The Microtubule-Targeting Agent Pretubulysin Impairs the Inflammatory Response in Endothelial Cells by a JNK-Dependent Deregulation of the Histone Acetyltransferase Brd4

The anti-inflammatory effects of depolymerizing microtubule-targeting agents on leukocytes are known for a long time, but the potential involvement of the vascular endothelium and the underlying mechanistic basis is still largely unclear. Using the recently synthesized depolymerizing microtubule-targeting agent pretubulysin, we investigated the anti-inflammatory potential of pretubulysin and other microtubule-targeting agents with respect to the TNF-induced leukocyte adhesion cascade in endothelial cells, to improve our understanding of the underlying biomolecular background. We found that treatment with pretubulysin reduces inflammation in vivo and in vitro via inhibition of the TNF-induced adhesion of leukocytes to the vascular endothelium by down-regulation of the pro-inflammatory cell adhesion molecules ICAM-1 and VCAM-1 in a JNK-dependent manner. The underlying mechanism includes JNK-induced deregulation and degradation of the histone acetyltransferase Bromodomain-containing protein 4. This study shows that depolymerizing microtubule-targeting agents, in addition to their established effects on leukocytes, also significantly decrease the inflammatory activation of vascular endothelial cells. These effects are not based on altered pro-inflammatory signaling cascades, but require deregulation of the capability of cells to enter constructive transcription for some genes, setting a baseline for further research on the prominent anti-inflammatory effects of depolymerizing microtubule-targeting agents.

Fluorite-related iridate Pr3IrO7: crystal growth, structure, magnetism, thermodynamic, and optical properties

Spin-orbit coupling in heavy 5dmetal oxides, in particular, iridates have received tremendous interest in recent years due to the realization of exotic electronic and magnetic phases. Here, we report the synthesis, structural, magnetic, thermodynamic, and optical properties of the ternary iridate Pr₃IrO₇. Single crystals of Pr₃IrO₇have been grown by the KF flux method. Structural analysis shows that Pr₃IrO₇crystallizes in an orthorhombic phase withCmcmsymmetry. The electron energy loss spectroscopy study indicates that Pr is in a 3+ valence state, which implies a 5+ oxidation state of Ir. Magnetization data measured at high and low magnetic fields do not exhibit any bifurcation betweenM_ZFCandM_FC, however, a weak hump inM(T) is observed atT∗∼10.4 K. The specific heat data reveal two maxima at ∼253 and ∼4.8 K. The optical conductivityσ1(ω)spectrum shows 24 infrared-active phonon modes and reveals an insulating behavior with an optical gapΔOPof size ∼500 meV. During cooling down, the temperature-dependent reflectivity spectrum reveals eight extra phonon modes below the structural phase transition (∼253 K). An anomaly is observed at aroundT∗in the temperature evolution of infrared-active mode frequencies suggesting the presence of significant spin-phonon coupling in the system.

Exploring behavior change motivation in an outpatient sample with more than one health risk behavior

Background

Evidence from western countries shows that the majority of adults have two or more health risk behaviors. The motivation to engage in a health behavior change (HBC) is the most proximal determinant of behavior change in the future. The aim of this study was to investigate the intention to increase physical activity and to quit smoking in an outpatient sample that show both health risk behaviors.

Methods

We used baseline data (n = 109) of an intervention study (Germany, 2016-2019) on physical activity and smoking cessation. Eligibility criteria were: aged 40 to 65 years, systolic blood pressure ≥130 mmHg, no history of cardiovascular event or vascular intervention. We collected information on HBC motivation, sex, age, and self-rated health (SRH) and identified 32 physically inactive smokers. Descriptive analyses and Fisher’s exact test were used to explore the proportion of those motivated for HBC and differences according to sex, age (45-55 vs. 56-65 years), and SRH (excellent-good vs. poor-very poor).

