Lectins are a group of proteins which could recognize different sugar structures and specifically initiate reversible
binding with them. Lectins are universally expressed in different organisms and undertake important biological
roles. Understanding of their inherent roles and mechanisms that they employ has inspired researches with new ideas and
applications. For example, along with the revelation of their anti-insect function, plant lectins exhibit great potential in agriculture.
In human beings, lectins shoulder great missions in cell communication, differentiation and vesicle trafficking
etc., aberrant expression of lectins is always associated with diseases. Mannan-binding lectin deficiency leads to immune
disorder and liver sinusoidal endothelial cell lectin is involved in colorectal carcinoma liver metastasis. In this review, we
present two contradictory roles of lectins in human cancer: the promotive roles of homologous lectins and suppressive
roles of heterologous lectins in cancer development. Hopefully, this review will facilitate a better understanding of tumorigenesis
and provide references for cancer treatment.