Retardation of growth of a transplantable carcinoma in mice fed basic metachromatic dyes.

Some years ago an experiment was briefly reported (25) in which it was found that a single subcutaneous injection of 0.1 cc. of heparin (Vitrum, Stockholm) into mice at the expected time of emergence of 1, 2, 5, 6dibenzanthracene-induced papillomas not infrequently led to the localization of a tumor in a small elliptical wound placed over the wheal raised by the injection in the painted area. Of 47 mice surviving this treatment, 8 carcinomas appeared in the scars; while in a further 11 animals the wounds in course of healing showed hyperkeratosis or small papillomas which subsequently regressed. No tumors arose from the scars of a comparable group of mice in which chick embryo extract replaced the heparin. Heparin (34) and embryo extract (4) were chosen for these experiments on account of their reported effects in causing, respectively, inhibition and stimulation of the growth of normal cells in tissue culture. The mechanism whereby heparin exerts an inhibitory effect on cells in tissue culture is still obscure, though recent work by Fischer (10) suggests that heparin or similar colloidal compounds carrying a strong electronegative charge may become bound to the basic groups that arise at cell surfaces as a result of injury. In the experiment previously reported (25) an additional effect in vivo of the injection of a strong solution of heparin was seen in the local and temporary resorption of dermal collagen which occurred at the site of injection. As a result, the elasticity of the surrounding skin pulled apart the edges of a wound in such an area and converted the original narrow ellipse into an oval or circular shape. It was thought that the greater mitotic activity necessary to close such wounds might in part account for the localization of tumors to the scars. A later experiment afforded some support for this view (25). Whether heparin plays any part in tumor formation or growth under normal circumstances is at present unknown. As regards its origin--and largely on the basis of the metachromatic staining reaction--it has been suggested that heparin is discharged into the blood stream from the granules of the histogenous mast cells which line the capillaries of the loose connective tissues (33). In addition to the hematological function of these cells, Sylv6n (29, 30) believes that in both normal and malignant growth the histogenous mast cells fulfil a second role in which they migrate away from the capillaries and discharge their granule content into the tissues where it may be detected as metachromatically-staining "free chromotrope substance" (15, 16). If, as Sylv6n (30) believes, such "free chromotrope substance" is important in facilitating the invasivenes of tumor cells, many of the observations on the aggregation of mast cells around tumors (2, 11, 13, 21, 28, 32) and in skin which has been subjected to the action of tar (1, 3,7-9, 19, 23, 24, 31), arsenic, X-rays (1) and the carcinogenic hydrocarbons (4, 24) take on a new significance. It was thus of interest to determine the effect on tumor growth of substances calculated to bind heparin or similar high molecular polysulphuric acid esters in the hope that results of possible therapeutic significance might emerge.