In recent years the search for plant antitumor drugs by investigators supported by NCI has typically involved 1) the screening (by NCI contractors) of extracts for activity in the 3PS (P388) in vivo murine leukemia system followed by 2) the monitoring of fractionation by in vitro cytotoxicity assays (usually 9KB or 9PS). These bioassays typically require the maintenance of NCI contractors (for 3PS) and cell culture laboratories (for 9KB, 9PS) at the grantee institutions; they are expensive (ca. $200 for 3PS, $20 for 9KB, 9PS) and time-consuming (ca. 2 months for 3PS, 1-2 weeks for 9KB, 9PS). Recognizing these and other disadvantages, five years ago we developed and are now using two simple, in house, alternative bioassays: 1) the inhibition of crown gall plant tumors on discs of potato tubers and 2) lethality to brine shrimp. The potato disc assay substitutes for 3PS; it is more rapid (12-14 days), requires less sample, has excellent statistical correlation with 3PS (p=2 x 10-6, which is far superior to any known cytotoxicity sytem), is inexpensive (S10) and spares higher animals. The brine shrimp bioassay substitutes for cytotoxicity in fractionation monitoring (most anti-tumor compounds are toxic); it is rapid (24 hrs), inexpensive, requires no aseptic technique or technical training, spares the need for higher animal serum (which is used for 9KB, 9PS), and gives results in the form of LC50 values with 95% confidence intervals as an expression of test reliability (9KB, 9PS ED 50 values are highly variable). The combination of these two bioassays has led us, so far, to several antitumor compounds of which two have been supplied, at the request of NCI, for tumor panel evaluations and another has been submitted for the new battery of human cell line bioassays. The proposed research would permit us to continue this convincing demonstration that simple, in house, bioassays can lead to the isolation of new antitumor agents. The specific materials to be fractionated include selected active species of Annonaceae, Euphorbiaceae, and Leguminosae. The savings of time and money, statistical validation of results, and the sparing of warm-blooded animals (and their serum) are noted advantages of our approach. The work is especially timely as the NCI now plans to move away from extensive 3PS screening in favor of specific human cell line tests; such tests will be limited to submitted pure compounds with previously demonstrated bioactivity.
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