Hypoxia, Hypoxia-inducible Transcription Factors, and Renal Cancer

Hypoxia-inducible factor 2α: a novel target in gliomas

Hypoxia is an important contributor to aggressive behavior and resistance mechanisms in glioblastoma. Upregulation of hypoxia inducible transcription factors (HIFs) is the primary adaptive cellular response to a hypoxic environment. While HIF1α has been widely studied in cancer, HIF2α offers a potentially more specific and appealing target in glioblastoma given expression in glioma stem cells and not normal neural progenitors, activation in states of chronic hypoxia and expression that correlates with glioma patient survival. A first-in-class HIF2α inhibitor, PT2385, is in clinical trials for renal cell carcinoma, and provides the first opportunity to therapeutically target this important pathway in glioma biology.

Bioinformatic identification of key genes and analysis of prognostic values in clear cell renal cell carcinoma

The present study aimed to identify new key genes as potential biomarkers for the diagnosis, prognosis or targeted therapy of clear cell renal cell carcinoma (ccRCC). Three expression profiles (GSE36895, GSE46699 and GSE71963) were collected from Gene Expression Omnibus. GEO2R was used to identify differentially expressed genes (DEGs) in ccRCC tissues and normal samples. The Database for Annotation, Visualization and Integrated Discovery was utilized for functional and pathway enrichment analysis. STRING v10.5 and Molecular Complex Detection were used for protein-protein interaction (PPI) network construction and module analysis, respectively. Regulation network analyses were performed with the WebGestal tool. UALCAN web-portal was used for expression validation and survival analysis of hub genes in ccRCC patients from The Cancer Genome Atlas (TCGA). A total of 65 up- and 164 downregulated genes were identified as DEGs. DEGs were enriched with functional terms and pathways compactly related to ccRCC pathogenesis. Seventeen hub genes and one significant module were filtered out and selected from the PPI network. The differential expression of hub genes was verified in TCGA patients. Kaplan-Meier plot showed that high mRNA expression of enolase 2 (ENO2) was associated with short overall survival in ccRCC patients (P=0.023). High mRNA expression of cyclin D1 (CCND1) (P<0.001), fms related tyrosine kinase 1 (FLT1) (P=0.004), plasminogen (PLG) (P<0.001) and von Willebrand factor (VWF) (P=0.008) appeared to serve as favorable factors in survival. These findings indicate that the DEGs may be key genes in ccRCC pathogenesis and five genes, including ENO2, CCND1, PLT1, PLG and VWF, may serve as potential prognostic biomarkers in ccRCC.

ERK and p38 Upregulation versus Bcl-6 Downregulation in Rat Kidney Epithelial Cells Exposed to Prolonged Hypoxia

Hypoxia is a common cause of kidney injury and a major issue in kidney transplantation. Mitogen-activated protein kinases (MAPKs) are involved in the cellular response to hypoxia, but the precise roles of MAPKs in renal cell reactions to hypoxic stress are not well known yet. This work was conducted to investigate the regulation of extracellular signal-regulated kinase-1 and -2 (ERK1/2) and p38 and their signaling-relevant molecules in kidney epithelial cells exposed to prolonged hypoxia. Rat kidney epithelial cells Normal Rat Kidney (NRK)-52E were exposed to hypoxic conditions (1% O₂) for 24 to 72 h. Cell morphology was examined by light microscopy, and cell viability was checked by 3-[4,5-dimethylthiazol-2-yl]-5-[3-carboxymethoxypheny]-2-[4-sulfophenyl]-2H-tetrazolium (MTS). The expression of ERK1/2 and p38 MAPK, as well as their signaling-related molecules, was measured by Western blot and real-time polymerase chain (RT-PCR) reaction. At the 1% oxygen level, cell morphology had no appreciable changes compared to the control up to 72 h of exposure under light microscopy, whereas the results of MTS showed a slight but significant reduction in cell viability after 72 h of hypoxia. On the other hand, ERK1/2 and p38 phosphorylation remarkably increased in these cells after 24 to 72 h of hypoxia. In sharp contrast, the expression of transcription factor B-cell lymphoma 6 (Bcl-6) was significantly downregulated in response to hypoxic stress. Other intracellular molecules relevant to the ERK1/2 and p38 signaling pathway, such as protein kinase A, protein kinase C, Bcl-2, nuclear factor erythroid 2-related factor 2, tristetraprolin, and interleukin-10(IL-10), had no significant alterations after 24 to 72 h of hypoxic exposure. We conclude that hypoxic stress increases the phosphorylation of both ERK1/2 and p38 but decreases the level of Bcl-6 in rat kidney epithelial cells.

Molecular and Metabolic Basis of Clear Cell Carcinoma of the Kidney

Renal cell carcinoma (RCC) is a heterogenous group of tumors, >70% of which belong to the category of clear cell carcinoma. In recent years, crucial advances have been made in our understanding of the molecular and metabolic basis of clear cell carcinoma. This tumor manifests significant alterations in the cellular metabolism, so that the tumor cells preferentially induce the hypoxia response pathway using aerobic glycolysis, rather than the normal oxidative phosphorylation for energy. Most of the clear cell carcinomas (sporadic as well as familial) have mutations and deletions in the VHL gene located at 3p (p3.25). Normally, pVHL plays a crucial role in the proteasomal degradation of hypoxia-inducible factors (HIF)1 and HIF2. Lack of a functioning pVHL owing to genetic alterations results in stabilization and accumulation of these factors, which promotes cell growth, cell proliferation, and angiogenesis, contributing to a neoplastic phenotype. Several other genes normally located adjacent to VHL (BAP1, SETD2, PBRM1) may also be lost. These are tumor suppressor genes whose loss not only plays a role in carcinogenesis but may also influence the clinical course of these neoplasms. In addition, interaction among a variety of other genes located at several different chromosomes may also play a role in the genesis and progression of clear cell carcinoma.

