Relevance of mortalin to cancer cell stemness and cancer therapy

Targeting HSP90 in Gynecologic Cancer: Molecular Mechanisms and Therapeutic Approaches

One of the leading causes of mortality for women is gynecologic cancer (GC). Numerous molecules (tumor suppressor genes or oncogenes) are involved in this form of cancer's invasion, metastasis, tumorigenic process, and therapy resistance. Currently, there is a shortage of efficient methods to eliminate these diseases, hence it is crucial to carry out more extensive studies on GCs. Novel pharmaceuticals are required to surmount this predicament. Highly conserved molecular chaperon, heat shock protein (HSP) 90, is essential for the maturation of recently produced polypeptides and offers a refuge for misfolding or denatured proteins to be turned around. In cancer, the client proteins of HSP90 play a role in the entire process of oncogenesis, which is linked to all the characteristic features of cancer. In this study, we explore the various functions of HSPs in GC progression. We also discuss their potential as promising targets for pharmacological therapy.

Synthetic and Natural Inhibitors of Mortalin for Cancer Therapy

Upregulation of stress chaperone Mortalin has been closely linked to the malignant transformation of cells, tumorigenesis, the progression of tumors to highly aggressive stages, metastasis, drug resistance, and relapse. Various in vitro and in vivo assays have provided evidence of the critical role of Mortalin upregulation in promoting cancer cell characteristics, including proliferation, migration, invasion, and the inhibition of apoptosis, a consistent feature of most cancers. Given its critical role in several steps in oncogenesis and multi-modes of action, Mortalin presents a promising target for cancer therapy. Consequently, Mortalin inhibitors are emerging as potential anti-cancer drugs. In this review, we discuss various inhibitors of Mortalin (peptides, small RNAs, natural and synthetic compounds, and antibodies), elucidating their anti-cancer potentials.

Targeting GRP75 with a Chlorpromazine Derivative Inhibits Endometrial Cancer Progression Through GRP75-IP3R-Ca2+-AMPK Axis

Tumors often overexpress glucose-regulated proteins, and agents that interfere with the production or activity of these proteins may represent novel cancer treatments. The chlorpromazine derivative JX57 exhibits promising effects against endometrial cancer with minimal extrapyramidal side effects; however, its mechanisms of action are currently unknown. Here, glucose-regulated protein 75 kD (GRP75) is identified as a direct target of JX57 using activity-based protein profiling and loss-of-function experiments. The findings show that GRP75 is necessary for the biological activity of JX57, as JX57 exhibits moderate anticancer properties in GRP75-deficient cancer cells, both in vitro and in vivo. High GRP75 expression is correlated with poor differentiation and poor survival in patients with endometrial cancer, whereas the knockdown of GRP75 can significantly suppress tumor growth. Mechanistically, the direct binding of JX57 to GRP75 impairs the structure of the mitochondria-associated endoplasmic reticulum membrane and disrupts the endoplasmic reticulum-mitochondrial calcium homeostasis, resulting in a mitochondrial energy crisis and AMP-activated protein kinase activation. Taken together, these findings highlight GRP75 as a potential prognostic biomarker and direct therapeutic target in endometrial cancer and suggest that the chlorpromazine derivative JX57 can potentially be a new therapeutic option for endometrial cancer.

Human HSP70-escort protein 1 (hHep1) interacts with negatively charged lipid bilayers and cell membranes

Human Hsp70-escort protein 1 (hHep1) is a cochaperone that assists in the function and stability of mitochondrial HSPA9. Similar to HSPA9, hHep1 is located outside the mitochondria and can interact with liposomes. In this study, we further investigated the structural and thermodynamic behavior of interactions between hHep1 and negatively charged liposomes, as well as interactions with cellular membranes. Our results showed that hHep1 interacts peripherally with liposomes formed by phosphatidylserine and cardiolipin and remains partially structured, exhibiting similar affinities for both. In addition, after being added to the cell membrane, recombinant hHep1 was incorporated by cells in a dose-dependent manner. Interestingly, the association of HSPA9 with hHep1 improved the incorporation of these proteins into the lipid bilayer. These results demonstrated that hHep1 can interact with lipids also present in the plasma membrane, indicating roles for this cochaperone outside of mitochondria.

Therapeutic strategies of dual-target small molecules to overcome drug resistance in cancer therapy

Despite some advances in targeted therapeutics of human cancers, curative cancer treatment still remains a tremendous challenge due to the occurrence of drug resistance. A variety of underlying resistance mechanisms to targeted cancer drugs have recently revealed that the dual-target therapeutic strategy would be an attractive avenue. Compared to drug combination strategies, one agent simultaneously modulating two druggable targets generally shows fewer adverse reactions and lower toxicity. As a consequence, the dual-target small molecule has been extensively explored to overcome drug resistance in cancer therapy. Thus, in this review, we focus on summarizing drug resistance mechanisms of cancer cells, such as enhanced drug efflux, deregulated cell death, DNA damage repair, and epigenetic alterations. Based upon the resistance mechanisms, we further discuss the current therapeutic strategies of dual-target small molecules to overcome drug resistance, which will shed new light on exploiting more intricate mechanisms and relevant dual-target drugs for future cancer therapeutics.

Clinical Relevance of Mortalin in Ovarian Cancer Patients

Background: Ovarian cancer (OC) is the most lethal malignancy of the female reproductive tract. Consequently, a better understanding of the malignant features in OC is pertinent. Mortalin (mtHsp70/GRP75/PBP74/HSPA9/HSPA9B) promotes cancer development, progression, metastasis, and recurrence. Yet, there is no parallel evaluation and clinical relevance of mortalin in the peripheral and local tumor ecosystem in OC patients. Methods: A cohort of 92 pretreatment women was recruited, including 50 OC patients, 14 patients with benign ovarian tumors, and 28 healthy women. Blood plasma and ascites fluid-soluble mortalin concentrations were measured by ELISA. Mortalin protein levels in tissues and OC cells were analyzed using proteomic datasets. The gene expression profile of mortalin in ovarian tissues was evaluated through the analysis of RNAseq data. Kaplan-Meier analysis was used to demonstrate the prognostic relevance of mortalin. Results: First, we found upregulation of local mortalin in two different ecosystems, i.e., ascites and tumor tissues in human OC compared to control groups. Second, abundance expression of local tumor mortalin is associated with cancer-driven signaling pathways and worse clinical outcome. Third, high mortalin level in tumor tissues, but not in the blood plasma or ascites fluid, predicts worse patient prognosis. Conclusions: Our findings demonstrate a previously unknown mortalin profile in peripheral and local tumor ecosystem and its clinical relevance in OC. These novel findings may serve clinicians and investigators in the development of biomarker-based targeted therapeutics and immunotherapies.

Mortalin: Protein partners, biological impacts, pathological roles, and therapeutic opportunities

Mortalin (GRP75, HSPA9A), a heat shock protein (HSP), regulates a wide range of cellular processes, including cell survival, growth, and metabolism. The regulatory functions of mortalin are mediated through a diverse set of protein partners associated with different cellular compartments, which allows mortalin to perform critical functions under physiological conditions, including mitochondrial protein quality control. However, alteration of mortalin's activities, its abnormal subcellular compartmentalization, and its protein partners turn mortalin into a disease-driving protein in different pathological conditions, including cancers. Here, mortalin's contributions to tumorigenic pathways are explained. Pathology information based on mortalin's RNA expression extracted from The Cancer Genome Atlas (TCGA) transcriptomic database indicates that mortalin has an independent prognostic value in common tumors, including lung, breast, and colorectal cancer (CRC). Subsequently, the binding partners of mortalin reported in different cellular models, from yeast to mammalian cells, and its regulation by post-translational modifications are discussed. Finally, we focus on colorectal cancer and discuss how mortalin and its tumorigenic downstream protein targets are regulated by a ubiquitin-like protein through the 26S proteasomal degradation machinery. A broader understanding of the function of mortalin and its positive and negative regulation in the formation and progression of human diseases, particularly cancer, is essential for developing new strategies to treat a diverse set of human diseases critically associated with dysregulated mortalin.

