The ClpP activator ONC‐212 (TR‐31) inhibits BCL2 and B‐cell receptor signaling in CLL

Abstract

Despite advances in therapy, a significant proportion of patients with chronic lymphocytic leukemia (CLL) relapse with drug resistant disease. Novel treatment approaches are required, particularly for high risk disease. The imipridones represent a new class of cancer therapy that has been investigated in pre‐clinical and clinical trials against a range of different cancers. We investigated the effects of the imipridone, ONC‐212, against CLL cells cultured under conditions that mimic aspects of the tumour microenvironment and a TP53ko CLL cell line (OSU‐CLL‐TP53ko). ONC‐212 induced dose‐dependent apoptosis, cell cycle arrest and reduced the migration of CLL cells in vitro, including cells from patients with TP53 lesions and OSU‐CLL‐TP53ko cells. The effects of ONC‐212 were associated with protein changes consistent with activation of the mitochondrial protease, CIpP, and the integrated stress response. We also observed inhibition of pathways downstream of the B‐cell receptor (BCR) (AKT and MAPK‐ERK1/2) and a pro‐apoptotic shift in the balance of proteins of the BCL2 family of proteins (BCL2, MCL1, BCLxL, BAX and NOXA). In conclusion, the study suggests ONC‐212 may represent an effective treatment for high risk CLL disease by inhibiting multiple facets of the BCR signaling pathway and the pro‐survival effects of the BCL2‐family proteins.

The CIpP activator, TR-57, is highly effective as a single agent and in combination with venetoclax against CLL cells in vitro

“…TR-57 had both cytotoxic (Figure 1) and cytostatic (Figure 3) effects against primary CLL cells and CLL cell lines, including a line in which TP53 was knocked-out using CrispR-Cas9 (OSU-CLL-TP53ko). In comparison to data from our previous study (Fatima, et al 2021), TR-57 was significantly (P = 0.0001) more cytotoxic towards CLL cells than ONC-212, with IC50 values of 287 ± 50.5 nM and 404 +/-70.6 nM, respectively against primary CLL cells in co-culture with CD40L-fibroblasts. The cytotoxic effects of TR-57 against CLL cells under in vitro conditions that mimic the tumour microenvironment were consistent with the ability of the drug to counter the supportive effects of the stromal cells and induce a pro-apoptotic shift in expression of MCL-1, BCL-xL, NOXA and BAX and phosphorylation of AKT and ERK1/2-MAPK (Figure 4).…”

“…Studies suggest drugs that target the unfolded protein response (UPR) and upregulate caseinolytic protease (ClpP) activity may be an effective treatment option for several cancers (Graves, et al 2019). Our previous study (Fatima, et al 2021) and development of the potent . CC-BY-ND 4.0 International license made available under a (which was not certified by peer review) is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity.…”

“…Studies suggest drugs that target the unfolded protein response (UPR) and upregulate caseinolytic protease (ClpP) activity may be an effective treatment option for several cancers (Graves, et al 2019). Our previous study (Fatima, et al 2021) and development of the potent CIpP-activating, TR-compounds prompted the current study, in which we examined the effects of TR-57 against CLL cells, as a single agent and in combination with venetoclax. TR-57 had both cytotoxic (Figure 1) and cytostatic (Figure 3) effects against primary CLL cells and CLL cell lines, including a line in which TP53 was knocked-out using CrispR-Cas9 (OSU-CLL-TP53ko).…”

“…In our recent study, we demonstrated that the imipridone ONC-212 (TR-31) induces expression of ClpP, inhibits key signalling pathways downstream of the BCR and induces a pro-apoptotic shift in the expression of proteins of the BCL-2 family in CLL cells, under in vitro conditions that mimic the TME (Fatima, et al 2021). These data provided the rationale for the current study, in which we investigated the effects of TR-57 towards CLL cells under conditions that mimic the pro-survival effects of the TME.…”

Mitochondrial ATP-Dependent Proteases—Biological Function and Potential Anti-Cancer Targets

“…As for the mechanism of action, imipridones, including ONC201, ONC212, and TR compounds were identified as ClpP activators [ 25 , 183 , 184 ]. Like ADEPs, ONC201 non-covalently binds to the hydrophobic pocket between ClpP subunits and opens the axial entrance [ 25 ].…”