Properties of the accelerant factor (s) for a transplantable mouse mammary tumor, Z8352.

freshly excised mouse mammary carcinoma Z835@ has been shown to enhance the malignant process associated with the transplantation of this tumor in susceptible mice (@5). This enhancement was manifested by a significant acceleration in the time to death (or a significant decrease in longev ity) in pretreated mice when compared to control animals which did not receive the accelerant ma terial. The active material, termed â€oefresh acceler ant,†• is apparently in the category described by Casey and associates (@,3, 9) as â€oeXYZfactors.†• It is the purpose of this paper to present the re suits of studies in which physical, chemical, and serological technics were employed to characterize the active tumor enhancive factor(s) present in the Z83@5@ tumor. The accompanying paper (@6) iscon cerned with the mechanism of the enhancement in tumor development that is provoked by the ac celerant factor(s). MATERIALS AND METHODS Tumor.†" The â€oefreshaccelerant†• tumor-enhancive ma terial employed for the preparatory inoculation and the tumor tissue for the challenge injection were derived from the mouse mammary adenocarcinoma Z8352. This tumor is of C3H origin (Bittner Z stock) and at the time this report was written it had been maintained for 45 successive passages by trans plantation in susceptible ZBC mice. Hosts.†" Hybrid back-cross ZBC mice (Bittner), from 6 to 8 weeks of age, were used as test animals. The transplantation of Z8352 cancer cells in these animals produced uniformly lethal results. following multiple centrifugation at 1,200 r.p.m. of a saline extract of freshly excised, homogenized Z8852 tumor tissue. The method of preparation has previously been described (25). Method of demonstrating acceleration.†" Enhancement of the malignant process was demonstrated by the employment of the followingexperimental procedure: (a) Test mice received by subcutaneous injection in the groin 0.2 ml. of accelerant material. (5) Test mice as well as control animals that bad not received a preparatory injection of accelerant material were challenged 9-81 days later with viable Z8852 cancer cells. The challenge inoculum, consisting of 0.1 ml. of tumor cells in S per cent suspension with 0.85 NaCI as diluent, was administered subcutaneously into the tissues of the nape of the neck. (c) Test and control recipient animals following challenge were observed daily until death to follow the de velopmentof the implantedtumor.As a meansof expressing quantitatively any enhancement in the malignant process the â€oepercental accelerant index†• method (25) was employed. In this formula: …