Expression Levels Of Parp1 And Phospho-P65 Protein In Human Her2-Positive Breast Cancers.

601 Background: Previous studies have shown that basal breast cancers, which may have an inherent “BRCAness” phenotype and sensitivity to inhibitors of poly (ADP-Ribose) polymerase (PARP), express elevated levels of PARP1. Our lab previously reported that HER2+ breast cancers are exquisitely sensitive to PARP inhibitors (PARPi) thru alteration of the NF-kB pathway. In this study, we assessed levels of PARP1 and phospho-p65, a marker of activated NF-kB, in human breast cancer tissues. Methods: PARP1 and PARP2 copy number, mRNA, and protein expression were assessed by interrogating the PAM-50 defined breast cancer patient set from the TCGA using the cBioPortal. PARP1 and phospho-p65 immunohistochemistry and correlation to clinical parameters were conducted using 307 primary breast cancer specimens (132 basal, 82 luminal, 93 HER2+) through univariate and multivariable analyses. Results: In the PAM50 breast cancer data set, PARP1 and 2 expression was altered in 24/58 (41%) HER2+, 32/81 (40%) basal, and 75/324...