Hereditary renal cell carcinoma syndromes: diagnosis, surveillance and management

PURPOSE

Genetic factors have been implicated in the pathogenesis of renal cell carcinoma (RCC), with around 3% of cases having a family history. A greater knowledge of the genetics of inherited RCC has the potential to translate into novel therapeutic targets for sporadic RCC.

METHODS

A literature review was performed summarising the current knowledge on hereditary RCC diagnosis, surveillance and management.

RESULTS

Familial RCC is usually inherited in an autosomal dominant manner, although inherited RCC may present without a relevant family history. A number of familial RCC syndromes have been identified. Familial non-syndromic RCC is suspected when ≥ 2 relatives are affected in the absence of syndromic features, although clear diagnostic criteria are lacking. Young age at onset and bilateral/multicentric tumours are recognised characteristics which should prompt molecular genetic analysis. Surveillance in individuals at risk of inherited RCC aims to prevent morbidity and mortality via early detection of tumours. Though screening and management guidelines for some inherited RCC syndromes (e.g. von Hippel-Lindau disease, Birt-Hogg-Dube syndrome, hereditary leiomyomatosis) are well defined for rare cause of inherited RCC (e.g. germline BAP1 mutations), there is limited information regarding the lifetime RCC risks and the most appropriate screening modalities.

CONCLUSION

Increasing knowledge of the natural history and genetic basis has led to characterisation and tailored management of hereditary RCC syndromes. International data sharing of inherited RCC gene variant information may enable evidence-based improvements in the diagnosis, surveillance protocols and management of these rare conditions.

Generation of autochthonous mouse models of clear cell renal cell carcinoma: mouse models of renal cell carcinoma

Renal cell carcinoma (RCC) is one of the 10 most common cancers worldwide, and to date, a strong systemic therapy has not been developed to treat RCC, even with the remarkable modern advances in molecular medicine mostly due to our incomplete understanding of its tumorigenesis. There is a dire unmet need to understand the etiology and progression of RCC, especially the most common subtype, clear cell RCC (ccRCC), and to develop new treatments for RCC. Genetically engineered mouse (GEM) models are able to mimic the initiation, progression, and metastasis of cancer, thus providing valuable insights into tumorigenesis and serving as perfect preclinical platforms for drug testing and biomarker discovery. Despite substantial advances in the molecular investigation of ccRCC and monumental efforts that have been performed to try to establish autochthonous animal models of ccRCC, this goal has not been achieved until recently. Here we present a review of the most exciting progress relevant to GEM models of ccRCC.

Crosstalk between VEGFR and other receptor tyrosine kinases for TKI therapy of metastatic renal cell carcinoma

Clear cell renal cell carcinoma (ccRCC) is the most common subtype of renal cell carcinoma (RCC), and is frequently accompanied by the genetic features of von Hippel–Lindau (VHL) loss. VHL loss increases the expression of hypoxia-inducible factors (HIFs) and their targets, including epidermal growth factor (EGF), vascular endothelial growth factor (VEGF), and platelet-derived growth factor (PDGF). The primary treatment for metastatic RCC (mRCC) is molecular-targeted therapy, especially anti-angiogenic therapy. VEGF monoclonal antibodies and VEGF receptor (VEGFR) tyrosine kinase inhibitors (TKIs) are the main drugs used in anti-angiogenic therapy. However, crosstalk between VEGFR and other tyrosine kinase or downstream pathways produce resistance to TKI treatment, and the multi-target inhibitors, HIF inhibitors or combination strategies are promising strategies for mRCC. HIFs are upstream of the crosstalk between the growth factors, and these factors may regulate the expression of VEGR, EGF, PDGF and other growth factors. The frequent VHL loss in ccRCC increases HIF expression, and HIFs may be an ideal candidate to overcome the TKI resistance. The combination of HIF inhibitors and immune checkpoint inhibitors is also anticipated. Various clinical trials of programmed cell death protein 1 inhibitors are planned. The present study reviews the effects of current and potential TKIs on mRCC, with a focus on VEGF/VEGFR and other targets for mRCC therapy.

Follistatin-like protein 1 plays a tumor suppressor role in clear-cell renal cell carcinoma

BACKGROUND

We previously showed that the expression of follistatin-like protein 1 (FSTL1) was significantly down-regulated in metastatic clear-cell renal cell carcinoma (ccRCC). In this study, we aimed to characterize the role of FSTL1 in the development of ccRCC.

METHODS

The effects of FSTL1 on cell activity and cell cycle were investigated in ccRCC cell lines with altered FSTL1 expression. Gene expression microarray assays were performed to identify the major signaling pathways affected by FSTL1 knockdown. The expression of FSTL1 in ccRCC and its effect on postoperative prognosis were estimated in a cohort with 89 patients.

