The expression of APE1 in triple-negative breast cancer and its effect on drug sensitivity of olaparib.

Triple-negative breast cancer is a kind of breast cancer with poor prognosis and special biological behavior, which lacked endocrine therapy and targeted therapy. We investigate the effect of human APE1 (apurinic/apyrimidyl endonuclease 1), a rate-limiting enzyme of base excision repair, on the prognosis in triple-negative breast cancer and drug sensitivity of olaparib. The expression of APE1 was detected by immunohistochemistry in the triple-negative breast cancer tissues and its effect on survival of triple-negative breast cancer patients was followed. To find whether APE1 effect the drug sensitivity in triple-negative breast cancer cells, the APE1-knockout HCC1937 cell line (triple-negative breast cancer cell line) was established by CRISPR/Cas9 system. Then, we use the wild-type and knockout one to test the drug sensitivity of olaparib. The expression of APE1 in triple-negative breast cancer tissues was significantly higher than that in the adjacent tissues (85.6% vs 14.4%) and its expression was related to tumor size (p < 0.05). We also found that it is an independent prognostic factor in patients with triple-negative breast cancer (overall survival, p = 0.01). In vitro assay, the half maximal inhibitory concentration of olaparib in HCC1937-APE1-KO was significantly increased (17.22 vs 91.85 µM) compared to the wild type. The growth curve showed that olaparib had a stronger lethality on HCC1937 compared to HCC1937- APE1-KO (p < 0.05 on day 3). HCC1937 resulted in more mitotic G2/M arrest and increased apoptosis rate after treatment with 40 µM of olaparib, while HCC1937-APE1-KO did not change significantly. When HCC1937 was treated with different concentrations of olaparib, it was found that APE1 expression decreased more significantly at 15 µM of olaparib was. In HCC1937-APE1-KO, the expression of endogenous poly (ADP-ribose) polymerase 1 was also less than that of HCC1937. These results suggested that the expression of APE1 was an important basis for the maintenance of poly (ADP-ribose) polymerase 1, and the deletion of APE1 may be related to the resistance of olaparib.

An Update on Poly(ADP-ribose) Polymerase I-A Brief Review.

Poly (ADP-ribose) polymerase 1 (PARP1) plays important roles in both DNA repair and transcription, and the interplay of these processes in relation to cellular function and disease states has not been well defined. The tumor-suppressor effects of PARP inhibitors have attracted significant interest in the development of novel cancer therapies. As PARP1 binding motifs may be readily found in promoter elements of DNA repair genes, the expanding role of PARP1 in DNA repair does not have to be independent of transcription. The discovery of ADP-ribose binding modules that bind to various forms of mono- and poly-ADP-ribose has provided important insights into how ADPribosylation regulates different cellular pathways. Among the four distinct PAR-binding modules discovered so far, it is the macrodomain alone that, in addition to possessing binding activity, in some instances, also supports a catalytic activity toward ADP-ribose derivatives. However, the development of PARP inhibitors as chemopotentiating agents has been limited by an increase in observed toxicity, mainly myelosuppression, necessitating dose reduction of the cytotoxic chemotherapeutic agent and the PARP inhibitor. Hence, it presents an opportunity to rationally develop combinations of PARP inhibitors with new classes of DNA repair inhibitors that are on the horizon and classical cytotoxic agents. Clinical trials of PARP inhibitors are investigating various uses of these approaches in cancer. Recent studies on the clinical significance of PARP1 inhibitors are discussed in this review. These recent research advances will inform the selection of patient populations who can benefit from the PARP inhibitor treatment and the development of effective drug combination strategies.

Inhibition of poly (ADP-Ribose) polymerase: A promising strategy targeting pancreatic cancer with BRCAness phenotype.

