Caspase-like Research Articles

Drug Combination Studies of Isoquinolinone AM12 with Curcumin or Quercetin: A New Combination Strategy to Synergistically Inhibit 20S Proteasome.

In the eukaryotic cells, the ubiquitin-proteasome system (UPS) plays a crucial role in the intracellular protein turnover. It is involved in several cellular functions such as the control of the regular cell cycle progression, the immune surveillance, and the homeostasis. Within the 20S proteasome barrel-like structure, the catalytic subunits, β1, β2 and β5, are responsible for different proteolytic activities: caspase-like (C-L), trypsin-like (T-L) and chymotrypsin-like (ChT-L), respectively. The β5 subunit is particularly targeted for its role in antitumor activity: the synthesis of β5 subunit inhibitors could be a promising strategy for the treatment of solid and hematologic tumors. In the present work, we performed two combination studies of AM12, a recently developed synthetic proteasome inhibitor, with curcumin and quercetin, two nutraceuticals endowed of many pharmacological properties. We measured the combination index (CI), applying the Chou and Talalay method, comparing the two studies, from 50% to 90% of proteasome inhibition. In the case of the combination AM12 + curcumin, an increasing synergism was observed from 50% to 90% of proteasome inhibition, while in the case of the combination AM12 + quercetin an additive effect was observed only from 50% to 70% of β5 subunit inhibition. These results suggest that combining AM12 with curcumin is a more promising strategy than combining it with quercetin for potential therapeutic applications, especially in treating tumors.

Risk assessment of oral leukoplakia malignant transformation based on the ubiquitin-proteasome system indicators

Relevance. The ubiquitin-proteasome system controls the activity and stability of various cellular proteins that affect cellular homeostasis by the regulation of signalling cascades. The system activity is associated with the onset and progression of oral squamous cell carcinoma, as the system participates in the specific proteolysis of most intracellular proteins involved in cancer pathogenesis.Material and methods. The study included 61 patients (28 men and 33 women) aged 21 to 75 y.o. The study determined chymotrypsin-like (CTL) and caspase-like (CL) activities of circulating and intracellular proteasomes in blood serum and biopsy specimens taken from the oral mucosa by hydrolysis of the corresponding fluorogenic oligopeptide on a «Cytation1» multi-mode microplate reader-imager at an excitation wavelength of 360 nm and an emission of 460 nm, the specific activity of the proteasomes was expressed in units of activity.Results. The value of the specific chymotrypsin-like activity of circulating proteasomes in non-homogeneous leukoplakia and oral squamous cell carcinoma was 1.76 (p < 0.001) times and 2.27 (p < 0.001) times higher relative to the comparison group. Pairwise comparison of signs showed a statistically significant difference in chymotrypsinlike activity between the groups of non-homogeneous and homogeneous leukoplakia (p < 0.001), non-homogeneous leukoplakia and oral squamous cell carcinoma (p = 0.04). The values of specific chymotrypsin-like and caspase-like activities of intracellular proteasomes in biopsy specimens taken from the pathological focus in the groups of homogeneous, non-homogeneous leukoplakia and squamous cell carcinoma of the oral cavity were 1.6, 2.38, 3 (p = 0.002, p = 0.004, p = 0.03) and 1.5, 2.8 and 3.3 (p = 0.003, p = 0.012, p < 0.001) times higher compared to the control group.Conclusion. The proposed logit model for risk assessment of oral leukoplakia malignant transformation, based on the indicators of the ubiquitin-proteasome system, can improve the quality of diagnosis.

Design, synthesis, and biological evaluation of some novel naphthoquinone-glycine/β-alanine anilide derivatives as noncovalent proteasome inhibitors.

A series of novel noncovalent glycine/β-alanine anilide derivatives possessing 2-chloronaphthoquinone structure as a pharmacophoric unit were designed, synthesized, and evaluated for their antiproliferative and antiproteasomal activities against MCF-7 cell line, in vitro. According to biological activity results, all the target compounds showed antiproliferative activity in the range of IC50 = 7.10± 0.10-41.08 ± 0.14 μM and most of them exhibited inhibitory efficacy with varying ratios against the three catalytic subunits (β1, β2, and β5) presenting caspase-like (C-L), trypsin-like (T-L) and chymotrypsin-like (ChT-L) activities of proteasome. The antiproteasomal activity evaluations revealed that compounds preferentially inhibited the β5 subunit compared with β1 and β2 subunits of the proteasome. Among the compounds, compounds 7 and 9 showed the highest antiproliferative activity with an IC50 value of 7.10± 0.10 and 7.43 ± 0.25 μM, respectively. Additionally, compound 7 displayed comparable potency to PI-083 lead compound in terms of β5 antiproteasomal activity with an inhibition percentage of 34.67 at 10μM. This compound showed an IC50 value of 32.30 ± 0.45 μM against β5 subunit. Furthermore, molecular modeling studies of the most active compound 7 revealed key interactions with β5 subunit. The results suggest that this class of compounds may be beneficial for the development of new potent proteasome inhibitors.

Five-year survival in luminal breast cancer patients: relation with intratumoral activity of proteasomes.

