Compounds and combinations of them that inhibit phosphatidic phosphohydrolase (PAP) enzymatic activity are formulated into pharmaceuticals useful in cancer treatment. Inhibitors of PAP can be used for blocking the progression of cancers that depend on the epidermal growth factor receptor (EGFR), its oncogenic variants and other members of its ErbB tyrosine kinase receptor family, through induction of their endocytosis, thus making them inaccessible to the extracellular stimuli that promote maintenance and progression of cancer.