Cell–cell contacts trigger programmed necrosis and induce cyclooxygenase-2 expression

Abstract

Necrosis was induced by cell-cell contacts of human dermal fibroblasts in three-dimensional culture. Dramatic induction of cyclooxygenase-2 (COX-2) expression was found throughout these necrotizing cell clusters, whereas no increase in expression of apoptosis markers was seen. The cells were rapidly committed to necrosis, and the process could not be reversed by allowing them to spread and adhere on a solid substrate. Induction of COX-2 expression was accompanied by greatly enhanced production of the prostaglandins E 2 , I 2 , and F 2a . When applied exogenously on necrotizing clusters, these prostaglandins delayed cell clustering and further enhanced COX-2 expression. Abolishing prostaglandin production by NS-398 or indomethacin reduced cell membrane damage (as measured by lactate dehydrogenase release into the culture medium). We also identified aenolase-mediated plasminogen activation as the major extracellular proteolytic executor of necrotic cell death. In contrast to inhibition of COX-2, inhibition of plasminogen activation failed to inhibit membrane damage associated with necrosis. Intracellular proteolysis, by caspases, was shown to take part in COX-2 induction. Taken together, our results indicate that cell-cell contacts induce an actively programmed necrotic process that functionally involves COX-2, a known hallmark of inflammation and cancer.

Nemosis of fibroblasts is inhibited by benign HaCaT keratinocytes but promoted by malignant HaCaT cells

“…Nemotic fibroblast clusters produce vast amounts of proinflammatory, proteolytic, angiogenic and growth-promoting factors, all of which are associated with the activation of inflammatory processes and invasiveness of cancer cells (Bizik et al, 2004;Zha et al, 2004;Kankuri et al, 2005). In this study we investigated the role of keratinocytes in the modulation of fibroblast nemosis.…”

“…The aggressive phenotype of spheroids activates the extracellular cascade of plasminogen activation and increased expression of matrix metalloproteinases (MMP-1, -10 and MT1-MMP) (Siré n et al, 2006). The a-enolase mediated activation of plasminogen is a proteolytic executor of necrotic death, and no increase in apoptotic markers is seen (Bizik et al, 2004).…”

“…This phenomenon of fibroblast activation, which induces a massive proinflammatory, proteolytic and growth factor response promoting tumor invasion and terminating in programmed necrosis, has been designated as nemosis (from Nemesis, The Greek Goddess of Retribution and Inevitable Consequence) (Bizik et al, 2004;Kankuri et al, 2005;Siré n et al, 2006;Vaheri, in press). A hallmark of this cell activation is the induction of cyclooxygenase-2 (COX-2) expression, commonly associated with inflammation and tumor progression (Bizik et al, 2004;Zha et al, 2004). The aggressive phenotype of spheroids activates the extracellular cascade of plasminogen activation and increased expression of matrix metalloproteinases (MMP-1, -10 and MT1-MMP) (Siré n et al, 2006).…”

Inflammatory environment created by fibroblast aggregates induces growth arrest and phenotypic shift of human myeloma cells

“…Spheroid formation was initiated as described previously [19]. Briefly, U bottom 96-well plates (TPP, Trasadingen, Switzerland) were treated with 0.8% SeaKem LE agarose (Lonza, Rockland, ME) prepared in sterile water to form a thin film of non-adhesive surface.…”

“…Nemosis, which is triggered solely by cell-cell contacts, is programmed process of cell activation and subsequent death, the most distinctly observed in human dermal fibroblasts [19]. These activated fibroblasts are characterized by production of inflammation-associated cytokines and growth factors, e.g., IL-1, IL-6, IL-8, IL-11, LIF, GM-CSF, as well as, COX-2 related-secretion of prostaglandins [20].…”