William F. Feller

Virus-like particles in human milk.

Samples of human milk from 59 women have been partially purified by highspeed density gradient ultracentrifugation. Pellets prepared from partially purified density gradient fractions have been examined by thin‐section electron microscopy. Virus‐like particles closely resembling various stages of the murine B and C‐type RNA tumor viruses have been seen in samples of milk from nine women.

Mammary Tumor Virus Antigen: Sensitive Immunoassay

A rapid, sensitive immuno-assay for mammary tumor virus antigen based on inhibition of passive hemagglutination has been developed. The method permits measurement of this antigen in mouse milk from which the fat has been removed.

Symposium on mammary neoplasia.

An international conference on mammary neoplasia sponsored by the Institute for Medical Research and the National Institutes of Health was held in Cherry Hill New Jersey on November 11-13 1971. 2 reports given focused on the genetic aspects of breast cancer. Bulbrook reported on the urinary steroid excretion patterns in women while Brennan and Wolfe studied the usefulness of xeroradiography in detecting ductal hyperplasia. Paymaster reviewed the epidemiology of breast cancer in India while Ozzello suggested that human breast cancer cells may perform a variety of synthetic and secretory activities. Sarkar suggested that there may be a connection between human breast cancer and RNA viruses and Dalton presented the ultrastructural detail of the mouse feline and human RNA virus. Nandi discussed his recent studies which attempt to locate the mammary tumor virus activity in blood. Concerning tissue and organ culture Lasfargues outlined a new method of growing human breast cancer cells in suspension cultures. Concerning immunology and interferon Blair attempted to elucidate the observation that immunodepression depressed MTV-induced mammary tumor development. Studies have shown striking regression of spontaneous breast cancers in animals following the administration of interferon inducers. Although the role of specific RNA viruses in the oncogenesis of many animal tumors is widely accepted the exact genetic mechanisms by which the viral RNA is expressed causes malignant transformation in the intact animals are not clear. The recent discovery of the enzyme reverse transcriptase and the subsequent demonstration that it is an integral part of all RNA tumor virions has opened a new field of investigation. Spiegelman Schlom Gallo and Temin all reported on it. Muhlbock reported on the influence of prolactin and estrogen on breast cancer as did Meites and Pearson. Thus the relation of an oncogenic virus to breast cancer and the role of reverse transcriptase in tumor viruses were thoroughly discussed at the conference.

Discussion from an article titled studies on the possible viral etiology of human breast cancer

must be present shortly after birth to be effective. It is equally infectious if given orally or by a parenteral route. The development of a mammary malig nancy in a mouse takes approximately 10 months or one half of the usual life-span of the mouse. The malignant transformationisconditionedby three distinct factors: (1) the presence of the virus; (2) the “¿ hormonal milieu― of the animal; and (3) the genetic constitution of the animal. Investigative effort aimed at under standing the exact interrelationship of these three factors is being carried on in a number of laboratories through out the world. Recent work has sug gested that estrogens acting at the cellular level may activate specific genes in the normal mammary epi thelial cells. The cancer virus may in teract with these “¿ activated genes―or their RNA complements to effect a malignant transformation. It is becom ing increasingly evident that a satis factory description of the manner in which the mouse mammary tumor virus produces cancer must depend upon a demonstrable interaction between an RNA virus and a steroid hormone molecule. This virus has been shown under the electron microscope to resemble the influenza virus. Electron micro scopic studies have shown the virus to be present in normal secreting mam mary epithelium, in preneoplastic tissue, and also in the tumor cell itself. The presence of the virus in a mouse cell does not necessarily indicate that the cell is malignant. Biochemical studies on purified preparations have revealed that the virus particle is a lipid-rich particle and contains ap proximately 0.8 per cent ribonucleic acid. It is the RNA which accounts for the essential activity of the virus. The ribonucleic acid is believed to be of a single-strand character. Discussion from an article titled Studies on the Possible Viral Etiology of Human Breast Can cer, by William F. Feller, M.D., Ph.D., Harish Chopra, Ph.D., and Frank Bepko, M.D.