Since it was first announced in 1982, the ECM theory has gained support from experimental results. This past spring, however, it was put to its most stern test. The malignant strain was treated in culture with an antibody that blocks one of the integrins-proteins which reside in the outer membrane of a cell and through which signals from the ECM are transmitted inside. This image shows a cluster of normal breast cells on the left, tumor cells in the center, and reverted tumor cells on the right. The reverted cells were treated with an integrin-blocking antibody.
Areas shown in red are cell nuclei, the green areas are cyto-skeletal protein.
These images were produced by Carolyn Larabell. Under the influence of the integrin-blocking antibody, the malignant cells reverted back to a normal appearance, their cancerous growth ceased, and they functioned as if they were healthy cells. Injected into mice, the same type of treated malignant cells yielded far fewer tumors that grew much more slowly than untreated cancer cells. By altering the pathways between the ECM and the nucleus, Bissell and Weaver were able to revert malignant cells back into almost normal form and function. When the reverted cells were examined with a fluorescent probe, the genes in their nuclei were still abnormal, indicating that the phenotype had been changed but not the genotype.