Tyrosine phosphorylation of HSC70 and its interaction with RFC mediates methotrexate resistance in murine L1210 leukemia cells

Heat Shock Proteins, a Double-Edged Sword: Significance in Cancer Progression, Chemotherapy Resistance and Novel Therapeutic Perspectives

Heat shock proteins (Hsps) are involved in one of the adaptive mechanisms protecting cells against environmental and metabolic stress. Moreover, the large role of these proteins in the carcinogenesis process, as well as in chemoresistance, was noticed. This review aims to draw attention to the possibilities of using Hsps in developing new cancer therapy methods, as well as to indicate directions for future research on this topic. In order to discuss this matter, a thorough review of the latest scientific literature was carried out, taking into account the importance of selected proteins from the Hsp family, including Hsp27, Hsp40, Hsp60, Hsp70, Hsp90 and Hsp110. One of the more characteristic features of all Hsps is that they play a multifaceted role in cancer progression, which makes them an obvious target for modern anticancer therapy. Some researchers emphasize the importance of directly inhibiting the action of these proteins. In turn, others point to their possible use in the design of cancer vaccines, which would work by inducing an immune response in various types of cancer. Due to these possibilities, it is believed that the use of Hsps may contribute to the progress of oncoimmunology, and thus help in the development of modern anticancer therapies, which would be characterized by higher effectiveness and lower toxicity to the patients.

Association of anti-HSC70 autoantibodies with cutaneous ulceration and severe disease in juvenile dermatomyositis

OBJECTIVES

JDM is an inflammatory myopathy characterized by prominent vasculopathy. AECAs are frequently detected in inflammatory and autoimmune diseases. We sought to determine whether AECAs correlate with clinical features of JDM, and thus serve as biomarkers to guide therapy or predict outcome.

METHODS

Plasma samples from 63 patients with JDM, 49 patients with polyarticular JIA and 40 juvenile healthy controls were used to detect anti-heat shock cognate 71 kDa protein (HSC70) autoantibodies, a newly identified AECA, in ELISA assays. Clinical features were compared between JDM patients with and without anti-HSC70 autoantibodies.

RESULTS

Anti-HSC70 autoantibodies were detected in 35% of patients with JDM, in 0% of patients with JIA (P < 0.0001) and in 0% of healthy donors (P < 0.0001). Both the presence of cutaneous ulcers (59% vs 17%, P < 0.002) and the use of wheelchairs and/or assistive devices (64% vs 27%, P < 0.007) were strongly associated with anti-HSC70 autoantibodies in JDM. High scores on the severity of myositis damage measures at the time of measurement of anti-HSC70 autoantibodies and an increased number of hospitalizations were also associated with anti-HSC70 autoantibodies. Intravenous immunoglobulin therapy was used more often in anti-HSC70 autoantibody-positive patients.

CONCLUSION

Anti-HCS70 autoantibodies are detected frequently in children with JDM and are novel myositis-associated autoantibodies correlating with disease severity.

The Pentose Phosphate Pathway in Cancer: Regulation and Therapeutic Opportunities

BACKGROUND

Tumorigenesis is associated with deregulation of nutritional requirements, intermediary metabolites production, and microenvironment interactions. Unlike their normal cell counterparts, tumor cells rely on aerobic glycolysis, through the Warburg effect.

SUMMARY

The pentose phosphate pathway (PPP) is a major glucose metabolic shunt that is upregulated in cancer cells. The PPP comprises an oxidative and a nonoxidative phase and is essential for nucleotide synthesis of rapidly dividing cells. The PPP also generates nicotinamide adenine dinucleotide phosphate, which is required for reductive metabolism and to counteract oxidative stress in tumor cells. This article reviews the regulation of the PPP and discusses inhibitors that target its main pathways. Key Message: Exploiting the metabolic vulnerability of the PPP offers potential novel therapeutic opportunities and improves patients' response to cancer therapy.

Quantitative Tyrosine Phosphoproteomic Analysis of Resistance to Radiotherapy in Nasopharyngeal Carcinoma Cells

Background

Radioresistance poses a major challenge in nasopharyngeal carcinoma (NPC) treatment. Protein tyrosine phosphorylation has emerged as a key device in the control of resistance to therapy in cancer cells.

Methods

Using tandem mass tag (TMT) labeling and phospho-antibody affinity enrichment followed by high-resolution LC-MS/MS analysis, quantitative tyrosine phosphorylome analysis was performed in CNE2 (parental) and its radioresistant subline CNE2-IR.

