Carl Friedrich Classen

Establishment and Characterization of Primary Glioblastoma Cell Lines from Fresh and Frozen Material: A Detailed Comparison

Background Development of clinically relevant tumor model systems for glioblastoma multiforme (GBM) is important for advancement of basic and translational biology. High molecular heterogeneity of GBM tumors is well recognized, forming the rationale for molecular tests required before administration of several of the novel therapeutics rapidly entering the clinics. One model that has gained wide acceptance is the primary cell culture model. The laborious and time consuming process is rewarded with a relative high success rate (about 60%). We here describe and evaluate a very simple cryopreservation procedure for GBM tissue prior to model establishment that will considerably reduce the logistic complexity. Methods Twenty-seven GBM samples collected ad hoc were prepared for primary cell culture freshly from surgery (#1) and after cryopreservation (#2). Results Take rates after cryopreservation (59%) were as satisfactory as from fresh tissue (63%; p = 1.000). We did not observe any relevant molecular or phenotypic differences between cell lines established from fresh or vitally frozen tissue. Further, sensitivity both towards standard chemotherapeutic agents (Temozolomide, BCNU and Vincristine) and novel agents like the receptor tyrosine kinase inhibitor Imatinib did not differ. Conclusions Our simple cryopreservation procedure facilitates collection, long-time storage and propagation (modeling) of clinical GBM specimens (potentially also from distant centers) for basic research, (pre-) clinical studies of novel therapies and individual response prediction.

Arginine deprivation by arginine deiminase of Streptococcus pyogenes controls primary glioblastoma growth in vitro and in vivo

Arginine auxotrophy constitutes a weak point of several tumors, among them glioblastoma multiforme (GBM). Hence, those tumors are supposed to be sensitive for arginine-depleting substances, such as arginine deiminase (ADI). Here we elucidated the sensitivity of patient-individual GBM cell lines toward Streptococcus pyogenes-derived ADI. To improve therapy, ADI was combined with currently established and pre-clinical cytostatic drugs. Additionally, effectiveness of local ADI therapy was determined in xenopatients. Half of the GBM cell lines tested responded well toward ADI monotherapy. In those cell lines, viability decreased significantly (up to 50 %). Responding cell lines were subjected to combination therapy experiments to test if any additive or even synergistic effects may be achieved. Such promising results were obtained in 2/3 cases. In cell lines HROG02, HROG05 and HROG10, ADI and Palomid 529 combinations were most effective yielding more than 70 % killing after 2 rounds of treatment. Comparable boosted antitumoral effects were observed after adding chloroquine to ADI (>60% killing). Apoptosis, as well as cell cycle dysregulation were found to play a minor role. In some, but clearly not all cases, (epi-) genetic silencing of arginine synthesis pathway genes (argininosuccinate synthetase 1 and argininosuccinate lyase) explained obtained results. In vivo, ADI as well as the combination of ADI and SAHA efficiently controlled HROG05 xenograft growth, whereas adding Palomid 529 to ADI did not further increase the strong antitumoral effect of ADI. The cumulative in vitro and in vivo results proved ADI as a very promising candidate therapeutic, especially for development of adjuvant GBM combination treatments.

Therapeutical doses of temozolomide do not impair the function of dendritic cells and CD8+ T cells

The median survival of patients with glioblastoma multiforme (GBM) remains poor. Innovative immunotherapies with dendritic cell (DC) vaccination might be combined with standard temozolomide (TMZ) treatment. Here, we evaluated the influence of TMZ on the phenotype and function of DCs and CD8+ T cells. DCs were generated from the peripheral blood of healthy volunteers (HVs) and GBM patients. DCs were analyzed by light microscopy and flow cytometry. Phagocytic activity was tested by FITC-dextran engulfment. Mixed lymphocyte peptide cultures were followed by enzyme-linked immunospot (ELISPOT) and flow cytometry assays. TMZ was added to DC and T cell cultures at concentrations up to 500 µM. Mature DCs were generated from HVs and GBM patients. Cells displayed a typical DC morphology and a mature DC phenotype. Expression of CD209 was even higher in DCs generated from patients under therapy than from HVs (75.2 vs. 51.1%). In contrast, CD40 (1.1 vs. 13.5%) and BDCA4 (26.5 vs. 52.9%) were lower expressed in GBM patients at time of diagnosis. Immature DCs showed high phagocytic activity. Addition of TMZ at concentrations up to 50 µM did neither impair the phenotype nor the function of DCs. In ELISPOT and flow cytometry assays, no impairment of CD8+ T cell responses to viral antigens could be observed. Taken together, TMZ does not impair the function of either DCs or the CD8+ T cells.

