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Old 07-10-2010, 03:08 PM   #3
gdpawel
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Re: Johns Hopkins is viewing cell behavior in three dimensions (3D)

In cell-based assay labs using functional profiling, they throw away the single cells and work exclusively with three dimensional, floating, tumor spheroids. If you test the same cells as three dimensional spheroids, they are not many-fold resistant in vitro, just as they are in vivo.

Once they have their proper comparison database, they then stratify the database, based on deviations from the median, for each assay system and at each drug concentration. One half standard deviation more "sensitive" than the median is the cut-off for a "sensitive result. One half standard deviation more "resistant" than the median is the cut-off for a "resistant" result.

Upgrading clinical therapy by using drug sensitivity assays measuring "cell death" of three dimensional microclusters of live "fresh" tumor cells improves the conventional situation by allowing more drugs to be considered. The more anti-cancer drug types there are in the selective arsenal, the more likely the system is to prove beneficial.

Because older assay types and peripheral blood assays test on subcultured cells (as opposed to fresh tumor cultures) and test the cells in monolayers (as opposed to three dimensional cell clusters), the cell grown in the lab will not behave the same way as the actual cancer cells do in your body' own environment.

However, all the work in the past twenty years in the cell culture field has been carried out largely on three dimensional clusters of cells (not monolayers). Solid tumor specimens are cultured in concical polypropylene microwells for 96 hours to increase the proportion of tumor cells, relative to normal cells.

Polypropylene is a slippery material which prevents the attachment of fibroblasts and epithelial cells and encourages the tumor cells to remain in the form of three dimensional, floating clusters. Real life 3D analysis makes chemoresponse assays indicative of what will happen in the body.

And since you got me started Rich, the "deviations" have to do with the Bayesian method of science, which Dr. Donald Berry, Ph.D., professor and chair of the Department of Biostatistics and Applied Mathematics at MD Anderson, says is more in line with how science works. They are putting the Bayesian approach (which is no stranger to cell culture assays) to test with more than 100 cancer-related phase I and II clinical trials planned or carried out.

In fact, the Bayesian methodology is what gives credit to the accuracy of cell culture assay testing. Bayes theorem has been used to describe the relationship between the accuracy of a predictive test (post-test probability) and the overall incidence of what is being tested (pre-test probability). Bayes' theorem indicates that cell death laboratory assays will be accurate in the prediction of clinical drug sensitivity and resistance in tumors.

Funny how some scientists think they have reinvented the wheel.
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