前沿科技及其它

The microcolony assay originally described by Withers and Elkind in 1970 (1) has been a useful method for investigating the effects of radiation and various other genotoxic and cytotoxic damaging agents on the intestinal epithelial stem cell population and to assess the ability of a variety ...

The recognition of cancer as a genetic disease has changed the approach investigators take to understanding the mechanisms of carcinogenesis. The discovery of oncogenes, and the recognition of the inactivation of tumor suppressor genes, DNA repair enzymes, and of apoptotic pathways h ...

While in situ techniques have been valuable in identifying the presence and localization of cytoplasmic and membrane components in tissue (1), there is often a need to study directly one or more cell types, free from its own microenvironment. For the human colon, isolation techniques to allow di ...

Somatic gene therapy is based on the principle of transferring recombinant genes efficiently into somatic tissues and achieving expression of the gene product in order to replace genetically defective gene functions or alter pathological disease processes. The development of a ge ...

Xenografting of human tumors has been used to produce samples which are enriched for neoplasia and optimal for subsequent molecular analyses. Molecular studies of xenograft tumors generated from both human colon and pancreatic adenocarcinomas have led to the discovery of important ...

Screening for chromosomal changes in solid tumors was long hindered by methodological problems encountered in standard cytogenetic analysis. Comparative genomic hybridization (CGH), a technique that emerged in 1992 (1) has proved to be a powerful tool for molecular cytogenetic an ...

An opportunity to look inside of the individual cell for the direct visualization in situ of “what happened?” is the most wonderful feature offered by fluorescence in situ hybridization (FISH). DNA in situ hybridization is a technique that allows the visualization of defined sequences of nuc ...

Loss of the long arm of chromosome 18 (18q) is one of the most common genetic changes in colorectal cancer. This chapter describes the method to determine chromosome 18q status using microsatellite markers. Specifically, tumor and normal tissue are separated by microdissection of routine f ...

Selective ultraviolet radiation fractionation (SURF) is a simple technique for the isolation of histologically defined microscopic tissue regions (1,2). Very small numbers (100-400) of cells can be rapidly isolated with relatively crude equipment. The isolated cells can be analy ...

Defective DNA mismatch repair (MMR) occurs in the majority of tumors from patients with hereditary non-polyposis colorectal cancer (HNPCC) and approx 15% of sporadic colorectal cancer (CRC) (1,2). In HNPCC-associated tumors, defective MMR is most often due to inactivating mutations of t ...

Microsatellites are tandem repeats of simple sequences that occur abundantly and are randomly interspersed throughout the human genome. They typically consist of 10-50 copies of 1-6 bp motifs, and are characterized by a high degree of polymorphism. Despite the variability observed am ...

Telomeres are very important structures that protect chromosomal ends from recombination, but the structure itself induces irreversible reduction without the presence of telomerase activity. Researchers are now collecting evidence of telomere dynamics in clinical sampl ...

Telomere length is now known to be directly responsible for limiting the capacity of cellular division in a number of human cell types (1,2). Comparison of telomere length in tumors and matched normal tissue from the same individual has indicated that the telomere repeat array is often shorter in t ...

The understanding that human neoplasms are clonal cell proliferations ultimately derived from a single transformed somatic cell represents a major advance in cancer biology. A cell population is designated as clonal if it can be demonstrated to have arisen from a single parent or progeni ...

Patients with acute leukemia have a total of approx 1012 leukemic cells at the time of diagnosis, and still have as many as 1010 leukemic cells in complete remission. The most important problem in the treatment of leukemia patients is the uncertainty of whether leukemic cells have been totally erad ...

The principle of cDNA microarray hybridization takes advantage of the property of DNA to form duplex structures between two complementary strands. In this technique (Fig. 1), the cDNA probes, which are arrayed onto a glass slide and represent the sequence of known genes or expressed sequence t ...

Understanding when and where the constellation of genes in a genome are expressed provides important information about the state of a tissue. Changes in gene expression are a driving force in cell differentiation, proliferation, and death. Abnormal gene expression as a direct consequen ...

It is estimated that the human genome contains 25,000–35,000 genes; however, only about 15% of these are expressed in any given cell and different cells and tissues express different gene subsets. Gene expression is tightly regulated under normal physiologic conditions but is often disrup ...

There are a variety of methods for the detection and definition of mutations in disease states including cancer. For the detection of unknown mutations, several screening techniques are available including single-strand connformation polymorphism (ssCP) (1), protein truncati ...

Nonisotopic RNase cleavage assay (NIRCA) is an RNase-cleavage-based method for mutation scanning that detects mutations as double-stranded cleavage products in duplex RNA targets. A central requirement for NIRCA is the ability to produce large amounts of double-stranded target R ...