Targeting autophagy increases the efficacy of proteasome inhibitor treatment in multiple myeloma by induction of apoptosis and activation of JNK

Endoplasmic reticulum stress in the pathogenesis of chemotherapy-induced mucositis: Physiological mechanisms and therapeutic implications

Chemotherapy is a common and effective treatment for cancer, but these drugs are also associated with significant side effects affecting patients' well-being. One such debilitating side effect is mucositis, characterized by inflammation, ulcerations, and altered physiological functions of the gastrointestinal (GI) tract's mucosal lining. Understanding the mechanisms of chemotherapy-induced intestinal mucositis (CIM) is crucial for developing effective preventive measures and supportive care. Chemotherapeutics not only target cancer cells but also rapidly dividing cells in the GI tract. These drugs disrupt endoplasmic reticulum (ER) homeostasis, leading to ER-stress and activation of the unfolded protein response (UPR) in various intestinal epithelial cell types. The UPR triggers signaling pathways that exacerbate tissue inflammation and damage, influence the differentiation and fate of intestinal epithelial cells, and compromise the integrity of the intestinal mucosal barrier. These factors contribute significantly to mucositis development and progression. In this review, we aim to give an in-depth overview of the role of ER-stress in mucositis and its impact on GI function. This will provide valuable insights into the underlying mechanisms and highlighting potential therapeutic interventions that could improve treatment-outcomes and the quality of life of cancer patients.

Co-operation of MCL-1 and BCL-XL anti-apoptotic proteins in stromal protection of MM cells from carfilzomib mediated cytotoxicity

Introduction

BCL-2 family proteins are important for tumour cell survival and drug resistance in multiple myeloma (MM). Although proteasome inhibitors are effective anti-myeloma drugs, some patients are resistant and almost all eventually relapse. We examined the function of BCL-2 family proteins in stromal-mediated resistance to carfilzomib-induced cytotoxicity in MM cells.

Methods

Co-cultures employing HS5 stromal cells were used to model the interaction with stroma. MM cells were exposed to CFZ in a 1-hour pulse method. The expression of BCL-2 family proteins was assessed by flow cytometry and WB. Pro-survival proteins: MCL-1, BCL-2 and BCL-XL were inhibited using S63845, ABT-199 and A-1331852 respectively. Changes in BIM binding partners were examined by immunoprecipitation and WB.

Results

CFZ induced dose-dependent cell death of MM cells, primarily mediated by apoptosis. Culture of MM cells on HS-5 stromal cells resulted in reduced cytotoxicity to CFZ in a cell contact-dependent manner, upregulated expression of MCL-1 and increased dependency on BCL-XL. Inhibiting BCL-XL or MCL-1 with BH-3 mimetics abrogated stromal-mediated protection only at high doses, which may not be achievable in vivo. However, combining BH-3 mimetics at sub-therapeutic doses, which alone were without effect, significantly enhanced CFZ-mediated cytotoxicity even in the presence of stroma. Furthermore, MCL-1 inhibition led to enhanced binding between BCL-XL and BIM, while blocking BCL-XL increased MCL-1/BIM complex formation, indicating the cooperative role of these proteins.

Conclusion

Stromal interactions alter the dependence on BCL-2 family members, providing a rationale for dual inhibition to abrogate the protective effect of stroma and restore sensitivity to CFZ.

GZ17-6.02 interacts with proteasome inhibitors to kill multiple myeloma cells

GZ17-6.02, a synthetically manufactured compound containing isovanillin, harmine and curcumin, has undergone phase I evaluation in patients with solid tumors (NCT03775525) with a recommended phase 2 dose (RP2D) of 375 mg PO BID. GZ17-6.02 was more efficacious as a single agent at killing multiple myeloma cells than had previously been observed in solid tumor cell types. GZ17-6.02 interacted with proteasome inhibitors in a greater than additive fashion to kill myeloma cells and alone it killed inhibitor-resistant cells to a similar extent. The drug combination of GZ17-6.02 and bortezomib activated ATM, the AMPK and PERK and inactivated ULK1, mTORC1, eIF2α, NFκB and the Hippo pathway. The combination increased ATG13 S318 phosphorylation and the expression of Beclin1, ATG5, BAK and BIM, and reduced the levels of BCL-XL and MCL1. GZ17-6.02 interacted with bortezomib to enhance autophagosome formation and autophagic flux, and knock down of ATM, AMPKα, ULK1, Beclin1 or ATG5 significantly reduced both autophagy and tumor cell killing. Knock down of BAK and BIM significantly reduced tumor cell killing. The expression of HDACs1/2/3 was significantly reduced beyond that previously observed in solid tumor cells and required autophagy. This was associated with increased acetylation and methylation of histone H3. Combined knock down of HDACs1/2/3 caused activation of ATM and the AMPK and caused inactivation of ULK1, mTORC1, NFκB and the Hippo pathway. HDAC knock down also enhanced ATG13 phosphorylation, increased BAK levels and reduced those of BCL-XL. Collectively, our present studies support performing additional in vivo studies with multiple myeloma cells.

