Abstract
Hoechst 33342 is a fluorescent dye used for cell selection from tumours based upon intratumour location. When the dye is administered i.v. to tumour-bearing animals, cellular fluorescence is directly related to the proximity of cells to blood vessels. The present study compared inherent Hoechst fluorescence between in vitro-stained EMT6/Ro (mouse mammary sarcoma) cells and host cells, to determine if these populations have different staining characteristics that may influence cell selection procedures. Tumour cell fluorescence exceeded host cell staining by 8-fold when pure cell populations (EMT6/Ro monolayer cells, mouse spleen and peritoneal cells) were compared, and 3-fold for tumour cell-enriched and host cell-enriched populations from solid tumours. Inherent uptake of HO 33342 appeared to be correlated with cell volume. These differences in inherent dye uptake between host and tumour cells were found to be minor in comparison to the fluorescence gradient between the 10% brightest and 10% dimmest (78-fold) cell populations from in vivo-stained tumours.
Highlights
Many types of murine and human tumours are significantly infiltrated by host cells, primarily macrophages, neutrophils, and lymphocytes (Witz & Hanna, 1980)
BALB/c mice were euthanized by cervical dislocation, and peritoneal cells were collected by lavage with balanced salt solution (BSS) containing 5 U ml- 1 heparin
Fluorescence appeared to be related to cell volume for the various cell types
Summary
Many types of murine and human tumours are significantly infiltrated by host cells, primarily macrophages, neutrophils, and lymphocytes (Witz & Hanna, 1980). Studies of HO33342 for cell selection in tumours have until now focused primarily upon staining of the tumour cell population, and direct comparisons of Hoechst staining of host and tumour cells have not been made. In order for HO 33342 to be useful for selection of cells based upon location with tumours, it is necessary that significant differences in fluorescence intensity between cells result only from differences in location and not from inherent variations in staining between host and tumour cells. The objectives of the present study were to compare inherent HO 33342 fluorescence between host and tumour cells, and to determine the usefulness of HO 33342 staining as a method for cell selection in the EMT6 mouse mammary tumour, which contains a significant proportion of infiltrated host cells (Lord, 1980)
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