Establishment and characterization of a new murine mammary tumor cell line, BALB/c-MC

A new murine mammary tumor cell line (BALB/c-MC) was established from a spontaneous mammary tumor in a 17-mo.-old female mouse of the low mammary cancer strain BALB/cHe. The cell line was derived from a papillary adenocarcinoma. In monolayer culture the line exhibits a pavementlike arrangement of cells and forms "domes" or "hemicysts" as the cells become confluent. The cell line rapidly forms tumors when transplanted into young syngeneic BALB/cHe mice. The subcutaneous injection of 10(6) cells resulted in the development of mammary tumors (typical papillary adenocarcinomas) in 33 of 37 (87%) recipients within 2 to 3 mo. after injection. These mammary tumors also metastasize to lung [14 of 33 (42%) of recipients] during this time. The number of chromosomes in this cell line is hyperdiploid (average of 43, range 39 to 44).

[Spontaneous calcification in F344/Slc and F344/JCL rats]

F344/Slc and F344/JCL rats 2 years of age were histologically examined for the incidence and distribution of calcification. In the male rats of both strains, calcification was observed in the testis, lung, brain, kidney, heart, aorta, cornea, prostate and seminal vesicle respectively. In the female F344/JCL rats, calcification appeared in the kidney, lung, cornea, brain, stomach, ovary and heart. Among these of both sexes, the lung was one of the most affected organs for calcification. On the other hand, calcification in the kidney was more severe and frequent in the females than in the males, suggesting that the sex may be one of enhancing factors for calcification.

Establishment of monoclonal antibodies reactive with epithelial and myoepithelial cells in the breast

Monoclonal antibodies which are considered to be able to differentiate epithelial and myoepithelial cells in the breast have been developed. Human mammary carcinoma cell line (HBC-4W) was used for immunization. Monoclonal antibodies-B4B2F10 (epi-1), E9E8B7 (myo-1)-with IgM was examined using tissues from diseased breast by avidin-biotin-peroxidase assay. Epi-1 antibody reacted with epithelial cells while myo-1 antibody reacted with myoepithelial cells in the mammary glands, respectively. The reaction was markedly visible, in particular, in fibroadenoma, mastopathy, and papilloma, which showed clear two-cell-type structures. In the infiltrating ductal carcinoma, epi-1 antibody reacted with carcinoma cells, while myo-1 antibody reacted with stromal cells rather than carcinoma cells suggesting that infiltrating ductal carcinoma was mainly of epithelial origin. In the infiltrating lobular carcinoma, however, myo-1 as well as epi-1 antibodies reacted with carcinoma cells. It is suggested that infiltrating lobular carcinoma was of a mixture of epithelial and myoepithelial cell origin.

Genetic marker patterns and endogenous mammary tumor virus genes in inbred mouse strains of Japan

In order to establish the genetic relatedness of the inbred mouse strains kept in Nara, genetic marker patterns were determined in conjunction with a study on endogenous mammary tumor viral genes in these strains. Isoenzyme patterns combined with patterns of other genetic markers, show that the unrelatedness between various inbred strains of the dd stock is as high or even higher as between strains of known different origin and geneology. Based on endogenous viral gene patterns the dd stock derived mice can be subdivided into three group, DDD, DDN, DDO, KF and DD/Tbr. The DD/Tbr and its foster-nursed substrain (DD/Tbrf) have the lowest number of endogenous viral genes, i.e. two, while the other strains carry 4-6 such genes. The SLN and SHN strains, derived from a Swiss stock, have a similar pattern of viral genes different that of all other strains studied, also strains of Swiss origin from other sources, such as the NFS and the GR.

Histological distribution of MTV antigen in mice detected by immuno-peroxidase staining

Histological localization of mammary tumor virus (MTV) antigen was investigated using a variety of organs high (DD/Tbr, SHN, SLN, GR) and low (BALB/c) mammary cancer mice strains and immuno-peroxidase staining with MTV antigen. Except for BALB/c strain mice, the mammary gland and mammary tumors were generally positive. Accessory male genital organs including the prostate, seminal vesicle, and coagulating gland also demonstrated a positive reaction, but the testis and female genital organs including uterus and ovaries did not. MTV antigen was also revealed in the serous acini of the salivary gland in both sexes. The site of positive reaction in the accessory male sex organs and salivary gland was located in the apical portion of the secretory epithelial cells and their secretory substance. Localization and intensity of antigenic expression of MTV detected histologically were comparable to results obtained by immunodiffusion test and radioimmunoassay. These evidences support the idea that MTV is transmitted horizontally via seminal fluid or saliva.

