Anti-angiogenic therapy in the treatment of advanced renal cell cancer

Anti-bevacizumab idiotype antibody vaccination is effective in inducing vascular endothelial growth factor-binding response, impairing tumor outgrowth

Tumors require blood supply and, to overcome this restriction, induce angiogenesis. Vascular endothelial growth factor (VEGF) plays an important role in this process, which explains the great number of antiangiogenic therapies targeting VEGF. The research and development of targeted therapy has led to the approval of bevacizumab, a humanized anti-VEGF monoclonal antibody (mAb), in clinical settings. However, side effects have been reported, usually as a consequence of bolus-dose administration of the antibody. This limitation could be circumvented through the use of anti-idiotype (Id) antibodies. In the present study, we evaluated the efficacy of an active VEGF-binding immune response generated by an anti-bevacizumab idiotype mAb, 10.D7. The 10.D7 anti-Id mAb vaccination led to detectable levels of VEGF-binding anti-anti-Id antibodies. In order to examine whether this humoral immune response could have implications for tumor development, 10.D7-immunized mice were challenged with B16-F10 tumor cells. Mice immunized with 10.D7 anti-Id mAb revealed reduced tumor growth when compared to control groups. Histological analyses of tumor sections from 10.D7-immunized mice showed increased necrotic areas, decreased CD31-positive vascular density and reduced CD68-positive cell infiltration. Our results encourage further therapeutic studies, particularly if one considers that the anti-Id therapeutic vaccination maintains stable levels of VEGF-binding antibodies, which might be useful in the control of tumor relapse.

Antitumor effect and biological pathways of a recombinant adeno-associated virus as a human renal cell carcinoma suppressor

The aims of this work are to study the antitumor effect of the adeno-associated virus on the xenografted tumors of chick embryo chorioallantoic membrane and predict potential genes and biological pathways which are associated with renal cell carcinoma. The adeno-associated virus NT4-TAT-6 × His-VHLbeta was constructed and identified. Then, chick embryos with xenografted tumor were divided into three groups and respectively inoculated with rAAV/NT4-TAT-6 × His-VHLbeta (group A), empty virus (group B), and phosphate-buffered saline (group C, the control subject). Antitumor effect in each group was investigated by means of immunofluorescence observation. Genes interacted with von Hippel–Lindau were screened by Search Tool for the Retrieval of Interacting Genes/Proteins database, while pathway analysis were performed based on Kyoto Encyclopedia of Genes and Genomes. The growth of xenografted tumors inoculated with recombinant adeno-associated virus was slower than the control subjects. The tumor volumes of group A showed significant difference compared with group B and group C (P < 0.05). Growth of xenografted tumors which administered with the recombinant adeno-associated virus was inhibited. Among the protein–protein interaction network, TCEB2, HIF1A, TCEB1, CUL2, RBX1, and PHF17 were hub genes which might be involved in the development of renal cell carcinoma. The most significant signaling pathway was renal cell carcinoma. In this paper, we constructed and identified the recombinant adeno-associated virus NT4-TAT-6 × His-VHLbeta and studied the antitumor effect of the adeno-associated virus on xenografted tumors of chicken embryo chorioallantoic membrane. In addition, genes in the protein–protein interaction network which are associated with renal cell carcinoma were revealed and the biological pathway of renal cell carcinoma was identified. Our results provide a gene-therapeutic agent for the treatment of human renal cell carcinoma.

Inhibition of MMP-9 using a pyrrole-imidazole polyamide reduces cell invasion in renal cell carcinoma

