Possible explanations for the lack of synergy in PTEN-null HCC-38 cells include 1) the fact that it harbors a fusion gene comprised partly of the SLC22A1 gene (which codes for OCT1) fused with CUTA (from the Sanger mutation database), 2) it has the lowest level of phosphorylated EGFR among the 17 cell lines (data not shown) and, 3) existence of other unknown genetic alterations in the relevant signaling pathways. This evidence concerns the gene PTEN and hepatocellular carcinoma.