Human Mammary Tumor Virus (HMTV) sequences in human milk.

BACKGROUND: Retroviral sequences 90-95% homologous to the mouse mammary tumor virus (MMTV) were present in 38% of the breast cancers studied from American women and were not detectable in non-tumor breast tissue from the same patient. The entire proviral structure was described and viral particles were isolated from primary cultures of human breast cancer. This virus was designated as human mammary tumor virus (HMTV). Hormone response elements present in the HMTV Long-Terminal-Repeat (LTR) suggest a mechanism for association of HMTV with hormonally responding tissues. In fact, the incidence of HMTV sequences is higher in gestational breast cancers, which are associated with hormonal changes. Milk epithelial cells are also under hormonal regulation and therefore are excellent specimens for HMTV sequence detection. METHODS: The HMTV sequence was studied in milk samples from lactating women recruited with increased risk of breast cancer because they had undergone breast biopsies (Biopsy-Group) and lactating women without breast biopsies (Reference-Group). RESULTS: HMTV-env sequences were detected by PCR in milk of 7.61% of 92 women of the Reference-Group and in 20.55% of 73 women of the Biopsy-Group (p: 0.015). The sequences were 94-98% homologous to MMTV. HMTV-env and HMTV-env/LTR junction sequences were detected in high-speed pellet RNA, implying the presence of HMTV viral particles. PCR assays to detect the murine mitochondrial cytochrome oxidase gene and intracisternal-A-type particle sequences were performed to rule out mouse mitochondrial or genomic DNA contamination. Eight women of the 73 Biopsy-Group participants had breast cancer and the milk of only one of these eight women had HMTV-env sequences. In the remaining 65 women of the Biopsy-Group, under enough clinical suspicion to lead to biopsy, HMTV was detected in 14, nearly three times the number of milks as compared to the Reference-Group (21.54% versus 7.61%; p: 0.016). CONCLUSION: The significance of HMTV in milk from the Reference-Group, the greater frequency in the milk of women who had undergone a breast biopsy and its possible infectivity for infants are important questions under study. The similarity of HMTV to MMTV is striking and suggests one possible avenue for viral transmission in humans.

Detection of human mammary tumor virus proteins in human breast cancer cells.

Mouse mammary tumor virus (MMTV) has been proven to induce mammary cancer in mice. MMTV-like env gene sequences have been detected in one-third of the human breast tumors studied. The whole proviral structure with 95% homology to MMTV was found in two human breast tumors and was designated as human mammary tumor virus (HMTV). HMTV viral particles with betaretroviral features have been isolated. In addition, a retrovirus called human betaretrovirus (HBRV), homologous to the mentioned retroviruses, has been isolated from tissues of patients with primary biliary cirrhosis. In this report, the expression of HMTV envelope (Env) and capsid (Ca) was detected in 10 primary cultures of human breast cancer containing HMTV sequences (MSSM) by Western blot and fluorescence activated cell sorting (FACS), using a panel of antibodies against HMTV Env, HBRV Env and Ca and the MMTV Env Gp36 and Ca P27 proteins. By contrast, HMTV proteins did not react with antibody against the MMTV Env Gp52 protein. All the antibodies detected MMTV proteins with exception of two out of four monoclonal antibodies against HMTV Env. Approximately 13% of the MSSM cells showed HMTV protein expression by FACS analysis. This report shows the expression of HMTV proteins for the first time in human breast cancer cells using a panel of antibodies against HMTV, HBRV and MMTV proteins. This should be taken into consideration when MMTV antibodies are used to detect HMTV proteins in human tissues.

Characterization of viral particles isolated from primary cultures of human breast cancer cells.

