Renal Implications of Long-Term Systemic Bevacizumab for Recurrent Respiratory Papillomatosis

BACKGROUND

Bevacizumab is a vascular endothelial growth factor (VEGF) inhibitor that is used off-label for select cases of recurrent respiratory papillomatosis (RRP) that are severe, involve the distal airway or lung parenchyma, and refractory to other forms of adjuvant therapy. However, there is limited safety data for the use of bevacizumab in children and VEGF inhibitors are reported to have a range of adverse renal effects, including hypertension, proteinuria, and thrombotic microangiopathy (TMA).

CASE-DIAGNOSIS/TREATMENT

This report describes a case of severe juvenile-onset RRP that had an exceptionally high operative burden that was refractory to several adjuvant treatment strategies (including intralesional cidofovir and subcutaneous pegylated interferon). Bevacizumab treatment resulted in a dramatic and sustained improvement in disease control over a 5-year period. However, after 3 years of treatment, the patient developed hypertension and proteinuria and was found to have evidence of a glomerular TMA on kidney biopsy. These complications were successfully managed with a reduction in bevacizumab frequency and angiotensin-converting enzyme inhibitor initiation.

CONCLUSIONS

Clinicians caring for children treated with VEGF inhibitors should be aware of the potential renal complications and their management.

Podocytes-The Most Vulnerable Renal Cells in Preeclampsia

Preeclampsia (PE) is a disorder that affects 3–5% of normal pregnancies. It was believed for a long time that the kidney, similarly to all vessels in the whole system, only sustained endothelial damage. The current knowledge gives rise to a presumption that the main role in the development of proteinuria is played by damage to the podocytes and their slit diaphragm. The podocyte damage mechanism in preeclampsia is connected to free VEGF and nitric oxide (NO) deficiency, and an increased concentration of endothelin-1 and oxidative stress. From national cohort studies, we know that women who had preeclampsia in at least one pregnancy carried five times the risk of developing end-stage renal disease (ESRD) when compared to women with physiological pregnancies. The focal segmental glomerulosclerosis (FSGS) is the dominant histopathological lesion in women with a history of PE. The kidney’s podocytes are not subject to replacement or proliferation. Podocyte depletion exceeding 20% resulted in FSGS, which is a reason for the later development of ESRD. In this review, we present the mechanism of kidney (especially podocytes) injury in preeclampsia. We try to explain how this damage affects further changes in the morphology and function of the kidneys after pregnancy.

Overexpression of preeclampsia induced microRNA-26a-5p leads to proteinuria in zebrafish

So far the pathomechanism of preeclampsia in pregnancy is focussed on increased circulating levels of soluble fms-like tyrosin kinase-1 (sFLT-1) that neutralizes glomerular VEGF-A expression and prevents its signaling at the glomerular endothelium. As a result of changed glomerular VEGF-A levels endotheliosis and podocyte foot process effacement are typical morphological features of preeclampsia. Recently, microRNA-26a-5p (miR-26a-5p) was described to be also upregulated in the preeclamptic placenta. We found that miR-26a-5p targets VEGF-A expression by means of PIK3C2α in cultured human podocytes and that miR-26a-5p overexpression in zebrafish causes proteinuria, edema, glomerular endotheliosis and podocyte foot process effacement. Interestingly, recombinant zebrafish Vegf-Aa protein could rescue glomerular changes induced by miR-26a-5p. In a small pilot study, preeclamptic patients with podocyte damage identified by podocyturia, expressed significantly more urinary miR-26a-5p compared to healthy controls. Thus, functional and ultrastructural glomerular changes after miR-26a-5p overexpression can resemble the findings seen in preeclampsia and indicate a potential pathophysiological role of miR-26a-5p in addition to sFLT-1 in this disease.

Urinary podocyte excretion and proteinuria in patients treated with antivascular endothelial growth factor therapy for solid tumor malignancies

BACKGROUND

Urinary podocyte excretion (podocyturia) may function as a more specific marker of ongoing glomerular damage. This study sought to analyze the relationship between proteinuria and podocyturia in cancer patients treated with antivascular endothelial growth factor (anti-VEGF) agents.

METHODS

Thirty-seven patients treated with anti-VEGF medications were analyzed in a single-institution, cross-sectional study. Podocyte cultures were performed on random urine collections (50-100 ml), and podocytes were identified by positive podocin staining. The corresponding urine samples were analyzed for protein and creatinine (Cr) measurements.

