The reagent, pharmaceutical formulation, kit, and methods of the invention provides a new approach to alleviate or eliminate certain negative effects associated with the use of certain cancer treatment agents (e.g. chemotherapy therapeutics, etc.) or regimens (e.g. radio therapies, etc.), including stimulation of the hypoxic stress response in tumor cells. The reagent and pharmaceutical formulation of the invention relates to Na.sup.+/K.sup.+-ATPase inhibitors, such as cardiac glycosides, including bufadieneolides or their corresponding aglycones (e.g., proscillaridin, scillaren, and scillarenin, etc.), especially in oral formulations and/or solid dosage forms containing more than 1 mg of active ingredients.