We investigated the clinical significance of the expression levels of matrix metalloproteinase 9 (MMP-9) in renal cell carcinoma (RCC). In addition, we validated the efficacy of pyrrole imidazole polyamide (PIP) targeting MMP-9 on inhibiting proliferation and invasion of RCC. We evaluated the expression levels of MMP-9 in 249 RCC specimens by immunostaining and analyzed the association between MMP-9 expression levels and cancer-specific survival. Furthermore, in a human RCC cell line, Caki-2, we tested the effect of a couple of PIPs targeting MMP-9 one recognizing an NF-κB binding site (MMP-9-NF-κB PIP) and another for the AP-1 binding site (MMP-9-AP-1 PIP) in the MMP-9 promoter. The expression levels of MMP-9, proliferative activity and invasive capability were tested by quantitative PCR, WST8 assay and Matrigel invasion assay, respectively. By immunostaining of the clinical specimens, strong MMP-9 staining was proven to be a significant predictor of poor prognosis for cancer-specific survival (P<0.01). In Caki-2 cells, MMP-9-NF-κB PIP significantly reduced the expression levels of MMP-9 mRNA and inhibited cell invasion, but did not affect the cell proliferation activity. On the other hand, no effect was found in MMP-9-AP-1 PIP on MMP-9 mRNA expression, cell proliferation and invasion. We confirmed the inhibitory effects of MMP-9-NF-κB PIP on the expression of MMP-9 and subsequent invasion of Caki-2 cells. Since it was clearly shown that high MMP-9 expression levels were associated with poor prognosis of RCC, MMP-9 is a potential candidate target for RCC treatment. Transcription therapy using a minor groove binder, such as NF-κB PIP, may be a potential therapeutic agent for RCC, although further investigation is required.

Development of a novel interferon-α2b gene construct with a repetitive hypoxia-inducible factor binding site and its suppressive effects on human renal cell carcinoma cell lines in vitro

BACKGROUND

Despite the advent of targeted therapies, interferon-alpha (IFN-α) remains a therapeutic option for advanced renal cell carcinoma (RCC), especially in Japan, with a treatment response rate of 15-20 %. To improve the efficacy of IFN-α-based therapies, we evaluated a novel treatment strategy for RCC using an IFN-α2b gene construct with a repetitive hypoxia-inducible factor binding site.

METHODS

We constructed an expression plasmid designated 5HREp-IFN-α2b containing the coding region of the IFN-α2b gene. Five copies of the hypoxia-response element (HRE) sequences were inserted upstream of the IFN-α2b gene, and the construct was transfected into human RCC cell lines ACHN, 786-O and KU19-20. The concentrations of IFN-α2b in the conditioned media were measured by enzyme-linked immunosorbent assay. Cell viabilities were determined by MTS assays.

RESULTS

Construct-induced IFN-α secretion was confirmed in all three cell lines. IFN-α production was significantly enhanced by the hypoxia-mimicking agent deferoxamine mesylate in cell lines expressing the wild-type von Hippel-Lindau (VHL) gene (KU19-20 and ACHN) compared with cells expressing the mutant VHL gene (786-O). The construct exerted significant suppressive effects on the viabilities of all RCC cell lines.

CONCLUSION

This is the first study to report on the construction of a cytokine gene with a repetitive hypoxia-inducible factor binding site and its application in the suppression of human cancer cells. Gene therapy using this IFN-α2b gene construct with HREs may represent a novel treatment modality for advanced RCC.

Therapeutic potential of nitric oxide donors in the prevention and treatment of angiogenesis-inhibitor-induced hypertension

Angiogenesis is critical to tumor growth as well as to metastases. This process is tightly regulated by pro- and anti-angiogenic growth factors and their receptors. Some of these factors are highly specific for the endothelium-e.g., vascular endothelial growth factor (VEGF). A variety of drugs that target VEGF or its receptors have been developed for the treatment of different tumor types and a number of new agents is expected to be introduced within the coming years. However, clinical experience has revealed that inhibition of VEGF induces several side effects including hypertension and renal and cardiac toxicity. Angiogenesis-inhibitor-induced hypertension represents "crux medicorum" as it is often pharmacoresistant to antihypertensive therapy. We consider two most important pathomechanisms in the development of hypertension induced by angiogenesis inhibitors. The first represents direct inhibition of NO production leading to reduced vasodilatation and the second consists in increased proliferation of vascular medial cells mediated by NO deficiency and is resulting in fixation of hypertension. Based on the results of experimental and clinical studies as well as on our clinical experience, we assume that NO donors could be successfully used not only for the treatment of developed angiogenesis-inhibitor-induced hypertension but also for preventive effects. We thoroughly documented three clinical cases of cancer patients with resistant hypertension who on receiving NO donor treatment achieved target blood pressure level and a good clinical status.

