In human cancer, early systemic spread of tumor cells is recognized as a leading cause of death. Adjuvant therapies are administered to patients after complete resectioning of their primary tumors to eradicate the few residual and latent metastatic cells. These therapeutic regimens, however, are currently designed without direct information about the presence or nature of the latent cells. To address this problem, we developed a PCR-based technique to analyze the transcriptome of individual tumor cells isolated from the bone marrow of cancer patients. From the same cells, genomic aberrations were identified by comparative genomic hybridization. The utility of this approach for understanding the biology of occult disseminated cells and for the identification of new therapeutic targets is demonstrated here by the detection of frequent extracellular matrix metalloproteinase inducer (EMMPRIN; CD147) expression which was verified by immunostaining.

Allogeneic stem cell transplantation (SCT) can induce curative graft-versus-tumor reactions in patients with hematological malignancies and solid tumors. The graft-versus-tumor reaction after human histocompatibility leukocyte antigen (HLA)-identical SCT is mediated by alloimmune donor T cells specific for polymorphic minor histocompatibility antigens (mHags). Among these, the mHag HA-1 was found to be restricted to the hematopoietic system. Here, we report on the HA-1 ribonucleic acid expression by microdissected carcinoma tissues and by single disseminated tumor cells isolated from patients with various epithelial tumors. The HA-1 peptide is molecularly defined, as it forms an immunogenic peptide ligand with HLA-A2 on the cell membrane of carcinoma cell lines. HA-1–specific cytotoxic T cells lyse epithelial tumor cell lines in vitro, whereas normal epithelial cells are not recognized. Thus, HA-1–specific immunotherapy combined with HLA-identical allogeneic SCT may now be feasible for patients with HA-1+ carcinomas.

The need to analyze rare cells is based on the nature of tissue differentiation and regeneration, the initiation and propagation of disease processes in multicellular organisms, and the functional diversity of individual cells. Gene transcription is the most important regulatory mechanism by which a phenotype and functional state of a cell is determined. Therefore, procedures for the qualitative and quantitative assessment of mRNA abundance are important. This unit presents a protocol for semi-quantitative analysis of gene expression of a single cell and quantitative representation of expressed genes from >10 to 30 cells. A basic protocol for array hybridization on nylon filters is provided because such filters are available in every laboratory. Tissue samples contain many different cell types in variable amounts, so their analysis may require microdissection; a protocol for obtaining cryosections is given. Finally, a simple procedure to prepare the data for statistical analysis is also provided.

The need to analyze rare cells is based on the nature of tissue differentiation and regeneration, the initiation and propagation of disease processes in multicellular organisms, and the functional diversity of individual cells. Gene transcription is the most important regulatory mechanism by which a phenotype and functional state of a cell is determined. Therefore, procedures for the qualitative and quantitative assessment of mRNA abundance are important. This unit presents a protocol for semi-quantitative analysis of gene expression of a single cell and quantitative representation of expressed genes from >10 to 30 cells. A basic protocol for array hybridization on nylon filters is provided because such filters are available in every laboratory. Tissue samples contain many different cell types in variable amounts, so their analysis may require microdissection; a protocol for obtaining cryosections is given. Finally, a simple procedure to prepare the data for statistical analysis is also provided.

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