RESULTS

FSTL1 knockdown promoted anchorage-independent growth, migration, invasion, and cell cycle of ccRCC cell lines, whereas FSTL1 overexpression attenuated cell migration. FSTL1 knockdown up-regulated nuclear factor-κB (NF-κB) and hypoxia-inducible factor (HIF) signaling pathways, increased epithelial-to-mesenchymal transition, up-regulated interleukin-6 expression, and promoted tumor necrosis factor-α-induced degradation of NF-κB inhibitor (IκBα) in ccRCC cell lines. FSTL1 immunostaining was selectively positive in epithelial cytoplasm in the loop of Henle, and positive rate of FSTL1 was significantly lower in ccRCC tissues than in adjacent renal tissues (P < 0.001). The multivariate Cox regression analysis showed that the intratumoral FSTL1 expression conferred a favorable independent prognosis with a hazard ratio of 0.325 (95% confidence interval 0.118-0.894). HIF-2α expression was negatively correlated with FSTL1 expression in ccRCC specimens (r = - 0.229, P = 0.044). Intratumoral expression of HIF-2α, rather than HIF-1α, significantly predicted an unfavorable prognosis in ccRCC (log-rank, P = 0.038).

CONCLUSIONS

FSTL1 plays a tumor suppression role possibly via repressing the NF-κB and HIF-2α signaling pathways. To increase FSTL1 expression might be a candidate therapeutic strategy for metastatic ccRCC.

Suppression of homology-dependent DNA double-strand break repair induces PARP inhibitor sensitivity in VHL-deficient human renal cell carcinoma

The von Hippel-Lindau (VHL) tumor suppressor gene is inactivated in the vast majority of human clear cell renal carcinomas. The pathogenesis of VHL loss is currently best understood to occur through stabilization of the hypoxia-inducible factors, activation of hypoxia-induced signaling pathways, and transcriptional reprogramming towards a pro-angiogenic and pro-growth state. However, hypoxia also drives other pro-tumorigenic processes, including the development of genomic instability via down-regulation of DNA repair gene expression. Here, we find that DNA repair genes involved in double-strand break repair by homologous recombination (HR) and in mismatch repair, which are down-regulated by hypoxic stress, are decreased in VHL-deficient renal cancer cells relative to wild type VHL-complemented cells. Functionally, this gene repression is associated with impaired DNA double-strand break repair in VHL-deficient cells, as determined by the persistence of ionizing radiation-induced DNA double-strand breaks and reduced repair activity in a homology-dependent plasmid reactivation assay. Furthermore, VHL deficiency conferred increased sensitivity to PARP inhibitors, analogous to the synthetic lethality observed between hypoxia and these agents. Finally, we discovered a correlation between VHL inactivation and reduced HR gene expression in a large panel of human renal carcinoma samples. Together, our data elucidate a novel connection between VHL-deficient renal carcinoma and hypoxia-induced down-regulation of DNA repair, and identify potential opportunities for targeting DNA repair defects in human renal cell carcinoma.

[Mechanism and Prospect of Radiotherapy Combined with Apotatinib in the Treatment of Non-small Cell Lung Cancer]

非小细胞肺癌是危害人类生命健康的最常见的恶性肿瘤之一。大多数患者确诊时为晚期，不符合手术适应症，主要的治疗方法是放化疗联合。近年来，随着抗血管生成治疗恶性肿瘤理论的提出，阿帕替尼作为一种新型的抗肿瘤药物，与放疗联合具有协同作用。可能的机制包括使血管正常化，改善肿瘤内乏氧情况，调节促血管生成因子水平等。将阿帕替尼与放疗联合有望成为一种新的治疗策略应用于非小细胞肺癌的治疗中，提高肺癌的治疗效果。

Renal Cell Carcinoma: Molecular Aspects

Renal cell carcinoma is the most common form of the kidney cancer accounting for more than 85% of the cases of which clear cell renal cell carcinoma (ccRCC) is the major histological subtype. The central molecular signature for ccRCC pathogenesis is the biallelic inactivation of VHL gene due to the presence of mutations/hyper-methylation/complete gene loss, which results in the downstream HIF activation. These events lead to increased tyrosine kinase receptor signalling pathways (RAS/MEK/ERK pathway, PI3K/AKT/mTOR pathway and NF-κB pathway), which through their downstream effector proteins causes the cell to proliferate and migrate. Recent studies have shown that VHL inactivation alone is not sufficient to induce the tumor. Mutations in numerous other genes that codes for chromatin modifiers (PBRM1, SETD2 and BAP1) and signalling proteins (PTEN and mTOR) have been identified along with activation of alternate signalling pathways like STAT and Sonic Hedgehog (SHH) pathway. It has also been shown that STAT pathway also works cooperatively with HIF to enhance the tumor progression. However, SHH pathway reactivation resulted in tumor regardless of the VHL status, indicating the complex nature of the tumor at the molecular level. Therefore, understanding the complete aetiology of ccRCC is important for future therapeutics.

Large-scale genome-wide screening of circulating microRNAs in clear cell renal cell carcinoma reveals specific signatures in late-stage disease

Circulating miRNAs have shown great promises as noninvasive diagnostic and predictive biomarkers in several solid tumors. While the miRNA profiles of renal tumors have been extensively explored, knowledge of their circulating counterparts is limited. Our study aimed to provide a large-scale genome-wide profiling of plasma circulating miRNA in clear-cell renal cell carcinoma (ccRCC). Plasma samples from 94 ccRCC cases and 100 controls were screened for 754 circulating micro-RNAs (miRNA) by TaqMan arrays. Analyses including known risk factors for renal cancer-namely, age, sex, hypertension, obesity, diabetes, tobacco smoking and alcohol consumption-highlighted that circulating miRNA profiles were tightly correlated with the stage of the disease. Advanced tumors, characterized as stage III and IV, were associated with specific miRNA signatures that significantly differ from both controls and earlier stage ccRCC cases. Molecular pathway enrichment analyses of their gene targets showed high similarities with alterations observed in renal tumors. Plasma circulating levels of miR-150 were significantly associated with RCC-specific survival and could marginally improve the predictive accuracy of clinical parameters in our series, including age at diagnosis, sex and conventional staging. In summary, our results suggest that circulating miRNAs may provide insights into renal cell carcinoma progression.