The purpose of the study was to analyze the relationship between the caspase-like (CL) and chymotrypsin-like (ChTL) activities of proteasomes and the 5-year overall and metastasis-free survival rates in patients with luminal breast cancer. The study included 117 patients with primary operable invasive breast cancer (T1-2N0-1M0). Tissue samples from breast cancer patients were obtained as a result of the radical mastectomy or breast conserving surgery, which was a first line of therapy. The ChTL and CL proteasomes activities in the tumor tissue and in the surrounding adjacent breast tissues were assessed using the fluorometric method. The coefficients of ChTL (cChTL) and CL (cCL) proteasomes activities were also determined. The coefficients were calculated as the ratio of the corresponding proteasomes activity in the tumor tissue to the surrounding adjacent breast tissues. Within 5 years of follow-up, hematogenous metastases occurred in 14% of patients with luminal A breast cancer, in 31% of patients with luminal B human epidermal growth factor receptor-2 (HER-2) negative and in 23% of patients with luminal B HER-2 positive breast cancers. The study protocol was approved by the Local Ethics Committee of the Cancer Research Institute of Tomsk National Research Medical Center. Written informed consent was obtained from all patients. An increase in the ChTL and CL proteasomes activities was shown in all studied molecular subtypes of breast cancer compared to adjacent tissues. It was found that the cChTL of >35.9 U/mg protein and the cCL of >2.21 in breast cancer patients were associated with the development of distant metastases. In patients with luminal A breast cancer, the 5-year metastasis-free survival rates were associated only with the value of cCL of proteasomes (log-rank test: P=0.008). In patients with luminal B HER-2 negative breast cancer, the 5-year metastasis-free survival rates were associated with the levels of ChTL and cCL proteasomes activities (log-rank test: P=0.02 and P=0.04, respectively). The data obtained on the correlation of 5-year metastasis-free survival rates with the level of proteasomes activities indicate the possibility of their use as additional prognostic criteria for breast cancer.

Proteasome activator 28γ (PA28γ) allosterically activates trypsin-like proteolysis by binding to the α-ring of the 20S proteasome

Proteasome activator 28γ (PA28γ/REGγ) is a member of the 11S family of proteasomal regulators that is constitutively expressed in the nucleus and implicated in various diseases, including certain cancers and systemic lupus erythematosus. Despite years of investigation, how PA28γ functions to stimulate proteasomal protein degradation remains unclear. Alternative hypotheses have been proposed for the molecular mechanism of PA28γ, including the following: (1) substrate selection, (2) allosteric upregulation of the trypsin-like (T-L) site, (3) allosteric inhibition of the chymotrypsin-like (CT-L) and caspase-like (C-L) sites, (4) conversion of the CT-L or C-L sites to new T-L sites, and (5) gate opening alone or in combination with a previous hypothesis. Here, by mechanistically decoupling gating effects from active site effects, we unambiguously demonstrate that WT PA28γ allosterically activates the T-L site. We show PA28γ binding increases the Kcat/Km by 13-fold for T-L peptide substrates while having little-to-no effect on hydrolysis kinetics for CT-L or C-L substrates. Furthermore, mutagenesis and domain swaps of PA28γ reveal that it does not select for T-L peptide substrates through either the substrate entry pore or the distal intrinsically disordered region. We also show that a previously reported point mutation can functionally switch PA28γ from a T-L activating to a gate-opening activator in a mutually exclusive fashion. Finally, using cryogenic electron microscopy, we visualized the PA28γ-proteasome complex at 4.3 Å and confirmed its expected quaternary structure. The results of this study provide unambiguous evidence that PA28γ can function by binding the 20S proteasome to allosterically activate the T-L proteolytic site.

Comparison of Proteasome Inhibitors-Induced Cardiotoxicity (carfilzomib vs. bortezomib): Insights into the Molecular Mechanisms

