A method known as image cytometry provided new information about the role of exosomes in bladder cancer recurrence and progression.

Bladder tumors have a high recurrence rate and may progress to invasive or metastatic disease, so there is an urgent need to identify novel biomarkers and mechanisms of disease progression for therapeutic targeting, a research team led by Gopal Gupta, MD, of the Department of Urology at Loyola University Chicago in Maywood, Illinois reported in BioMed Research International. Exosomes, which are microvesicles secreted from cells, contain proteins, mRNA, and miRNA. Bladder cancer cell lines have been shown to shed exosomes that contain proteins important for tumor progression.

The uptake of bladder cancer–shed exosomes by recipient bladder cancer cells must be better understood and characterized, Dr. Gupta and associates explained. Flow cytometers, conical microscopes, and a technology that employs conventional optical microscope and laser light (Nanosight) are all used in this pursuit, yet all have their limitations.

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The study group used image cytometry as a novel method for both quantifying exosomes and measuring uptake by recipient bladder cancer cells. Like flow cytometry, image cytometry provides area of bright field and fluorescence intensity measurements, but also can quantify morphological features as seen through microscopy. Image cytometry showed how exosomes and their cargo can be transferred between cells—information that supported the study team’s hypothesis that shedding of exosomes from bladder tumors plays a key role in cancer metastasis.

Imaging cytometry allowed the investigators to establish the minimal number of exosomes and incubation time required to achieve cellular uptake, and to identify a strong direct correlation between number of bladder cancer cells and number of exosomes secreted by those cells.

“Taken together, our novel method of characterization of cellular uptake and internalization by bladder cancer cells could become invaluable for understanding the role of exosomes on bladder cancer recurrence and progression,” concluded the study authors. “Furthermore, the ability to study the biology of exosome uptake in cancer cells in an unbiased, quantitative, and reproducible manner will enable standardization of exosome functional studies.”