Hsc70 contributes to cancer cell survival by preventing Rab1A degradation under stress conditions

Pristimerin Promotes Ubiquitination of HSPA8 and Activates the VAV1/ERK Pathway to Suppress TNBC Proliferation

Triple-negative breast cancer (TNBC) is a subtype of breast cancer with a poor prognosis. The natural compound pristimerin has shown promising anti-tumor effect. Here, it is found that pristimerin significantly triggered the activation of autophagy initiation and induced apoptosis in TNBC. Mechanistically, RNA sequencing revealed that pristimerin activated mitogen-activated protein kinase/extracelluar regulated protein kinases (MAPK/ERK) pathway. Drug affinity responsive target stability and mass spectrometry techniques are employed to confirm the direct binding target of pristimerin. Heat shock protein family A member 8 (HSPA8) is identified and verified by cellular thermal shift assays and surface plasmon resonance assays. The further results suggested that pristimerin promoted the ubiquitination and degradation of HSPA8, leading to a decrease in the degradation of Vac Guanine Nucleotide Exchange Factor 1 (VAV1), a downstream client protein of HSPA8 which plays a crucial role in activating the ERK pathway. Importantly, knockdown of HSPA8 or VAV1 significantly impaired the anticancer activity of pristimerin on TNBC cells. Additionally, pristimerin significantly inhibited the migration and invasion of TNBC cells and enhanced the sensitivity of TNBC cells to doxorubicin. Collectively, this study provides the initial evidence that pristimerin directly targets HSPA8 to activate the VAV1/ERK pathway, thereby promoting cell autophagy and apoptosis.

C118P Suppresses Gastric Cancer Growth via Promoting Autophagy-Lysosomal Degradation of RAB1A

Background/Objectives: Gastric cancer (GC) is the leading cause of cancer-related deaths worldwide. C118P, a microtubule inhibitor with anti-angiogenic and vascular-disrupting activities, was proven to be cytotoxic to various cancer cell lines. This study aimed to explore the anti-tumor effect of C118P against gastric cancer and identify its potential target. Methods: The MTT assay, colony formation assay, and EdU incorporation assay were used to evaluate the effect of C118P on GC cell proliferation. Cell cycle and cell apoptosis were measured using flow cytometry. Molecular docking, a microscale thermophoresis (MST) analysis, and the cellular thermal shift assay (CETSA) were used to investigate the binding of C118P to RAB1A. Autophagy-related effects were evaluated by using the MDC staining assay, immunofluorescence assay, and immunoblotting assay. The SGC-7901 cell line xenograft mouse model was used to confirm the anti-tumor efficacy of C118P. Results: C118P dramatically inhibited proliferation, induced G2/M cell cycle arrest, and triggered apoptosis in GC cell lines HGC-27 and SGC-7901. Mechanistically, C118P was demonstrated to bind with RAB1A and reduce the RAB1A protein level, accompanied by the inhibition of mTORC1 signaling. Moreover, C118P induced autophagosome formation and promoted RAB1A protein degradation in an autophagy-lysosomal-dependent manner. The in vivo study verified that C118P inhibits GC growth by inhibiting the RAB1A-mTOR axis. Conclusions: Our findings suggested that C118P inhibits GC growth by promoting the autophagy-lysosomal-dependent degradation of RAB1A and modulating mTOR C1 signaling. C118P shows potential as being a small molecule drug effective in the treatment of gastric cancer via targeting RAB1A.

Human Hsp70 Substrate-Binding Domains Recognize Distinct Client Proteins

The 13 Hsp70 proteins in humans act on unique sets of substrates with diversity often being attributed to J-domain-containing protein (Hsp40 or JDP) cofactors. We were therefore surprised to find drastically different binding affinities for Hsp70-peptide substrates, leading us to probe substrate specificity among the 8 canonical Hsp70s from humans. We used peptide arrays to characterize Hsp70 binding and then mined these data using machine learning to develop an algorithm for isoform-specific prediction of Hsp70 binding sequences. The results of this algorithm revealed recognition patterns not predicted based on local sequence alignments. We then showed that none of the human isoforms can complement heat-shocked DnaK knockout Escherichia coli cells. However, chimeric Hsp70s consisting of the human nucleotide-binding domain and the substrate-binding domain of DnaK complement during heat shock, providing further evidence in vivo of the divergent function of the Hsp70 substrate-binding domains. We also demonstrated that the differences in heat shock complementation among the chimeras are not due to loss of DnaJ binding. Although we do not exclude JDPs as additional specificity factors, our data demonstrate substrate specificity among the Hsp70s, which has important implications for inhibitor development in cancer and neurodegeneration.

Heat shock protein family A member 8 serving as a co-activator of transcriptional factor ETV4 up-regulates PHLDA2 to promote the growth of liver cancer

Heat shock protein family A member 8 (HSPA8) participates in the folding or degradation of misfolded proteins under stress and plays critical roles in cancer. In this study, we investigated the function of HSPA8 in the development of liver cancer. By analyzing the TCGA transcriptome dataset, we found that HSPA8 was upregulated in 134 clinical liver cancer tissue samples, and positively correlated with poor prognosis. IHC staining showed the nuclear and cytoplasmic localization of HSPA8 in liver cancer cells. Knockdown of HSPA8 resulted in a decrease in the proliferation of HepG2 and Huh-7 cells. ChIP-seq and RNA-seq analysis revealed that HSPA8 bound to the promoter of pleckstrin homology-like domain family A member 2 (PHLDA2) and regulated its expression. The transcription factor ETV4 in HepG2 cells activated PHLDA2 transcription. HSPA8 and ETV4 could interact with each other in the cells and colocalize in the nucleus. From a functional perspective, we demonstrated that HSPA8 upregulated PHDLA2 through the coactivating transcription factor ETV4 to enhance the growth of liver cancer in vitro and in vivo. From a therapeutic perspective, we identified both HSPA8 and PHDLA2 as novel targets in the treatment of HCC. In conclusion, this study demonstrates that HSPA8 serves as a coactivator of ETV4 and upregulates PHLDA2, leading to the growth of HCC, and is a potential therapeutic target in HCC treatment.

