Provided are methods of treating a disease or condition associated with an increased level of expression of a protein disulfide-isomerase A3 (PDIA3) by administering to a subject with an increased level of expression of PDIA3 a PDI A3-inhibiting effective amount of a thiazolide compound, such as nitazoxanide or tizoxanide. Also provided are methods of screening for therapeutic agents based on PDIA3 inhibition.