The present invention provides methods and compositions for isolating and detecting rare cells from a biological sample containing other types of cells. In particular, the present invention includes a debulking step that uses a microfabricated filters for filtering fluid samples and the enriched rare cells can be used in a downstream process such as identifies, characterizes or even grown in culture or used in other ways. The invention also include a method of determining the aggressiveness of the tumor or of the number or proportion of
cancer cells in the enriched sample by detecting the presence or amount of
telomerase activity or
telomerase nucleic acid or
telomerase expression after enrichment of rare cells. This invention further provides an efficient and rapid method to specifically remove red blood cells as well as white blood cells from a biological sample containing at least one of each of red blood cells and white blood cells, resulting in the enrichment of rare target cells including circulating
tumor cells (CTC), stromal cells, mesenchymal cells, endothelial cells, fetal cells, stem cells, non-hematopoietic cells etc from a blood sample. The method is based upon combination of immuno-microparticles (
antibody coated microparticles) and density-based separation. The final enriched target cells can be subjected to a variety of analysis and manipulations, such as flowcytometry, PCR,
immunofluorescence,
immunocytochemistry,
image analysis, enzymatic assays,
gene expression profiling analysis,
efficacy tests of therapeutics, culturing of enriched rare cells, and therapeutic use of enriched rare cells. In addition, depleted
plasma protein and white blood cells can be optionally recovered, and subjected to other analysis such as
inflammation studies,
gene expression profiling, etc.