Original article
Renin-angiotensin system (RAS) blockade attenuates growth and metastatic potential of renal cell carcinoma in mice

https://doi.org/10.1016/j.urolonc.2014.11.022Get rights and content

Highlights

  • We examined the effects of RAS blockade on orthotopic model of murine renal carcinoma.

  • We used ACEI and ARB drugs isolated or combined to treat the animals.

  • RAS blockade decreased the tumor proliferation and metastatic capacity of murine RCC.

  • The effects may have been due to less angiogenesis sinceVEGF and CD34 were decreased.

  • Combined blockade was worse in inhibiting tumor growth than isolated treatments.

Abstract

Objectives

Renal cell carcinoma (RCC) is the most frequent type of cancer among renal neoplasms in adults and responds poorly to radiotherapy and chemotherapy. There is evidence that blockade of the renin-angiotensin system (RAS) might have antineoplastic effects. The aim of this study was to investigate the effects of RAS blockade on RCC in a murine model.

Methods and materials

Murine renal cancer cells (Renca) were injected (1×105) into the subcapsular space of the left kidney of BALB/c mice (8 wk of age). The animals were divided into 4 groups: a control group (no treatment), angiotensin-receptor blockers group (losartan 100 mg/kg/d), angiotensin-converting enzyme inhibitor group (captopril 10 mg/kg/d), and angiotensin-receptor blockers +angiotensin-converting enzyme inhibitor group (losartan 100 mg/kg/d +captopril 10 mg/kg/d). The animals received the drugs by gavage for 21 days after inoculation, beginning 2 days before tumor induction, and were then euthanized. After killing the animals, the kidneys and lungs were removed, weighed, and processed for histopathological and immunohistochemical analyses. Angiogenesis and vascular microvessels were assessed with the antibodies anti–vascular endothelial growth factor and anti-CD34.

Results

Angiotensin II–inoculated animals developed renal tumors. Treated animals presented smaller tumors, regardless of the therapeutic regimen, and far fewer lung metastases in both quantity and dimension compared with the controls. The expression of vascular endothelial growth factor and CD34 were significantly decreased in renal tumors of treated animals compared with the controls.

Conclusions

Our findings suggest that blockade of RAS decreases tumor proliferation and metastatic capacity of RCC in this experimental model.

Introduction

Renal cell carcinoma (RCC) is the most common kidney cancer and represents approximately 3% of all adult malignancies [1], [2], [3]. There has been an increase in the incidence of RCC in recent years. More than one-third of patients with RCC have evidence of metastases at the time of diagnosis, and approximately 33% develop systemic recurrence after primary tumor resection [4], [5]. The lung is the most common site of distant recurrence. Lung metastases are found in 50% to 60% of patients [6].

RCC is not responsive to conventional radiotherapy and chemotherapy [7]. In the case of localized disease, RCC is curable with surgery. However, the prognosis is poor for patients presenting with distant metastases [8]. The treatment of metastatic RCC (mRCC) has significantly improved with a better understanding of the disease pathogenesis. Recently, some multitarget-oriented drugs have shown impressive activity in mRCC, with a high percentage of patients exhibiting a partial response or disease stabilization or both; additionally, these drugs have had a significant effect on survival [9], [10], [11], [12]. Nevertheless, the outcomes are far from optimal, and novel therapeutic strategies are needed in order to help overcome this disease.

The renin-angiotensin system (RAS) regulates normal kidney blood flow and fluid homeostasis and also plays a key role in blood pressure control [13], [14]. Angiotensin II (Ang II) is a crucial component of RAS, and its actions are mediated through its specific cell surface membrane receptors, AT1R, and AT2R. A potential role of Ang II in promoting tumor growth is through hormonal actions and vasoconstrictive effects [15]. Lever et al. [16] reported the first clinical evidence that long-term Ang II blockade may have a protective effect against cancer and suggested that it could prevent carcinogenesis. There have been several reports that Ang II can induce neovascularization in experimental models via AT1R [17], [18]. AT1R is also expressed frequently in various human tumors [19], [20]. Several studies have shown that RAS blockade inhibits tumor growth both in vitro [21], [22], [23] and in vivo [24], [25], [26], [27], [28], [29], and some suggest that this inhibition is due to the suppression of angiogenesis. Vascular endothelial growth factor (VEGF) is the most important angiogenic factor associated with inducing and maintaining neovasculature in tumors, thereby exerting its mitogenic effect by binding to its receptors, mainly VEGF receptor 2 [30].

In this study, we investigated the effects of Ang II blockade on a murine model of RCC.

Section snippets

Cell line and culture

Renca, a murine cell RCC line of spontaneous origin derived from a BALB/c mouse, was purchased from the American Type of Culture collection (CRL-2947). The cells were maintained in RPMI supplemented with 10% fetal bovine serum (Life Technologies) and supplemented with fresh 2-mM l-glutamine (Life Technologies), 100-U/ml penicillin, and 100-mg/ml streptomycin. Cells were maintained in a humid chamber at 37°C and 5% CO2.

Animals

All experimental procedures were conducted according to the National

Tumor growth

Inoculation of the left kidney of BALB/c mice (8 wk) resulted in the development of large tumors (Fig. 1A) with a mean increase in kidney weight of 4.30±0.78-fold in relation to the contralateral kidney (Fig. 1B). In the course of the experiments, 2 animals in the control group, 1 animal in the ARB group and 1 animal in the group ARB+ACEI died. Tumor growth was significantly reduced in treated mice when compared with the controls. However, the animals treated with ARB or ACEI alone had

Discussion

RCC is relatively resistant to conventional cancer treatments, such as radiation and chemotherapy, and despite new treatment options for advanced and metastatic disease, radical nephrectomy remains the mainstay for the treatment of disease [7].

Recent studies have identified a high expression of AT1R in primary RCC and metastases, as well as the involvement of Ang II in tumor angiogenesis and metastasis [26], [31], [32].

Therefore, we decided to investigate whether the blockade of Ang II with

Conclusions

We conclude that the Ang II/AT1R axis plays an important role in the progression and metastatic potential of RCC and that suppression of tumor angiogenesis may be one of the mechanisms by which ACEI and ARB attenuate the growth and metastases of RCC. It is evident that further studies on this subject should be conducted to strengthen these data. However, these drug classes may represent a potentially promising strategy as an ancillary therapy to angiogenesis control in RCC.

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    This work was supported by institutional Grants (no 2010/52180-A) from Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP), Brazil and Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES), Brazil.

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