A method for treating a patient suffering from an anti-HER2-resistant, MUC4+ HER2+ cancer is disclosed. For example, the method can be used to treat trastuzumab-resistant HER2+ breast cancer. In some embodiments, the method includes: (i) determining mucin-4 (MUC4) expression in cells of the patient； and (ii) if the MUC4 expression is greater than a predetermined-threshold, administering to the patient a therapeutically effective amount of a selective inhibitor of soluble tumor necrosis factor in combination with an anti-HER2 therapeutic agent, whereby said patient is treated.