Results

Participants (50% female) were on average 52.6 years old and 78% had school education ≤10 years. Overall, 44% intended to change physical inactivity only, 34% intended to change both behaviors, 13% wanted to change neither, and 9% intended to change smoking only. There was no difference in HBC motivation according to sex and age. But, there was a significant difference according to SRH (Fisher’s exact = 0.048); e.g., there were more individuals motivated to change both behaviors among those with lower SRH (64%) compared to those with higher SRH (19%).

Conclusions

In this baseline sample of an intervention study, the majority of participants intended to change physical inactivity but not smoking. Among those with lower SRH, almost two-thirds intended to change both behaviors. Thus, individuals with more than one health risk behavior differ in their HBC motivation. Lower SRH may offer a window of opportunity to promote HBC interventions.

Key messages

• Physically inactive smokers with a systolic blood pressure ≥130 mmHg differ in their motivation to change these behaviors.

• Lower self-rated health may offer a window of opportunity to promote interventions to change health behavior.

National strategy for palliative care of severely ill and dying people and their relatives in pandemics (PallPan) in Germany - study protocol of a mixed-methods project

Background

In the SARS-CoV-2 pandemic, general and specialist Palliative Care (PC) plays an essential role in health care, contributing to symptom control, psycho-social support, and providing support in complex decision making. Numbers of COVID-19 related deaths have recently increased demanding more palliative care input. Also, the pandemic impacts on palliative care for non-COVID-19 patients. Strategies on the care for seriously ill and dying people in pandemic times are lacking. Therefore, the program ‘Palliative care in Pandemics’ (PallPan) aims to develop and consent a national pandemic plan for the care of seriously ill and dying adults and their informal carers in pandemics including (a) guidance for generalist and specialist palliative care of patients with and without SARS-CoV-2 infections on the micro, meso and macro level, (b) collection and development of information material for an online platform, and (c) identification of variables and research questions on palliative care in pandemics for the national pandemic cohort network (NAPKON).

Methods

Mixed-methods project including ten work packages conducting (online) surveys and qualitative interviews to explore and describe i) experiences and burden of patients (with/without SARS-CoV-2 infection) and their relatives, ii) experiences, challenges and potential solutions of health care professionals, stakeholders and decision makers during the SARS-CoV-2 pandemic. The work package results inform the development of a consensus-based guidance. In addition, best practice examples and relevant literature will be collected and variables for data collection identified.

Discussion

For a future “pandemic preparedness” national and international recommendations and concepts for the care of severely ill and dying people are necessary considering both generalist and specialist palliative care in the home care and inpatient setting.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12904-021-00898-w.

A pre-registered short-term forecasting study of COVID-19 in Germany and Poland during the second wave

Disease modelling has had considerable policy impact during the ongoing COVID-19 pandemic, and it is increasingly acknowledged that combining multiple models can improve the reliability of outputs. Here we report insights from ten weeks of collaborative short-term forecasting of COVID-19 in Germany and Poland (12 October-19 December 2020). The study period covers the onset of the second wave in both countries, with tightening non-pharmaceutical interventions (NPIs) and subsequently a decay (Poland) or plateau and renewed increase (Germany) in reported cases. Thirteen independent teams provided probabilistic real-time forecasts of COVID-19 cases and deaths. These were reported for lead times of one to four weeks, with evaluation focused on one- and two-week horizons, which are less affected by changing NPIs. Heterogeneity between forecasts was considerable both in terms of point predictions and forecast spread. Ensemble forecasts showed good relative performance, in particular in terms of coverage, but did not clearly dominate single-model predictions. The study was preregistered and will be followed up in future phases of the pandemic.

Intestinal and hepatic contributions to the pharmacokinetic interaction between gamithromycin and rifampicin after single-dose and multiple-dose administration in healthy foals

BACKGROUND

Standard treatment of foals with severe abscessing lung infection caused by Rhodococcus equi using rifampicin and a macrolide antibiotic can be compromised by extensive inhibition and/or induction of drug metabolising enzymes (e.g. CYP3A4) and transport proteins (e.g. P-glycoprotein), as has been shown for rifampicin and clarithromycin. The combination of rifampicin with the new, poorly metabolised gamithromycin, a long-acting analogue of azithromycin and tulathromycin with lower pharmacokinetic interaction potential, might be a suitable alternative.

