HSPA5 and breast cancer: On one hand, cell surface-attached GRP78 is a breast cancer-promoting factor (see Section 4.2 for details) but, on the other hand, the presence of GRP78 on the breast cancer cell surface renders this chaperone targetable for GRP78-binding agents (e.g., chemical inhibitors, peptides, proteins or antibodies) which may exert the antitumor effects.