Introduction: Proteasome inhibitors are widely used for the treatment of multiple myeloma (MM). Carfilzomib is an irreversible proteasome inhibitor, which has been licensed for the treatment of relapsed/refractory MM. In phase 3 trials, carfilzomib has been associated with higher heart failure and cardiotoxicity rates (grade ≥3: 4-6%) compared with the reversible inhibitor, bortezomib (grade ≥3: <2%). However, the mechanisms of heart damage by carfilzomib have not been fully identified yet. The aim of this study was to investigate the molecular mechanisms of carfilzomib-induced cardiotoxicity compared to bortezomib in vivo .Methods: Male C57BL/6 mice, 12 weeks old, were randomized into the following groups: 1. Control group (Ν/S 0.9%, n=7); 2. Bortezomib group (1mg/kg ip, n=9); 3. Carfilzomib group (8 mg/kg ip, n=8). Drugs were administered every 48 hours for 6 days. At baseline and at the end of treatment the mice underwent echocardiographic assessment. Animals were sacrificed and blood and myocardial tissue samples were obtained for the analysis of proteasome peptidases activity, signaling pathways and molecular mechanisms. Protein kinase Akt, along with its downstream NO synthases; endothelial (eNOS) and inducible (iNOS), were identified as targets of possible endothelial dysfunction and inflammation. Moreover, the transcription factor FOXO1, downstream target of Akt and AMPKα, was identified in order to investigate possible changes in the expression of apoptotic factors. Finally, AMPKα was identified since - besides phosphorylating eNOS and FOXO1 - it functions as a regulator of autophagy. Blood samples were used to measure levels of malondialdehyde (MDA), a marker for oxidative stress (lipid peroxidation).Results: Administration of bortezomib or carfilzomib resulted in significant reduction of the assayed chymotrypsin-like (CT-L) and caspase-like (C-L) proteasomal peptidase activities in the hearts of treated mice vs . controls. Echocardiography at day 6 demonstrated a statistically significant reduction in the fractional shortening (FS) in the carfilzomib group compared to the bortezomib and control groups (39.87±0.47% vs. 42.10±0.82% and 42.05±0.64 respectively, p <0.05). Western blot analysis in the carfilzomib group demonstrated a decrease in pAkt/tAkt (0.54 fold change of control, p<0.05), pAMPKα/tAMPKα (0.05 fold change of control, p<0.001) and peNOS/teNOS (0.41 fold change of control, p<0.05) levels and an increase in the expression of iNOS (5.16 fold change of control, p<0.01) compared to the control group. In contrast, no statistically significant differences were observed in the above mentioned signaling molecules between bortezomib and control. In the carfilzomib group a decrease in pAkt/tAkt (36.73% of bortezomib, p<0.001), pAMPKα/tAMPKα (4.07% of bortezomib, p<0.0001) and an increase in the expression of iNOS (607.06% of bortezomib, p<0.01) compared to the bortezomib group was observed. Levels of pFOXO1/tFOXO1 decreased in both carfilzomib and bortezomib groups versus the control group (0.24 and 0.26 fold change of control respectively, p<0.001). Interestingly, in the bortezomib group, reduction in body weight (median 20.10 mg; range 18.20 to 25.20 mg) versus control (median 24.80 mg; range 24.00 to 26.80 mg; p<0.01) and carfilzomib (median 23.60 mg; range 22.20 to 25.20 mg; p<0.05)) and increased levels of MDA in plasma (median 13.08 uM; range 8.09 to 17.21 uM), versus control (median 8.30 uM; range 5.30 to 10.86 uM; p<0.05) and carfilzomib (median 6.18 uM; range 4.89 to 7.79 uM; p<0.01), combined with a 43.75% increase in mortality (compared to zero mortality in carfilzomib and control groups), were observed.Conclusion: The present study demonstrates that carfilzomib induces cardiac dysfunction via interfering with the Akt/eNOS axis and via simultaneous increase of iNOS, leading to possible endothelial dysfunction and inflammation. Importantly the decrease of phosphorylation of AMPKα observed in the carfilzomib group seems to be an essential mechanism for carfilzomib induced FS reduction. Moreover, AMPKα and Akt inhibition results in decreased FOXO1 phosphorylation with possible induction of apoptosis and autophagy. On the contrary bortezomib seems to cause premature death in the mice through a different mechanism that requires further investigation. DisclosuresKastritis:Takeda: Honoraria; Amgen: Research Funding; Genesis: Honoraria; Janssen: Honoraria, Research Funding. Dimopoulos:Genesis Pharma: Research Funding; Amgen Inc, Celgene Corporation, Janssen Biotech Inc, Onyx Pharmaceuticals, an Amgen subsidiary, Takeda Oncology: Consultancy, Honoraria, Other: Advisory Committee: Amgen Inc, Celgene Corporation, Janssen Biotech Inc, Onyx Pharmaceuticals, an Amgen subsidiary, Takeda Oncology; Novartis: Consultancy, Honoraria. Terpos:Janssen: Honoraria, Research Funding; Takeda: Honoraria, Other: SC member; GSK: Honoraria; Genesis/Celgene: Honoraria, Other: DMC member, Research Funding; Amgen: Honoraria, Other: SC member, Research Funding; BMS: Honoraria; Abbvie: Honoraria.

Amniotic Fluid Proteasome and Immunoproteasome in the Setting of Intra-Amniotic Infection, Inflammation, and Preterm Birth.

Preterm birth is an important determinant of neonatal morbidity and mortality and intra-amniotic infection (IAI) and inflammation play a causative role. The constitutive proteasome and immunoproteasome are key players in maintenance of proteostasis and their alteration outside pregnancy has been linked to pathogenesis of numerous inflammatory diseases. Our goal was to evaluate the levels, activities, and potential origin of amniotic fluid (AF) proteasome in women with preterm birth induced by infection and/or inflammation. Total proteasome and immunoproteasome concentrations were measured in AF retrieved by trans-abdominal amniocentesis from 155 pregnant women. Proteasome activities were measured with fluorogenic substrates targeting caspase-like (CAS-L), trypsin-like (TRY-L), or chymotrypsin-like (CHE-L) lytic activities. We found that IAI significantly upregulated AF concentrations of total proteasome and of the immunoproteasome (P<0.001 for both) with no differences based on gestational age. Based on substrate preference and profile of pharmacologic inhibition, we identified the CHE-L activity of the immunoproteasome as the primary lytic activity upregulated in AF of pregnancies complicated by IAI. When compared with matched maternal blood and cord blood, proteasome activity was by far the highest in AF and this was further elevated in IAI. Western blot confirmed β5 (PSMB5) and β5i (PSMB8) subunits of the constitutive proteasome and immunoproteasome are present in AF and IHC staining of fetal membranes pointed to chorio-decidua as a potential source. In conclusion, IAI is associated with increased AF immunoproteasome activity that by analogy with other inflammatory diseases may generate antigenic oligopeptides and may play a role in triggering preterm birth.

