Abstract: The present invention provides a novel method which makes it possible to obtain, from a piece of tissue, a sample enriched with cells or cell nuclei of interest. A piece of tissue is subjected to pretreatment comprising water flow disruption and/or ultrasonic disruption to obtain a population of particles including individually separated cells or cell nuclei. A population of particles significantly abundant in cells or cell nuclei of interest is sorted or fractionated on the basis of optical properties of the cell nuclei in the separated cells or of the separated cell nuclei or on the basis of physical properties of the cell nuclei in the separated cells or of the separated cell nuclei.

Abstract: Provided are a pretreatment method for detecting the number of cells containing Ki-67 protein-positive nuclei using Ki-67 antibody; a method for the detection; a kit to be used in the detection method; and determination of a therapy regimen using the aforesaid method. Attempts were made to activate Ki-67 antigen with the use of an enzyme having been considered as inappropriate for the activation thereof. By pretreating a sample with an enzyme not recognizing the epitope of MIB-1 (a rare cutter enzyme), the antigen activation of Ki-67 antigen was enhanced, while enhancing the antigenicity of other antigens including a cytokeratin too. As a result, a method for more objectively and more universally quantifying Ki-67-positive cells at higher reproducibility, said method comprising isolating cell nuclei from an FFPE section while enhancing the antigenicity and performing a reaction between Ki-67 protein, i.e., the target, existing in the cell nuclei with a fluorescently labeled antibody, has been completed.