Mouse mammary tumour virus-like env nucleotide and p14 signal peptide are present in feline mammary carcinomas, but not in neoplastic or dysplastic canine mammary lesions

PLoS One. 2018 Jul 24;13(7):e0200839. doi: 10.1371/journal.pone.0200839. eCollection 2018.


Mouse mammary tumour virus-like (MMTV-like) is suspected to be involved in human breast cancer and it has been hypothesized that companion animals might have a role in viral transmission. The aim of our study was to investigate the presence of MMTV-like nucleotide sequences and viral protein in a larger number of feline (FMCs) and canine mammary carcinomas (CMCs) by nested PCR and immunohistochemistry. Results showed that the presence of MMTV-like env sequence in FMCs was 7% (6/86), while all the CMCs and canine dysplastic lesions scored negative. All PCR-positive FMCs scored positive for the MMTV p14 signal peptide of the envelope precursor protein of the virus. In contrast, all PCR-negative FMCs and canine mammary lesions were also negative for immunohistochemistry analysis. Canine and feline normal mammary gland tissues scored negative for both PCR and MMTV-p14 protein. Multiple nucleotide alignment of MMTV-like env gene sequences isolated from cat showed 97% and 99% similarity with HMTV and MMTV, respectively, while the others two presented some polimorphisms. Particularly the sequences of one of these two tumors showed a polymorphism (c.7575 A> G), that causes a previously unreported amino acid substitution (Thr > Ala). In conclusion, the results of our study showed the presence of MMTV-like sequences and viral protein in some FMCs. Further studies are needed to understand whether this virus does play a role in the development of FMCs, if MMTV-like is an exogenous virus as these data suggest and, in such a case, how and from whom this virus was acquired.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Breast / pathology
  • Cats
  • DNA, Viral / genetics
  • Dogs
  • Female
  • Gene Products, env / genetics*
  • Genes, env
  • Immunohistochemistry
  • Inflammation
  • Lasers
  • Mammary Neoplasms, Animal / virology*
  • Mammary Tumor Virus, Mouse / genetics*
  • Mice
  • Microdissection
  • Phylogeny
  • Protein Sorting Signals
  • Tumor Virus Infections / virology


  • DNA, Viral
  • Gene Products, env
  • Protein Sorting Signals

Grant support

This work was supported by Università di Pisa grant no. 599999_2017_Neoplasie_Mammarie to AP. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.