Effects of Cancer Presence and Therapy on the Platelet Proteome.

Platelets are involved in tumor angiogenesis and cancer progression. Previous studies indicated that cancer could affect platelet content. In the current study, we investigated whether cancer-associated proteins can be discerned in the platelets of cancer patients, and whether antitumor treatment may affect the platelet proteome. Platelets were isolated from nine patients with different cancer types and ten healthy volunteers. From three patients, platelets were isolated before and after the start of antitumor treatment. Mass spectrometry-based proteomics of gel-fractionated platelet proteins were used to compare patients versus controls and before and after treatment initiation. A total of 4059 proteins were detected, of which 50 were significantly more abundant in patients, and 36 more in healthy volunteers. Eight of these proteins overlapped with our previous cancer platelet proteomics study. From these data, we selected potential biomarkers of cancer including six upregulated proteins (RNF213, CTSG, PGLYRP1, RPL8, S100A8, S100A9) and two downregulated proteins (GPX1, TNS1). Antitumor treatment resulted in increased levels of 432 proteins and decreased levels of 189 proteins. In conclusion, the platelet proteome may be affected in cancer patients and platelets are a potential source of cancer biomarkers. In addition, we found in a small group of patients that anticancer treatment significantly changes the platelet proteome.

Platelet function is disturbed by the angiogenesis inhibitors sunitinib and sorafenib, but unaffected by bevacizumab.

INTRODUCTION: At the clinical introduction of antiangiogenic agents as anticancer agents, no major toxicities were expected as merely just endothelial cells (ECs) in tumors would be affected. However, several (serious) toxicities became apparent, of which underlying mechanisms are largely unknown. We investigated to what extent sunitinib (multitargeted antiangiogenic tyrosine kinase inhibitor (TKI)), sorafenib (TKI) and bevacizumab [specific antibody against vascular endothelial growth factor (VEGF)] may impair platelet function, which might explain treatment-related bleedings. MATERIALS AND METHODS: In vitro, the influence of sunitinib, sorafenib, and bevacizumab on platelet aggregation, P-selectin expression and fibrinogen binding, platelet-EC interaction, and tyrosine phosphorylation of c-Src was studied by optical aggregation, flow cytometry, real-time perfusion, and western blotting. Ex vivo, platelet aggregation was analyzed in 25 patients upon sunitinib or bevacizumab treatment. Concentrations of sunitinib, VEGF, and platelet and EC activation markers were measured by LC-MS/MS and ELISA. RESULTS: In vitro, sunitinib and sorafenib significantly inhibited platelet aggregation (20 µM sunitinib: 71.3%, p < 0.001; 25 µM sorafenib: 55.8%, p = 0.042). Sorafenib and sunitinib significantly inhibited P-selectin expression on platelets. Exposure to both TKIs resulted in a reduced tyrosine phosphorylation of c-Src. Ex vivo, within 24 h sunitinib impaired platelet aggregation (83.0%, p = 0.001, N = 8). Plasma concentrations of sunitinib, VEGF, and platelet/EC activation markers were not correlated with disturbed aggregation. In contrast, bevacizumab only significantly impaired platelet aggregation in vitro at high concentrations, but not ex vivo. CONCLUSION: Sunitinib significantly inhibits platelet aggregation in patients already after 24 h of first administration, whereas bevacizumab had no effect on aggregation. These findings may explain the clinically observed bleedings during treatment with antiangiogenic TKIs.

Pazopanib-related tumor lysis syndrome in metastatic clear cell renal cell carcinoma: a case report.

Introduction Tumor lysis syndrome (TLS) is a life-threatening emergency caused by rapid cell death as a result of anti-tumor therapy. In the era of targeted therapy it has increasingly been observed in solid malignancies such as hepatocellular carcinoma (HCC) and renal cell carcinoma (RCC). Case We describe the case of a 58-year old man with the medical history of a memorial sloan kettering cancer centre (MSKCC) poor prognosis metastasized clear cell renal cell carcinoma (mRCC) who developed TLS within six days after initiating therapy with the tyrosine kinase inhibitor (TKI) pazopanib. Discussion The pharmacokinetics and pharmacodynamics of pazopanib are complex and characterized by a non-linear and time-dependent bioavailability. Pazopanib is almost completely bound to serum albumin (>99.9%). In this presented case, a low serum albumin (26 g/L) might have led to a higher free fraction of pazopanib, which could have resulted in more toxicity. Also, pazopanib is metabolised by the CYP3A4 isoform of the cytochrome P450 group. Low quantities of this enzyme may lead to an impaired and prolonged breakdown of the drug. Conclusion As far as we know this is the first report on pazopanib induced TLS. We advise further research in order to identify the exact mechanism behind TKI-induced TLS and the patients at risk of developing TLS.

