Abstract
Proliferating cell nuclear antigen (PCNA) is a highly conserved protein necessary for proper component loading during the DNA replication and repair process. Proteins make a connection within the interdomain connector loop of PCNA, and much of the regulation is a result of the inherent competition for this docking site. If this target region of PCNA is modified, the DNA replication and repair process in cancer cells is potentially altered. Exploitation of this cancer-associated region has implications for targeted breast cancer therapy. In the present communication, we characterize a novel peptide (caPeptide) that has been synthesized to mimic the sequence identified as critical to the cancer-associated isoform of PCNA. This peptide is delivered into cells using a nine-arginine linking mechanism, and the resulting peptide (R9-cc-caPeptide) exhibits cytotoxicity in a triple-negative breast cancer cell line, MDA-MB-436, while having less of an effect on the normal counterparts (MCF10A and primary breast epithelial cells). The novel peptide was then evaluated for cytotoxicity using various in vivo techniques, including ATP activity assays, flow cytometry, and clonogenetic assays. This cytotoxicity has been observed in other breast cancer cell lines (MCF7 and HCC1937) and other forms of cancer (pancreatic and lymphoma). R9-cc-caPeptide has also been shown to block the association of PCNA with chromatin. Alanine scanning of the peptide sequence, combined with preliminary in silico modeling, gives insight to the disruptive ability and the molecular mechanism of action of the therapeutic peptide in vivo.
Footnotes
- Received April 10, 2014.
- Accepted December 5, 2014.
This work was supported by the Department of Defense [Grant W81XWH-11-1-0786 to L.H.M.] and by the National Institutes of Health National Cancer Institute [Grants R01-CA121289 and P30-CA033572]. The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institutes of Health.
↵This article has supplemental material available at molpharm.aspetjournals.org.
- Copyright © 2015 by The American Society for Pharmacology and Experimental Therapeutics
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