Evaluating rational non-cross-resistant combination therapy in advanced clear cell renal cell carcinoma: combined mTOR and AKT inhibitor therapy

Targeted Induction of Endogenous VDUP1 by Small Activating RNA Inhibits the Growth of Lung Cancer Cells

Recent studies have reported that small double-strand RNAs (dsRNAs) can activate endogenous genes via an RNA-based promoter targeting mechanism termed RNA activation (RNAa). In the present study, we showed that dsVDUP1-834, a novel small activating RNA (saRNA) targeting promoter of vitamin D₃ up-regulated protein 1 (VDUP1) gene, up-regulated expression of VDUP1 at both mRNA and protein levels in A549 lung cancer cells. We also demonstrated that dsVDUP1-834 inhibited cell proliferation in A549 lung cancer cells. Further studies showed that dsVDUP1-834 induced cell-cycle arrest by increasing p27 and p53 and decreasing cyclin A and cyclin B1. In addition, knockdown of VDUP1 abrogated dsVDUP1-834-induced up-regulation of VDUP1 gene expression and related effects. The activation of VDUP1 by dsVDUP1-834 was accompanied by an increase in dimethylation of histone 3 at lysine 4 (H3K4me2) and acetylation of histone 3 (H3ac) and a decrease in dimethylation of histone 3 at lysine 9 (H3K9me2) at the target site of VDUP1 promoter. Moreover, the enrichment of Ago2 was detected at the dsVDUP1-834 target site, and Ago2 knockdown significantly suppressed dsVDUP1-834-mediated inhibition of cell proliferation and modulation of cell-cycle regulators. Taken together, the results presented in this report demonstrate that dsVDUP1-834 induces VDUP1 gene expression by epigenetic changes, resulting in cell growth inhibition and cell-cycle arrest. Our results suggest that targeted induction of VDUP1 by dsVDUP1-834 might be a promising therapeutic strategy for the treatment of lung cancer.

Bioinformatics analysis of KLF2 as a potential prognostic factor in ccRCC and association with epithelial‑mesenchymal transition

Clear cell renal cell carcinoma (ccRCC) is a primary pathological subtype of RCC and has poor clinical outcome. Krüppel-like factors (KLFs), which are zinc-finger proteins, may be involved in ccRCC development and progression. KLFs belong to the zinc-finger family of DNA-binding transcription factors and regulate transcription of downstream target genes. KLFs are involved in cancer development. The present study aimed to investigate the role of KLFs in ccRCC prognosis. The Cancer Genome Atlas database and multifactorial analysis showed that KLFs were widely expressed in pan-cancers and KLF2 was an independent protective factor for ccRCC prognosis. Patients with low KLF2 expression had a low survival probability and expression of KLF2 was downregulated in patients with ccRCC with high pathological grade (II + III vs. I). In addition, western blot and reverse transcription-quantitative PCR revealed that KLF2 was expressed at low levels in ccRCC cell lines and overexpression of KLF2 inhibited cell migration. In addition, KLF2 expression was negatively correlated with methylation. KLF2 expression was elevated following treatment of ccRCC cells with DNA methyltransferase inhibitor. A prognostic risk index prediction model was constructed based on multiple Cox regression. The receiver operating characteristic curve was 0.780 (area under curve >0.5). Furthermore, Gene Ontology enrichment analysis showed that ‘cell adhesion’ and ‘junction’ were negatively correlated with KLF2 and that high-risk group exhibited significantly activated ‘epithelial-mesenchymal transition’. Western blot analysis showed that overexpression of KLF2 increased expression of E-cadherin, while decreasing levels of N-cadherin and vimentin. The present study highlighted the role of KLFs in ccRCC prognosis prediction and provides a research base for the search of validated prognostic biological markers for ccRCC.

Preclinical efficacy of dual mTORC1/2 inhibitor AZD8055 in renal cell carcinoma harboring a TFE3 gene fusion

Background

Renal cell carcinomas (RCC) harboring a TFE3 gene fusion (TfRCC) represent an aggressive subset of kidney tumors. Key signaling pathways of TfRCC are unknown and preclinical in vivo data are lacking. We investigated Akt/mTOR pathway activation and the preclinical efficacy of dual mTORC1/2 versus selective mTORC1 inhibition in TfRCC.

