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Assessing tumor drug sensitivity by a new in vitro assay which preserves tumor heterogeneity and subpopulation
Abstract:
We have designed an in vitro assay to assess the influence of tumor subpopulation interactions on drug response. The assay is based upon inhibition of growth of 1 mm3-pieces of tumor embedded in a collagen gel matrix. Tumor growth is quantitated by planimetry of each colony's image, formed with a split image tracing device attached to an inverted microscope. That expansion of the colonies in collagen gel represents growth through cell replication was demonstrated by releasing and counting cell nuclei. Outgrowths from pieces of tumors produced by a series of mouse mammary tumor subpopulation lines expanded in collagen gel at a rate characteristic of each cell line: the growth rate of tumor pieces was similar to that of the corresponding tumor line embedded as a cell bolus of cultured cells, indicating that growth of pieces of tumor is due to the tumor cells rather than to stromal components. When two cell lines were grown together in collagen cultures, interactions affecting growth rate were observed. Both tumor pieces and cell boluses from cultured cells of the relatively homogeneous cell lines displayed similar, characteristic sensitivities to adriamycin (ADR) in the collagen gel assay. Advantages of the collagen assay over cloning assays are (1) preservation of potential cellular interactions which may be important in assessing tumor drug sensitivity; (2) maximization of growth of all cell populations within the tumor, as compared to growth in agar; and (3) reflection of the zonal distribution of different subpopulations within tumors; and (4) simulation of the three-dimensional growth architecture found in vivo.
Insights
This study introduces a novel in vitro collagen gel assay to evaluate how tumor cell interactions affect drug response. The assay accurately measures tumor growth and drug sensitivity, preserving in vivo conditions.
Area of Science:
- Oncology
- Biotechnology
- Drug Discovery
Background:
- Tumor heterogeneity significantly impacts drug response.
- Accurate in vitro models are crucial for predicting in vivo drug efficacy.
- Existing assays may not fully capture complex tumor microenvironment interactions.
Purpose of the Study:
- To develop and validate a novel in vitro assay for assessing tumor subpopulation interactions and their influence on drug response.
- To compare the performance of this assay against traditional cloning assays.
- To evaluate the drug sensitivity of tumor pieces and cultured cells using the developed assay.
Main Methods:
- Utilizing a 3D collagen gel matrix to embed 1 mm³ tumor pieces.
- Quantifying tumor growth via planimetry of colony images captured by microscopy.
- Validating growth as cell replication through cell nuclei counting.
- Assessing drug sensitivity using adriamycin (ADR) on tumor pieces and cell boluses.
Main Results:
- Tumor pieces in collagen gel exhibited characteristic growth rates, mirroring cultured cell lines.
- Growth in collagen gel was confirmed to be due to tumor cell replication.
- Co-culture experiments revealed interactions between cell lines affecting growth rates.
- Both tumor pieces and cell boluses showed similar adriamycin sensitivities.
Conclusions:
- The collagen gel assay effectively models in vivo tumor growth architecture and cellular interactions.
- This assay preserves crucial cell-cell interactions, offering a more realistic assessment of tumor drug sensitivity compared to traditional methods.
- The assay supports the growth of diverse tumor subpopulations, providing a comprehensive evaluation of drug response.