Prognosis value and positive association of Rab1A/IL4Rα aberrant expression in gastric cancer

Gastric cancer (GC) is the most common gastrointestinal cancer and the leading cause of worldwide cancer-associated mortality. Several GC patients are diagnosed at the advanced stage with an unsatisfactory 5-year survival rate. Rab1A was significantly associated with IL4Rα expression in non-small cell lung cancer. However, their potential correlation in expression and prognosis remains largely unknown in GC. In this study, Rab1A/IL-4Rα was significantly increased in GC than in para-cancerous tissues, and Rab1A/IL-4Rα overexpression caused poor prognosis among GC patients. Rab1A expression was significantly correlated with IL-4Rα expression in GC tissues, as determined by IHC analysis. In addition, the mRNA expression of Rab1A was closely linked with the IL-4Rα mRNA expression in GC tissue expressed by qPCR. Furthermore, the Kaplan-Meier analysis demonstrated that the group with negative Rab1A and IL-4Rα expression had longer 5-year survival rates than the other group. Besides, the group with positive Rab1A and IL-4Rα expression had a worse prognosis than the other group. Finally, nomograms revealed the overall 3 and 5-year survival determined crucial roles of Rab1A/IL-4Rα expression in predicting the prognosis of GC patients. Therefore, Rab1A/IL-4Rα is vital in GC, providing a novel perspective on targeted GC therapy.

Discovery and Development of a Selective Inhibitor of the ER Resident Chaperone Grp78

A recent study illustrated that a fluorescence polarization assay can be used to identify substrate-competitive Hsp70 inhibitors that can be isoform-selective. Herein, we use that assay in a moderate-throughput screen and report the discovery of a druglike amino-acid-based inhibitor with reasonable specificity for the endoplasmic reticular Hsp70, Grp78. Using traditional medicinal chemistry approaches, the potency and selectivity were further optimized through structure-activity relationship (SAR) studies in parallel assays for six of the human Hsp70 isoforms. The top compounds were all tested against a panel of cancer cell lines and disappointingly showed little effect. The top-performing compound, 8, was retested using a series of endoplasmic reticulum (ER) stress-inducing agents and found to synergize with these agents. Finally, 8 was tested in a spheroid tumor model and found to be more potent than in two-dimensional models. The optimized Grp78 inhibitors are the first reported isoform-selective small-molecule-competitive inhibitors of an Hsp70-substrate interaction.

The Role of Heat Shock Protein 70 Subfamily in the Hyperplastic Prostate: From Molecular Mechanisms to Therapeutic Opportunities

Benign prostatic hyperplasia (BPH) is one of the most common causes of lower urinary tract symptoms (LUTS) in men, which is characterized by a noncancerous enlargement of the prostate. BPH troubles the vast majority of aging men worldwide; however, the pathogenetic factors of BPH have not been completely identified. The heat shock protein 70 (HSP70) subfamily, which mainly includes HSP70, glucose-regulated protein 78 (GRP78) and GRP75, plays a crucial role in maintaining cellular homeostasis. HSP70s are overexpressed in the course of BPH and involved in a variety of biological processes, such as cell survival and proliferation, cell apoptosis, epithelial/mesenchymal transition (EMT) and fibrosis, contributing to the development and progress of prostate diseases. These chaperone proteins also participate in oxidative stress, a cellular stress response that takes place under stress conditions. In addition, HSP70s can bind to the androgen receptor (AR) and act as a regulator of AR activity. This interaction of HSP70s with AR provides insight into the importance of the HSP70 chaperone family in BPH pathogenesis. In this review, we discuss the function of the HSP70 family in prostate glands and the role of HSP70s in the course of BPH. We also review the potential applications of HSP70s as biomarkers of prostate diseases for targeted therapies.

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.

A novel circRNA-miRNA-mRNA network reveals hsa-circ-0040039 as a biomarker for intervertebral disc degeneration

Objective

Alterations in the structure and function of intervertebral discs by multifaceted chronic processes can result in intervertebral disc degeneration (IDD). The mechanisms involved in IDD are still unknown.

Methods

We investigated the possible mechanisms underlying IDD using a bioinformatics analysis of publicly available microarray expression datasets and built a circular RNA–microRNA–mRNA (circRNA–miRNA–mRNA) network based on the results. Datasets GSE67566 and GSE116726 were downloaded from the Gene Expression Omnibus (GEO) and analyzed using the limma package in R. The CircInteractome database was used to detect miRNAs related to circRNA, and TargetScan, miRDB, and miRTarBase were used to predict target mRNAs. Key target genes were annotated using Gene Ontology terms.

Results

The circRNA hsa-circ-0040039 was found to have the top log fold-change score. Analysis using Metascape showed that the associated genes were enriched mainly in the cell cycle. The Cytoscape plugin MCODE predicted that two members of the RAS oncogene family—RAB1A and RAB1B—and multiple coagulation factor deficiency (MCFD2) may play key roles in IDD.

