Identification of those patients with cancer who will or will not respond to a specific chemotherapy is important for making decisions regarding chemotherapy regimens as well as alternative management approaches. A laboratory test that could help to determine the sensitivity of an individual patient's tumor cells to specific chemotherapeutic agents would be valuable in choosing the optimal chemotherapy regimen for that patient with an expectation of increasing the response rate to the therapy. Several types of in vitro assays that measure tumor cell survival following exposure to cytotoxic agents have been evaluated for their ability to predict chemotherapy outcomes. As a group, these assays are referred to as drug resistance assays. In a resistance assay, the surviving tumor cells can be detected directly by their exclusion or metabolism of specific dyes. Alternatively, since some of tumor cells are proliferating, their survival can be detected by measurement of DNA synthesis by radiolabeled precursor incorporation or demonstration of clonogenic potential by growth into colonies in semi-solid culture medium. In several clinical studies, these assays were useful in detecting drug resistance and in predicting a poor prognosis for cancer patients. However, these resistance assays cannot detect sensitivity of an individual patient's tumor cells to a specific drug. Therefore, new methods determining drug-sensitivity of the tumor cells of an individual patient and, thus, capable of both predicting a positive treatment outcome and guiding chemotherapy, would be of significant value.
Recently, an automated microculture kinetic (MiCK) assay for measuring drug induced apoptosis in tumor cells has been developed1-4. Apoptosis is a distinct mode of cell death which occurs under physiological conditions and yet can be induced in malignant cells by chemical and physical factors including antitumor drugs5-7. During the last decade, it has been recognized that chemotherapeutic agents exert their antitumor activity by triggering apoptosis in susceptible tumor cells8-17. This implies that the MiCK assay for apoptosis provides a mechanism-based approach to studying effects of cytotoxic agents on tumor cells. Unlike "resistance" assays that measure a fraction of cells surviving drug exposure, the MiCK assay measures a fraction of tumor cells killed by a chemotherapeutic agent via mechanism of apoptosis. Therefore the MiCK assay determines drug sensitivity, rather than resistance. Recently the MiCK assay has been shown to predict complete remission rate and survival in acute myeloid leukemia patients better than clinical criteria did18-20. In a limited study, the MiCK assay has been used to direct chemotherapy of the leukemia patients 21.
The MiCK assay has also been used to study drug-induced apoptosis in solid tumors, including neuroblastoma and colon adenocarcinoma cell lines22-23. More recent data accumulated by DiaTech has demonstrated that the MiCK assay can detect drug induced apoptosis in primary cultures of tumor cells isolated from patients with ovarian carcinoma, gastric carcinoma, metastatic breast cancer and high grade soft tissue sarcoma. The purpose of this study is to correlate the results of the MICK assay with short- and long-term results of treatments in cancer patients and evaluate the role of the MiCK assay in guiding chemotherapy of cancer patients.
