PARP1-modulated chromatin remodeling is a new target for cancer treatment.

Cancer progression requires certain tumorigenic mutations in genes encoding for different cellular and nuclear proteins. Altered expressions of these mutated genes are mediated by post-translational modifications and chromatin remodeling. Chromatin remodeling is mainly regulated by the chromatin remodeling enzyme complexes and histone modifications. Upon DNA damage, Poly-(ADP-ribose) Polymerase1 (PARP1) plays a very important role in the induction of chromatin modifications and activation of DNA repair pathways to repair the DNA lesion. It has been targeted to develop different anti-cancer therapeutic interventions and PARP inhibitors have been approved by the U.S. Food and Drug Administration (FDA) for clinical use. But it has been found that the cancer cells often develop resistance to these PARP inhibitors and chromatin remodeling helps in enhancing this process. Hence, it may be beneficial to target PARP1-mediated chromatin remodeling, which may allow to reverse the drug resistance. In the current review, we have discussed the role of chromatin remodeling in DNA repair, how PARP1 regulates modifications of chromatin dynamics, and the role of chromatin modifications in cancer. It has also been discussed how the PARP1-mediated chromatin remodeling can be targeted by PARP inhibitors alone or in combination with other chemotherapeutic agents to establish novel anti-cancer therapeutics. We have also considered the use of PARG inhibitors that may enhance the action of PARP inhibitors to target different types of cancers.

Olaparib enhances curcumin-mediated apoptosis in oral cancer cells by inducing PARP trapping through modulation of BER and chromatin assembly.

Apart from inducing catalytic inhibition of PARP-1, PARP inhibitors can also trap PARP proteins at the sites of DNA damage and forming toxic PARP-DNA complexes. These complexes obstruct the DNA repair process, resulting in cancer cell death. To study the detailed mechanism of anti-cancer action through PARP trapping, we have treated oral cancer cells (H-357) with curcumin (Cur), olaparib (Ola) and their combination (Cur + Ola). Cur + Ola treatment triggered the expressions of PARP-1 and adenomatous polyposis coli (APC) and down regulated other base excision repair (BER) proteins in the chromatin fraction but not in the nuclear fraction. Cur + Ola treatment inhibited PARylation, altered interaction of PARP-1 with representative BER proteins and arrested cells in S-phase. We have for the first time provided direct evidence and measured the cellular PARP-1 trapping potentiality of Ola in Cur pretreated H-357 cells. Unchanged cellular PARP-1 trapping, unaltered expression of BER proteins and BER activity were found in APC silenced H-357 cells, which further confirmed that the DNA damage/repair response was APC-dependent. Interestingly, complete abolishment of the chromatin remodeler 'amplified in Liver Cancer 1' (ALC1), decreased expression of Histone H3 and histone acetyltransferase (P300) was noted in chromatin of Cur + Ola treated cells. Their expressions remained unchanged in APC silenced cells. Cur + Ola also altered the interaction of ALC1 with BER proteins including APC. Thus, the present study reveals that Cur + Ola treatment increased oral cancer cell death not only through catalytic inhibition of PARP-1 but also predominantly through PARP-1 trapping and indirect inhibition of chromatin remodeling.

PARP inhibitor Veliparib (ABT-888) enhances the anti-angiogenic potentiality of Curcumin through deregulation of NECTIN-4 in oral cancer: Role of nitric oxide (NO).

