Malignant mesothelioma (MM), an asbestos-associated cancer with no known cure, is a highly aggressive tumor causing profound morbidity and nearly universal mortality. Extracellular matrix (ECM) matrix metalloproteinases (MMPs) produced by tumor and stromal cells play a key role in tumor invasion and metastasis. Prevention of ECM degradation by MMP inhibition has been shown to be a promising therapeutic approach to inhibition of cancer development. Based on reported anticancer properties, the authors investigated the effect of a mixture (NM) containing lysine, proline, ascorbic acid, and green tea extract on MM cell line MSTO-211 H proliferation (by [MTT] [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide] assay), MMP secretion (by gelatinase zymography), invasion (through Matrigel), and morphology (by hematoxylin and eosin [H&E] staining). MMP-2 and phorbol 12-myristate 13-acetate (PMA)-induced MMP-9 secretion were inhibited by NM in a dose-dependent fashion, with virtual total inhibition at 500 microg/ml NM. Invasion through Matrigel was inhibited at 50, 100, and 500 microg/ml by 27%, 36%, and 100%, respectively. NM was not toxic to the MM cell line, and H&E staining did not indicate any changes at and below 100 microg/ml concentration. In conclusion, NM significantly inhibited MM cell MMP secretion and invasion-both important parameters for cancer prevention, suggesting NM is an effective treatment strategy for MM.