utility of P388 leukemia compared to B16 melanoma and colon carcinoma 38 for in vivo screening of plant extracts

We compared the value of using two in vivo solid tumor murine screening models, the B16 Melanoma and Colon 38 carcinoma, to the use of in vivo P388 leukemia in the detection of active extracts and in the prioritization of weak P388 active extracts. We found that, among a diverse group of 82 cytotoxc plant extracts negative in the P388 assay in vivo, only one had activity in B16 melanoma or Colon 38 and, among a group of 99 botanically diverse P388‐active extracts, none were active in either the B16 or Colon 38 models. We therefore conclude that the B16 and Colon 38 models in vivo are not useful for screening of crude extract and that, while the P388 leukemia may over‐predict useful leads due to its high sensitivity, its use as a first screen for crude extracts does not appear to result in missing solid tumor actives.