OBJECTIVES

To evaluate the pharmacokinetic interactions and pulmonary distribution of rifampicin and gamithromycin in healthy foals, and to investigate the cellular uptake of gamithromycin in vitro.

STUDY DESIGN

Controlled, four-period, consecutive, single-dose and multiple-dose study.

METHODS

Pharmacokinetics and lung distribution of rifampicin (10 mg/kg) and gamithromycin (6 mg/kg) were measured in nine healthy foals using LC-MS/MS. Enzyme induction was confirmed using the 4β-OH-cholesterol/cholesterol ratio. Affinity of gamithromycin to drug transport proteins was evaluated in vitro using equine hepatocytes and MDCKII-cells stably transfected with human OATP1B1, OATP1B3 and OATP2B1.

RESULTS

Rifampicin significantly (P<0.05) increased the plasma exposure of gamithromycin (16.2 ± 4.77 vs. 8.57 ± 3.10 μg × h/mL) by decreasing the total body clearance. Otherwise, gamithromycin significantly lowered plasma exposure of single- and multiple-dose rifampicin (83.8 ± 35.3 and 112 ± 43.1 vs. 164 ± 96.7 μg × h/mL) without a change in metabolic ratio and half-life. Gamithromycin was identified as an inhibitor of human OATP1B1, OATP1B3 and OATP2B1 and as a substrate of OATP2B1. In addition, it was extracted by equine hepatocytes via a mechanism which could be inhibited by rifampicin.

MAIN LIMITATIONS

Influence of gamithromycin on pulmonary distribution of rifampicin was not evaluated.

CONCLUSION

The plasma exposure of gamithromycin is significantly increased by co-administration of rifampicin which is most likely caused by inhibition of hepatic elimination.

Pitfalls in accelerometer-based measurement of physical activity: The presence of reactivity in an adult population

When a behavior is monitored, it is likely to change, even if no change may be intended. This phenomenon is known as measurement reactivity. We investigated systematic changes in accelerometer-based measures over the days of monitoring as an indicator of measurement reactivity in an adult population. One hundred seventy-one participants from the general population (65% women; mean age = 55 years, range: 42-65 years) wore accelerometers for 7 consecutive days to measure sedentary behavior and physical activity (PA). Latent growth models were used (a) to investigate changes in accelerometer wear time over the measurement days and (b) to identify measurement reactivity indicated by systematic changes in sedentary time (ST), light physical activity (LPA), and moderate-to-vigorous physical activity (MVPA). Over the measurement days, participants reduced accelerometer wear time by trend (rate of change [b] = -4.7 min/d, P = .051, Cohen's d = .38), increased ST (b = 2.4 min/d, P = .018, d = .39), and reduced LPA (b = -2.4 min/d, P = .015, d = .38). Participants did not significantly reduce MVPA (P = .537). Our data indicated that accelerometry might generate reactivity. Small effects on ST and LPA were found. Thus, the validity of accelerometer-based data on ST and LPA may be compromised. Systematic changes observed in accelerometer wear time may further bias accelerometer-based measures. MVPA seems to be less altered due to the presence of an accelerometer.

The pretubulysin-induced exposure of collagen is caused by endothelial cell retraction that results in an increased adhesion and decreased transmigration of tumor cells

