Enhancement of poly-adenosine diphosphate-ribosylation in human hepatocellular carcinoma

Preclinical selection of a novel poly(ADP-ribose) polymerase inhibitor for clinical trial

Poly(ADP-ribose) polymerase (PARP)-1 (EC 2.4.2.30) is a nuclear enzyme that promotes the base excision repair of DNA breaks. Inhibition of PARP-1 enhances the efficacy of DNA alkylating agents, topoisomerase I poisons, and ionizing radiation. Our aim was to identify a PARP inhibitor for clinical trial from a panel of 42 potent PARP inhibitors (K(i), 1.4-15.1 nmol/L) based on the quinazolinone, benzimidazole, tricyclic benzimidazole, tricyclic indole, and tricyclic indole-1-one core structures. We evaluated chemosensitization of temozolomide and topotecan using LoVo and SW620 human colorectal cells; in vitro radiosensitization was measured using LoVo cells, and the enhancement of antitumor activity of temozolomide was evaluated in mice bearing SW620 xenografts. Excellent chemopotentiation and radiopotentiation were observed in vitro, with 17 of the compounds causing a greater temozolomide and topotecan sensitization than the benchmark inhibitor AG14361 and 10 compounds were more potent radiosensitizers than AG14361. In tumor-bearing mice, none of the compounds were toxic when given alone, and the antitumor activity of the PARP inhibitor-temozolomide combinations was unrelated to toxicity. Compounds that were more potent chemosensitizers in vivo than AG14361 were also more potent in vitro, validating in vitro assays as a prescreen. These studies have identified a compound, AG14447, as a PARP inhibitor with outstanding in vivo chemosensitization potency at tolerable doses, which is at least 10 times more potent than the initial lead, AG14361. The phosphate salt of AG14447 (AG014699), which has improved aqueous solubility, has been selected for clinical trial.

Poly(ADP-ribose) polymerase (PARP) and DNA-fragmentation factor (DFF45): Expression and correlation in normal, hyperplastic and neoplastic endometrial tissues

This study evaluated the immunohistochemical expression of poly(ADP-ribose) polymerase (PARP) and DNA fragmentation factor 45 (DFF45) in normal endometria (NE, n=13), non-atypical (NAH, n=22) and atypical hyperplasia (AH, n=14), endometrioid carcinoma (EC, n=34), serous carcinoma (SC, n=10), and clear cell carcinoma (CCC, n=2). With regard to quantity and intensity of positively stained cells, immunostaining was scored as negative, low, and strong. Nuclear PARP immunoreactivity was found in all cases. If present, DFF45 immunoreactivity was detected predominantly in the nucleus and to some extent in the cytoplasm. PARP immunoreactivity increased significantly from NE via NAH to AH (P=0.0004), and decreased from AH to endometrial carcinomas (P=0.0054). DFF45 immunoreactivity increased significantly from NE to NAH and to AH (P=0.0009). No significant differences were calculated between AH and endometrial carcinomas (P=0.7495). FIGO stages and tumor grades could not be characterized by PARP and DFF45 immunoexpression (P=1.000 and 0.7383, as well as P=0.3034 and 0.7533, respectively). Pearson correlation revealed significant associations of PARP and DFF45 immunoscores for all diagnostic categories of NE, NAH, AH, EC, and SC/CCC. Immunoexpression of PARP and DFF45 is apparently altered in endometrial carcinomas as compared with non-neoplastic endometrial tissues, indicating impaired mechanisms of apoptosis in the former.

Relationship between expression of poly adenosine diphosphate-ribose polymerase-1 and its biological characteristics in human hepatocellular carcinoma

AIM: To investigate the expression of poly adenosine diphosphate-ribose polymerase-1 (PARP-1) in human hepatocellular carcinoma (HCC) and its adjacent liver tissues as well as the correlation between the expression of PARP-1 and the biological characteristics.

METHODS: Immunohistochemical staining and Western blotting were employed to examine the expression of PARP-1 in HCC and its adjacent liver tissues obtained from the surgical specimens of 40 HCC patients who underwent liver resections in our hospital, and the correlation between the expression level of PARP-1 and the differentiation, recurrence and metastasis of HCC were analyzed.

RESULTS: The expression of PARP-1 was mainly located in the nucleus, and the rate of PARP-1 expression in HCC was significantly higher than that in its adjacent liver tissues (t = 6.49, P < 0.01). The rates of PARP-1 expression in the poorly differentiated HCC were significantly greater than those in the well and moderately differentiated HCC (t = 4.57, P < 0.01). Furthermore, the expression rates in the HCC with recurrence and metastasis were significantly higher than those in the ones without recurrence and metastasis (t = 3.33, P < 0.01).

CONCLUSION: PARP-1 expression is up-regulated in HCC, and the up-regulation of PARP-1 is closely correlated with the differentiation and metastasis. This study indicates that the PARP-1 gene may be involved in the carcinogenesis and development of human HCC.

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Poly(adenosine diphosphate-ribose) polymerase 1 expression in malignant melanomas from photoexposed areas of the head and neck region

The family of the poly(adenosine diphosphate-ribose) polymerase (PARP) proteins is directly involved in genomic stability, DNA repair, and apoptosis by DNA damage. In this study, we evaluated the role of PARP-1 in melanoma and its prognostic importance. We studied by immunohistochemistry and Western blot analysis PARP-1 expression in a selected series of 80 primary melanoma of the head and neck region. The results were correlated with tumor thickness and patient's outcome. A follow-up of at least 3 years was available. Fifteen cases of benign melanocytic nevi were used as controls. Normal melanocytes showed only scattered, focal nuclear positivity and were considered as negative for PARP-1 expression by immunohistochemistry (score, 0). Thirty cases of melanoma (37.5%) showed nuclear expression of PARP-1 in both radial and vertical growth phases. Western blot analysis showed the presence of a high signal for full-length PARP-1 only in the cases with high immunohistochemical (nuclear) expression of protein (score, ++/+++) in both radial and vertical growth phase. A significant correlation was present between PARP-1 expression in vertical growth phase and the thickness of tumor lesion (P = .014); all but one tumor measuring less than 0.75 mm showed no or low PARP-1 expression. No correlation was found between PARP-1 expression in radial growth phase and tumor thickness (P = .38, data not shown). These data suggest that PARP-1 overexpression is a potential novel molecular marker of aggressive cutaneous malignant melanoma and a direct correlation between PARP-1-mediated inhibition of the apoptosis and biologic behavior of cutaneous malignant melanoma.