Treatment with the eIF2α-phosphatase inhibitor SAL003 inhibits the colony forming efficiency of the breast tumor cells and substantially potentiates the anti-proliferative and anti-tumor effects of Trastuzumab on HER2+ breast and gastric tumors in culture and immune deficient mice (Fig. 5, 6; Supplementary Fig. 7). Here, ERBB2 is linked to neoplasm.