Molecular biology of renal cell carcinoma

Knockdown of ubiquitin‑specific peptidase 39 inhibits the malignant progression of human renal cell carcinoma

Ubiquitin specific peptidase 39 (USP39) serves important roles in mRNA processing and is involved in tumorigenesis of multiple solid malignancies. However, the influence and underlying mechanism of USP39 on human renal cell carcinomas (RCC) remain to be elucidated. The current study investigated the functional roles of USP39 in human RCC cell lines. siRNA‑mediated RNA interference was used to downregulate USP39 in RCC cells. CCK‑8, wound healing and invasion assays were performed to assess the proliferative ability and metastatic potential. The cell cycle distribution and apoptosis were evaluated by flow cytometry. The activity of signaling pathways and the expression of cell cycle‑related proteins were detected by western blot analysis. The siRNA‑directed RNA interference targeting USP39 could effectively downregulate the expression level of USP39 in two RCC cell lines. Depletion of USP39 by siRNA significantly suppressed cell growth and decreased invasive capacity of RCC cells. Silencing of USP39 induced cell apoptosis and cell cycle arrest at G2/M phase. Additionally, the expression levels of apoptotic and G2/M phase‑related proteins were notably decreased following depletion of USP39. Mechanistically, downregulation of USP39 blocked the activation of Akt and extracellular signal regulated kinase signaling pathways in RCC cells. These findings indicate that USP39 may serve as an oncogenic factor in RCC and could be a potential therapeutic candidate for human RCCs.

Evaluation of polymorphisms in angiogenesis-related genes as predictive and prognostic markers for sunitinib-treated metastatic renal cell carcinoma patients

PURPOSE

Single nucleotide polymorphisms (SNPs) in angiogenesis-associated genes might play an important role in activity of the tyrosine kinase inhibitor sunitinib and could affect survival of cancer patients treated with this drug. The aim of this retrospective study was to elucidate the role of 10 known SNPs in VEGFA, VEGFR1, VEGFR2 and VEGFR3 as potential prognostic and predictive markers in an independent cohort of patients with metastatic renal cell carcinoma (mRCC).

METHODS

DNA from 121 mRCC patients treated with sunitinib was used to analyze SNPs by TaqMan genotyping assays. Disease control rate was evaluated according to RECIST. Adverse effects of sunitinib were registered from medical records. The results of Cox and logistic regression were verified by correction for multiple testing.

RESULTS

Kaplan-Meier analysis revealed a reduced progression-free survival in patients with the wild-type (WT) allele of the VEGFA SNP rs699947 compared to variant alleles. Patients with the AA/AC-alleles of the VEGFR1 SNP rs9582036 had an improved median overall survival compared to those with the CC-WT allele what could be confirmed by multivariable Cox proportional hazard regression analyses. No statistically significant associations between the analyzed SNPs and higher risk for adverse effects were observed.

CONCLUSIONS

The results of this study suggest that most of the selected SNPs in angiogenesis-related genes are not associated with survival of mRCC patients after sunitinib therapy or with adverse effects. Only the VEGFR1 SNP rs9582036 showed a statistically significant association with overall survival. The potential of SNPs as prognostic and predictive markers for sunitinib-treated mRCC patients should be finally assessed by prospective studies.

Increased Insulin mRNA Binding Protein-3 Expression Correlates with Vascular Enhancement of Renal Cell Carcinoma by Intravenous Contrast-CT and is Associated with Bone Metastasis

Purpose

To: 1) assess the correlation between CT vascularity and a candidate molecular marker of RCC metastasis (insulin-like mRNA binding protein-3 (IMP3)); and 2) demonstrate the differential expression of IMP3 in high vs. low vascular tumors.

