HSP90AB1 and neoplasm: Moreover, the interaction of Hsp90β with MAST1 could repress MAST1 ubiquitination at lysines 317 and 545 by CHIP and curbed proteasomal degradation; combined inhibition of Hsp90 and MAST1 could further disrupt MAST1 activity, which enhances cisplatin-triggered tumor growth arrest [14].