Colorectal cancers differ in respect of PARP-1 protein expression

TL;DR

This study investigates PARP-1 protein expression in colorectal cancers, revealing heterogeneity linked to tumor site and stage, which could inform patient selection for PARP inhibitor therapy.

Contribution

It provides the first detailed analysis of PARP-1 expression levels in CRC tissue samples and their association with clinical features.

Findings

68.2% of CRCs show high PARP-1 expression

PARP-1 expression is higher in colon than rectal cancers

Expression varies with tumor stage and site

Abstract

Recent findings raise the possibility of PARP inhibitor therapy in colorectal cancers(CRCs). However, the extent of PARP-1 protein expression in clinical specimens of CRC is not known. Using immunohistochemistry we assessed PARP-1 protein expression in tissue microarrays of 151 CRCs and its association with the patient's age, sex, Astler-Coller stage, grade and site of the tumor. High PARP nuclear immunoreactivity was found in 68.2% (103/151) of all cases. In turn, 31.8% (48/151)of tumors showed low PARP expression, including 9 (6%) PARP-1 negative CRCs. There was a significant association of PARP-1 expression with the site of CRC and Astler-Coller stage. A high PARP expression was noted in 79.1% of colon vs. 53.9% of rectal tumors (p = 0.001). The mean PARP-1 score was 1.27 times higher in colon vs. rectal cancers (p = 0.009) and it was higher in stage B2 vs. stage C of CRCs (p = 0.018). In conclusion, the level of PARP-1 protein nuclear expression is associated with the tumor site and heterogeneous across clinical specimens of CRC, with the majority of CRCs expressing a high level but minority - low or no PARP-1 expression. These findings may have a clinical significance because the assessment of PARP-1 expression in tumor samples may improve selection of patients with CRC for PARP inhibitor therapy.