Methods

Levels of phosphorylated Akt/mTOR pathway proteins were compared by immunoblot in TfRCC and clear cell RCC (ccRCC) cell lines. Effects of the mTORC1 inhibitor, sirolimus, and the dual mTORC1/2 inhibitor, AZD8055, on Akt/mTOR activation, cell cycle progression, cell viability and cytotoxicity were compared in TfRCC cells. TfRCC xenograft tumor growth in mice was evaluated after 3-week treatment with oral AZD8055, intraperitoneal sirolimus and respective vehicle controls.

Results

The Akt/mTOR pathway was activated to a similar or greater degree in TfRCC than ccRCC cell lines and persisted partly during growth factor starvation, suggesting constitutive activation. Dual mTORC1/2 inhibition with AZD8055 potently inhibited TfRCC viability (IC50 = 20-50 nM) due at least in part to cell cycle arrest, while benign renal epithelial cells were relatively resistant (IC50 = 400 nM). Maximal viability reduction was greater with AZD8055 than sirolimus (80–90% versus 30–50%), as was the extent of Akt/mTOR pathway inhibition, based on significantly greater suppression of P-Akt (Ser473), P-4EBP1, P-mTOR and HIF1α. In mouse xenograft models, AZD8055 achieved significantly better tumor growth inhibition and prolonged mouse survival compared to sirolimus or vehicle controls.

Conclusions

Akt/mTOR activation is common in TfRCC and a promising therapeutic target. Dual mTORC1/2 inhibition suppresses Akt/mTOR signaling more effectively than selective mTORC1 inhibition and demonstrates in vivo preclinical efficacy against TFE3-fusion renal cell carcinoma.

Electronic supplementary material

The online version of this article (10.1186/s12885-019-6096-0) contains supplementary material, which is available to authorized users.

Small activating RNA induced expression of VHL gene in renal cell carcinoma

Recent studies have reported that chemically synthesized double-stranded RNAs (dsRNAs), also known as small activating RNA (saRNAs), can specifically induce gene expression by targeting promoter sequences by a mechanism termed RNA activation (RNAa). In the present study, we designed 4 candidate saRNAs targeting the Von Hippel-Lindau (VHL) gene promoter. Among these saRNAs, dsVHL-821 significantly inhibited cell growth by up-regulating VHL at both the mRNA and protein levels in renal cell carcinoma 769-P cells. Functional analysis showed that dsVHL-821 induced apoptosis by increasing p53, decreasing Bcl-xL, activating caspase 3/7 and poly-ADP-ribose polymerase in a dose-dependent manner. Chromatin immunoprecipitation analysis revealed that dsVHL-821 increased the enrichment of Ago2 and RNA polymerase II at the dsVHL-821 target site. In addition, Ago2 depletion significantly suppressed dsVHL-821-induced up-regulation of VHL gene expression and related effects. Single transfection of dsVHL-821 caused long-lasting (14 days) VHL up-regulation. Furthermore, the activation of VHL by dsVHL-821 was accompanied by an increase in dimethylation of histone 3 at lysine 4 (H3K4me2) and acetylation of histone 4 (H4ac) and a decrease in dimethylation of histone 3 at lysine 9 (H3K9me2) and lysine 27 (H3K27me2) in the dsVHL-821 target region. Taken together, these results demonstrate that dsVHL-821, a novel saRNA for VHL, induces the expression of the VHL gene by epigenetic changes, leading to inhibition of cell growth and induction of apoptosis, and suggest that targeted activation of VHL by dsVHL-821 may be explored as a novel treatment of renal cell carcinoma.

