Chalones: from aqueous extracts to oligopeptides.

The term "chalone" was coined about 40 years ago to describe endogenous growth-inhibiting factors with a tissue-specific and reversible effect. A large number of "chalones" were reported in the 1970's and early 80's. The term was, however, used rather indiscriminately and attempts at purification of the active component(s) were without success. As a result, most laboratories lost interest. Then, in the early 1980's, two different research teams demonstrated that the active growth-inhibiting constituents were N-substituted oligopeptides. In the following years, similar oligopeptides were characterized in extracts of liver, the large bowel, melanocytes, lymphocytes, and neuroblastoma, in addition to the two first ones from monomyelopoietic cells and epidermis, respectively. All peptides have a bell-shaped dose response pattern and optimal effect at very low concentrations. Several of them inhibit growth even in tumors derived from the respective organs. Preliminary studies have revealed that two of the oligopeptides alter the expression of growth- and differentiation-related genes. Quite recently, some papers are again using the term "chalone" and a short review therefore seems appropriate.