Carfilzomib Triggers Cell Death in Chronic Lymphocytic Leukemia by Inducing Proapoptotic and Endoplasmic Reticulum Stress Responses

Small molecules for impairing endoplasmic reticulum in cancer

The endoplasmic reticulum plays an important role in maintaining the protein homeostasis of cells as well as regulating Ca2+ storage. An increased load of unfolded proteins in the endoplasmic reticulum due to alterations in the cell's metabolic pathway leads to the activation of the unfolded protein response, also known as ER stress. ER stress plays a major role in maintaining the growth and survival of various cancer cells, but persistent ER stress can also lead to cell death and hence can be a therapeutic pathway in the treatment of cancer. In this review, we focus on different types of small molecules that impair different ER stress sensors, the protein degradation machinery, and chaperone proteins. We also review the metal complexes and other miscellaneous compounds inducing ER stress through multiple mechanisms. Finally, we discuss the challenges in this emerging area of research and the potential direction of research to overcome them towards next-generation ER-targeted cancer therapy.

Preclinical efficacy of carfilzomib in BRAF-mutant colorectal cancer models

Serine/threonine-protein kinase B-raf (BRAF) mutations are found in 8-15% of colorectal cancer patients and identify a subset of tumors with poor outcome in the metastatic setting. We have previously reported that BRAF-mutant human cells display a high rate of protein production, causing proteotoxic stress, and are selectively sensitive to the proteasome inhibitors bortezomib and carfilzomib. In this work, we tested whether carfilzomib could restrain the growth of BRAF-mutant colorectal tumors not only by targeting cancer cells directly, but also by promoting an immune-mediated antitumor response. In human and mouse colorectal cancer cells, carfilzomib triggered robust endoplasmic reticulum stress and autophagy, followed by the emission of immunogenic-damage-associated molecules. Intravenous administration of carfilzomib delayed the growth of BRAF-mutant murine tumors and mobilized the danger-signal proteins calreticulin and high mobility group box 1 (HMGB1). Analyses of drug-treated samples revealed increased intratumor recruitment of activated cytotoxic T cells and natural killers, concomitant with the downregulation of forkhead box protein P3 (Foxp3)+ T-cell surface glycoprotein CD4 (CD4)+ T cells, indicating that carfilzomib promotes reshaping of the immune microenvironment of BRAF-mutant murine colorectal tumors. These results will inform the design of clinical trials in BRAF-mutant colorectal cancer patients.

Size optimization of carfilzomib nanocrystals for systemic delivery to solid tumors

Carfilzomib (CFZ) is a second-generation proteasome inhibitor effective in blood cancer therapy. However, CFZ has shown limited efficacy in solid tumor therapy due to the short half-life and poor tumor distribution. Albumin-coated nanocrystal (NC) formulation was shown to improve the circulation stability of CFZ, but its antitumor efficacy remained suboptimal. We hypothesize that NC size reduction is critical to the formulation safety and efficacy as the small size would decrease the distribution in the reticuloendothelial system (RES) and selectively increase the uptake by tumor cells. We controlled the size of CFZ-NCs by varying the production parameters in the crystallization-in-medium method and compared the size-reduced CFZ-NCs (z-average of 168 nm, NC₁₆₈) with a larger counterpart (z-average of 325 nm, NC₃₂₅) as well as the commercial CFZ formulation (CFZ-CD). Both CFZ-NCs showed similar or higher cytotoxicity than CFZ-CD against breast cancer cells. NC₁₆₈ showed greater uptake by cancer cells, less uptake by macrophages and lower immune cell toxicity than NC₃₂₅ or CFZ-CD. NC₁₆₈, but not NC₃₂₅, showed a similar safety profile to CFZ-CD in vivo. The biodistribution and antitumor efficacy of CFZ-NCs in mice were also size-dependent. NC₁₆₈ showed greater antitumor efficacy and tumor accumulation but lower RES accumulation than NC₃₂₅ in 4T1 breast cancer model. These results support that NC formulation with an optimal particle size can improve the therapeutic efficacy of CFZ in solid tumors.

