Presence of mouse mammary tumour-like virus gene sequences may be associated with morphology of specific human breast cancer.
BACKGROUND
Mouse mammary tumour virus (MMTV) has a proven role in breast carcinogenesis in wild mice and genetically susceptible in-bred mice. MMTV-like env gene sequences, which indicate the presence of a replication-competent MMTV-like virus, have been identified in some human breast cancers, but rarely in normal breast tissues. However, no evidence for a causal role of an MMTV-like virus in human breast cancer has emerged, although there are precedents for associations between specific histological characteristics of human cancers and the presence of oncogenic viruses.


OBJECTIVE
To investigate the possibility of an association between breast cancer and MMTV-like viruses.


METHODS
Histological characteristics of invasive ductal human breast cancer specimens were compared with archival MMTV-associated mammary tumours from C3H experimental mice. The presence of MMTV-like env DNA sequences in the human breast cancer specimens was determined by polymerase chain reaction and confirmed by Southern hybridisation.


RESULTS
MMTV-like env gene sequences were identified in 22 of 59 (37.3%) human breast cancer specimens. Seventeen of 43 (39.5%) invasive ductal carcinoma breast cancer specimens and 4 of 16 (25%) ductal carcinoma in situ specimens had some histological characteristics, which were similar to MMTV-associated mouse mammary tumours. However, these similarities were not associated with the presence or absence of MMTV-like gene sequences in the human breast tumour specimens. A significant (p = 0.05) correlation was found between the grade of the human breast cancer and similarity to the mouse mammary tumours. The lower the grade, the greater the similarity.


CONCLUSIONS
Some human breast cancer specimens, in which MMTV-like env DNA sequences have been identified, were shown to have histological characteristics (morphology) similar to MMTV-associated mouse mammary tumours. These observations are compatible with, but not conclusive of, an association between the presence of MMTV-like env DNA sequences and some human breast cancers.
Lawson
J S
JS
School of Public Health and Community Medicine, University of New South Wales, Sydney, Australia. lawson@unsw.edu.au
Tran
D D
DD
Carpenter
E
E
Ford
C E
CE
Rawlinson
W D
WD
Whitaker
N J
NJ
Delprado
W
W
D000818:Animals; D001943:Breast Neoplasms / Q000473:pathology / Q000821:virology*; D018270:Carcinoma, Ductal, Breast / Q000473:pathology / Q000821:virology*; D002285:Carcinoma, Intraductal, Noninfiltrating / Q000473:pathology / Q000821:virology*; D004279:DNA, Viral / Q000032:analysis; D005260:Female; D006801:Humans; D015674:Mammary Neoplasms, Animal / Q000473:pathology / Q000821:virology; D008324:Mammary Tumor Virus, Mouse / Q000235:genetics / Q000302:isolation & purification*; D051379:Mice; D008809:Mice, Inbred C3H; D016133:Polymerase Chain Reaction / Q000379:methods; D012192:Retroviridae Infections / Q000150:complications; D014412:Tumor Virus Infections / Q000150:complications; D014759:Viral Envelope Proteins / Q000032:analysis
D004279:DNA, Viral; D014759:Viral Envelope Proteins