The advantages of the new methodology, called multiplexed ion beam imaging (MIBI), is described by a team of scientists at UC Davis and San Francisco and at Stanford, Genentec in the March 23 advance online publication of the journal Nature Medicine.
“This technology enables researchers to identify the molecular makeup of breast tumor cells more quickly and in greater detail than has been possible before,” said Richard Levenson, study co-author and professor and vice chair for strategic technologies in the UC Davis Department of Pathology and Laboratory Medicine. “It’s a powerful tool that allows us to look at many more than one biomarker at a time, which has important implications for research and clinical diagnosis.”
Conventional immunohistochemistry (IHC), the standard method for detecting these molecules, typically can simultaneously pinpoint only two to four markers, Levenson said. And while other existing technologies could be used to assemble a detailed map of many protein markers, called antigens, of breast tumor cells, he said that these techniques are time-consuming and can involve many steps. In contrast, future iterations of MIBI could quickly provide up to 100 antigens “all in one shot.”
Researchers and clinicians need the greater detail that MIBI can provide because identifying protein markers that make up each cell in a breast tumor is complex. Tumors contain a variety of cells, from cancerous cells that differ in gene expression, or activity, to immune system cells and non-malignant stromal cells that form the structural framework of the tumor.
Until recently, a tumor’s stromal cells were thought to be inconsequential in the development and growth of a malignant tumor. But recent research has found that biological cross-talk occurs between malignant and stromal cells, Levenson said.
“The stromal cells are clearly influencing the cancerous cells and vice versa,” he said. “Understanding the nature of the cross-talk as well as the protein markers associated with a tumor’s growth and spread to other sites in the body potentially could lead to more effective treatments against the disease.”
For the study, Stanford University researchers developed MIBI, and Levenson and UC Davis anatomic pathologist Alexander D. Borowsky provided the expertise in breast tumor pathology and the clinically relevant antibodies from breast cancer patient biopsies that enabled Stanford researchers to evaluate MIBI’s effectiveness. Like other clinical samples, the tissue sections were formalin-fixed and embedded in paraffin.
MIBI uses a technique known as secondary ion mass spectrometry to image the locations of antibodies that have been labeled with isotopically pure elemental metals. Because each of these metal-tagged antibodies binds to a specific protein, or antigen, in a section of tissue, they serve as reporters of the identity and location of the proteins there. The signals produced by the metal tags on the antibodies also enable the mass spectrometer to produce images that reveal the spatial features of protein expression in individual cells.
Co-authors of the technical report, entitled “Multiplexed Ion Beam Imaging of Human Breast Tumors,” include Michael Angelo, Stanford University and UC San Francisco; Sean C. Bendall, Rachel Finck, Matthew B. Hale, Chuck Hitzman, Scot D. Liu, Shuchun Zhao, Yasodha Natkunam and Garry P. Nolan, Stanford University; Alexander D. Borowsky and Richard M Levenson, UC Davis; John B. Lowe, Genentech.