Therapeutic Targeting of NF-κB in Acute Lung Injury: A Double-Edged Sword

Acute lung injury/acute respiratory distress syndrome (ALI/ARDS) is a devastating disease that can be caused by a variety of conditions including pneumonia, sepsis, trauma, and most recently, COVID-19. Although our understanding of the mechanisms of ALI/ARDS pathogenesis and resolution has considerably increased in recent years, the mortality rate remains unacceptably high (~40%), primarily due to the lack of effective therapies for ALI/ARDS. Dysregulated inflammation, as characterized by massive infiltration of polymorphonuclear leukocytes (PMNs) into the airspace and the associated damage of the capillary-alveolar barrier leading to pulmonary edema and hypoxemia, is a major hallmark of ALI/ARDS. Endothelial cells (ECs), the inner lining of blood vessels, are important cellular orchestrators of PMN infiltration in the lung. Nuclear factor-kappa B (NF-κB) plays an essential role in rendering the endothelium permissive for PMN adhesion and transmigration to reach the inflammatory site. Thus, targeting NF-κB in the endothelium provides an attractive approach to mitigate PMN-mediated vascular injury, not only in ALI/ARDS, but in other inflammatory diseases as well in which EC dysfunction is a major pathogenic mechanism. This review discusses the role and regulation of NF-κB in the context of EC inflammation and evaluates the potential and problems of targeting it as a therapy for ALI/ARDS.

Identification of a new member of Mortaparib class of inhibitors that target mortalin and PARP1

Mortalin, a heat shock family protein enriched in cancer cells, is known to inactivate tumor suppressor protein p53. Abrogation of mortalin-p53 interaction and reactivation of p53 has been shown to trigger growth arrest/apoptosis in cancer cells and hence, suggested to be useful in cancer therapy. In this premise, we earlier screened a chemical library to identify potential disruptors of mortalin-p53 interaction, and reported two novel synthetic small molecules (5-[1-(4-methoxyphenyl) (1,2,3,4-tetraazol-5-yl)]-4-phenylpyrimidine-2-ylamine) and (4-[(1E)-2-(2-phenylindol-3-yl)-1-azavinyl]-1,2,4-triazole) called Mortaparib and Mortaparib^Plus, respectively. These compounds were shown to possess anticancer activity that was mediated through targeting mortalin and PARP1 proteins, essential for cancer cell survival and proliferation. Here, we report characterization of the third compound, {4-[(4-amino-5-thiophen-2-yl-1,2,4-triazol-3-yl)sulfanylmethyl]-N-(4-methoxyphenyl)-1,3-thiazol-2-amine}, isolated in the same screening. Extensive computational and molecular analyses suggested that the new compound has the capability to interact with mortalin, p53, and PARP1. We provide evidence that this new compound, although required in high concentration as compared to the earlier two compounds (Mortaparib and Mortaparib^Plus) and hence called Mortaparib^Mild, also downregulates mortalin and PARP1 expression and functions in multiple ways impeding cancer cell proliferation and migration characteristics. Mortaparib^Mild is a novel candidate anticancer compound that warrants further experimental and clinical attention.

Novel secretion modification region (SMR) peptide exhibits anti-metastatic properties in human breast cancer cells

Breast cancer is the second leading cause of cancer-related mortality in women worldwide, with nearly 90% attributed to metastatic progression. Exosomes containing epithelial–mesenchymal transition (EMT) ‘programs’ transmit pro-metastatic phenotypes. Our group discovered and developed a novel anti-cancer SMR peptide that antagonizes breast cancer cell exosome release resulting in cell cycle arrest and tumor growth suppression. This study aims to evaluate the anti-metastatic capabilities of the SMR peptide, focusing on exosomes and EMT. Breast cancer cell lines MDA-MB-231 and MCF-7 were treated with the SMRwt peptide, and the following assays were performed: cell wound-healing, migration, invasion. The SMRwt peptide consists of the following amino acid sequence VGFPVAAVGFPVDYKDDDDK and contains the SMR domain (⁶⁶VGFPV⁷⁰) of the HIV-1 Nef protein. Western blot analysis detected epithelial and mesenchymal markers to evaluate EMT progression. Extracellular vesicle type and quantity were assessed through NanoSight analysis. Mortalin and Vimentin knockdown was achieved through antibody targeting and miRNAs. Data gathered demonstrated that the SMR peptide interacts with Mortalin and Vimentin to inhibit pro-EMT exosome release and induce EMT tumor suppressor protein expression. Specifically, SMRwt treatment reduced mesenchymal markers Mortalin and Vimentin expression, while the epithelial marker E-cadherin expression was increased in breast cancer cells and breast cancer-derived exosomes. The SMR peptide specificity was identified as no effect was observed for MCF-10A exosome release or function. Direct Mortalin knockdown paralleled the results of SMR peptide treatment with an effective blockade of breast cancer cell migration. Conversely, the invasion assay differed between breast cancer cell lines with invasion blocked for in MCF-7 but not in MDA-MB-231. These results reinforce the therapeutic value of targeting breast cancer exosome release and reinforce Mortalin and Vimentin as critical regulators and therapeutic targets in breast cancer cell progression, EMT, and metastatic potential. A greater understanding of the SMR peptide mechanism of action will benefit the therapeutic design of anti-metastatic agents.

The mitochondrial unfolded protein response (UPRmt): shielding against toxicity to mitochondria in cancer

Mitochondria are essential for tumor growth and progression. However, the heavy demand for mitochondrial activity in cancer leads to increased production of mitochondrial reactive oxygen species (mtROS), accumulation of mutations in mitochondrial DNA, and development of mitochondrial dysfunction. If left unchecked, excessive mtROS can damage and unfold proteins in the mitochondria to an extent that becomes lethal to the tumor. Cellular systems have evolved to combat mtROS and alleviate mitochondrial stress through a quality control mechanism called the mitochondrial unfolded protein response (UPR^mt). The UPR^mt system is composed of chaperones and proteases, which promote protein folding or eliminate mitochondrial proteins damaged by mtROS, respectively. UPR^mt is conserved and activated in cancer in response to mitochondrial stress to maintain mitochondrial integrity and support tumor growth. In this review, we discuss how mitochondria become dysfunctional in cancer and highlight the tumor-promoting functions of key components of the UPR^mt.

Why is Mortalin a Potential Therapeutic Target for Cancer?

Cancer is one of the leading causes of death worldwide, accounting for nearly 10 million deaths in 2020. Therefore, cancer therapy is a priority research field to explore the biology of the disease and identify novel targets for the development of better treatment strategies. Mortalin is a member of the heat shock 70 kDa protein family. It is enriched in several types of cancer and contributes to carcinogenesis in various ways, including inactivation of the tumor suppressor p53, deregulation of apoptosis, induction of epithelial–mesenchymal transition, and enhancement of cancer stemness. It has been studied extensively as a therapeutic target for cancer treatment, and several types of anti-mortalin molecules have been discovered that effectively suppress the tumor cell growth. In this review, we 1) provide a comprehensive sketch of the role of mortalin in tumor biology; 2) discuss various anti-mortalin molecules, including natural compounds, synthetic small molecules, peptides, antibodies, and nucleic acids, that have shown potential for cancer treatment in laboratory studies; and 3) provide future perspectives in cancer treatment.

ErbB3-Targeting Oncolytic Adenovirus Causes Potent Tumor Suppression by Induction of Apoptosis in Cancer Cells

Cancer is a multifactorial and deadly disease. Despite major advancements in cancer therapy in the last two decades, cancer incidence is on the rise and disease prognosis still remains poor. Furthermore, molecular mechanisms of cancer invasiveness, metastasis, and drug resistance remain largely elusive. Targeted cancer therapy involving the silencing of specific cancer-enriched proteins by small interfering RNA (siRNA) offers a powerful tool. However, its application in clinic is limited by the short half-life of siRNA and warrants the development of efficient and stable siRNA delivery systems. Oncolytic adenovirus-mediated therapy offers an attractive alternative to the chemical drugs that often suffer from innate and acquired drug resistance. In continuation to our reports on the development of oncolytic adenovirus-mediated delivery of shRNA, we report here the replication-incompetent (dAd/shErbB3) and replication-competent (oAd/shErbB3) oncolytic adenovirus systems that caused efficient and persistent targeting of ErbB3. We demonstrate that the E1A coded by oAd/shErbB, in contrast to dAd/shErbB, caused downregulation of ErbB2 and ErbB3, yielding stronger downregulation of the ErbB3-oncogenic signaling axis in in vitro models of lung and breast cancer. These results were validated by in vivo antitumor efficacy of dAd/shErbB3 and oAd/shErbB3.

