Expression of the double-strand RNA activated protein kinase (PKR) and its prognostic significance in patients with locally advanced rectal cancer

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3643 Background: The interferon induced, dsRNA-activated, protein kinase, PKR is a key regulator of translational initiation, playing an important role in the regulation of cell proliferation, apoptosis, and transformation. Increased expression of PKR has been shown to correlate with better patient prognosis in head and neck cancer ( Haines et al. Arch. Otolaryngol. Head Neck Surg. 1993). The aim of this study is to identify the prognostic significance of PKR in locally advanced rectal cancer. Methods: One hundred nine patients had potentially curative surgical resection and were treated with chemoradiation therapy followed by 5-fluorouracil based chemotherapy. Paraffin embedded tumor tissue was collected and evaluated in 92 patients. Samples were immunohistochemically stained with the monoclonal antibody TJ4C4. Overall scores for PKR expression were calculated based on staining intensity and percentage of immunoreactive tumor cells. Clinical information including tumor grade, stage, carcinoembryonic antigen (CEA), disease-free survival (DFS), and overall survival (OS) was evaluated and compared by PKR expression. Results: The median follow-up duration was 30 months. The PKR score was not related to the tumor grade, stage, CEA level. The relapse rate was lower in high PKR score group (>7.0) than low PKR score group, though statistically insignificant (27.5% vs. 41.5% p=0.158). There was no significant difference in 5-year DFS (70.2% vs. 47.1%, p=0.3575) and 5- year OS (74.3% vs. 53.9%, p=0.9283) between the two groups. Cox regression multivariate analyses showed that new AJCC stage and tumor differentiation were significant independent prognostic factors in both DFS and OS. Conclusions: The levels of PKR expression were not associated with clinical outcome in locally advanced rectal cancer patients. No significant financial relationships to disclose.

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