Results

Altogether, 233 tyrosine phosphorylation sites in 179 protein groups were identified, among which 179 sites in 140 proteins were quantified. Among the quantified proteins, 38 tyrosine phosphorylation proteins are up-regulated and 18 tyrosine phosphorylation proteins are down-regulated in CNE2-IR vs CNE2. Increased tyrosine phosphorylation in multiple receptor/protein tyrosine kinases (EPHA2, EGFR, IGF1R, ABL1 and LYN) was identified in CNE2-IR vs CNE2 cells. Intensive bioinformatic analyses revealed robust activation of multiple biological processes/pathways including E-cadherin stabilization, cell-cell adhesion, and cell junction organization in radioresistant CNE2-IR cells. Specifically, we observed that the CNE2 cells incubated with EphrinA1-Fc exhibited higher EPHA2 Y772 phosphorylation and lower E-cadherin expression, as compared with PBS control. Furthermore, an ATP-competitive EPHA2 RTK inhibitor (ALW-II-41-27, ALW) reduced EPHA2 Y772 phosphorylation and increased the expression of E-cadherin in CNE2-IR cells. Colony formation analysis showed that EFNA1 (EFNA1 is the ligand of EPHA2) treatment in CNE2 significantly promoted colony formation after 6Gy irradiation; while incubation with EPHA2 inhibitor ALW-II-41-27 in CNE2-IR cells impaired colony formation after irradiation, as compared with solvent control (DMSO).

Conclusion

In conclusion, phosphoproteomic approach allowed us to link tyrosine kinases signaling with radioresistance in NPC. Further studies are necessary to delineate the molecular function of EPHA2/E-cadherin signaling in radioresistant NPC and to explore rational combination therapy and its underlying mechanism.

Post-translational modifications of Hsp70 family proteins: Expanding the chaperone code

Cells must be able to cope with the challenge of folding newly synthesized proteins and refolding those that have become misfolded in the context of a crowded cytosol. One such coping mechanism that has appeared during evolution is the expression of well-conserved molecular chaperones, such as those that are part of the heat shock protein 70 (Hsp70) family of proteins that bind and fold a large proportion of the proteome. Although Hsp70 family chaperones have been extensively examined for the last 50 years, most studies have focused on regulation of Hsp70 activities by altered transcription, co-chaperone "helper" proteins, and ATP binding and hydrolysis. The rise of modern proteomics has uncovered a vast array of post-translational modifications (PTMs) on Hsp70 family proteins that include phosphorylation, acetylation, ubiquitination, AMPylation, and ADP-ribosylation. Similarly to the pattern of histone modifications, the histone code, this complex pattern of chaperone PTMs is now known as the "chaperone code." In this review, we discuss the history of the Hsp70 chaperone code, its currently understood regulation and functions, and thoughts on what the future of research into the chaperone code may entail.

Identification of GdRFC1 as a novel regulator of telomerase in Giardia duodenalis

Telomerase plays a crucial role in ageing and tumourigenesis. However, the regulatory network of its activity is complicated and not fully understood. In the present study, a yeast two-hybrid screen identified a homologue of human replication factor C subunit 1 (RFC1) as a novel interacting protein of Giardia duodenalis GdTRBD (Giardia duodenalis telomerase ribonucleoprotein complex RNA binding domain GdTRBD). This interaction was further verified via GST pull-down in vitro and co-immunoprecipitation (Co-IP) and bimolecular fluorescence complementation (BiFC) in vivo. We also found that GdRFC1 (Giardia duodenalis replication factor C subunit 1) only interacted with GdTRBD in one nucleus in Giardia duodenalis via a proximity ligation assay (PLA). We reasoned that the two nuclei might have significant heterogeneity in their functional activities during the trophozoite stage and that the two molecules might be involved in other unidentified functions in addition to telomerase activity. In addition, knockdown of GdRFC1 decreased telomerase activity. Collectively, our results indicate that GdRFC1 is a novel binding partner and positive regulator of telomerase in Giardia duodenalis.

DNLC: differential network local consistency analysis

BACKGROUND

The biological network is highly dynamic. Functional relations between genes can be activated or deactivated depending on the biological conditions. On the genome-scale network, subnetworks that gain or lose local expression consistency may shed light on the regulatory mechanisms related to the changing biological conditions, such as disease status or tissue developmental stages.

RESULTS

In this study, we develop a new method to select genes and modules on the existing biological network, in which local expression consistency changes significantly between clinical conditions. The method is called DNLC: Differential Network Local Consistency. In simulations, our algorithm detected artificially created local consistency changes effectively. We applied the method on two publicly available datasets, and the method detected novel genes and network modules that were biologically plausible.

CONCLUSIONS

The new method is effective in finding modules in which the gene expression consistency change between clinical conditions. It is a useful tool that complements traditional differential expression analyses to make discoveries from gene expression data. The R package is available at https://cran.r-project.org/web/packages/DNLC.

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.

