Patent ID: 7323300

Claim:
A method for detecting a gene expression profile of living neoplastic cells that are resistant to a cytotoxic compound and distinguishing said profile from the gene expression profile of living neoplastic cells that are sensitive to the cytotoxic compound in a mixed population of cells from a tumor sample, the method comprising the steps of: a) contacting the mixed population of cells with the cytotoxic compound for a time and at a concentration wherein the neoplastic cells that are sensitive to the cytotoxic compound undergo apoptosis; b) contacting the mixed population of step (a) with a vital stain or fluorescent dye; c) contacting the mixed population of cells of step (b) with a discrimination compound that binds to phosphatidylserine; d) contacting the mixed cell population of step (c) with a detectably-labeled immunological reagent that specifically binds to the phosphatidylserine discrimination compound; and e) separating the cells in the mixed population of step (d) that are not stained with the vital stain from the cells that are stained with the vital stain; f) separating and isolating the cells in the mixed population of step (e) that are not stained with the vital stain and that do not bind the immunological reagent from the cells in the mixed population of step (e) that are not stained with the vital stain and that do bind the immunological reagent; g) isolating cellular RNA from the each of the separated cells selected in step (f); h) preparing detectably-labeled cDNA from the cellular RNA isolated in step (g); i) hybridizing each of the cDNA preparations prepared in step (h) to a gene array comprising at least 4000 eukaryotic genes; j) detecting a pattern of gene expression for hybridization of each of the cDNA preparations prepared from the mRNA isolated from the cells selected in step (f); and k) comparing the pattern of gene expression detected in step (j) from hybridization of the microarray with cDNA from cells that are not stained with the vital stain and that do not bind the immunological reagent with a pattern of gene expression obtained by hybridizing cDNA prepared from cells that are not stained with the vital stain and that do bind the immunological reagent.