Concurrent use of DNA damaging agents with PARP inhibitors contribute to the effectiveness of the anticancer therapy. But there is a dearth of reports on the antiangiogenic effects of PARP inhibitors and the suppression of angiogenesis by this drug combination is not yet reported. For the successful development of cancer therapeutics, anti-cancer drugs ought to have anti-angiogenic potentiality along with their DNA damaging abilities. In this current piece of work, we investigated the in vitro and in ovo anti-angiogenic effect of Curcumin and Veliparib (a PARP inhibitor) in oral cancer. Recent evidences suggest an involvement of the NECTIN-4 in cancer angiogenesis and the exact molecular pathway of this involvement remains to be delineated. We observed that the soluble NECTIN-4 secreted from H357 oral cancer cells enhanced the angiogenesis of endothelial cells (HUVECs) and this was inhibited by Curcumin-Veliparib combination. NECTIN-4 enhanced vascularization, induced vasodilation and triggered the angiogenic sprouting via endothelial tip cell filopodia. Data indicated that NECTIN-4 mediated angiogenesis is associated with PI3K-AKT-mediated nitric oxide (NO) formation. A noticeable increase in the NO enhanced epithelial NO level through HIF-1α mediated iNOS activation. We observed that increased NO enhanced the NECTIN-4 mediated eNOS expression and thereby elicited further angiogenesis. Curcumin antagonised the NECTIN-4-induced angiogenesis through inhibition of PI3K-AKT mediated eNOS pathway and Veliparib synergized the effect of Curcumin. Our observations indicate that NO is cardinal in inducing NECTIN-4 mediated angiogenesis in H357 cells. Thus, Curcumin-Veliparib combination suppresses angiogenesis through deregulation of the PI3K-AKT-eNOS pathway downstream to the NECTIN-4.

Clinical significance of a pvrl 4 encoded gene Nectin-4 in metastasis and angiogenesis for tumor relapse.

PURPOSE: In the present study, we have systematically examined the clinical significance of Nectin-4 (encoded by the PVRL-4 gene), a marker for breast cancer stem cells (CSCs), in cancer metastasis and angiogenesis using a variety of human specimens, including invasive duct carcinoma (IDC) with multiple grades, several types of primary tumors to local and distant relapses, lymph node metastases and circulating tumor cells (CTCs). METHODS: Nectin-4 was overexpressed in more than 92% of samples with 65.2% Nectin-4-positive cells. The level of expression was increased with increasing tumor grade (GI-III) and size (T1-4) of IDC specimens. RESULTS: More induction of Nectin-4 was noted in relapsed samples from a variety of tumors (colon, tongue, liver, kidney, ovary, buccal mucosa) in comparison to primary tumors, while paired adjacent normal tissues do not express any Nectin-4. A high expression of Nectin-4 along with other representative markers in CTCs and lymph node metastasis was also observed in cancer specimens. An increased level of Nectin-4 along with representative metastatic (CD-44, Sca1, ALDH1, Nanog) and angiogenic (Ang-I, Ang-II, VEGF) markers were noted in metastatic tumors (local and distant) in comparison to primary tumors that were correlated with different grades of tumor progression. In addition, greater expression of Nectin-4 was observed in secondary tumors (distant metastasis, e.g., breast to liver or stomach to gall bladder) in comparison to primary tumors. CONCLUSION: Our study demonstrated a significant correlation between Nectin-4 expression and tumor grade as well as stages (p < 0.001), suggesting its association with tumor progression. Nectin-4 was overexpressed at all stages of metastasis and angiogenesis, thus appearing to play a major role in tumor relapse through the PI3K-Akt-NFκß pathway.

PARP inhibitor Olaparib Enhances the Apoptotic Potentiality of Curcumin by Increasing the DNA Damage in Oral Cancer Cells through Inhibition of BER Cascade.

Although Olaparib (Ola, a PARP-inhibitor), in combination with other chemotherapeutic agents, was clinically approved to treat prostate cancer, but cytotoxicity, off-target effects of DNA damaging agents limit its applications in clinic. To improve the anti-cancer activity and to study the detailed mechanism of anti-cancer action, here we have used bioactive compound curcumin (Cur) in combination with Ola. Incubation of Ola in Cur pre-treated cells synergistically increased the death of oral cancer cells at much lower concentrations than individual optimum dose and inhibited the topoisomerase activity. Short exposure of Cur caused DNA damage in cells, but more increased DNA damage was noticed when Ola has incubated in Cur pre-treated cells. This combination did not alter the major components of homologous recombination (HR) and non-homologous end-joining (NHEJ) pathways but significantly altered both short patch (SP) and long patch (LP) base excision repair (BER) components in cancer cells. Significant reduction in relative luciferase activity, expression of BER components and PARylation after Cur and Ola treatment confirmed this combination inhibit the BER activity in cells. Reduction of PARylation, decreased expression of BER components, decreased tumor volume and induction of apoptosis were also noticed in Cur + Ola treated Xenograft mice model. The combination treatment of Cur and Ola also helped in recovering the body weight of tumor-bearing mice. Thus, Cur + Ola combination increased the oral cancer cells death by not only causing the DNA damage but also blocking the induction of BER activity.

