Expression of pp32 gene family members in breast cancer

The pp32 gene family consists of at least three closely related members, pp 32, pp32r1 and pp32r2. In spite of a high degree of identity at the nucleot ide level, pp32 functionally behaves as a tumor suppressor where as pp32r1 and pp32r2 are pro-oncogenic. The purpose of this pilot study was to determ ine pp32-related expression and whether alternative gene use among the pp32 family members occurred in human breast cancer. As a first step, in situ h ybridization with a riboprobe capable of hybridizing with all the three mem bers showed abundant pp32-related mRNA in benign ducts and acini and in inf iltrating ductal carcinomas. A total of 100/102 cases were positive. Furthe r, a detailed molecular analysis by RT-PCR, cloning, and sequencing was per formed in five frozen infiltrating breast carcinomas and matched benign bre ast tissues. Oncogenic pp32r1 (5/5) and pp32r2 (3/5) expression was observe d in carcinomas where as benign breast tissues expressed pp32. 4/5 carcinom as continued to express pp32 but one was devoid of pp32 expression. These r esults suggest that alternative expression of pp32 family members may be co mmon in human breast cancer and the analysis of the profile of pp32-related expression might be helpful in understanding the role of these genes in br east cancer pathogenesis.