The use of chemotherapeutic regimens for the treatment of pancreatic cancer is still limited because pancreatic cancer is usually diagnosed at an advanced stage as a refractory disease in which symptoms are difficult to recognize in the early stages. Furthermore, at advanced stages, there are important challenges to achieve clinical benefit and symptom resolution, even with the use of an expanded spectrum of anticancer drugs. Recently, a point of reduced susceptibility to conventional chemotherapies by breast cancer susceptibility gene (BRCA) mutations led to a new perspective for overcoming the resistance of pancreatic cancer within the framework of increased genome instability. Poly (ADP-Ribose) polymerase (PARP) -1 is an enzyme that can regulate intrinsic functions, such as response to DNA damage. Therefore, in an environment where germline mutations in BRCAs (BRCAness) inhibit homologous recombination in DNA damage, resulting in a lack of DNA damage response, a key role of PARP-1 for the adaptation of the genome instability could be further emphasized. Here, we summarized the key functional role of PARP-1 in genomic instability of pancreatic cancer with the BRCAness phenotype and listed clinical applications and outcomes of PARP-1 inhibitors to highlight the importance of targeting PARP-1 activity.

Poly(ADP-ribose) polymerase-1 inhibitor ameliorates dextran sulfate sodium-induced colitis in mice by regulating the balance of Th17/Treg cells and inhibiting the NF-κB signaling pathway.

Poly(ADP-ribose) polymerase-1 (PARP-1) plays a critical role in inflammatory pathways. The PARP-1 inhibitor, 5-aminoisoquinolinone (5-AIQ), has been demonstrated to exert significant pharmacological effects. The present study aimed to further examine the potential mechanisms of 5-AIQ in a mouse model of dextran sodium sulfate (DSS)-induced colitis. Colitis conditions were assessed by changes in weight, disease activity index, colon length, histopathology and pro-inflammatory mediators. The colonic expression of PARP/NF-κB and STAT3 pathway components was measured by western blot analysis. Flow cytometry was used to analyze the proportion of T helper 17 cells (Th17) and regulatory T cells (Tregs) in the spleen. Western blot analysis and reverse transcription-quantitative PCR were employed to determine the expression of the transcription factors retinoic acid-related orphan receptor and forkhead box protein P3. The results demonstrated that 5-AIQ reduced tissue damage and the inflammatory response in mice with experimental colitis. Moreover, 5-AIQ increased the proportion of Treg cells and decreased the percentage of Th17 cells in the spleen. Furthermore, following 5-AIQ treatment, the main components of the PARP/NF-κB and STAT3 pathways were downregulated. Collectively, these results demonstrate that the PARP-1 inhibitor, 5-AIQ, may suppress intestinal inflammation and protect the colonic mucosa by modulating Treg/Th17 immune balance and inhibiting PARP-1/NF-κB and STAT3 signaling pathways in mice with experimental colitis.

Fluorine-18 labeled poly (ADP-ribose) polymerase1 inhibitor as a potential alternative to 2-deoxy-2-[18F]fluoro-d-glucose positron emission tomography in oral cancer imaging.

OBJECTIVES: The evaluation of disease extent and post-therapy surveillance of head and neck cancer using 2-deoxy-2-[18F]fluoro-d-glucose ([18F]FDG) PET is often complicated by physiological uptake in normal tissues of the head and neck region, especially after surgery or radiotherapy. However, irrespective of low positive predictive values, [18F]FDG PET remains the standard of care to stage the disease and monitor recurrences. Here, we report the preclinical use of a targeted poly (ADP-ribose) polymerase1 (PARP1) binding PET tracer, fluorine-18 labeled poly (ADP-ribose) polymerase1 inhibitor ([18F]PARPi), as a potential alternative with greater specificity. METHODS: Using an orthotopic xenograft mouse model injected with either FaDu or Cal 27 (human squamous cell carcinoma cell lines) we performed PET/CT scans with the 2 tracers and compared the results. Gamma counts and autoradiography were also assessed and correlated with histology. RESULTS: The average retained activity of [18F]PARPi across cell lines in tumor-bearing tongues was 0.9 ±â€¯0.3%ID/g, 4.1 times higher than in control (0.2 ±â€¯0.04%ID/g). Autoradiography and histology confirmed that the activity arose almost exclusively from the tumor areas, with a signal/normal tissue around a ratio of 42.9 ±â€¯21.4. In vivo, [18F]PARPi-PET allowed delineation of tumor from healthy tissue (p < .005), whereas [18F]FDG failed to do so (p = .209). CONCLUSIONS AND IMPLICATIONS FOR PATIENT CARE: We demonstrate that [18F]PARPi is more specific to tongue tumor tissue than [18F]FDG. [18F]PARPi PET allows for the straightforward delineation of oral cancer in mouse models, suggesting that clinical translation could result in improved imaging of head and neck cancer when compared to [18F]FDG.

