HDAC6 and neoplasm: These findings highlightits efficacy in targeting both fully developed, heterogeneous tumormasses (MTSs) and tumor formations enriched in tumor-initiating cells(sc-TSs), which are associated with increased metastatic potential.Furthermore, comparison between compound 17 (dual HDAC6/Hsp90inhibitor) with its precursor 1 (HDAC6 inhibitor), tubastatin-A(HDAC6 inhibitor), and geldanamycin (Hsp90 inhibitor), both as singleor combined agents, shows that compound 17 is more effectivein reducing the size and number of sc-TSs.