Impaired platelet aggregation in melanoma patients treated with interferon-alpha-2b adjuvant therapy

Tetherin/BST2, a physiologically and therapeutically relevant regulator of platelet receptor signalling

The reactivity of platelets, which play a key role in the pathogenesis of atherothrombosis, is tightly regulated. The integral membrane protein tetherin/bone marrow stromal antigen-2 (BST-2) regulates membrane organization, altering both lipid and protein distribution within the plasma membrane. Because membrane microdomains have an established role in platelet receptor biology, we sought to characterize the physiological relevance of tetherin/BST-2 in those cells. To characterize the potential importance of tetherin/BST-2 to platelet function, we used tetherin/BST-2-/- murine platelets. In the mice, we found enhanced function and signaling downstream of a subset of membrane microdomain-expressing receptors, including the P2Y12, TP thromboxane, thrombin, and GPVI receptors. Preliminary studies in humans have revealed that treatment with interferon-α (IFN-α), which upregulates platelet tetherin/BST-2 expression, also reduces adenosine diphosphate-stimulated platelet receptor function and reactivity. A more comprehensive understanding of how tetherin/BST-2 negatively regulates receptor function was provided in cell line experiments, where we focused on the therapeutically relevant P2Y12 receptor (P2Y12R). Tetherin/BST-2 expression reduced both P2Y12R activation and trafficking, which was accompanied by reduced receptor lateral mobility specifically within membrane microdomains. In fluorescence lifetime imaging-Förster resonance energy transfer (FLIM-FRET)-based experiments, agonist stimulation reduced basal association between P2Y12R and tetherin/BST-2. Notably, the glycosylphosphatidylinositol (GPI) anchor of tetherin/BST-2 was required for both receptor interaction and observed functional effects. In summary, we established, for the first time, a fundamental role of the ubiquitously expressed protein tetherin/BST-2 in negatively regulating membrane microdomain-expressed platelet receptor function.

Side effects of interferon-alpha therapy

AIM

Interferon-alpha (IFN-alpha) has been extensively explored for its efficacy in various disease conditions and is currently used as a standard treatment in several of these. Its use is accompanied by a wide variety of possible side effects. These side-effects may hamper reaching and maintaining the dose needed for maximal therapeutic effect while their occurrence can outweigh clinical benefit of IFN-alpha treatment. This review addresses the toxicity profile of IFN-alpha, the presumed pathophysiology of the different side effects and the strategies to handle these.

METHODS

Computerized searches were used and cross-references of articles and books were checked.

RESULTS

Adverse effects due to IFN-alpha have been described in almost every organ system. Many side-effects are clearly dose-dependent. Taken together, occurrence of flu-like symptoms, hematological toxicity, elevated transaminases, nausea, fatigue, and psychiatric sequelae are the most frequently encountered. Although insight in the mechanisms accounting for IFN-alpha-related toxicities has improved in recent years, much remains to be elucidated. Guidelines on the management of these untoward sequelae are mostly based on clinical experience, while many side-effects can only be adequately handled by dose adjustment or cessation of treatment.

CONCLUSION

Further research on the mechanisms underlying both therapeutic effects and adverse events is warranted. Hopefully, this will lead to better identification of those patients who are likely to benefit from treatment without experiencing severe toxicities.

Anaesthetic implications of anticancer chemotherapy

In anaesthetic practice we deal with cancer patients who are scheduled for operations on tumours or other manifestations of malignant disease. Those patients are often debilitated and have significant weight loss accompanied with hypoproteinaemia, anaemia and coagulation disorders. Oncological patients usually present to the anaesthetist before tumour disease surgery, but they are also candidates for elective operations (e.g. hernia repair) and urgent/emergency surgery (e.g. trauma, fractures and ileus). Chemotherapeutic agents given to these patients are potentially noxious, can affect the conduct of anaesthesia and, furthermore, may aggravate the patient's condition. In this review the most commonly used cytostatic drug regimens and their common side-effects are listed. Some preclinical studies on anaesthetic and cytostatic drug metabolism and interactions are emphasized, as well as clinically relevant perioperative alterations that may affect anaesthetic management in cancer patients. An anaesthetist may have to modify a routine anaesthetic regimen in cancer patients especially if anticancer chemotherapeutics were given. Clinically silent toxic drug effects may become apparent during operation, trauma or in the early postoperative course in such patients. Altered reactions to commonly used anaesthetics in patients receiving chemotherapeutics and an impaired stress reaction may occur in such patients. Special attention must be drawn to protection against opportunistic infections.