Eight proteins play critical roles in RCC with bone metastasis via mitochondrial dysfunction

Iron homeostasis and ferroptosis in human diseases: mechanisms and therapeutic prospects

Iron, an essential mineral in the body, is involved in numerous physiological processes, making the maintenance of iron homeostasis crucial for overall health. Both iron overload and deficiency can cause various disorders and human diseases. Ferroptosis, a form of cell death dependent on iron, is characterized by the extensive peroxidation of lipids. Unlike other kinds of classical unprogrammed cell death, ferroptosis is primarily linked to disruptions in iron metabolism, lipid peroxidation, and antioxidant system imbalance. Ferroptosis is regulated through transcription, translation, and post-translational modifications, which affect cellular sensitivity to ferroptosis. Over the past decade or so, numerous diseases have been linked to ferroptosis as part of their etiology, including cancers, metabolic disorders, autoimmune diseases, central nervous system diseases, cardiovascular diseases, and musculoskeletal diseases. Ferroptosis-related proteins have become attractive targets for many major human diseases that are currently incurable, and some ferroptosis regulators have shown therapeutic effects in clinical trials although further validation of their clinical potential is needed. Therefore, in-depth analysis of ferroptosis and its potential molecular mechanisms in human diseases may offer additional strategies for clinical prevention and treatment. In this review, we discuss the physiological significance of iron homeostasis in the body, the potential contribution of ferroptosis to the etiology and development of human diseases, along with the evidence supporting targeting ferroptosis as a therapeutic approach. Importantly, we evaluate recent potential therapeutic targets and promising interventions, providing guidance for future targeted treatment therapies against human diseases.

Identify CTBP1-DT as an immunological biomarker that promotes lipid synthesis and apoptosis resistance in KIRC

Recently, mounting evidence has highlighted the essential function of the C-terminal binding protein-1 divergent transcript (CTBP1-DT) in malignancies. However, its role in kidney renal clear cell carcinoma (KIRC) remains largely unknown. Our study aimed to identify the potential function of CTBP1-DT in KIRC. RT-qPCR, Kaplan-Meier survival analysis, Cox regression analysis, and nomogram analysis were utilized to determine the expression and effects of CTBP1-DT on survival. The subcellular localization of CTBP1-DT was determined using RNA fluorescence in situ hybridization (FISH). To investigate the functions of CTBP1-DT in regulating KIRC cell proliferation, migration, invasion, lipid synthesis, and apoptosis, we conducted CCK8, EdU, Transwell, and Oil Red O staining and cell apoptosis staining assays. The relationships between CTBP1-DT and the tumor microenvironment were investigated with multiple bioinformatics analysis algorithms and databases, including CYBERSORT, TIMER2, Spearman correlation test, tumor mutation burden (TMB), microsatellite instability (MSI), and immunophenoscore (IPS). According to our results, CTBP1-DT is a lncRNA located in the nucleus that is significantly upregulated in KIRC and is correlated with better clinical outcomes. Downregulating CTBP1-DT inhibited cell viability, migration, invasion, and lipid synthesis but triggered cell apoptosis. Additionally, we explored the potential effect of CTBP1-DT in regulating immune cell infiltration in KIRC and other malignancies. Furthermore, CTBP1-DT could be used to predict the effectiveness of targeted drugs and immune checkpoint inhibitors. In conclusion, we identified CTBP1-DT as a potential immunological biomarker and discovered the potential role of CTBP1-DT in regulating lipid synthesis and apoptosis resistance.

The Role of the PAX Genes in Renal Cell Carcinoma

Renal cell carcinoma (RCC) is a significant oncological challenge due to its heterogeneous nature and limited treatment options. The PAX developmental gene family encodes nine highly conserved transcription factors that play crucial roles in embryonic development and organogenesis, which have been implicated in the occurrence and development of RCC. This review explores the molecular landscape of RCC, with a specific focus on the role of the PAX gene family in RCC tumorigenesis and disease progression. Of the various RCC subtypes, clear cell renal cell carcinoma (ccRCC) is the most prevalent, characterized by the loss of the von Hippel-Lindau (VHL) tumor suppressor gene. Here, we review the published literature on the expression patterns and functional implications of PAX genes, particularly PAX2 and PAX8, in the three most common RCC subtypes, including ccRCC, papillary RCC (PRCC), and chromophobe RCC (ChRCC). Further, we review the interactions and potential biological mechanisms involving PAX genes and VHL loss in driving the pathogenesis of RCC, including the key signaling pathways mediated by VHL in ccRCC and associated mechanisms implicating PAX. Lastly, concurrent with our update regarding PAX gene research in RCC, we review and comment on the targeting of PAX towards the development of novel RCC therapies.