Microtubule-targeting agents (MTAs) are the most widely used chemotherapeutic drugs. Pretubulysin (PT), a biosynthetic precursor of the myxobacterial tubulysins, was recently identified as a novel MTA. Besides its strong anti-tumoral activities, PT attenuates tumor angiogenesis, exerts anti-vascular actions on tumor vessels and decreases cancer metastasis formation in vivo. The aim of the present study was to analyze the impact of PT on the interaction of endothelial and tumor cells in vitro to gain insights into the mechanism underlying its anti-metastatic effect. The influence of PT on tumor cell adhesion and transmigration onto/through the endothelium as well as its influence on cell adhesion molecules and the chemokine system CXCL12/CXCR4 was investigated. Treatment of human endothelial cells with PT increased the adhesion of breast cancer cells to the endothelial monolayer, whereas their transmigration through the endothelium was strongly reduced. Interestingly, the PT-induced upregulation of ICAM-1, VCAM-1 and CXCL12 were dispensable for the PT-evoked tumor cell adhesion. Tumor cells preferred to adhere to collagen exposed within PT-triggered endothelial gaps via β1-integrins on the tumor cell surface. Taken together, our study provides, at least in part, an explanation for the anti-metastatic potential of PT.

[Rehabilitation Processes in Out- and Inpatient Rehabilitation after Radical Prostatectomy]

We evaluated processes in in- and outpatient rehabilitation after radical prostatectomy. Overall, we analyzed motivation and expectations of 119 in- and 719 outpatients (aged≤64) at the beginning of rehabilitation as well as satisfaction and the amount of interventions at the end. Compared to inpatients outpatients had a higher socio-economic status and better physical condition. Both groups reported similar outcomes regarding motivation, expectation and satisfaction. Furthermore in- and outpatients got a comparable amount of interventions, but both groups differed to some extent in regard to the kind of interventions. In- and outpatients are comparable in regard to their received amount of interventions. Discrepancies concerning the kind of interventions are due to differences between in- and outpatients. The results indicate specific patients' characteristics in both settings, but more research is needed to verify these findings.

Coumaryl Triflate, a Versatile Building Block for the Modification of Coumarins and for Fluorescence Labeling

Coumaryl triflate can be used for a wide range of substitution reactions, either under Pd-catalyzed conditions or via direct nucleophilic substitutions, and is therefore an ideal substrate for the fluorescence labeling of functionalized compounds, such as amino acids.

[Collaborative Goal Setting in Rehabilitation (ParZivar II): Evaluation of an Intervention in Patients with Chronic Back Pain]

OBJECTIVE

The "ParZivar II" project had 2 aims: optimization of the "ParZivar I" intervention by individual coaching of physicians, and evaluation of the optimized intervention.

METHODS

The intervention was evaluated in a sequential control group design in 4 rehabilitation facilities with 3 measurement points. A total of n=279 patients with chronic low back pain participated in the study.

RESULTS

The optimized intervention shows the potential to statistically significantly improve proximal outcomes (e. g. goal-centric processes or patient-physician interaction). Regarding distal outcomes, no statistically significant differences were found.

CONCLUSION

The "ParZivar" intervention is a suitable approach to increase participative goal setting. Due to the complexity of the intervention, problems of dissemination and the potential for improvement in study design, there is a need for further research.

Selective growth of MFU-4l single crystals on microstructured plasma polymer coatings

Crystals of the metal–organic framework Ulm-4l(arge) grow site selectively and with 〈1 0 0〉 orientation on microtextured plasma polymer coatings.

Simplified pretubulysin derivatives and their biological effects on cancer cells

Tubulin binding agents are a potent group of cancer chemotherapeutics. Most of these substances are naturally derived compounds. A novel substance class of destabilizing agents is the group of tubulysins. The tubulysins and their derivative pretubulysin have shown high efficacy in vitro and in vivo. Due to their complex chemical structures, one major bottleneck of the tubulysins is their accessibility. Biotechnological as well as chemical production is challenging, especially on larger scales. Thus, the synthesis of chemically simplified structures is needed with retained or improved biological activity. Herein is presented the biological evaluation of two pretubulysin derivatives [2-desmethylpretubulysin AU816 (1) and phenylpretubulysin JB337 (2)] in comparison to pretubulysin. Both 1 and 2 display a simplification in chemical synthesis. It was shown that both compounds exhibited potent biological activity against cancer cells. These simplified compounds inhibited tubulin polymerization in the nanomolar range. The cytotoxic effects of 1 and 2 were in a similar range, when compared with pretubulysin [IC50 (nM): pretubulysin: 0.6; 1: 10; 2: 100]. Furthermore, it was shown that cell cycle arrest is induced and migration is hampered in MDA-MB-231 breast cancer cells. In conclusion, 1 was shown to be about 10-fold more active than 2 and as potent as pretubulysin.

