Tumor stress-induced phosphoprotein 1 as a prognostic biomarker for breast cancer

Stress-induced phosphoprotein 1: how does this co-chaperone influence the metastasis steps?

In several cancer types, metastasis is associated with poor prognosis, survival, and quality of life, representing a life risk more significant than the primary tumor itself. Metastasis is a multi-step process that spreads tumor cells from primary sites to surrounding or distant organs, originating secondary tumors. The interconnected steps that drive metastasis depend of several capabilities that enable cells to detach from the primary tumor, acquire motility and migrate through the basal membrane; invade and spread through the vascular system, and finally settle and originate a new tumor. Recently, stress-induced phosphoprotein 1 (STIP1) has emerged as a protein capable of driving tumor cells through these metastasis steps by mediating several biological processes and signaling pathways. This protein is mainly known for its function as a co-chaperone, acting as a scaffold for the interaction of its client heat-shock proteins Hsp70/90 chaperones; however, it is also known that STIP1 can act independently of chaperones to activate downstream phosphorylation pathways. The over-expression of STIP1 has been reported across various cancer types, identifying it as a potential biomarker for predicting patient prognosis and monitoring the progression of metastasis. Here, we present a discussion on how this co-chaperone mediates the initial steps of metastasis (cell adhesion loss, epithelial-to-mesenchymal transition, and angiogenesis), highlighting the biological mechanisms in which STIP1 plays a vital role, also presenting an overview of the current knowledge regarding its clinical relevance.

Stress induced phosphoprotein 1 overexpression controls proliferation, migration and invasion and is associated with poor survival in oral squamous cell carcinoma

Objective

Although there have been remarkable achievements in the molecular landscape of oral squamous cell carcinoma (OSCC) in recent years, bringing advances in the understanding of its pathogenesis, development and progression, little has been applied in the prognosis and choosing the optimal treatment. In this study, we explored the influence of the stress induced phosphoprotein 1 (STIP1), which is frequently reported to be highly expressed in many cancers, in OSCCs.

Methods

STIP1 expression was assessed in the TCGA database and in two independent cohorts by immunohistochemistry. Knockdown strategy was applied in OSCC cell lines to determine the impact of STIP1 on viability, proliferation, migration and invasion. The zebrafish model was applied for studying tumor formation and metastasis in vivo. The association of STIP1 and miR-218-5p was explored by bioinformatics and mimics transfection.

Results

STIP1 was highly expressed in OSCCs and significantly associated with shortened survival and higher risk of recurrence. STIP1 down-regulation decreased proliferation, migration and invasion of tumor cells, and reduced the number of metastases in the Zebrafish model. STIP1 and miR-218-5p were inversely expressed, and the transfection of miR-218-5p mimics into OSCC cells decreased STIP1 levels as well as proliferation, migration and invasion.

Conclusion

Our findings show that STIP1 overexpression, which is inversely associated with miR-218-5p levels, contributes to OSCC aggressiveness by controlling proliferation, migration and invasion and is a determinant of poor prognosis.

Hsp70/Hsp90 Organising Protein (Hop): Coordinating Much More than Chaperones

The Hsp70/Hsp90 organising protein (Hop, also known as stress-inducible protein 1/STI1/STIP1) has received considerable attention for diverse cellular functions in both healthy and diseased states. There is extensive evidence that intracellular Hop is a co-chaperone of the major chaperones Hsp70 and Hsp90, playing an important role in the productive folding of Hsp90 client proteins, although recent evidence suggests that eukaryotic Hop is regulatory within chaperone complexes rather than essential. Consequently, Hop is implicated in many key signalling pathways, including aberrant pathways leading to cancer. Hop is also secreted, and it is now well established that Hop interacts with the prion protein, PrP^C, to mediate multiple signalling events. The intracellular and extracellular forms of Hop most likely represent two different isoforms, although the molecular determinants of these divergent functions are yet to be identified. There is also a growing body of research that reports the involvement of Hop in cellular activities that appear independent of either chaperones or PrP^C. While the various cellular functions of Hop have been described, its biological function remains elusive. However, recent knockout studies in mammals suggest that Hop has an important role in embryonic development. This review provides a critical overview of the latest molecular, cellular and biological research on Hop, critically evaluating its function in healthy systems and how this function is adapted in diseased states.

