Epidemiological evidence indicates that Brassica vegetables protect against
colorectal cancer. Brassicas contain
glucosinolates, the breakdown products of which exert antiproliferative effects against
cancer cells. We have examined the effects of
allyl-isothiocyanate (
AITC), a major breakdown product of the
glucosinolate sinigrin, on proliferation and death of
colorectal cancer cells. HT-29 colorectal cells were exposed to
AITC for 24 h and the number of adherent and detached cells determined. Both populations were analysed for cell-cycle characteristics and examined by light and electron microscopy for features of apoptosis and mitosis. Evidence of apoptosis was also determined by flow cytometric analysis of
Annexin V staining in the detached population of cells.
AITC-treated cells were also stained for
alpha-tubulin. Treatment caused cells to round up after 7 h of exposure and subsequently detach. At 24 h these cells were blocked in mitosis. Detached
AITC-treated cells showed no signs of apoptosis as assessed by morphological features or by
Annexin V staining but they did show evidence of disrupted
tubulin.
AITC inhibits proliferation of
cancer cells by causing mitotic block associated with disruption of
alpha-tubulin in a manner analogous to a number of chemotherapeutic agents.