Arnold E. Reif

Acid phosphatase isozymes in cancer of the prostate

Acid phosphatase (AP‐ase) isozymes were studied in prostatic carcinoma, to determine to what extent they remain active and unchanged. In contrast to serum AP‐ase, that of tissue homogenates was relatively stable. Tartrate‐sensitive AP‐ase activity varied 100‐fold for lesions taken from 11 different patients, without complete loss of activity in any lesion. The results explain why the serum AP‐ase activity is not invariably elevated even in patients with metastatic cancer of the prostate. An equation is given that permits estimation of the conditions under which secretion by the tumor will result in a detectable rise in the serum level of this enzyme. There was a close parallel between AP‐ase activity determined by test‐tube assay with phenyl phosphate as substrate, and activity determined by disc electrophoresis and development of isozyme bands with naphthol AS‐BI phosphate. Disc electrophoresis of prostate from normal adults and from patients with benign prostatic hypertrophy showed a fine structure of multiple isozyme bands, which was largely acquired during fetal development. Samples of primary and metastatic cancer of the prostate showed variable loss of normal prostatic isozyme bands, but some of these changes may have been artifactual. An AP‐ase isozyme band shared between fetal prostate and prostatic carcinoma, but absent from normal prostate, was not found.

Effect of Cigarette Smoking on Susceptibility to Lung Cancer

Fisher first suggested that genetic predisposition to lung cancer is a more important factor than cigarette smoking, and that therefore one may smoke. Recently, this thesis has been defended strongly by Burch. Here, a literature survey has been done that indicates that the genetic susceptibility for development of lung cancer varies between individuals. But it is wrong to conclude from this that therefore one may smoke. Such a conclusion only would be valid, if there was a close relationship between the genetic tendency to smoke cigarettes, and the genetic tendency to develop lung cancer. The evidence that such a relationship does not exist is overwhelming. It is, therefore, valid to conclude that the large excess of deaths from lung cancer in cigarette smokers as compared to nonsmokers is a direct consequence of smoking cigarettes. To illustrate the effect of cigarette smoking on susceptibility to lung cancer, the distribution of susceptibilities to lung cancer in cigarette smokers and in nonsmokers has been derived. The shape of the susceptibility distribution is determined by the effects of all environmental carcinogens (both known and unknown) to which the population has been exposed, as well as by differences in genetic susceptibility between members of the population. The method described has general application.

An explanation for the proportion of carcinomas and sarcomas seen in chemically induced murine submaxillary gland tumors.

Pellets of 1 mg 9,10‐dimethyl‐1,2‐benzanthracene (DMBA) were implanted into the submaxillary glands of 53 male C57BL/6J mice, and groups of mice were autopsied weekly or biweekly thereafter. Histologic evidence of tumor was noticed first at 12 weeks. From 16 weeks onwards, the submaxillary glands of all mice autopsied contained either carcinoma (three animals) or sarcoma (ten animals); 8/9 attempts to transplant these tumors in C57BL/6J mice were successful. Of the resulting eight tumor lines, two carcinomas and two fibrosarcomas were transplanted for over 30 months. Within the first few transplant generations, all four tumors showed an increase in growth rate and in histologic evidence of anaplasticity. For the particular tumors selected for study, the two carcinomas differed from the two sarcomas by growing more slowly, requiring more cells for tumor takes, and possessing a higher immunogenicity. These results may explain the types of tumors generated in submaxillary gland carcinogenesis. Carcinomas appear first, since they develop from the epithelial cells into which the carcinogen is implanted. Later, when fibroblasts wall off the carcinogen, fibroblasts are at risk for neoplastic conversion. Because of the more aggressive nature of the resultant fibrosarcoma cells, sarcomas may overgrow some early carcinomas.

