Breast cancer is the most common type of
cancer, predominantly among women over 20, whereas colo-
rectal cancer occurs in both men and women over the age of 50.
Chemotherapy of both
cancers affect rapidly growing normal as well as
cancer cells.
Cancer cells are non-apoptotic. Seven anti-
cancer agents (cis -platin,
Tamoxifen,
Melphalan,
Betulinic acid, D-
PDMP, L-
PPMP, and GD3) have been tested with human breast (SKBR3) and colon (Colo-205)
carcinoma cells for their apoptotic effect and found to be positive by several assay systems. Colo-205 cells were obtained from ATCC, and the SKBR3 cells were a gift from the Cleveland Clinic. All of these six agents killed those two cell lines in a dose-dependent manner. In the early apoptotic stage (6 h), these cells showed only a flopping of
phosphatidylserine on the outer lamella of the plasma membranes as evidenced by the binding of a novel
fluorescent dye PSS-380. After 24 h of the treatment, those apoptotic cells showed damage of the plasma as well as the nuclear membrane as evidenced by binding of
propidium iodide to the nuclear
DNA.
DNA laddering assay viewed further breakdown of
DNA by 1%
agarose gel electrophoresis analysis. It is concluded that during apoptosis the signaling by Mitochondrial Signaling Pathway (MSP) is stimulated by some of these agents.
Caspase 3 was activated with the concomitant appearance of its p17
polypeptide as viewed by Westernblot analyses. Incorporation of radioactivity from [U-(14)C]-
L-serine in total
sphingolipid mixture was observed between 2 and 4 micromolar concentrations of most of the agents except ci s-platin. However, apoptosis in
carcinoma cells in the presence of cis -platin is induced by a
caspase 3 activation pathway without any increase in synthesis of
ceramide.