Jun 23, 2006 - 1:09 am
Cell Culture Drug Resistance Testing (CCDRT) has a long history with a number of different technologies and many different tumor types tested. Almost all technologies used for hematological malignancies are identical in their logic and similar in their execution.
The concepts underlying cell death assays are relatively simple: if the drug kills tumor cells from an individual patient in a test tube, then the drug is more likely to be effective when administered to a patient. Conversely, a drug that does not kill the patient's cells, even at concentrations significantly higher than can be achieved in the patient, it is unlikely to be effective.
Total cell kill assay have almost exclusively been used for testing the drug sensitivity of leukemias and lymphomas. The DiSC assay and similar tests have some advantages over the other short term assays.
Cell Culture Drug Resistance Testing (CCDRT)
CCDRTs are laboratory tests in which fresh specimens of human neoplasms are cultured in the presence and absence of anti-cancer drugs. At the conclusion of the cell culture, measurements are made to determine whether the drugs are effective in either killing the neoplastic cells and in/or preventing their growth. Test results correlate with drug effects in the patient, with respect to both treatment response and patient survival.
The logic is that if the drug kills tumor cells from an individual patient in a test tube, then the drug is more likely to be effective when administered to a patient. Conversely, a drug that does not kill the patient's cancer cells, even at concentrations significantly higher than can be achieved in the patient, then it is unlikely to be effective.
The concept is to isolate cells from a fresh specimen obtained from a viable neoplasm. These cells are cultured in the continuous presence or absence of a drug, most often for 3 to 7 days. At the end of the culture period, a measurement is made of cell injury, which correlates directly with cell death (apoptosis).
The general measurements of cell death are the DISC assay method, the MTT assay method, the ATP assay method, and the flurescein diacetate assay method. These four endpoints produce valid and reliable measurements of cell death. They also correlate well with each other on direct comparisons of the different methods.
As with other laboratory tests, the determination of the efficacy of CCDRT is based on comparisons of laboratory tests with patient response (clinical correlations). The hypothesis to be tested with clinical correlations is that above-average drugs effects in the assays correlate with above-average drug effects in the patient, as measured by both response rates and patient survival.
Patients with test results in the "sensitive" range were more likely to respond than the total patient population as a whole. Conversely, patients with test results in the "resistant" range were less likely to respond than the patient population as a whole. On average, patients with assays in the "sensitive" range were 3.5-fold more likely to respond than patients with assays in the "resistant" range.
Gene Expression Profiling
Over the past few years, gene expression profiling has been suggested as the best or only way of determining ex vivo drug sensitivity. However, due to almost all patients being treated with combination chemotherapy, this methodology cannot even be calibrated without the use of CCDRT. CCDRTs can actually integrate all the gene expression into one convenient test result.
In obtaining information from gene mutations (DNA content assays) and/or gene expression (RNA content) it must be realized that DNA structure is only important insofar as it predicts for RNA content, which is only important insofar as it predicts for protein content, which is only important insofar as it predicts for protein func