Lung Cancer Gene Discovery A Sign of Cancer's Future
Science is tackling gene-caused flaws, cancer stem cells, and earlier detection of tumors
New Avenues of Exploration
While most doctors now talk in terms of managing cancer rather than curing it outright, there is one avenue of research—cancer stem cells—that might offer a permanent solution. Just as healthy adult stem cells in the body's organs produce cells for renewal and repair, the thinking goes, a small fraction of the cells in a single tumor manufacture tumor cells like little factories. Chemotherapy and radiation may seem to make a person cancer free when they actually leave the factories untouched to crank up production again later. Researchers have reported finding stem cells in leukemias and myelomas, as well as in breast, brain, pancreatic, and other tumors. Whether the cells are true stem cells or simply cells that have mutated to possess the stem-cell-like power of self-renewal is up for debate; either way, those properties are likely controlled by unique pathways that might be singled out and targeted.
It won't be easy to find and take aim at stem cells, since they're apt to look different from patient to patient, says Craig Jordan, a molecular biologist at the University of Rochester Medical Center whose lab is one of several working to develop new cancer stem cell treatments. But some drugs may already be blasting these cells. Gleevec may work so well because it eliminates leukemia stem cells, for example. And the breast cancer drug Tykerb appears to cut the number of breast cancer stem cells.
As well as explaining how a tumor recurs, some experts theorize that stem cells may offer clues to a cancer cell's deadliest function: metastasis. Perhaps the stem cells themselves stealthily leave the site of the original tumor and lodge elsewhere, sometimes hiding for years before beginning to grow again. Or perhaps they are capable of producing those highly mobile cells.
Understanding how cancer operates in the body requires looking beyond the cancer cell itself, at the tiny neighborhood of normal cells that surround it. Cancer that wants to grow and thrive has to recruit nearby cells to its cause, just as someone might borrow a cup of sugar from a neighbor. For example, the cascade of chemicals involved in the body's inflammatory response may help the cell invade healthy tissue, says David Cheresh, vice chair of pathology at Moores Cancer Center at the University of California-San Diego. And the various healthy surrounding tissues and cells play their part, too. One class of drugs, including Avastin for advanced colon, lung, and breast cancer, already buys some patients extra time by targeting one part of the tumor's outreach to its neighborhood: its recruitment of blood vessels to fuel its growth.
A friendly microenvironment is also key to metastasis. Ties between a cancer cell and its neighbors are already strong by the time a primary tumor grows, says Lynn Matrisian, chair of cancer biology at Vanderbilt University. But when a cancer cell travels to a distant organ, "in my mind, there's an opportunity to intervene" before neighborly relationships are cemented, says Matrisian. Indeed, drugs used to prevent osteoporosis can also make the bone less hospitable to metastatic cells from breast, prostate, and other cancers.
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