Plasmatic miR-210, miR-221 and miR-1233 profile: potential liquid biopsies candidates for renal cell carcinoma

Renal cell carcinoma (RCC) represents a challenge for clinicians since the nonexistence of screening and monitoring tests contributes to the fact that one-third of patients are diagnosed with metastatic disease and 20–40% of the remaining patients will also develop metastasis. Modern medicine is now trying to establish circulating biomolecules as the gold standard of biomarkers. Among the molecules that can be released from tumor cells we can find microRNAs. The aim of this study was to evaluate the applicability of cancer-related miR-210, miR-218, miR-221 and miR-1233 as prognostic biomarkers for RCC. Patients with higher levels of miR-210, miR-221 and miR-1233 presented a higher risk of specific death by RCC and a lower cancer-specific survival. The addition of miR-210, miR-221 and miR-1233 plasma levels information improved the capacity to predict death by cancer in 8, 4% when compared to the current variables used by clinicians. We also verified that hypoxia stimulates the release of miR-210 and miR-1233 from HKC-8, RCC-FG2 and 786-O cell lines. These results support the addition of circulating microRNAs as prognostic biomarkers for RCC.

Epigenome Aberrations: Emerging Driving Factors of the Clear Cell Renal Cell Carcinoma

Clear cell renal cell carcinoma (ccRCC), the most common form of Kidney cancer, is characterized by frequent mutations of the von Hippel-Lindau (VHL) tumor suppressor gene in ~85% of sporadic cases. Loss of pVHL function affects multiple cellular processes, among which the activation of hypoxia inducible factor (HIF) pathway is the best-known function. Constitutive activation of HIF signaling in turn activates hundreds of genes involved in numerous oncogenic pathways, which contribute to the development or progression of ccRCC. Although VHL mutations are considered as drivers of ccRCC, they are not sufficient to cause the disease. Recent genome-wide sequencing studies of ccRCC have revealed that mutations of genes coding for epigenome modifiers and chromatin remodelers, including PBRM1, SETD2 and BAP1, are the most common somatic genetic abnormalities after VHL mutations in these tumors. Moreover, recent research has shed light on the extent of abnormal epigenome alterations in ccRCC tumors, including aberrant DNA methylation patterns, abnormal histone modifications and deregulated expression of non-coding RNAs. In this review, we discuss the epigenetic modifiers that are commonly mutated in ccRCC, and our growing knowledge of the cellular processes that are impacted by them. Furthermore, we explore new avenues for developing therapeutic approaches based on our knowledge of epigenome aberrations of ccRCC.

Renal cell carcinoma: new insights and challenges for a clinician scientist

There is a growing recognition of the complex interplay between renal cell cancer (RCC), kidney function, mechanical reduction of nephron mass, and systemic agents targeting the cancer. Earlier detection of RCC and rising life expectancy of cancer survivors places a greater emphasis on preservation of renal function after cancer resection and during systemic therapy. Unique adverse effects associated with RCC drugs not only help reveal cancer pathophysiology but also expand our knowledge of normal cell signaling and metabolism. In this review, we outline our current understanding of RCC biology and treatment, their bidirectional relationship with kidney function, and unmet research needs in this field.

HIF prolyl hydroxylase PHD3 regulates translational machinery and glucose metabolism in clear cell renal cell carcinoma

BACKGROUND

A key feature of clear cell renal cell carcinoma (ccRCC) is the inactivation of the von Hippel-Lindau tumour suppressor protein (pVHL) that leads to the activation of hypoxia-inducible factor (HIF) pathway also in well-oxygenated conditions. Important regulator of HIF-α, prolyl hydroxylase PHD3, is expressed in high amounts in ccRCC. Although several functions and downstream targets for PHD3 in cancer have been suggested, the role of elevated PHD3 expression in ccRCC is not clear.

METHODS

To gain insight into the functions of high PHD3 expression in ccRCC, we used PHD3 knockdown by siRNA in 786-O cells under normoxic and hypoxic conditions and performed discovery mass spectrometry (LC-MS/MS) of the purified peptide samples. The LC-MS/MS results were analysed by label-free quantification of proteome data using a peptide-level expression-change averaging procedure and subsequent gene ontology enrichment analysis.

RESULTS

Our data reveals an intriguingly widespread effect of PHD3 knockdown with 91 significantly regulated proteins. Under hypoxia, the response to PHD3 silencing was wider than under normoxia illustrated by both the number of regulated proteins and by the range of protein expression levels. The main cellular functions regulated by PHD3 expression were glucose metabolism, protein translation and messenger RNA (mRNA) processing. PHD3 silencing led to downregulation of most glycolytic enzymes from glucose transport to lactate production supported by the reduction in extracellular acidification and lactate production and increase in cellular oxygen consumption rate. Moreover, upregulation of mRNA processing-related proteins and alteration in a number of ribosomal proteins was seen as a response to PHD3 silencing. Further studies on upstream effectors of the translational machinery revealed a possible role for PHD3 in regulation of mTOR pathway signalling.

