The preferential accumulation of sickle blood cells in
tumor vasculature is demonstrated noninvasively using MRI and sickle red blood cells loaded with
Gd-DTPA and invasively by two other techniques. The distribution of red blood cells in rat
brain tumors relative to normal brains were measured using three separate techniques: MRI of
Gd-DTPA loaded cells, fluorescent microscopy detection of
Oregon Green 488 fluorescence conjugated to a
streptavidin-
biotin complex that binds to red blood cell
surface proteins, and autoradiography using a
technetium (99m)Tc-labeling kit. Labeled red cells were infused intravenously in rats with
brain tumors. Sickle cells preferentially accumulated in
tumor relative to normal brain, with highest concentrations near the
tumor / normal tissue boundary, whereas control normal red cells did not preferentially aggregate at the
tumor periphery. This demonstrates the potential of sickle red blood cells to accumulate in the abnormal
tumor vessel network, and the ability to detect their aggregation noninvasively and at high spatial resolution using MRI. The application of the noninvasive measurement of sickle cells for imaging
tumor neovasculature, or as a delivery tool for
therapy, requires further study.