JAK2-Mediated Phosphorylation of Stress-Induced Phosphoprotein-1 (STIP1) in Human Cells

Stress-induced phosphoprotein-1 (STIP1)—a heat shock protein (HSP)70/HSP90 adaptor protein—is commonly overexpressed in malignant cells, where it controls proliferation via multiple signaling pathways, including JAK2/STAT3. We have previously shown that STIP1 stabilizes the protein tyrosine kinase JAK2 in cancer cells via HSP90 binding. In this study, we demonstrate that STIP1 may act as a substrate for JAK2 and that phosphorylation of tyrosine residues 134 and 152 promoted STIP1 protein stability, induced its nuclear-cytoplasmic shuttling, and promoted its secretion into the extracellular space. We also found that JAK2-mediated STIP1 phosphorylation enhanced cell viability and increased resistance to cisplatin-induced cell death. Conversely, interference STIP1 with JAK2 interaction—attained either through site-directed mutagenesis or the use of cell-penetrating peptides—decreased JAK2 protein levels, ultimately leading to cell death. On analyzing human ovarian cancer specimens, JAK2 and STIP1 expression levels were found to be positively correlated with each other. Collectively, these results indicate that JAK2-mediated phosphorylation of STIP-1 is critical for sustaining the JAK2/STAT3 signaling pathway in cancer cells.

Stress-induced phosphoprotein 1 facilitates breast cancer cell progression and indicates poor prognosis for breast cancer patients

Breast cancer (BC) threatened the life health of a tremendous amount of the population, and the estimated number of death is still rising nowadays. We found that stress-induced phosphoprotein 1 (STIP1) is overexpressed in BC tissues compared to non-tumorous breast tissues. Our study is to validate the prognostic value of STIP1 and investigate its biological role in BC. We verified the upregulation of STIP1 in multiple databases, proved that STIP1 is upregulated in BC tissues and cell lines using real-time quantitative PCR (qRT-PCR). We used small interfering RNA to examine the function of STIP1 in BC cell lines (BT-549, MDA-MB-231, Hs-578 T) and explored the mechanism of function of STIP1 in BC cells using Western blotting and qRT-PCR. Analyses of multiple databases indicated that high STIP1 expression is a marker that effectively distinguishes BC patients from healthy control and predicts worse clinical outcomes in BC. The loss-of-function experiments showed that STIP1 silencing results in inhibition of cell proliferation and migration, inducing cell apoptosis, and S-phase arrest in vitro. Our study also showed that STIP1 downregulation inhibited the JAK2/STAT3 pathway and epithelial-mesenchymal transition process. Rescue experiments demonstrated that the oncogenic effect of STIP1 is partially dependent on mediating JAK2 expression. This study verified that STIP1 is an oncogenic gene that promotes BC progression and serves as a valuable diagnostic and outcome-related marker of BC.

Intracellular targeting of STIP1 inhibits human cancer cell line growth

BACKGROUND

Extracellular and cell-surface molecules remain the most common druggable cancer targets. However, intracellular therapeutic modalities are gaining momentum. The overexpression of stress-induced phosphoprotein 1 (STIP1), an adaptor protein that coordinates the functions of different chaperones in protein folding, has been reported in several solid malignancies. Here, we investigated the effects of intracellular STIP1 inhibition, attained either through the HEPES-mediated cytosolic delivery of anti-STIP1 antibodies or the use of a cell-penetrating signal-tagged peptide 520, in different human cancer cell lines and luciferase-expressing murine ovarian cancer cells (MOSEC/Luc) tumor-bearing C57BL/6 mice.

