards clinical implementation for IGRT of lung cancer

Purpose: Combined ultrafast 90\ub0+90\ub0 kV-MV-CBCT within single breath-hold of 15s has high clinical potential for accelerating imaging for lung cancer patients treated with deep inspiration breath-hold (DIBH). For clinical feasibility of kV-MV-CBCT, dose exposure has to be small compared to prescribed dose. In this study, kV-MV dose output is evaluated and compared to clinically-established kV-CBCT. Methods: Accurate dose calibration was performed for kV and MV energy; beam quality was determined. For direct comparison of MV and kV dose output, relative biological effectiveness (RBE) was considered. CT dose index (CTDI) was determined and measurements in various representative locations of an inhomogeneous thorax phantom were performed to simulate the patient situation. Results: A measured dose of 20.5mGE (Gray-equivalent) in the target region was comparable to kV-CBCT (31.2mGy for widely-used, and 9.1mGy for latest available preset), whereas kVMV spared healthy tissue and reduced dose to 6.6mGE (30%) due to asymmetric dose distribution. The measured weighted CTDI of 12mGE for kV-MV lay in between both clinical presets. Conclusions: Dosimetric properties were in agreement with established imaging techniques, whereas exposure to healthy tissue was reduced. By reducing the imaging time to a single breathhold of 15s, ultrafast combined kV-MV CBCT shortens patient time at the treatment couch and thus improves patient comfort. It is therefore usable for imaging of hypofractionated lung DIBH patients

"Freezing" the Tumor in a Known Position During Radiation Therapy In Regard to Boda-Heggemann et al

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Clinical outcome of hypofractionated breath-hold image-guided SABR of primary lung tumors and lung metastases

Background: Stereotactic Ablative RadioTherapy (SABR) of lung tumors/metastases has been shown to be an effective treatment modality with low toxicity. Outcome and toxicity were retrospectively evaluated in a unique single-institution cohort treated with intensity-modulated image-guided breath-hold SABR (igSABR) without external immobilization. The dose–response relationship is analyzed based on Biologically Equivalent Dose (BED). Patients and methods: 50 lesions in 43 patients with primary NSCLC (n = 27) or lung-metastases of various primaries (n = 16) were consecutively treated with igSABR with Active-Breathing-Coordinator (ABC®) and repeat-breath-hold cone-beam-CT. After an initial dose-finding/-escalation period, 5x12 Gy for peripheral lesions and single doses of 5 Gy to varying dose levels for central lesions were applied. Overall-survival (OS), progression-free-survival (PFS), progression pattern, local control (LC) and toxicity were analyzed. Results: The median BED2 was 83 Gy. 12 lesions were treated with a BED2 of &lt;80 Gy, and 38 lesions with a BED2 of <80 Gy. Median follow-up was 15 months. Actuarial 1- and 2-year OS were 67% and 43%; respectively. Cause of death was non-disease-related in 27%. Actuarial 1- and 2-year PFS was 42% and 28%. Progression site was predominantly distant. Actuarial 1- and 2 year LC was 90% and 85%. LC showed a trend for a correlation to BED2 (p = 0.1167). Pneumonitis requiring conservative treatment occurred in 23%. Conclusion: Intensity-modulated breath-hold igSABR results in high LC-rates and low toxicity in this unfavorable patient cohort with inoperable lung tumors or metastases. A BED2 of <80 Gy was associated with reduced local control

Automated VMAT planning for postoperative adjuvant treatment of advanced gastric cancer

Background: Postoperative/adjuvant radiotherapy of advanced gastric cancer involves a large planning target volume (PTV) with multi-concave shapes which presents a challenge for volumetric modulated arc therapy (VMAT) planning. This study investigates the advantages of automated VMAT planning for this site compared to manual VMAT planning by expert planners. Methods: For 20 gastric cancer patients in the postoperative/adjuvant setting, dual-arc VMAT plans were generated using fully automated multi-criterial treatment planning (autoVMAT), and compared to manually generated VMAT plans (manVMAT). Both automated and manual plans were created to deliver a median dose of 45 Gy to the PTV using identical planning and segmentation parameters. Plans were evaluated by two expert radiation oncologists for clinical acceptability. AutoVMAT and manVMAT plans were also compared based on dose-volume histogram (DVH) and predicted normal tissue complication probability (NTCP) analysis. Results: Both manVMAT and autoVMAT plans were considered clinically acceptable. Target coverage was similar (manVMAT: 96.6 ± 1.6%, autoVMAT: 97.4 ± 1.0%, p = 0.085). With autoVMAT, median kidney dose was reduced on average by &gt; 25%; (for left kidney from 11.3 ± 2.1 Gy to 8.9 ± 3.5 Gy (p = 0.002); for right kidney from 9.2 ± 2.2 Gy to 6.1 ± 1.3 Gy (p &lt;  0.001)). Median dose to the liver was lower as well (18.8 ± 2.3 Gy vs. 17.1 ± 3.6 Gy, p = 0.048). In addition, Dmax of the spinal cord was significantly reduced (38.3 ± 3.7 Gy vs. 31.6 ± 2.6 Gy, p &lt;  0.001). Substantial improvements in dose conformity and integral dose were achieved with autoVMAT plans (4.2% and 9.1%, respectively; p &lt;  0.001). Due to the better OAR sparing in the autoVMAT plans compared to manVMAT plans, the predicted NTCPs for the left and right kidney and the liver-PTV were significantly reduced by 11.3%, 12.8%, 7%, respectively (p ≤ 0.001). Delivery time and total number of monitor units were increased in autoVMAT plans (from 168 ± 19 s to 207 ± 26 s, p = 0.006) and (from 781 ± 168 MU to 1001 ± 134 MU, p = 0.003), respectively. Conclusions: For postoperative/adjuvant radiotherapy of advanced gastric cancer, involving a complex target shape, automated VMAT planning is feasible and can substantially reduce the dose to the kidneys and the liver, without compromising the target dose delivery

Quality assurance process within the RAdiosurgery for VENtricular TAchycardia (RAVENTA) trial for the fusion of electroanatomical mapping and radiotherapy planning imaging data in cardiac radioablation

A novel quality assurance process for electroanatomical mapping (EAM)-to-radiotherapy planning imaging (RTPI) target transport was assessed within the multi-center multi-platform framework of the RAdiosurgery for VENtricular TAchycardia (RAVENTA) trial. A stand-alone software (CARDIO-RT) was developed to enable platform independent registration of EAM and RTPI of the left ventricle (LV), based on pre-generated radiotherapy contours (RTC). LV-RTC were automatically segmented into the American-Heart-Association 17-segment-model and a manual 3D-3D method based on EAM 3D-geometry data and a semi-automated 2D-3D method based on EAM screenshot projections were developed. The quality of substrate transfer was evaluated in five clinical cases and the structural analyses showed substantial differences between manual target transfer and target transport using CARDIO-RT