A Lectin with Highly Potent Inhibitory Activity toward Breast Cancer Cells from Edible Tubers of Dioscorea opposita cv. Nagaimo

Abstract

A 70-kDa galactose-specific lectin was purified from the tubers of Dioscorea opposita cv. nagaimo. The purification involved three chromatographic steps: anion exchange chromatography on a Q-Sepharose column, FPLC-anion exchange chromatography on a Mono Q column, and FPLC-gel filtration on a Superdex 75 column. The purified nagaimo lectin presented as a single 35-kDa band in reducing SDS-PAGE while it exhibited a 70-kDa single band in non-reducing SDS-PAGE suggesting its dimeric nature. Nagaimo lectin displayed moderate thermostability, retaining full hemagglutinating activity after heating up to 62°C for 30 minutes. It also manifested stability over a wide pH range from pH 2 to 13. Nagaimo lectin was a galactose-specific lectin, as evidenced by binding with galactose and galactose-containing sugars such as lactose and raffinose. The minimum concentration of galactose, lactose and raffinose required to exert an inhibitory effect on hemagglutinating activity of nagaimo lectin was 20 mM, 5 mM and 40 mM, respectively. Nagaimo lectin inhibited the growth of some cancer cell lines including breast cancer MCF7 cells, hepatoma HepG2 cells and nasopharyngeal carcinoma CNE2 cells, with IC50 values of 3.71 µM, 7.12 µM and 19.79 µM, respectively, after 24 hour treatment with nagaimo lectin. The induction of phosphatidylserine externalization and mitochondrial depolarization indicated that nagaimo lectin evoked apoptosis in MCF7 cells. However, the anti-proliferative activity of nagaimo lectin was not blocked by application of galactose, signifying that the activity was not related to the carbohydrate binding specificity of the lectin.

Anti-insect potential of a lectin from the tuber, Dioscorea mangenotiana towards Eldana saccharina (Lepidoptera: Pyralidae)

“…D. mangenotiana lectin was observed to be stable at both acidic and physiological pH (2 -9) but activity was almost completely lost at alkaline pH (9 -11) as shown in Figure 3B. This is similar to the report on the lectin from D. batatas, DB1 which was stable at pH 7 -9 and DB3 at pH 3 -9 (Mariam et al, 2004) but is contrary to the report on the lectin from D. opposita which displayed stability over a wider pH range (2 -13) (Chan and Ng, 2013). The lectin from Arisaema jacquemontii Blume was reported to be stable at pH 2.5 (Kaur et al, 2006a).…”

“…This suggests a homodimeric structure for the lectin. A dimeric galactose-specific lectin was also reported to have been purified from the tubers of D. opposita cv.nagaimo with subunit molecular weight of 35 kDa (Chan and Ng, 2013) while a tetrameric mannosebinding lectin with subunit molecular weight of 31 kDa was purified from D. batatas (Mariam et al, 2004).…”

Isolation and characterization of lectin from the leaves of Euphorbia tithymaloides (L.)

“…Our findings are also on the same line as lectins of ET were inhibited by D-galactose and lactose which shows galactose specificity. Similar inhibition was observed in Tridax procumbens (Ramteke & Patil 2005), tubers of Dioscorea opposite (Chan & Ng 2013) and Zizyphus oenoplia (Butle & Patil 2015).…”

Stimulation of dendritic cell maturation and induction of apoptosis in lymphoma cells by a stable lectin from buckwheat seeds

“…After incubation at room temperature for 30 min, the solutions were neutralized, and assay of hemagglutinating activity was performed as described above (Chan and Ng, 2013). For the heat stability test, the TBL solutions were heated at different temperatures (25°C-80°C) for 30 min and immediately cooled on ice.…”