A simple technique for quantifying apoptosis in 96-well plates.

BACKGROUND: Analyzing apoptosis has been an integral component of many biological studies. However, currently available methods for quantifying apoptosis have various limitations including multiple, sometimes cell-damaging steps, the inability to quantify live, necrotic and apoptotic cells at the same time, and non-specific detection (i.e. "false positive"). To overcome the shortcomings of current methods that quantify apoptosis in vitro and to take advantage of the 96-well plate format, we present here a modified ethidium bromide and acridine orange (EB/AO) staining assay, which may be performed entirely in a 96-well plate. Our method combines the advantages of the 96-well format and the conventional EB/AO method for apoptotic quantification. RESULTS: We compared our method and the conventional EB/AO method for quantifying apoptosis of suspension cells (Jurkat) and adherent cells (A375) under normal growth and apoptosis-inducing conditions. We found that our new EB/AO method achieved quantification results comparable to those produced using the conventional EB/AO method for both suspension and adherent cells. CONCLUSION: By eliminating the detaching and washing steps, our method drastically reduces the time needed to perform the test, minimizes damage to adherent cells, and decreases the possibility of losing floating cells. Overall, our method is an improvement over the currently available techniques especially for adherent cells.

Lovastatin-induced apoptosis in human melanoma cell lines.

The cholesterol-lowering medications, statins, inhibit cellular proliferation and induce apoptosis in an array of cancer cell lines, including melanoma. We investigated the apoptotic mechanism of lovastatin on human melanoma cell lines in vitro. The cytotoxicity of statins on multiple cell lines was examined by Cell Titer 96 Aqueous One solution cell proliferation assay (MTS assay). Apoptosis was assayed by ethidium bromide and acridine orange morphologic assays, an Annexin V apoptosis detection kit and active caspase 3 assays. Farnesyl pyrophosphate and geranylgeranyl pyrophosphate add-back experiments were performed to better define the molecular mechanisms mediating lovastatin cytotoxicity. Lovastatin caused cytotoxicity in human and murine melanoma cells, but did not induce toxicity in an epidermoid carcinoma cell line A431. For human melanoma cells, lovastatin precipitated cell rounding, increased the percentage of apoptotic cells detected by ethidium bromide and acridine orange staining and by the Annexin V apoptosis detection kit, and resulted in a 50-fold increase in active caspase 3, corroborating that lovastatin induced apoptosis. Adding back geranylgeranyl pyrophosphate, but not farnesyl pyrophosphate, reversed the effects of lovastatin in A375 cells. Of the five statins tested, pravastatin was least effective in killing melanoma cells. Lovastatin induced caspase-dependent apoptosis in multiple melanoma cell lines via a geranylation-specific mechanism. This study supports a possible role of lovastatin as a therapeutic, adjuvant or chemopreventive agent for melanoma.

Fast response temperature measurement and highly reproducible heating methods for 96-well plates.

Hyperthermia, the procedure of exposing cells to a temperature between 42 degrees and 49 degrees C, has been shown to be a promising approach for cancer treatment. To understand the underlying mechanisms of hyperthermic killing of cancer cells, it is critical to have an accurate temperature measurement technique and a heating method with high reproducibility. To this end, we have developed a method using fine thermocouples with fast response time to measure the temperatures in multiple wells of a 96-well plate. The accuracy of temperature measurement was +/- 0.2 degree C. Such a capability allows a complete record of the time and temperature of the treatment procedure and helps define an accurate thermal dose. We have also compared several methods for heating 96-well plates and found that use of copper blocks in contact with the lower surface of the 96-well plate in an incubator provides a highly reproducible heating method. The common method of using water bath to heat cells in vitro resulted in a decrease of cell viability even at the control temperature of 37 degrees C and a decrease in the reproducibility of certain biological assays. In summary, using these improved techniques, proposed thermal dose can be defined more precisely, and highly reproducible heating in vitro can be achieved.