Horizontal transmission of the mouse mammary tumor virus in cage mates of the same and opposite sex of low and high mammary cancer strain mice

Horizontal transmission of mouse mammary tumor virus (MTV) was investigated in cage mates of the same and opposite sex of low (BALB/c) and high mammary cancer strains (DD/Tbr, SHN and GR). By MTVp27 and MTVgp52 radioimmunoassay, MTV antigen expression was found in the salivary glands, mammary glands and secondary male genital organs of the MTV-free BALB/c strain. Infectivity and oncogenicity were also found in DDf or BALB/c mice by inoculating extracts of salivary gland and/or seminal vesicle in high mammary cancer strains. It is suggested that the primary source of the infectious agent in cases of caged animals of the same sex is saliva, while the primary source in cases of caged animals of the opposite sex is the seminal fluid, although additional infection through saliva cannot be ruled out in the latter case.

Tissue and organ distribution of mammary tumor virus antigens in low and high mammary cancer strain mice

Expression of mammary tumor virus (MTV) antigen was measured in a wide variety of organs and tissues of a series of high (GR, SHN, SHNf, DD, SLN, SLNf) and low (DDf, DDD, DDDf, KF, KFf, ddY, C57BL, BALB/c) mammary cancer strain mice. Tests were carried out by microimmunodiffusion (micro-ID) and immunoperoxidase tests on formalin-fixed tissues and radioimmunoassays in extracts for 2 viral proteins, MTVp27 from the viral core and MTVgp52 from the viral envelope. Organs with exocrine function, i.e. the mammary gland, salivary gland, coagulating gland and prostate, were mostly positive. The secretory epithelial cells of these organs showed viral antigen expression. Less positivity was encountered in brain, pancreas, stomach, urinary bladder, epididymis, uterus, thymus, spleen, lymph nodes and kidney, plasma and blood cell pools. Unexpectedly the uterus extracts showed MTV antigen expression, occasionally even by immunodiffusion, especially in mice of various DD stocks, but also in the GR strain. Another striking observation was the detection of MTV antigen expression in salivary glands in C57BL strain mice; most other organs of this strain (including the mammary glands) were negative. The implications of results of this extensive survey for MTV antigen expression are discussed for tumorigenesis by MTV of mammary gland and perhaps other tissues in the mouse.

Mammary tumor induction in inbred mouse strains with urethane is not accompanied by changes in expression of B- and C-type retroviral structural proteins

Urethane administrated in the drinking water of breeding female mice of five inbred strains (DDf, KF, C3Hf, ddY and C57BL) leads to a higher incidence of mammary tumors at an extremely early age in four of these strains (DDf, KF, C3Hf and ddY). In the case of the DDf strain the tumors are adenoacanthomas, but in the case of the other strains adenocarcinomas are also observed. The effect of urethane in the drinking water on expression of endogenous retroviral structural proteins of the B and C type (MTV and MuLV) was studied in the milk by an immunodiffusion test and in organ extracts by radioimmunoassays (for MTVp27, MTVgp52 and MuLVp30). Organs tested include salivary glands, thymus and spleen from female and male animals. In addition, prostate and seminal vesicles were tested in male animals and uterus and mammary glands in females. Mammary tumors induced by urethane were also treated. Urethane does not induce or enhance endogenous retroviral antigen expression, either in these organs or in the mammary gland, one of the target organs for tumorigenesis by this agent.