METHODS

The effects of STIP1 in different human cell lines were determined by cell viability, cell cytotoxicity and cell apoptosis assays. Immunoblotting was used to assess the relevant proteins found in this study and tumor xenograft mice models were also employed.

RESULTS

Intracellular targeting of STIP1 inhibited cancer cell line growth and promoted caspase 3-dependent apoptotic cell death. Moreover, the intracellular delivery of anti-STIP1 antibodies facilitated the degradation of STIP1 and two of its client proteins, lysine-specific demethylase 1 and Janus kinase 2. In vivo studies demonstrated that survival of mice bearing experimental tumors was improved by administration of anti-STIP1 antibodies.

CONCLUSIONS

Our findings demonstrate that the cytosolic inhibition of STIP1 in tumor cells is feasible and provides a solid basis for further investigation of STIP1 as an intracellular cancer target. Our findings demonstrate that cytosolic inhibition of STIP1 in tumor cells is feasible and provide a solid basis for further exploration of STIP1 as an intracellular cancer target.

Chemical features of blood-borne TRG CDR3s associated with an increased overall survival in breast cancer

PURPOSE

Immunogenomics and earlier, pioneering studies, particularly by Whiteside and colleagues, have indicated a positive role for B-cells in breast cancer, as well as a positive role for gamma-delta T-cells. However, these studies have been completely limited to assessing breast cancer tumor tissue.

METHODS AND RESULTS

Our analyses here has shown that blood-borne T-cell receptor gamma (TRG) chain sequences were associated with greater overall survival, of particular note due to the comparative longevity of primary breast cancer patients, whereby assessments of disease-free, but rarely overall survival parameters are possible. Additional immunogenomics approaches narrowed the overall survival correlations to specific, TRG complementarity determining region-3, amino acid (AA) sequence chemical features, independently of many common, confounding variables in the breast cancer setting, such as estrogen or progesterone receptor status.

CONCLUSIONS

These results are discussed in the context of patient age and with regard to potential antigenic targets, based on the chemistry of the TRG CDR3 AA sequences associated with the higher survival rates.

GOLPH3 Promotes Cancer Growth by Interacting With STIP1 and Regulating Telomerase Activity in Pancreatic Ductal Adenocarcinoma

Overexpression of Golgi phosphoprotein 3 (GOLPH3) predicts poor prognosis and is a potential therapeutic target in pancreatic ductal adenocarcinoma (PDAC). However, its role and underlying molecular mechanisms in the progression of PDAC remain unknown. In the present study, using high-throughput bimolecular fluorescence complementation (BiFC) analysis, we identified that stress-inducible protein-1 (STIP1) interacts with GOLPH3 and confirmed the interaction using co-localization and co-immunoprecipitation. The levels of GOLPH3 and STIP1 in PDAC tissues and adjacent non-cancerous pancreatic tissues were determined using immunohistochemistry (IHC) and quantitative real-time reverse transcription PCR. Real-time Quantitative-telomere repeat amplification (Q-TRAP) was applied to detect relative telomerase activity, and cell proliferation was measured when small interfering RNAs targeting GOLPH3 or STIP1 were transfected into PDAC cell lines. BALB/c nude mice were used to assess tumor growth inhibition of BXPC3 cells stably transfected with GOLPH3 short hairpin RNA. In summary, GOLPH3 was found to interact with STIP1 and both proteins were overexpressed and co-localized in PDAC tissues and cell lines. Moreover, suppression of GOLPH3 expression using shRNAs in PANC1 and BXPC3 cells inhibited tumor cell proliferation both in vitro and in vivo. Mechanistically, GOLPH3 interacts with STIP1 to activate telomerase reverse transcriptase (hTERT) and telomerase activity by c-Myc, and then upregulates cell cycle-related signaling proteins, including cyclin D1, to promote tumor cell growth, suggesting that disrupting the interaction between STIP1 and GOLPH3 would be a promising new strategy to treat PDAC.