42: Fetuses with fetal growth restriction (FGR) have elevated proteasome levels and activity

To increase lean body mass, the rate of fetal protein synthesis must exceed that of protein breakdown. The ubiquitin-proteasome system is an assembly of enzymatic activities with a key role in protein degradation and homeostasis. Environmental stressors switch the constitutive proteasome (cPROT) to immunoproteasome (iPROT), a quality control proteolytic machinery effective also in the absence of inflammation. Our hypothesis was that FGR fetuses have upregulated levels and enzymatic activity of the proteasome. We analyzed maternal blood, cord blood, and placenta of 70 singleton pregnancies of which 37 were complicated by FGR (EFW< 10%, Table). FGR occurred in the context of preeclampsia with severe features (sPE, n=23), identifiable causes (n=2: CMV infection, true cord knot) or idiopathic factors (n=12). Proteasome levels were measured using ELISA for cPROT and iPROT 20S subunit. Lytic activity was analyzed with fluorogenic substrates for caspase-like (CAS-L), chemotrypsin-like (CHE-L) and trypsin-like (TRY-L) activities. Specificity was confirmed with proteasome inhibitors MG132 and ONX. Placenta was stained for β5 (cPROT) and β5i (iPROT) subunits. Controls were idiopathic preterm births (iPTB) without fetal or placental inflammation. Data was adjusted for gestational age (GA) at birth. 1) The highest maternal cPROT levels were seen in sPE, independent of FGR (sPE p=.003, FGR p=.259, 2-way ANOVA, Fig A); 2) There was no correlation between cord blood and maternal proteasome levels (r=-.009, p=.96); 3) Fetuses with FGR had heightened CHE-L enzymatic activity independent of maternal proteasome levels or activity, sPE status or GA (adjusted p=.04, Fig B); 4) Cord blood proteasome activity of FGR fetuses was inhibited by MG132 and ONX with maximal effect on CHE-L activity which was reduced to 1.7% and 0.6%, respectively; 5) FGR placenta displayed intense β5i staining in trophoblasts and stromal cells suggestive of upregulated iPROT (Fig C). FGR fetuses display a significant upregulation in proteasome enzymatic activity independent of maternal compartment and etiology.View Large Image Figure ViewerDownload Hi-res image Download (PPT)

Type II-Metacaspases are involved in cell stress but not in cell death in the unicellular green alga Dunaliella tertiolecta.

Ultraviolet radiation (UVR; 280–400 nm) has a great impact on aquatic ecosystems by affecting ecophysiological and biogeochemical processes as a consequence of the global change scenario generated by anthropogenic activities. We studied the effect of PAR (P)+UVA (A)+UVB (B) i.e. PAB, on the molecular physiology of the unicellular green alga Dunaliella tertiolecta for six days. We assessed the relationship between the triggered UVR stress response and metacaspases and caspase-like (CL)activities, which are proteases denoted to participate in cell death (CD) in phytoplankton. UVR inhibited cell growth and in vivo chlorophyll a fluorescence but did not cause cell death. Western blot analyses reflected that Type-II metacaspases (MCs) are present and appear to be involved in UVR induced-cell stress but not in dark-induced CD in D. tertiolecta. Enzyme kinetics revealed that cleavage of the MCs-reporter substrates RVRR, QRR, GRR, LKR, HEK, and VLK was 10-fold higher than WEHD, DEVD, IETD, and LETD CLs-substrates. The lowest apparent Michaelis-Menten constants (KMap) corresponded to RVRRase (37.5 μM) indicating a high affinity by the RVRR substrate. The inhibition of enzymatic activities by using inhibitors with different target sites for hydrolyses demonstrated that from all of the R/ Kase activities only RVRRase was a potential candidate for being a metacaspase. In parallel, zymograms and peptide-mass fingerprinting analyses revealed the identities of such Rase activities suggesting an indirect evidence of possible natural physiological substrates of MCs. We present evidence of type II-MCs not being involved in CD in D. tertiolecta, but rather in survival strategies under the stressful irradiance conditions applied in this study.

Role of proteasome system in prognosis of breast cancer progression

The aim of this study was to compare the activity of proteasomes with different variants of tumor progression in luminal and triple-negative breast cancer (BC). Materials and methods. 132 patients with primary luminal and triple-negative breast cancer in stage Т 1-3 N0 2 M 0 who had not received neoadjuvant treatment were included in this study. Proteasome chymotrypsin-like (ChTL) and caspase-like (CL) activities were determined by hydrolysis of fluorogenic peptides Suc-LLVY-AMC and Z-LLGlu-AMC in samples of tumor and adjacent tissues. The coefficients of chymotrypsin-like (kChTL) and caspase-like (kCL) proteasome activity were also calculated as the ratio of the corresponding activity in the tumor tissue to activity in the adjacent tissue. Results: Results. The increased level of ChTL and CL proteasomal activity in the tumor were observed in comparison with adjacent tissues for all molecular subtypes of BC. The process of lymphogenic metastasis of luminal A and luminal B subtypes of breast cancer is associated with significant changes in the CL activity of the proteasome. Caspase-like activity of proteasomes was increased in luminal A breast cancer with extensive lymphogenic metastasis (N2), and on the other hand it was decreased in the luminal B subtype of cancer. For the hematogenic pathway of breast cancer progression the ratio of proteasomal activity in the tumor and adjacent tissues plays a significant role. The increase in proteasome activity in the tumor over the activity of proteasomes in adjacent tissues more than 2 times was associated with poor metastatic-free prognosis of the disease.

