Loss of heterozygosity in ING3 and ING5 genes in breast cancer

The tumor suppressor genes (TSGs) ING3 and ING5, members of the inhibitor of growth gene family, are effective in inhibition of cell growth and induction of apoptosis. However, in many cancer types, one of the alleles of a TSG is lost through carcinogenesis, while the remaining allele is usually inactivated through a process called loss of heterozygosity (LOH). Previous studies in head and neck cancer revealed that allelic loss and reduced expression is a common pattern of ING gene family members. Fifty paraffin-embedded breast cancer tissues were analyzed by polymerase chain reaction and denatured-polyacrylamide gel electrophoresis for LOH status. The allelic deletion frequency of ING3 and ING5 were detected as 14% and 17% in breast cancer patients, respectively. No significant relationship was detected between ING3 LOH status and clinicopathological variables. Our data also suggest that both ING3 and ING5 LOH statuses have no significant effect in overall survival and disease-free survival of breast cancer patients. These results provide a rational explanation and relative contribution for the complexity of tumor formation, whereby allelic loss of ING3 and ING5 genes is not a major factor for breast cancer but is rather a part of a larger complex mechanism.