A new
lectin with the potent mitogenic and in vitro anti-proliferative activity was isolated from the tubers of a wild monocotyledonous plant Sauromatum venosum (Schott), from the family Araceae, by affinity chromatography on the
asialofetuin linked amino-activated
silica beads. The apparent native molecular mass of S. venosum
lectin (SVL), as determined by gel filtration chromatography, was 54 kDa. In HPLC, size exclusion and
cation exchange chromatography, SVL gave a single peak and also a single band of 13.5 kDa in SDS-PAGE, pH 8.3, under reducing and non-reducing conditions, indicating that the
lectin is composed of four identical subunits. S. venosum
lectin agglutinated rabbit, rat, sheep and guinea pig erythrocytes but reacted with goat erythrocytes after the
neuraminidase treatment. However, SVL was unable to agglutinate human
ABO blood group erythrocytes even
after treatment with
neuraminidase. SVL was inhibited by N-acetyl-D-
Lactosamine (LacNAc), which is an important marker in various
carcinomas and a complex desialylated
glycoprotein,
asialofetuin. The
amino acid composition showed that
lectin contained a high amount of
aspartic acid and
glycine but totally devoid of
cysteine. However, trace amounts of
methionine was present. The
lectin showed a potent mitogenic response towards BALB/c splenocytes and human lymphocytes. As the mitogenic stimulation was more than that of Con A, a standard well-known plant
mitogen and the response of this
lectin was almost double than that of Con A. This
lectin is endowed with proliferation of T cells as revealed by
IL-2 bioassay but showed no production of
immunoglobulins thus indicating the non-stimulation of B cells. SVL significantly inhibited the proliferation of murine
cancer cell-lines, i.e., WEHI-279 to 84.6%, J774 to 81%, P388D1 to 74% and A-20 to 47%. In addition, the in vitro anti-proliferative activity of SVL was also evaluated against nine human
cancer cell lines representing different organs and tissues namely, T-47D (breast), SiHa (cervix), SK-N-MC (CNS), SK-N-SH (CNS), SW-620 (colon), HT-29 (colon), HEP-2 (liver), OVCAR-5 (ovary) and PC-3 (prostate). SVL showed a significant inhibition towards the entire cell lines except the cell lines from CNS, which showed partial response in comparison to a standard anticancer
drug adriamycin which was used at a concentration of 5 x 10(-5) M. Thus the anti-proliferative ability of SVL may be helpful in identification of new
lectin probes that can lead to better understanding in the detection and study of certain types of
cancer.