Milder degenerative effects of Carfilzomib vs. Bortezomib in the Drosophila model: a link to clinical adverse events

Proteasome inhibitors, e.g. Bortezomib (BTZ) and Carfilzomib (CFZ), have demonstrated clinical efficacy against haematological cancers. Interestingly, several adverse effects are less common, compared to BTZ, in patients treated with CFZ. As the molecular details of these observations remain not well understood we assayed the pathophysiological effects of CFZ vs. BTZ in the Drosophila experimental model. Mass Spectrometry analyses showed that neither CFZ nor BTZ are hydrolysed in flies’ tissues, while at doses inducing similar inhibition of the rate limiting for protein breakdown chymotrypsin-like (CT-L) proteasomal activity, CFZ treatment resulted in less intense increase of oxidative stress or activation of antioxidant and proteostatic modules. Also, despite comparable cardiotoxicity likely due to disrupted mitochondrial function, CFZ did not affect developmental processes, showed minimal neuromuscular defects and reduced to a lesser extent flies’ healthspan. Studies in flies, human cancer cell lines and blood cells isolated from Multiple Myeloma patients treated with CFZ or BTZ revealed, that the increased BTZ toxicity likely relates to partial co-inhibition of the caspase-like (C-L) proteasomal activity Supportively, co-treating flies with CFZ and a C-L selective proteasome inhibitor exacerbated CFZ-mediated toxicity. Our findings provide a reasonable explanation for the differential adverse effects of CFZ and BTZ in the clinic.

Abstract 3069: Investigation of pharmacodynamic and predictive biomarkers to define response to proteasome inhibitor marizomib in glioma

Abstract Proteasome inhibitors (PIs) have been employed with clinical success in multiple myeloma, but have been much less effective in solid tumors, despite the central role of the proteasome in controlling cellular metabolism. Marizomib (MRZ) is a novel second generation proteasome inhibitor which binds irreversibly to and inhibits the enzymatic activity of all three subunits of the proteasome. The unique ability of MRZ among PIs to cross the blood-brain barrier, combined with its pan-proteasome activity, suggest that MRZ may have distinct therapeutic advantages over the approved PIs in the treatment of glioma. Preclinical studies with MRZ have demonstrated anti-tumor activity in intracranial glioma studies, and MRZ is currently being evaluated in a Phase I clinical trial in WHO Grade IV recurrent glioma in combination with bevacizumab (NCT02330562). The aim of this study was to identify pharmacodynamic and predictive biomarkers of response to marizomib in glioma patients. Analysis of the pharmacodynamic profile of MRZ in packed whole blood from MRZ-treated glioma patients demonstrated &amp;gt;70% inhibition of the chymotrypsin-like (CT-L) activity as early as day 1 of cycle1 at 1 hr post-infusion, with 100% inhibition post-infusion in all patients by the end of cycle 1. Pre-infusion data demonstrate a prolonged effect, with &amp;gt;60% inhibition of CT-L persistent between day 15 of each cycle and day 1 of the next cycle. Trypsin-like (T-L) and caspase-like (C-L) activities increased after the first 1-2 MRZ doses, presumably due to compensatory hyperactivation of these subunits triggered by CT-L inhibition, which was subsequently overcome by repeated MRZ infusion, resulting in 40-60% inhibition of T-L and 10-30% inhibition of C-L evident through cycle 5. Analysis of proteasome enzymatic activity in archival glioma tumor tissue revealed that levels of all three proteasome activities are variable between high grade glioma samples, suggesting the potential for differential sensitivity to proteasome inhibition in glioma patients. Further, there is a linear correlation between CT-L activity (the rate limiting enzyme for proteasomal proteolysis) and C-L activity in these samples, suggesting that a PI such as MRZ with pan-proteasome specificity could potentially exhibit more activity in glioma compared to CT-L specific PIs. The data are currently being expanded to evaluate both proteasome enzymatic activity and subunit mRNA levels, to establish whether these endpoints might serve as a proteasome based biomarker. In conclusion, this study demonstrates that packed whole blood may be suitable as a pharmacodynamic biomarker for proteasome inhibition. This biomarker strategy may be crucial to stratify MRZ responsive patients in glioma. Citation Format: Daniela Bota, Annick Desjardins, Warren Mason, Kaijun Di, Ann P. MacLaren, Nancy Levin, Mohit Trikha. Investigation of pharmacodynamic and predictive biomarkers to define response to proteasome inhibitor marizomib in glioma. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 3069.

Marizomib Overcomes Compensatory Hyperactivation of Trypsin-like and Caspase-like Subunits to Provide Pan-Proteasome Subunit Inhibition in Patients with Multiple Myeloma and Solid Tumors