In-silico validation of novel therapeutic activities of withaferin a using molecular docking and dynamics studies

Withaferin A is a bioactive molecule of W. somnifera. We access its efficacy against various target proteins associated with Cancer, Type-II Diabetes and hypercholesterolemia using molecular docking. Although it's efficacy against some of these targets have been reported earlier, we validate each mechanism in order to report the most appropriate mechanism of action. We explain the anti-cancer activity of Withaferin A by inhibition of Mortalin (mtHsp70) and Nrf2 protein with binding energies -8.85 kcal/mol and -12.59 kcal/mol respectively. Similarly, the anti-diabetic activity could be explained by inhibition of alpha and betα-glucosidase with binding energies -6.44 and -4.43 kcal/mol respectively and the cholesterol reduction could be explained by its ability to inhibition of NPC1 and SRB1 with binding energies -5.73 and -7.16 kcal/mol respectively. The molecular dynamics of the apoprotein and the protein-ligand complex simulated for the best targets of each activity namely Nrf2 protein for anti-cancer, α-glucosidase for anti-diabetic and SR-B1 for anti-hypercholesterolemia activity indicated the formation of stable complexes due to low RMSD deviations, low RMSF fluctuations and low RG values after the docking simulation. Finally, an ADME + T (Adsorption, distribution, metabolism, excretion and toxicity) prediction on Withaferin A showed that it obeyed all the Lipinsky's rules and qualified the drug-like criteria. All these results validate that Withaferin A possess potential anti-cancer, anti-diabetic and cholesterol reducing properties. This is the first report that indicates the possibility of Withaferin A binding and inhibiting SR-B1 as a mechanism of its anti-hypercholesterolemia activity.

Investigation of the effects of overexpression of jumping translocation breakpoint (JTB) protein in MCF7 cells for potential use as a biomarker in breast cancer

Jumping translocation breakpoint (JTB) gene acts as a tumor suppressor or an oncogene in different malignancies, including breast cancer (BC), where it was reported as overexpressed. However, the molecular functions, biological processes and underlying mechanisms through which JTB protein causes increased cell growth, proliferation and invasion is still not fully deciphered. Our goal is to identify the functions of JTB protein by cellular proteomics approaches. MCF7 breast cancer cells were transfected with sense orientation of hJTB cDNA in HA, His and FLAG tagged CMV expression vector to overexpress hJTB and the expression levels were confirmed by Western blotting (WB). Proteins extracted from transfected cells were separated by SDS-PAGE and the in-gel digested peptides were analyzed by nano-liquid chromatography tandem mass spectrometry (nanoLC-MS/MS). By comparing the proteome of cells with upregulated conditions of JTB vs control and identifying the protein dysregulation patterns, we aim to understand the function of this protein and its contribution to tumorigenesis. Gene Set Enrichment Analysis (GSEA) algorithm was performed to investigate the biological processes and pathways that are associated with the JTB protein upregulation. The results demonstrated four significantly enriched gene sets from the following significantly upregulated pathways: mitotic spindle assembly, estrogen response late, epithelial-to-mesenchymal transition (EMT) and estrogen response early. JTB protein itself is involved in mitotic spindle pathway by its role in cell division/cytokinesis, and within estrogen response early and late pathways, contributing to discrimination between luminal and mesenchymal breast cancer. Thus, the overexpressed JTB condition was significantly associated with an increased expression of ACTNs, FLNA, FLNB, EZR, MYOF, COL3A1, COL11A1, HSPA1A, HSP90A, WDR, EPPK1, FASN and FOXA1 proteins related to deregulation of cytoskeletal organization and biogenesis, mitotic spindle organization, ECM remodeling, cellular response to estrogen, proliferation, migration, metastasis, increased lipid biogenesis, endocrine therapy resistance, antiapoptosis and discrimination between different breast cancer subtypes. Other upregulated proteins for overexpressed JTB condition are involved in multiple cellular functions and pathways that become dysregulated, such as tumor microenvironment (TME) acidification, the transmembrane transport pathways, glycolytic flux, iron metabolism and oxidative stress, metabolic reprogramming, nucleocytosolic mRNA transport, transcriptional activation, chromatin remodeling, modulation of cell death pathways, stress responsive pathways, and cancer drug resistance. The downregulated proteins for overexpressed JTB condition are involved in adaptive communication between external and internal environment of cells and maintenance between pro-apoptotic and anti-apoptotic signaling pathways, vesicle trafficking and secretion, DNA lesions repair and suppression of genes involved in tumor progression, proteostasis, redox state regulation, biosynthesis of macromolecules, lipolytic pathway, carbohydrate metabolism, dysregulation of ubiquitin-mediated degradation system, cancer cell immune escape, cell-to-cell and cell-to-ECM interactions, and cytoskeletal behaviour. There were no significantly enriched downregulated pathways.

Insight into the mitochondrial unfolded protein response and cancer: opportunities and challenges

The mitochondrial unfolded protein response (UPR^mt) is an evolutionarily conserved protective transcriptional response that maintains mitochondrial proteostasis by inducing the expression of mitochondrial chaperones and proteases in response to various stresses. The UPR^mt-mediated transcriptional program requires the participation of various upstream signaling pathways and molecules. The factors regulating the UPR^mt in Caenorhabditis elegans (C. elegans) and mammals are both similar and different. Cancer cells, as malignant cells with uncontrolled proliferation, are exposed to various challenges from endogenous and exogenous stresses. Therefore, in cancer cells, the UPR^mt is hijacked and exploited for the repair of mitochondria and the promotion of tumor growth, invasion and metastasis. In this review, we systematically introduce the inducers of UPR^mt, the biological processes in which UPR^mt participates, the mechanisms regulating the UPR^mt in C. elegans and mammals, cross-tissue signal transduction of the UPR^mt and the roles of the UPR^mt in promoting cancer initiation and progression. Disrupting proteostasis in cancer cells by targeting UPR^mt constitutes a novel anticancer therapeutic strategy.

Loss of Function of mtHsp70 Chaperone Variants Leads to Mitochondrial Dysfunction in Congenital Sideroblastic Anemia

Congenital Sideroblastic Anemias (CSA) is a group of rare genetic disorders characterized by the abnormal accumulation of iron in erythrocyte precursors. A common hallmark underlying these pathological conditions is mitochondrial dysfunction due to altered protein homeostasis, heme biosynthesis, and oxidative phosphorylation. A clinical study on congenital sideroblastic anemia has identified mutations in mitochondrial Hsp70 (mtHsp70/Mortalin). Mitochondrial Hsp70 plays a critical role in maintaining mitochondrial function by regulating several pathways, including protein import and folding, and iron-sulfur cluster synthesis. Owing to the structural and functional homology between human and yeast mtHsp70, we have utilized the yeast system to delineate the role of mtHsp70 variants in the etiology of CSA’s. Analogous mutations in yeast mtHsp70 exhibited temperature-sensitive growth phenotypes under non-respiratory and respiratory conditions. In vivo analyses indicate a perturbation in mitochondrial mass and functionality accompanied by an alteration in the organelle network and cellular redox levels. Preliminary in vitro biochemical studies of mtHsp70 mutants suggest impaired import function, altered ATPase activity and substrate interaction. Together, our findings suggest the loss of chaperone activity to be a pivotal factor in the pathophysiology of congenital sideroblastic anemia.

A Low Dose Combination of Withaferin A and Caffeic Acid Phenethyl Ester Possesses Anti-Metastatic Potential In Vitro: Molecular Targets and Mechanisms

Simple Summary

Cancer therapy suffers from its high cost and high rate of adverse effects and relapse of the disease. Hence, the new (preferably natural), economic and safer therapeutic as well preventive measures have been on demand and have been subject of priority research. We have, earlier, demonstrated anticancer activity in the extracts of Ashwagandha leaves and propolis. A combination of Wi-A (an active anticancer ingredient in Ashwagandha extract) and CAPE (an active anticancer ingredient in propolis) was earlier shown to offer higher and cancer cell-selective cytotoxicity. In the present study, we report an anti-metastasis activity in the low dose combination of Wi-A and CAPE along with its mechanism of action and propose its use in cancer metastasis treatment.

Abstract

Withaferin A (Wi-A) and Caffeic Acid Phenethyl Ester (CAPE) are the bioactive ingredients of Ashwagandha (Withania somnifera) and propolis, respectively. Both of these natural compounds have been shown to possess anticancer activity. In the present study, we recruited a low dose of each of these compounds and developed a combination that exhibited remarkably potent anti-migratory and anti-angiogenic activities. Extensive molecular analyses including a cDNA array and expression analyses of the specific gene targets demonstrated that such activities are mediated through their effect on cell adhesion/tight junction proteins (Claudins, E-cadherin), inhibition of canonical Wnt/β-catenin signaling pathways and the consequent downregulation of EMT-signaling proteins (Vimentin, MMPs, VEGF and VEGFR) that play a critical role in cancer metastasis. The data supported that this novel combination of Wi-A and CAPE (Wi-ACAPE, containing 0.5 µM of Wi-A and 10 µM of CAPE) may be recruited for the treatment of metastatic and aggressive cancers and, hence, warrant further evaluation by recruiting a variety of experimental and clinical metastatic models.

