PARPs (poly ADP ribose polymerases) are DNA repair enzymes that promote single stranded break (SSB) repair by binding to DNA at the sites of SSBs and recruiting repair machinery. In humans, the PARP superfamily consists of 17 members, of which five play known roles in SSB repair. PARP-1, the most well-studied family member, is required for base excision repair and is thought to be responsible for 90% of PARP activity (5).
PARP inhibitors are a class of pharmacological agents that have been used to treat certain types of cancer, and are designed to induce cell death by preventing cancer cells from repairing damaged DNA. PARP inhibitors have been tested in various combination therapy contexts. For instance, one recent study compared radiation-induced cytotoxicity in cell culture and xenograft models of pancreatic carcinoma and found that PARP inhibition with radiation increased cell death in vitro and reduced tumor growth in vivo (4). In addition to assaying PARP inhibitor responses, this group also used a Novus anti-PARP antibody (NB100-111) to measure PARP expression levels in response to drug treatment using Western Blot, and found that following pharmacological treatment, PARP expression increased in a dose-dependent manner. This finding suggests that PARP inhibitors prevent SSB repair in pancreatic carcinoma models and in turn cause up-regulation of SSB-response pathways (and, therefore, PARP expression) (4). This observed increase in PARP protein expression in response to SSB is common in many experimental contexts, and therefore antibody-based PARP detection is also often used as an assay to quantify genomic damage.
Due to its critical role in SSB repair, PARP is a target of apoptotic caspases (2). Antibodies that detect PARP cleavage products are often used to measure cell apoptosis using western blots and immunohistochemical (IHC) analyses of tissue sections. Novus anti-PARP antibodies have used to detect PARP cleavage products as a readout for apoptosis in a number of studies (1). For example, one group used a Novus anti-PARP antibody to show that apoptosis-induced PARP cleavage increases following protein kinase CK2 inhibition in chronic lymphocytic leukemia cells (3). Another group used a similar PARP cleavage assay to determine the effect of histone deacetylase 4 (HDAC4) knockdown or loss in tumor cell lines, and found that cells with activated DNA-damage pathways are uniquely susceptible to HDAC4 inhibition induced apoptoic cell death (1).
Novus Biologicals offers PARP reagents for your research needs including:
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