Podophyllotoxin Derivatives Suppress Gain-of-function Of Ras/MAPK Pathway In Caenorhabditis Elegans And Their Toxicity

Podophyllotoxin and its derivatives are known to have important antineoplastic properties and used as chemotherapeutics in certain cancers, such as lymphoma, non-cell lung cancer, non-Hodgkin’s disease, leukemia, breast cancer, bladder cancer and testicular cancer. Their antitumor properties were due to two mechanisms of action:ⅰ) inhibited microtubule assembly during mitosis;ⅱ) formed "topoisomerase-drug-DNA" ternary complex to induce abnormal DNA recombinant. However, it is not known whether podophyllotoxin derivatives can suppress gain-of-function of Ras signaling pathway. Therefore, the multivulva (Muv) phenotype of Caenorhabditis elegans caused by a gain-of-function (gf) let-60 ras mutation is used to study antineoplastic properties of podophyllotoxin derivatives. As C. elegans has been widely used to evaluate toxicity, C. elegans was also used to test the toxicity of podophyllotoxin derivatives.Ten podophyllotoxin derivatives were tested in C. elegans on antineoplastic properties and their toxicity. Our results suggested that three podophyllotoxin derivatives of p-18, p-19 and p-21 could downregulate gain-of-function of Ras/MAPK signaling pathway and had toxicity on some degree.200μM of podophyllotoxin derivatives p-18 and p-21 and 400μM of podophyllotoxin derivatives p-19 can significantly suppress the formation of multivulva at a level of 7%,7% and 6%, respectively, lower than the vehicle control group.The toxicity results indicated that podophyllotoxin derivatives p-18 and p-21 did not affect on the body length, width and the position of vulva of C. elegans, yet p-19 only have effect on the body length of C. elegans.Three derivatives of podophyllotoxin could inhibit the activity of DNA topoisomeraseⅡ, the IC50 of p-18, p-19 and p-21 are 39.57±1.597μM,16.596±1.220μM and 376.99±2.576μM, respectively.According to results both in vivo and in vitro, the high efficacy and low toxicity of p-18 may be candidate compound and deserved to be further studied. Futhermore, p-21 at concentration higher than 200μM tended to have more efficacies and should be tested on further study.