Clinical Implications of a Six-Protein Signature in Bone Metastasis of Renal Cell Carcinoma

Bone metastases is prevalent from renal cell carcinoma (RCC) with poor quality of life and prognosis. Our previous proteomics analysis identified dysregulated proteins in the bone-tropism RCC cells. In this study, we further examined the clinical implications of these proteins using multiple clinical cohorts. We identified 6 proteins with significant upregulation in RCC tumor tissue in comparing to tumor adjacent normal tissue (p<0.05). High expression of these 6 protein-encoding genes significantly correlates with a poor survival in the TCGA-KIRC (Kidney renal clear cell carcinoma) cohort (log-rank test p=2.7e-05), and they all individually had a reverse-correlation with the gene expression of VHL and PBRM1 (p<0.001), and positive-correlation with the expression of VEGFA (p<0.001). Further gene set variation analysis (GSVA) revealed positive correlation with Th17 cells enrichment and negative CD8 T cell infiltration in the RCC tumor microenvironment. High expression of these 6 genes in pretreatment tumors favors longer overall survival (OS)(p=0.027) in anti-PDL1 treated patients (n=428). We treated one humeral metastases RCC patient with the anti-PDL1 antibody drug atezolizumab after examined the elevated expression of the 6 proteins in his nephrectomy tumor tissue, the tumor at the fracture site shrunk remarkably after four courses of treatment. These results altogether suggest a clinical implication of the 6-protein signature in RCC bone metastasis prognosis and response to immune-checkpoint inhibitor treatment.

MicroRNA-155 and cancer metastasis: Regulation of invasion, migration, and epithelial-to-mesenchymal transition

Among the leading causes of death globally has been cancer. Nearly 90% of all cancer-related fatalities are attributed to metastasis, which is the growing of additional malignant growths out of the original cancer origin. Therefore, a significant clinical need for a deeper comprehension of metastasis exists. Beginning investigations are being made on the function of microRNAs (miRNAs) in the metastatic process. Tiny non-coding RNAs called miRNAs have a crucial part in controlling the spread of cancer. Some miRNAs regulate migration, invasion, colonization, cancer stem cells' properties, the epithelial-mesenchymal transition (EMT), and the microenvironment, among other processes, to either promote or prevent metastasis. One of the most well-conserved and versatile miRNAs, miR-155 is primarily distinguished by overexpression in a variety of illnesses, including malignant tumors. It has been discovered that altered miR-155 expression is connected to a number of physiological and pathological processes, including metastasis. As a result, miR-155-mediated signaling pathways were identified as possible cancer molecular therapy targets. The current research on miR-155, which is important in controlling cancer cells' invasion, and metastasis as well as migration, will be summarized in the current work. The crucial significance of the lncRNA/circRNA-miR-155-mRNA network as a crucial regulator of carcinogenesis and a player in the regulation of signaling pathways or related genes implicated in cancer metastasis will be covered in the final section. These might provide light on the creation of fresh treatment plans for controlling cancer metastasis.