Mitochondrial chaperones in human health and disease

Molecular chaperones are a family of proteins that maintain cellular protein homeostasis through non-covalent peptide folding and quality control mechanisms. The chaperone proteins found within mitochondria play significant protective roles in mitochondrial biogenesis, quality control, and stress response mechanisms. Defective mitochondrial chaperones have been implicated in aging, neurodegeneration, and cancer. In this review, we focus on the two most prominent mitochondrial chaperones: mtHsp60 and mtHsp70. These proteins demonstrate different cellular localization patterns, interact with different targets, and have different functional activities. We discuss the structure and function of these prominent mitochondrial chaperone proteins and give an update on newly discovered regulatory mechanisms and disease implications.

A pan-metazoan concept for adult stem cells: the wobbling Penrose landscape

Adult stem cells (ASCs) in vertebrates and model invertebrates (e.g. Drosophila melanogaster) are typically long-lived, lineage-restricted, clonogenic and quiescent cells with somatic descendants and tissue/organ-restricted activities. Such ASCs are mostly rare, morphologically undifferentiated, and undergo asymmetric cell division. Characterized by 'stemness' gene expression, they can regulate tissue/organ homeostasis, repair and regeneration. By contrast, analysis of other animal phyla shows that ASCs emerge at different life stages, present both differentiated and undifferentiated phenotypes, and may possess amoeboid movement. Usually pluri/totipotent, they may express germ-cell markers, but often lack germ-line sequestering, and typically do not reside in discrete niches. ASCs may constitute up to 40% of animal cells, and participate in a range of biological phenomena, from whole-body regeneration, dormancy, and agametic asexual reproduction, to indeterminate growth. They are considered legitimate units of selection. Conceptualizing this divergence, we present an alternative stemness metaphor to the Waddington landscape: the 'wobbling Penrose' landscape. Here, totipotent ASCs adopt ascending/descending courses of an 'Escherian stairwell', in a lifelong totipotency pathway. ASCs may also travel along lower stemness echelons to reach fully differentiated states. However, from any starting state, cells can change their stemness status, underscoring their dynamic cellular potencies. Thus, vertebrate ASCs may reflect just one metazoan ASC archetype.

HSP70 and HSP90 in Cancer: Cytosolic, Endoplasmic Reticulum and Mitochondrial Chaperones of Tumorigenesis

HSP70 and HSP90 are two powerful chaperone machineries involved in survival and proliferation of tumor cells. Residing in various cellular compartments, HSP70 and HSP90 perform specific functions. Concurrently, HSP70 and HSP90 homologs may also translocate from their primary site under various stress conditions. Herein, we address the current literature on the role of HSP70 and HSP90 chaperone networks in cancer. The goal is to provide a comprehensive review on the functions of cytosolic, mitochondrial and endoplasmic reticulum HSP70 and HSP90 homologs in cancer. Given that high expression of HSP70 and HSP90 enhances tumor development and associates with tumor aggressiveness, further understanding of HSP70 and HSP90 chaperone networks may provide clues for the discoveries of novel anti-cancer therapies.

Salvianolic acid B targets mortalin and inhibits the migration and invasion of hepatocellular carcinoma via the RECK/STAT3 pathway

BACKGROUND

Tumor migration and invasion is a complex and diverse process that involves the epithelial-mesenchymal transition (EMT) of tumor cells and degradation of the extracellular matrix by matrix metalloproteases (MMPs). Mortalin is an important oncogene. It has been reported to play an important role in tumor migration and invasion through various signaling pathways, but the underlying mechanism is not fully understood.

METHODS

Here, we investigated the role of mortalin in the migration of the hepatocellular carcinoma (HCC) cell lines HepG2 and HCCLM3.

RESULTS

The overexpression of mortalin in HepG2 cells decreased the protein level of reversion-inducing cysteine-rich protein with Kazal motifs (RECK) and activated the phosphorylation and acetylation of STAT3, thereby up-regulating matrix metalloproteinase 9 (MMP9) and promoting cell migration and invasion. In contrast, in HCCLM3 cells, mortalin knockdown increased the expression of RECK, inhibited the STAT3 pathway and the activity of MMP9, and inhibited cell migration and invasion. Furthermore, we found that salvianolic acid B, a caffeic acid phenethyl ester analog, specifically bound to mortalin and increased the degradation of mortalin proteasomes through ubiquitination, thereby up-regulating RECK, inhibiting STAT3, and finally inhibiting the migration and invasion of HCC cells.

CONCLUSION

Our work suggested that mortalin is a potential therapeutic target for hepatocellular carcinoma.

Megakaryocytes Mediate Hyperglycemia-Induced Tumor Metastasis

High blood glucose has long been established as a risk factor for tumor metastasis, yet the molecular mechanisms underlying this association have not been elucidated. Here we describe that hyperglycemia promotes tumor metastasis via increased platelet activity. Administration of glucose, but not fructose, reprogrammed the metabolism of megakaryocytes to indirectly prime platelets into a prometastatic phenotype with increased adherence to tumor cells. In megakaryocytes, a glucose metabolism-related gene array identified the mitochondrial molecular chaperone glucose-regulated protein 75 (GRP75) as a trigger for platelet activation and aggregation by stimulating the Ca²⁺-PKCα pathway. Genetic depletion of Glut1 in megakaryocytes blocked MYC-induced GRP75 expression. Pharmacologic blockade of platelet GRP75 compromised tumor-induced platelet activation and reduced metastasis. Moreover, in a pilot clinical study, drinking a 5% glucose solution elevated platelet GRP75 expression and activated platelets in healthy volunteers. Platelets from these volunteers promoted tumor metastasis in a platelet-adoptive transfer mouse model. Together, under hyperglycemic conditions, MYC-induced upregulation of GRP75 in megakaryocytes increases platelet activation via the Ca²⁺-PKCα pathway to promote cancer metastasis, providing a potential new therapeutic target for preventing metastasis. SIGNIFICANCE: This study provides mechanistic insights into a glucose-megakaryocyte-platelet axis that promotes metastasis and proposes an antimetastatic therapeutic approach by targeting the mitochondrial protein GRP75.

NKX3.1 Localization to Mitochondria Suppresses Prostate Cancer Initiation

Mitochondria provide the first line of defense against the tumor-promoting effects of oxidative stress. Here we show that the prostate-specific homeoprotein NKX3.1 suppresses prostate cancer initiation by protecting mitochondria from oxidative stress. Integrating analyses of genetically engineered mouse models, human prostate cancer cells, and human prostate cancer organotypic cultures, we find that, in response to oxidative stress, NKX3.1 is imported to mitochondria via the chaperone protein HSPA9, where it regulates transcription of mitochondrial-encoded electron transport chain (ETC) genes, thereby restoring oxidative phosphorylation and preventing cancer initiation. Germline polymorphisms of NKX3.1 associated with increased cancer risk fail to protect from oxidative stress or suppress tumorigenicity. Low expression levels of NKX3.1 combined with low expression of mitochondrial ETC genes are associated with adverse clinical outcome, whereas high levels of mitochondrial NKX3.1 protein are associated with favorable outcome. This work reveals an extranuclear role for NKX3.1 in suppression of prostate cancer by protecting mitochondrial function. SIGNIFICANCE: Our findings uncover a nonnuclear function for NKX3.1 that is a key mechanism for suppression of prostate cancer. Analyses of the expression levels and subcellular localization of NKX3.1 in patients at risk of cancer progression may improve risk assessment in a precision prevention paradigm, particularly for men undergoing active surveillance.See related commentary by Finch and Baena, p. 2132.This article is highlighted in the In This Issue feature, p. 2113.

Experimental Evidence for Therapeutic Potentials of Propolis

Propolis is produced by honeybees from materials collected from plants they visit. It is a resinous material having mixtures of wax and bee enzymes. Propolis is also known as bee glue and used by bees as a building material in their hives, for blocking holes and cracks, repairing the combs and strengthening their thin borders. It has been extensively used since ancient times for different purposes in traditional human healthcare practices. The quality and composition of propolis depend on its geographic location, climatic zone and local flora. The New Zealand and Brazilian green propolis are the two main kinds that have been extensively studied in recent years. Their bioactive components have been found to possess a variety of therapeutic potentials. It was found that Brazilian green propolis improves the cognitive functions of mild cognitive impairments in patients living at high altitude and protects them from neurodegenerative damage through its antioxidant properties. It possesses artepillin C (ARC) as the key component, also known to possess anticancer potential. The New Zealand propolis contains caffeic acid phenethyl ester (CAPE) as the main bioactive with multiple therapeutic potentials. Our lab performed in vitro and in vivo assays on the extracts prepared from New Zealand and Brazilian propolis and their active ingredients. We provided experimental evidence that these extracts possess anticancer, antistress and hypoxia-modulating activities. Furthermore, their conjugation with γCD proved to be more effective. In the present review, we portray the experimental evidence showing that propolis has the potential to be a candidate drug for different ailments and improve the quality of life.