Notch 1 is a valuable therapeutic target against cell survival and proliferation in clear cell renal cell carcinoma

Notch 1 is a key component of the Notch pathway, which performs a crucial role in clear cell renal cell carcinoma (CCRCC) development. The present study aimed to investigate whether Notch 1 could serve as a potential target for CCRCC treatment. Firstly, an association analysis was performed using 52 CCRCC cases and 30 normal controls. The results indicated that Notch 1 protein expression in renal tissues was closely associated with the incidence of CCRCC. In addition, higher Notch 1 expression in CCRCC tissues was positively associated with higher tumor-node-metastasis stage and Fuhrman grade, in addition to larger tumor size. Subsequently, an in vitro study was conducted to examine the biological functions of Notch 1 in CCRCC 786-O cells through inhibiting the Notch 1 expression with Notch 1-specific small interfering RNA (siRNA). As a result, the inhibition of Notch 1 expression by increasing concentrations of Notch 1-specific siRNA dose-dependently decreased cell proliferation and increased cell apoptosis in 786-O cells. Furthermore, B-cell lymphoma-2 and procaspase-3 expression exhibited a dose-dependent decrease accompanied with a dose-dependent inactivation of the Akt/mammalian target of rapamycin (mTOR) signaling pathway in Notch 1 siRNA-treated 786-O cells. These findings demonstrated that Notch 1 was associated with CCRCC carcinogenesis and progression, the underlying mechanism of which was that Notch 1 acted as an activator for cell proliferation and a suppressor for cell apoptosis through the Akt/mTOR signaling-dependent pathway in CCRCC. In conclusion, the present study confirmed that Notch 1 is a valuable target against cell survival and proliferation in CCRCC treatment.

Novel drugs that target the metabolic reprogramming in renal cell cancer

Molecular profiling studies of tumor tissue from patients with clear cell renal cell cancer (ccRCC) have revealed extensive metabolic reprogramming in this disease. Associations were found between metabolic reprogramming, histopathologic Fuhrman grade, and overall survival of patients. Large-scale genomics, proteomics, and metabolomic analyses have been performed to identify the molecular players in this process. Genes involved in glycolysis, the pentose phosphate pathway, glutamine metabolism, and lipogenesis were found to be upregulated in renal cell cancer (RCC) specimens as compared to normal tissue. Preclinical research indicates that mutations in VHL, FBP1, and the PI3K-AKT-mTOR pathway drives aerobic glycolysis through transcriptional activation of the hypoxia-inducible factors (HIF). Mechanistic studies revealed glutamine as an important source for de novo fatty acid synthesis through reductive carboxylation. Amplification of MYC drives reductive carboxylation. In this review, we present a detailed overview of the metabolic changes in RCC in conjunction with potential novel therapeutics. We discuss preclinical studies that have investigated targeted agents that interfere with various aspects of tumor cell metabolism and emphasize their impact specifically on glycolysis, lipogenesis, and tumor growth. Furthermore, we describe a number of phase 1 and 2 clinical trials that have been conducted with these agents.

GSK-3 directly regulates phospho-4EBP1 in renal cell carcinoma cell-line: an intrinsic subcellular mechanism for resistance to mTORC1 inhibition

Background

The phosphoinositide 3-kinase (PI3K)/Akt/mammalian target of rapamycin 1 (mTORC1) signaling pathway is aberrantly activated in renal cell carcinoma (RCC). We previously demonstrated glycogen synthase kinase-3β (GSK-3β) positively regulated RCC proliferation. The aim of this study was to evaluate the role of GSK-3 in the PI3K/Akt/mTORC1 pathway and regulation of the downstream substrates, eukaryotic translation initiation factor 4E-binding protein 1 (4EBP1), ribosomal protein S6 kinase (S6K), and ribosomal protein S6 (S6RP).

Methods

We used human RCC cell lines (ACHN, Caki1, and A498) and, as normal controls, human renal proximal tubular epithelial cell (HRPTEpC) and non-tumorous kidney tissues that were obtained surgically for treatment of RCC patients. Rapamycin-resistant ACHN (ACHN/RR) cells were generated with chronic exposure of ACHN to rapamycin ranging from 1nM finally to 1 μM. Cell viability, cell cycling and direct interaction between GSK-3β and 4EBP1 were evaluated with MTS assay, flowcytometry and in vitro kinase assay with recombinant GSK-3β and 4EBP1products, respectively. Protein expression and phosphorylation of molecules associated with the PI3K/Akt/mTORC1 pathway were examined by immunoblotting. Effects of drug combination were determined as the combination index with CompuSyn software.

