The FTO (fat mass and obesity-associated) gene has a strong linkage disequilibrium block, within which SNPs have been identified that are involved in the development of obesity. Recently some of these variants have also been associated with cancer. However, identification of the possible mechanisms that could explain these associations has proven to be elusive. It has been found that FTO polymorphisms can regulate the expression of genes at large kilobases of distance as well as the expression of the FTO gene itself, and regions for transcription factor binding. To date it has been observed that variants rs9939609, rs17817449, rs8050136, rs1477196, rs6499640, rs16953002, rs11075995 and rs1121980 are associated with the risk of developing cancer. Some studies have produced negative results when comparing the same polymorphisms, but make a simple association between polymorphic variants and cancer, have proved difficult because this relation is by nature multifactorial. A certain degree of variation resulting from the improper design of studies or processing of data can lead to erroneous conclusions. However, it is now unquestionable that certain FTO polymorphisms regulate genetic expression related to cancer susceptibility, although this field is just beginning to be understood.

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BackgroundBreast cancer is a complex multifactorial genetic disease. Among other factors, race and, to an even greater extent, viruses are known to influence the development of this heterogeneous disease. It has been reported that MMTV-like (HMTV) gene sequences with a 90 to 98% homology to mouse mammary tumor virus are found in several populations with a prevalence range of 0 to 74%. In the Mexican population, 4.2% of patients with breast cancer exhibit the presence of HMTV (MMTV-like) sequences. The aim of this study was to evaluate the presence and current prevalence of retroviral HMTV (MMTV-like) sequences in breast cancer in Mexican women.MethodsWe used nested PCR and real-time PCR with a TaqMan probe. As a positive control, we used the C3H MMTV strain inserted into pBR322 plasmid. To confirm that we had identified the HMTV sequences, we sequenced the amplicons and compared these sequences with those of MMTV and HMTV (GenBank AF033807 and AF346816).ResultsA total of 12.4% of breast tumors were HMTV-positive, and 15.7% of the unaffected tissue samples from 458 patients were HMTV-positive. A total of 8.3% of the patients had both HMTV-positive tumor and adjacent tissues. The HMTV-positive samples presented 98% similarity to the reported HMTV sequence.ConclusionsThese results confirm that the HMTV sequence is present in breast tumors and non-affected tissues in the Mexican population. HMTV should be considered a prominent causative agent of breast cancer.

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