Conclusion

Our results suggested that hsa-circ-0040039 and the related network may be potential biomarkers for IDD.

HDAC6 Inhibition Extinguishes Autophagy in Cancer: Recent Insights

Simple Summary

Autophagy is an essential process in cell recycling, and its involvement in cancer has been increasingly recognized in the last few decades. This mechanism acts as a double-edged sword in tumor progression and is known to either block or promote tumorigenesis in a context-specific manner. Its role in determining chemotherapeutic resistance makes it a potential target in cancer treatment. The two autophagic inhibitors hydroxychloroquine and chloroquine are currently used in the clinic but cause several side effects in tumor patients. Since recent studies also show that epigenetic enzymes such as histone deacetylase (HDAC) proteins are able to modulate autophagy, this review focuses on the ability of HDAC6 to actively regulate the autophagic process. We also explore the possibility of using HDAC6 inhibitors as therapeutic agents in adjuvant treatment or in combination with autophagic modulators to trigger this mechanism, thus avoiding the occurrence and effects of chemoresistance.

Abstract

Autophagy is an essential intracellular catabolic mechanism involved in the degradation and recycling of damaged organelles regulating cellular homeostasis and energy metabolism. Its activation enhances cellular tolerance to various stresses and is known to be involved in drug resistance. In cancer, autophagy has a dual role in either promoting or blocking tumorigenesis, and recent studies indicate that epigenetic regulation is involved in its mechanism of action in this context. Specifically, the ubiquitin-binding histone deacetylase (HDAC) enzyme HDAC6 is known to be an important player in modulating autophagy. Epigenetic modulators, such as HDAC inhibitors, mediate this process in different ways and are already undergoing clinical trials. In this review, we describe current knowledge on the role of epigenetic modifications, particularly HDAC-mediated modifications, in controlling autophagy in cancer. We focus on the controversy surrounding their ability to promote or block tumor progression and explore the impact of HDAC6 inhibitors on autophagy modulation in cancer. In light of the fact that targeted drug therapy for cancer patients is attracting ever increasing interest within the research community and in society at large, we discuss the possibility of using HDAC6 inhibitors as adjuvants and/or in combination with conventional treatments to overcome autophagy-related mechanisms of resistance.

Similarities and Differences of Hsp70, hsc70, Grp78 and Mortalin as Cancer Biomarkers and Drug Targets

Background: Upregulation of Heath Shock Protein 70 (HSP70) chaperones supports cancer cell survival. Their high homology causes a challenge to differentiate them in experimental or prevention and treatment strategies. The objective of this investigation was to determine similarities and differences of Hsp70, hsc70, Grp78 and Mortalin members of the HSP70 family encoded by HSPA1, HSPA8, HSPA5 and HSPA9 genes, respectively. Methods: Literature reviews were conducted using HSPA1, HSPA5, HSPA8 and HSPA9 gene or protein names or synonyms combined with biological or cancer-relevant terms. Ingenuity Pathway Analysis was used to identify and compare profiles of proteins that directly bind individual chaperones and their associated pathways. TCGA data was probed to identify associations of hsc70 with cancer patient survival. ClinicalTrials.gov was used to identify HSP70 family studies. Results: The chaperones have similar protein folding functions. Their different cellular effects are determined by co-chaperones and client proteins combined with their intra- and extra-cellular localizations. Their upregulation is associated with worse patient prognosis in multiple cancers and can stimulate tumor immune responses or drug resistance. Their inhibition selectively kills cancer over healthy cells. Conclusions: Differences in Hsp70, hsc70, Grp78 and mortalin provide opportunities to calibrate HSP70 inhibitors for individual cancers and combination therapies.

Targeting HSPA8 inhibits proliferation via downregulating BCR-ABL and enhances chemosensitivity in imatinib-resistant chronic myeloid leukemia cells

The resistance to tyrosine kinase inhibitors is currently a major problem for chronic myeloid leukemia (CML) treatment and HSPA8 is highly expressed and a hallmark of poor prognosis in several human cancers. However, its role in imatinib-resistant CML (IR-CML) cells remains undetermined. Here, we determined HSPA8 was overexpressed in IR-CML cells and associated with imatinib resistance. HSPA8 ablation could downregulate BCR-ABL/STAT5 and BCR-ABL/AKT signaling pathways, dramatically induce proliferation inhibition, autophagy, G0/G1 phase cell cycle arrest but not apoptosis in IR-CML cells. Significantly, HSPA8 ablation enhanced the antitumor activity of imatinib via promoting apoptosis in vitro and vivo. These findings unraveled that HSPA8 ablation inhibits proliferation via downregulating BCR-ABL and enhances chemosensitivity of imatinib in IR-CML cells, which investigate the role and molecular mechanism of HSPA8 in IR-CML cells and suggest that HSPA8 may be a potential target for IR-CML treatment.

Function, Therapeutic Potential, and Inhibition of Hsp70 Chaperones

Hsp70s are among the most highly conserved proteins in all of biology. Through an iterative binding and release of exposed hydrophobic residues on client proteins, Hsp70s can prevent aggregation and promote folding to the native state of their client proteins. The human proteome contains eight canonical Hsp70s. Because Hsp70s are relatively promiscuous they play a role in folding a large proportion of the proteome. Hsp70s are implicated in disease through their ability to regulate protein homeostasis. In recent years, researchers have attempted to develop selective inhibitors of Hsp70 isoforms to better understand the role of individual isoforms in biology and as potential therapeutics. Selective inhibitors have come from rational design, forced localization, and serendipity, but the development of completely selective inhibitors remains elusive. In the present review, we discuss the Hsp70 structure and function, the known Hsp70 client proteins, the role of Hsp70s in disease, and current efforts to discover Hsp70 modulators.