Mutant p53L194F Harboring Luminal-A Breast Cancer Cells Are Refractory to Apoptosis and Cell Cycle Arrest in Response to MortaparibPlus, a Multimodal Small Molecule Inhibitor

Simple Summary

Tumor suppressor protein p53 is a master regulator that inhibits the process of oncogenesis by induction of cell senescence/cell cycle arrest/apoptosis during normal and stressed states of cells. It is functionally inactivated in the majority of cancers. Mortalin, a member of the Hsp70 family of proteins, enriched in cancer cells, is known to cause cytoplasmic sequestration and inactivation of the p53’s transcriptional activation function. Inhibition of mortalin–p53 interaction and reactivation of p53 functions by natural and synthetic drugs has emerged as a possible cancer therapeutic strategy. We recently reported a novel multimodal small molecule, named Mortaparib^Plus, that inhibited mortalin–p53 interaction and caused reactivation of p53 function in colorectal cancer cells. Here, we report its effect on breast cancer cells with wildtype (MCF-7) or mutant (T47D) p53 status.

Abstract

We previously performed a drug screening to identify a potential inhibitor of mortalin–p53 interaction. In four rounds of screenings based on the shift in mortalin immunostaining pattern from perinuclear to pan-cytoplasmic and nuclear enrichment of p53, we had identified Mortaparib^Plus (4-[(1E)-2-(2-phenylindol-3-yl)-1-azavinyl]-1,2,4-triazole) as a novel synthetic small molecule. In order to validate its activity and mechanism of action, we recruited Luminal-A breast cancer cells, MCF-7 (p53^{wild type}) and T47D (p53^L194F) and performed extensive biochemical and immunocytochemical analyses. Molecular analyses revealed that Mortaparib^Plus is capable of abrogating mortalin–p53 interaction in both MCF-7 and T47D cells. Intriguingly, upregulation of transcriptional activation function of p53 (as marked by upregulation of the p53 effector gene—p21^WAF1—responsible for cell cycle arrest and apoptosis) was recorded only in Mortaparib^Plus-treated MCF-7 cells. On the other hand, Mortaparib^Plus-treated T47D cells exhibited hyperactivation of PARP1 (accumulation of PAR polymer and decrease in ATP levels) as a possible non-p53 tumor suppression program. However, these cells did not show full signs of either apoptosis or PAR-Thanatos. Molecular analyses attributed such a response to the inability of Mortaparib^Plus to disrupt the AIF–mortalin complexes; hence, AIF did not translocate to the nucleus to induce chromatinolysis and DNA degradation. These data suggested that the cancer cells possessing enriched levels of such complexes may not respond to Mortaparib^Plus. Taken together, we report the multimodal anticancer potential of Mortaparib^Plus that warrants further attention in laboratory and clinical studies.

Mortalin maintains breast cancer stem cells stemness via activation of Wnt/GSK3β/β-catenin signaling pathway

Previous research indicated that mortalin overexpressed in breast cancer and contributed to carcinogenesis. Mortalin was also demonstrated to promote Epithelial-mesenchymal transition (EMT) and was considered as a factor for maintaining the stemness of the cancer stem cells. However, the underlying mechanisms about mortalin maintaining the stemness of breast cancer stem cells (BCSCs) remain unclear. Here, we identified that increased expression of mortalin in breast cancer was associated with poorer overall survival rate. Mortalin was elevated in breast cancer cell lines and BCSC-enriched populations. Additionally, knockdown of mortalin significantly inhibited the cell proliferation, migration and EMT, as well as sphere forming capacity and stemness genes expression. Further study revealed that mortalin promoted EMT and maintained BCSCs stemness via activating the Wnt/GSK3β/β-catenin signaling pathway in vivo and in vitro. Taken together, these findings unveiled the mechanism of mortalin in maintaining and regulating the stemness of BCSCs, and may offer novel therapeutic strategies for breast cancer treatment.

Identification and Characterization of MortaparibPlus-A Novel Triazole Derivative That Targets Mortalin-p53 Interaction and Inhibits Cancer-Cell Proliferation by Wild-Type p53-Dependent and -Independent Mechanisms

p53 has an essential role in suppressing the carcinogenesis process by inducing cell cycle arrest/apoptosis/senescence. Mortalin/GRP75 is a member of the Hsp70 protein family that binds to p53 causing its sequestration in the cell cytoplasm. Hence, p53 cannot translocate to the nucleus to execute its canonical tumour suppression function as a transcription factor. Abrogation of mortalin-p53 interaction and subsequent reactivation of p53's tumour suppression function has been anticipated as a possible approach in developing a novel cancer therapeutic drug candidate. A chemical library was screened in a high-content screening system to identify potential mortalin-p53 interaction disruptors. By four rounds of visual assays for mortalin and p53, we identified a novel synthetic small-molecule triazole derivative (4-[(1E)-2-(2-phenylindol-3-yl)-1-azavinyl]-1,2,4-triazole, henceforth named Mortaparib^Plus). Its activities were validated using multiple bioinformatics and experimental approaches in colorectal cancer cells possessing either wild-type (HCT116) or mutant (DLD-1) p53. Bioinformatics and computational analyses predicted the ability of Mortaparib^Plus to competitively prevent the interaction of mortalin with p53 as it interacted with the p53 binding site of mortalin. Immunoprecipitation analyses demonstrated the abrogation of mortalin-p53 complex formation in Mortaparib^Plus-treated cells that showed growth arrest and apoptosis mediated by activation of p21^WAF1, or BAX and PUMA signalling, respectively. Furthermore, we demonstrate that Mortaparib^Plus-induced cytotoxicity to cancer cells is mediated by multiple mechanisms that included the inhibition of PARP1, up-regulation of p73, and also the down-regulation of mortalin and CARF proteins that play critical roles in carcinogenesis. Mortaparib^Plus is a novel multimodal candidate anticancer drug that warrants further experimental and clinical attention.

Mitochondrial protein import dysfunction: mitochondrial disease, neurodegenerative disease and cancer

The majority of proteins localised to mitochondria are encoded by the nuclear genome, with approximately 1500 proteins imported into mammalian mitochondria. Dysfunction in this fundamental cellular process is linked to a variety of pathologies including neuropathies, cardiovascular disorders, myopathies, neurodegenerative diseases and cancer, demonstrating the importance of mitochondrial protein import machinery for cellular function. Correct import of proteins into mitochondria requires the co-ordinated activity of multimeric protein translocation and sorting machineries located in both the outer and inner mitochondrial membranes, directing the imported proteins to the destined mitochondrial compartment. This dynamic process maintains cellular homeostasis, and its dysregulation significantly affects cellular signalling pathways and metabolism. This review summarises current knowledge of the mammalian mitochondrial import machinery and the pathological consequences of mutation of its components. In addition, we will discuss the role of mitochondrial import in cancer, and our current understanding of the role of mitochondrial import in neurodegenerative diseases including Alzheimer's disease, Huntington's disease and Parkinson's disease.

Mortalin depletion induces MEK/ERK-dependent and ANT/CypD-mediated death in vemurafenib-resistant B-RafV600E melanoma cells

Therapy resistance to a selective B-Raf inhibitor (BRAFi) poses a challenge in treating patients with BRAF-mutant melanomas. Here, we report that RNA interference of mortalin (HSPA9/GRP75), a mitochondrial molecular chaperone often upregulated and mislocalized in melanoma, can effectively induce death of vemurafenib-resistant progenies of human B-Raf^V600E melanoma cell lines, A375 and Colo-829. Mortalin depletion induced death of vemurafenib-resistant cells at similar efficacy as observed in vemurafenib-naïve parental cells. This lethality was correlated with perturbed mitochondrial permeability and was attenuated by knockdown of adenine nucleotide translocase (ANT) and cyclophilin D (CypD), the key regulators of mitochondrial permeability. Chemical inhibition of MEK1/2 and ERK1/2 also suppressed mortalin depletion-induced death and mitochondrial permeability in these cells. These data suggest that mortalin and MEK/ERK regulate an ANT/CypD-associated mitochondrial death mechanism(s) in B-Raf^V600E melanoma cells and that this regulation is conserved even after these cells develop BRAFi resistance. We also show that doxycycline-induced mortalin depletion can effectively suppress the xenografts of vemurafenib-resistant A375 progeny in athymic nude mice. These findings suggest that mortalin has potential as a candidate therapeutic target for BRAFi-resistant BRAF-mutant tumors.

