Determinación de anomalías cromosómicas y secuencias de ADN amplificadas en cáncer de mama

Abstract

Breast cancer is the third cause of death in the general population and the second one in Colombian women. In 2002, 40.5% of the cases were of women younger than 50. Breast cancer originates as a result of multiple and consecutive changes in the genome of normal epithelial cells, such as mutations, oncogene activation, inactivation of tumor suppression genes and of DNA damage repairing genes. The latter, can have its origin in chromosomal abnormalities such as monosomies, trisomies, translocations, inversions, loss of genetic material and amplifications, which may lead to over-expression of oncoproteins related with a greater risk of tumor progression (1) (2) (3) (4). However, very little is known about the sequence in which the different types of alterations of the genome appear. n the present study, the chromosomal abnormalities,and amplified DNA sequences were established in breast cancer patients in both samples of peripheral blood and of tissue from the breast tumor of 30 patients. A high frequency of monosomies, specially those of the chromosomes X, 6, 7, 9, 17, 19 and 22 were observed, with statistically meaningful differences between the monosomies of the chromosomes 17 and 22 and the negative STATE for the estrogen and progesterone receptors (p=0.027, p=0.050) and between the monosomy of the chromosome 19 with an advanced age (p=0.034), indicating more aggressive forms of the disease. The monosomies were characteristic of ductal infiltrating carcinomas of any stage and they were observed in a low frequency in other types of carcinomas. Although relationship between the monosomies, fragilities and BREAKINGS of the chromosome 9 with breast cancer has not been reported by previous studies, these chromosomal abnormalities were found in our study in a representative manner and this finding could constitute a new risk marker in this type of cancer. The high frequency and significance of the fragilities found in peripheral blood and (fra 9q12 p=0.001 y fra 3p14 p= 0.38) those of fragilities spontaneously expressed (not induced by the use of specific REACTIVOS) in breast tumor samples (fra 1p11 p= 0.001, fra 2q11 p= 0.002) may somehow confirm the high chromosomal instability in the genome of these patients, probably allowing these fragility tests to be useful in the early determination of the individuals with a high risk of developing breast cancer. Amplification of the ERBb2 and c-myc genes was not observed in FISH assays in any of the analyzed patients; this agrees with related research, in which an over-expression of the protein without an adequate amplification of the gene has been found in this type of tumors, probably due to mutations in the promoter region and an increase in the transcription rate without there being an amplification of the gene (5) (6) (7). The obtained results, although preliminary, are important due to the fact that they contribute to the search of new chromosomal markers and are also important to the orientation of the diagnosis, prognosis and treatment of this disease.