Individual Susceptibility Analysis Using Patient-derived Slice Cultures of Colorectal Carcinoma

BACKGROUND

Nonresponse to chemotherapy in colorectal carcinoma (CRC) is still a clinical problem. For most established treatment regimens, no predictive biomarkers are available. Patient-derived tumor slice culture may be a promising ex vivo technology to assess the drug susceptibility in individual tumors.

METHODS

Patient-derived slice cultures of CRC specimens were prepared according to a standardized protocol and treated with different concentrations of 5-fluorouracil (5-FU) and an adapted FOLFOX regimen (5-FU and oxaliplatin) to investigate histologic response. Additionally, a semi-automatized readout using fluorescent stain-specific segmentation algorithms for Image J was established to quantify changes in tumor proliferation. Nonresponse to chemotherapy was defined as persisting tumor cell proliferation.

RESULTS

Slices treated with 5-FU showed lower tumor cell fractions and dose-dependent alterations of proliferating tumor cells compared with controls (1 μM, Δ +3%; 10 μM, Δ -9%; 100 μM, Δ -15%). Individual tumor samples were examined and differences in chemotherapy susceptibility could be observed. Untreated slice cultures contained an average tumor cell fraction of 31% ± 7%. For all samples, the histopathologic characteristics exhibited some degree of intratumoral heterogeneity with regard to tumor cell morphology and distribution. The original tumor matched the features found in slices at baseline and after 3 days of cultivation.

CONCLUSIONS

Patient-derived slice cultures may help to predict response to clinical treatment in individual patients with CRC. Future studies need to address the problem of tumor heterogeneity and evolution. Prospective correlation of ex vivo results with the clinical course of treated patients is warranted.

Organotypic slice cultures of human gastric and esophagogastric junction cancer

Gastric and esophagogastric junction cancers are heterogeneous and aggressive tumors with an unpredictable response to cytotoxic treatment. New methods allowing for the analysis of drug resistance are needed. Here, we describe a novel technique by which human tumor specimens can be cultured ex vivo, preserving parts of the natural cancer microenvironment. Using a tissue chopper, fresh surgical tissue samples were cut in 400 μm slices and cultivated in 6-well plates for up to 6 days. The slices were processed for routine histopathology and immunohistochemistry. Cytokeratin stains (CK8, AE1/3) were applied for determining tumor cellularity, Ki-67 for proliferation, and cleaved caspase-3 staining for apoptosis. The slices were analyzed under naive conditions and following 2-4 days in vitro exposure to 5-FU and cisplatin. The slice culture technology allowed for a good preservation of tissue morphology and tumor cell integrity during the culture period. After chemotherapy exposure, a loss of tumor cellularity and an increase in apoptosis were observed. Drug sensitivity of the tumors could be assessed. Organotypic slice cultures of gastric and esophagogastric junction cancers were successfully established. Cytotoxic drug effects could be monitored. They may be used to examine mechanisms of drug resistance in human tissue and may provide a unique and powerful ex vivo platform for the prediction of treatment response.

Organotypic slice cultures of human gastric cancer (GC) and esophagogastric junction adenocarcinoma (AEG): A new technology to study treatment response, resistance, and tumor heterogeneity

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Background: GC and AEG have an unpredictable response to cytotoxic treatment and a poor prognosis. There is an urgent need for new research methods allowing for the determination of chemotherapy sensitivities, the analysis of resistance mechanisms and tumor heterogeneity. Here, we describe a novel technique extending our recent findings in other tumors (Gerlach et al. 2014; Merz et al. 2013), by which cancer specimens can be cultured in vitro and maintained in their natural micro-environment. Methods: Using a tissue chopper, fresh surgical and endoscopic tissue samples from GC and AEG were cut in 400 µm thick slices and cultivated in 6-well plates for up to 6 days. The slices were then fixed, embedded in paraffin and cut for routine histopathology and immunohistochemistry. Cytokeratin stains (CK8 and AE1/3) were used for determining tumor cellularity, ki-67 for proliferation, and cleaved caspase 3 staining for apoptosis. The slices were examined under naïve condition and following in-vitro exposure to 5-FU, cisplatin or docetaxel over a period of 2-4 days. Results: GC and AEG slice cultures from resection specimens (n=14) and endoscopic biopsies (n=17) revealed a good preservation of tissue morphology and tumor cell integrity during the culture period in most cases. The stroma and the tumor cellularity remained stable over at least 4 days, proving the viability of cancer in slice cultures. The amount of sampled tissue from endoscopic biopsies was identified as a critical determinant for the feasibility of slice cultures. During treatment of cultures with chemotherapy, a significant loss of tumor cellularity and an increase of apoptotic cells were observed, although a systematic and reproducible read-out still needs to be established. Conclusions: Slice cultures of GC and AEG were successfully established. They can be expected to provide a unique and powerful in vitro platform for the determination of sensitivities of a given tumor towards chemotherapy, to examine mechanisms of drug-resistance and to analyze tumor heterogeneity in patient samples.

Slice cultures from head and neck squamous cell carcinoma: a novel test system for drug susceptibility and mechanisms of resistance

Background:

Human head and neck squamous cell carcinoma (HNSCC) fundamentally vary in their susceptibility to different cytotoxic drugs and treatment modalities. There is at present no clinically accepted test system to predict the most effective therapy for an individual patient.

Methods:

Therefore, we established tumour-derived slice cultures which can be kept in vitro for at least 6 days. Upon treatment with cisplatin, docetaxel and cetuximab, slices were fixed and paraffin sections were cut for histopathological analysis.

Results:

Apoptotic fragmentation, activation of caspase 3, and cell loss were observed in treated tumour slices. Counts of nuclei per field in untreated compared with treated slices deriving from the same tumour allowed estimation of the anti-neoplastic activity of individual drugs on an individual tumour.

Conclusion:

HNSCC-derived slice cultures survive well in vitro and may serve not only to improve personalised therapies but also to detect mechanisms of tumour resistance by harvesting surviving tumour cells after treatment.