Chaperone Mediated Autophagy Substrates and Components in Cancer

Chaperone-mediated autophagy (CMA) represents a specific way of lysosomal protein degradation and contrary to macro and microautophagy is independent of vesicles formation. The role of CMA in different physiopathological processes has been studied for several years. In cancer, alterations of the CMA principal components, Hsc70 and Lamp2A protein and mRNA levels, have been described in malignant cells. However, changes in the expression levels of these CMA components are not always associated with changes in CMA activity and their biological significance must be carefully interpreted case by case. The objective of this review is to discuss whether altering the CMA activity, CMA substrates or CMA components is accurate to avoid cancer progression. In particular, this review will discuss about the evidences in which alterations CMA components Lamp2A and Hsc70 are associated or not with changes in CMA activity in different cancer types. This analysis will help to better understand the role of CMA activity in cancer and to elucidate whether CMA can be considered as target for therapeutics. Further, it will help to define whether the attention of the investigation should be focused on Lamp2A and Hsc70 because they can have an independent role in cancer progression beyond of their participation in altered CMA activity.

Clinical value and potential association of Rab1A and FoxM1 aberrant expression in colorectal cancer

Colorectal carcinoma (CRC) is one of the most common malignancies with a dismal 5-year survival rate. Our recent study indicated that Rab1A expression was closely related to GLI1 expression. A previous study shows that aberrant overexpression of GLI1 promotes colorectal cancer metastasis via FoxM1 overexpression. However, the potential correlation between Rab1A and FoxM1 in CRC remains elusive. Immunohistochemistry was performed to investigate the association of the expression of Rab1A and FoxM1 and to determine the prognosis in 135 CRC tissue and adjacent normal tissues. Using Oncomine datasets, we found that Rab1A and FoxM1 mRNA were obviously upregulated in CRC tissues compared to normal tissues. Additionally, the expression of Rab1A and FoxM1 was significantly higher in CRC tissues than that in normal tissues. Rab1A expression was positively correlated with FoxM1 expression in CRC, especially in TNM stage III. In addition, Rab1A and FoxM1 overexpression was found to be significantly correlated with poor prognosis in CRC patients. Besides, both high expression of Rab1A and FoxM1 led to a worse prognosis than anyone low group, and both low expression of Rab1A and FoxM1 had a better prognosis than the anyone low group. Therefore, Rab1A and FoxM1 play crucial roles and could be used as clinical biomarkers in CRC.

Expression of Rab1A in bladder cancer and its clinical implications

Rab1A protein has been identified to be highly expressed in a number of malignant tumor tissues and to participate in the regulation of tumor development, but no data concerning bladder cancer have been described at present. The present study measured the expression of Rab1A in bladder cancer tissues and cell lines, and analyzed its clinical significance for patients with bladder cancer. A total of 153 pairs of bladder cancer tumor tissues and adjacent cancer healthy tissues were included in the present study. Western blot analysis and immunohistochemistry were used to measure the expression of Rab1A protein in normal bladder and bladder cancer cell line, and bladder cancer and normal adjacent tissues. SPSS 20.0 software was used for statistical analysis and mapping of survival curves in patients with bladder cancer. The expression levels of Rab1A protein in normal bladder cells and tissues was significantly decreased compared with that in bladder cancer cells and tissues, and it was significantly associated with tumor size, histological grade, tumor-node-metastasis (TNM) stage, lymph node metastasis and remote metastasis in 153 patients with bladder cancer. Cox regression analysis demonstrated that the expression of Rab1A protein in bladder cancer tissues was an independent risk factor for prognosis (overall risk=0.549; 95% confidence interval=0.139-0.916). The 5-year survival rate of patients with bladder cancer with high expression levels of Rab1A protein was 48.613%, which was significantly decreased compared with the rate of patients with low expression 75.31% (P<0.05). The expression of Rab1A in bladder cancer tissues and cell lines was upregulated, and its expression increased with increasing TNM stages. It was also associated with the metastasis of tumor cells and negatively affected the survival time of patients with bladder cancer.

Rab1A knockdown represses proliferation and promotes apoptosis in gastric cancer cells by inhibition of mTOR/p70S6K pathway

Rab1A, a member of the Ras-like protein in rat brain (Rab) family, acts as an oncogene in a variety of malignant tumors. Previous studies reported that Rab1A was highly expressed in GC tissues. However, the function and molecular mechanism of Rab1A in gastric cancer (GC) development remain far from being addressed. Rab1A mRNA and protein levels were detected by qRT-PCR and western blot, respectively. Cell proliferation was evaluated by CCK-8 and BrdU incorporation assays. Apoptosis was estimated by flow cytometry analysis and western blot analysis of B cell lymphoma 2 (Bcl-2), myeloid cell leukemia 1 (Mcl-1), Bcl-2 associated X (Bax), and Bcl-2 homologous antagonist/killer (Bak) expression. Alteration of the mammalian target of rapamycin (mTOR)/p70 ribosomal protein S6 kinase (p70S6K) signaling pathway was detected by western blot. We found that Rab1A expression at both mRNA and protein was upregulated in GC cells. Rab1A knockdown significantly inhibited cell proliferation and induced apoptosis in GC cells. Rab1A overexpression promoted proliferation, inhibited cisplatin-induced apoptosis, and increased xenograft growth. In addition, we found that Rab1A knockdown suppressed the mTOR/p70S6K pathway in GC cells. Moreover, activation of mTOR/p70S6K pathway by MHY1485 abolished the effects of Rab1A knockdown on cell proliferation and apoptosis. In conclusion, Rab1A knockdown repressed proliferation and promoted apoptosis in GC cells by inhibition of the mTOR/p70S6K pathway.