Autophagy-related mechanisms for treatment of multiple myeloma

Multiple myeloma (MM) is a type of hematological cancer that occurs when B cells become malignant. Various drugs such as proteasome inhibitors, immunomodulators, and compounds that cause DNA damage can be used in the treatment of MM. Autophagy, a type 2 cell death mechanism, plays a crucial role in determining the fate of B cells, either promoting their survival or inducing cell death. Therefore, autophagy can either facilitate the progression or hinder the treatment of MM disease. In this review, autophagy mechanisms that may be effective in MM cells were covered and evaluated within the contexts of unfolded protein response (UPR), bone marrow microenvironment (BMME), drug resistance, hypoxia, DNA repair and transcriptional regulation, and apoptosis. The genes that are effective in each mechanism and research efforts on this subject were discussed in detail. Signaling pathways targeted by new drugs to benefit from autophagy in MM disease were covered. The efficacy of drugs that regulate autophagy in MM was examined, and clinical trials on this subject were included. Consequently, among the autophagy mechanisms that are effective in MM, the most suitable ones to be used in the treatment were expressed. The importance of 3D models and microfluidic systems for the discovery of new drugs for autophagy and personalized treatment was emphasized. Ultimately, this review aims to provide a comprehensive overview of MM disease, encompassing autophagy mechanisms, drugs, clinical studies, and further studies.

STF-083010 an inhibitor of IRE1α endonuclease activity affects mitochondrial respiration and generation of mitochondrial membrane potential

STF-083010 is an inhibitor of endonuclease activity of inositol requiring-enzyme 1α (IRE1α) that is involved in activation of IRE1α-XBP1 axis of the unfolded protein response after ER stress. STF-083010 was tested as a possible antitumor agent in some previous studies exhibiting the ability either to induce death of tumour cells or to increase sensitivity of tumours cells to other neoplastic agents. STF-083010 exhibits also hepatoprotective effects in different models of liver injury and hepatic steatohepatitis. We have shown that STF-083010 has significant impact on mitochondrial functions that is not dependent on the way of STF-083010 application. We have observed that STF-083010 decrease of both maximal respiration (representing maximal electron transfer capacity of mitochondrial respiratory chain) and spare respiratory capacity after either incubation of the SH-SY5Y cells with STF-083010 or direct addition of STF-083010 to the respiration medium. In addition, we have documented impact of STF-083010 on generation of mitochondrial membrane potential (ΔΨm) that could be a result of decreased mitochondrial substrate level phosphorylation. Finally, increased sensitivity of ΔΨm to uncoupler in the presence of STF-083010 was documented. Our results indicate that STF-083010 has important impact on mitochondrial functions independently of its ability to inhibit endonuclease activity of IRE1α that is involved in activation of IRE1α-XBP1 axis of the unfolded protein response after ER stress. The impact of STF-083010 on mitochondrial functions could be associated with its possible off-target effect.

Targeting Myc-driven stress addiction in colorectal cancer

MYC is a proto-oncogene that encodes a powerful regulator of transcription and cellular programs essential for normal development, as well as the growth and survival of various types of cancer cells. MYC rearrangement and amplification is a common cause of hematologic malignancies. In epithelial cancers such as colorectal cancer, genetic alterations in MYC are rare. Activation of Wnt, ERK/MAPK, and PI3K/mTOR pathways dramatically increases Myc levels through enhanced transcription, translation, and protein stability. Elevated Myc promotes stress adaptation, metabolic reprogramming, and immune evasion to drive cancer development and therapeutic resistance through broad changes in transcriptional and translational landscapes. Despite intense interest and effort, Myc remains a difficult drug target. Deregulation of Myc and its targets has profound effects that vary depending on the type of cancer and the context. Here, we summarize recent advances in the mechanistic understanding of Myc-driven oncogenesis centered around mRNA translation and proteostress. Promising strategies and agents under development to target Myc are also discussed with a focus on colorectal cancer.

