Rigid plasma‐membrane‐derived vesicles, enriched in tumour‐associated surface antigens (MLr), occurring in the ascites fluid of a murine leukaemia (GRSL)

Abstract

Extracellular membraneous vesicles of GRSL leukaemia cells were isolated from the ascites fluid bathing the cells in vivo, and from cell washes. Mammary tumour virus-induced antigens (MLr) expressed on the surface of the cells are enriched on these vesicles as compared to plasma membranes isolated from the cell homogenate. The lipid fluidity of the vesicles is much smaller than that of the plasma membranes, and the content of the pertinent lipid parameters, cholesterol and sphingomyelin, are accordingly greatly increased. The extracellular vesicles which are also enriched in sialic acid and 5'-nucleotidase are apparently derived from the plasma membrane, probably at least partly by exfoliation of selected parts or domains of the surface of living cells. An analogy between this shedding of vesicles, the formation of endocytotic vesicles and the budding of viruses is noted; all these processes select or assemble rigid lipid domains of the cell membrane. The possible participation of surface microvilli and sub-lethal autolysis in the process of shedding is discussed.

Mechanisms by which docosahexaenoic acid and related fatty acids reduce colon cancer risk and inflammatory disorders of the intestine

“…Given that exfoliated vesicles normally arise from non-random regions of the cell surface [Armstrong, 1988;Beaudoin, 1991;Black, 1980;Taylor, 1988;van Blitterswijk, 1979], these data clearly indicate that cellular lipid environment can influence the lipid composition and structure of vesicles formed therein.…”

Modulation of prostate cancer growth in bone microenvironments

“…Shed membrane vesicles are implicated in cancer cell escape from immune responses, the induction of angiogenesis, and the spread of metalloproteinase activity [Wood et al, 1997; Kim et al, 2002]. Membrane vesicles, derived of specific regions of the plasma membrane [van Blitterswijk et al, 1979, 1982; Lerner et al, 1983] and enriched in tumor cell surface antigens are shed both in vitro and in vivo. Interestingly, vesicle quantities in patient serum appear to correlate with cell invasiveness and tumor load [Dolo et al, 1994, 1995, 1998; Ginestra et al, 1998, 1999; Dolo et al, 1999].…”

Accumulation of an alkyl lysophospholipid in tumor cell membranes affects membrane fluidity and tumor cell invasion

“…A crude nuclear fraction was obtained by centrifugation twice at 1000 x g for 10 min, with intermittent washing. Plasma membranes were purified from (1.95-945).104 g.min pellets, utilizing a discontinuous sucrose gradient, as described in detail (8). The purity of the plasma membrane preparations was ascertained routinely by electron microscopy and by marker assays, as described (8).…”