CONCLUSIONS

Our findings suggest crucial involvement of PHD3 in the maintenance of key cellular functions including glycolysis and protein synthesis in ccRCC.

Multiple renal cancer susceptibility polymorphisms modulate the HIF pathway

Un-physiological activation of hypoxia inducible factor (HIF) is an early event in most renal cell cancers (RCC) following inactivation of the von Hippel-Lindau tumor suppressor. Despite intense study, how this impinges on cancer development is incompletely understood. To test for the impact of genetic signals on this pathway, we aligned human RCC-susceptibility polymorphisms with genome-wide assays of HIF-binding and observed highly significant overlap. Allele-specific assays of HIF binding, chromatin conformation and gene expression together with eQTL analyses in human tumors were applied to mechanistic analysis of one such overlapping site at chromosome 12p12.1. This defined a novel stage-specific mechanism in which the risk polymorphism, rs12814794, directly creates a new HIF-binding site that mediates HIF-1α isoform specific upregulation of its target BHLHE41. The alignment of multiple sites in the HIF cis-acting apparatus with RCC-susceptibility polymorphisms strongly supports a causal model in which minor variation in this pathway exerts significant effects on RCC development.

MicroRNAs and altered metabolism of clear cell renal cell carcinoma: Potential role as aerobic glycolysis biomarkers

BACKGROUND

Warburg Effect is a metabolic switch that occurs in most of cancer cells but its advantages are not fully understood. This switch is known to happen in renal cell carcinoma (RCC), which is the most common solid cancer of the adult kidney. RCC carcinogenesis is related to pVHL loss and Hypoxia Inducible Factor (HIF) activation, ultimately leading to the activation of several genes related to glycolysis. MicroRNAs (miRNAs) regulate gene expression at a post-transcriptional level and are also deregulated in several cancers, including RCC.

SCOPE OF REVIEW

This review focuses in the miRNAs that direct target enzymes involved in glycolysis and that are deregulated in several cancers. It also reviews the possible application of miRNAs in the improvement of clinical patients' management.

MAJOR CONCLUSIONS

Several miRNAs that direct target enzymes involved in glycolysis are downregulated in cancer, strongly influencing the Warburg Effect. Due to this strong influence, FDG-PET can possibly benefit from measurement of these miRNAs. Restoring their levels can also bring an improvement to the current therapies.

GENERAL SIGNIFICANCE

Despite being known for almost a hundred years, the Warburg Effect is not fully understood. MiRNAs are now known to be intrinsically connected with this effect and present an opportunity to understand it. They also open a new door to improve current diagnosis and prognosis tests as well as to complement current therapies. This is urgent for cancers like RCC, mostly due to the lack of an efficient screening test for early relapse detection and follow-up and the development of resistance to current therapies.

The zebrafish miR-125c is induced under hypoxic stress via hypoxia-inducible factor 1α and functions in cellular adaptations and embryogenesis

Hypoxia is a unique environmental stress. Hypoxia inducible factor-lα (HIF-lα) is a major transcriptional regulator of cellular adaptations to hypoxic stress. MicroRNAs (miRNAs) as posttranscriptional gene expression regulators occupy a crucial role in cell survival under low-oxygen environment. Previous evidences suggested that miR-125c is involved in hypoxia adaptation, but its precise biological roles and the regulatory mechanism underlying hypoxic responses remain unknown. The present study showed that zebrafish miR-125c is upregulated by hypoxia in a Hif-lα-mediated manner in vitro and in vivo. Dual-luciferase assay revealed that cdc25a is a novel target of miR-125c. An inverse correlation between miR-125c and cdc25a was further confirmed in vivo, suggesting miR-125c as a crucial physiological inhibitor of cdc25a which responds to cellular hypoxia. Overexpression of miR-125c suppressed cell proliferation, led to cell cycle arrest at the G1 phase in ZF4 cells and induced apoptotic responses during embryo development. More importantly, miR-125c overexpression resulted in severe malformation and reduction of motility during zebrafish embryonic development. Taken together, we conclude that miR-125c plays a pivotal role in cellular adaptations to hypoxic stress at least in part through the Hif-1α/miR-125c/cdc25a signaling and has great impact on zebrafish early embryonic development.

High expression of Aldolase A predicts poor survival in patients with clear-cell renal cell carcinoma

Background

Aldolase A (ALDOA) is a glycolytic enzyme that drives the glycolytic metabolic pathway in mammalian cells. The overexpression of ALDOA was observed in a variety of cancers including clear-cell renal cell carcinoma (ccRCC). However, little was known about the clinicopathological significance and prognostic value of ALDOA in ccRCC patients.

Methods

The expression of ALDOA was detected using immunohistochemical staining in 162 formalin-fixed, paraffin-embedded ccRCC sections. Prognostic outcomes correlated with ALDOA were examined using Kaplan–Meier analysis and the Cox proportional hazards model.

Results

In patients with ccRCC, increased cytoplasmic ALDOA expression was positively associated with tumor size (P=0.021), TNM stages (P=0.034), lymph node metastasis (P=0.020), and overall survival (OS) (P<0.001). Kaplan–Meier analysis showed that high cytoplasmic expression of ALDOA was associated with a statistically significant lower OS (P<0.001). Multivariate analysis demonstrated that ALDOA expression was an independent and significant prognostic factor (HR =3.561, 95% CI =1.715–7.396, P=0.001). ALDOA expression was not associated with significant prognostic deference in the subgroups of TNM stage I patients or pT1 patients.

Conclusion

Our results suggest that ALDOA expression is an independent prognostic factor for OS in patients with ccRCC.