Selective Autophagy Regulates Cell Cycle in Cancer Therapy

Aberrant function of cell cycle regulators results in uncontrolled cell proliferation, making them attractive therapeutic targets in cancer treatment. Indeed, survival of many cancers exclusively relies on these proteins, and several specific inhibitors are in clinical use. Although the ubiquitin-proteasome system is responsible for the periodic quality control of cell cycle proteins during cell cycle progression, increasing evidence clearly demonstrates the intimate interaction between cell cycle regulation and selective autophagy, important homeostasis maintenance machinery. However, these studies have often led to divergent rather than unifying explanations due to complexity of the autophagy signaling network, the inconsistent functions between general autophagy and selective autophagy, and the different characteristics of autophagic substrates. In this review, we highlight current data illustrating the contradictory and important role of cell cycle proteins in regulating autophagy. We also focus on how selective autophagy acts as a central mechanism to maintain orderly DNA repair and genome integrity by degrading specific cell cycle proteins, regulating cell division, and promoting DNA damage repair. We further discuss the ways in which selective autophagy may impact the cell cycle regulators, since failure to appropriately remove these can interfere with cell death-related processes, including senescence and autophagy-related cell death. Imbalanced cell proliferation is typically utilized by cancer cells to acquire resistance. Finally, we discuss the possibility of a potent anticancer therapeutic strategy that targets selective autophagy or autophagy and cell cycle together.

Genistein suppresses aerobic glycolysis and induces hepatocellular carcinoma cell death

Background:

Genistein is a natural isoflavone with many health benefits, including antitumour effects. Increased hypoxia-inducible factor 1 α (HIF-1α) levels and glycolysis in tumour cells are associated with an increased risk of mortality, cancer progression, and resistance to therapy. However, the effect of genistein on HIF-1α and glycolysis in hepatocellular carcinoma (HCC) is still unclear.

Methods:

Cell viability, apoptosis rate, lactate production, and glucose uptake were measured in HCC cell lines with genistein incubation. Lentivirus-expressed glucose transporter 1 (GLUT1) or/and hexokinase 2 (HK2) and siRNA of HIF-1α were used to test the direct target of genistein. Subcutaneous xenograft mouse models were used to measure in vivo efficacy of genistein and its combination with sorafenib.

Results:

Genistein inhibited aerobic glycolysis and induced mitochondrial apoptosis in HCC cells. Neither inhibitors nor overexpression of HK2 or GLUTs enhance or alleviate this effect. Although stabiliser of HIF-1α reversed the effect of genistein, genistein no longer has effects on HIF-1α siRNA knockdown HCC cells. In addition, genistein enhanced the antitumour effect of sorafenib in sorafenib-resistant HCC cells and HCC-bearing mice.

Conclusions:

Genistein sensitised aerobic glycolytic HCC cells to apoptosis by directly downregulating HIF-1α, therefore inactivating GLUT1 and HK2 to suppress aerobic glycolysis. The inhibitory effect of genistein on tumour cell growth and glycolysis may help identify effective treatments for HCC patients at advanced stages.

Heat Shock Proteins and Cancer

Heat shock proteins (HSPs) constitute a large family of proteins involved in protein folding and maturation whose expression is induced by heat shock or other stressors. The major groups are classified based on their molecular weights and include HSP27, HSP40, HSP60, HSP70, HSP90, and large HSPs. HSPs play a significant role in cellular proliferation, differentiation, and carcinogenesis. In this article we comprehensively review the roles of major HSPs in cancer biology and pharmacology. HSPs are thought to play significant roles in the molecular mechanisms leading to cancer development and metastasis. HSPs may also have potential clinical uses as biomarkers for cancer diagnosis, for assessing disease progression, or as therapeutic targets for cancer therapy.

Doxorubicin induces apoptosis by targeting Madcam1 and AKT and inhibiting protein translation initiation in hepatocellular carcinoma cells

Doxorubicin (Doxo) is one of the most widely used chemotherapeutic drugs for patients with hepatocellular carcinoma (HCC). Doxo is a DNA intercalating drug that inhibits topoisomerase II. Thereby Doxo has the ability to block DNA replication and induce apoptosis. However, the other targets and mechanisms through which Doxo induces apoptosis to treat HCC still remain unknown. Here, we identified Mucosal vascular addressin cell adhesion molecule 1 (Madcam1) as a potential Doxo target because Madcam1 overexpression suppressed, while Madcam1 depletion stimulated Doxo-induced apoptosis. Furthermore, we first revealed that Doxo can induce apoptosis by blocking protein translation initiation. In contrast, Madcam1 activated protein translation through an opposite mechanism. We also found de-phosphorylation of AKT may be an important pro-apoptotic event that is triggered by Doxo-induced Madcam1 down-regulation. Finally, we revealed that Madcam1 promoted increased AKT phosphorylation, which is essential for maintaining the sensitivity of HCC cells to Doxo treatment. Taken together, we uncovered a potential mechanism for Doxo-induced apoptosis in HCC treatment through targeting Madcam1 and AKT and blocking protein translation initiation.