Mitochondria as a Novel Target for Cancer Chemoprevention: Emergence of Mitochondrial-targeting Agents

Cancer chemoprevention is the most effective approach to control cancer in the population. Despite significant progress, chemoprevention has not been widely adopted because agents that are safe tend to be less effective and those that are highly effective tend to be toxic. Thus, there is an urgent need to develop novel and effective chemopreventive agents, such as mitochondria-targeted agents, that can prevent cancer and prolong survival. Mitochondria, the central site for cellular energy production, have important functions in cell survival and death. Several studies have revealed a significant role for mitochondrial metabolism in promoting cancer development and progression, making mitochondria a promising new target for cancer prevention. Conjugating delocalized lipophilic cations, such as triphenylphosphonium cation (TPP+), to compounds of interest is an effective approach for mitochondrial targeting. The hyperpolarized tumor cell membrane and mitochondrial membrane potential allow for selective accumulation of TPP⁺ conjugates in tumor cell mitochondria versus those in normal cells. This could enhance direct killing of precancerous, dysplastic, and tumor cells while minimizing potential toxicities to normal cells.

Identification of Caffeic Acid Phenethyl Ester (CAPE) as a Potent Neurodifferentiating Natural Compound That Improves Cognitive and Physiological Functions in Animal Models of Neurodegenerative Diseases

Cell-based screening of bioactive compounds has served as an important gateway in drug discovery. In the present report, using human neuroblastoma cells and enrolling an extensive three-step screening of 57 phytochemicals, we have identified caffeic acid phenethyl ester (CAPE) as a potent neurodifferentiating natural compound. Analyses of control and CAPE-induced neurodifferentiated cells revealed: (i) modulation of several key proteins (NF200, MAP-2, NeuN, PSD95, Tuj1, GAP43, and GFAP) involved in neurodifferentiation process; and (ii) attenuation of neuronal stemness (HOXD13, WNT3, and Msh-2) and proliferation-promoting (CDC-20, CDK-7, and BubR1) proteins. We anticipated that the neurodifferentiation potential of CAPE may be beneficial for the treatment of neurodegenerative diseases and tested it using the Drosophila model of Alzheimer’s disease (AD) and mice model of amnesia/loss of memory. In both models, CAPE exhibited improved disease symptoms and activation of physiological functions. Remarkably, CAPE-treated mice showed increased levels of neurotrophin-BDNF, neural progenitor marker-Nestin, and differentiation marker-NeuN, both in the cerebral cortex and hippocampus. Taken together, we demonstrate the differentiation-inducing and therapeutic potential of CAPE for neurodegenerative diseases.

Mortalin/HSPA9 targeting selectively induces KRAS tumor cell death by perturbing mitochondrial membrane permeability

The mitochondrial HSP70 chaperone mortalin (HSPA9/GRP75) is often upregulated and mislocalized in MEK/ERK-deregulated tumors. Here, we show that mortalin depletion can selectively induce death of immortalized normal fibroblasts IMR90E1A when combined with K-Ras^G12V expression, but not with wild type K-Ras expression, and that K-Ras^G12V-driven MEK/ERK activity is necessary for this lethality. This cell death was attenuated by knockdown or inhibition of adenine nucleotide translocase (ANT), cyclophilin D (CypD), or mitochondrial Ca²⁺ uniporter (MCU), which implicates a mitochondria-originated death mechanism. Indeed, mortalin depletion increased mitochondrial membrane permeability and induced cell death in KRAS-mutated human pancreatic ductal adenocarcinoma (PDAC) and colon cancer lines, which were attenuated by knockdown or inhibition of ANT, CypD, or MCU, and occurred independently of TP53 and p21^CIP1. Intriguingly, JG-98, an advanced MKT-077 derivative, phenocopied the lethal effects of mortalin depletion in K-Ras^G12V-expressing IMR90E1A and KRAS-mutated tumor cell lines in vitro. Moreover, JG-231, a JG-98 analog with improved microsomal stability effectively suppressed the xenograft of MIA PaCa-2, a K-Ras^G12C-expressing human PDAC line, in athymic nude mice. These data demonstrate that oncogenic KRAS activity sensitizes cells to the effects of mortalin depletion, suggesting that mortalin has potential as a selective therapeutic target for KRAS-mutated tumors.

Molecular Chaperones in Cancer Stem Cells: Determinants of Stemness and Potential Targets for Antitumor Therapy

Cancer stem cells (CSCs) are a great challenge in the fight against cancer because these self-renewing tumorigenic cell fractions are thought to be responsible for metastasis dissemination and cases of tumor recurrence. In comparison with non-stem cancer cells, CSCs are known to be more resistant to chemotherapy, radiotherapy, and immunotherapy. Elucidation of mechanisms and factors that promote the emergence and existence of CSCs and their high resistance to cytotoxic treatments would help to develop effective CSC-targeting therapeutics. The present review is dedicated to the implication of molecular chaperones (protein regulators of polypeptide chain folding) in both the formation/maintenance of the CSC phenotype and cytoprotective machinery allowing CSCs to survive after drug or radiation exposure and evade immune attack. The major cellular chaperones, namely heat shock proteins (HSP90, HSP70, HSP40, HSP27), glucose-regulated proteins (GRP94, GRP78, GRP75), tumor necrosis factor receptor-associated protein 1 (TRAP1), peptidyl-prolyl isomerases, protein disulfide isomerases, calreticulin, and also a transcription heat shock factor 1 (HSF1) initiating HSP gene expression are here considered as determinants of the cancer cell stemness and potential targets for a therapeutic attack on CSCs. Various approaches and agents are discussed that may be used for inhibiting the chaperone-dependent development/manifestations of cancer cell stemness.

Mortalin (HSPA9) facilitates BRAF-mutant tumor cell survival by suppressing ANT3-mediated mitochondrial membrane permeability

Mortalin [also known as heat shock protein family A (HSP70) member 9 (HSPA9) or glucose-regulated protein 75 (GRP75)] is a mitochondrial molecular chaperone that is often up-regulated and mislocalized in tumors with abnormal activation of the kinases MEK and ERK. Here, we found that mortalin depletion was selectively lethal to tumor and immortalized normal cells expressing the mutant kinase B-Raf^V600E or the chimeric protein ΔRaf-1:ER and that MEK-ERK-sensitive regulation of the peptide-binding domain in mortalin was critical to cell survival or death. Proteomics screening identified adenine nucleotide translocase 3 (ANT3) as a previously unknown mortalin substrate and cell survival/death effector. Mechanistically, increased MEK-ERK signaling activity and mortalin function converged opposingly on the regulation of mitochondrial permeability. Specifically, whereas MEK-ERK activity increased mitochondrial permeability by promoting the interaction between ANT3 and the peptidyl-prolyl isomerase cyclophilin D (CypD), mortalin decreased mitochondrial permeability by inhibiting this interaction. Hence, mortalin depletion increased mitochondrial permeability in MEK-ERK-deregulated cells to an extent that triggered cell death. HSP70 inhibitor derivatives that effectively inhibited mortalin suppressed the proliferation of B-Raf^V600E tumor cells in culture and in vivo, including their B-Raf inhibitor-resistant progenies. These findings suggest that targeting mortalin has potential as a selective therapeutic strategy in B-Raf-mutant or MEK-ERK-driven tumors.

Evolving paradigms on the interplay of mitochondrial Hsp70 chaperone system in cell survival and senescence

The role of mitochondria within a cell has grown beyond being the prime source of cellular energy to one of the major signaling platforms. Recent evidence provides several insights into the crucial roles of mitochondrial chaperones in regulating the organellar response to external triggers. The mitochondrial Hsp70 (mtHsp70/Mortalin/Grp75) chaperone system plays a critical role in the maintenance of proteostasis balance in the organelle. Defects in mtHsp70 network result in attenuated protein transport and misfolding of polypeptides leading to mitochondrial dysfunction. The functions of Hsp70 are primarily governed by J-protein cochaperones. Although human mitochondria possess a single Hsp70, its multifunctionality is characterized by the presence of multiple specific J-proteins. Several studies have shown a potential association of Hsp70 and J-proteins with diverse pathological states that are not limited to their canonical role as chaperones. The role of mitochondrial Hsp70 and its co-chaperones in disease pathogenesis has not been critically reviewed in recent years. We evaluated some of the cellular interfaces where Hsp70 machinery associated with pathophysiological conditions, particularly in context of tumorigenesis and neurodegeneration. The mitochondrial Hsp70 machinery shows a variable localization and integrates multiple components of the cellular processes with varied phenotypic consequences. Although Hsp70 and J-proteins function synergistically in proteins folding, their precise involvement in pathological conditions is mainly idiosyncratic. This machinery is associated with a heterogeneous set of molecules during the progression of a disorder. However, the precise binding to the substrate for a specific physiological response under a disease subtype is still an undocumented area of analysis.