STIP1 down-regulation inhibits glycolysis by suppressing PKM2 and LDHA and inactivating the Wnt/β-catenin pathway in cervical carcinoma cells

AIMS

Glycolysis is an important process for cervical carcinoma development. Previous studies have indicated that stress-induced phosphoprotein 1 (STIP1) is associated with development of multiple tumors. Nevertheless, the role and mechanism of STIP1 in glycolysis of cervical carcinoma remain unclear.

MAIN METHODS

The association between STIP1 and survival probability and the correlation between STIP1 expression and pyruvate kinase M2 (PKM2) as well as lactate dehydrogenase isoform A (LDHA) levels in cervical carcinoma were analyzed via The Cancer Genome Atlas (TCGA). The expression of STIP1, PKM2, LDHA, and cytochrome c (Cyt C) was measured via western blot or quantitative reverse transcription polymerase chain reaction. Cell viability and apoptosis were examined via cell counting kit 8 and flow cytometry, respectively. Glycolysis was assessed via detection of glucose consumption and lactate production. The protein involved in the Wnt/β-catenin pathway was measured via western blot.

KEY FINDINGS

STIP1 abundance was elevated in cervical carcinoma cells. High expression of STIP1 indicated poor survival probability. Knockdown of STIP1 inhibited cervical carcinoma cell viability and promoted apoptosis. STIP1 expression was positively correlated with PKM2 and LDHA levels in cervical carcinoma. Silence of STIP1 inhibited glycolysis and decreased PKM2 and LDHA expression. Down-regulation of STIP1 repressed the Wnt/β-catenin pathway. Overexpression of β-catenin reversed the effect of STIP1 silence on viability, apoptosis, glycolysis, and levels of PKM2 and LDHA.

SIGNIFICANCE

STIP1 knockdown suppressed glycolysis in cervical carcinoma by inhibiting PKM2 and LDHA expression and activation of the Wnt/β-catenin pathway.

Mn-Doping-induced hierarchical petal growth of a flower-like 3D MOF assembled with black phosphorous nanosheets as an electrochemical aptasensor of human stress-induced phosphoprotein 1

Herein, we report the preparation of Mn-doped Ni-based metal-organic frameworks (Mn-MOF) with 3D hierarchical flower-like superstructures through solvothermal synthesis. The Mn-MOF was assembled with 2D black phosphorous nanosheets (BPNSs) to achieve novel 2D/3D BPNSs/Mn-MOF nanocomposites, followed by the direct coupling of methylene blue (MB)-labeled DNA aptamer on the interface of the nanocomposites-modified glassy carbon electrode (GCE). The aptamer/BPNSs/Mn-MOF/GCE platform was utilized for the capture and efficient detection of stress-induced phosphoprotein 1 (STIP1). Experimental results confirmed that Mn-doping-induced the hierarchical petal growth of the flower-like 3D MOF and its assembly with BPNSs. GCE surface modifications with various components were studied by measuring electrochemical curves. The morphologies, microstructures and spectra of products were characterized. The optimal conditions used for electrochemical measurements were assessed. A smart aptasensor was explored by the aptamer/BPNSs/Mn-MOF/GCE that had multiple attractive merits, including synergistic effects of components, porous superstructures of hierarchical flower-like 3D Mn-MOF and specific aptamer-target recognition. The merits endowed this aptasensor with selective and sensitive signal responses to STIP1 over interferences. This aptasensor enabled the efficient detection of STIP1 in a broad range of 2 × 10^-3-1 × 10⁴ ng mL^-1, accompanied by a low limit of detection of 1 pg mL^-1. This aptasensor realized the successful determination of STIP1 in practical samples, exhibiting high reliability and practicability.

The multiple functions of the co-chaperone stress inducible protein 1

Stress inducible protein 1 (STI1) is a co-chaperone acting with Hsp70 and Hsp90 for the correct client proteins' folding and therefore for the maintenance of cellular homeostasis. Besides being expressed in the cytosol, STI1 can also be found both in the cell membrane and the extracellular medium playing several relevant roles in the central nervous system (CNS) and tumor microenvironment. During CNS development, in association with cellular prion protein (PrP^c), STI1 regulates crucial events such as neuroprotection, neuritogenesis, astrocyte differentiation and survival. In cancer, STI1 is involved with tumor growth and invasion, is undoubtedly a pro-tumor factor, being considered as a biomarker and possibly therapeutic target for several malignancies. In this review, we discuss current knowledge and new findings on STI1 function as well as its role in tissue homeostasis, CNS and tumor progression.

