| Popis: |
One of the joys of preparing this paper was the necessity of rereviewing the elegant work of Leslie Foulds (1969), Harry Greene (1951), and Jacob Furth (1953), and of recalling many pleasant and stimulating discussions with each of them. Foulds studied solid tumors, primarily adenocarcinomas of the breast, and his definition of progression as the independent and irreversible gain or loss of unit characters with time leading to the autonomous state has served oncologists well. Similarly, Greene’s study of adenocarcinoma of the endometrium and breast which demonstrated increased malignancy with time are classics, and Furth’s demonstration of conditioned and dependent tumors and loss of dependency as a manifestation of progression has markedly influenced endocrine therapy of cancer. The mechanism of progression appears to involve the selection of cells best able to survive under the conditions. Thus, the irreversible gains and losses of attributes by a tumor with time are the result of extermination of subpopulations of cells with consequent loss of their phenotypic traits, leaving a tumor composed of more rapidly growing subpopulations expressing their particular traits. Thus, the phenotype and behavior of tumors change irreversibly with time. |