Novel Tubulin Antagonist Pretubulysin Displays Antivascular Properties In Vitro and In Vivo

Objective—

Pretubulysin (PT) is a novel, synthetically accessible myxobacterial compound that acts as a tubulin-depolymerizing agent and inhibits cancer cell growth in vitro and in vivo. Moreover, PT was found to attenuate tumor angiogenesis. Here, we hypothesized that PT could exert antivascular activities on existing tumor vessels.

Approach and Results—

We aimed to characterize the antivascular effects of PT and to elucidate the underlying mechanisms in endothelial cells. In vitro, PT rapidly induced endothelial hyperpermeability and a concentration-dependent disassembly of established endothelial tubes on Matrigel and in an ex vivo aortic ring model. It disrupted endothelial cell junctions and triggered F-actin stress fiber formation and cell contraction by the RhoA/Rho-associated protein kinase pathway without causing cell death. In vivo, using a hamster dorsal skinfold chamber preparation, PT significantly decreased blood flow and vessel diameter in hamster A-Mel-3 amelanotic melanoma tumors but not in the neighboring healthy tissue. In a second tumor model using mice with subcutaneous murine B16 melanoma tumors, a single dose of PT (10 mg/kg) caused a shut down of tumor blood flow and a strong central tumor cell necrosis within 24 hours. Repeated PT administration significantly decelerates tumor growth and seems to be well tolerated.

Conclusions—

In summary, we could show for the first time that the antitumor effect of PT is, at least in part, mediated via its antivascular activities on existing tumor vessels.

Developing FGFR4 inhibitors as potential anti-cancer agents via in silico design, supported by in vitro and cell-based testing

Fibroblast growth factor receptor-4 (FGFR4) is a tyrosine kinase with a range of important physiological functions. However, it is also frequently mutated in various cancers and is now generating significant interest as a potential therapeutic target. Unfortunately, biochemical characterization of its role in disease, and further evaluation as a drug target is hampered by lack of a specific inhibitor. We aimed to discover new inhibitors for FGFR4 ab initio using a strategy combining in silico, in vitro and cell-based assays. We used the homologous FGFR1 to calculate docking scores of a chemically-diverse library of approximately 2000 potential kinase inhibitors. Nineteen potential inhibitors and ten randomly- selected negative controls were taken forward for in vitro FGFR4 kinase assays. All compounds with good docking scores significantly inhibited FGFR4 kinase activity, some with sub-micromolar (most potent being V4-015 with an IC(50) of 0.04 μM). Four of these compounds also demonstrated substantial activity in cellular assays using the FGFR4- overexpressing breast carcinoma cell line, MDA-MB453. Through immunoblot assays, these compounds were shown to block the phosphorylation of the FGFR4 adaptor protein, FGFR substrate protein-2α (FRS2α). The most potent compound to date, V4-015, suppressed proliferation of MDA-MB453 cells at sub-micromolar concentrations, activated the pro-apoptotic caspases 3/7 and inhibited cellular migration. While achieving complete selectivity of this compound for FGFR4 will require further lead optimization, this study has successfully identified new chemical scaffolds with unprecedented FGFR4 inhibition capacities that will support mechanism of action studies and future anti-cancer drug design.

[Female patients with fibromyalgia syndrome in somatic and psychosomatic rehabilitation center - an exploratory study on access routes and differences in patient characteristics]

STUDY OBJECTIVE

Fibromyalgia syndrome (FMS) is characterized by e. g. chronic, multilocular pain, and mental health problems. In Germany, patients with FMS are treated in somatic and psychosomatic rehabilitation centers - specialized for rheumatic diseases (somatic) or psychosomatic diseases. The aim of this study is to identify the status quo of FMS patients' access routes to the rehabilitation system, and to identify their predictors for being assigned to one or the other indication group.