The association of human breast cancer with sequences similar to the mouse mammary tumor virus (MMTV) has been shown, but convincing evidence for the presence of viral particles in breast tumors has been lacking. We have described the complete proviral structure of a retrovirus in human breast cancer. This provirus, designated as human mammary tumor virus (HMTV), was 95% homologous to MMTV and revealed features of a replication-competent virus. We have therefore investigated the production of viral particles in primary cultures of human breast cancer (MSSM). Cells isolated from ascites or pleural effusions of patients with metastatic breast cancer contained viral sequences in their DNA, expressed Env protein, and showed retroviral particles by electron microscopy. Viral particles from culture media exhibited morphologic features of beta-retroviruses sedimenting at buoyant densities of 1.12 to 1.18 g/mL in sucrose gradients and showed reverse transcriptase activity. cDNA sequences from virion RNA were synthesized, amplified, and sequenced and all the virion genes were detected and 70% of the virion RNA was sequenced. The sequence homologies were, respectively, 85% to 95% compared with the MMTV and HMTV proviruses we have previously described. These results clearly show that breast cancer cells in primary cultures produced HMTV viral particles that are similar to the mouse virus and which may play a role in human breast cancer pathogenesis.

Transcription profile of a human breast cancer cell line expressing MMTV-like sequences.

BACKGROUND: It has been postulated that inflammation caused by certain viruses might result in cancer. Recently, it was shown that childhood lymphoblastic leukemia, breast and ovarian cancers express an interferon-related signature, providing support for this notion. We have previously shown that 38% of the sporadic breast cancers contain MMTV-like env gene sequences. To find out if the presence and expression of MMTV-like sequences correlated with an inflammatory phenotype, we have compared the expression profile of two sublines of MCF-7 cells, one containing the MMTV-like sequences (env+), the other one lacking them (env-). RESULTS: The results indicated that there were 47 differentially expressed genes between the two sublines. Among 27 upregulated genes in the env+ cells there were 7 interferon-related genes, 5 TNF-connected genes and 2 TGFbeta-related genes. CONCLUSION: These results suggest that the env+ cells were most likely responding to an infectious agent, and support the hypothesis that a viral infection may play a role in breast cancer pathogenesis.

Increasing evidence for a human breast carcinoma virus with geographic differences.

BACKGROUND: An early immunologic study suggesting that a virus similar to the mouse mammary tumor virus (MMTV) was associated highly with breast carcinoma in Tunisian patients, compared with patients in the United States, led the authors to examine different breast carcinoma populations by using more current molecular techniques. METHODS: Thirty-nine paraffin blocks were selected for sequencing of the 250-base pair segment of the MMTV from patients with breast carcinoma who were seen and treated at the Institut Salah Azaiz in Tunisia. Fifteen of those blocks were examined under code by a second laboratory, which used a different methodology and was blinded to the results of the first laboratory, and 14 blocks were analyzed successfully. RESULTS: The comparison of Tunisian patients and patients from other countries clearly showed a significantly higher proportion of tumors with MMTV-like sequences in the Tunisian series of patients. There was complete reproducibility of data between the two laboratories. Using the results from the first laboratory and similar studies from the literature, detection of the MMTV-like env gene sequence showed an important geographic pattern with a significantly higher percentage of positive patients with breast carcinoma in Tunisia (74%) compared with patients with breast carcinoma in the United States (36%), Italy (38%), Australia (42%), Argentina (31%), and Vietnam (0.8%) CONCLUSIONS: The findings provided increased evidence for a human breast carcinoma virus with geographic differences in prevalence. The geographic differences were compatible with studies of MMTV in wild mice; thus, the data were plausible biologically.

Poxvirus infection and apoptosis.

The following excellent reviews have been published on poxviruses and apoptosis during the last few years: P.C. Turner and R.W. Moyer, Semin. Virology, 8: 453-469, 1998; J.L. Shisler and B. Moss, Semin. Immunol., 13: 67-72, 2001; and H. Everett and G. McFadden, Curr. Opin. Microbiol., 5: 395-402, 2002. These articles dealt with the viral products and the mechanisms by which they interfere with apoptosis. In this review, we summarize new and old information and also introduce a new approach to explore interactions between the host cell and the replicating virus.