Results

Overexpression and phosphorylation of 4EBP1 and S6RP together with GSK-3 activation were observed in RCC cell lines, but not in human normal kidney cells and tissues. Cell proliferation, p4EBP1 and pS6RP were strongly suppressed by GSK-3 inhibition. Rapamycin and LY294002 sufficiently decreased pS6RP, but only moderately p4EBP1. In vitro kinase assays showed that recombinant GSK-3β phosphorylated recombinant 4EBP1, and the effect was blocked by GSK-3 inhibitors. Different from rapamycin, AR- A014418 remarkably inhibited cell proliferation, and rapidly suppressed p4EBP1 and pS6RP in ACHN and ACHN/RR (in 30 min to 1 h). AR- A014418 and rapamycin combination showed additivity at lower concentrations, but antagonism at higher concentrations.

Conclusions

GSK-3β could directly phosphorylate 4EBP1 and activate the mTORC1 downstream signaling cascades to enhance protein biosynthesis and cell proliferation in RCC cell lines independent of rapamycin sensitivity. The direct GSK-3β/4EBP1 pathway might be an important subcellular mechanism as an inherent equipment for RCC cells to acquire clinical chemoresistance to mTORC1 inhibitors.

Electronic supplementary material

The online version of this article (doi:10.1186/s12885-016-2418-7) contains supplementary material, which is available to authorized users.

Synergistic roles of p53 and HIF1α in human renal cell carcinoma-cell apoptosis responding to the inhibition of mTOR and MDM2 signaling pathways

Introduction

mTOR and MDM2 signaling pathways are frequently deregulated in cancer development, and inhibition of mTOR or MDM2 independently enhances carcinoma-cell apoptosis. However, responses to mTOR and MDM2 antagonists in renal cell carcinoma (RCC) remain unknown.

Materials and methods

A498 cells treated with MDM2 antagonist MI-319 and/or mTOR inhibitor rapamycin were employed in the present study. Cell apoptosis and Western blot analysis were performed.

Results and conclusion

We found that the MDM2 inhibitor MI-319 induced RCC cell apoptosis mainly dependent on p53 overexpression, while the mTOR antagonist rapamycin promoted RCC cell apoptosis primarily through upregulation of HIF1α expression. Importantly, strong synergistic effects of MI-319 and rapamycin combinations at relatively low concentrations on RCC cell apoptosis were observed. Depletion of p53 or HIF1α impaired both antagonist-elicited apoptoses to differential extents, corresponding to their expression changes responding to chemical treatments, and double knockdown of p53 and HIF1α remarkably hindered MI-319- or rapamycin-induced apoptosis, suggesting that both p53 and HIF1α are involved in MDM2 or mTOR antagonist-induced apoptosis. Collectively, we propose that concurrent activation of p53 and HIF1α may effectively result in cancer-cell apoptosis, and that combined MDM2 antagonists and mTOR inhibitors may be useful in RCC therapy.

Induction of epithelial-mesenchymal transition via activation of epidermal growth factor receptor contributes to sunitinib resistance in human renal cell carcinoma cell lines

Sunitinib is widely used for treating renal cell carcinoma (RCC). However, some patients do not respond to treatment with this drug. We aimed to study the association between sunitinib sensitivity and epithelial-mesenchymal transition (EMT) regulation via epidermal growth factor receptor (EGFR) signaling, which is a mechanism of resistance to anticancer drugs. Three RCC cell lines (786-O, ACHN, and Caki-1) were used, and then we evaluated cell viability, EMT regulatory proteins, and signal transduction with sunitinib treatment. Cell viability of 786-O cells was maintained after treatment with sunitinib. After treatment with sunitinib, EGFR phosphorylation increased in 786-O cells, resulting in an increase in the phosphorylation of extracellular signal-regulated kinase, nuclear translocation of β-catenin, and expression of mesenchymal markers. These results suggest that sunitinib induced EMT via activation of EGFR in 786-O cells, but not in ACHN and Caki-1 cells. Caki-1/SN cells, a resistant cell line generated by continuous exposure to sunitinib, displayed increased phosphorylation of EGFR. Cell viability in the presence of sunitinib was decreased by erlotinib, as the selective inhibitor of EGFR, treatment in 786-O and Caki-1/SN cells. Similarly, erlotinib suppressed sunitinib-induced EGFR activation and upregulated mesenchymal markers. Thus, we postulate that resistance to sunitinib in RCC may be associated with EMT caused by activation of EGFR.

