Valosin-Containing Protein/p97 as a Novel Therapeutic Target in Acute Lymphoblastic Leukemia

Abstract

B acute lymphoblastic leukemia (B-ALL) cells are distinctively vulnerable to endoplasmic reticulum (ER) stress. Recently, inhibition of p97 was shown to induce ER stress and subsequently cell death in solid tumors and in multiple myeloma. We investigated the role of a novel, orally available, p97 inhibitor (CB-5083; Cleave Biosciences) in B-ALL. CB-5083 induced a significant reduction in viability in 10 human B-ALL cell lines, harboring the most common fusion-genes involved in pediatric and adult B-ALL, with IC50s ranging from 0.34 to 0.76 μM. Moreover, CB-5083 significantly reduced the colony formation of OP1 and NALM6 cells. Early and strong induction of apoptosis was demonstrated in BALL1 and OP1 cells, together with a robust cleavage of PARP. CB-5083 induced ER stress, as documented through: 1) prominent expression of chaperones (GRP78, GRP94, PDI, DNAJC3, and DNAJB9); 2) increased activation of IRE1-alpha, as demonstrated by the splicing of XBP1; and 3) activation of PERK, which resulted in a significant overexpression of CHOP, and its downstream genes. CB-5083 reduced the viability also in GRP78−/−, GRP94−/−, and XBP1−/− cells, suggesting that none of these proteins alone was strictly required for CB-5083 activity. Moreover, we showed that the absence of XBP1 (XBP1−/−) increased the sensitivity to CB-5083, leading to the hypothesis that XBP1 splicing counteracts the activity of CB-5083, probably mitigating ER stress. Finally, vincristine was synergistic with CB-5083 in both BALL1 and OP1 cells. In summary, the targeting of p97 with CB-5083 is a novel promising therapeutic approach that should be further evaluated in B-ALL.

Structural Basis of p97 Inhibition by the Site-Selective Anticancer Compound CB-5083

“…Treatment of tumor cells with CB-5083 leads to accumulation of polyubiquitinated proteins and retention of endoplasmic reticulum-associated degradation substrates. This antitumor activity of CB-5083 is also exhibited in multiple myeloma, B acute lymphoblastic leukemia, and hematologic and solid tumor models by activating the apoptotic arm of the UPS (Anderson et al, 2015;Bastola et al, 2017;Gugliotta et al, 2017;Gareau et al, 2018). In preclinical studies, CB-5083 also showed auspicious results against proteasome inhibitorresistant multiple myeloma patient samples (Le Moigne et al, 2017).…”

A robust strategy for proteomic identification of biomarkers of invasive phenotype complexed with extracellular heat shock proteins

“…Other chaperones were prominent in extracellular HSP complexes ( Table 2). All three sources contained abundant endoplasmic reticulum ATPase p97 (VCP) central to invasive phenotype (Cui et al 2015;Fu et al 2016) and modulation of proteotoxicity (Vekaria et al 2016;Gugliotta et al 2017). Protein disulfide isomerases P4HB and PDIA3 as well as peptidyl prolyl isomerases were also significant as exported chaperome components (Perrucci et al 2015;Lee and Lee 2017;Zou et al 2017;Stifani 2018).…”

Upregulation of valosin-containing protein (VCP) is associated with poor prognosis and promotes tumor progression of orbital B-cell lymphoma

“…Gugliotta et al found that CB5083 induced a significant reduction in viability in human B-ALL cell lines. Early and strong induction of apoptosis was also demonstrated in human B-ALL cell lines treated with CB5083 21. We will explore the effect of CB5083 on human BCL cells and its therapeutic effect on BCL in an animal model.…”