Skeletal-Related Events in Renal Cell Carcinoma: Prediction With Alkaline Phosphatase (ALP), C-reactive Protein (CRP), Haemoglobin (Hb) and Erythrocyte Sedimentation Rate (ESR) (A.C.H.E.) Score for Risk Stratification

Introduction  Skeletal metastasis is catastrophic in patients with renal cell carcinoma (RCC), leading to skeletal-related events (SRE) such as nerve entrapment, hypercalcemia and even pathological fractures, which may require surgical intervention. The nature of the bone metastasis in advanced RCC is large, destructive, hyper-vascular and mostly lytic. The present retrospective analysis aims to identify potential risk factors for predicting SREs in advanced RCC with bone metastasis. Methods The clinical data of 42 patients with RCC and bone metastasis and at least one episode of SRE were reviewed, and the correlations between erythrocyte sedimentation rate (ESR), alkaline phosphatase (ALP), C-reactive protein (CRP), haemoglobin (Hb), carcinoembryonic antigen (CEA) and bone metastases were analysed. Risk factors were identified by multivariate logistic regression analysis. Bone metastasis was diagnosed on a bone scan. The receiver operating characteristic (ROC) curve calculated the cut-off value of the independent correlation factors. Results The areas under the ROC curve for ALP, Hb, CRP, and ESR were 0.84, 0.76, 0.86 and 0.88, respectively, suggesting excellent discriminatory capability of ALP, CRP, ESR and sufficient discriminative ability of Hb in predicting bone metastasis. Multivariate logistic regression analysis showed ALP, CRP, Hb and ESR associated with SRE and skeletal metastasis. Conclusion We propose that an A.C.H.E. score encompassing ALP, CRP, Hb, and ESR are potential risk factors for developing SRE and concomitant bone metastasis in advanced RCC patients. For new RCC patients, if values of ALP >128 U/L, CRP ≥74 mg/L, Hb <11.5 g/L, and ESR ≥55 mm/hr are detected, intensive monitoring and bone scanning are warranted as these cases are at a higher risk of skeletal events.

Hypermethylation of mitochondrial DNA facilitates bone metastasis of renal cell carcinoma

Kidney cancers including clear cell carcinoma (RCC) are identified with very vulnerable mitochondria DNA (mtDNA) and frequent epigenetic aberrations. Bone metastasis from RCC is prevalent and destructive. Bone marrow contains a quite hypoxic microenvironment that usually insitigate 50% of hypermethylation events in conferring a selective advantage for tumor growth. We hypothesized that hypermethylation of mtDNA in RCC cells would significantly contribute to bone metastatic tumor progression. Methylation-specific polymerase chain reaction assay (MSP) was adopted to measure the methylation status of D-loop region of mtDNA in 15 pairs of bone metastatic and primary RCC as well as tumor adjescent normal kidney tissues. mtDNA copy number was examined by the real-time quantitative polymerase chain reaction (qPCR). Western blotting analysis was used to measure the accumulation of several DNA methyltransferases (DNMTs) in the mitochondria and nucleus fractions of bone metastatic RCC cells. mRNA expression of mitochondria encoded genes was examined by RT-PCR. Reactive oxygen species (ROS), mitochondrial membrane potential and ATP content were measured using in vitro cells treated with de-methylation drug 5-Azacytidine (5-Aza). Non-invasive bioluminescent imaging was performed to monitor tumor occurrence in skeleton in mice. Our results showed that the D-loop region in bone metastatic tumor cells was markedly hypermethylated than those in primary RCC tumor cells, that is associated with a decreased mtDNA copy number and accumulation of DNMT1 in the mitochondria. The bone-tropism tumor colonization and progression of RCC cells was significantly suppressed by demethylating the D-loop region of mtDNA and reducing the intracellular level of ROS and ATP by 5-Aza treatment. In conclusion, our study provided a direct association between hypermethylation of mtDNA in RCC with bone metastastic tumor growth.

KLF2 inhibits cancer cell migration and invasion by regulating ferroptosis through GPX4 in clear cell renal cell carcinoma

The metastatic dissemination and underlying mechanisms of clear cell renal cell carcinoma (ccRCC) remain insufficiently understood. In this study, we identified the essential role of KLF2 in suppressing the metastasis of ccRCC. Downregulation of KLF2 detected by immunohistochemistry in primary metastatic ccRCC was remarkably related to poor clinical outcomes. Overexpression of KLF2 in vitro inhibited growth, migration and invasion of RCC cells. Analysis of clinical specimens revealed that there is a close correlation between KLF2 and GPX4 in ccRCC. Mechanistically, KLF2 deficiency is sufficient to inhibit ferroptosis on account of the impairment of transcriptional repression of GPX4 and thus promotes the migration and invasion of RCC cells. Reverting KLF2 expression in vivo decreased pulmonary metastatic lesions and prolonged life span of mice, whereas GPX4 overexpression reversed these properties. Overall, our results established a novel critical pathway that drives human ccRCC invasion and metastasis, which could be a promising target regarding to the therapies of advanced ccRCC in the clinic.

