Depletion of the C3 component of complement enhances the ability of rituximab-coated target cells to activate human NK cells and improves the efficacy of monoclonal antibody therapy in an in vivo model.

Growing evidence indicates antibody-dependent cellular cytotoxicity (ADCC) contributes to the clinical response to monoclonal antibody (mAb) therapy of lymphoma. Recent in vitro analysis suggests C3b can inhibit mAb-induced natural killer (NK)-cell activation and ADCC. Further studies were conducted to assess the effect of C3 depletion on mAb-induced NK activation and therapy of lymphoma. Normal human serum inhibited the ability of rituximab-coated lymphoma cells to activate NK cells as previously reported. Serum did not inhibit NK-cell activation when it was preincubated with cobra venom factor (CVF) to deplete C3. Similar results were found when transudative pleural fluid or nonmalignant ascites was used as surrogates for extravascular fluid, suggesting the inhibitory effect of complement may be present in the extravascular compartment, in which many malignant lymphocytes reside. In vivo, C3 was depleted before mAb treatment in a syngeneic murine model of lymphoma. Survival of lymphoma-bearing mice after treatment with CVF plus mAb and with a human C3 derivative with CVF-like functions (HC3-1496) plus mAb was both superior to that of mAb alone. These studies show that complement depletion enhances NK-cell activation induced by rituximab-coated target cells and improves the efficacy of mAb therapy in a murine lymphoma model.

Cigarette smoke induces cellular senescence via Werner's syndrome protein down-regulation.

RATIONALE: Werner's syndrome is a genetic disorder that causes premature aging due to loss-of-function mutations in a gene encoding a member of the RecQ helicase family. Both Werner's syndrome and cigarette smoking accelerate aging. No studies have examined the effect of cigarette smoke on Werner's syndrome protein. OBJECTIVES: To investigate the role of Werner's syndrome protein in cigarette smoke-induced cellular senescence. METHODS: Cellular senescence and amounts of Werner's syndrome protein were measured in fibroblasts isolated from patients with emphysema and compared with age-matched nonsmokers. The in vitro effects of cigarette smoke on amounts of Werner's syndrome protein, function, and senescence were also evaluated in primary human lung fibroblasts and epithelial cells. MEASUREMENTS AND MAIN RESULTS: Cultured lung fibroblasts isolated from patients with emphysema exhibited a senescent phenotype accompanied by a decrease in Werner's syndrome protein. Cigarette smoke extract decreased Werner's syndrome protein in cultured fibroblasts and epithelial cells. Werner's syndrome protein-deficient fibroblasts were more susceptible to cigarette smoke-induced cellular senescence and cell migration impairment. In contrast, exogenous overexpression of Werner's syndrome protein attenuated the cigarette smoke effects. CONCLUSIONS: Cigarette smoke induces cellular senescence and cell migration impairment via Werner's syndrome protein down-regulation. Rescue of Werner's syndrome protein down-regulation may represent a potential therapeutic target for smoking-related diseases.

Cigarette smoke induces cellular senescence.

Chronic obstructive pulmonary disease (COPD) is the fourth leading cause of death in the United States, and cigarette smoking is the major risk factor for COPD. Fibroblasts play an important role in repair and lung homeostasis. Recent studies have demonstrated a reduced growth rate for lung fibroblasts in patients with COPD. In this study we examined the effect of cigarette smoke extract (CSE) on fibroblast proliferative capacity. We found that cigarette smoke stopped proliferation of lung fibroblasts and upregulated two pathways linked to cell senescence (a biological process associated with cell longevity and an inability to replicate), p53 and p16-retinoblastoma protein pathways. We compared a single exposure of CSE to multiple exposures over an extended time course. A single exposure to CSE led to cell growth inhibition at multiple phases of the cell cycle without killing the cells. The decrease in proliferation was accompanied by increased ATM, p53, and p21 activity. However, several important senescent markers were not present in the cells at an earlier time point. When we examined multiple exposures to CSE, we found that the cells had profound growth arrest, a flat and enlarged morphology, upregulated p16, and senescence-associated beta-galactosidase activity, which is consistent with a classic senescent phenotype. These observations suggest that while a single exposure to cigarette smoke inhibits normal fibroblast proliferation (required for lung repair), multiple exposures to cigarette smoke move cells into an irreversible state of senescence. This inability to repair lung injury may be an essential feature of emphysema.