A functional bioassay to determine the activity of anti-VEGF antibody therapy in blood of patients with cancer.

BACKGROUND: Only a small proportion of patients respond to anti-VEGF therapy, pressing the need for a reliable biomarker that can identify patients who will benefit. We studied the biological activity of anti-VEGF antibodies in patients' blood during anti-VEGF therapy by using the Ba/F3-VEGFR2 cell line, which is dependent on VEGF for its growth. METHODS: Serum samples from 22 patients with cancer before and during treatment with bevacizumab were tested for their effect on proliferation of Ba/F3-VEGFR2 cells. Vascular endothelial growth factor as well as bevacizumab concentrations in serum samples from these patients were determined by enzyme linked immunosorbent assay (ELISA). RESULTS: The hVEGF-driven cell proliferation was effectively blocked by bevacizumab (IC50 3.7 µg ml-1; 95% CI 1.7-8.3 µg ml-1). Cell proliferation was significantly reduced when patients' serum during treatment with bevacizumab was added (22-103% inhibition compared with pre-treatment). Although bevacizumab levels were not related, on-treatment serum VEGF levels were correlated with Ba/F3-VEGFR2 cell proliferation. CONCLUSIONS: We found that the neutralising effect of anti-VEGF antibody therapy on the biological activity of circulating VEGF can be accurately determined with a Ba/F3-VEGFR2 bioassay. The value of this bioassay to predict clinical benefit of anti-VEGF antibody therapy needs further clinical evaluation in a larger randomised cohort.

Rapid decrease in delivery of chemotherapy to tumors after anti-VEGF therapy: implications for scheduling of anti-angiogenic drugs.

Current strategies combining anti-angiogenic drugs with chemotherapy provide clinical benefit in cancer patients. It is assumed that anti-angiogenic drugs, such as bevacizumab, transiently normalize abnormal tumor vasculature and contribute to improved delivery of subsequent chemotherapy. To investigate this concept, a study was performed in non-small cell lung cancer (NSCLC) patients using positron emission tomography (PET) and radiolabeled docetaxel ([(11)C]docetaxel). In NSCLC, bevacizumab reduced both perfusion and net influx rate of [(11)C]docetaxel within 5 hr. These effects persisted after 4 days. The clinical relevance of these findings is notable, as there was no evidence for a substantial improvement in drug delivery to tumors. These findings highlight the importance of drug scheduling and advocate further studies to optimize scheduling of anti-angiogenic drugs.

Blood platelets contain tumor-derived RNA biomarkers.

Diagnostic platforms providing biomarkers that are highly predictive for diagnosing, monitoring, and stratifying cancer patients are key instruments in the development of personalized medicine. We demonstrate that tumor cells transfer (mutant) RNA into blood platelets in vitro and in vivo, and show that blood platelets isolated from glioma and prostate cancer patients contain the cancer-associated RNA biomarkers EGFRvIII and PCA3, respectively. In addition, gene-expression profiling revealed a distinct RNA signature in platelets from glioma patients compared with normal control subjects. Because platelets are easily accessible and isolated, they may form an attractive platform for the companion diagnostics of cancer.

Antiangiogenic tyrosine kinase inhibition related gastrointestinal perforations: a case report and literature review.

Anti-VEGF (vascular endothelial growth factor) therapy with the monoclonal antibody bevacizumab can cause gastrointestinal (GI) perforations. In recent years it became apparent that GI perforations also occur during treatment with antiangiogenic tyrosine kinase inhibitors (TKIs). It is of clinical importance to consider (vague) abdominal complaints during antiangiogenic treatment as a sign of a GI perforation. To illustrate this serious complication, we report four cases of antiangiogenic treatment related GI perforations. In three cases this was due to antiangiogenic TKI treatment. Reported risk factors of GI perforations due to bevacizumab include the presence of a primary tumor in situ and recent history of endoscopy or abdominal radiotherapy. Pathology assessments of surgical removal of the perforated intestinal part reveal that perforations are predominantly seen at the tumor or anastomotic site, in case of carcinomatosis or diverticulitis or when GI obstruction or an intra-abdominal abscess is present. Whether the same risk factors may be involved in antiangiogenic TKI related GI perforations is unknown. The underlying mechanisms responsible for GI perforation during antiangiogenic treatment is unknown, but disturbance of host cell homeostasis of immune cells as well as platelet-endothelial cell interactions may play an important role. In conclusion, while clinical awareness that antiangiogenic treatment can cause GI perforations is critical for current medical practice, it is also very important to get more insight in its underlying mechanisms so that this life-threatening complication may be prevented in the near future.