Assessment of the number of local cytotoxic T lymphocytes required for degradation of micrometer-size tumor spheroids.

The Institute of Physical and Chemical Research (RIKEN), Koyadai, RIKEN Cell Bank, Tsukuba Science City, Ibaraki, 305, Japan.
Cytotechnology (Impact Factor: 1.32). 10/2001; 37(1):31-40. DOI: 10.1023/A:1016139010531
Source: PubMed

ABSTRACT Adoptive immunotherapy with human cytotoxic T lymphocytes (CTL) is a promising cancer treatment. Previously we showed that human CTLs against various types of tumors can be efficiently produced by coculturing peripheral blood cells with target cells. The aims of this study were to simulate the interaction of CTLs and micrometer-size tumor tissues in vitro and to assess the required number of CTLs at local tumor sites for degradation of a tumor. Allogeneic CTLs against a human transitional cell carcinoma cell line and autologous CTLs against a renal cell carcinoma cell derived from a surgical specimen were generated. The cytotoxic activities of CTLs against tumor cells in monolayer culture and tumor spheroids formed in U-bottom 96-well culture plates were assessed. Both allogeneic and autologous CTLs showed greater destructive activity than lymphokine activated killer (LAK) cells against target tumor spheroids. CTLs inoculated at E/T ratios of 0.1 to 1 coexisted with the tumor spheroid for 5 to 6 days and then increased in number with apparently lethal activity against the tumor spheroid. In contrast to CTLs, the increase in LAK cell numbers was scarcely observed, and the proliferated LAK cells did not show cytotoxicity against the tumor spheroid. These observations suggest that, when a small number of CTLs reach a local tumor site, they can destroy micrometer-size tumors after considerable local proliferation.

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    ABSTRACT: The present article highlights the rationale, potential and flexibility of tumor spheroid mono- and cocultures for implementation into state of the art anti-cancer therapy test platforms. Unlike classical monolayer-based models, spheroids strikingly mirror the 3D cellular context and therapeutically relevant pathophysiological gradients of in vivo tumors. Some concepts for standardization and automation of spheroid culturing, monitoring and analysis are discussed, and the challenges to define the most convenient analytical endpoints for therapy testing are outlined. The potential of spheroids to contribute to either the elimination of poor drug candidates at the pre-animal and pre-clinical state or the identification of promising drugs that would fail in classical 2D cell assays is emphasised. Microtechnologies, in the form of micropatterning and microfluidics, are also discussed and offer the exciting prospect of standardized spheroid mass production to tackle high-throughput screening applications within the context of traditional laboratory settings. The extension towards more sophisticated spheroid coculture models which more closely reflect heterologous tumor tissues composed of tumor and various stromal cell types is also covered. Examples are given with particular emphasis on tumor-immune cell cocultures and their usefulness for testing novel immunotherapeutic treatment strategies. Finally, tumor cell heterogeneity and the extraordinary possibilities of putative cancer stem/tumor-initiating cell populations that can be maintained and expanded in sphere-forming assays are introduced. The relevance of the cancer stem cell hypothesis for cancer cure is highlighted, with the respective sphere cultures being envisioned as an integral tool for next generation drug development offensives.
    Journal of Biotechnology 07/2010; 148(1):3-15. · 3.18 Impact Factor

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