METHOD

Our cohort consists of 197 FMS patients from 3 psychosomatic (M=49.9 years) and 223 FMS patients (M=50.2 years) from 3 somatic rehabilitation centers. At the beginning of rehabilitation, patients filled out a questionnaire packet to identify their access routes to the rehabilitation centers and to record patients' disease-related, psychosocial and socio-demographic characteristics. To analyze the results we used descriptive calculations, calculated bivariate correlations, and conducted binary logistic regression analysis for the prediction of group membership.

RESULTS

The access routes of FMS patients to a somatic or a psychosomatic rehabilitation center were often similar. Some items revealed significant group differences, i. e., a higher primary -rejection rate, longer waiting period between application for rehabilitation and its approval, and between the application itself and initiation of psychosomatic rehabilitation in comparison to somatic FMS patients. Prior experience of out-patient psychotherapy, and expectations ("psychological support") for the rehabilitation were predictive patient characteristics for the assignment into a psychosomatic rehabilitation center. Marriage, motivation, and expectations ("physical improvement" and "interaction with other patients") for the rehabilitation were predictive patient characteristics for the assignment in a somatic rehabilitation center. The predictors clarified 32% of the variance of group membership.

CONCLUSION

Our results provide initial evidence of how FMS patients access the German rehabilitation system and which of their characteristics are responsible for being assigned to a particular rehabilitation setting.

[Evaluation of a Vocationally Oriented Concept within Inpatient Oncological Rehabilitation]

AIM OF THE STUDY

We evaluated an occupation-related rehabilitation program, which has been designed to enhance the return to work of cancer patients. As return to work plays an important role to get back to normalcy after suffering from cancer, there is a substantial need for support and evaluated programs.

METHODS

The study had a quasi-experimental design with an intervention group (IG) and a comparison group (CG). We defined performance-related outcomes (e. g. return to work, self-assessed working capacity), asked patients if they needed further vocational advice and how helpful they estimated the rehabilitation treatment. 1 year after the end of rehabilitation 309 employed patients had completed the study (65%). We addressed our research questions using non-parametric tests, t-tests, analyses of variance and logistic regressions.

RESULTS

Of the 309 patients 58% started rehabilitation not later than 14 days after the end of acute treatment while the other 42% had finished their treatments at least some weeks or even months ago. Patients of the IG evaluated the work-related rehabilitation offers significantly better and needed less additional vocational advice after the end of rehabilitation (n. s.). Regarding the patients, who started rehabilitation not later than 14 days after the end of acute treatment (beginning of rehabilitation n=269, 12 months after rehabilitation n=174), the IG achieved a slightly higher return-to-work-rate 12 months after the end of rehabilitation (81% IG, 76% CG, n. s.). Above that the IG estimated their subjective working capacity significantly more often as fully re-established (IG 46%; CG 29%, p=0,030).

CONCLUSIONS

A high percentage of the patients return to work (78%). These results show the success of oncological rehabilitation in helping patients to return to work. In addition, the occupation-related rehabilitation program enhances subjective variables as the satisfaction of the patients regarding the information and the improvement of the patients' working-capacity.

Anti-angiogenic effects of the tubulysin precursor pretubulysin and of simplified pretubulysin derivatives

BACKGROUND AND PURPOSE

The use of tubulin-binding compounds, which act in part by inhibiting tumour angiogenesis, has become an integral strategy of tumour therapy. Recently, tubulysins were identified as a novel class of natural compounds of myxobacterial origin, which inhibit tubulin polymerization. As these compounds are structurally highly complex, the search for simplified precursors [e.g. pretubulysin (Prt)] and their derivatives is mandatory to overcome supply problems hampering clinical development. We tested the anti-angiogenic efficacy of Prt and seven of its derivatives in comparison to tubulysin A (TubA).