Inhibitors of the ATPase p97/VCP: From basic research to clinical applications

Protein homeostasis deficiencies underlie various cancers and neurodegenerative diseases. The ubiquitin-proteasome system (UPS) and autophagy are responsible for most of the protein degradation in mammalian cells and, therefore, represent attractive targets for cancer therapy and that of neurodegenerative diseases. The ATPase p97, also known as VCP, is a central component of the UPS that extracts and disassembles its substrates from various cellular locations and also regulates different steps in autophagy. Several UPS- and autophagy-targeting drugs are in clinical trials. In this review, we focus on the development of various p97 inhibitors, including the ATPase inhibitors CB-5083 and CB-5339, which reached clinical trials by demonstrating effective anti-tumor activity across various tumor models, providing an effective alternative to targeting protein degradation for cancer therapy. Here, we provide an overview of how different p97 inhibitors have evolved over time both as basic research tools and effective UPS-targeting cancer therapies in the clinic.

MAPK Cascade Signaling Is Involved in α-MMC Induced Growth Inhibition of Multiple Myeloma MM.1S Cells via G2 Arrest and Mitochondrial-Pathway-Dependent Apoptosis In Vitro

Multiple myeloma is a hematological malignancy characterized by the unrestricted proliferation of plasma cells that secrete monoclonal immunoglobulins in the bone marrow. Alpha-momorcharin (α-MMC) is a type I ribosome-inactivating protein extracted from the seeds of the edible plant Momordica charantia L., which has a variety of biological activities. This study aimed to investigate the inhibitory effect of α-MMC on the proliferation of multiple myeloma MM.1S cells and the molecular mechanism of MM.1S cell death induced through the activation of cell signal transduction pathways. The cell counting kit-8 (CCK-8) assay was used to determine the inhibitory effect of α-MMC on the proliferation of MM.1S cells and its toxic effect on normal human peripheral blood mononuclear cells (PBMCs). The effect of α-MMC on the MM.1S cells' morphology was observed via inverted microscope imaging. The effects of α-MMC on the MM.1S cell cycle, mitochondrial membrane potential (MMP), and apoptosis were explored using propidium iodide, JC-1, annexin V- fluorescein isothiocyanate/propidium iodide fluorescence staining, and flow cytometry (FCM) analysis. Western blot was used to detect the expressions levels of apoptosis-related proteins and MAPK-signaling-pathway-related proteins in MM.1S cells induced by α-MMC. The results of the CCK-8 showed that in the concentration range of no significant toxicity to PBMCs, α-MMC inhibited the proliferation of MM.1S cells in a time-dependent and concentration-dependent manner, and the IC₅₀ value was 13.04 and 7.518 μg/mL for 24 and 48 h, respectively. Through inverted microscope imaging, it was observed that α-MMC induced a typical apoptotic morphology in MM.1S cells. The results of the FCM detection and analysis showed that α-MMC could arrest the MM.1S cells cycle at the G2 phase, decrease the MMP, and induce cell apoptosis. Western blot analysis found that α-MMC upregulated the expression levels of Bax, Bid, cleaved caspase-3, and cleaved PARP, and downregulated the expression levels of Mcl-1. At the same time, α-MMC decreased the expression levels of p-c-Raf, p-MEK1/2, p-ERK1/2, p-MSK1, and p-P90RSK, and increased the expression levels of p-p38, p-SPAK/JNK, p-c-Jun, and p-ATF2. The above results suggest that α-MMC can inhibit the proliferation of multiple myeloma MM.1S cells. MAPK cascade signaling is involved in the growth inhibition effect of α-MMC on MM.1S cells via cycle arrest and mitochondrial-pathway-dependent apoptosis.

PPA1, an energy metabolism initiator, plays an important role in the progression of malignant tumors

Inorganic pyrophosphatase (PPA1) encoded by PPA1 gene belongs to Soluble Pyrophosphatases (PPase) family and is expressed widely in various tissues of Homo sapiens, as well as significantly in a variety of malignancies. The hydrolysis of inorganic pyrophosphate (PPi) to produce orthophosphate (Pi) not only dissipates the negative effects of PPi accumulation, but the energy released by this process also serves as a substitute for ATP. PPA1 is highly expressed in a variety of tumors and is involved in proliferation, invasion, and metastasis during tumor development, through the JNK/p53, Wnt/β-catenin, and PI3K/AKT/GSK-3β signaling pathways. Because of its remarkable role in tumor development, PPA1 may serve as a biological target for adjuvant therapy of tumor malignancies. Further, PPA1 is a potential biomarker to predict survival in patients with cancer, where the assessment of its transcriptional regulation can provide an in-depth understanding. Herein, we describe the signaling pathways through which PPA1 regulates malignant tumor progression and provide new insights to establish PPA1 as a biomarker for tumor diagnosis.