Pediatric palliative care - The role of the patient’s family

Whenever a child suffers, what does she or he cry Mother! What does that mean Palliative care is not a type of medicine based on objective evidence or statistics. The only relevant standard is the very individual quality of life. Nobody knows better what this actually means but the patient himself. Thus, if the mothers presence has the biggest impact on a childs wellbeing or comfort, she herself is the most valuable treatment modality. In nearly every publication dealing with pediatric palliative care, it is stated that palliative care does not only imply care for the sick child but also for the parents and the whole family. Usually, it is pointed out that they are suffering a lot as well. But helping them does also mean: helping the child! Of course, it means higher efforts, obligations and costs for the healthcare system. Thus the justification of this effort may be put in question; in particular, it may be argued that disorders of family members should, if necessary, be treated as such. But this is only one side of the coin! In the following, we will, based on published literature, look at the role of mothers, fathers, and siblings for the wellbeing of an ill or even dying child. As a conclusion, we will learn that if it is our task to give a dying child the best available care, helping mothers, fathers and sibling is an inevitable part of it.

Temozolomide-induced increase of tumorigenicity can be diminished by targeting of mitochondria in in vitro models of patient individual glioblastoma

Glioblastoma multiforme (GBM) is a highly heterogeneous and aggressive brain tumor with a dismal prognosis. Development of resistance towards cytostatic drugs like the GBM standard drug temozolomide is a severe problem in GBM treatment. One potential source of GBM relapse could be so called cancer stem like cells (CSCs). These represent an undifferentiated subpopulation of cells with high potential for tumor initiation. Furthermore, it has been shown that differentiated GBM cells can regain CSC properties when exposed to continuous temozolomide treatment in vitro. In this study, treatment of several primary GBM cell lines with clinically relevant doses of temozolomide increased their tumorigenicity as determined by colony formation assays in soft agar. Increased tumorigenicity is a known property of CSCs. Hence, therapy options that specifically target CSCs are under investigation. CSCs appear to be particularly dependent on mitochondria biogenesis which may represent a useful target for CSC elimination. Toxicity towards mitochondria is a known side effect of several antibiotics. Thus, addition of antibiotics like doxycycline may represent a useful tool to inhibit CSCs in GBM. Here, we show that combining temozolomide treatment of primary GBM cells with doxycycline could counteract the increase of tumorigenicity induced by temozolomide treatment.

Amplification of the EGFR gene can be maintained and modulated by variation of EGF concentrations in in vitro models of glioblastoma multiforme

Glioblastoma multiforme (GBM) is the most common and lethal brain tumor in adults. It is known that amplification of the epidermal growth factor receptor gene (EGFR) occurs in approximately 40% of GBM, leading to enhanced activation of the EGFR signaling pathway and promoting tumor growth. Although GBM mutations are stably maintained in GBM in vitro models, rapid loss of EGFR gene amplification is a common observation during cell culture. To maintain EGFR amplification in vitro, heterotopic GBM xenografts with elevated EGFR copy number were cultured under varying serum conditions and EGF concentrations. EGFR copy numbers were assessed over several passages by quantitative PCR and chromogenic in situ hybridization. As expected, in control assays with 10% FCS, cells lost EGFR amplification with increasing passage numbers. However, cells cultured under serum free conditions stably maintained elevated copy numbers. Furthermore, EGFR protein expression positively correlated with genomic amplification levels. Although elevated EGFR copy numbers could be maintained over several passages in vitro, levels of EGFR amplification were variable and dependent on the EGF concentration in the medium. In vitro cultures of GBM cells with elevated EGFR copy number and corresponding EGFR protein expression should prove valuable preclinical tools to gain a better understanding of EGFR driven glioblastoma and assist in the development of new improved therapies.

Glioblastomas: are individual therapies required for individual tumors?

In contrast to most other malignant diseases, especially in children, up to now glioblastoma multiforma is a lethal diagnosis for most patients. Operation and radiotherapy are very effective to reduce the tumor burden, however, a strong adjuvant treatment is lacking. Due to rapid infiltrative growth, relapse is common, which can then no more be controlled in most of the cases. Many data are available on the cellular signaling and regulation networks in glioblastomas, particularly in the different growth factor receptor dependent pathways upregulated in these tumors. Numerous substances acting in a molecular way to inhibit these are at hand, but still, although these compounds showed some activity in individual patients, larger studies aiming at an improvement of the cure rate were generally disappointing. One reason for this might be the heterogeneity of tumors. Novel methods of molecular analysis showed that they are extremely heterogeneous - regarding genetic, epigenetic or signaling regulation, receptor expression, or interaction with stroma, vasculature, or the immune system. Another striking fact is that in glioblastomas of children and adolescents, completely different patterns of molecular setup are found compared to those in adults. Thus, probably a different therapeutical approach would be required for each tumor, using an individually selected panel of treatment modalities. For such an approach, besides many laboratory hurdles, also the concept of evidence based medicine has to be developed further to handle individualized medicine.