Comparative and Mechanistic Study on the Anticancer Activity of Quinacrine-Based Silver and Gold Hybrid Nanoparticles in Head and Neck Cancer.

Using oral cancer cells ( in vitro) and in vivo xenograft mice model, we have systematically studied the detailed mechanism of anticancer activity of quinacrine-based hybrid silver (QAgNP) and gold (QAuNP) nanoparticles (NPs) and compared their efficacies. Both the NPs showed characteristic anti-cell proliferation profile in various cancer cells with minimally affecting the normal nontransformed breast epithelial MCF-10A cells. The IC50 values of QAuNP in various cancer cells were less compared to QAgNP and also found to be the lowest (0.5 µg/mL) in SCC-9 oral cancer cells. Although both NPs caused apoptosis by increased DNA damage, arresting at S phase and simultaneously inhibiting the DNA repair activity in cells, efficacy of QAuNP was better than that of QAgNP. NPs intercalated with DNA and inhibited the topoisomerase activity in cells. Alteration in expression of cell cycle regulatory (cyclins B1, E1, A2, etc.) and replication-related (MRE11, RPA, RFC, etc.) proteins were also observed after NP exposure to the cells. Accumulation of cells resulted in extended G/M phase after prolonged exposure of QAuNP in SCC-9 cells. Interestingly, depletion of geminin and increase of Cdt-1 along with CDC-6 suggest the formation of re-replication. Recovery of body weight and reduction in tumor volume were found in NP-treated xenograft mice. Induction of Bax/Bcl-xL, PARP-1 cleavage, p53, and p21 were noted in NP-treated xenograft mice tissue samples. Thus, data suggest that NP inhibits topoisomerase activity, thereby inhibiting DNA replication and inducing re-replication, which causes S-phase arrest, DNA damage, and finally apoptosis of the oral cancer cells. Also, it was found that anticancer activity of QAuNP is better than that of QAgNP.

Seroprevalence of hepatitis B surface antigen and anti HCV antibody and its associated risk factors among pregnant women attending maternity ward of Felege Hiwot Referral Hospital, northwest Ethiopia: a cross-sectional study.

BACKGROUND: Viral hepatitis is a life-threatening liver disease that has become important public health issue in developing countries including Ethiopia. This study was undertaken to determine the seroprevalence of HBsAgs and anti-HCV antibodies and what socio-demographic factors are associated with sero-positivity of Hepatitis B Virus (HBV) and Hepatitis C Virus (HCV) infections among pregnant women attending maternity ward of Felege Hiwot Referral Hospital, northwest, Ethiopia. METHODS: Hospital based cross-sectional study was conducted from November 2013 to January 2014. Blood samples were randomly collected from 384 pregnant women. Data on socio-demographic characteristics, obstetric and potential risk factors were collected using semi-structured questionnaire. Chromatographic kits were used to detect the presence of HBsAg and antibodies against HCV in serum samples of the studied subjects. Chi-square test was used for assessing the association between socio-demographic variables and HBV and HCV status. Logistic regression analysis was done to determine the strength of association between risk factors and HBV or HCV infection. P-values less than 0.05 were considered as significant. RESULTS: Seroprevalnce of hepatitis B and C virus infections were found to be 4.4 and 0.26 %, respectively. None of the pregnant women were co-infected by these two viruses. Amongst the potential risk factors, previous history of dental procedure (AOR = 4.104, CI = 1.276-13.201, P = 0.018), house hold contact (AOR = 5.475, CI = 1.472-20.368, P = 0.011), multiple sexual exposure (AOR = 5.041, CI = 1.580-16.076, P = 0.006), and delivery at traditional birth attendants (AOR = 4.100, CI = 0.195-86.129, P = 0.024) were significantly associated with and important predictors of hepatitis B infection. CONCLUSIONS: This study found an intermediate endemicity (4.4 %) of HBV infection in pregnant women whereas seroprevalence of anti-HCV antibody was very small, but this needs to be confirmed by other similar studies with larger sample size. Thus, scaling up of the screening of pregnant women for HBV and HCV infections and provision of health education about the risk factors, the mode of transmissions and prevention is recommended.