Immunoproteasome Activity in Chronic Lymphocytic Leukemia as a Target of the Immunoproteasome-Selective Inhibitors

Targeting proteasome with proteasome inhibitors (PIs) is an approved treatment strategy in multiple myeloma that has also been explored pre-clinically and clinically in other hematological malignancies. The approved PIs target both the constitutive and the immunoproteasome, the latter being present predominantly in cells of lymphoid origin. Therapeutic targeting of the immunoproteasome in cells with sole immunoproteasome activity may be selectively cytotoxic in malignant cells, while sparing the non-lymphoid tissues from the on-target PIs toxicity. Using activity-based probes to assess the proteasome activity profile and correlating it with the cytotoxicity assays, we identified B-cell chronic lymphocytic leukemia (B-CLL) to express predominantly immunoproteasome activity, which is associated with high sensitivity to approved proteasome inhibitors and, more importantly, to the immunoproteasome selective inhibitors LU005i and LU035i, targeting all immunoproteasome active subunits or only the immunoproteasome β5i, respectively. At the same time, LU102, a proteasome β2 inhibitor, sensitized B-CLL or immunoproteasome inhibitor-inherently resistant primary cells of acute myeloid leukemia, B-cell acute lymphoblastic leukemia, multiple myeloma and plasma cell leukemia to low doses of LU035i. The immunoproteasome thus represents a novel therapeutic target, which warrants further testing with clinical stage immunoproteasome inhibitors in monotherapy or in combinations.

Recent Research Progress of Chiral Small Molecular Antitumor-Targeted Drugs Approved by the FDA From 2011 to 2019

Chiral drugs usually contain chiral centers, which are present as single enantiomers or racemates. Compared with achiral drugs, they have significant advantages in safety and efficacy with high stereoselectivity. Of these drugs, chirality not only exerts influence on the solubility and pharmacokinetic characteristics but also has specific mechanistic characteristics on their targets. We noted that small molecules with unique chiral properties have emerged as novel components of antitumor drugs approved by the FDA in decade. Since approved, these drugs have been continuously explored for new indications, new mechanisms, and novel combinations. In this mini review, recent research progress of twenty-two FDA-approved chiral small molecular-targeted antitumor drugs from 2011 to 2019 is summarized with highlighting the potential and advantages of their applications. We believe that these updated achievements may provide theoretical foundation and stimulate research interests for optimizing drug efficacy, expanding clinical application, overcoming drug resistance, and advancing safety in future clinical administrations of these chiral targeted drugs.

Combinations of proteasome inhibitors with obatoclax are effective for small cell lung cancer

Proteasome inhibitors, bortezomib (BTZ), and carfilzomib (CFZ) are approved drugs for hematological malignancies, but lack anticancer activities against most solid tumors. Small cell lung cancer (SCLC) is a very aggressive neuroendocrine carcinoma of the lungs demanding effective therapy. In this study we investigated whether BTZ or CFZ combined with obatoclax (OBX), an antagonist for MCL-1 and a pan-BCL family inhibitor, could cause synergistic growth inhibition of SCLC cells. We showed that combined application of BTZ or CFZ with OBX caused synergistic growth inhibition of human SCLC cell lines (H82, H526, DMS79, H196, H1963, and H69) than single agent alone. Both BTZ-OBX and CFZ-OBX combinations displayed marked synergism on inducing apoptosis (~50% increase vs BTZ or CFZ alone). A comprehensive proteomics analysis revealed that BTZ preferentially induced the expression of MCL-1, an antiapoptotic protein, in SCLC cells. Thus, proteasome inhibitor-OBX combinations could specifically induce massive growth inhibition and apoptosis in SCLC cells. Subsequent proteome-wide profiling analysis of activated transcription factors suggested that BTZ- or CFZ-induced MCL-1 upregulation was transcriptionally driven by FOXM1. In nude mice bearing in SCLC H82 xenografts, both BTZ-OBX, and CFZ-OBX combinations exhibited remarkable antitumor activities against SCLC tumors evidenced by significant reduction of tumor size and the proliferation marker Ki-67 signals in tumor tissues as compared with single agent alone. Thus, proteasome inhibitor-OBX combinations are worth immediate assessments for SCLC in clinical settings.

Carfilzomib Promotes the Unfolded Protein Response and Apoptosis in Cetuximab-Resistant Colorectal Cancer

Cetuximab is a common treatment option for patients with wild-type K-Ras colorectal carcinoma. However, patients often display intrinsic resistance or acquire resistance to cetuximab following treatment. Here we generate two human CRC cells with acquired resistance to cetuximab that are derived from cetuximab-sensitive parental cell lines. These cetuximab-resistant cells display greater in vitro proliferation, colony formation and migration, and in vivo tumour growth compared with their parental counterparts. To evaluate potential alternative therapeutics to cetuximab-acquired-resistant cells, we tested the efficacy of 38 current FDA-approved agents against our cetuximab-acquired-resistant clones. We identified carfilzomib, a selective proteosome inhibitor to be most effective against our cell lines. Carfilzomib displayed potent antiproliferative effects, induced the unfolded protein response as determined by enhanced CHOP expression and ATF6 activity, and enhanced apoptosis as determined by enhanced caspase-3/7 activity. Overall, our results indicate a potentially novel indication for carfilzomib: that of a potential alternative agent to treat cetuximab-resistant colorectal cancer.

