First, we screened the expression levels of the cellular receptors for GALV (PiT1) and AMLV (PiT2) in human cell lines by qPCR (data not shown), and found that the mRNA levels of both receptors were high in most cancer cell lines, including Hep3B cells (>100-fold compared with fibroblasts). Here, SLC20A1 is linked to cancer.