Modulation of plasma complement by the initial dose of epirubicin/docetaxel therapy in breast cancer and its predictive value.

BACKGROUND: Despite the widespread use of neoadjuvant chemotherapy in breast cancer patients, prediction of individual response to treatment remains an unsolved clinical problem. Particularly, administration of an inefficient chemotherapeutic regimen should be avoided. Therefore, a better understanding of the molecular mechanisms underlying response to neoadjuvant chemotherapy is of particular clinical interest. Aim of the present study was to test whether neoadjuvant chemotherapy with epirubicin/docetaxel induces early changes in the plasma proteome of breast cancer patients and whether such changes correlate with response to therapy. METHODS: Plasma samples of 25 breast cancer patients obtained before and 24 h after initiation of epirubicin/docetaxel-based neoadjuvant chemotherapy were analysed using two-dimensional differential gel electrophoresis (2D-DIGE). Protein spots found to be differentially expressed were identified using mass spectrometry and then correlated with the pathological response after six cycles of therapy. Markers identified in a discovery set of patients (n=12) were confirmed in an independent validation set (n=13). RESULTS: 2D-DIGE revealed 33 protein spots to be differentially expressed in response to chemotherapy, including the complement factors C1, C3 and C4, inter-α-trypsin inhibitor, α-1-antichymotrypsin and α-2-Heremans-Schmid glycoprotein (AHSG). With respect to cytokines, only interleukin (IL)-6, IL-10 and soluble intracellular adgesion molecule 3 (sICAM3) were minimally modulated. Moreover, two protein spots within the complement component C3 significantly correlated with response to therapy. CONCLUSION: We have identified acute phase proteins and the complement system as part of the early host response to epirubicin/docetaxel chemotherapy. As complement C3 cleavage correlates with the efficacy of docetaxel/epirubicin-based chemotherapy, it has the potential as an easily accessible predictive biomarker.

Serum-dependent processing of late apoptotic cells for enhanced efferocytosis.

Binding of the serum protein complement component C1q to the surface of dying cells facilitates their clearance by phagocytes in a process termed efferocytosis. Here, we investigate during which phase of apoptotic cell death progression C1q binding takes place. Purified C1q was found to bind to all dying cells and, albeit weaker, also to viable cells. The presence of serum abrogated completely the binding to viable cells. In addition, C1q binding to dying cells was limited to a specific subpopulation of late apoptotic/secondary necrotic cells. Co-culturing serum-treated apoptotic cells with human monocytes revealed a much higher phagocytosis of C1q-positive than of C1q-negative late apoptotic/secondary necrotic cells. But this phagocytosis-promoting activity could not be observed with purified C1q. Serum-treated C1q-positive late apoptotic/secondary necrotic cells exhibited a similar volume, a similar degraded protein composition, but a much lower DNA content in comparison with the remaining late apoptotic/secondary necrotic cells. This was mediated by a serum-bound nuclease activity that could be abrogated by G-actin, which is a specific inhibitor of serum DNase I. These results show that serum factors are involved in the prevention of C1q binding to viable cells and in the processing of late apoptotic/secondary necrotic cells promoting cell death progression toward apoptotic bodies. This process leads to the exposure of C1q-binding structures and facilitates efferocytosis.