Cytotoxicity and Target Modulation in Pediatric Solid Tumors by the Proteasome Inhibitor Carfilzomib

BACKGROUND

Most children with recurrent metastatic solid tumors have high mortality rates. Recent studies have shown that proteasome inhibition leads to effective tumor killing in cells that have acquired treatment resistance and metastatic properties.

OBJECTIVE

The purpose of this study was to test the potential of Carfilzomib (CFZ), a proteasome inhibitor, in refractory pediatric solid tumors, which is currently unknown.

METHODS

A panel of pediatric solid tumor cell lines, including neuroblastoma, Ewing's sarcoma, osteosarcoma, rhabdomyosarcoma, and atypical teratoid rhabdoid tumor (ATRT), was used to evaluate the cytotoxic and proteasomal inhibitory effects of CFZ. A drug scheduling experiment was performed to determine the optimal dose and time to obtain effective cell killing. Combination studies of CFZ with chemotherapeutic drugs of different classes were performed to determine the extent of synergy.

RESULTS

CFZ showed effective cytotoxicity against all cell lines tested (mean IC50 = 7nM, range = 1-20nM) and activity in a fluorophore-tagged cell-based proteasome assay. Drug scheduling experiments showed that the minimum exposure of 4-8 hours/day is needed for effective cumulative killing. CFZ, when combined with chemotherapeutic drugs of different classes, synergistically enhanced the extent of cell death.

CONCLUSIONS

CFZ showed cytotoxic activity against all the solid pediatric cancer cell lines tested. This study provides initial in vitro data on the potential of CFZ to treat pediatric solid tumors and supports further investigations into the components of drug scheduling, biological correlates, and drug combinations for future early phase clinical trials in children.

Inhibition of ERAD synergizes with FTS to eradicate pancreatic cancer cells

Background

Pancreatic ductal adenocarcinoma (PDAC), one of the most lethal cancers, is driven by oncogenic KRAS mutations. Farnesyl thiosalicylic acid (FTS), also known as salirasib, is a RAS inhibitor that selectively dislodges active RAS proteins from cell membrane, inhibiting downstream signaling. FTS has demonstrated limited therapeutic efficacy in PDAC patients despite being well tolerated.

Methods

To improve the efficacy of FTS in PDAC, we performed a genome-wide CRISPR synthetic lethality screen to identify genetic targets that synergize with FTS treatment. Among the top candidates, multiple genes in the endoplasmic reticulum-associated protein degradation (ERAD) pathway were identified. The role of ERAD inhibition in enhancing the therapeutic efficacy of FTS was further investigated in pancreatic cancer cells using pharmaceutical and genetic approaches.

Results

In murine and human PDAC cells, FTS induced unfolded protein response (UPR), which was further augmented upon treatment with a chemical inhibitor of ERAD, Eeyarestatin I (EerI). Combined treatment with FTS and EerI significantly upregulated the expression of UPR marker genes and induced apoptosis in pancreatic cancer cells. Furthermore, CRISPR-based genetic ablation of the key ERAD components, HRD1 and SEL1L, sensitized PDAC cells to FTS treatment.

Conclusion

Our study reveals a critical role for ERAD in therapeutic response of FTS and points to the modulation of UPR as a novel approach to improve the efficacy of FTS in PDAC treatment.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12885-021-07967-6.

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

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.

ER Stress and Unfolded Protein Response in Leukemia: Friend, Foe, or Both?