Changes in signaling pathways induced by vandetanib in a human medullary thyroid carcinoma model, as analyzed by reverse phase protein array

BACKGROUND

Medullary thyroid carcinoma (MTC) is a rare tumor that is caused by activating mutations in the proto-oncogene RET. Vandetanib, a tyrosine-kinase inhibitor, has been recently approved to treat adult patients with metastatic MTC. The aim of this study was to investigate changes in signaling pathways induced by vandetanib treatment in preclinical MTC models, using the reverse-phase protein array method (RPPA).

METHODS

The human TT cell line was used to assess in vitro and in vivo activity of vandetanib. Protein extracts from TT cells or TT xenografted mice, treated by increasing concentrations of vandetanib for different periods of time, were probed with a set of 12 antibodies representing major signaling pathways, using RPPA. Results were validated using two distinct protein detection methods: Western immunoblotting and immunohistochemistry.

RESULTS

Vandetanib displays antiproliferative and antiangiogenic activities and inhibits RET autophosphorylation. The MAPK and AKT pathways were the two major signaling pathways inhibited by vandetanib. Interestingly, phosphorylated levels of NFκB-p65 were significantly increased by vandetanib. Comparable results were obtained in both the in vitro and in vivo approaches, as well as for the protein detection methods. However, some discrepancies were observed between RPPA and Western immunoblotting, possibly due to lack of specificity of the primary antibodies used.

CONCLUSIONS

Overall, our results confirmed the interest of RPPA for screening global changes induced in signaling pathways by kinase inhibitors. MAPK and AKT were identified as the main pathways involved in vandetanib response in MTC models. Our results also suggest alternative routes for controlling the disease, and provide a rationale for the development of therapeutic combinations based on the comprehensive identification of molecular events induced by inhibitors.

Perifosine in renal cell carcinoma

INTRODUCTION

Perifosine is an oral alkylphospholipid which has recently been assessed clinically in patients with advanced renal cell carcinoma (RCC). Perifosine acts primarily by attenuating the activation of Akt by preventing its pleckstrin homology (PH) domain-dependent localization to the cell membrane.

AREAS COVERED

This review summarizes the therapeutic landscape of RCC including the proposed role of perifosine in patients with advanced RCC. The mechanism of action, pharmacodynamics, pharmacokinetics, clinical efficacy in RCC and safety of perifosine are all addressed as well.

EXPERT OPINION

Although perifosine has clear clinical activity in RCC, it is not superior to currently available agents and therefore does not appear worthy of further clinical development in RCC as a single agent. Given the observed efficacy and mild toxicity, however, perifosine may have a role in RCC therapy given in combination with other molecularly targeted agents.

Inhibition of chondrosarcoma growth by mTOR inhibitor in an in vivo syngeneic rat model

Background

Chondrosarcomas are the second most frequent primary malignant type of bone tumor. No effective systemic treatment has been identified in advanced or adjuvant phases for chondrosarcoma. The aim of the present study was to determine the antitumor effects of doxorubicin and everolimus, an mTOR inhibitor on chondrosarcoma progression.

Methods and Findings

Doxorubin and/or everolimus were tested in vivo as single agent or in combination in the rat orthotopic Schwarm chondrosarcoma model, in macroscopic phase, as well as with microscopic residual disease. Response to everolimus and/or doxorubicin was evaluated using chondrosarcoma volume evolution (MRI). Histological response was evaluated with % of tumor necrosis, tumor proliferation index, metabolism quantification analysis between the treated and control groups. Statistical analyses were performed using chi square, Fishers exact test. Doxorubicin single agent has no effect of tumor growth as compared to no treatment; conversely, everolimus single agent significantly inhibited tumor progression in macroscopic tumors with no synergistic additive effect with doxorubicin. Everolimus inhibited chondrosarcoma proliferation as evaluated by Ki67 expression did not induce the apoptosis of tumor cells; everolimus reduced Glut1 and 4EBP1 expression. Importantly when given in rats with microscopic residual diseases, in a pseudo neoadjuvant setting, following R1 resection of the implanted tumor, everolimus significantly delayed or prevented tumor recurrence.

