CAD204520 Targets NOTCH1 PEST Domain Mutations in Lymphoproliferative Disorders

NOTCH1 PEST domain mutations are often seen in hematopoietic malignancies, including T-cell acute lymphoblastic leukemia (T-ALL), chronic lymphocytic leukemia (CLL), splenic marginal zone lymphoma (SMZL), mantle cell lymphoma (MCL), and diffuse large B-cell lymphoma (DLBCL). These mutations play a key role in the development and progression of lymphoproliferative tumors by increasing the Notch signaling and, consequently, promoting cell proliferation, survival, migration, and suppressing apoptosis. There is currently no specific treatment available for cancers caused by NOTCH1 PEST domain mutations. However, several NOTCH1 inhibitors are in development. Among these, inhibition of the Sarco-endoplasmic Ca2+-ATPase (SERCA) showed a greater effect in NOTCH1-mutated tumors compared to the wild-type ones. One example is CAD204520, a benzimidazole derivative active in T-ALL cells harboring NOTCH1 mutations. In this study, we preclinically assessed the effect of CAD204520 in CLL and MCL models and showed that NOTCH1 PEST domain mutations sensitize cells to the anti-leukemic activity mediated by CAD204520. Additionally, we tested the potential of CAD204520 in combination with the current first-line treatment of CLL, venetoclax, and ibrutinib. CAD204520 enhanced the synergistic effect of this treatment regimen only in samples harboring the NOTCH1 PEST domain mutations, thus supporting a role for Notch inhibition in these tumors. In summary, our work provides strong support for the development of CAD204520 as a novel therapeutic approach also in chronic lymphoproliferative disorders carrying NOTCH1 PEST domain mutations, emerging as a promising molecule for combination treatment in this aggressive subset of patients.

Β-blockers activate autophagy on infantile hemangioma-derived endothelial cells in vitro

The mechanisms underlying the success of propranolol in the treatment of infantile hemangioma (IH) remain elusive and do not fully explain the rapid regression of hemangiomatous lesions following drug administration. As autophagy is critically implicated in vascular homeostasis, we determined whether β-blockers trigger the autophagic flux on infantile hemangioma-derived endothelial cells (Hem-ECs) in vitro.

MATERIAL AND METHODS

Fresh tissue specimens, surgically removed for therapeutic purpose to seven children affected by proliferative IH, were subjected to enzymatic digestion. Cells were sorted with anti-human CD31 immunolabeled magnetic microbeads. Following phenotypic characterization, expanded Hem-ECs, at P2 to P6, were exposed to different concentrations (50 μM to 150 μM) of propranolol, atenolol or metoprolol alone and in combination with the autophagy inhibitor Bafilomycin A1. Rapamycin, a potent inducer of autophagy, was also used as control. Autophagy was assessed by Lysotracker Red staining, western blot analysis of LC3BII/LC3BI and p62, and morphologically by transmission electron microscopy.

RESULTS

Hem-ECs treated with either propranolol, atenolol or metoprolol displayed positive LysoTracker Red staining. Increased LC3BII/LC3BI ratio, as well as p62 modulation, were documented in β-blockers treated Hem-ECs. Abundant autophagic vacuoles and multilamellar bodies characterized the cytoplasmic ultrastructural features of autophagy in cultured Hem-ECs exposed in vitro to β-blocking agents. Importantly, similar biochemical and morphologic evidence of autophagy were observed following rapamycin while Bafilomycin A1 significantly prevented the autophagic flux promoted by β-blockers in Hem-ECs.

CONCLUSION

Our data suggest that autophagy may be ascribed among the mechanisms of action of β-blockers suggesting new mechanistic insights on the potential therapeutic application of this class of drugs in pathologic conditions involving uncontrolled angiogenesis.

Identification of an Epi-metabolic dependency on EHMT2/G9a in T-cell acute lymphoblastic leukemia

Genomic studies have identified recurrent somatic alterations in genes involved in DNA methylation and post-translational histone modifications in acute lymphoblastic leukemia (ALL), suggesting new opportunities for therapeutic interventions. In this study, we identified G9a/EHMT2 as a potential target in T-ALL through the intersection of epigenome-centered shRNA and chemical screens. We subsequently validated G9a with low-throughput CRISPR-Cas9-based studies targeting the catalytic G9a SET-domain and the testing of G9a chemical inhibitors in vitro, 3D, and in vivo T-ALL models. Mechanistically we determined that G9a repression promotes lysosomal biogenesis and autophagic degradation associated with the suppression of sestrin2 (SESN2) and inhibition of glycogen synthase kinase-3 (GSK-3), suggesting that in T-ALL glycolytic dependent pathways are at least in part under epigenetic control. Thus, targeting G9a represents a strategy to exhaust the metabolic requirement of T-ALL cells.

