Ubiquitin B: an essential mediator of trichostatin A-induced tumor-selective killing in human cancer cells

Abstract

Although histone deacetylase inhibitors (HDACis) are emerging as a new class of anticancer agents, the mechanism of tumorselective killing by HDACi is not well understood. We used suppression of mortality by antisense rescue technique (SMART) to screen the key genes responsible for the tumor-selective killing by trichostatin A (TSA). Twenty-four genes were identified, the most significant of which was ubiquitin B (UbB). The expression of UbB was selectively upregulated by TSA in tumor cells, but not non-malignant cells. Further observation indicated that TSA induced a substantial dissipation of mitochondrial transmembrane potential, release of cytochrome c into the cytosol, and proteolytic cleavage of caspases-3/9 in HeLa cells, which was apparently mediated by ubiquitylation and the subsequent degradation of mitochondrial membrane proteins including BCL-2 and MCL-1. In contrast, knockdown of UbB expression inhibited the TSA-induced apoptotic cascade by abolishing TSA-induced ubiquitylation and the subsequent degradation of mitochondrial membrane proteins. Furthermore, apicidine, another HDACi, exhibited activity similar to that of TSA. Interestingly, TSA induced UbB-dependent proteasomal degradation of BCR-ABL fusion protein in K562 leukemic cells. Thus, our findings highlight the essential role of UbB and UbBdependent proteasomal protein degradation in HDACi-induced tumor selectivity. The mechanism provides a novel starting point for dissecting the molecular mechanism underlying the tumor selectivity of HDACi. 1-3 The clinical potential of HDACis has been well exemplified by the successful development of Vorinostat, which was recently approved by the US Food and Drug Administration for treatment of cutaneous T-cell lymphoma. 4 Despite the rapid clinical progress achieved, the mechanism of action of HDACis is not yet well understood. One of the central questions is how these agents selectively kill tumor cells while sparing normal cells. Identification of the critical intracellular targets responsible for the tumor selectivity of HDACis will further improve the design of optimized clinical protocols. More attractively, unraveling the potential 'death programs' selectively activated in tumor but not in normal cells will have broader implications for the understanding of tumorigenesis and the design of targeted therapies.Identification of the target genes essential for the selective induction of apoptosis in tumor cells has proven to be very difficult. It is well established that HDACis could affect up to 10% of all known genes at the transcriptional level. 5 In addition to HDACs, many non-histone proteins are also regulated by HDACis by influencing the molecular events of acetylation, protein-protein interactions and stability, and so on. Previously, a significant number of apoptotic and cell-cycle regulatory genes have been identified by different groups and proposed to be effectors responsible for the tumorselective action of HDACis. 6 In acute promyelocytic leukemia, however, preferential induction of tumor-n...

Loss of the novel mitochondrial protein FAM210B promotes metastasis via PDK4-dependent metabolic reprogramming

“…12 In this study, further analysis indicated that FAM210B was a novel mitochondria outer membrane protein and low expression of FAM210B obviously promoted malignant metastasis in vitro and in vivo. Depletion of FAM210B in ovarian cancer cells displayed elevated mitochondrial respiration and decreased glycolysis relative to control cells via the suppression of its downstream target, pyruvate dehydrogenase kinase 4 (PDK4).…”

Functional polyesters enable selective siRNA delivery to lung cancer over matched normal cells

“…To investigate the potential of functional polyesters to be cancer specific, we delivered a pan-toxic siRNA targeting UBB (27,28) to lung cancer and normal cells derived from single patient to discover cancer cell-selective NPs that show more efficacious siUBB delivery to tumor cells over matched normal cells ( Fig. 2A and SI Appendix, Table S1).…”

“…1A) in vitro and in vivo. We delivered siRNA targeting ubiquitin B (siUBB) (27,28), which causes cell death in all cell types to evaluate the delivery selectivity to HCC4017 tumor cells over HBEC30-KT normal cells. NPs were identified that showed selective cellular uptake to cancer cells over normal cells followed by reduced transport to lysosomes.…”

Synergistic Killing Effect between Vorinostat and Target of CD146 in Malignant Cells

“…Quantitative PCR was done in an ABI Prism 7000 using the SYBR Green PCR Master Mix (Sigma) as our previous description (27) with the following set of primers: CD146, 5′-CAG TCC TCA TAC CAG AGC CAA CAG-3′ and 5′-GGA CCA GGA TGC ACA CAA TCA-3′; E-cadherin, 5′-GGA TTG CAA ATT CCT GCC ATT C-3′ and 5′-AAC GTT GTC CCG GGT GTC A-3′; β-catenin, 5′-AAC GTT GTC CCG GGT GTC A-3′ and 5′-GGC AAG ATT TCG AAT CAA TCC AAC-3; integrin β1, 5′-GCC TTA CAT TAG CAC AAC ACC-3′ and 5′-CAT CTC CAG CAA AGT GAA AC-3; ICAM-1, 5′-CCT GAT GGG CAG TCA ACA GCT A-3′ and 5′-ACA GCT GGC TCC CGT TTC A-3′; VCAM-1, 5′-CGT GAT CCT TGG AGC CTC AAA TA-3′ and 5′-GAC GGA GTC ACC AAT CTG AGC A-3′; selectin-E, 5′-CAC TCA AGG GCA GTG GAC ACA-3′ and 5′-CAG CTG GAC CCA TAA CGG AAA C-3′; 18S, 5′-AGT CCC TGC CCT TTG ACA CA-3′ and 5′-GAT CCG AGG GCC TCA CTA AAC-3′. 18s RNA was used as an internal control.…”