Multicolor quantum dots ID rare cancer cells

Charles T. Troy, charlie.troy@photonics.com

Multicolor quantum dots linked to antibodies can distinguish the Reed-Sternberg cells characteristic of Hodgkin’s lymphoma, according to researchers at Emory University and Georgia Institute of Technology (Georgia Tech).

“Our multicolor quantum dot staining method provides rapid detection and identification of rare malignant cells from heterogeneous tissue specimens,” said Dr. Shuming Nie, the Wallace H. Coulter distinguished professor in the Coulter department of biomedical engineering at Georgia Tech and Emory. The department was created jointly by the Emory University School of Medicine and the Georgia Tech College of Engineering.

“The clinical utility is not limited to Hodgkin’s lymphoma but potentially could be extended to detect cancer stem cells, tumor-associated macrophages and other rare cell types,” Nie said.

Quantum dots can be chemically linked to antibodies, which can detect molecules present on the surfaces or internal parts of cancer cells.

As a test of quantum dots’ discriminatory power, the authors used four varieties at once – white, red, green and blue – each detecting a different protein, to stain lymph node biopsies. The goal was to distinguish six Hodgkin’s lymphoma cases from two other types of lymphoma and samples from two patients with benign growths in their lymph nodes.

Reed-Sternberg cells can be distinguished by their red outline, blue and white internal staining, and their lack of green staining. Courtesy of Dr. Shuming Nie.

Reed-Sternberg cells have a distinctive appearance, but in lymph-node tissue, they usually are surrounded by other white blood cells. The authors describe identifying them as like “finding a needle in a haystack.”

“We’re excited about this technology,” said Dr. Andrew N. Young, associate professor of pathology and laboratory medicine at Emory and director of clinical laboratories at Grady Health System. “We expect it could help guide the type of treatment a cancer patient gets and that it could be used with a wider variety of tumor types.”

The most reliable way to assign cell identity is to look at more than one protein, Young said. With the standard methods in most pathology labs, staining cells with four different antibodies would require four separate slides – a problem when the specimen is very small. Small diagnostic specimens are common today because they minimize the burden on the patient. In addition, the images from multiple separate slides would not depict the same cells exactly. The quantum dots allow multiplexing, or superimposing, four colors on top of each other.

Hodgkin’s lymphoma usually is treated with chemotherapy and radiation and is notable among the subtypes of adult lymphoma because the survival rate is relatively high. Young said the quantum dot technique could be useful for other types of cancer, where distinguishing cancer cells based on surface or genetic markers can point oncologists toward “targeted therapies” designed for a particular type of tumor.