Background: Proteasome inhibitors (PIs) are a highly active drug class in multiple myeloma (MM), but development of resistance is commonly observed. Although all clinical-stage PIs are effective inhibitors of chymotrypsin-like (CT-L) proteasome subunit activity, a possible mechanism of resistance is compensatory hyperactivation of the caspase-like (C-L) and trypsin-like (T-L) subunits. Marizomib (MRZ) is a novel, irreversible, second-generation PI under development for the treatment of MM and malignant glioma. MRZ potently inhibits the 3 subunits of the 20S proteasome with a specificity and activity distinct from that of bortezomib and carfilzomib and their oral analogs ixazomib and oprozomib.Methods: In the clinical study NPI-0052-102, we evaluated the pharmacodynamic (PD) activity of MRZ against all three proteasome subunits in whole blood after single, or repeated administration, via two schedules in patients (pts) with previously treated advanced malignancies (solid tumors or hematologic). Pts received MRZ via Schedule A - weekly dosing for 3 doses in 4-week cycles by IV infusion over 1 to 10 min, or Schedule B - twice-weekly dosing for 4 doses in 3-week cycles by IV infusion over 10 min to 2 hr. Blood samples were collected on Days 1 and 15 (Schedule A) or 1 and 11 (Schedule B), pelleted by centrifugation and frozen within 48 hrs. Pellets were lysed and the activity of all 3 proteasomal subunits was assayed using specific fluorogenic substrates.Results: Partial or complete inhibition of all three proteasome subunits was achieved with both once-weekly and twice-weekly MRZ dosing. The rank order of sensitivity, CT-L > T-L > C-L, was as expected from the biochemical and cellular potencies of the drug. For CT-L activity, proteasome inhibition was dose dependent, with both the initial effect (on Cycle 1, Day 1 - C1D1) and the peak effect of proteasome inhibition increasing in a dose-dependent manner. CT-L inhibition was modest at the lowest dose levels (≤ 0.15 mg/m2), reaching moderate levels after repeat dosing. At intermediate dose levels of 0.3 to 0.55 mg/m2, CT-L inhibition was 31% to 75% on C1D1, rising to 70% to 93% after repeat dosing. At doses of 0.7 mg/m2 and above, inhibition of CT-L activity was usually complete within the first cycle. By contrast, C-L and T-L activities were unchanged or increased in the first cycle, suggesting compensatory hyperactivation in response to effective blockade of CT-L activity. Importantly, however, this response was overcome by repeat dosing with MRZ, and inhibition of T-L and C-L activity was noted across all dose levels. For C-L activity, treatment with MRZ at the recommended Phase 2 dose (RP2D) of 0.5 mg/m2 with twice-weekly dosing resulted in inhibition of up to 39% by Cycle 2 and was maintained, when tested, through Cycles 4 and 6. Treatment at the RP2D of 0.7 mg/m2 for once-weekly dosing resulted in C-L inhibition of 14% to 37% by the end of the first cycle, rising to 31% to 50% by the end of Cycle 2. Blockade of T-L activity was more robust after multiple cycles of MRZ therapy. Although inhibition of the T-L subunit was absent on C1D1 in patients receiving 0.5 to 0.55 mg/m2, inhibition of up to 80% was achieved by Cycle 2 and maintained for the duration of treatment. At the once-weekly RP2D of 0.7 mg/m2, T-L inhibition of 29% to 56% was achieved by the end of the first cycle, rising to 64% to 78% by the end of Cycle 2.Conclusions: The PD activity of MRZ against all three proteolytic subunits was assessed in patients with MM, solid tumors, and advanced lymphomas. At the twice-weekly and once-weekly RP2Ds, complete inhibition of CT-L activity was observed within 1-2 cycles of therapy, but accompanied by compensatory hyperactivation of the C-L and T-L subunits. This phenomenon in red cells suggests that it may be due to allosteric interactions within the catalytic core of the 20S proteasome rather than de novo synthesis of additional proteasomes. Ongoing MRZ therapy was able to overcome this adaptive response, resulting in robust pan-subunit proteasome inhibition within 2-6 cycles, most probably due to the cumulative effect of multiple exposures to MRZ. Due to their reversible binding mode (bortezomib, ixazomib) or monospecificity for the CT-L site (carfilzomib, oprozomib), other clinical PIs are predicted to lack this capability. This unique property of MRZ may explain in part its clinical activity in patients with MM resistant to both bortezomib and carfilzomib. DisclosuresOff Label Use: marizomib treatment for multiple myeloma and solid tumours.. Harrison:AbbVie: Research Funding; Janssen: Research Funding, Speakers Bureau; Celgene: Honoraria, Research Funding. Burrows:Triphase Accelerator Corporation: Consultancy. Reich:Triphase Accelerator Corporation: Consultancy. Trikha:Triphase Accelerator Corporation: Employment.

Inhibition of immunoproteasome reduces infarction volume and attenuates inflammatory reaction in a rat model of ischemic stroke.

The detailed knowledge about the contribution of immunoproteasome to the neuroinflammation in ischemic stroke is still not available. The immunoreactivity of low molecular mass peptide 2 (LMP2) and low molecular mass peptide 7 (LMP7) was evident in the ipsilateral ischemic cerebral cortex and striatum following transient middle cerebral artery occlusion (MCAO). Both LMP2 and LMP7 increased as early as 4 h after the MCAO, further increased at 24 h, peaked at 72 h and decreased 7 days later. LMP2 and LMP7 were mainly present in astrocytes and microglia/macrophage cells, respectively. LMP2 knockdown by shRNA (short hairpin RNA) markedly reduced the levels of LMP2 and LMP7 protein and caused 75.5 and 78.6% decrease in the caspase-like (C-L) and chymotrypsin-like (CT-L) activities, respectively. Compared with cont-shRNA group (39.7%, infarction volumes/total ipsilateral hemisphere), the infarction volumes were reduced to 22.5% in LMP2-shRNA group. Additionally, LMP2 knockdown significantly reduced activated astrocytes and microglia, the expression nuclear factor kappa B (NF-κB) p65, tumor necrosis factor-α (TNF-α) and interleukin-1β (IL-1β) and caused less accumulation of ischemia-induced protein ubiquitination compared with MG132. These findings demonstrate that inhibition of LMP2 significantly attenuates inflammatory reaction and offers neuroprotection against focal cerebral ischemia in rats, suggesting that selective immunoproteasome inhibitors may be a promising strategy for stroke treatment.

