Interfering RNA Technology Used for Chemotherapy Sensitivity Screening

Cancer researchers have combined a high-throughput cell-based one-well/one-gene screening platform with a genome-wide synthetic library of chemically synthesized small interfering RNAs to identify genes related to the sensitivity of cancer cells to the chemotherapeutic drug paclitaxel.
Paclitaxel disrupts microtubule function, inhibiting cell replication. One of the roles of normal microtubules is to aid in the replication of cells, and paclitaxel promotes the formation of microtubules that do not function properly, thus disrupting this function and inhibiting cell replication. The drug is used in patients who have ovarian cancer carcinoma alone, and in combination with such platinum-containing drugs as cisplatin or carboplatin. Paclitaxel is also used to treat breast cancer that has recurred or progressed following treatment with other drugs. It is also used to treat non-small cell lung carcinoma in combination with cisplatin in cases where surgery or radiation is not possible. Paclitaxel is also used to treat AIDS-related Kaposi's sarcoma.
Investigators at the University of Texas Southwestern Medical Center (Dallas, USA) used isolated NCI-H1155 human non-small-cell lung cancer cells in a high-throughput 96-well array along with four siRNAs targeting a single gene in each well. Paclitaxel was added to each well for two days, and by examining the survival of the cells in each well, the investigators determined which genes were involved in affecting the cells'sensitivity to the drug.
Results published in the April 12, 2007, edition of Nature revealed that a panel of 87 genes represented major focal points of the autonomous response of cancer cells to paclitaxel's abrogation of microtubule dynamics. Several of these genes sensitized lung cancer cells to paclitaxel concentrations 1,000-fold lower than otherwise required for a significant response.
"Being able to do this in human cells, and being able to do it fast – this is very powerful,” said senior author Dr. Michael White, professor of cell biology at the University of Texas Southwestern Medical Center. "The idea of the screen was to be able to take advantage of the new generation of technology to silence any gene we want. That is the power of a genome-wide screen - you go in without any expectations and let the data tell you what is important. Chemotherapy is a very blunt instrument, it makes people sick, and its effects are very inconsistent. Identifying genes that make chemotherapy drugs more potent at lower doses is a first step toward alleviating these effects in patients.”


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University of Texas Southwestern Medical Center