Direct chemosensitivity monitoring ex vivo on undissociated melanoma tumor tissue by impedance spectroscopy.

Stage III/IV melanoma remains incurable in most cases due to chemotherapeutic resistance. Thus, predicting and monitoring chemotherapeutic responses in this setting offer great interest. To overcome limitations of existing assays in evaluating the chemosensitivity of dissociated tumor cells, we developed a label-free monitoring system to directly analyze the chemosensitivity of undissociated tumor tissue. Using a preparation of tumor micro-fragments (TMF) established from melanoma biopsies, we characterized the tissue organization and biomarker expression by immunocytochemistry. Robust generation of TMF was established successfully and demonstrated on a broad range of primary melanoma tumors and tumor metastases. Organization and biomarker expression within the TMF were highly comparable with tumor tissue, in contrast to dissociated, cultivated tumor cells. Using isolated TMF, sensitivity to six clinically relevant chemotherapeutic drugs (dacarbazine, doxorubicin, paclitaxel, cisplatin, gemcitabine, and treosulfan) was determined by impedance spectroscopy in combination with a unique microcavity array technology we developed. In parallel, comparative analyses were performed on monolayer tumor cell cultures. Lastly, we determined the efficacy of chemotherapeutic agents on TMF by impedance spectroscopy to obtain individual chemosensitivity patterns. Our results demonstrated nonpredictable differences in the reaction of tumor cells to chemotherapy in TMF by comparison with dissociated, cultivated tumor cells. Our direct impedimetric analysis of melanoma biopsies offers a direct ex vivo system to more reliably predict patient-specific chemosensitivity patterns and to monitor antitumor efficacy.

Comparative label-free monitoring of immunotoxin efficacy in 2D and 3D mamma carcinoma in vitro models by impedance spectroscopy.

For selective killing of tumor cells, there are many novel and promising therapeutic approaches like immunotoxins. However, on the long way to clinical application, especially in vitro approved biologicals often fail due to loss of target sensitivity and efficacy in vivo. This is mostly explained with degradation or penetration disability in vivo. Although, these problems are well known, until today, there are no in vitro systems for reliable monitoring and quantification of therapeutic efficacy in 3D tumor models and the direct comparison to results from 2D models. In this context, we developed a combined label-free impedimetric monitoring system using our self-developed planar interdigital electrode arrays and our unique microcavity array technology. Therefore, we could demonstrate the time and concentration dependent monitoring and quantification of therapeutic efficacy in a 2D and 3D mamma carcinoma model. In detail, we synthesized a novel modular immunotoxin B3(dsFv)-PE38 (B3-PE38) in which the antibody fragment and the protein toxin are polyionic linked together. We compared the efficacy of the immunotoxin B3-PE38, the toxin E8C-PE38 (PE38) and the small molecule chemotherapeutic paclitaxel. The impedimetric screening revealed the highest cytotoxicity for the immunotoxin B3-PE38 in the 2D model. More strikingly, the immunotoxin efficacy was substantially higher in the 3D model when compared to PE38 and paclitaxel even though having a considerably lower penetration capability than paclitaxel. So our novel impedimetric monitoring system offers the comparative efficacy quantification of novel therapeutics in 2D and 3D in vitro tumor models.