Experimental design

Retrospectively obtained contrast CT from 72 patients with primary RCC were used to establish threshold values for Low, Intermediate and High tumor vascularity. Paired histopathology specimens from 33 of these patients were used for immunohistochemistry (IHC) to correlate CT with IMP-3 expression. IMP-3 gene expression studies were performed on RCC and poorly vascular prostate cancer (PC) human bone metastases samples to confirm presence of IMP3 in metastatic samples from RCC. Gene expression studies were performed on RCC 786-O and PC3 cell lines to confirm the presence of high expression of IMP3 in the RCC cell line.

Results

IMP-3 expression positively correlated with CT vascular enhancement (p<0.01). IMP3 expression by IHC was strongly positive in all RCC, but weak in PC bone metastases. Real time RT-PCR demonstrated a significant 4-fold increase in imp-3 expression in RCC 786-O vs. PC3 cells in vitro (p<0.001).

Conclusion

Quantitation of pre-operative CT is a feasible method to phenotype primary RCC vascularity, which correlates with IMP-3 expression. In situ and cell line studies demonstrate an association between high IMP-3 expression and RCC bone metastasis. Studies aimed at defining the diagnostic potential of biomarkers for RCC bone metastasis, and functional significance of IMP-3 in RCC vascularity and tumor progression are warranted.

Analysis of TMEM174 gene expression in various renal cancer types by RNA in situ hybridization

Transmembrane protein 174 (TMEM174) mRNA is easily detectable in human kidney tissues and activates AP-1 and promotes 293T cell proliferation. In the present study, RNA in situ hybridization was used to detect TMEM174 gene expression in various malignant renal cancer and normal renal tissues. The results showed that TMEM174 exhibits differential expression in renal tissues, with a high positive rate of expression in squamous cell carcinoma with necrosis, papillary renal cell carcinoma and transitional cell carcinoma, and a low positive rate of expression in clear cell carcinoma, interstitial nephritis, undifferentiated carcinoma, retroperitoneal metastatic clear cell carcinoma, adrenal gland metastatic clear cell carcinoma, pelvic cavity metastatic chromophobe carcinoma, severe atypical hyperplasia of transitional epithelium and hyperplasia. Extremely weak expression was exhibited in collecting duct carcinoma, Wilms’ tumor, chronic pyelonephritis, acute pyelonephritis, cancer adjacent normal renal tissue and normal renal tissue. In conclusion, the TMEM174 gene exhibited high expression levels in certain renal carcinomas, which may indicate that TMEM174 may have a significant role in the development and progression of these renal carcinomas.

The role of functional imaging in the era of targeted therapy of renal cell carcinoma

Antiangiogenic therapies interacting with tumor-specific pathways have been established for targeted therapy of renal cell carcinoma (RCC). However, evaluation of tumor response based on morphologic tumor diameter measurements has limitations, as tumor shrinkage may lag behind pathophysiological response. Functional imaging techniques such as dynamic contrast-enhanced (DCE) ultrasound (US), computed tomography (CT) and magnetic resonance imaging (MRI), unenhanced diffusion-weighted MRI (DW-MRI), and also metabolic imaging with positron emission tomography (PET) have the ability to assess physiological parameters and to predict and monitor therapy response. Assessment of changes in vascularity, cellularity, oxygenation, and glucose uptake with functional imaging during targeted therapy may correlate with progression-free survival and can predict tumor response or progression. In this review, we explore the potential of functional imaging techniques for assessing the effects of targeted therapy of RCC and as well review the reproducibility and limitations.

Unique angiogenic and vasculogenic properties of renal cell carcinoma in a xenograft model of bone metastasis are associated with high levels of vegf-a and decreased ang-1 expression

