Looking for solid anticancer evidence.

Looking for solid anticancer evidence

Cell suspensions living in the laboratory have given scientists much of what they know about cancer -- how it grows and how it might be stopped. But basic differences exist between more diffuse malignacies, such as leukemia, and the so-called solid tumors, which are characterized by more tightly defined margins, discrete internal environments and an unfortunate propensity for becoming resistant to drugs. In the past, the search for anticancer drugs has been based on leukemia-like systems, says Thomas H. Corbett of Wayne State University in Detroit. Now he and others are creating in vitro systems they say will give better information on pathogenesis and treatment of the solid tumors like colorectal cancer.

One of those systems Corbett and his colleagues call a multiple-tumor-soft-agar-disk-diffusion assay. Cancer cells from solid tumors, when placed in soft agar, grow in tight colonies. By placing a drug-saturated paper disk on top of cancer cells in the agar, the scientists can look for colony-growth inhibition -- a method similar to commonly used antibiotic screening tests. Roughly 85 percent of the drugs screened thus far have shown no activity against solid tumors, Corbett says, adding that fewer than 1 percent go on to animal testing. He says the ability to screen 5,000 to 6,000 new drugs a year, at a cost far cheaper than other methods, will speed drug development.