ALK and hepatocellular carcinoma: It should be noted that the concomitant expressions of midkine and ALK are not found in all the examined HCC cell lines, for example, PLC/PRF/5 cells show the maximum expression in both midkine and ALK, whereas MHCC97 cells, known as the most metastatic cells, expresses a higher level of midkine but a very low level of ALK.