Pretreatment assessment of tumor enhancement on contrast-enhanced computed tomography as a potential predictor of treatment outcome in metastatic renal cell carcinoma patients receiving antiangiogenic therapy

BACKGROUND

Tumor vascularity is a potential predictor of treatment outcomes in metastatic renal cell carcinoma (mRCC), and contrast enhancement of tumors in computed tomography (CT) is correlated significantly with microvessel density. In this study, the authors investigated whether tumor enhancement in contrast-enhanced CT (CECT) is useful for predicting outcomes in patients with mRCC who are receiving antiangiogenic therapy.

METHODS

Attenuation values were reviewed retrospectively on CECT images of all metastatic lesions in 66 patients from February 2007 to November 2008. All patients received a tyrosine kinase inhibitor (either sunitinib or sorafenib). Tumor response was evaluated on CECT studies every 12 weeks. The authors analyzed the association between contrast enhancement and treatment outcomes, including objective response, tumor size reduction rate, time to response, and time to progression.

RESULTS

In 46 patients, 198 metastatic lesions were assessed. Tumor size was reduced in 140 lesions (70.7%) and was increased in 58 lesions (29.3%). The mean reduction in size was 23.8%. The overall mean time to response and the time to progression were 8.6 months and 16.4 months, respectively. In multivariate analyses, tumor enhancement and enhancement pattern were associated with objective responses (P = .003 and P = .028, respectively). In addition, tumor enhancement was associated with tumor size reduction (P = .004). In Cox proportional hazards models, only tumor enhancement was associated significantly with the time to size reduction and progression-free survival (P = .03 and P = .015, respectively).

CONCLUSIONS

Tumor enhancement on CECT images was associated with treatment outcomes and was identified as a potential predictor of treatment outcomes after antiangiogenic therapy in patients with mRCC.

Metastatic Renal Cancer: What Role for Everolimus?

Metastatic renal cell carcinoma is uncommon (only 3% of cancers worldwide) but of poor prognosis. Renal cell carcinoma has traditionally been treated with cytokines (interferon-α or interleukin-2). More recently, a more clear understanding of the molecular and cellular mechanisms of the disease, involving the VEGF receptor and mTOR, has led to the discovery of novel therapies. Therapeutic options in patients with advanced RCC include the VEGF receptor inhibitors Sunitinib and Sorafenib, the anti-VEGF monoclonal antibody Bevacizumab and the mTORC1 inhibitors Temsirolimus and Everolimus. In 2009, Everolimus was FDA-approved for the treatment of patients with advanced clear cell RCC which had progressed within 6 months of stopping treatment with Sunitinib or sorafenib, or both drugs. Everolimus resulted in a 70% reduction in the risk of disease recurrence or death. The purpose of this review is to update on the current knowledge of the role of Everolimus in metastatic renal cell carcinoma.

The role of the mammalian target of rapamycin (mTOR) in renal disease

The mammalian target of rapamycin (mTOR) is a serine/threonine kinase that plays a pivotal role in mediating cell size and mass, proliferation, and survival. mTOR has also emerged as an important modulator of several forms of renal disease. mTOR is activated after acute kidney injury and contributes to renal regeneration and repair. Inhibition of mTOR with rapamycin delays recovery of renal function after acute kidney injury. Activation of mTOR within the kidney also occurs in animal models of diabetic nephropathy and other causes of progressive kidney disease. Rapamycin ameliorates several key mechanisms believed to mediate changes associated with the progressive loss of GFR in chronic kidney disease. These include glomerular hypertrophy, intrarenal inflammation, and interstitial fibrosis. mTOR also plays an important role in mediating cyst formation and enlargement in autosomal dominant polycystic kidney disease. Inhibition of mTOR by rapamycin or one of its analogues represents a potentially novel treatment for autosomal dominant polycystic kidney disease. Finally, inhibitors of mTOR improve survival in patients with metastatic renal cell carcinoma.

siRNA targeting survivin inhibits growth and induces apoptosis in human renal clear cell carcinoma 786-O cells