[Detection of murine mammary tumor virus (MMTV) env gene-like sequences in breast cancer from Argentine patients]. / Detección de secuencias homológas al gen env del virus del Tumor Mamario Murino (MMTV) en cáncer de mama de pacientes argentinas.

In the last years research on the possible viral etiology of human breast cancer has been revised. Previous studies have demonstrated the presence of a Mouse Mammary Tumor Virus (MMTV) env gene-like sequence in about 38% of breast cancers from American and Italian women; these sequences are generally absent in other tumors and in normal mammary tissue. In the present study we have analyzed the presence of a 250-bp sequence of the MMTV env gene in breast cancer biopsies from Argentine patients. The retroviral fragment was present in 31% (23/74) of the tumors, only in one normal mammary tissue and in none of the fibroadenomas analYzed. Peripheral blood mononuclear cells (PBMC) from 46 cancer patients were also analyzed; the sequence was found in 17% (2/12) of the PBMC from env positive tumor patients and in 3% (1/34) of the env negatives. The results from Argentine samples are similar to those from USA and Italy, where the breast cancer incidence is alike. These findings support the hypothesis of a viral agent involved in the genesis of this neoplasia and encourage the continuation of these studies.

Deteccion de secuencias homologas al gen env del virus del Tumor Mamario Murino (MMTV) en cancer de mama de pacientes argentinas / Detection of murine mammary tumor virus (MMTV) env gene-like sequences in breast cancer from Argentine patients

In the last years research on the possible viral etiology of human breast cancer has been revised. Previous studies have demonstrated the presence of a Mouse Mammary Tumor Virus (MMTV) env gene-like sequence in about 38% of breast cancers from American and Italian women; these sequences are generally absent in other tumors and in normal mammary tissue. In the present study we have analyzed the presence of a 250-bp sequence of the MMTV env gene in breast cancer biopsies from Argentine patients. The retroviral fragment was present in 31% (23/74) of the tumors, only in one normal mammary tissue and in none of the fibroadenomas analYzed. Peripheral blood mononuclear cells (PBMC) from 46 cancer patients were also analyzed; the sequence was found in 17% (2/12) of the PBMC from env positive tumor patients and in 3% (1/34) of the env negatives. The results from Argentine samples are similar to those from USA and Italy, where the breast cancer incidence is alike. These findings support the hypothesis of a viral agent involved in the genesis of this neoplasia and encourage the continuation of these studies

Detección de secuencias homológas al gen env del virus del Tumor Mamario Murino (MMTV) en cáncer de mama de pacientes argentinas. / [Detection of murine mammary tumor virus (MMTV) env gene-like sequences in breast cancer from Argentine patients]

In the last years research on the possible viral etiology of human breast cancer has been revised. Previous studies have demonstrated the presence of a Mouse Mammary Tumor Virus (MMTV) env gene-like sequence in about 38

of breast cancers from American and Italian women; these sequences are generally absent in other tumors and in normal mammary tissue. In the present study we have analyzed the presence of a 250-bp sequence of the MMTV env gene in breast cancer biopsies from Argentine patients. The retroviral fragment was present in 31

(23/74) of the tumors, only in one normal mammary tissue and in none of the fibroadenomas analYzed. Peripheral blood mononuclear cells (PBMC) from 46 cancer patients were also analyzed; the sequence was found in 17

(2/12) of the PBMC from env positive tumor patients and in 3

(1/34) of the env negatives. The results from Argentine samples are similar to those from USA and Italy, where the breast cancer incidence is alike. These findings support the hypothesis of a viral agent involved in the genesis of this neoplasia and encourage the continuation of these studies.