Identification of a new series of amides as non-covalent proteasome inhibitors

Proteasome inhibition has emerged as an important therapeutic strategy for the treatment of multiple myeloma (MM) and some forms of lymphoma, with potential application in other types of cancers. 20S proteasome consists of three different catalytic activities known as chymotrypsin-like (ChT-L), trypsin-like (T-L), and, post-glutamyl peptide hydrolyzing (PGPH) or caspase-like (C-L), which are located respectively on the β5, β2, and β1 subunits of each heptameric β rings. Currently a wide number of covalent proteasome inhibitors are reported in literature; however, the less widely investigated non-covalent inhibitors might be a promising alternative to employ in therapy, because of the lack of all drawbacks and side-effects related to irreversible inhibition. In the present work we identified a series of amides, two of which (1b and 1f) are good candidates to non-covalent inhibition of the chymotrypsin-like activity of the β5 proteasome subunit. The non-covalent binding mode was corroborated by docking simulations of the most active inhibitors 1b, 1f and 2h into the yeast 20S proteasome crystal structure.

Enzymatic Activities Of Circulating Plasma Proteasomes (cProt) In Newly Diagnosed Multiple Myeloma (NDMM) Patients Undergoing Treatment With Carfilzomib, Lenalidomide and Dexamethasone (CRd)

BackgroundThe proteasome inhibitor carfilzomib is highly effective in the treatment of multiple myeloma (MM). It selectively and irreversibly binds the chymotrypsin-like (CHYM) active site in the β5 subunit of the proteasome. One prior retrospective study based on 50 NDMM patients found maintained elevated total cProt levels post therapy to be associated with poorer response to therapy and shorter overall survival (PMID: 17095627). We conducted a study based on NDMM patients treated with carfilzomib, lenalidomide and dexamethasone (CRd). The aim of this investigation was to assess the role of specific enzymatic activities of plasma cProt in relation to treatment responses. MethodsWe assessed 37 newly diagnosed MM patients from our ongoing clinical trial using CRd therapy (NCT01402284). Baseline demographic, clinical and laboratory parameters were collected. Plasma samples were collected at time intervals as specified in the protocol [C1D1 (baseline), C1D2 (post single dose carfilzomib), C2D1, C4D1 and C8D1] and frozen to -80ºC. Patient responses were assessed per current IMWG guidelines. CHYM, caspase-like (CASP), and trypsin-like (TRYP) activities from cProt were assayed by continuously monitoring the production of 7-amino-4-methylcoumarin (AMC) from fluorogenic peptides in plasma. Briefly, plasma samples were activated with SDS (for chymotrypsin-like and caspase-like) or 10% Tween-20 (for trypsin-like). The reaction wells contained 30 μL assay buffer (25 mmol/L HEPES), 10 μL activated sample, and 10 μL of the prospective fluorogenic peptide-AMC substrate. To measure the fluorescence release of free AMC with time, the SpectraMax M5 (Molecular Devices) instrument was used with a read interval of 1 min during 30 min at 37ºC. Samples were analyzed per triplicate. Enzymatic activities were quantified (pmol AMC/s/mL plasma) by generating a standard curve of AMC. A two tailed Wilcoxon signed rank test was used for comparisons across matched cProt values. The Mann Whitney Test was used to compare differences between two independent groups of cProt values. Spearman's rank correlation was used for correlation between cProt levels and clinical parameters. All p-values are two-tailed. ResultsPatients had a median age of 61 years (range 40-86; 57% males). Median M-spike was 2.7 (0.8-7.1) g/dL, isotypes included IgG (n=26), IgA (n=6), kappa (n=4) and lambda (n=1); International Staging System (ISS) Stage I (n=19) and II (n=18). Median C1D1 levels of chymotrypsin-like, caspase-like and trypsin-like activity for all patients were 0.84 (0.12-3.89), 0.85 (0.31-2.28) and 2.95 (1.4-7.39) pmol AMC/s/ml plasma, respectively. CHYM and CASP C1D1 levels correlated with the levels of baseline IgG (r=0.42, CHYM; r=0.38 CASP) and the levels of baseline β2-microglobulin (r=0.37, CHYM; r=0.45, CASP). Additionally, CHYM correlated with levels of free kappa (r=0.33) and levels of serum M-protein (r=0.34); and CASP correlated with the percentage of plasma cell infiltration in core bone marrow biopsy (r=0.36). Baseline TRYP levels did not correlate with clinical parameters. Median CHYM (1.3 versus 0.7 pmol AMC/s/ml plasma) and CASP (1.0 versus 0.7 pmol AMC/s/ml plasma) levels, but not TRYP levels, were were non-significantly elevated in Stage II ISS compared to Stage I patients. CHYM levels after an initial single dose of carfilzomib were reduced by a median of 68.2% (p<0.05), whereas CASP and TRYP levels were increased by 5.3% (p>0.05) and 0.4% (p>0.05), respectively. CASP and TRYP levels measured at C2D1, C4D1 and C8D1 remained stable throughout treatment cycles. When compared to baseline, median CHYM levels decreased significantly at C1D2 (after one dose of carfilzomib), then increased at C2D1 and steadily decreased again throughout treatment at the C4D1 and C8D1 time intervals. ConclusionsIn newly diagnosed MM patients, pre-treatment CHYM and CASP plasma activity levels were non-significantly higher among patients with higher ISS stage. Peripheral blood collected 24 hours after a single dose carfilzomib showed reduced CHYM levels by >60% in most patients. Fluctuations in CHYM, CASP and TRYP levels were noted throughout CRd treatment; no consistent patterns were observed in relation to response to therapy. Disclosures:No relevant conflicts of interest to declare.

