Reversible inhibition of proliferation of epithelial cell lines by Agaricus bisporus (edible mushroom) lectin.
Galactosyl beta-1,3-N-acetyl galactosamine (Gal beta-1,3-GalNAc) (Thomsen Friedenreich antigen), the Class I core sequence in O-linked oligosaccharide chains, behaves as an oncofetal antigen showing increased expression in many epithelial malignancies. Previous work has shown that peanut agglutinin (PNA), a lectin that binds Gal beta-1,3-GalNAc, stimulates proliferation in HT-29 (human colon cancer) cells and normal human colonic epithelium and this implies that cell surface glycoproteins which express Gal beta-1,3-GalNAc may play an important role in the regulation of epithelial cell proliferation. We have now studied the effect on epithelial cells of another dietary Gal beta-1,3-GalNAc-binding lectin, the edible mushroom Agaricus bisporus lectin (ABL). This differs from PNA in its ability to bind also to sialylated Gal beta-1,3-GalNAc. In contrast to PNA, ABL (25 micrograms/ml) inhibited incorporation of [3H]-thymidine into DNA of HT29 colon cancer cells by 87% (95% confidence limit, 85-89%), Caco-2 colon cancer cells by 16% (95% confidence limit, 12-20%), MCF-7 breast cancer cells by 50% (95% confidence limit, 47-52%), and Rama-27 rat mammary fibroblasts by 55% (95% confidence limit, 51-60%) when these cells were grown for 24 h in serum-free medium. When assessed by cell count, similar inhibition of proliferation of HT29 cells by ABL was found. In the presence of 2% fetal calf serum (which contains the ABL-binding glycoprotein fetuin), the inhibitory effect of ABL on cell proliferation was still demonstrable but at increased ABL concentration (60 micrograms/ml for 49% inhibition). Ten micrograms/ml ABL completely abolished the stimulatory effect on [3H]thymidine incorporation of epidermal growth factor (100 pg/ml) and PNA (25 micrograms/ml) and markedly inhibited the stimulatory effect of insulin (50 ng/ml). ABL (0.2 mg/ml) caused no cytotoxicity to HT29, MCF-7, and Rama-27 cells as measured by trypan blue exclusion, and inhibition of proliferation in HT29 cells caused by 50 micrograms/ml ABL was reversible after removal of the lectin. Binding studies with 125I-labeled ABL suggested a single class of binding site with an apparent Kd value of (4.12 +/- 0.29) x 10(-7) M with (3.6 +/- 0.3) x 10(7) binding sites/cell. A. bisporus lectin is a reversible noncytotoxic inhibitor of epithelial cell proliferation which deserves study as a potential agent for cancer therapy.
Yu
L
L
Department of Medicine, University of Liverpool, United Kingdom.
Fernig
D G
DG
Smith
J A
JA
Milton
J D
JD
Rhodes
J M
JM
D000230:Adenocarcinoma; D000328:Adult; D000364:Agaricus; D000368:Aged; D000818:Animals; D010367:Arachis; D001665:Binding Sites; D001943:Breast Neoplasms; D002240:Carbohydrate Sequence; D002455:Cell Division / Q000187:drug effects*; D002462:Cell Membrane / Q000378:metabolism; D002470:Cell Survival / Q000187:drug effects; D003110:Colonic Neoplasms; D004273:DNA, Neoplasm / Q000096:biosynthesis / Q000187:drug effects*; D004187:Disaccharides; D004305:Dose-Response Relationship, Drug; D004815:Epidermal Growth Factor / Q000494:pharmacology; D004847:Epithelial Cells; D004848:Epithelium / Q000187:drug effects; D005260:Female; D006801:Humans; D037102:Lectins / Q000378:metabolism / Q000494:pharmacology*; D008297:Male; D008321:Mammary Glands, Animal; D008969:Molecular Sequence Data; D019887:Peanut Agglutinin; D037121:Plant Lectins; D051381:Rats; D013936:Thymidine / Q000378:metabolism; D014407:Tumor Cells, Cultured
C041433:Agaricus lectins; D004273:DNA, Neoplasm; D004187:Disaccharides; D037102:Lectins; D019887:Peanut Agglutinin; D037121:Plant Lectins; D004815:Epidermal Growth Factor; D013936:Thymidine