Pooled analysis of prognostic value and clinical significance of Rab1A expression in human solid tumors

BACKGROUND

This study aims to assess the relationship between Rab1A expression and clinicopathological parameters and prognosis of patients with human solid cancer by summarizing the studies included.

METHODS

PubMed, EMBASE, The Cochrane Library, and other sources were searched for relative studies. The risk ratios (RRs) and confidence interval (CI) were used to assess association between Rab1A expression and clinical parameters and prognosis in solid cancer patients.

RESULTS

Eight studies were included in the final analysis with 800 patients. The results revealed that expression of Rab1A was significantly related with differentiation (RR = 0.883, 95%CI = 0.782-0.997, P = .044), lymph node metastasis (RR = 0.835, 95%CI = 0.753-0.926, P = .001), tumor-lymph node-metastasis (TNM) stage (RR = 1.190, 95%CI = 1.071-1.322, P < .001) and tumor size (RR = 0.818, 95%CI = 0.730-0.915, P < .001). What is more, no significant difference was seen in 1-year survival between high and low expression of Rab1A in multiple malignancies (RR = 0.855, 95%CI = 0.697-1.050, P = .136). However, increased Rab1A revealed poorer prognosis with 2-year survival (RR = 0.760, 95%CI = 0.701-0.824, P < .001), 3-year survival (RR = 0.669, 95%CI = 0.604-0.742, P < .001), 4-year survival (RR = 0.622, 95%CI = 0.554-0.698, P < .001) and 5-year survival (RR = 0.525, 95%CI = 0.458-0.698, P < .001). Expression of Rab1A was increased obviously in solid cancer tissues compared with the adjacent normal tissue (RR = 4.78, 95%CI 4.05-5.63, P = .015).

CONCLUSION

This study revealed Rab1A expression links closely with tumor size, differentiation, lymph node metastasis, TNM stage and poor prognosis of human solid cancer patients. It may act as a biomarker of prognosis and a novel therapeutic target in solid cancer.

Expression analysis and implication of Rab1A in gastrointestinal relevant tumor

Gastrointestinal cancers have become increasingly prevalent worldwide. Previous studies have reported an oncogenic function of Rab1A in colorectal cancer and hepatocellular carcinomas via the mTOR pathway. However, the exact role of Rab1A in gastrointestinal cancers remains elusive. We detected significantly higher expression of Rab1A in the gastrointestinal tumor tissues compared to that in other cancer types following an in silico analysis of TGCA and GTEX databases. Furthermore, Rab1A was overexpressed in the gastrointestinal tumor tissues compared to the para-tumor tissues. Although Rab1A expression levels were not associated with the tumor-lymph node-metastasis (TNM) stage, Rab1A overexpression in the tumor tissues of a gastric cancer (GC) cohort was strongly correlated with poor prognosis in the patients. In addition, Rab1A knockdown significantly inhibited the in vitro proliferation and migration abilities of GC cells, as well as the growth of GC xenografts in vivo. Furthermore, a positive correlation was observed between Rab1A expression levels and that of different upstream/downstream mTOR targets. Taken together, Rab1A regulates the PI3K-AKT-mTORC1 pathway through the mTORC1 complex consisting of mTORC1, Rheb and Rab1A, and is a promising therapeutic target in GC.

miR‑139‑3p suppresses the invasion and migration properties of breast cancer cells by targeting RAB1A

Accumulated evidence indicates that aberrant microRNAs (miRNAs) expression plays an important role in the initiation and progression of various cancers, including breast cancer. Previous studies suggested that miR-139-3p might serve as a tumor suppressor and is downregulated in several cancer types. However, the expression patterns and exact role of miR-139-3p in breast cancer remain to be elucidated. In this study, we aimed to analyze the effect of miR-139-3p on the progression of breast cancer and the mechanism involved. Through bioinformatics analysis and in vitro experimental studies, we found that miR-139-3p was decreased in breast cancer tissues and cell lines, and decreased miR-139-3p is associated with a poor prognosis in breast cancer patients. Overexpression of miR-139-3p by transfection significantly inhibits cell proliferation, migration, and invasion of breast cancer cells. Bioinformatics analysis and luciferase reporter gene assay confirmed that RAB1A was a potential target of miR-139-3p. Furthermore, overexpression of RAB1A counteracted the suppressing effects of miR-139-3p on breast cancer cell migration, invasion and epithelial-to-mesenchymal transition (EMT). Taken together, these data suggest that miR-139-3p plays a tumor suppressive role in breast cancer by targeting RAB1A and may serve as a potential new biomarker for breast cancer prognosis.

