ABSTRACT
Functional defects in mitochondria are involved in the induction of cell death in cancer cells. The process of programmed cell death may occur through the mechanisms of apoptosis. Several potential lead molecules such as Camptothecin [CPT] and its analogues have been isolated from plants with anticancer effect. The aim of the present study was to understand the necrotic effect versus apoptotic nature of CPT in HeLa cancer cells. The antiproliferative activity of CPT was estimated through 3-[4, 5- Dimethyl thiazol-2-yl]-2, 5-diphenyl tetrazolium bromide [MTT] assay and DNA fragmentation analysis using gel electrophoresis. Lactate Dehydrogenase [LDH] activity and cell morphology were assessed under control and CPT exposed conditions to evaluate the necrotic effect of CPT. The results showed that CPT inhibited the proliferation of HeLa cells in a dose-dependent manner with an Inhibitory Concentration 50% [IC50] of 0.08 +/- 0.012 microg/ml. However the significant [P<0.05] increase happens in LDH activity at concentrations 1x10-1microg/ml and above. Morphological changes showed that CPT in low concentrations induced an apoptotic mechanism of cell death, such as cell shrinkage and characteristic rounding of dying cells, while at high concentrations showed necrosis changes. The characteristic DNA ladder formation of CPT-treated cells in agarose gel electrophoresis confirmed the results obtained by light microscopy and LDH assay. Camptothecin as an anticancer drug may have antiproliferative effect on HeLa cancer cells in low concentrations, through its nature of induction of apoptosis. The border line between necrotic effect and apoptotic nature of CPT in HeLa cancer cells has been found to be at concentration of 1x10-1 microg/ml