Potential prognostic biomarkers related to immunity in clear cell renal cell carcinoma using bioinformatic strategy

The clear cell renal cell carcinoma (ccRCC) is the main pathological subtype of renal cell carcinoma. Immune system evasion, one hallmark of cancer, contributes to cancer cells in escaping from the attack of immune cells. In order to identify potential prognostic biomarkers in ccRCC patients and immune cells fraction, we collected and downloaded profiles from The Cancer Genome Atlas (TCGA) database and Gene Expression Omnibus (GEO) database. We obtained 2 modules significantly associated with tumor stage and immune cells; functional enrichment analysis showed that genes in the module ‘yellow’ were significantly enriched in proteins targeting to membrane and ribosome, as well as the oxidative phosphorylation pathway, while genes in the module ‘green’ mainly participate in molecular functions associated with immunity like activation of T cells. Four LncRNAs (LINC00472, AL590094.1, AL365203.3, and AC147651.3) and RPL27A and RPL22L1 in the module ‘yellow’ and two lncRNAs (LINC00426 and AC129507.2) and five protein-coding genes (CSF1, NOD2, ITGAE, CD7, and PDCD1) in the module ‘green’ represented independent prognostic values in patients with ccRCC. Expression of LINC0042, NOD2, CD7, and PDCD1 were significantly correlated with ratio of immune cells (like T cells CD8 and resting mast cells). LINC00426, with significant correlation with immune cell fraction, shows potential prognostic value in ccRCC patients. Our findings provide a strategy in exploring biomarkers with prognostic significance and significant association with the fraction of immune cells.

A lncRNA TCL6-miR-155 Interaction Regulates the Src-Akt-EMT Network to Mediate Kidney Cancer Progression and Metastasis

Metastasis is the leading cause of mortality from kidney cancer, and understanding the underlying mechanism of this event will provide better strategies for its management. Here we investigated the biological, functional, and clinical significance of lncTCL6 and its interacting miR-155 in clear cell renal cell carcinoma (ccRCC). We employed a comprehensive approach to investigate the lncTCL6-miR-155-Src/Akt-mediated epithelial-to-mesenchymal transition (EMT) pathway as a novel regulatory mechanism in ccRCC progression. Expression analyses revealed that lncTCL6 is downregulated in ccRCC compared with normal tissues. Overexpression of lncTCL6 in ccRCC cell lines impaired their oncogenic functions, such as cell proliferation and migration/invasion, and induced cell-cycle arrest and apoptosis; conversely, depletion of lncTCL6 rescued these phenotypic effects. Furthermore, lncTCL6 directly interacted with miR-155. Unlike lncTCL6, miR-155 was overexpressed in ccRCC. Stable knockdown of miR-155 phenocopied the effects of lncTCL6 overexpression. Conversely, reconstitution of miR-155 and suppression of lncTCL6 in noncancerous renal cell HK2 induced tumorigenic characteristics. Patients with higher expression of lncTCL6 and lower expression of miR-155 had better survival probability. When overexpressed, lncTCL6 recruited STAU1 and mediated decay of Src mRNA, followed by a marked downregulation of an integrated network of Src target genes involved in migration, invasion, and EMT. However, the interaction between miR-155 and lncTCL6 attenuated the regulatory role of lncTCL6 on Src-mediated EMT. In conclusion, this study is the first report documenting the lncTCL6-miR155-Src/Akt/EMT network as a novel regulatory mechanism in aggressive ccRCC and a promising therapeutic target to inhibit renal cancer. SIGNIFICANCE: This study's investigation of noncoding RNA interactions in renal cell carcinoma identify miRNA-155-lncRNA TCL6-mediated regulation of the Src-Akt-EMT network as a novel mechanism of disease progression and metastasis.