Rab1A promotes proliferation and migration abilities via regulation of the HER2/AKT-independent mTOR/S6K1 pathway in colorectal cancer

Colorectal carcinoma (CRC) is one of the most common malignancies worldwide and the second leading cause of cancer-related deaths in the US. Recently, Rab1A has been reported to be an activator of mTORC1 and p-S6K1, which is downstream of mTORC1. However, the association between Rab1A and p-S6K1 in CRC remains elusive. In the present study, we first demonstrated that Rab1A was overexpressed in CRC tissues and Rab1A overexpression was positively related to lymph node invasion, degree of differentiation, venous invasion and tumor-node-metastasis (TNM) stage. In both TNM stage I–II and III–IV patients, Rab1A-positive patients had a shorter survival time than Rab1A-negative patients. Furthermore, in univariate and multivariate analyses, only Rab1A expression was verified as an independent prognostic factor for survival in CRC patients. The level of p-S6K1 was markedly high in CRC tissues and Rab1A expression level had a positive association with p-S6K1 level. In addition, high levels of both Rab1A and p-S6K1 were associated with a poorer prognosis compared with low expression of either Rab1A or p-S6K1 level. Moreover, high levels of both Rab1A and p-S6K1 were associated with a poorer prognosis than patients with high levels of either Rab1A or p-S6K1 alone. Finally, knockdown of Rab1A expression inhibited migration and proliferation of SW480 and HCT116 cell lines by targeting regulation of p-S6K1. Thus, our findings indicate that Rab1A plays an important role in CRC and may provide a therapeutic target for CRC, particularly for mTORC1-targeted therapy-resistant cancers.

Overexpression of Hsc70 promotes proliferation, migration, and invasion of human glioma cells

Migration and invasion are often recognized as the main reasons for the high recurrence and death rates of glioma and limit the efficacy of surgery and other antitumor therapies. In this study, we found over activation of heat shock cognate protein 70 (Hsc70) in human glioma specimens, which was closely related to glioma grade. We investigated whether Hsc70 induced the migration and invasion of glioma cells. Wound healing and transwell migration assay were used to determine the migration and invasion ability of human glioma U251 and U87 cells, in which the expression of Hsc70 was knocked down by small interfering RNA. Western blot analysis was performed to determine the expression of FAK-Src signaling in malignant glioma cells. The results showed that Hsc70 deficiency significantly retarded migration and invasion and reduced the phosphorylation of FAK, Src, and Pyk2 in U251 and U87 cells. Overall, our results indicate that the migration and invasion capacity of human brain glioma cells is at least partly induced by Hsc70-dependent activation of FAK-Src signaling.

Hsc70 Interacts with β4GalT5 to Regulate the Growth of Gliomas

Heat shock cognate protein 70 (Hsc70) is a key mediator for the maintenance of intracellular proteins and regulates cellular activities. And it is elevated in various tumor tissues including glioma, which is closely related to the malignancy and poor prognosis of the tumors. However, the effects of Hsc70 on gliomas and its regulatory mechanism have not yet been elucidated. In the present study, we found that Hsc70 was overexpressed in glioma tissues and cultured glioma cells. Furthermore, Hsc70 expression exhibited positive correlation with the grades of gliomas. Knockdown of Hsc70 could effectively inhibit cell proliferation and increase cell apoptosis. Furthermore, we identified that β4GalT5 was a critical target for Hsc70-mediated anti-glioma effects. Blocking β4GalT5 activity could effectively reverse the anti-tumor effect of Hsc70. Taken together, these data indicate that Hsc70 regulates β4GalT5 levels, and possibly plays a role in cell proliferation and apoptosis of glioma.

Comprehensive transcriptomic analysis of heat shock proteins in the molecular subtypes of human breast cancer

BACKGROUND

Heat Shock Proteins (HSPs), a family of genes with key roles in proteostasis, have been extensively associated with cancer behaviour. However, the HSP family is quite large and many of its members have not been investigated in breast cancer (BRCA), particularly in relation with the current molecular BRCA classification. In this work, we performed a comprehensive transcriptomic study of the HSP gene family in BRCA patients from both The Cancer Genome Atlas (TCGA) and the Molecular Taxonomy of Breast Cancer International Consortium (METABRIC) cohorts discriminating the BRCA intrinsic molecular subtypes.

METHODS

We examined gene expression levels of 1097 BRCA tissue samples retrieved from TCGA and 1981 samples of METABRIC, focusing mainly on the HSP family (95 genes). Data were stratified according to the PAM50 gene expression (Luminal A, Luminal B, HER2, Basal, and Normal-like). Transcriptomic analyses include several statistical approaches: differential gene expression, hierarchical clustering and survival analysis.

RESULTS

Of the 20,531 analysed genes we found that in BRCA almost 30% presented deregulated expression (19% upregulated and 10% downregulated), while of the HSP family 25% appeared deregulated (14% upregulated and 11% downregulated) (|fold change| > 2 comparing BRCA with normal breast tissues). The study revealed the existence of shared HSP genes deregulated in all subtypes of BRCA while other HSPs were deregulated in specific subtypes. Many members of the Chaperonin subfamily were found upregulated while three members (BBS10, BBS12 and CCTB6) were found downregulated. HSPC subfamily had moderate increments of transcripts levels. Various genes of the HSP70 subfamily were upregulated; meanwhile, HSPA12A and HSPA12B appeared strongly downregulated. The strongest downregulation was observed in several HSPB members except for HSPB1. DNAJ members showed heterogeneous expression pattern. We found that 23 HSP genes correlated with overall survival and three HSP-based transcriptional profiles with impact on disease outcome were recognized.

CONCLUSIONS

We identified shared and specific HSP genes deregulated in BRCA subtypes. This study allowed the recognition of HSP genes not previously associated with BRCA and/or any cancer type, and the identification of three clinically relevant clusters based on HSPs expression patterns with influence on overall survival.

