Developing a new urine cell flow cytometry analysis of pdl1 expression and DNA content for diagnosis of bladder cancer
Alanee SR, Deebajah M, Chen P, Wang X, and Patterson BK. Developing a new urine cell flow cytometry analysis of pdl1 expression and DNA content for diagnosis of bladder cancer. J Clin Oncol 2019; 37.
J Clin Oncol
Background: Bladder cancer is the fifth most common cancer in the United States. PD1/PDL1, a pathway used by cancer cells to evade immune response, correlates with bladder cancer severity and has emerged as a target in bladder cancer treatment. Chromosomal instability is also a prominent feature associated with the development of bladder cancer. A method for unbiased analysis of PDL1 expression and DNA content in cells from urine samples promises to be a new test for diagnosis of bladder cancer. Methods: To evaluate the PDL1 expression and DNA content, we developed a 4color flow assay. Cells in voided urine samples were pelleted, fixed in incellMAX (IncellDx Inc.) and stained with antibodies against pancytokeratin (CK), CD45, PDL1 and a cell cycle dye. The stained samples were analyzed by a flow cytometer alongside stained control cells. Results: Fifty bladder cancer patient and 15 normal donor urine samples were collected and tested with this assay. We could distinguish epithelial cells (panCK+) and white blood cells (WBCs, CD45+) in urine samples and obtain PDL1 expression and DNA content information simultaneously from these cell populations. The patient samples showed a significantly higher percentage of WBCs with substantial PDL1 expression (P < 0.001). The percentage of PDL1 positive epithelial cells was not distinguishable between normal donor and patient samples. However increased post G1 epithelial cells ( > 5%) were observed in a majority of bladder cancer patients, with around 25% of samples showing a DNA index above 1.05. Conclusions: We developed a flow cytometry-based method to investigate PDL1 and DNA content simultaneously in cells from urine samples that could provide us with a new method to accurately identify bladder cancer patients through urine testing.