Human saliva as route of inter-human infection for mouse mammary tumor virus

// Chiara Maria Mazzanti 1, * , Francesca Lessi 1, * , Ivana Armogida 2, 7 , Katia Zavaglia 2 , Sara Franceschi 1 , Mohammad Al Hamad 2, 8 , Manuela Roncella 3 , Matteo Ghilli 3 , Antonio Boldrini 4 , Paolo Aretini 1 , Giovanni Fanelli 2 , Ivo Marchetti 2 , Cristian Scatena 2 , Jacob Hochman 5 , Antonio Giuseppe Naccarato 2, 6 , Generoso Bevilacqua 1, 2 1 FPS – The Pisa Science Foundation, Pisa, Italy 2 Department of Pathology, Pisa University Hospital, Pisa, Italy 3 Breast Center, Department of Breast Surgery, Pisa University Hospital, Pisa, Italy 4 Department of Neonatology, Pisa University Hospital, Pisa, Italy 5 Department of Cell and Developmental Biology, Institute of Life Sciences, The Hebrew University of Jerusalem, Jerusalem, Israel 6 Laboratory of Pathology, “San Rossore” Hospital, Pisa, Italy 7 Current address: Illumina Cambridge Ltd., Cambridge, UK 8 Current address: Department of Pathology, University of Dammam, Dammam, KSA * These authors have contributed equally to this work Correspondence to: Generoso Bevilacqua, e-mail: generoso.bevilacqua@med.unipi.it Keywords: Pathology Section, mouse mammary tumor virus (MMTV), breast cancer, breast cancer etiology, saliva Received: April 12, 2015 Accepted: July 03, 2015 Published: July 15, 2015 ABSTRACT Etiology of human breast cancer is unknown, whereas the Mouse Mammary Tumor Virus (MMTV) is recognized as the etiologic agent of mouse mammary carcinoma. Moreover, this experimental model contributed substantially to our understanding of many biological aspects of the human disease. Several data strongly suggest a causative role of MMTV in humans, such as the presence of viral sequences in a high percentage of infiltrating breast carcinoma and in its preinvasive lesions, the production of viral particles in primary cultures of breast cancer, the ability of the virus to infect cells in culture. This paper demonstrates that MMTV is present in human saliva and salivary glands. MMTV presence was investigated by fluorescent PCR, RT-PCR, FISH, immunohistochemistry, and whole transcriptome analysis. Saliva was obtained from newborns, children, adults, and breast cancer patients. The saliva of newborns is MMTV-free, whereas MMTV is present in saliva of children (26.66%), healthy adults (10.60%), and breast cancer patients (57.14% as DNA and 33.9% as RNA). MMTV is also present in 8.10% of salivary glands. RNA-seq analysis performed on saliva of a breast cancer patient demonstrates a high expression of MMTV RNA in comparison to negative controls. The possibility of a contamination by murine DNA was excluded by murine mtDNA and IAP LTR PCR. These findings confirm the presence of MMTV in humans, strongly suggest saliva as route in inter-human infection, and support the hypothesis of a viral origin for human breast carcinoma.