EIF4EBP1 and cancer: For example, immunohistochemical staining of human breast cancer for phospho-4E-BP1 (Thr 70) and phospho-S6 (Ser 240/244), as markers of mTORC1 activity, shows a marked heterogeneity among cancer cells, exhibiting either a strong or a weak staining in the same tumor [84, 85].