Attenuation of the progression of adjuvant-induced arthritis by 3-aminobenzamide treatment.

Rheumatoid arthritis (RA) is a disease that is still insufficiently controlled by current treatments. Poly(ADP-ribose) polymerase (PARP) inhibitors ameliorate immune-mediated diseases in several experimental models, including RA, colitis, experimental autoimmune encephalomyelitis and allergy. Together these findings showed that ADP-ribosylating enzymes, in particular PARP-1, play a pivotal role in the regulation of immune responses and may represent a noble target for new therapeutic approaches in immune-mediated diseases. The effect of 3-aminobenzamide (3-AB), an inhibitor of poly(ADP-ribose) synthetase activity, was evaluated in a mouse model of adjuvant-induced arthritis (AIA) on pro-inflammatory cytokines, adhesion molecules, inflammatory mediators and chemokine production/expression in serum and knee joint. Histopathological examination was also done on joint section. Our data demonstrates that 3-AB, 10mg/kg, intraperitoneally (i.p.) significantly reduces pro-inflammatory cytokine (IL-17, TNF-α and IL-2) and chemokine (MCP-1 and MIP-2) production/expression, accompanied by amelioration of the disease as indicated by reduced paw swelling and arthritic scores and was associated with a significant reduction of VCAM-1 and ICAM-1 expression in the knee joint. Moreover, the expression of inflammatory mediators (iNOS, COX-2, MMP-2, MMP-9) and joint histological inflammatory damage was also markedly decreased. The results of this study suggest that PARP-1 inhibitor may play a role in the inflammatory arthritic process after administration of 3-AB may be a beneficial therapeutic approach.

XRCC2 rs3218536 polymorphism decreases the sensitivity of colorectal cancer cells to poly(ADP-ribose) polymerase 1 inhibitor.

Single nucleotide polymorphisms (SNPs) are associated with the development of certain types of cancer. The present study aimed to investigate the association between X-ray repair complementing defective repair in Chinese hamster cells 2 (XRCC2) SNPs and colorectal cancer (CRC) cell sensitivity to the poly(ADP-ribose) polymerase (PARP) 1 inhibitor olaparib (AZD2281). SNaPshot® analysis of XRCC2 SNPs was performed in five CRC cell lines. The AZD2281-sensitivities of the CRC cells were also analyzed using MTT assays. The effect of AZD2281 on XRCC2 and PARP1 expression was investigated in the five cell lines using quantitative polymerase chain reaction and western blot analyses. Parallel investigations were performed using a cisplatin (DDP) model of DNA damage. The XRCC2 rs3218536 SNP was found to be associated with the LoVo microsatellite instability CRC cell line. The relative rate of growth inhibition was found to be lower in the LoVo cells following treatment with AZD2281 compared with the other four cell lines (P=0.002). Furthermore, the XRCC2 mRNA level in the LoVo cells was observed to be significantly higher than that in the other four cell lines (P<0.05). Similar results were found using the DDP model of DNA damage (P<0.05). The present study indicated that the XRCC2 rs3218536 polymorphism decreases the sensitivity of CRC cells to AZD2281.