Heat Shock Proteins: Agents of Cancer Development and Therapeutic Targets in Anti-Cancer Therapy

Heat shock proteins (HSPs) constitute a large family of molecular chaperones classified by their molecular weights, and they include HSP27, HSP40, HSP60, HSP70, and HSP90. HSPs function in diverse physiological and protective processes to assist in maintaining cellular homeostasis. In particular, HSPs participate in protein folding and maturation processes under diverse stressors such as heat shock, hypoxia, and degradation. Notably, HSPs also play essential roles across cancers as they are implicated in a variety of cancer-related activities such as cell proliferation, metastasis, and anti-cancer drug resistance. In this review, we comprehensively discuss the functions of HSPs in association with cancer initiation, progression, and metastasis and anti-cancer therapy resistance. Moreover, the potential utilization of HSPs to enhance the effects of chemo-, radio-, and immunotherapy is explored. Taken together, HSPs have multiple clinical usages as biomarkers for cancer diagnosis and prognosis as well as the potential therapeutic targets for anti-cancer treatment.

Mortaparib, a novel dual inhibitor of mortalin and PARP1, is a potential drug candidate for ovarian and cervical cancers

Background

Mortalin is enriched in a large variety of cancers and has been shown to contribute to proliferation and migration of cancer cells in multiple ways. It has been shown to bind to p53 protein in cell cytoplasm and nucleus causing inactivation of its tumor suppressor activity in cancer cells. Several other activities of mortalin including mitochondrial biogenesis, ATP production, chaperoning, anti-apoptosis contribute to pro-proliferative and migration characteristics of cancer cells. Mortalin-compromised cancer cells have been shown to undergo apoptosis in in vitro and in vivo implying that it could be a potential target for cancer therapy.

Methods

We implemented a screening of a chemical library for compounds with potential to abrogate cancer cell specific mortalin-p53 interactions, and identified a new compound (named it as Mortaparib) that caused nuclear enrichment of p53 and shift in mortalin from perinuclear (typical of cancer cells) to pancytoplasmic (typical of normal cells). Biochemical and molecular assays were used to demonstrate the effect of Mortaparib on mortalin, p53 and PARP1 activities.

Results

Molecular homology search revealed that Mortaparib is a novel compound that showed strong cytotoxicity to ovarian, cervical and breast cancer cells. Bioinformatics analysis revealed that although Mortaparib could interact with mortalin, its binding with p53 interaction site was not stable. Instead, it caused transcriptional repression of mortalin leading to activation of p53 and growth arrest/apoptosis of cancer cells. By extensive computational and experimental analyses, we demonstrate that Mortaparib is a dual inhibitor of mortalin and PARP1. It targets mortalin, PARP1 and mortalin-PARP1 interactions leading to inactivation of PARP1 that triggers growth arrest/apoptosis signaling. Consistent with the role of mortalin and PARP1 in cancer cell migration, metastasis and angiogenesis, Mortaparib-treated cells showed inhibition of these phenotypes. In vivo tumor suppression assays showed that Mortaparib is a potent tumor suppressor small molecule and awaits clinical trials.

Conclusion

These findings report (i) the discovery of Mortaparib as a first dual inhibitor of mortalin and PARP1 (both frequently enriched in cancers), (ii) its molecular mechanism of action, and (iii) in vitro and in vivo tumor suppressor activity that emphasize its potential as an anticancer drug.

Novel and Alternative Targets Against Breast Cancer Stemness to Combat Chemoresistance

Breast cancer stem cells (BCSCs) play a vital role in tumor progression and metastasis. They are heterogeneous and inherently radio- and chemoresistant. They have the ability to self-renew and differentiate into non-BCSCs. These determinants of BCSCs including the plasticity between the mesenchymal and epithelial phenotypes often leads to minimal residual disease (MRD), tumor relapse, and therapy failure. By studying the resistance mechanisms in BCSCs, a combinatorial therapy can be formulated to co-target BCSCs and bulk tumor cells. This review addresses breast cancer stemness and molecular underpinnings of how the cancer stemness can lead to pharmacological resistance. This might occur through rewiring of signaling pathways and modulated expression of various targets that support survival and self-renewal, clonogenicity, and multi-lineage differentiation into heterogeneous bulk tumor cells following chemotherapy. We explore emerging novel and alternative molecular targets against BC stemness and chemoresistance involving survival, drug efflux, metabolism, proliferation, cell migration, invasion, and metastasis. Strategic targeting of such vulnerabilities in BCSCs may overcome the chemoresistance and increase the longevity of the metastatic breast cancer patients.

The assembly of succinate dehydrogenase: a key enzyme in bioenergetics

Succinate dehydrogenase (SDH) also known as complex II or succinate:quinone oxidoreductase is an enzyme involved in both oxidative phosphorylation and tricarboxylic acid cycle; the processes that generate energy. SDH is a multi-subunit enzyme which requires a series of proteins for its proper assembly at several steps. This enzyme has medical significance as there is a broad range of human diseases from cancers to neurodegeneration related to SDH malfunction. Some of these disorders have recently been linked to defective assembly factors, reinvigorating further research in this area. Apart from that this enzyme has agricultural importance as many fungicides have been/will be designed targeting specifically this enzyme in plant fungal pathogens. In addition, we speculate it might be possible to design novel fungicides specifically targeting fungal assembly factors. Considering the medical and agricultural implications of SDH, the aim of this review is an overview of the SDH assembly factors and critical analysis of controversial issues around them.

Impact of Heat Shock Protein 90 Inhibition on the Proteomic Profile of Lung Adenocarcinoma as Measured by Two-Dimensional Electrophoresis Coupled with Mass Spectrometry

Heat shock protein 90 (HSP90) is an important chaperone in lung adenocarcinoma, with relevant protein drivers such as EGFR (epidermal growth factor receptor) and EML4-ALK (echinoderm microtubule-associated protein-like protein4 fused to anaplastic lymphoma kinase) depending on it for their correct function, therefore HSP90 inhibitors show promise as potential treatments for lung adenocarcinoma. To study responses to its inhibition, HSP90 was pharmacologically interrupted by geldanamycin and resorcinol derivatives or with combined inhibition of HSP90 plus HSP70 in lung adenocarcinoma cell lines. Two-dimensional electrophoresis was performed to identify proteomic profiles associated with inhibition which will help to understand the biological basis for the responses. HSP90 inhibition resulted in altered protein profiles that differed according the treatment condition studied. Results revealed 254 differentially expressed proteins after treatments, among which, eukaryotic translation initiation factor3 subunit I (eIF3i) and citrate synthase demonstrated their potential role as response biomarkers. The differentially expressed proteins also enabled signalling pathways involved in responses to be identified; these included apoptosis, serine-glycine biosynthesis and tricarboxylic acid cycle. The proteomic profiles identified here contribute to an improved understanding of HSP90 inhibition and open possibilities for the detection of potential response biomarkers which will be essential to maximize treatment efficacy in lung adenocarcinoma.

Elevated Mortalin correlates with poor outcome in hepatocellular carcinoma

Although several lines of evidence existed suggesting that Mortalin was linked with survival in malignant tumors; it has been barely described regarding the prognostic involvement of its expression in hepatocellular carcinoma (HCC). Herein, to understand the prognostic meaning of Mortalin expression, Immunohistochemistry was undertaken to observe the immunohistochemical characteristics of Mortalin on HCC tissue microarray consisting of 90 cases of HCC and its paired normal control dots, followed by detailed statistical analysis with the accompanying clinicopathological variables available, including gender, age, tumor size, differentiation, cirrhosis, vascular invasion, clinical stage, T classification and intrahepatic metastases. Meanwhile, Kaplan-Meier survival curve was plotted to analyze the prognostic difference for patients with high and low expression of Mortalin. It was exhibited that Mortalin was over-expressed in HCC tissues relative to paired normal control and elevated Mortalin significantly correlated with vascular invasion, clinical stage and intrahepatic metastasis. Kaplan-Meier survival analysis revealed that Mortalin was remarkably associated with overall survival and disease-free survival. Multivariate Cox regression analysis showed that expression of Mortalin was an independent prognostic factor in HCC. Collectively, the data we provided here support the prognostic prediction value of Mortalin in HCC.

2- and N6-functionalized adenosine-5'-diphosphate analogs for the inhibition of mortalin

Our early efforts to find a covalent inhibitor of mortalin, a member of the 70 kD heat shock protein (Hsp70) family, led us to solve the structure of the mortalin nucleotide-binding domain (NBD) in complex with N6-propargyladenosine-5'-diphosphate. The acquired structure emphasizes the ability of the nucleotide-binding pocket to accommodate modified ADP compounds. A library of ADP analogs modified at either the 2- or N6-positions of adenosine was screened against the mortalin-NBD. Competitive inhibition and binding assays of the analogs demonstrate that modifications at the 2- or N6-positions have potential to bind and inhibit mortalin uniquely compared to other Hsp70 homologs, and that modifications at the 2-position confer the greatest selectivity in binding and inhibition of the mortalin-NBD.