Comparison of mammary tumorigenesis between litters in relation to mammary tumor virus antigenic expression in the milk of C3H/He mice

As a possible step to estimate the relationship between mammary tumor virus (MTV) and mammary tumorigenesis in mice, MTV antigenic expression in mother's milk and spontaneous mammary tumorigenesis in their daughters were compared between the 1st, the 2nd and the 3rd litters of the highly inbred strains of C3H/H3 mice with low mammary tumor incidence. While MTV antigenic expression was detected in all undiluted samples at each litter by immunodiffusion test, the amount of antigen as measured by the single radial immunodiffusion method was increased with increasing litter numbers. On the other hand, the development of preneoplastic mammary hyperplastic alveolar nodules was different little between litters and mammary tumor incidence by 13 months of age was very low with no difference in all litters. The pattern of estrous cycles and plasma prolactin level were also similar in each litter. The results suggest that spontaneous mammary tumorigenesis in mice is not always affected quantitatively by the amount of MTV when endocrine and genetical conditions are similar.

MuMTV antigen expression and mammary tumor incidence in non-inbred dd mice

The expression of mammary tumor virus (MTV) antigen in the milk and various organs of three non-inbred dd mouse stocks (ddO, ddN and ddY) was examined by the immunodiffusion (ID) and micro-immunodiffusion (micro-ID) tests. The rate of MTV antigen expression in the milk was 100% at the first lactation in ddO (6/6) and ddN mice (10/10), and 23% in ddY mice (3/13). Mammary tumor incidence was 13% (mean tumor age: 12.0 months), 32% (9.6 months) and 10% (11.5 months) in ddO, ddN and ddY mice, respectively, In F1 hybrids between MTV-free BALB/c females and dd males, a high level of MTV antigen was detected by the ID test in the milk of (BALB/c X ddO) F1, however, the levels in (BALB/c X ddN) F1 and (BALB/c X ddY) F1 mice were low at the first lactation and elevated with the advance of lactation number. Mammary tumor incidence had a trend to be higher and earlier in these F1 hybrids than in non-inbred dd stocks. The development of mammary tumors and detection of MTV antigen in F1 hybrids indicate the extrachromosomal transmission of MTV by male dd mice. The micro-ID test has shown that the mammary tumors, mammary glands, male genital organs except for the testis and the salivary gland expressed MTV antigen, with a high frequency of suggesting that secondary male genital organs may play an important role in MTV infection in mice.

Strain difference in the expression of mammary tumor virus antigen in the male genital organs of mice during aging

Mammary tumor virus (MTV) antigen expression was tested in the male genital organs (testis, epididymis, prostate, seminal vesicle and coagulating gland) of DD/Tbr, KF and DDD strains (dd (German) mouse group), GR strain (Swiss origin), SHN and SLN strains (different Swiss origin), C3H and A strains (American origin), BALB/c and C57BL strains (low mammary tumor strains), and DDf and SHNf strains (MTV eliminated strains). Microimmunodiffusion analysis showed that expression of MTV antigen is tissue extracts was found most frequently in the prostate, sometimes in the seminal vesicle and coagulating gland but rarely in the epididymis and not at all in the testis of mammary cancer strains. No expression was found in these organs from BALB/c and C57BL strains. The earliest expression was found in GR, SHN and SLN strains of Swiss origin. Expression was not lost in SHNf strain, indicating that it is due to genetically transmitted MTV, rather than a milk-factor. Male genital organs from two mammary cancer strains of American origin became positive occasionally at rather higher age than in the strains of Swiss origin. DD/Tbr, KF and DDD strains expressed MTV antigen in the male genital organs at intermediate age between the strains of Swiss origin and American origin. Complete disappearance of MTV antigen expression in these organs of DDf strain indicates that the expression of MTV in DD/Tbr is due to a milk-factor.

Mammary tumor virus antigen expression in inbred mouse strains of European origin established in Japan

Expression of the mammary tumor virus (MTV) antigen in the milk from inbred mouse strains maintained in Japanese laboratories was investigated by means of the immunodiffusion test (ID) and the results were compared with the incidence of mammary tumors in breeding females of identical strains. Japanese strains tested were classified into two groups. The DD/Tbr, DDD and KF strains were derived from "dd" stock mice, and they showed equally high incidences of MTV antigen expression in the milk, though each strain developed mammary tumors with different incidences; 71%, 14% and 22%, respectively. Other strains originated from Swiss albino mice. The incidence of MTV antigen expression in the milk of SHN and SLN strains was the same as that of mammary tumors at an early age.