In: Chemotherapy20 Nov 2014
We have focused on the semiautomatic MTT assay, a tetrazolium dye method. Large numbers of samples can be tested at many drug concentrations and the results obtained within a few days. The major disadvantage of such assays is that they are unable to discriminate between normal and tumor cells if applied to fresh tumor samples. We are attempting to adapt the assay for clinical use by combining it with short-term selective culture of tumor cells in defined media as well as differential adhesiveness. By these methods, a relatively pure tumor cell sample can be obtained within a few days. add comment
Obviously, such an approach will only be successful if: 1) the assay reflects clinical experience, and 2) if cell lines (short- or long-term) are representative of the tumor specimens from which they were derived. We believe that the answer to both questions is an emphatic yes. Thus, lines from SCLC are much more chemosensitive than lines from NSCLC or carcinoid patients. In addition, SCLC lines from previously treated patients are modestly more resistant than those derived from previously untreated patients. Many problems remain. Some drugs, such as cyclophosphamide, cannot be tested under routine in vitro conditions; some, such as methotrexate, require serum free conditions to yield meaningful data. Methods for using in vitro data for clinical predictions remain controversial, with no universally accepted standard. The bottom line, of course, is whether the selected method is correlated with clinical response. Prediction of radiation sensitivity presents further problems, as several cell divisions may be required to gauge the full effects. While we have attempted to use the MTT assay for such purposes, clonogenic or plating assays remain the most widely used methods. These methods have identified a radioresistant subtype of SCLC associated with amplification and over-expression of the c-myc oncogene.
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