A cancer cell and a healthy cell share much of the same basic biology and biochemistry. The difference between them is that the expression or repression of the genes in a cancer cell is not properly regulated. As a result, the cancer cell exhibits uncontrolled growth and abnormal differentiation.
Berkeley Lab's Mina Bissell has argued that cancerous cells lose the ability to "sense" their microenvironment properly.
During the past decade, Bissell and her collaborators have conducted a series of studies in which they have manipulated the microenvironments of cells in cultures that mimic the physiological microenvironments in organs of the human body. The results have vital implications for breast cancer diagnosis and prognosis.
In one study, for example, malignant human breast cells were made to look and act as if they were normal, by regulating them from outside the cells (see sidebar); conversely, normal cells were made to look and act as if they were cancerous by changing their microenvironments.
"Our experiments have helped to explain why breast cancer takes so long to develop, even in women who are at high genetic risk," says Bissell. "So long as cellular and tissue structure are maintained, tumor development can be suppressed despite the presence of cancer-inducing genes. Even after cancer genes have been expressed and lesions have formed, it may still be possible to reverse the tumor process and restore cells to normal appearance and function." This is a hopeful view of cancer.