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Senior Member
Join Date: Aug 2006
Location: Pennsylvania
Posts: 1,080
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San Antonio Breast Cancer Symposium (SABCS)
As Dr. Robert Nagourney, medical and laboratory director at Rational Therapeutics, and instructor of Pharmacology at the University of California, Irvine School of Medicine describes it, recent press coverage from the San Antonio Breast Cancer Symposium (SABCS) touched upon the development of multi-gene predictors for clinical response in breast cancer.
One report from that meeting described correlations between a laboratory assay model in use at the University of Pittsburgh and microarray analyses. However, the suggestion that this laboratory technique - described by its proponents as a chemosensitivity assay - could accurately identify gene profiles that would predict response seems at odds with the current literature.
Although the press coverage concluded that this technique showed “promising performance” it was largely exploratory and defined by the authors as a “validation study.”
What is interesting is that a team of highly reputable investigators from M.D. Anderson recently reported a very negative study using a similar approach of identifying target genes in cell lines and then correlating them with patient outcomes.
In the paper, published in the June 2010 issue of Breast Cancer Research and Treatment (Liedtke, C. et al. Breast Cancer Res Treat. 2010 Jun; 121(2):301-9) the authors reported “cell line derived predictors of response to four commonly used chemotherapy drugs did not predict response accurately in patients.”
Indeed, differential gene expression seemed only to correlate with paclitaxel. The authors found that false discovery rates were high for all other drugs tested. Thus, the report from the SABCS will need to be carefully examined to determine whether truly relevant clinically predictive information can be provided by this particular laboratory platform.
Modern cancer research can be divided into three principal disciplines based upon methodology:
1. Genomic - the analysis of DNA sequences, single nucleotide polymorphisms (SNPs), amplifications and mutations to develop prognostic and, to a limited degree, predictive information on cancer patient outcome.
2. Proteomic - the study of proteins, largely at the level of phosphoprotein expressions.
3. Functional - the study of human tumor explants isolated from patients to examine the effects of growth factor withdrawal, signal transduction inhibition and cytotoxic insult on cancer cell viability.
Contrary to analyte-based genomic and proteomic methodologies that yield static measures of gene or protein expression, functional profiling provides a window on the complexity of cellular biology in real-time, gauging tumor cell response to chemotherapies in a laboratory platform.
By examining drug induced cell death, functional analyses measure the cumulative result of all of a cell's mechanisms of resistance and response acting in concert. Thus, functional profiling most closely approximates the cancer phenotype.
Insights gained can determine which drugs, signal transduction inhibitors, or growth factor inhibitors induce programmed cell death in individual patients' tumors. Functional profiling is the most clinically validated technique available today to predict patient response to drugs and targeted agents.
Epigentics may have important implications for the treatment of cancer. The cell-based functional profiling platform has the capacity to measure genetic and epigenetic events as a functional, real-time adjunct to static genomic and proteomic platforms.
By examining small clusters of cancer cells (microspheroids or microclusters) in their native state, it can provide a snapshot of the response of tumor cells to drugs, combinations and targeted therapies.
The proteomic platform does not clarify how the response to targeted drugs compares with that to chemotherapy, combinations, or other targeted therapies. There is a challenge to identify which patients the targeted treatment will be effective.
The analysis is unique in that each microspheroid examined contains all the complex elements of tumor biosystems found in the human body and have a major impact on clinical response. Cell function analysis is a conduit that connects novel drugs to clinicians and patients in need.
There are any number of variables that affect drugs, including the rate of excretion of the drugs by the kidneys and liver, protein binding and a myriad of other biological factors. In the body, these cells interact with and are supported by other living cells, both malignant and non-malignant cells. That is why cell-death functional profiling assays study cancer cells in microspheroids or microclusters.
Three-dimensional (3D) tissue culture methods have an invaluable role in tumor biology and provides very important insights into cancer biology. As well as increasing our understanding of homeostasis, cellular differentiation and tissue organization, they provide a well defined environment for cancer research in contrast to the complex host environment of an in vivo model.
Due to their enormous potential, 3D tumor cultures are currently being exploited by many branches of biomedical science with therapeutically orientated studies becoming the major focus of research. Recent advances in 3D culture and tissue engineering techniques have enabled the development of more complex heterologous 3D tumor models.
Clinical application of functional profiling in advanced NSCLC and colorectal cancers ASCO Meeting Abstracts 26: 13547 R. A. Nagourney, J. Blitzer, D. McConnell, R. Shuman, S. Grant, K. Azaren, I. Shbeeb, T. Ascuito, B. Sommers, and M. Paulsen
Functional profiling in stage IV colorectal cancer: A phase II trial of individualized therapy ASCO Meeting Abstracts 27: e15124. J. B. Blitzer, I. Shbeeb, A. Neoman, K. Azaren, M. Paulsen, S. Evans, and R. Nagourney
Functional profiling in stage IV NSCLC: A phase II trial of individualized therapy ASCO Meeting Abstracts 27: e19079. R. A. Nagourney, J. Blitzer, E. Deo, R. Nandan, R. Schuman, T. Asciuto, D. Mc Connell, M. Paulsen, and S. Evans
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