AHNAK2 is a Novel Prognostic Marker and Oncogenic Protein for Clear Cell Renal Cell Carcinoma

Integrative database analysis was performed to identify novel candidate oncogene AHNAK2 overexpressed in clear cell renal cell carcinoma (ccRCC). However, the function of AHNAK2 in cancer cells is currently unknown. In this study, we first confirmed the upregulation of AHNAK2 in ccRCC tissues compared with adjacent normal tissues in 15 pairs of samples. Then we analyzed AHNAK2 expression in a large cohort of ccRCC patient samples (n = 355), and found that up-regulation of AHNAK2 was positively correlated with tumor progression and poor survival (p = 0.032). Knockdown of AHNAK2 inhibited cancer cell proliferation, colony formation and migration in vitro and tumorigenic ability in vivo. Meanwhile, knockdown of AHNAK2 impaired the cell oncologic-metabolism by inhibiting lipid synthesis. Moreover, we observed that expression of AHNAK2 was greatly upregulated, at least in part, by hypoxia in cancer cells. By using chromatin immune-precipitation (CHIP) and promoter-luciferase reporter assays, we identified that upregulation of AHNAK2 induced by hypoxia was hypoxia-inducible factor-1α (HIF1α)-dependent. Knockdown of AHNAK2 impaired hypoxia-induced epithelial-mesenchymal transition (EMT) and stem cell-like properties. Considered together, we reveal that AHNAK2 is upregulated in cancer cells and hypoxic upregulation of AHNAK2 can drive tumorigenesis and progression by supporting EMT and cancer cell stemness. Thus, AHNAK2 is a novel prognostic marker and an oncogenic protein for ccRCC.

CD34 immunostaining enhances a distinct pattern of intratumor angiogenesis with prognostic implications in clear cell renal cell carcinoma

Clear cell renal cell carcinoma is an aggressive neoplasm related to VHL gene inactivation. The molecular events derived from this initial alteration lead to a permanent intracellular pseudo-hypoxic status that stimulates vascular proliferation. The resulting increased intratumor angiogenesis is the target of most modern therapies. Although intratumor angiogenesis has received full attention in the last years, few studies have focused on its potential importance from a strict morphological approach. Intratumor angiogenesis has been analyzed in a retrospective series of clear cell renal cell carcinomas (n = 208) with long-term follow-up (n = 177). Two different patterns of angiogenesis have been highlighted with CD34 at the front of tumor invasion, termed continuous and discontinuous, respectively. The continuous pattern of angiogenesis showed a complete microvascular network surrounding totally tumor nests. Conversely, the discontinuous pattern displayed an incomplete network around tumor nests. The continuous pattern was associated to shorter 5-year (p = 0.00064, hazard ratio = 2.8) and 15-year (p = 0.014, hazard ratio = 1.7) survivals. Cox regression multivariate analysis also showed that the continuous pattern (p = 0.016373) remains a significant variable when considered together with grade (p = 0.001755) and stage (p = 0.000952). These findings support the notion that a continuous CD34⁺ pattern of intratumor angiogenesis may be useful for pathologists in predicting tumor behavior in clear cell renal cell carcinomas.

Ubiquitination and regulation of AURKA identifies a hypoxia-independent E3 ligase activity of VHL

The hypoxia-regulated tumor-suppressor von Hippel-Lindau (VHL) is an E3 ligase that recognizes its substrates as part of an oxygen-dependent prolyl hydroxylase (PHD) reaction, with hypoxia-inducible factor α (HIFα) being its most notable substrate. Here we report that VHL has an equally important function distinct from its hypoxia-regulated activity. We find that Aurora kinase A (AURKA) is a novel, hypoxia-independent target for VHL ubiquitination. In contrast to its hypoxia-regulated activity, VHL mono-, rather than poly-ubiquitinates AURKA, in a PHD-independent reaction targeting AURKA for degradation in quiescent cells, where degradation of AURKA is required to maintain the primary cilium. Tumor-associated variants of VHL differentiate between these two functions, as a pathogenic VHL mutant that retains intrinsic ability to ubiquitinate HIFα is unable to ubiquitinate AURKA. Together, these data identify VHL as an E3 ligase with important cellular functions under both normoxic and hypoxic conditions.

Hypoxia-inducing factor (HIF)-1α-derived peptide capable of inducing cancer-reactive cytotoxic T lymphocytes from HLA-A24+ patients with renal cell carcinoma

Hypoxic tumor microenvironment makes cancer cells to be therapy-resistant and hypoxia-inducing factors (HIFs) play a central role in hypoxic adaptation. Especially, renal cell carcinoma (RCC) is often associated with von Hippel-Lindau (VHL) gene mutations, leading to up-regulation of HIFs. However, from a different point of view, this suggests the possibility that HIFs could be promising targets in anti-cancer therapy. In this study, we searched for HIF-1α-derived peptides that are able to induce RCC-reactive cytotoxic T lymphocytes (CTLs) from HLA-A24⁺ RCC patients. Among five peptides derived from HIF-1α, which were prepared based on the binding motif to the HLA-A24 allele, a HIF-1α_278-287 peptide induced peptide-specific CTLs from peripheral blood mononuclear cells of HLA-A24⁺ RCC patients most effectively. In immunoblot assays, the expression of HIF-1α was lowly detected in whole and nuclear lysates of RCC cell lines even under normoxia (20% O₂), and their expression in whole lysates was increased under hypoxia (1% O₂). Additionally, HIF-1α_278-287 peptide-stimulated T cells showed a higher cytotoxicity against HLA-A24⁺ HIF-1α-expressing RCC cells than against HLA-A24^- HIF-1α-expressing RCC cells. The cytotoxicity was inhibited by the addition of HIF-1α_278-287 peptide-pulsed cold target cells. Altogether, these results indicate that the HIF-1α_278-287 peptide could be a candidate for peptide-based anti-cancer vaccines for HLA-A24⁺ RCC patients.