EXPERIMENTAL APPROACH

The compounds were tested in cellular angiogenesis assays (proliferation, cytotoxicity, cell cycle, migration, chemotaxis, tube formation) and in vitro (tubulin polymerization). The efficacy of Prt was also tested in vivo in a murine subcutaneous tumour model induced with HUH7 cells; tumour size and vascularization were measured.

KEY RESULTS

The anti-angiogenic potency of all the compounds tested ran parallel to their inhibition of tubulin polymerization in vitro. Prt showed nearly the same efficacy as TubA (EC(50) in low nanomolar range in all cellular assays). Some modifications in the Prt molecule caused only a moderate drop in potency, while others resulted in a dramatic loss of action, providing initial insight into structure-activity relations. In vivo, Prt completely prevented tumour growth and reduced vascular density to 30%.

CONCLUSIONS AND IMPLICATIONS

Prt, a chemically accessible precursor of some tubulysins is a highly attractive anti-angiogenic compound both in vitro and in vivo. Even more simplified derivatives of this compound still retain high anti-angiogenic efficacy.

Expression of epidermal growth-factor receptor correlates with metastatic potential of 13762nf rat mammary adenocarcinoma cells

Increased expression of EGFR in metastases of human mammary carcinoma as compared to cells of the primary cancer suggests a contribution of EGFR to mammary carcinoma metastasis. To test for a positive correlation, we investigated 13762NF rat mammary adenocarcinoma cloned tumor cell lines of high (MTLn3) or low (MTC) metastatic potential. While MTC cells expressed barely detectable amounts of EGFR, MTLn3 cells expressed readily detectable levels of receptor. This was demonstrated in Northern blot analysis, in immunoprecipitation studies using metabolically labeled whole cell lysates and in Western blot analysis of membrane fractions. Cross-linking of radiolabeled ligand to intact cells identified on both cell types specific binding to a 170 kd protein, however, at much lower levels on low-metastatic MTC cells and not in sufficient amounts to estimate receptor numbers by Scatchard analysis. In contrast, Scatchard plot analysis of I-125-EGF binding to MTLn3 cells revealed the expression of about 10,000 high and 46,000 low affinity sites. Both cell lines expressed the ligand in comparable amounts as was demonstrated by using a specific rat TGFalpha cDNA probe in Northern blot and an antibody recognising membrane bound TGF in FACS analysis. Adhesion of MTC cells to immobilized collagen or fibronectin was rapid reaching 50% after 30 min while control MTLn3 cells demonstrated lower adhesion to collagen. Addition of 10 ng/ml EGF increased the rate and the maximal adhesion of MTLn3 cells to collagen G, while the adhesion kinetics of MTC cells to collagen G or fibronectin were unaffected.

Synthetic studies towards bottromycin

Thio-Ugi reactions are described as an excellent synthetic tool for the synthesis of sterically highly hindered endothiopeptides. S-Methylation and subsequent amidine formation can be carried out in an inter- as well as in an intramolecular fashion. The intramolecular approach allows the synthesis of the bottromycin ring system in a straightforward manner.

Pretubulysin: from hypothetical biosynthetic intermediate to potential lead in tumor therapy

Pretubulysin is a natural product that is found in strains of myxobacteria in only minute amounts. It represents the first enzyme-free intermediate in the biosynthesis of tubulysins and undergoes post-assembly acylation and oxidation reactions. Pretubulysin inhibits the growth of cultured mammalian cells, as do tubulysins, which are already in advanced preclinical development as anticancer and antiangiogenic agents. The mechanism of action of this highly potent compound class involves the depolymerization of microtubules, thereby inducing mitotic arrest. Supply issues with naturally occurring derivatives can now be circumvented by the total synthesis of pretubulysin, which, in contrast to tubulysin, is synthetically accessible in gram-scale quantities. We show that the simplified precursor is nearly equally potent to the parent compound. Pretubulysin induces apoptosis and inhibits cancer cell migration and tubulin assembly in vitro. Consequently, pretubulysin appears to be an ideal candidate for future development in preclinical trials and is a very promising early lead structure in cancer therapy.