Der Stellenwert der Targeted-Therapie beim Nierenzellkarzinom

Discovery and validation of urinary biomarkers for detection of renal cell carcinoma

INTRODUCTION

Renal cell carcinoma (RCC) is often accompanied by non-specific symptoms. The increase of incidentally discovered small renal masses also presents a diagnostic dilemma. This study investigates whether RCC-specific peptides with diagnostic potential can be detected in urine and whether a combination of such peptides could form a urinary screening tool.

MATERIALS AND METHODS

For the discovery of RCC-specific biomarkers, we have employed CE-MS to analyze urine samples from patients with RCC (N=40) compared to non-diseased controls (N=68).

RESULTS AND DISCUSSION

86 peptides were found to be specifically associated to RCC, of which sequence could be obtained for 40. A classifier based on these peptides was evaluated in an independent set of 76 samples, resulting in 80% sensitivity and 87% specificity. The specificity of the marker panel was further validated in a historical dataset of 1077 samples including age-matched controls (N=218), patients with related cancer types and renal diseases (N=859). In silico protease prediction based on the cleavage sites of differentially excreted peptides, suggested modified activity of certain proteases including cathepsins, ADAMTS and kallikreins some of which were previously found to be associated to RCC.

CONCLUSIONS

RCC can be detected with high accuracy based on specific urinary peptides.

BIOLOGICAL SIGNIFICANCE

Clear cell renal cell carcinoma (RCC) has the highest incidence among the renal malignancies, often presenting non-specific or no symptoms at all. Moreover, with no diagnostic marker being available so far, almost 30% of the patients are diagnosed with metastatic disease and 30-40% of the patients initially diagnosed with localized tumor relapse. These facts introduce the clinical need of early diagnosis. This study is focused on the investigation of a marker model based on urinary peptides, as a tool for the detection of RCC in selected patients at risk. Upon evaluation of the marker model in an independent blinded set of 76 samples, 80% sensitivity and 87% specificity were reported. An additional dataset of 1077 samples was subsequently employed for further evaluation of the specificity of the classifier.

pS6 Expression in normal renal parenchyma, primary renal cell carcinomas and their metastases

In cancer therapy novel concepts focus on phosphoinositide-3-kinase/protein kinase B/mammalian target of rapamycin (mTOR) inhibitors. In this context, phosphorylated S6 protein of the 40S ribosomal subunit (pS6) overexpression was previously shown to be associated with sensitivity to inhibitors of mTOR. The present study therefore evaluated pS6 expression in normal renal parenchyma (NRP), primary renal cell carcinomas (PRCC) and their metastases. pS6 and pmTOR expression was immunohistochemically analyzed in a tissue microarray (TMA) from localized primary renal cell carcinoma (lPRCC) (n = 35), metastasized primary renal cell carcinoma (mPRCC) (n = 45), their metastases (n = 45), and NRP (n = 45). pS6 expression was stronger in mPRCCs and metastases than in NRP and lPRCCs (p < 0.05). In mPRCCs high-grade and high-stage tumors showed higher pS6 levels. pS6 overexpression was more frequently found in metastases (40/45; 88.9%) than in mPRCC (24/45; 53.3%) (p < 0.05). Overexpression of pS6 in metastases without concomitant overexpression in their primary tumors was found in 16/45 (35.56%) cases. Patients with pS6 overexpression in mPRCCs but also in metastases showed a tendency to shorter overall survival. pS6 score and pmTOR score correlated positively in NRP and in tumorous tissue (mPRCC and metastases). In conclusion, the present study showed stronger pS6 expression and more frequent overexpression in metastases than in corresponding PRCCs. In approximately one-third of the cases pS6 overexpression was found exclusively in metastases, which is interesting with regard to the association between high pS6 expression and sensitivity to mTOR inhibitor therapy.

[Systemic therapy of renal cell carcinoma]

Systemic therapy of metastatic renal cell carcinoma has completely changed in the last 5 years. Although a cure for the disease is still not achieved with systemic treatment in the majority of cases immunotherapy is no longer used. The therapeutic regiments are mainly based on angiogenic inhibitors such as sunitinib, sorafenib, pazopanib, everolimus and temsirolimus as well as the combination of bevacizumab with interferon. This article gives an overview of these treatment options and the clinical setting for their usage. To achieve a prolonged progression-free survival, a continuous therapy based on the new drugs is necessary. The major goal of the treatment remains to keep the disease stable as complete remission is only seen in 2-4% of cases. With these lengthy treatment regimes a schedule for sequenced administration of drugs is necessary for most of the patients. The optimal treatment sequence is unknown and should be chosen based on the individual course of the disease and the side effects as well as comorbidities. The role of neoadjuvant and adjuvant therapies remains unclear.

p-AKT overexpression in primary renal cell carcinomas and their metastases

In cancer therapy novel concepts focus on phosphoinositide 3-kinase (PI3K)/activated protein kinase B (p-AKT)/mammalian target of rapamycin (mTOR) inhibitors. In this context, p-AKT overexpression was previously shown to be associated with sensitivity to inhibitors of mTOR. The present study evaluated p-AKT expression in a tissue microarray of primary renal cell carcinomas (PRCCs) (n = 45), their metastases (primary onset n = 45, secondary onset n = 5), and normal renal parenchyma (n = 45) by means of immunohistochemistry. Total p-AKT overexpression was found in 24/45 (53.3%) PRCCs, in 32/45 (71.1%) primary and in 3/5 (60%) secondary onset metastases. Membranous p-AKT overexpression was seen more frequently in PRCCs, namely 11/45 (24.4%), than in primary onset metastases 1/45 (2.2%). Overexpression of total p-AKT solely in metastases without overexpression in PRCC was exclusively demonstrated in primary onset metastases, namely in 28.9%. Patients with total p-AKT overexpression in primary carcinomas showed a trend to longer, and those with total p-AKT overexpression in metastases a tendency to shorter survival. In conclusion, the present study shows total p-AKT overexpression to be more frequent in metastases than in PRCCs. Total p-AKT overexpression in metastases without concomitant overexpression in their primary tumors was found in approximately one-third of primary onset metastases, which is interesting with regard to the association between high p-AKT expression and sensitivity to mTOR inhibitor therapy.

[Volumetry of metastases from renal cell carcinoma: comparison with the RECIST criteria]

For patients with metastasized renal cell carcinoma (RCC), imaging techniques are of great importance. Currently, therapy widely relies on antiangiogenic factors, which frequently lead to relatively subtle changes in the size of lesions. From this aspect the commonly used RECIST criteria (response evaluation criteria in solid tumors) must be considered as imprecise for the evaluation of the response to therapy. This article gives a review on new software-based volumetric methods, which allow therapy-induced changes in the size of metastases from RCC to be detected with higher sensitivity and reproducibility. A comparison of RECIST and volumetry was carried out with data from patients with metastasized RCC to demonstrate the higher sensitivity of the 3D volumetric procedure.

[Value of lymph node dissection for renal cell carcinoma]

There are as yet no common standards regarding lymph node dissection during tumor nephrectomy. In order to assess prognoses and survival rates and ensure early detection of kidney tumors, a pathohistological staging following lymphadenopathy and new adjuvant therapies in metastatic disease have to be established in the future. The aims of lymph node dissection are - as far as the morbidity and performance status of the patient are concerned - accurate staging and a decrease in risk of tumor recurrence, particularly in organ-confined cancer disease.