Developmental pathways associated with cancer metastasis: Notch, Wnt, and Hedgehog

Master developmental pathways, such as Notch, Wnt, and Hedgehog, are signaling systems that control proliferation, cell death, motility, migration, and stemness. These systems are not only commonly activated in many solid tumors, where they drive or contribute to cancer initiation, but also in primary and metastatic tumor development. The reactivation of developmental pathways in cancer stroma favors the development of cancer stem cells and allows their maintenance, indicating these signaling pathways as particularly attractive targets for efficient anticancer therapies, especially in advanced primary tumors and metastatic cancers. Metastasis is the worst feature of cancer development. This feature results from a cascade of events emerging from the hijacking of epithelial-mesenchymal transition, angiogenesis, migration, and invasion by transforming cells and is associated with poor survival, drug resistance, and tumor relapse. In the present review, we summarize and discuss experimental data suggesting pivotal roles for developmental pathways in cancer development and metastasis, considering the therapeutic potential. Emerging targeted antimetastatic therapies based on Notch, Wnt, and Hedgehog pathways are also discussed.

The epigenetic landscape of renal cancer

The majority of kidney cancers are associated with mutations in the von Hippel-Lindau gene and a small proportion are associated with infrequent mutations in other well characterized tumour-suppressor genes. In the past 15 years, efforts to uncover other key genes involved in renal cancer have identified many genes that are dysregulated or silenced via epigenetic mechanisms, mainly through methylation of promoter CpG islands or dysregulation of specific microRNAs. In addition, the advent of next-generation sequencing has led to the identification of several novel genes that are mutated in renal cancer, such as PBRM1, BAP1 and SETD2, which are all involved in histone modification and nucleosome and chromatin remodelling. In this Review, we discuss how altered DNA methylation, microRNA dysregulation and mutations in histone-modifying enzymes disrupt cellular pathways in renal cancers.

Rock2 promotes RCC proliferation by decreasing SCARA5 expression through β-catenin/TCF4 signaling

Rho-associated coiled-coil forming protein kinase 2 (Rock2), as a key effector of the small GTPase RhoA, is involved in tumor development. Scavenger receptor class A member 5 (SCARA5) is an important regulator of biological processes in cancer cells. However, the roles and relationship of Rock2 and SCARA5 in renal cell carcinoma (RCC) remain unclear. In this study, we found that Rock2 expression was markedly increased in clinical RCC tissues compared with that in adjacent non-cancerous tissues. High expression of Rock2 was inversely correlated with patient survival in RCC, which indicated that Rock2 may be a prognostic marker in human RCC. In addition, Rock2 knockdown increased SCARA5 expression and suppressed RCC cell proliferation both in vitro and in vivo. Furthermore, we found that the β-catenin/TCF4 pathway contributed to the effect of Rock2 on SCARA5-mediated RCC proliferation. Taken together, these results suggest that this newly identified Rock2-β-catenin/TCF4-SCARA5 axis will provide novel insight into the understanding of the regulatory mechanisms of proliferation in human RCC.

The Nephrologist's Tumor: Basic Biology and Management of Renal Cell Carcinoma

Kidney cancer, or renal cell carcinoma (RCC), is a disease of increasing incidence that is commonly seen in the general practice of nephrology. However, RCC is under-recognized by the nephrology community, such that its presence in curricula and research by this group is lacking. In the most common form of RCC, clear cell renal cell carcinoma (ccRCC), inactivation of the von Hippel-Lindau tumor suppressor is nearly universal; thus, the biology of ccRCC is characterized by activation of hypoxia-relevant pathways that lead to the associated paraneoplastic syndromes. Therefore, RCC is labeled the internist's tumor. In light of this characterization and multiple other metabolic abnormalities recently associated with ccRCC, it can now be viewed as a metabolic disease. In this review, we discuss the basic biology, pathology, and approaches for treatment of RCC. It is important to distinguish between kidney confinement and distant spread of RCC, because this difference affects diagnostic and therapeutic approaches and patient survival, and it is important to recognize the key interplay between RCC, RCC therapy, and CKD. Better understanding of all aspects of this disease will lead to optimal patient care and more recognition of an increasingly prevalent nephrologic disease, which we now appropriately label the nephrologist's tumor.

E2F3 upregulation promotes tumor malignancy through the transcriptional activation of HIF-2α in clear cell renal cell carcinoma

The E2F3 transcriptional regulatory pathway plays a major part in multiple-cancer progression, but the specific contributions of this pathway to tumor formation and the progression of clear cell renal cell carcinoma (ccRCC) are not fully understood. Clinically, we demonstrated that E2F3 was overexpressed in advanced tumor features. Moreover, cytoplasmic restoration predicted the poor overall survival of ccRCC patients. As a remarkable oncogene for ccRCC, high HIF-2α levels closely correlated with E2F3 upregulation. We observed in vitro that E2F3 overexpression and knockdown regulated HIF-2α expression. Furthermore, we found that HIF-2α harbored multiple E2F3 binding sites in the promoters. Mechanistically, E2F3 acted to transactivate HIF-2α transcription, which in turn exerted a serial effect on the pivotal epithelial–mesenchymal transition-related genes. The RNA interference-mediated silencing of HIF-2α attenuated E2F3-enhanced cell migration and invasion in vitro and in vivo. Overall, our results identified HIF-2α as a direct target gene for E2F3 upregulation, which was critical for carcinogenesis and progression of ccRCC. Thus, targeting the E2F3–HIF-2α interaction may be a promising approach to ccRCC treatment.

