Study finds new way to detect cancer indicators

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Researchers at Purdue University have developed a new way to detect protein movements inside cells, which signal a variety of cellular changes such as those in cancer cell development. The method could help diagnose cancer, according to a study published this month in Analytical Chemistry.

The technique combines two distinct methods to examine large numbers of cells individually, a “feat not previously possible,” said Chang Lu, a Purdue University assistant professor of agricultural and biological engineering.

Lu's method uses two existing technologies: electroporation, used to determine protein location, and flow cytometry, a technique capable of rapidly examining individual cells but blind to intracellular protein locations on its own.

The Purdue technique, electroporative flow cytometry, harnesses the discerning power of the first method with the speed of the second, Geahlen said. 

In the study, Lu demonstrated that the technique can detect a handful of protein movements, or translocations, within entire populations of cells. These movements are important to detect because they are involved in many disease processes, such as oncogenesis, wherein a normal cell becomes malignant, said Robert Geahlen, a study co-author and researcher in the department of medicinal chemistry and molecular pharmacology.

The method involves cells being sent through tiny channels within a microchip and undergoing electroporation, wherein electrical pulses open pores in cell membranes and protein is released from inside. Then, sensors measure protein concentrations. Since a protein's subcellular location can directly influence the amount of protein leaving the cell, this technique is capable of indirectly determining location, Geahlen said.

If proteins are in their original position, floating freely in the cell's interior, or cytoplasm, a large percentage of them will flow out of the cell upon electroporation, Lu said. If translocation has occurred, in which proteins migrate from the cytoplasm to tightly bind to the interior of the cell membrane, few will be able to leave.

According to Lu, previous technologies detect either protein movement in a few individual cells via slow imaging techniques or take average measurements from larger groups of cells, data usually irrelevant to protein location in individual cells.

The study also examined the movement of a certain type of protein called kinases, whose translocations are important for activating and deactivating cells and sending signals to one another, Geahlen said.

The technology has the potential to be scaled up significantly, Lu said. In the study, 100-200 cells were processed per second, but he said that rate could potentially increase to speeds typical of flow cytometry, which goes through 10,000 cells per second. Speed increases can be achieved by optimizing the technology, he added.

According to Lu, “due to the frequent involvement of kinase translocations in disease processes such as oncogenesis, our approach will have utility for kinase-related drug discovery and tumor diagnosis and staging.”