The unfolded protein response (UPR) is an evolutionarily conserved adaptive signaling pathway triggered by a stress of the endoplasmic reticulum (ER) lumen compartment, which is initiated by the accumulation of unfolded proteins. This response, mediated by three sensors-Inositol Requiring Enzyme 1 (IRE1), Activating Transcription Factor 6 (ATF6), and Protein Kinase RNA-Like Endoplasmic Reticulum Kinase (PERK)—allows restoring protein homeostasis and maintaining cell survival. UPR represents a major cytoprotective signaling network for cancer cells, which frequently experience disturbed proteostasis owing to their rapid proliferation in an usually unfavorable microenvironment. Increased basal UPR also participates in the resistance of tumor cells against chemotherapy. UPR activation also occurs during hematopoiesis, and growing evidence supports the critical cytoprotective role played by ER stress in the emergence and proliferation of leukemic cells. In case of severe or prolonged stress, pro-survival UPR may however evolve into a cell death program called terminal UPR. Interestingly, a large number of studies have revealed that the induction of proapoptotic UPR can also strongly contribute to the sensitization of leukemic cells to chemotherapy. Here, we review the current knowledge on the consequences of the deregulation of UPR signaling in leukemias and their implications for the treatment of these diseases.

Suppression of proteasome induces apoptosis in APL cells and increases chemo-sensitivity to arsenic trioxide: Proposing a perception in APL treatment

In the last three decades, the pathogenesis of acute promyelocytic leukemia (APL) has been mostly studied with regard to the oncogenic role of PML/RAR fusion protein; however, the latest discoveries have stated that the concerns with the treatment of APL patients would not be resolved until the role of aberrant networks is overlooked. The present study was designed to evaluate the anti-cancer property of second-generation of the proteasome inhibitors carfilzomib (CFZ) on APL-derived NB4 cells. Our results showed that pharmacologic targeting of proteasome in NB4 reduced the proliferative rate of malignant cells through a c-Myc-mediated G2/M cell cycle arrest. Moreover, we found that the suppression of proteasome was coupled with the induction of apoptotic NB4 cell death, which is probably mediated through down-regulation of anti-apoptotic target genes. Interestingly, our results suggested that the suppression of the autophagy system using chloroquine could serve as a mechanism through which the cytotoxicity of CFZ in APL cells was ameliorated. Finally, and consistent with the favorable efficacy of single agent of CFZ, we also noted an intensifying effect of the inhibitor on the anti-leukemic activity of arsenic trioxide (ATO) when it was used in combination. Overall, this study suggests that pharmaceutical targeting of proteasome using CFZ, either as a single agent or in combination with ATO, could be a promising mechanism through which the obstacle on the way of APL would be tackled; however, further investigations are needed to determine the advantages of the inhibitor in clinical applications.

Saga of Mcl-1: regulation from transcription to degradation

The members of the Bcl-2 family are the central regulators of various cell death modalities. Some of these proteins contribute to apoptosis, while others counteract this type of programmed cell death, thus balancing cell demise and survival. A disruption of this balance leads to the development of various diseases, including cancer. Therefore, understanding the mechanisms that underlie the regulation of proteins of the Bcl-2 family is of great importance for biomedical research. Among the members of the Bcl-2 family, antiapoptotic protein Mcl-1 is characterized by a short half-life, which renders this protein highly sensitive to changes in its synthesis or degradation. Hence, the regulation of Mcl-1 is of particular scientific interest, and the study of Mcl-1 modulators could aid in the understanding of the mechanisms of disease development and the ways of their treatment. Here, we summarize the present knowledge regarding the regulation of Mcl-1, from transcription to degradation, focusing on aspects that have not yet been described in detail.

Sustained Delivery of Carfilzomib by Tannic Acid-Based Nanocapsules Helps Develop Antitumor Immunity

A group of chemotherapeutic drugs has gained increasing interest in cancer immunotherapy due to the potential to induce immunogenic cell death (ICD). A critical challenge in using the ICD inducers in cancer immunotherapy is the immunotoxicity accompanying their antiproliferative effects. To alleviate this, a nanocapsule formulation of carfilzomib (CFZ), an ICD-inducing proteasome inhibitor, was developed using interfacial supramolecular assembly of tannic acid (TA) and iron, supplemented with albumin coating. The albumin-coated CFZ nanocapsules (CFZ-pTA-alb) attenuated CFZ release, reducing toxicity to immune cells. Moreover, due to the adhesive nature of the TA assembly, CFZ-pTA-alb served as a reservoir of damage-associated molecular patterns released from dying tumor cells to activate dendritic cells. Upon intratumoral administration, CFZ-pTA-alb prolonged tumor retention of CFZ and showed consistently greater antitumor effects than cyclodextrin-solubilized CFZ (CFZ-CD) in B16F10 and CT26 tumor models. Unlike CFZ-CD, the locally injected CFZ-pTA-alb protected or enhanced CD8+ T cell population in tumors, helped develop splenocytes with tumor-specific interferon-γ response, and delayed tumor development on the contralateral side in immunocompetent mice (but not in athymic nude mice), supporting that CFZ-pTA-alb contributed to activating antitumor immunity. This study demonstrates that sustained delivery of ICD inducers by TA-based nanocapsules is an effective way of translating local ICD induction to systemic antitumor immunity.