Blockade of Oncogenic NOTCH1 with the SERCA Inhibitor CAD204520 in T Cell Acute Lymphoblastic Leukemia

The identification of SERCA (sarco/endoplasmic reticulum calcium ATPase) as a target for modulating gain-of-function NOTCH1 mutations in Notch-dependent cancers has spurred the development of this compound class for cancer therapeutics. Despite the innate toxicity challenge associated with SERCA inhibition, we identified CAD204520, a small molecule with better drug-like properties and reduced off-target Ca2+ toxicity compared with the SERCA inhibitor thapsigargin. In this work, we describe the properties and complex structure of CAD204520 and show that CAD204520 preferentially targets mutated over wild-type NOTCH1 proteins in T cell acute lymphoblastic leukemia (T-ALL) and mantle cell lymphoma (MCL). Uniquely among SERCA inhibitors, CAD204520 suppresses NOTCH1-mutated leukemic cells in a T-ALL xenografted model without causing cardiac toxicity. This study supports the development of SERCA inhibitors for Notch-dependent cancers and extends their application to cases with isolated mutations in the PEST degradation domain of NOTCH1, such as MCL or chronic lymphocytic leukemia (CLL).

Abstract B113: Selective blockade of oncogenic NOTCH1 with the new SERCA inhibitor CAD204520 in T-cell acute lymphoblastic leukemia

Given its oncogenic role in human cancers, Notch1 signaling has garnered increased attention as a therapeutic target. Several Notch modulators, including γ-secretase inhibitors, have shown therapeutic efficacy in preclinical tumor models. However, despite this promise, few of these candidates have shown clinical benefit in patients, in part due to tissue-dependent on-target toxicities from the repression of both mutant and wild type Notch proteins. The discovery of the P-type ATPase Sarco/Endoplasmic Reticulum Ca2+-ATPase (SERCA) as a modulator of Notch transport and activity suggested a new approach to treat T-cell Acute Lymphoblastic Leukemia (T-ALL) an aggressive cancer dependent on aberrant Notch1 activation. In fact, thapsigargin mediated SERCA inhibitions had a stronger effect on the most common type of activating NOTCH1 mutants compared to wild type. However, the consequence of thapsigargin binding to SERCA is a rapid disruption of Ca2+ homeostasis that might cause cardiac toxicity in human, suggesting the need to identify inhibitors with better drug-like properties and reduced off-target toxicity. From a small molecule screening of 191,000 P-type ATPase modulators for inhibition of the yeast S. cerevisiae H+-ATPase Pma1, 407 hits were counter screened for their ability to target Na+/K+-ATPase and the Ca2+-ATPase proteins. CAD204520 displayed ~25 and ~79 fold greater selectivity toward human SERCA compared to Na+/K+and H+-ATPase and emerged as a candidate for the development of novel anti-NOTCH1 agents. We demonstrated that CAD204520 impairs the proliferation of a panel of lymphoid malignancies carrying activating mutations in the NOTCH1 heterodimerization domain (HD, such as T-ALL) and/or deletions in the degradation domain (PEST, such as mantle cell lymphoma (MCL)). Similar to thapsigargin, CAD204520 causes a defect in NOTCH1 trafficking that results in an accumulation of full-length NOTCH1 and in a depletion of the activated form: ICN1. Consequently, the NOTCH1 targets, MYC, DTX1, were repressed as measured by qRT-PCR. In contrast, no effect at protein level was observed in T-ALL wild type NOTCH1. To assess the in vivo efficacy of CAD204520 we established xenografts from the SKW-3/KE-37 T-ALL cell line and demonstrated that drug’s treatment reduced circulating and tissue infiltrating human leukemia cells without causing heart-related off-target effects. Consistently preclinical toxicity studies in rat cardiomyocytes showed that compared to thapsigargin, CAD204520 minimally alters cell cardiac mechanical performance (~25%) suggesting that the heart will likely tolerate CAD204520 modulation in vivo. In fact, in CD1 mice exposed to CAD204520 (30 mg/Kg, BID for 21 days) no adverse clinical symptoms were found. A tempting hypothesis to explain for the variation of Ca2+ dependent toxicities seen in our studies is that thapsigargin and CAD204520 inhibit SERCA in distinct pockets. Consistently, docking poses showed that CAD204520 binds SERCA in the trans-membrane helices M1, M3 and M4 while thapsigargin in the M3, M5 and M7 groove. Consequently, thapsigargin and CAD204520 co-treatment resulted in synergistic anti-proliferative effect in T-ALL. In conclusion, this study supports the development of tolerated SERCA inhibitors for Notch dependent cancers and extends its application to cases with mutations in the PEST degradation domain such as MCL or chronic lymphocytic leukemia.

Citation Format: Marchesini Matteo, Andrea Gherli, Anne-Marie Lund Winter, Samuel Kitara, Anna Montanaro, Chiara Rompietti, Claudia Sorrentino, Donatella Stilli, Federica Rizzi, Luca Pagliaro, Kimberly Stegmaier, William Dalby-Brown, Giovanni Roti. Selective blockade of oncogenic NOTCH1 with the new SERCA inhibitor CAD204520 in T-cell acute lymphoblastic leukemia [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference on Molecular Targets and Cancer Therapeutics; 2019 Oct 26-30; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2019;18(12 Suppl):Abstract nr B113. doi:10.1158/1535-7163.TARG-19-B113