PREPARATION AND THERAPEUTIC POTENTIAL OF RABBIT ANTISERA WITH “DIRECTED” SPECIFICITIES FOR MOUSE LEUKEMIAS*

Several immunization regimens for preparation of ALK-NABS were compared. One series of eight intravenous injections spaced over 5 weeks gave an ALK-NABS with potency and specificity that could be bettered only slightly by a second series of four injections spaced over 2 weeks, whereas a third series of injections was deleterious. Use of late immune antisplenocyte NABS for such immunizations produced ALK-NABS reagents with the highest in vitro specificity to leukemia cells relative to splenocytes after absorption, whereas early immune antisplenocyte NABS gave ALK-NABS with the highest antileukemia specificity relative to thymocytes. Therapy experiments with leukemias L1210 and BW-A showed increased survival times for isogeneic mice injected intraperitoneally with 10(3) (L1210 only), 10(4), and 10(5) (higher significance for L1210) cells, when ALK-NABS was given intraperitoneally in high dose on 4 or 5 successive days starting 1 day after inoculation of leukemia cells. In additional experiments with 10(5) cells given intraperitoneally, lower doses of ALK-NABS were progressively more effective with L1210 leukemia, producing some survivors without any apparent toxicity from the antiserum. In contrast, a similar experiment with leukemia BW-A was entirely negative. Addition of guinea pig serum to already excessive amounts of antiserum was not helpful.

Relationship of macrophage content, immunogenicity, and metastatic potential of a murine osteosarcoma of recent origin

The purpose of these studies was to determine whether the high macrophage content (>50 per cent) of the90Sr-induced osteogenic sarcoma J (Os-J) of recent origin correlated with its immunogenicity or low metastatic potential. Cloning experiments demonstrated that the Os-J tumor is heterogeneous with regard to the production of experimental pulmonary metastases. Immunization-challenge studies in syngeneic mice and comparisons of tumor growth in normal or nude mice established that the slow growing Os-J tumor is poorly immunogenic.In vitro studies demonstrated that the Os-J tumor is highly susceptible to macrophages-mediated lysis. This may explain the slow growth of the tumor in normal recipients with an intact mononuclear phagocyte system, as compared with the more rapid emergence of tumors in macrophage-suppressed mice. However, spontaneous metastases of the Os-J tumor were not observed either in normal or macrophage-suppressed mice. Although a high macrophage infiltration of neoplasms could slow tumor growth, this was not associated with the immunogenicity of the neoplasm and did not appear to limit the spontaneous metastasis of this essentially benign neoplasm.

Susceptibility to Cancer and Spontaneous Incidence

Susceptibility to cancer implies being easily affected by carcinogen, as well as having an overt spontaneous incidence of cancer. The susceptibility of a population to the development of fatal cancer of a given organ can be represented by a frequency distribution. This distribution depends both upon the genetic susceptibility of the population and upon all environmental carcinogens that have impinged on that population. The method for construction of such a susceptibility distribution has been simplified and applied to experimental data on bone tumor induction with 90Sr in mice, and to bone tumor mortality and prostate cancer mortality in man. The relative susceptibilities of different human organs to the development of fatal tumors can be defined in terms of the spontaneous tumor mortalities.

Susceptibility to carcinogenesis.

This report examines qualitative and quantitative evidence that the spontaneous incidence of a specific type of tumor is one of the many factors which determine the incidence of carcinogen‐induced tumors of the same type. To avoid selection bias in the choice of data for analysis, all suitable data used in a previous review on a closely related subject are analyzed. One method of attack consists of the mathemetical elimination of factors other than spontaneous incidence which influence carcinogenesis. When unselected carcinogenesis data are examined without such elimination, then the spontaneous incidence often has no apparent effect on induced incidence. The explanation appears to be that the spontaneous incidence is a weak factor which has incomplete penetrance, and frequently is outweighed by other factors. Although the evidence examined is consistent with this conclusion, this does not constitute proof. Regarding mechanism, a carcinogen is seen to enhance the potential for the conversion of normal progenitor cells into cancer cells, which underlies the spontaneous incidence of tumors. It follows that carcinogen assays should be most sensitive, when the type of tumor induced by the carcinogen has a spontaneous incidence which is over but low, or is just barely subthreshold. Cancer 57:2408–2418, 1986.

Immunopathology of Malignant Disease in Mice Leukemias and Lymphomas, Stalking-Horses for Human Counterparts

The last 20 years have seen a veritable explosion in our knowledge about both animal and human tumors of the lymphoid and hemopoietic systems. Today, a bewildering amount of detailed information is available about the causes, varieties, and therapies of these tumors. The challenge for us all is to obtain a coherent overview of this forest of information, which will allow us to recognize individual trees as members of a particular grove, and to know the location of the empty tracts in which future generations may plant their trees.