Multicell spheroid tumor

In the second part of this article (Section III), various tumor models, which can mimic several characteristics of human tumors, are summarized and compared. These models include single cells, multicell spheroids, and experimental solid tumors. The most obvious and observable characteristic of neoplastic diseases is uncontrolled growth, invasion, and metastasis. As a result, attempts to model growth kinetics of tumor are discussed briefly in this section. 

Multicell spheroids provide an in vitro model for tumors which is intermediate in complexity between solid tumors and single cell cultures. Spheroids are three-dimensional, spherical clusters of a variety of animal and human cells about 0.1-1 mm in diameter. Spheroids can be grown in suspension culture, in quiescent liquid, or in semi-solid medium. 

Multicell spheroids have been used to study the transport of molecules and cells. They have been used for in vivo studies by injecting spheroids into the peritoneal cavities of experimental animals. This approach has been used to study tumor cell response to drugs and also to study immune response to tumors. As a result of lack of vasculature, caution must be exercised in using spheroid information to plan treatment in animals and patients (Sutherland, 1988). 

Since solid tumors are the primary cause of cancerous deaths, in this article we will focus our attention on these tumors. Results obtained from single cells and multicell spheroids will also be discussed to compare the information obtained from all three systems. 

Sundfor K, Lyng H, Trope CG, Rofstad EK (2000) Treatment outcome in advanced squamous cell carcinoma of the uterine cervix relationships to pretreatment tumor oxygenation and vascularization. Radiother Oncol 54 101-107 Sutherland RM (1988) Cell and environment interactions in tumor microregions The multicell spheroid model. Science 240 177-184... 

T.H. Foster, D.F. Hartley, M.G. Nichols, R. Hilf (1993). Fluence rate effects in photodynamic therapy of multicell tumor spheroids. Cancer Res., 53, 1249-1254. 

Spikes, J.D., Quantum yields and kinetics of the photobleaching of hematoporphyrin, Photofrin 11, tetra(4-sulfonatophenyl)porphine and uroporphyrin, Photochem. Photobiol., 55, 797,1992. Coutier, S., Mitra, S., Bezdetnaya, L.N., Parache, R.M., Georgakoudi, I., Foster, T.H., and Guillemin, F, Effects of fluence rate on cell survival and photobleaching in meta-tetra-(hydroxyphenyl)chlo-rin-photosensitized Colo 26 multicell tumor spheroids, P/jotoc/iem. Photobiol, 73, 297, 2001. Finlay, J.C., Conover, D.L., Hull, E.L., and Foster, T.H., Porphyrin bleaching and PDT-induced spectral changes are irradiance dependent in ALA-sensitized normal rat skin in vivo, Photochem. Photobiol, 73, 54, 2001. 

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