In NER that maintenance DNA damage induced by UV-C irradiation and some chemotherapeutic agents, such as cisPt [57, 58], PCNA facilitates the recruitment of the essential proteins endonuclease XP-G and XP-A for DNA repair [60, 61]. cancer cells. The DNA damage agents used in the study include ionizing radiation source cesium-137 (Cs-137), chemotherapy drug cisplatin (cisPt), ultraviolet-C (UV-C), and oxidative compound H2O2. DNA damage was assessed using immunofluorescent staining of H2AX and the Comet assay. The homologous recombination repair (HRR) was decided using a plasmid-based HRR reporter assay and the nucleotide excision repair (NER) was indirectly examined by the removal of UV-induced cyclobutane pyrimidine dimers (CPD). We found that PCNA-I1S inhibited cell growth in a dose-dependent manner and significantly enhanced the cell growth inhibition induced by pretreatment with DNA damaging brokers Cs-137 irradiation, UV-C, and cisPt. However, the additive growth inhibitory effects were not observed in cells pre-treated with PCNA-I1S, followed by treatment with cisPt. H2O2 enhanced the level of chromatin-bound PCNA in quiescent cells, which was attenuated by PCNA-I1S. DNA damage was induced in cells treated with FASN-IN-2 either PCNA-I1S or cisPt alone and was significantly elevated in cells exposed to the combination of PCNA-I1S and cisPt. Finally, PCNA-I1S attenuated repair of DNA double strand breaks (DSBs) by HRR and the removal of CPD by NER. These data suggest that targeting PCNA with PCNA-I1S may provide a novel approach for enhancing the efficacy of chemotherapy and radiation therapy in treatment of human prostate and lung cancer. Introduction Proliferating cell nuclear antigen (PCNA) is an evolutionally very well conserved multifunctional protein [1, 2] and a non-oncogenic protein essential for tumor cell FASN-IN-2 growth and survival. It is overexpressed in all tumors [2]. Overexpression of PCNA in prostate cancer [3, 4] and non-small cell lung carcinoma (NSCLC) [5] is usually associated with advanced disease and metastasis, and is a reliable biomarker predicting poor prognosis of cancers of various tissue types [3, 4, 6C8]. Given that tumor cells are more active in replication and contain much higher levels of damaged DNA [9, 10] than normal cells, they are more vulnerable to the stress of downregulation or Mouse monoclonal to EGFR. Protein kinases are enzymes that transfer a phosphate group from a phosphate donor onto an acceptor amino acid in a substrate protein. By this basic mechanism, protein kinases mediate most of the signal transduction in eukaryotic cells, regulating cellular metabolism, transcription, cell cycle progression, cytoskeletal rearrangement and cell movement, apoptosis, and differentiation. The protein kinase family is one of the largest families of proteins in eukaryotes, classified in 8 major groups based on sequence comparison of their tyrosine ,PTK) or serine/threonine ,STK) kinase catalytic domains. Epidermal Growth factor receptor ,EGFR) is the prototype member of the type 1 receptor tyrosine kinases. EGFR overexpression in tumors indicates poor prognosis and is observed in tumors of the head and neck, brain, bladder, stomach, breast, lung, endometrium, cervix, vulva, ovary, esophagus, stomach and in squamous cell carcinoma. inhibition of PCNA function. Therefore, targeting PCNA could be an effective approach for treatment of cancer. Native PCNA, present predominantly in the nucleoplasm as free-form PCNA, is usually a ring-shaped homotrimeric protein joined together through head to tail conversation [11, 12]. To be functional, PCNA must be linearized or monomerized, and relocalized. Upon being loaded onto the primer-template junctions of DNA, PCNA encircles DNA, serves as a platform FASN-IN-2 for and interacts with proteins involved in DNA replication and repair and other cellular processes [2, 13C16]. When monomerized and exported to cytoplasm, PCNA was shown to interact with procaspases to inhibit apoptosis [17] and with glycolytic enzymes to promote glycolysis [18]. PCNA also interacts with some cell signaling proteins, such as PI3K proteins, and regulates cell signaling processes [19]. On cell membrane, PCNA interrupts the recognition of tumor cells by natural killer cells [20]. PCNA interacts with its partner proteins made up of PIP (PCNA conversation protein)-box, KA-box, APIM (AlkB homologue 2 PCNA-interacting motif), and other motifs [2, 16, 19]. Great efforts have been made to develop novel approaches targeting PCNA for cancer therapy. Peptides mimicking the APIM or a sequence of caPCNA (cancer associated PCNA) selectively inhibit tumor cell growth, induce apoptosis, and enhance cytotoxicity of chemotherapy drugs on tumor cells [19, 21C23]. The selective inhibitory effects were also observed in malignancy cells treated with small molecule T2AA targeting the PIP-box [24, 25] and small molecule AOH1160 targeting caPCNA [26]. Targeting PCNA in replisomes with monoclonal.