Marine Carotenoid Fucoxanthin Possesses Anti-Metastasis Activity: Molecular Evidence

Fucoxanthin is commonly found in marine organisms; however, to date, it has been one of the scarcely explored natural compounds. We investigated its activities in human cancer cell culture-based viability, migration, and molecular assays, and found that it possesses strong anticancer and anti-metastatic activities that work irrespective of the p53 status of cancer cells. In our experiments, fucoxanthin caused the transcriptional suppression of mortalin. Cell phenotype-driven molecular analyses on control and treated cells demonstrated that fucoxanthin caused a decrease in hallmark proteins associated with cell proliferation, survival, and the metastatic spread of cancer cells at doses that were relatively safe to the normal cells. The data suggested that the cancer therapy regimen may benefit from the recruitment of fucoxanthin; hence, it warrants further attention for basic mechanistic studies as well as drug development.

Interorganellar calcium signaling in the regulation of cell metabolism: A cancer perspective

Organelles were originally considered to be individual cellular compartments with a defined organization and function. However, recent studies revealed that organelles deeply communicate within each other via Ca²⁺ exchange. This communication, mediated by specialized membrane regions in close apposition between two organelles, regulate cellular functions, including metabolism and cell fate decisions. Advances in microscopy techniques, molecular biology and biochemistry have increased our understanding of these interorganelle platforms. Research findings suggest that interorganellar Ca²⁺ signaling, which is altered in cancer, influences tumorigenesis and tumor progression by controlling cell death programs and metabolism. Here, we summarize the available data on the existence and composition of interorganelle platforms connecting the endoplasmic reticulum with mitochondria, the plasma membrane, or endolysosomes. Finally, we provide a timely overview of the potential function of interorganellar Ca²⁺ signaling in maintaining cellular homeostasis.

Heat Shock Proteins (HSPs): A Novel Target for Cancer Metastasis Prevention

Background:

Heat shock proteins (HSPs) are predominant molecular chaperones which are actively involved in the protein folding; which is essential in protecting the structure and functioning of proteins during various stress conditions. Though HSPs have important physiological roles, they have been well known for their roles in various pathogenic conditions such as carcinogenesis; however, limited literature has consolidated its potential as an anti-metastatic drug target.

Objectives:

The present review outlines the role of different HSPs on cancer progression and metastasis; possible role of HSP inhibitors as anti-neoplastic agents is also discussed.

Methods:

The data were collected from PubMed/Medline and other reputed journal databases. The literature that was too old and had no significant role to the review was then omitted.

Results:

Despite their strong physiological functions, HSPs are considered as good markers for cancer prognosis and diagnosis. They have control over survival, proliferation and progression events of cancer including drug resistance, metastasis, and angiogenesis. Since, neoplastic cells are more dependent on HSPs for survival and proliferation, the selectivity and specificity of HSP-targeted cancer drugs remain high. This has made various HSPs potential clinical and experimental targets for cancer prevention. An array of HSP inhibitors has been in trials and many others are in experimental conditions as anticancer and anti-metastatic agents. Several natural products are also being investigated for their efficacy for anticancer and anti-metastatic agents by modulating HSPs.

Conclusion:

Apart from their role as an anticancer drug target, HSPs have shown to be promising targets for the prevention of cancer progression. Extensive studies are required for the use of these molecules as anti-metastatic agents. Further studies in this line may yield specific and effective antimetastatic agents.

Role of C5b-9 and RGC-32 in Cancer

The complement system represents an effective arsenal of innate immunity as well as an interface between innate and adaptive immunity. Activation of the complement system culminates with the assembly of the C5b-9 terminal complement complex on cell membranes, inducing target cell lysis. Translation of this sequence of events into a malignant setting has traditionally afforded C5b-9 a strict antitumoral role, in synergy with antibody-dependent tumor cytolysis. However, in recent decades, a plethora of evidence has revised this view, highlighting the tumor-promoting properties of C5b-9. Sublytic C5b-9 induces cell cycle progression by activating signal transduction pathways (e.g., Gi protein/ phosphatidylinositol 3-kinase (PI3K)/Akt kinase and Ras/Raf1/ERK1) and modulating the activation of cancer-related transcription factors, while shielding malignant cells from apoptosis. C5b-9 also induces Response Gene to Complement (RGC)-32, a gene that contributes to cell cycle regulation by activating the Akt and CDC2 kinases. RGC-32 is expressed by tumor cells and plays a dual role in cancer, functioning as either a tumor promoter by endorsing malignancy initiation, progression, invasion, metastasis, and angiogenesis, or as a tumor suppressor. In this review, we present recent data describing the versatile, multifaceted roles of C5b-9 and its effector, RGC-32, in cancer.

Mortalin is a distinct bio-marker and prognostic factor in serous ovarian carcinoma

This study focused on mortalin expression and its relevance to the prognosis in serous ovarian carcinoma, mortalin modulated cell malignant proliferation and EMT progression via Wnt/β-Catenin signaling pathway. In this study, data obtained from Oncomine database, Cancer Cell Line Encyclopedia (CCLE) analysis and Immunohistochemical (IHC) staining was used to assess the expression of mortalin in serous ovarian carcinoma. The prognostic value of mortalin was analyzed using Meier plotter database and Kaplan-Meier. MTT (3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2-H-tetrazolium bromide) assay, immunofluorescence (IF) staining, and colony formation assay were used to detect cell reproductive capacity. SK-OV-3 cell motility and epithelial-mesenchymal transition (EMT) were measured by wound-healing, migration and western-blot assays. Data from Oncomine showed that mortalin was highly expressed in serous ovarian carcinomas compared with corresponding normal controls. Similar results were found in CCLE analysis and in clinical specimens. High mortalin expression was associated with high histological grade and worse overall survival (OS) rate. The results of MTT analyses, IF staining, and colony formation assay indicated that MKT-077 (1-Ethyl-2-[[3-ethyl-5-(3-methyl-2(3H)-benzothiazolylidene)-4-oxo-2-thiazolidinylidene] methyl]-pyridinium chloride) suppressed the viability of SK-OV-3 cells. Besides, mortalin suppression restrained cell EMT progression by Wnt/β-Catenin signaling pathway. Taken together, mortalin is over-expressed in serous ovarian carcinoma. High mortalin expression could be a candidate for the prognostic indicator and a biomarker in serous ovarian carcinoma.

Novel and Alternative Targets Against Breast Cancer Stemness to Combat Chemoresistance

Breast cancer stem cells (BCSCs) play a vital role in tumor progression and metastasis. They are heterogeneous and inherently radio- and chemoresistant. They have the ability to self-renew and differentiate into non-BCSCs. These determinants of BCSCs including the plasticity between the mesenchymal and epithelial phenotypes often leads to minimal residual disease (MRD), tumor relapse, and therapy failure. By studying the resistance mechanisms in BCSCs, a combinatorial therapy can be formulated to co-target BCSCs and bulk tumor cells. This review addresses breast cancer stemness and molecular underpinnings of how the cancer stemness can lead to pharmacological resistance. This might occur through rewiring of signaling pathways and modulated expression of various targets that support survival and self-renewal, clonogenicity, and multi-lineage differentiation into heterogeneous bulk tumor cells following chemotherapy. We explore emerging novel and alternative molecular targets against BC stemness and chemoresistance involving survival, drug efflux, metabolism, proliferation, cell migration, invasion, and metastasis. Strategic targeting of such vulnerabilities in BCSCs may overcome the chemoresistance and increase the longevity of the metastatic breast cancer patients.

Exploration of Benzothiazole Rhodacyanines as Allosteric Inhibitors of Protein-Protein Interactions with Heat Shock Protein 70 (Hsp70)

Cancer cells rely on the chaperone heat shock protein 70 (Hsp70) for survival and proliferation. Recently, benzothiazole rhodacyanines have been shown to bind an allosteric site on Hsp70, interrupting its binding to nucleotide-exchange factors (NEFs) and promoting cell death in breast cancer cell lines. However, proof-of-concept molecules, such as JG-98, have relatively modest potency (EC₅₀ ≈ 0.7-0.4 μM) and are rapidly metabolized in animals. Here, we explored this chemical series through structure- and property-based design of ∼300 analogs, showing that the most potent had >10-fold improved EC₅₀ values (∼0.05 to 0.03 μM) against two breast cancer cells. Biomarkers and whole genome CRISPRi screens confirmed members of the Hsp70 family as cellular targets. On the basis of these results, JG-231 was found to reduce tumor burden in an MDA-MB-231 xenograft model (4 mg/kg, ip). Together, these studies support the hypothesis that Hsp70 may be a promising target for anticancer therapeutics.