Personal Medicine and Bone Metastases: Biomarkers, Micro-RNAs and Bone Metastases

Bone metastasis is a major cause of morbidity within solid tumours of the breast, prostate, lung and kidney. Metastasis to the skeleton is associated with a wide range of complications including bone fractures, spinal cord compression, hypercalcaemia and increased bone pain. Improved treatments for bone metastasis, such as the use of anti-bone resorptive bisphosphonate agents, within post-menopausal women have improved disease-free survival; however, these treatments are not without side effects. There is thus a need for biomarkers, which will predict the risk of developing the spread to bone within these cancers. The application of molecular profiling techniques, together with animal model systems and engineered cell-lines has enabled the identification of a series of potential bone-metastasis biomarker molecules predictive of bone metastasis risk. Some of these biomarker candidates have been validated within patient-derived samples providing a step towards clinical utility. Recent developments in multiplex biomarker quantification now enable the simultaneous measurement of up to 96 micro-RNA/protein molecules in a spatially defined manner with single-cell resolution, thus enabling the characterisation of the key molecules active at the sites of pre-metastatic niche formation as well as tumour-stroma signalling. These technologies have considerable potential to inform biomarker discovery. Additionally, a potential future extension of these discoveries could also be the identification of novel drug targets within cancer spread to bone. This chapter summarises recent findings in biomarker discovery within the key bone metastatic cancers (breast, prostate, lung and renal cell carcinoma). Tissue-based and circulating blood-based biomarkers are discussed from the fields of genomics, epigenetic regulation (micro-RNAs) and protein/cell-signalling together with a discussion of the potential future development of these markers towards clinical development.

Network as a Biomarker: A Novel Network-Based Sparse Bayesian Machine for Pathway-Driven Drug Response Prediction

With the advances in different biological networks including gene regulation, gene co-expression, protein–protein interaction networks, and advanced approaches for network reconstruction, analysis, and interpretation, it is possible to discover reliable and accurate molecular network-based biomarkers for monitoring cancer treatment. Such efforts will also pave the way toward the realization of biomarker-driven personalized medicine against cancer. Previously, we have reconstructed disease-specific driver signaling networks using multi-omics profiles and cancer signaling pathway data. In this study, we developed a network-based sparse Bayesian machine (NBSBM) approach, using previously derived disease-specific driver signaling networks to predict cancer cell responses to drugs. NBSBM made use of the information encoded in a disease-specific (differentially expressed) network to improve its prediction performance in problems with a reduced amount of training data and a very high-dimensional feature space. Sparsity in NBSBM is favored by a spike and slab prior distribution, which is combined with a Markov random field prior that encodes the network of feature dependencies. Gene features that are connected in the network are assumed to be both relevant and irrelevant to drug responses. We compared the proposed method with network-based support vector machine (NBSVM) approaches and found that the NBSBM approach could achieve much better accuracy than the other two NBSVM methods. The gene modules selected from the disease-specific driver networks for predicting drug sensitivity might be directly involved in drug sensitivity or resistance. This work provides a disease-specific network-based drug sensitivity prediction approach and can uncover the potential mechanisms of the action of drugs by selecting the most predictive sub-networks from the disease-specific network.

Expression of mitochondrial dynamics markers during melanoma progression: Comparative study of head and neck cutaneous and mucosal melanomas

BACKGROUND

Head and neck mucosal melanomas (MMs) are rare tumors with adverse outcomes and poorer prognoses than their more common cutaneous counterparts (cutaneous melanomas-CMs). Few studies have compared the expression of mitochondrial dynamic markers in these tumors. This study aimed to assess the correlations of mitochondrial markers with melanoma progression and their potential as predictors of lymph node involvement and distant metastasis.

METHODS

Immunohistochemistry against anti-mitochondrial (AMT), dynamin-related protein 1 (DRP1), mitochondrial fission protein 1 (FIS1), mitofusin-1 (MFN1), and mitofusin-2 (MFN2) antibodies was performed in 112 cases of head and neck CM and MM. A Cox regression multivariate model was used to assess the correlation of AMT, FIS1, and MFN2 expressions considering the risk for nodal and distant metastasis.

