It is suggested that recombinant galectin 9 (rGal 9), produced in host Escherichia coli, exhibits an immune system-mediated action and a direct action on tumor cells (i.e., activity of inducing the intercellular adhesion and apoptosis of the tumor cells), thereby potent in inducing the inhibition of cancer metastasis and reduction. Moreover, the rGal 9 exerts no efficacy on non-activated lymphocytes but can induce apoptosis in activated T cells, in particular, CD4-positive T cells causing an excessive immune response. The rGal 9 has a further potent apoptosis-inducing property on synovial cells participating in joint deformation in rheumatism, etc. In the rGal 9, however, a link domain linking two CRDs is highly susceptible to protease and, therefore, is very easily digestible with the enzyme, thereby losing the above activities. Thus, there is a need for a more stabilized molecule in view of further studies. Modification of the link domain linking two CRDs in galectin 9 provides a modified molecule having an elevated activity without any undesirable effects on the above activities.