Recent advances in the understanding of molecular mechanisms of cartilage degeneration, synovitis and subchondral bone changes in osteoarthritis

Osteoarthritis (OA), the most common form of degenerative joint disease, is linked to high morbidity. It is predicted to be the single greatest cause of disability in the general population by 2030. The development of disease-modifying therapy for OA currently face great obstacle mainly because the onset and development of the disease involve complex molecular mechanisms. In this review, we will comprehensively summarize biological and pathological mechanisms of three key aspects: degeneration of articular cartilage, synovial immunopathogenesis, and changes in subchondral bone. For each tissue, we will focus on the molecular receptors, cytokines, peptidases, related cell, and signal pathways. Agents that specifically block mechanisms involved in synovial inflammation, degeneration of articular cartilage, and subchondral bone remodeling can potentially be exploited to produce targeted therapy for OA. Such new comprehensive agents will benefit affected patients and bring exciting new hope for the treatment of OA.

The Expression of VHL (Von Hippel-Lindau) After Traumatic Spinal Cord Injury and Its Role in Neuronal Apoptosis

The VHL (Von Hippel-Lindau) gene is a tumor suppressor gene, which is best known as an E3 ubiquitin ligase that negatively regulates the hypoxia inducible factor. The inactivation of VHL gene could result in the abnormal synthesis of VHL protein, which is in contact with the development and occurrence of renal clear cell carcinoma. However, the expression and possible function of VHL in central nervous system (CNS) is still unclear. To examine the function of VHL in CNS injury and repair, we used an acute spinal cord injury (SCI) model in adult rats. Western blot analysis showed an important upregulation of VHL protein, reaching a peak at day 3 and then declined during the following days. Double immunofluorescence staining showed that VHL was co-expressed with neurons, but not with astrocytes and microglia. Moreover, we detected that active caspase-3 had co-localized with VHL in neurons after SCI. Additionally in vitro, VHL depletion, by short interfering RNA, significantly reduced neuronal apoptosis. In conclusion, these data suggested that the change of VHL protein expression was related to neuronal apoptosis after SCI.

Wnt Signaling in Renal Cell Carcinoma

Renal cell carcinoma (RCC) accounts for 90% of all kidney cancers. Due to poor diagnosis, high resistance to the systemic therapies and the fact that most RCC cases occur sporadically, current research switched its focus on studying the molecular mechanisms underlying RCC. The aim is the discovery of new effective and less toxic anti-cancer drugs and novel diagnostic markers. Besides the PI3K/Akt/mTOR, HGF/Met and VHL/hypoxia cellular signaling pathways, the involvement of the Wnt/β-catenin pathway in RCC is commonly studied. Wnt signaling and its targeted genes are known to actively participate in different biological processes during embryonic development and renal cancer. Recently, studies have shown that targeting this pathway by alternating/inhibiting its intracellular signal transduction can reduce cancer cells viability and inhibit their growth. The targets and drugs identified show promising potential to serve as novel RCC therapeutics and prognostic markers. This review aims to summarize the current status quo regarding recent research on RCC focusing on the involvement of the Wnt/β-catenin pathway and how its understanding could facilitate the identification of potential therapeutic targets, new drugs and diagnostic biomarkers.

Targeting Protein-Protein Interactions in the HIF System

Animals respond to chronic hypoxia by increasing the levels of a transcription factor known as the hypoxia-inducible factor (HIF). HIF upregulates multiple genes, the products of which work to ameliorate the effects of limited oxygen at cellular and systemic levels. Hypoxia sensing by the HIF system involves hydroxylase-catalysed post-translational modifications of the HIF α-subunits, which 1) signal for degradation of HIF-α and 2) limit binding of HIF to transcriptional coactivator proteins. Because the hypoxic response is relevant to multiple disease states, therapeutic manipulation of the HIF-mediated response has considerable medicinal potential. In addition to modulation of catalysis by the HIF hydroxylases, the HIF system manifests other possibilities for therapeutic intervention involving protein-protein and protein-nucleic acid interactions. Recent advances in our understanding of the structural biology and biochemistry of the HIF system are facilitating medicinal chemistry efforts. Herein we give an overview of the HIF system, focusing on structural knowledge of protein-protein interactions and how this might be used to modulate the hypoxic response for therapeutic benefit.

[Hereditary renal tumors: More common than expected?]

Renal cell carcinomas are associated with hereditary tumor syndromes in approximately 5 % of cases. In patients with a hereditary predisposition, tumors show an earlier age of onset, often with a multicentric and bilateral manifestation. While some patients with renal cell carcinoma can be classified into well-characterized kidney cancer syndromes others have a genetic background which is still poorly understood. Most of the specific tumor syndromes are associated with a histopathologically distinct renal cell tumor phenotype. The recognition of patients with hereditary renal cell carcinoma and the identification of individual family members with a higher risk of development of renal tumors is important for early tumor detection and treatment. This manuscript reviews the clinical pathological and molecular findings of hereditary renal cell carcinoma syndromes.