PTK2 and leukemia: In cancers of the breast and liver, anti‐metastatic potentials are implicated[27, 28]; moreover, in the stomach, pancreas, and biliary tract, inhibition of proliferation or enhancement of tumor cell apoptosis is observed.[29, 30, 31] In contrast, a recent study reported that galectin‐9 promotes breast cancer metastasis through activating the focal adhesion kinase (FAK) pathway.[32] One study reported the involvement of galectin‐9 in TIC maintenance in leukemia,[17] but its role in the TIC of solid tumors has not been reported.