The small molecule WNT/β-catenin inhibitor CWP232291 blocks the growth of castration-resistant prostate cancer by activating the endoplasmic reticulum stress pathway

BACKGROUND

Androgen receptor (AR)-targeted treatments improve the survival of castration-resistant prostate cancer (CRPC) patients; however, secondary resistance to these agents ultimately occurs in virtually all patients. Therefore, alternative therapeutic targets are urgently needed. Since growing evidence demonstrates that WNT/β-catenin signaling plays an important role in CRPC, the antitumor activity and mechanism of action of CWP232291, a small molecule β-catenin inhibitor, were investigated in prostate cancer.

METHODS

We assessed the antitumor activity of CWP232291 in prostate cancer cell lines and primary cells derived from CRPC patients. The effect of CWP232291 on apoptotic cell death, endoplasmic reticulum (ER) stress, cell viability, and WNT/β-catenin signaling was evaluated by flow cytometry, western blotting, luciferase reporter assay, and fluorescence microscopy. Antitumor efficacy was assessed in two CRPC xenograft mouse models.

RESULTS

CWP232291 induced ER stress, resulting in upregulation of the proapoptotic protein CHOP and activation of caspase-3-dependent apoptosis. In addition, CWP232291 suppressed the expression of β-catenin by affecting WNT-dependent transcriptional activity, and downregulated AR and its splice variants in prostate cancer cells. Antitumor activity was observed in prostate cancer cells in vitro and ex vivo, and antitumor efficacy was observed in vivo.

CONCLUSIONS

Beyond providing preclinical evidence of therapeutic efficacy for the novel small molecule β-catenin inhibitor CWP232291 in CRPC, our results show that inducing ER stress and targeting WNT/β-catenin signaling may be a novel strategy against CRPC.

Carfilzomib enhances cisplatin-induced apoptosis in SK-N-BE(2)-M17 human neuroblastoma cells

Neuroblastoma is a solid malignant tumor of the sympathetic nervous system, which accounts for 8–10% of childhood cancers. Considering the overall high risk and poor prognosis associated with neuroblastoma, effective therapeutics should be developed to improve patient survival and quality of life. A recent study showed that a proteasome inhibitor, carfilzomib (CFZ), reduced cell viability of SK-N-BE(2)-M17 neuroblastoma cells. Therefore, we investigated the molecular mechanisms by which CFZ lower the cell viability of neuroblastoma cells. CFZ reduced cell viability via cell cycle arrest at G2/M and apoptosis, which involved caspase activation (caspases-8, 9, 4, and 3), endoplasmic reticulum stress, reactive oxygen species production, mitochondrial membrane potential loss, and autophagy in a dose- and time-dependent manner. The effect of CFZ was additive to that of cisplatin (Cis), a well-known chemotherapeutic drug, in terms of cell viability reduction, cell cycle arrest, and apoptosis. Importantly, the additive effect of CFZ was maintained in Cis-resistant neuroblastoma cells. These results suggest that CFZ can be used in combination therapy for patients with neuroblastoma to overcome the resistance and adverse side effects of Cis.

Efficacy of celastrol combined with cisplatin in enhancing the apoptosis of U-2OS osteosarcoma cells via the mitochondrial and endoplasmic reticulum pathways of apoptosis

Osteosarcoma is a common primary malignant tumor of bone, and the poor prognosis and low 5-year survival rate have not improved for three decades. The present study aimed to study the effect a combination of celastrol and cisplatin on the human osteosarcoma cell line U-2OS, and to investigate the mechanism by which celastrol/cisplatin induces the apoptosis of osteosarcoma cells. MTT and Annexin V-FITC/PI assays were used to evaluate the effects of combined celastrol/cisplatin on growth and apoptosis, respectively, in U-2OS cells. Morphological changes accompanying cell growth inhibition were observed using a fluorescence microscope. Combination index (CI) analysis was used to evaluate the combinatorial effects of celastrol/cisplatin treatment. Western blotting was used to quantify the expression of apoptosis-associated proteins. It was identified that celastrol/cisplatin inhibited the growth of U-2OS cells in a dose-dependent manner. CI analysis revealed that combined celastrol/cisplatin demonstrated a synergistic effect in U-2OS cells, with CIs ranging from 0.80 to 0.97 at effect levels from IC₁₀ to IC₇₀. In addition, it was observed that celastrol/cisplatin upregulated the expression of Bcl-associated X protein, cytochrome c, caspase-3 and C/EBP homologous protein, and downregulated the expression of Bcl-2, poly(ADP-ribose) polymerase, 78 kDa glucose-regulated protein and caspase-9, whereas the expression of caspase-8 remained unchanged. To conclude, celastrol/cisplatin induced apoptosis in U-2OS cells via the mitochondrial and endoplasmic reticulum pathways, particularly in the former. Celastrol/cisplatin therefore exhibits potential as a novel therapeutic combination for the treatment of osteosarcoma.

