Lovastatin (LOV), the drug recently introduced to treat hypercholesteremia, inhibits the synthesis of mevalonic acid. The effects ofLOV on the cell cycle progression of the human bladder carcinoma T24 cell line expressing activated p21 were investigated. At a concentration of 2-10 jpM, LOV arrested cells in GI and also prolonged-or arrested a minor fraction of cells in-the G2 phase of the cell cycle; at a concentration of 50 p&M, LOV was cytotoxic. The cytostatic effects were reversed by addition of exogenous mevalonate. Cells arrested in the cycle by LOV were viable for up to 72 hr and did not show any changes in RNA or protein content or chromatin condensation, which would be typical of either unbalanced growth or deep quiescence. The expression of the proliferation-associated nuclear proteins Ki-67 and p105 in these cells was reduced by up to 72% and 74%, respectively, compared with exponentially growing control cells. After removal ofLOV, the cells resumed progression through the cycle, they entered S phase asynchronously after a lag of~'6 hr.Because mevalonate is essential for the posttranslational modification (isoprenylatdon) of p2l', which in turn allows this protein to become attached to the cell membrane, the data suggest that the LOV-induced GI arrest may be a consequence of the loss of the signal trnsduction capacity of p21a. Indeed, while exposure of cells to LOV had no effect on the cellular content of p21 (detected immunocytochemically), it altered the intracellular location ofthis protein, causing its dissociation from the cell membrane and translocation toward the cytoplasm and nucleus. However, it is also possible that inhibition of isoprenylation of proteins other than p2l' (e.g., nuclear lamins) by LOV may be responsible for the observed suppression of growth of T24 cells.The drug lovastatin (LOV) was introduced to the clinic nearly 3 years ago to treat hypercholesteremia. It suppresses synthesis of mevalonic acid by blocking activity of 3-hydroxy-3-methylglutaryl-CoA reductase (EC 1.1.1.88). However, because mevalonic acid is also in the pathway of posttranslational modification of proteins that involve attachment of thioether-linked prenyl groups (isoprenylations) such as farnesylation (1), LOV, in addition to its anticholesterol activity, is also an inhibitor of these modifications.Recent evidence indicates that isoprenylation of the ras oncogene-encoded protein (p211a5) is an essential step enabling this protein to anchor to the cell membrane (2, 3).Because the signal transduction activity of p215, which is associated with its regulatory role in the cell cycle, requires its membrane attachment, suppression of the isoprenylation is expected to interfere with the cellular function of this protein. We have presently studied the effects of LOV on the cell cycle of the human bladder carcinoma T24 cell line. These cells express the activated form ofp21' resulting from a single point mutation of this oncogene (4,5). Since the cultures were maintained in the presence of fetal calf serum, ...

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We examined molecular events and morphological features associated with apoptosis induced by anthraquinone anticancer drugs aclarubicin, mitoxantrone and doxorubicin in two spontaneously immortalized cell lines (NIH 3T3 and B14) in relation to cytotoxicity of these drugs. The investigated cells showed similar sensitivity to aclarubicin but different sensitivity to doxorubicin and mitoxantrone: mitoxantrone was the most cytotoxic drug in both cell lines. All three drugs triggered both apoptosis and necrosis but none of these processes was positively correlated with their cytotoxicity. Apoptosis was the prevalent form of cell kill by aclarubicin, while doxorubicin and mitoxantrone induced mainly the necrotic mode of cell death. The extent and the timing of apoptosis were strongly dependent on the cell line, the type of the drug and its dose, and were mediated by caspase-3 activation. A significant increase in caspase-3 activity and the percentage of apoptotic cells, oligonucleosomal DNA fragmentation, chromatin condensation and formation of apoptotic bodies was observed predominantly in B14 cells. NIH 3T3 cells showed lesser changes and a lack of DNA fragmentation. Aclarubicin was the fastest acting drug, inducing DNA fragmentation 12 h earlier than doxorubicin, and 24 h earlier than mitoxantrone. Caspase-3 inhibitor Ac-DEVD-CHO did not show any significant effect on drug cytotoxicity and DNA nucleosomal fragmentation.

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