RESULTS

Proteinuria ≥0.5 g/g Cr was found in 30% of the patients (median, 0.12; interquartile range, 0.04-0.86), and 62% had podocyturia. There was a significant difference in the amount of podocyturia between patients with proteinuria ≥0.5 g/g Cr and those with a value <0.5 g/g Cr (median podocyturia, 1.08 cells/mg Cr, range, 0-14.55 vs. 0.03 cells/mg Cr, range, 0-1.64, respectively; p < 0.001). A statistically significant correlation was observed between the cumulative dose of bevacizumab and both proteinuria (r = 0.48, p = 0.004) and podocyturia (r = 0.34, p = 0.045) as well as between proteinuria and podocyturia (r = 0.63, p < 0.001), suggesting that these are mechanistically related.

DISCUSSION

Ongoing podocyte loss may be mechanistically related to the onset and severity of proteinuria in patients treated with anti-VEGF agents.

Angiogenic inhibitors for older patients with advanced colorectal cancer: Does the age hold the stage?

Although major progress has been achieved in the treatment of advanced colorectal cancer (CRC) with the employment of antiangiogenic agents, several questions remain on the use of these drugs in older patients. Since cardiovascular, renal and other comorbidities are common in the elderly, an accurate assessment of the patients’ conditions should be performed before a treatment decision is made. Since most CRC patients enrolled in clinical trials testing antiangiogenic drugs were aged < 65 years, the efficacy and tolerability of these agents in elderly patients has not been adequately explored. Data suggest that patients with advanced CRC derive similar benefit from bevacizumab treatment regardless of age, but the advantage of other antiangiogenic drugs in the same class of patients appears more blurred. Literature data suggest that specific antiangiogenic-related toxicities such as hypertension or arterial thromboembolic events may be higher in the elderly than in the younger patients. In addition, it should be emphasized that the patients included in the clinical studies discussed herein were selected and therefore may not be representative of the usual elderly population. Advanced age alone should not discourage the use of bevacizumab. However, a careful patients’ selection and watchful monitoring of toxicities are required to optimize the use of antiangiogenics in this population.

VEGF inhibition, hypertension, and renal toxicity

The use of anti-angiogenic agents as part of the therapeutic armamentarium for advanced stage solid tumors has become the standard of care in several instances, particularly for renal cell carcinoma, non-small cell lung carcinoma, colorectal carcinoma, and gastrointestinal stromal tumors. These agents primarily target vascular endothelial growth factor (VEGF) and/or its receptors, and include bevacizumab, a humanized monoclonal antibody against VEGF, as well as tyrosine kinase inhibitors that target several receptor tyrosine kinases (RTK), including VEGF receptors. These therapies, as a general class of anti-angiogenic medications, have been shown to have common adverse vascular effects attributable directly or indirectly to their anti-VEGF effects, including hypertension, renal vascular injury, often manifested by proteinuria and thrombotic microangiopathy, and congestive heart failure. Knowledge of these common side effects and their underlying mechanisms may allow for more accurate and prompt diagnoses, timely clinical interventions, and the development of rational and standard treatments. These measures may minimize patient morbidity and mortality, not only by the treatment of side effects, but also by minimizing the disruption of treatment of the underlying malignancy, as well as improving patient quality of life.

Relevance of VEGF and nephrin expression in glomerular diseases

The glomerular filtration barrier is affected in a large number of acquired and inherited diseases resulting in extensive leakage of plasma albumin and larger proteins, leading to nephrotic syndrome and end-stage renal disease. Unfortunately, the molecular mechanisms governing the development of the nephrotic syndrome remain poorly understood. Here, I give an overview of recent investigations that have focused on characterizing the interrelationships between the slit diaphragm components and podocytes-secreted VEGF, which have a significant role for maintaining the normal podocyte structure and the integrity of the filtering barrier.

Renal involvement in preeclampsia: similarities to VEGF ablation therapy

Glomerular VEGF expression is critical for the maintenance and function of an intact filtration barrier. Alterations in glomerular VEGF bioavailability result in endothelial as well as in podocyte damage. Renal involvement in preeclampsia includes proteinuria, podocyturia, elevated blood pressure, edema, glomerular capillary endotheliosis, and thrombotic microangiopathy. At least the renal signs, symptoms, and other evidence can sufficiently be explained by reduced VEGF levels. The aim of this paper was to summarize our pathophysiological understanding of the renal involvement of preeclampsia and point out similarities to the renal side effects of VEGF-ablation therapy.