A Small Molecule Inhibitor of Ubiquitin-Specific Protease-7 Induces Apoptosis in Multiple Myeloma Cells and Overcomes Bortezomib Resistance

Bortezomib therapy has proven successful for the treatment of relapsed/refractory, relapsed, and newly diagnosed multiple myeloma (MM); however, dose-limiting toxicities and the development of resistance limit its long-term utility. Here, we show that P5091 is an inhibitor of deubiquitylating enzyme USP7, which induces apoptosis in MM cells resistant to conventional and bortezomib therapies. Biochemical and genetic studies show that blockade of HDM2 and p21 abrogates P5091-induced cytotoxicity. In animal tumor model studies, P5091 is well tolerated, inhibits tumor growth, and prolongs survival. Combining P5091 with lenalidomide, HDAC inhibitor SAHA, or dexamethasone triggers synergistic anti-MM activity. Our preclinical study therefore supports clinical evaluation of USP7 inhibitor, alone or in combination, as a potential MM therapy.

Activity Enhancement of the Synthetic Syrbactin Proteasome Inhibitor Hybrid and Biological Evaluation in Tumor Cells

Syrbactins belong to a recently emergent class of bacterial natural product inhibitors that irreversibly inhibit the proteasome of eukaryotes by a novel mechanism. The total syntheses of the syrbactin molecules syringolin A, syringolin B, and glidobactin A have been achieved, which allowed the preparation of syrbactin-inspired derivatives, such as the syringolin A-glidobactin A hybrid molecule (SylA-GlbA). To determine the potency of SylA-GlbA, we employed both in vitro and cell culture-based proteasome assays that measure the subcatalytic chymotrypsin-like (CT-L), trypsin-like (T-L), and caspase-like (C-L) activities. We further studied the inhibitory effects of SylA-GlbA on tumor cell growth using a panel of multiple myeloma, neuroblastoma, and ovarian cancer cell lines and showed that SylA-GlbA strongly blocks the activity of NF-κB. To gain more insights into the structure-activity relationship, we cocrystallized SylA-GlbA in complex with the proteasome and determined the X-ray structure. The electron density map displays covalent binding of the Thr1O(γ) atoms of all active sites to the macrolactam ring of the ligand via ether bond formation, thus providing insights into the structure-activity relationship for the improved affinity of SylA-GlbA for the CT-L activity compared to those of the natural compounds SylA and GlbA. Our study revealed that the novel synthetic syrbactin compound represents one of the most potent proteasome inhibitors analyzed to date and therefore exhibits promising properties for improved drug development as an anticancer therapeutic.

C-terminal trans,trans-muconic acid ethyl ester partial retro-inverso pseudopeptides as proteasome inhibitors

The development of specific inhibitors of the proteasome represents an important opportunity for new drug therapies. The central role of the multicatalytic complex in the intracellular proteolysis mediated by ubiquitin-proteasome pathway goes to discovery many molecules able to selectively inhibits enzymatic active subsites. Now, we report synthesis and activity of a new partial retro-inverso oligopseudopeptide derivatives bearing a trans,trans-muconic acid ethyl ester pharmacophoric unit at the C-terminal. Some analogues selectively inhibited in µM range the caspase-like (C-L) activity in the β1 subunit of the proteasome.

Syringolin B-inspired proteasome inhibitor analogue TIR-203 exhibits enhanced biological activity in multiple myeloma and neuroblastoma

Context: The bacterium Pseudomonas syringae pv. syringae (Pss) is a pathogen of many plant species and causes, for example, brown spot disease in bean plants (Phaseolus vulgaris). Pss excretes the syringolins, natural product molecules that act as a virulence factors and inhibit the proteasome of the host plants.Objective: Proteasome inhibitors belong to an important class of anticancer agents and bortezomib (Velcade®) has been Food and Drug Administration-approved for the treatment of multiple myeloma (MM) and mantle cell lymphoma. Syringolins represent a new class of proteasome inhibitors and the present work was undertaken to design a potent syringolin-inspired analogue (TIR-203) for anticancer drug development.Materials and methods: TIR-203 was tested against human MM and neuroblastoma (NB) cells. Cancer cells were treated with TIR-203 at various concentrations (0–10 µM) and the cell viability was measured using the MTS assay. To determine the effects on proteasomal activities, the cell culture-based proteasome inhibition assay was used. Syringolin A (SylA) and bortezomib were included as controls.Results: TIR-203 inhibited the cell proliferation of MM and NB cells in a dose-dependent manner at significantly lower concentrations than SylA. In MM cells, TIR-203 effectively inhibited the chymotrypsin-like (CT-L), caspase-like (C-L), and trypsin-like (T-L) activities of the proteasome. In NB cells, TIR-203 inhibited the CT-L and C-L activities, but not the T-L activity.Discussion and conclusions: The newly designed proteasome inhibitor TIR-203 is more potent than the natural product SylA and strongly inhibits the cell viability and proteasomal activity of MM and NB cells.