RESULTS

All markers studied presented higher staining in tumor cells than normal adjacent tissues. Higher mitochondrial content was observed in MM than in CM, and it was significantly associated with nodal metastasis in oral melanomas. Both FIS1 and DRP1 expressions were related to advanced Clark's levels in CM, and they were overexpressed in oral melanomas. Moreover, increased immunoexpression of MFN2 was significantly associated with a higher risk of metastasis in CM, and it was also overexpressed in sinonasal melanomas.

CONCLUSIONS

Our results suggest that mitochondrial fission and fusion processes can play an important role during multiple stages of tumorigenesis and the development of nodal and distant metastasis in cutaneous and mucosal melanomas.

Down-regulation of transient receptor potential melastatin member 7 prevents migration and invasion of renal cell carcinoma cells via inactivation of the Src and Akt pathway

Purpose

Transient receptor potential melastatin member 7 (TRPM7), an ion channel and serine/threonine protein kinase, has been linked with distinct human malignancies. However, the role of TRPM7 in renal cell carcinoma (RCC) has not been investigated. The aim of this study is to determine whether TRPM7 regulates the migration and invasion of RCC cells. Its relationship with signal transduction pathways was also studied.

Materials and Methods

The human RCC cell lines ACHN and SN12C were chosen for this study. The molecular mechanisms of TRPM7 action were studied using Western blot analysis and small interfering RNA (siRNA)-based knockdown. The effect of TRPM7 knockdown on RCC cells was measured by using Transwell invasion and wound healing migration assays.

Results

siRNA-induced silencing of TRPM7 notably decreased the migration and invasion of ACHN and SN12C RCC cells. The phosphorylation levels of Src in both cells were obviously reduced after TRPM7 silencing compared with that of the control ACHN and SN12C cells. Furthermore, the phosphorylation levels of Akt were greatly decreased in ACHN cells after siRNA-induced knockdown of TRPM7. Additionally, the treatment of cells with Src and Akt inhibitors clearly limited the migration and invasion of RCC cells.

Conclusions

Our data show that TRPM7 regulated ACHN and SN12C RCC cell invasion via the Src/Akt signaling pathway. Therefore, targeting the Src/Akt signaling pathway and/or the expression or function of TRPM7 could be a potential beneficial treatment for patients with RCC.

[Quantitative and comparative proteomics analysis in clear cell renal cell carcinoma and adjacent noncancerous tissues by 2-D DIGE]

OBJECTIVE

To identify specific protein markers for renal cell carcinoma detection and diagnosis, as well as develop new potential therapeutic targets of the disease.

METHODS

We used two-dimensional difference in-gel electrophoresis (2-D DIGE) technique conjunction with mass spectrometry (MS) for the identification of significant differentially expressed proteins between 15cases of paired clear cell renal cell carcinoma (ccRCC) and adjacent normal renal tissues. The protein spots were considered as differentially expressed if a 1.5-fold altered expression level was observed (Student's t test, P value<0.05).

RESULTS

Of the 27 differentially expressed protein spots, 26 proteins were successfully identified. 11 proteins up-regulated in renal cell carcinoma,15 proteins down-regulated. Among them Short/branched chain specific acyl-CoA dehydrogenase, mitochondrial (ACDSB), Aldose 1-epimerase (GALM), Peroxiredoxin-4 (PRDX4), Macrophage-capping protein (CAPG), Beta-defensin 107 (D107A), Microfibril-associated glycoprotein 4 (MFAP4) were first time screening as new differential expressed proteins by protomic study in renal cell carcinoma.

CONCLUSIONS

2-D DIGE is a useful technique for screening and analysis differential expressed proteins in renal cell carcinoma. These new differently expressed proteins may be useful for development new molecular markers for the tumor.

[Quantitative and comparative proteomics analysis in clear cell renal cell carcinoma and adjacent noncancerous tissues by 2-D DIGE]

OBJECTIVE

To identify specific protein markers for renal cell carcinoma detection and diagnosis, as well as develop new potential therapeutic targets of the disease.

