Cryptophycin 52 has potent antimitotic, antiproliferative and cytotoxic activity in in vitro human tumor cell models. It is significantly more potent and less sensitive to multidrug resistance mechanisms than other antimitotic antitumor agents currently used in cancer therapy. These characteristics may translate into therapeutic advantages for the clinical use of cryptophycin 52 in cancer chemotherapy.

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Mast cell counts were performed on sections taken from the lungs of rats exposed by inhalation to different UICC samples of asbestos fibres for periods ranging from a few days to two years. A comparison of mast cell counts with grades of fibrosis showed that there is a sevenfold increase when there is interlobular linking of the fibrotic lesions (grade 5). Submesothelial mast cells showed a trend of increasing numbers with increasing exposure and with increasing subpleural thickening. Each type of asbestos produced a steady increase in mast cell numbers with increasing exposure. Two samples from animals exposed to chrysotile and two from animals exposed to amphiboles (crocidolite and amosite respectively) had 10 times as many cells as the control group after six and 24 monthe exposure. Another amphibole, anthophyllite, produced 50 times more cells than were present in the control -specimen appropriate for the heaviest exposure. These results are briefly discussed in relation to further exposure, smoking, and characteristics of the dusts.

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