Finally, we assessed the levels of p-4EBP1, a surrogate marker of mTORC1 activation, and SLC38A1 in a collection of human HB specimens (n = 28) by immunohistochemistry (Figure 7). Strikingly, strong immunoreactivity for p-4EBP1 and SLC38A1 proteins was detected in most tumor tissues when compared with corresponding non-tumorous surrounding liver tissues (Figure 7). Specifically, increased levels of SLC38A1 and p-4EBP1 were detected in 20 of 28 (71.4%) and 23 of 28 (82.1%) HB specimens, respectively. Of note, 18 of 20 (90%) HB showing upregulation of SLC38A1 also displayed elevated levels of p-4EBP1. No significant association was found between the levels of SLC38A1 and/or p-4EBP1 with clinicopathologic features of the patients, including age, gender, etiology, histology subtype, recurrence or lung metastasis (data not shown).