Conclusions

MTOR inhibitor everolimus blocks cell proliferation, Glut1 expression and HIF1a expression, and prevents in vivo chondrosarcoma tumor progression in both macroscopic and in adjuvant phase post R1 resection. Taken together, our preclinical data indicate that mTOR inhibitor may be effective as a single agent in treating chondrosarcoma patients. A clinical trial evaluating mTOr inhibitor as neo-adjuvant and adjuvant therapy in chondrosarcoma patients is being constructed.

Two phase 2 trials of the novel Akt inhibitor perifosine in patients with advanced renal cell carcinoma after progression on vascular endothelial growth factor-targeted therapy

BACKGROUND

The clinical activity of allosteric inhibitors of mammalian target of rapamycin (mTOR) inhibitors in renal cell carcinoma (RCC) may be limited by upstream activation of phosphatidylinositol 3 (PI3)-kinase/Akt resulting from mTOR1 inhibition. On the basis of this rationale, 2 independent phase 2 trials (Perifosine 228 and 231) were conducted to assess the efficacy and safety of the novel Akt inhibitor perifosine in patients with advanced RCC who had failed on previous vascular endothelial growth factor (VEGF)-targeted therapy.

METHODS

In the Perifosine 228 trial, 24 patients with advanced RCC received oral perifosine (100 mg daily). Perifosine 231 enrolled 2 groups that received daily oral perifosine (100 mg daily): Group A comprised 32 patients who had received no prior mTOR inhibitor, and Group B comprised 18 patients who had received 1 prior mTOR inhibitor.

RESULTS

In the Perifosine 228 trial, 1 patient achieved a partial response (objective response rate, 4%; 95% confidence interval, 0.7%-20%), and 11 patients (46%) had stable disease as their best response. The median progression-free survival was 14.2 weeks (95% confidence interval, 7.7-21.6 weeks). In the Perifosine 231 trial, 5 patients achieved a partial response (objective response rate, 10%; 95% confidence interval, 4.5%-22.2%) and 16 patients (32%) had stable disease as their best response. The median progression-free survival was 14 weeks (95% confidence interval, 12.9, 20.7 weeks). Overall, perifosine was well tolerated, and there were very few grade 3 and 4 events. The most common toxicities included nausea, diarrhea, musculoskeletal pain, and fatigue.

CONCLUSIONS

Although perifosine demonstrated activity in patients with advanced RCC after failure on VEGF-targeted therapy, its activity was not superior to currently available second-line agents. Nonetheless, perifosine may be worthy of further study in RCC in combination with other currently available therapies.

Kinome expression profiling identifies IKBKE as a predictor of overall survival in clear cell renal cell carcinoma patients

There are 516 known kinases in the human genome. Because of their important role maintaining proper cellular function, they are often misregulated during tumorigenesis and associated with clinical outcomes in cancer patients, including clear cell renal cell carcinoma (ccRCC). However, less is known about the global expression status of these genes in renal cell carcinoma and their association with clinical outcomes. We performed a systematic analysis of gene expression for 503 kinases in 93 tumor samples and adjacent normal tissues. Expression patterns for 41 kinases were able to clearly differentiate tumor and normal samples. Expression of I-kappa-B kinase epsilon (IKBKE) was associated with a 5.3-fold increased risk of dying [95% confidence interval (CI): 1.93-14.59, P-value: 0.0012]. Individuals with high IKBKE expression were at a significantly increased risk of death (hazard ratio: 3.34, 95% CI: 1.07-10.40, P-value: 0.038) resulting in a significantly reduced overall survival time compared with those with low IKBKE tumor expression (P-value: 0.049). These results for IKBKE were validated in a replication population consisting of 237 ccRCC patients (P-value: 0.0021). Furthermore, IKBKE was observed to be higher expressed in tumors compared with adjacent normal tissues (P-value < 10(-7)). IKBKE is a member of the nuclear factor-kappaB (NF-κB) signaling pathway and interestingly, gene expression patterns for other members of the NF-κB pathway were not associated with survival, suggesting that IKBKE gene expression may be an independent marker of variation in overall survival. Overall, these results support a novel role for IKBKE expression in modulating overall survival in ccRCC patients.