METHODS

We used two-dimensional difference in-gel electrophoresis (2-D DIGE) technique conjunction with mass spectrometry (MS) for the identification of significant differentially expressed proteins between 15cases of paired clear cell renal cell carcinoma (ccRCC) and adjacent normal renal tissues. The protein spots were considered as differentially expressed if a 1.5-fold altered expression level was observed (Student's t test, P value<0.05).

RESULTS

Of the 27 differentially expressed protein spots, 26 proteins were successfully identified. 11 proteins up-regulated in renal cell carcinoma,15 proteins down-regulated. Among them Short/branched chain specific acyl-CoA dehydrogenase, mitochondrial (ACDSB), Aldose 1-epimerase (GALM), Peroxiredoxin-4 (PRDX4), Macrophage-capping protein (CAPG), Beta-defensin 107 (D107A), Microfibril-associated glycoprotein 4 (MFAP4) were first time screening as new differential expressed proteins by protomic study in renal cell carcinoma.

CONCLUSIONS

2-D DIGE is a useful technique for screening and analysis differential expressed proteins in renal cell carcinoma. These new differently expressed proteins may be useful for development new molecular markers for the tumor.

Autocrine and paracrine STIP1 signaling promote osteolytic bone metastasis in renal cell carcinoma

Bone metastases are responsible for some of the most devastating complications of renal cell carcinoma (RCC). However, pro-metastatic factors leading to the highly osteolytic characteristics of RCC bone metastasis have barely been explored. We previously developed novel bone-seeking RCC cell lines by the in vivo selection strategy and performed a comparative proteome analysis on their total cell lysate. Here, we focused on STIP1 (stress-induced phosphoprotein 1), the high up-regulated protein in the bone-seeking cells, and explored its clinical relevance and functions in RCC bone metastasis. We observed high levels of both intracellular and extracellular STIP1 protein in bone metastatic tissue samples. Elevated STIP1 mRNA in the primary RCC tumors remarkably correlated with worse clinical outcomes. Furthermore, both human recombinant STIP1 protein and anti-STIP1 neutralizing antibody were used in the functional studies. We found that 1) STIP1 protein on the extracellular surface of tumor cells promoted the proliferation and migration/invasion of RCC tumor cells through the autocrine STIP1-ALK2-SMAD1/5 pathway; and 2) STIP1 protein secreted into the extracellular tumor stromal area, promoted the differentiation of osteoclasts through the paracrine STIP1-PrPc-ERK1/2 pathway. Increased cathepsin K (CTSK), the key enzyme secreted by osteoclasts to degrade collagen and other matrix proteins during bone resorption was further detected in the differentiated osteoclasts. These results provide evidence of the great potential of STIP1 as a novel biomarker and therapeutic target in RCC bone metastasis.

Tetrandrine inhibits migration and invasion of human renal cell carcinoma by regulating Akt/NF-κB/MMP-9 signaling

Renal cell carcinoma (RCC) is known as one of the most lethal malignancies in the urological system because of its high incidence of metastasis. Tetrandrine (Tet), a traditional Chinese herbal medicine, exerts a potent anti-cancer effect in a variety of cancer cells. However, the anti-metastatic effect of Tet and its possible mechanism in RCC is still unclear. The present study revealed that Tet significantly suppressed the migration and invasion of RCC 786-O and 769-P cells in vitro. Mechanistically, the protein levels of matrix metalloproteinases 9 (MMP-9), phosphorylated PI3K, PDK1, Akt and NF-κB were markedly reduced after Tet treatment. Moreover, co-treatment with LY294002 (PI3K inhibitor) could further enhance the Tet-inhibited migration and invasion, and the NF-κB and MMP-9 protein levels were further decreased. Similar results were observed after PDTC (NF-κB inhibitor) co-treatment. Conversely, SC79, an Akt activator, could partially reverse the anti-metastatic effects of Tet, accompanied by the restoration of NF-κB and MMP-9 protein levels. In conclusion, the current results indicated that Tet inhibited migration and invasion of RCC partially by regulating Akt/NF-κB/MMP-9 signaling pathway, suggesting that Tet may be a potential therapeutic candidate against metastatic RCC.