Serially heterotransplanted human prostate tumours as an experimental model

Chemosensitivity and resistance testing in malignant effusions with focus on primary malignant mesothelioma and metastatic adenocarcinoma

Cell based chemosensitivity and resistance testing is an attractive approach that offers functional measurement of drug response ex vivo with the ultimate goal to guide the choice of chemotherapy for various cancers. Thus, it has a great potential to select patients for the optimal treatment option, thereby offering a tool for personalized cancer therapy. Despite several decades of intensive scientific efforts ex-vivo tests are still not incorporated in the standard of care. Limited access to fresh tumor tissue, unsatisfactory models and single readout as endpoint constitute major hindrance. Thus, establishing and validating clinically useful and reliable model systems still remains a major challenge. Here we present malignant effusions as valuable sources for ex-vivo chemosensitivity and resistance testing. Accumulation of a malignant effusion in the pleura, peritoneum or pericardium is often the first diagnostic material for both primary malignant mesothelioma and a broad spectrum of metastatic adenocarcinoma originating from lung-, breast-, ovary- and gastro-intestinal organs as well as lymphoma. In contrast to biopsies, in these effusions malignant cells are easily accessible and often abundant. Effusion derived cells can occur dissociated or forming three-dimensional papillary structures that authentically recapitulate the biology of the corresponding tumor tissue and offer models for ex vivo testing. In addition, effusions have the advantage of being available prior to or concurrent with the pathological review, thus constituting an excellent source of viable cells for simultaneous molecular profiling, biomarker analysis and for establishing primary cells for studying tumor biology and resistance mechanisms. For a reliable test, however, a careful validation is needed, taking into account the inherited heterogeneity of malignant tumors, but also the complex interplay between malignant and benign cells, which are always present in this setting.

Establishment of a novel experimental model of human angiosarcoma and a VEGF-targeting therapeutic experiment

BACKGROUND

Angiosarcoma is one of the most life-threatening neoplasms with strong resistance to conventional chemotherapy/radiotherapy; consequently, alternative therapeutic agents are urgently required. One factor in delaying the therapy development is the limitation of experimental models.

OBJECTIVE

We established a novel experimental angiosarcoma model.

METHODS

From surgically resected tissue, human AS cell line was established. Using xenograft of AS cell line, we performed therapeutic experiments with the anti-human VEGF Ab or the receptor tyrosine kinase inhibitor.

RESULTS

First we generated an angiosarcoma cell line, HAMON (human angiosarcoma, monoclonal), which expresses CD31 and produces tumors in immunodeficient mice. HAMON expresses VEGFR2 and that exogenous VEGF leads to HAMON proliferation in vitro. Anti-human VEGF Ab bevacizumab treatment failed to suppress HAMON proliferation in vitro and in vivo. Furthermore, the receptor tyrosine kinase inhibitor sunitinib did not suppress HAMON proliferation in vitro. Similarly, in in vivo therapeutic experiments, even high doses of sunitinib failed to inhibit tumor growth. Finally, we checked whether compensatory activation of VEGF signaling occurred after sunitinib addition. VEGF protein secretion, VEGF mRNA synthesis and VEGFR2 phosphorylation all were unaffected in HAMON after sunitinib treatment.

CONCLUSION

A novel in vitro and in vivo experimental model of human angiosarcoma has been successfully established. With this model, we were able to perform therapeutic experiments. In addition, our angiosarcoma cell line, HAMON, is quite useful for identifying key molecules in angiosarcoma.

Discrepancies between metabolic activity and DNA content as tool to assess cell proliferation in cancer research

Cell proliferation is a critical and frequently studied feature of molecular biology in cancer research. Therefore, various assays are available using different strategies to measure cell proliferation. Metabolic assays such as AlamarBlue, water-soluble tetrazolium salt and 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide, which were originally developed to determine cell toxicity, are used to assess cell numbers. Additionally, proliferative activity can be determined by quantification of DNA content using fluorophores such as CyQuant and PicoGreen. Referring to data published in high ranking cancer journals, these assays were applied in 945 publications over the past 14 years to examine the proliferative behaviour of diverse cell types. In these studies, however, mainly metabolic assays were used to quantify changes in cell growth yet these assays may not accurately reflect cellular proliferation rates due to a miscorrelation of metabolic activity and cell number. Testing this hypothesis, we compared the metabolic activity of different cell types, human cancer cells and primary cells, over a time period of 4 days using AlamarBlue and the fluorometric assays CyQuant and PicoGreen to determine their DNA content. Our results show certain discrepancies in terms of over-estimation of cell proliferation with respect to the metabolic assay in comparison to DNA binding fluorophores.