Terri Pollastro was diagnosed with advanced breast cancer three years ago, at age 43. The mother of two young daughters, she thought the fact that her cancer had already spread meant her remaining time with her children might be short.

Today, Pollastro’s cancer’s in remission and her tumor markers are low. She attributes this unexpected turn of events to the drug Herceptin.

This agent, manufactured by Genentech, is a new type of cancer drug. Instead of making a brute force attack on any growing cell — which happens in conventional chemotherapy, and is why hair loss often results — Herceptin blocks specific molecules, called receptors, on the cell surface. These receptors, thanks to abnormally overactive genes, are greatly over-expressed in some breast cancers. This new-style agent, though, inactivates most of those receptors, so the cells no longer get the insistent message to keep on growing.

Initially given to a subgroup of patients with advanced breast cancer, the drug is being studied for use in others. But aside from having proven its value in cancer, the new agent is also an argument for a basic research approach.

More than two decades ago, Robert Weinberg, MIT biology professor and founding member of the MIT Center for Cancer Research, discovered the key gene that becomes dysfunctional in cancers like Pollastro’s. Researchers at another university picked up on the work, connecting that gene and its protein product specifically to certain breast cancers. Genentech then took over, and the drug appeared on the market in 1998.

MIT cancer center director Tyler Jacks says Herceptin shows that the model of “basic research leading to a discovery, and people here, there, and everywhere picking up on the discovery and eventually creating a drug does work.” He cautions, though, that we still have a long way to go in exploring the biology that makes some molecularly targeted drugs effective and others not.

The workings of cells, including tumor cells, aren’t “linear processes,” he notes. “Cells are highly integrated networks, and we need to better understand how they function.”