Some rare genetic variants in a variable tandemly repeated region (minisatellite) of the H-ras gene have been associated with increased risk of cancers, including breast cancer. The aim of this work is to examine the possibility that rare alleles of HRAS1 minisatellite are implicated in the predisposition to develop early-onset breast cancer.

One hundred and nine blood samples of a control population from healthy donors, and 95 samples from unrelated women under 40 years old at diagnosis of a first primary breast cancer, have been studied for HRAS1 minisatellite locus. The analysis of HRAS1 alleles was performed using fluorescent detection of size alleles and MVR-PCR.

After the analysis of the HRAS1 MVR sequences and the length polymorphism typing in the healthy control population and the affected patients, we have observed that 20% of breast cancer patients had at least one rare HRAS1 allele compared to 6.42% of HRAS1 alleles in the control population (χ², P =0.0037). Therefore, the risk of developing breast cancer increases with the presence of rare alleles (OR=3.64 and 95% CI=1.46-9.09). Only 11.58% of breast cancer patients studied showed HRAS1 intermediate alleles, an important decrease compared with 25.69% of intermediate alleles found in the control population.

Our results suggest that the frequency of rare HRAS1 alleles is increased in early-onset breast cancer women, in comparison with a control population. There is also an important decrease in intermediate alleles in the breast cancer population.