How cancer cells attach to urinary bladder epithelium in vivo: study of the early stages of tumorigenesis in an orthotopic mouse bladder tumor model
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The majority of bladder cancers in humans are non-muscle-invasive cancers that recur frequently after standard treatment procedures. Mouse models are widely used to develop anti-tumor treatments. The purpose of our work was to establish an orthotopic mouse bladder tumor model and to explore early stages of implantation of cancerous MB49 cells in vivo using various labeling and microscopic techniques. To distinguish cancer cells from normal urothelial cells in mouse urinary bladders, we performed molecular characterization of MB49 cells before intravesical injection experiments. In this new approach we applied internalized metal nanoparticles to unequivocally discriminate cancer cells from normal cells. This method revealed that cancer cells attached to the urothelium or basal lamina within just 1 hour of intravesical injection, whereas small tumors and localized hyperplastic urothelial regions developed within two days. We found that cancer cells initially adhere to normal urothelial cells through filopodia and by focal contacts with basal lamina. This is the first in vivo characterization of intercellular contacts between cancerous and normal urothelial cells in the bladder. Our study yields new data about poorly known early events of tumorigenesis in vivo, which could be helpful for the translation into clinic.
KeywordsOrthotopic bladder tumor Mouse model Urinary bladder Urothelium Cancer cells Cell adhesion
This research work was supported by the Slovenian Research Agency (ARRS) (grant no. P3-0108 and grant no. J3-7494). Authors kindly thank Tjaša Bigec for the help with the fluorescence microscopy analysis. Authors also express gratitude Dr. Julian Venables (Science Sense) for correcting the English.
Compliance with ethical standards
Conflict of interest
The authors declare that they have no conflict of interest.
All applicable international, national, and institutional guidelines for the care and use of animals were followed. Additionally, all procedures performed in studies involving animals were in accordance with the ethical standards of the institution at which the studies were conducted.
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