Alterations of the 16q22.1 and 16q24.3 chromosomal loci in sporadic invasive breast carcinomas: Correlation with proliferative activity, ploidy and hormonal status of the tumors

Background: Breast cancer is characterized by complex genetic alterations found in multiple chromosomal regions, most commonly losses of 17p, 16q, 8p and others. A number of tumor suppressor genes mapped on these loci have been investigated in mammary tumors, whereas other gene products are of unclear function and await identification. Materials and Methods: We analyzed the loss of heterozygosity (LOH) of two chromosomal loci: a. 16q24.3 using the genetic markers D16S303, D16S3026 and D16S3407 and b. 16q22.1, the locus of E-cadherin gene, using the microsattelite markers D16S503, D16S752 and D16S512, in a series of 63 sporadic invasive breast carcinomas consisting of 56 ductal, 4 lobular and 3 tumors of mixed type. Our findings were correlated with proliferative activity, ploidy and hormonal status of the tumors. Results: Fourteen (22.2%) tumors demonstrated LOH of 16q24.3. Allelic imbalance of the 16q22. 1 locus was found in 19 of 61 informative cases (31%) and commonly coexisted with LOH of 16q24.3. A significant association was observed between LOH of D16S752 and the absence of progestel one receptors in tumor cells (p=0.005). Conclusions: LOH of 16q24.3 and 16q22. 1 are frequent genetic alterations in breast cancer and they do nor seem to correlate with rumor cell proliferation or ploidy. The statistical association between LOH of 16q24.3 and progesterone receptors need to be further investigated in larger series.