P. noctiluca venom or its fractions (F1-F4) inhibit tumour cells proliferation. U87 cells were cultured for the indicated periods of time in the absence or in the presence of 10 μg/ml of venom or its fractions (F1-F4). Cell proliferation activity was evaluated by using MTT assay. Measurement of the absorbance was performed at a wavelength of 560 nm. The results are from a representative experiment of two performed in triplicate. *p < 0.05 compared with control (untreated cells).