Stress-induced phosphoprotein 1 promotes pancreatic cancer progression through activation of the FAK/AKT/MMP signaling axis

BACKGROUND

Dependent on the extent of adenosine triphosphate (ATP) hydrolysis and/or ATP/ADP exchange, the stress-induced phosphoprotein 1 (STIP1) mediates molecular interaction and complex formation between the molecular chaperones heat shock protein (Hsp)70 and Hsp90. The overexpression of STIP1 is increasingly being documented in various human malignancies, including ovarian, cholangiocellular, renal and gastric cancers. However, the role of STIP1 in pancreatic cancer (PANC) and probable molecular mechanism remains largely unexplored.

METHODS & RESULTS

In the present study, using clinical samples (n = 88) and human PANC cell lines PANC-1, Capan-2, SW1990, and BxPC-3, we demonstrated that STIP1 is aberrantly expressed in human PANC tissues or cell lines compared to adjacent non-tumor pancreas samples or human pancreatic duct epithelial cells (HPDEC), respectively. Clinicopathological correlation studies revealed significant positive correlation between high STIP1 expression and lymph node involvement (p = 0.001), cancer metastasis (p = 0.002), microvascular invasion (p = 0.002), advance TNM stage (p = 0.024), perineural invasion (PNI; p = 0.013), and cancer-related death (p = 0.002) among patients with PANC. Univariate and multivariate analyses indicate that STIP1overexpression is an independent prognostic factor of PANC. Furthermore, STIP1 knockdown significantly inhibit the migration and invasive ability of PANC-1 and SW1990 cells, while downregulating N-cadherin and Vimentin, but upregulating E-cadherin mRNA expression levels, concurrently. We also demonstrated that STIP1 knockdown suppressed p-FAK, p-AKT, MMP2, MMP9, and Slug protein and mRNA expression levels, thus, indicating, at least in part, a role for STIP1 in the activation of FAK/AKT/MMP signaling.

CONCLUSION

Taken together, our results demonstrate a critical role for STIP1 in cancer metastasis, disease progression and poor prognosis, as well as, provide evidence suggestive of the therapeutic efficacy of STIP1-mediated targeting of the FAK/AKT/MMP signaling axis in patients with PANC.

Cancer protein biomarker discovery based on nucleic acid aptamers

Identification of biomarkers is essential for diagnosis, targeted therapy and prognosis evaluation of diseases, especially cancers. Currently, the number of ideal clinical biomarkers is still limited partially because of lacking efficient methods in biomarker discovery. Nucleic acid aptamers are artificial single-stranded DNA or RNA sequences that can selectively bind to various targets with high specificity and affinity. Moreover, aptamers possess desirable advantages, including easy synthesis, convenient modification, relative chemical stability and low immunogenicity. Recently, different aptamer-based strategies have been developed to facilitate the discovery of biomarkers. Based on cell-SELEX technology, the selected aptamers can be used to identify cell-surface protein biomarkers of different cancer cells. SOMAscan can analyze thousands of proteins of different biological samples, which becomes a multiplexed protein biomarker discovery platform. Additionally, secreted protein biomarkers can be discovered by aptamers screened through secretome SELEX. In order to facilitate the identification of target proteins, several covalent cross-linking strategies have been developed, such as aptamer-based affinity labeling (ABAL), DNA-templated aptamer and protein-aptamer template (PAT). In this review, we mainly highlight the emerging nucleic acid aptamer-based biomarker discovery strategies and demonstrate their unique technological advantages in discovering cancer biomarkers. The challenges and perspectives of aptamer-based methods are also discussed.