Co-inhibition of BET and proteasome enhances ER stress and Bim-dependent apoptosis with augmented cancer therapeutic efficacy

Agents that inhibit bromodomain and extra-terminal domain (BET) protein have been actively tested in the clinic as potential anticancer drugs. Proteasome inhibitors such as carfilzomib (CFZ) are FDA-approved for the treatment of patients with advanced multiple myeloma and have been tested against other cancers. The current study focuses on the combination of a BET inhibitor (e.g., JQ1) and a proteasome inhibitor (e.g., CFZ) as a novel cancer therapeutic strategy and the underlying mechanisms. The tested combination (JQ1 with CFZ) synergistically decreased cell survival and enhanced apoptosis in vitro and inhibited tumor growth in vivo. The dramatic induction of apoptosis was accompanied by enhanced elevation of Bim and ER stress. Bim knockout significantly attenuated apoptosis induced by the combination, suggesting a critical role of Bim induction in mediating the enhanced induction of apoptosis by BET and proteasome co-inhibition. The combination significantly increased Bim mRNA levels with limited effect on Bim protein stability, suggesting a primary transcriptional regulation of enhanced Bim expression. Our findings warrant further investigation of this combinatorial strategy as an effective regimen against cancer in the clinic.

Simultaneously targeting DNA damage repair pathway and mTORC1/2 results in small cell lung cancer growth arrest via ER stress-induced apoptosis

Purpose: Small cell lung cancer (SCLC) is highly lethal with no effective therapy. Wee1 kinase inhibitor AZD1775 (MK-1775) and mTOR kinase inhibitor MLN0128 (TAK228) are in clinical trials for relapsed SCLC and recurrent lung cancer, respectively. However, there is no preclinical data combining these two drugs in human cancers. Methods: In this study, we set to investigate the combinatorial anti-tumor effects of AZD1775 and MLN0128 on two human SCLC cell lines H69 and H82 in vitro and in vivo. Results: We have found that AZD1775 or MLN0128 treatment results in remarkably suppressed cell proliferation and increased cell death in vitro, what's more, the salient finding here is the potent anti-tumor effect observed in combinatorial treatment in H82 xenograft tumor. Importantly, we have first observed marked induction of ER stress and CHOP-dependent SCLC cell apoptosis in MLN0128 and AZD1775-primed cells. Conclusion: Our study has first provided preclinical evidence that combination of AZD1775 and MLN0128 could be a novel effective therapy for advanced SCLC patients.

Second-generation proteasome inhibitor carfilzomib sensitizes neuroblastoma cells to doxorubicin-induced apoptosis

Neuroblastoma (NB), which accounts for about 15% of cancer-related mortality in children, is the most common extracranial malignant neoplasm in children. Elevated level of proteasome activity promotes cancer development and the inhibition of proteasome activity is a promising strategy for cancer treatment. Therefore, targeting proteasome by small molecule inhibitors may be a viable option for NB therapy. Here in this study, we show that a novel proteasome inhibitor Carfilzomib (CFZ) exerts anti-tumor effect on NB. CFZ caused decreased cell viability and attenuated colony formation ability of a subset of NB cell lines. CFZ induced cell apoptosis in NB cells. Moreover, CFZ enhanced the cytotoxic effect of doxorubicin (Dox) on NB cells and Dox-induced p38 and JNK phosphorylation. In addition, CFZ inhibited Dox-induced NF-κB activation by stabilizing the protein level of IκBα. Furthermore, CFZ induced apoptosis and augmented Dox-induced apoptosis in NB tumor cells in orthotopic xenograft mouse models. In summary, our study suggests that proteasome is a therapeutic target in NB and proteasome inhibition by CFZ is a potential therapeutic strategy for treating NB patients.