Book of abstract 2008

Plasma-mediated attractive interaction between membraneous structures
as a possible suppressive mechanism of tumor progression
Vid Janša1, Karin Schara2, Nejc Tomšič1, Janez Pavlič3, Rado Janša4, Roman Jerala5,
Veronika Kralj Iglič1
1Laboratory of Clinical Biophysics, Faculty of Medicine, University of Ljubljana, Slovenia; 2Dept. of
Orthopaedic Surgery, University Clinical Centre Ljubljana, Slovenia; 3University College for Health
Care, University of Ljubljana, Slovenia; 4Clinical Dept. of Gastroenterology, University Clinical Centre
Ljubljana, Slovenia; 5Dept. of Biotechnology, National Institute of Chemistry, Slovenia
Microvesicles shed from membranes of different cells can be considered as extracellular
organelles which convey communication between distant cells. In particular, tumorreleased
microvesicles in cancer patients are suggested to be involved in tumor progression.
It was recently shown that the plasma protein-mediated attractive interaction between
phospholipid membranes could in the budding process cause adhesion of the bud to the
mother membrane. Since in the in vivo conditions, the budding of cell membranes leads to
the release of microvesicles into the circulation, a hypothesis is put forward that the ability
of plasma to cause adhesion between membranes may prevent microvesiculation and
thereby supresses progression of cancer. According to the hypothesis, in cancer patients
with plasma which induces a more pronounced adhesion between membranes, the number
of MVs in the peripheral blood is smaller. The hypothesis was tested on 5 patients with
gastrointestinal cancer and 16 patients with other gastrointestinal diseases. The extent of
plasma–induced adhesion between membranes was determined by assessing the average
effective angle of contact between giant phospholipid vesicles created by electroformation
method; larger average effective angle of contact corresponds to a more pronounced
adhesion. The number of microvesicles isolated from peripheral blood was determined by
flow cytometry. It was found that patients with gastrointestinal cancer had larger number of
microvesicles (difference 140%, statistical significance 0.033) and smaller average effective
angle of contact (difference 20%, statistical significance 0.013) compared to patients with
other gastrointestinal diseases, which is in favor of the above hypothesis.
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