natural and synthetic compounds of formulae ia - ie having a lactone structure , in particular securolide , have been determined to be effective anti - tumor compounds which target the hrad9 gene and / or protein encoded thereby or complex containing the protein and / or the p53 gene and / or protein . securolide is cytoselective for mutants of hrad9 based on studies conducted in rad9 mutant yeast strains . securolide appears to interact with mutant hrad9 in cancer cells to produce dna lesions which result in apoptosis . studies have demonstrated that securolide is useful for treating proliferation disorders such as melanoma , leukemia , breast cancer , lung cancer , ovarian cancer , colon cancer , esophagus cancer , liver cancer , and lymphatic cancer , and to alleviate pain associated with the cancer . other compounds effective for the treatment of cancer and optionally pain associated therewith may also be identified using the same assays , for example , by screening for efficacy in assays using rad9 and / or p53 defective mutant yeasts .