Endogenous epitope tagging of heat shock protein 70 isoform Hsc70 using CRISPR/Cas9

Heat shock protein 70 (Hsp70) is an evolutionarily well-conserved molecular chaperone involved in several cellular processes such as folding of proteins, modulating protein-protein interactions, and transport of proteins across the membrane. Binding partners of Hsp70 (known as "clients") are identified on an individual basis as researchers discover their particular protein of interest binds to Hsp70. A full complement of Hsp70 interactors under multiple stress conditions remains to be determined. A promising approach to characterizing the Hsp70 "interactome" is the use of protein epitope tagging and then affinity purification followed by mass spectrometry (AP-MS/MS). AP-MS analysis is a widely used method to decipher protein-protein interaction networks and identifying protein functions. Conventionally, the proteins are overexpressed ectopically which interferes with protein complex stoichiometry, skewing AP-MS/MS data. In an attempt to solve this issue, we used CRISPR/Cas9-mediated gene editing to integrate a tandem-affinity (TAP) epitope tag into the genomic locus of HSC70. This system offers several benefits over existing expression systems including native expression, no requirement for selection, and homogeneity between cells. This cell line, freely available to chaperone researchers, will aid in small and large-scale protein interaction studies as well as the study of biochemical activities and structure-function relationships of the Hsc70 protein.

Heat shock protein 70 inhibitors suppress androgen receptor expression in LNCaP95 prostate cancer cells

Androgen deprivation therapy is initially effective for treating patients with advanced prostate cancer; however, the prostate cancer gradually becomes resistant to androgen deprivation therapy, which is termed castration-resistant prostate cancer (CRPC). Androgen receptor splice variant 7 (AR-V7), one of the causes of CRPC, is correlated with resistance to a new-generation AR antagonist (enzalutamide) and poor prognosis. Heat shock protein 70 (Hsp70) inhibitor is known to decrease the levels of full-length AR (AR-FL), but little is known about its effects against CRPC cells expressing AR-V7. In this study, we investigated the effect of the Hsp70 inhibitors quercetin and VER155008 in the prostate cancer cell line LNCaP95 that expresses AR-V7, and explored the mechanism by which Hsp70 regulates AR-FL and AR-V7 expression. Quercetin and VER155008 decreased cell proliferation, increased the proportion of apoptotic cells, and decreased the protein levels of AR-FL and AR-V7. Furthermore, VER155008 decreased AR-FL and AR-V7 mRNA levels. Immunoprecipitation with Hsp70 antibody and mass spectrometry identified Y-box binding protein 1 (YB-1) as one of the molecules regulating AR-FL and AR-V7 at the transcription level through interaction with Hsp70. VER155008 decreased the phosphorylation of YB-1 and its localization in the nucleus, indicating that the involvement of Hsp70 in AR regulation might be mediated through the activation and nuclear translocation of YB-1. Collectively, these results suggest that Hsp70 inhibitors have potential anti-tumor activity against CRPC by decreasing AR-FL and AR-V7 expression through YB-1 suppression.

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.

Ophiobolin A Induces Autophagy and Activates the Mitochondrial Pathway of Apoptosis in Human Melanoma Cells

Ophiobolin A, a fungal toxin from Bipolaris species known to affect different cellular processes in plants, has recently been shown to have anti-cancer activity in mammalian cells. In the present study, we investigated the anti-proliferative effect of Ophiobolin A on human melanoma A375 and CHL-1 cell lines. This cellular model was chosen because of the incidence of melanoma malignant tumor on human population and its resistance to chemical treatments. Ophyobolin A strongly reduced cell viability of melanoma cells by affecting mitochondrial functionality. The toxin induced depolarization of mitochondrial membrane potential, reactive oxygen species production and mitochondrial network fragmentation, leading to autophagy induction and ultimately resulting in cell death by activation of the mitochondrial pathway of apoptosis. Finally, a comparative proteomic investigation on A375 cells allowed to identify several Ophiobolin A down-regulated proteins, which are involved in fundamental processes for cell homeostasis and viability.

Determining protein biomarkers for DLBCL using FFPE tissues from HIV negative and HIV positive patients

DLBCL is the most common lymphoma subtype occurring in older populations as well as in younger HIV infected patients. The current treatment options for DLBCL are effective for most patients yet the relapse rate is high. While many biomarkers for DLBCL exist, they are not in clinical use due to low sensitivity and specificity. In addition, these biomarkers have not been studied in the HIV context. Therefore, the identification of new biomarkers for HIV negative and HIV positive DLBCL, may lead to a better understanding of the disease pathology and better therapeutic design. Protein biomarkers for DLBCL were determined using MALDI imaging mass spectrometry (IMS) and characterised using LC-MS. The expression of one of the biomarkers, heat shock protein (Hsp) 70, was confirmed on a separate cohort of samples using immunohistochemistry. The biomarkers identified in the study consisted of four protein clusters including glycolytic enzymes, ribosomal proteins, histones and collagen. These proteins could differentiate between control and tumour tissue, and the DLBCL immunohistochemical subtypes in both cohorts. The majority (41/52) of samples in the confirmation cohort were negative for Hsp70 expression. The HIV positive DLBCL cases had a higher percentage of cases expressing Hsp70 than their HIV negative counterparts. The non-GC subtype also frequently overexpressed Hsp70, confirming MALDI IMS data. The expression of Hsp70 did not correlate with survival in both the HIV negative and HIV positive cohort. This study identified potential biomarkers for HIV negative and HIV positive DLBCL from FFPE tissue sections. These may be used as diagnostic and prognostic markers complementary to current clinical management programmes for DLBCL.

