Background Lung cancer causes 6% of UK deaths with 20% due to infection1,2. The reason is multifactorial with myelosuppression secondary to chemotherapy being a contributor. However, the effect of chemotherapy drugs on the function of peripheral neutrophils has rarely been explored. It is proposed carboplatin and gemcitabine may decrease the function of circulating neutrophils that are present, causing a poorer response to infection by neutrophils that are present. Granulocyte-macrophage colony-stimulating factor (GM-CSF) is used to stimulate neutrophil production in febrile neutropenic patients on chemotherapy, however studies show it also improves mature neutrophil function3,4. The aim was to research the effect of carboplatin and gemcitabine on neutrophil phagocytic function and to determine whether GM-CSF reverses any deficit seen in phagocytosis.
Methods Neutrophils isolated from healthy donor blood by dextran sedimentation followed by discontinuous Percoll gradient. Untreated neutrophils compared with those pre-incubated with carboplatin, gemcitabine or both drugs (10-4 mM). Phagocytosis assessed by ingestion of serum-opsonised zymosan. Repeated with 30 minute GM-CSF (5 ng/ml) pre-incubation. Apoptosis analysed by flow cytometry. All cells incubated for 2 hours untreated or with single or both chemotherapeutic agents (10-4 mM) or phorbol 12-myristate 13-acetate (PMA) for 30 minutes. Cells stained with APC-Annexin V to detect apoptosis and propidium iodide to distinguish early and late apoptotic cells.
Results A significant decrease in percentage phagocytosis occurred with chemotherapy drugs compared to untreated neutrophils: carboplatin p = < 0.001, gemcitabine p = < 0.01, carboplatin and gemcitabine p = < 0.05. GM-CSF caused a significant increase in percentage phagocytosis when gemcitabine caused a deficit (p = < 0.05) with a 9–13% increasing trend seen in other conditions. No difference in apoptosis occurred between untreated (median 3.9%) and chemotherapy treated neutrophils (median: carboplatin 4.4%, gemcitabine 4.9%, carboplatin and gemcitabine 3.6%).
Conclusions This study demonstrated that phagocytosis is impaired by carboplatin and gemcitabine in healthy volunteer blood. Therefore it is proposed a reduced response to infection may also occur in lung cancer patients given these drugs, contributing to mortality. There was no difference in apoptosis, suggesting an alternative mechanism of action. Further study is required to explore the mechanism of action and the effect of GM-CSF on phagocytosis following chemotherapy.
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