We investigated the inhibitory effect of small interfering RNA (siRNA) targeting survivin gene on cell proliferation and apoptosis in human renal clear cell carcinoma 786-O cells. qRT-PCR, immunocytochemistry, and Western Blot were used to detect Survivin gene expression in 786-O cells. Cell proliferation was determined by BrdU assay and PCNA expression. Cell apoptosis was analyzed through detection of caspase-3 activity, and the effect of survivin-siRNA on Bcl-2 gene expression was also examined. Forty-eight hours after transfection, survivin expression was markedly inhibited at the mRNA and protein level. Downregulation of survivin resulted in a significant inhibition of tumor cell growth. Caspase-3 activity showed that siRNA targeting survivin gene induced cell apoptosis in 786-O cells. Moreover, Bcl-2 protein expression was markedly inhibited by transfection with siRNA against survivin. These results indicate that siRNA targeting survivin gene can downregulate survivin gene expression in 786-O cells, inhibit growth, and induce apoptosis of renal carcinoma cells.

Tumor escape from endogenous, extracellular matrix-associated angiogenesis inhibitors by up-regulation of multiple proangiogenic factors

PURPOSE

Thrombospondin-1 (Tsp1), endostatin, and tumstatin are extracellular matrix-associated proteins that inhibit angiogenesis. We examined the mechanisms by which tumor cells may bypass the antiangiogenic effects of these endogenous regulators.

EXPERIMENTAL DESIGN

CT26 colon and RenCa renal carcinoma cells were stably transfected with Tsp1, endostatin, or tumstatin cDNA. Subcutaneous and metastatic tumor growth in syngeneic mice was analyzed. Expression of proangiogenic factors in resulting tumors was measured by quantitative real-time PCR. The combination of Tsp1 and vascular endothelial growth factor (VEGF) receptor-2 inhibition was also examined.

RESULTS

There was significant suppression of angiogenesis in flank tumors and liver metastases formed from cells overexpressing Tsp1, endostatin, or tumstatin. However, all tumors ultimately escaped angiogenesis inhibition. The combination of all three angiogenesis inhibitors had no additive effect beyond overexpression of a single inhibitor. Using quantitative real-time PCR, we found that VEGF and platelet-derived growth factor (PDGF)-A levels were routinely up-regulated at least 5-fold in all CT26 tumors overexpressing any antiangiogenic protein, and there were variable increases in angiopoietin 2 (Ang2), basic fibroblast growth factor, and PDGF-B. In contrast, RenCa tumors, which have high baseline levels of VEGF and PDGF-B, relied on basic fibroblast growth factor, Ang1, and PDGF-A up-regulation to counteract Tsp1 overexpression. Growth of CT26 cells with Tsp1 overexpression was suppressed when anti-VEGFR-2 treatment was added.

CONCLUSIONS

Cancer cells with overexpression of three different endogenous angiogenesis inhibitor eventually escape angiogenesis inhibition by up-regulation of various proangiogenic factors. Tsp1, endostatin, and tumstatin may be functionally redundant in this system. These endogenous angiogenesis inhibitors are likely best used in combination with the blockade of proangiogenic pathways or with traditional chemotherapy or radiation therapy.

Erythropoietin prevents blood brain barrier damage induced by focal cerebral ischemia in mice

Recombinant human erythropoietin (rhEPO), a neurovascular protective agent, therapeutically supports angiogenesis after stroke by enhancing endogenous up-regulation of vascular endothelial growth factor (VEGF). Increased VEGF expression has been characterized to negatively impact the integrity of the blood brain barrier (BBB), causing brain edema and secondary injury. The present study investigated the rhEPO-induced BBB protection after stroke and how it might be achieved by affecting VEGF pathway. rhEPO treatment (5,000 U/kg, i.p., 30 min before stroke and once a day for three days after stroke) reduced Evans blue leakage and brain edema after ischemia. The expression of the BBB integrity markers, occludin, alpha-catenin and beta-catenin, in the brain was preserved in animals received rhEPO. rhEPO up-regulated VEGF expression; however, the expression of VEGF receptor-2 (fetal liver kinase receptor, Flk-1) was significantly reduced in rhEPO-treated animals three days after stroke. We propose that, disregarding increased VEGF levels, rhEPO protects against ischemia-induced BBB damage at least partly by down-regulating Flk-1 expression and the response to VEGF signaling in the acute phase after stroke.