Protection of stromal cell-derived factor 2 by heat shock protein 72 prevents oxaliplatin-induced cell death in oxaliplatin-resistant human gastric cancer cells

Heat shock protein 72 (Hsp72) is a molecular chaperone that assists in the folding of nascent polypeptides and in the refolding of denatured proteins. In many cancers, Hsp72 is constitutively expressed at elevated levels, which can result in enhanced stress tolerance. Similarly, following treatment with anticancer drugs, Hsp72 binds to denatured proteins that may be essential for survival. We therefore hypothesized that Hsp72 client proteins may play a crucial role in drug resistance. Here, we aimed to identify proteins that are critical for oxaliplatin (OXA) resistance by analyzing human gastric cancer cell lines, as well as OXA-resistant cells via a mass spectrometry-based proteomic approach combined with affinity purification using anti-Hsp72 antibodies. Stromal cell-derived factor 2 (SDF-2) was identified as an Hsp72 client protein unique to OCUM-2M/OXA cells. SDF-2 was overexpressed in OXA-resistant cells and SDF-2 silencing promoted the apoptotic effects of OXA. Furthermore, Hsp72 prevented SDF-2 degradation in a chaperone activity-dependent manner. Together, our data demonstrate that Hsp72 protected SDF-2 to avoid OXA-induced cell death. We propose that inhibition of SDF-2 may comprise a novel therapeutic strategy to counteract OXA-resistant cancers.

Experimental Adaptation of Rotaviruses to Tumor Cell Lines

A number of viruses show a naturally extended tropism for tumor cells whereas other viruses have been genetically modified or adapted to infect tumor cells. Oncolytic viruses have become a promising tool for treating some cancers by inducing cell lysis or immune response to tumor cells. In the present work, rotavirus strains TRF-41 (G5) (porcine), RRV (G3) (simian), UK (G6-P5) (bovine), Ym (G11-P9) (porcine), ECwt (murine), Wa (G1-P8), Wi61 (G9) and M69 (G8) (human), and five wild-type human rotavirus isolates were passaged multiple times in different human tumor cell lines and then combined in five different ways before additional multiple passages in tumor cell lines. Cell death caused by the tumor cell-adapted isolates was characterized using Hoechst, propidium iodide, 7-AAD, Annexin V, TUNEL, and anti-poly-(ADP ribose) polymerase (PARP) and -phospho-histone H2A.X antibodies. Multiple passages of the combined rotaviruses in tumor cell lines led to a successful infection of these cells, suggesting a gain-of-function by the acquisition of greater infectious capacity as compared with that of the parental rotaviruses. The electropherotype profiles suggest that unique tumor cell-adapted isolates were derived from reassortment of parental rotaviruses. Infection produced by such rotavirus isolates induced chromatin modifications compatible with apoptotic cell death.

Glutathione-S-transferase omega 1 (GSTO1-1) acts as mediator of signaling pathways involved in aflatoxin B1-induced apoptosis-autophagy crosstalk in macrophages

Aflatoxin B1 (AFB1) is the most toxic aflatoxin species and has been shown to be associated with specific as well as non-specific immune responses. In the present study, using murine macrophage Raw 264.7 cells as a model, we report that short exposure (6h) to AFB1 caused an increase in the cellular calcium pool in mitochondria, which in turn elevated reactive oxygen species (ROS)-mediated oxidative stress and led to loss of mitochondrial membrane potential and ultimately c-Jun N-terminal kinases (JNK)-mediated caspase-dependent cell death. On the contrary, longer exposure (12h) to AFB1 reduced JNK phosphorylation and cell death in macrophages. Measurement of autophagic flux demonstrated that autophagy induction through the canonical pathway was responsible for suppressing AFB1-induced apoptosis after 12h. As a detailed molecular mechanism, we found that the unfolded protein response (UPR) machinery was active at 12h post-exposure to AFB1 and induced cytoprotective autophagy as confirmed by determination of major autophagic markers. Inhibition of autophagy by Beclin-1 siRNA also resulted in JNK-mediated cell death. We further established that glutathione S transferase omega1-1 (GSTO1-1), a specific class of GST, was the responsible factor between apoptosis and autophagy crosstalk. Targeting of GSTO1-1 increased JNK-mediated apoptosis by 2-fold compared to the control, whereas autophagy rate was reduced. Thus, increased expression of GSTO1-1 was associated with increased protein glutathionylation, an important protein modification in response to cellular redox status.

New challenges in pseudopodial proteomics by a laser-assisted cell etching technique

Pseudopodia are ventral membrane protrusions that extend toward higher concentrations of chemoattractants and play key roles in cell migration and cancer cell invasion. Cancers, including carcinoma and sarcoma, become life threatening when they invade surrounding structures and other organs. Understanding the molecular basis of invasiveness is important for the elimination of cancers. Thus, determining the pseudopodial composition will offer insights into the mechanisms underlying tumor cell invasiveness and provide potential biomarkers and therapeutic targets. Pseudopodial composition has been extensively investigated by using proteomic approaches. A variety of modalities, including gel-based and mass spectrometry-based methods, have been employed for pseudopodial proteomics. Our research group recently established a novel method using excimer laser pulses to selectively harvest pseudopodia, and we successfully identified a number of new pseudopodial constituents. Here, we summarized the conventional proteomic procedures and describe our new excimer laser-assisted method, with a special emphasis on the differences in the methods used to isolate pseudopodia. In addition, we discussed the theoretical background for the use of excimer laser-mediated cell ablation in proteomic applications. Using the excimer laser-assisted method, we showed that alpha-parvin, an actin-binding adaptor protein, is localized to pseudopodia, and is involved in breast cancer invasiveness. Our results clearly indicate that excimer laser-assisted cell etching is a useful technique for pseudopodial proteomics. This article is part of a Special Issue entitled: Medical Proteomics.