Management of various tumor metastases to bone has dramatically improved, but this is not so for renal cell carcinoma (RCC), which is a difficult surgical problem due to its great vascularity. Furthermore, the unique mechanisms that mediate RCC vasculogenesis in bone remain unknown. To understand this process we developed a xenograft model that recapitulates highly vascular RCC versus less vascular tumors that metastasize to bone. Human tumor cell lines of RCC (786-O), prostate cancer (PC3), lung cancer (A549), breast cancer (MDA-MB231), and melanoma (A375) were transduced with firefly luciferase (Luc), injected into the tibiae of nude mice, and differences in growth, osteolysis, and vascularity were assessed by longitudinal bioluminescent imaging, micro-CT for measurement of calcified tissues and vascularity and histology. The results showed that while RCC-Luc has reduced growth and osteolytic potential versus the other tumor lines, it displayed a significant increase in vascular volume (p < 0.05). This expansion was due to 3- and 5-fold increases in small and large vessel numbers respectively. In vitro gene expression profiling revealed that RCC-Luc expresses significantly (p < 0.05) more vegf-a (10-fold) and 20- to 30-fold less ang-1 versus the other lines. These data demonstrate the utility of this model to study the unique vasculogenic properties of RCC bone metastases.

Targeting of VEGF-dependent transendothelial migration of cancer cells by bevacizumab

Cancer progression is often associated with the formation of malignant effusions. Vascular endothelial growth factor (VEGF) is a major regulator of vascular permeability and has been implicated as mediator of tumor progression. We examined the production and secretion of VEGF(165) in various primary cancer cells derived from malignant effusions, and the role of exogenous VEGF(165) as a mediator of effusion formation. VEGF(165) was constantly secreted by all cultured tumor cells in an mTOR-dependent manner, as it was inhibited by the mTOR inhibitor rapamycin. Secreted VEGF(165) showed functional activity by inducing endothelial leakiness and tumor cell-transendothelial migration in vitro, effects which could be reverted by the anti-VEGF antibody bevacizumab. Thus, mTOR inhibitors as well as bevacizumab should be considered as potential agents in cancer patients suffering from malignant effusions.

RLIP76: a target for kidney cancer therapy

RLIP76 is a multifunctional transporter protein that serves as an energy-dependent efflux mechanism for endogenously generated toxic metabolites as well as exogenous toxins, including chemotherapy drugs. Our recent studies in cultured cells, syngeneic animal tumor model, and in xenograft model have shown that RLIP76 serves a major cancer-specific antiapoptotic role in a wide variety of histologic types of cancer, including leukemia, melanoma, colon, lung, prostate, and ovarian cancer. Results of present studies in cell culture and xenograft model of Caki-2 cells show that RLIP76 is an important anticancer for kidney cancer because inhibition of RLIP76 function by antibody or its depletion by small interfering RNA or antisense DNA caused marked and sustained regression of established human kidney xenografts of Caki-2 cells in nude mouse.

mTOR signalling in human cancer

Inhibitors of mTOR, the mammalian target of rapamycin, have been extensively studied in clinical trials for cancer treatment. Results have been promising, mostly in certain lymphomas, but in solid tumours the results have been generally less encouraging. However, recent results, particularly in renal cell carcinoma, have provided renewed interest in the role of mTOR inhibitors in solid tumours. A rational, and potentially more successful, development of these agents (i.e., RAD001, temsirolimus and AP23573) likely relies in a deeper knowledge of mTOR signalling in cancer, both at the preclinical and clinical levels. These would allow a better selection of patients more likely to respond to the use of biologically active doses of the agents and the development of mechanistically based combinations with other agents. The goal of this review is to provide an update on the complex signalling of mTOR in cancer and on the biological effects of mTOR inhibitors in cancer cells.

PtdIns-4,5-P2 as a potential therapeutic target for pathologic angiogenesis

A variety of diseases arise, at least in part, when the events controlling the formation and stability of blood vessels are deregulated. For instance, the growth and survival of solid tumors are tightly linked to their ability to undergo vascularization. Similarly, pathologic angiogenesis of the retina or choroid underscores blinding diseases that afflict a substantial percentage of the world's population. Therefore, it is of great interest to develop antiangiogenic drugs that will relieve the burden of vascular diseases such as cancer, age-related macular degeneration and proliferative diabetic retinopathy. In this article, the authors highlight their recent discovery that PtdIns-4,5-P2)can regulate vessel stability. This finding identifies PtdIns-4,5-P2 as a novel target for angiogenesis therapies.