Deteccion de secuencias homologas al gen env del virus del Tumor Mamario Murino (MMTV) en cancer de mama de pacientes argentinas / Detection of murine mammary tumor virus (MMTV) env gene-like sequences in breast cancer from Argentine patients

In the last years research on the possible viral etiology of human breast cancer has been revised. Previous studies have demonstrated the presence of a Mouse Mammary Tumor Virus (MMTV) env gene-like sequence in about 38% of breast cancers from American and Italian women; these sequences are generally absent in other tumors and in normal mammary tissue. In the present study we have analyzed the presence of a 250-bp sequence of the MMTV env gene in breast cancer biopsies from Argentine patients. The retroviral fragment was present in 31% (23/74) of the tumors, only in one normal mammary tissue and in none of the fibroadenomas analYzed. Peripheral blood mononuclear cells (PBMC) from 46 cancer patients were also analyzed; the sequence was found in 17% (2/12) of the PBMC from env positive tumor patients and in 3% (1/34) of the env negatives. The results from Argentine samples are similar to those from USA and Italy, where the breast cancer incidence is alike. These findings support the hypothesis of a viral agent involved in the genesis of this neoplasia and encourage the continuation of these studies (AU)

En busca de secuencias retrovirales relacionadas con el cáncer de mama humano / Searching for retroviral sequences related to human breast cancer

The participation of viruses in mammary carcinogenesis has been largely studied in animals. A model similar to the mouse mammary tumor virus (MMTV) was previously proposed. Several lines of research supported the participation of MMTV in human breast cancer, but these evidences were contradicted when further research was performed. One major issue was the presence of human endogenous retroviral sequences that confounded results reporting MMTV-like sequences in human breast cancer. To overcome this problem we selected a 660 bp sequence of the MMTV env gene with low homology to endogenous sequences and search for a sequence to it using the polymerase chain reaction (PCR). The sequence was found in 38 of the human breast cancers and in 2 of the normal breasts studied. The sequence was not present in tumors from other organs. It was 90-98 homologous to MMTV and only 18 to human endogenous retrovirus (HERV) K-10. It was also detected in some of the positive tumors by Southern blot hybridization using one of the cloned 660 bp as a probe. Using reverse transcriptase PCR, it was possible to demonstrate that the 660 bp sequence is expressed in the majority of the tumors. Also, preliminary experiments revealed that sequences related to the LTR and gag genes of MMTV were present in the DNA of breast tumors. The origin of the MMTV-like sequences in tumor DNA could be the result of integrated MMTV-like sequences derived from a human mammary virus or may represent unknown endogenous sequences that can only be detected in breast tumors.

En busca de secuencias retrovirales relacionadas con el cáncer de mama humano / Searching for retroviral sequences related to human breast cancer

The participation of viruses in mammary carcinogenesis has been largely studied in animals. A model similar to the mouse mammary tumor virus (MMTV) was previously proposed. Several lines of research supported the participation of MMTV in human breast cancer, but these evidences were contradicted when further research was performed. One major issue was the presence of human endogenous retroviral sequences that confounded results reporting MMTV-like sequences in human breast cancer. To overcome this problem we selected a 660 bp sequence of the MMTV env gene with low homology to endogenous sequences and search for a sequence to it using the polymerase chain reaction (PCR). The sequence was found in 38 of the human breast cancers and in 2 of the normal breasts studied. The sequence was not present in tumors from other organs. It was 90-98 homologous to MMTV and only 18 to human endogenous retrovirus (HERV) K-10. It was also detected in some of the positive tumors by Southern blot hybridization using one of the cloned 660 bp as a probe. Using reverse transcriptase PCR, it was possible to demonstrate that the 660 bp sequence is expressed in the majority of the tumors. Also, preliminary experiments revealed that sequences related to the LTR and gag genes of MMTV were present in the DNA of breast tumors. The origin of the MMTV-like sequences in tumor DNA could be the result of integrated MMTV-like sequences derived from a human mammary virus or may represent unknown endogenous sequences that can only be detected in breast tumors.(Au)