Genome damage and their defective repair have been etiologically linked to degenerating neurons in many subtypes of amyotrophic lateral sclerosis (ALS) patients; however, the specific mechanisms remain enigmatic. The majority of sporadic ALS patients feature abnormalities in the transactivation response DNA-binding protein of 43 kDa (TDP-43), whose nucleo-cytoplasmic mislocalization is characteristically observed in spinal motor neurons. While emerging evidence suggests involvement of other RNA/DNA binding proteins, like FUS in DNA damage response (DDR), the role of TDP-43 in DDR has not been investigated. Here, we report that TDP-43 is a critical component of the nonhomologous end joining (NHEJ)-mediated DNA double-strand break (DSB) repair pathway. TDP-43 is rapidly recruited at DSB sites to stably interact with DDR and NHEJ factors, specifically acting as a scaffold for the recruitment of break-sealing XRCC4-DNA ligase 4 complex at DSB sites in induced pluripotent stem cell-derived motor neurons. shRNA or CRISPR/Cas9-mediated conditional depletion of TDP-43 markedly increases accumulation of genomic DSBs by impairing NHEJ repair, and thereby, sensitizing neurons to DSB stress. Finally, TDP-43 pathology strongly correlates with DSB repair defects, and damage accumulation in the neuronal genomes of sporadic ALS patients and inCaenorhabditis elegansmutant with TDP-1 loss-of-function. Our findings thus link TDP-43 pathology to impaired DSB repair and persistent DDR signaling in motor neuron disease, and suggest that DSB repair-targeted therapies may ameliorate TDP-43 toxicity-induced genome instability in motor neuron disease.

BackgroundRecent observations indicate potential role of transcription factor STAT3 in cervical cancer development but its role specifically with respect to HPV infection is not known. Present study has been designed to investigate expression and activation of STAT3 in cervical precancer and cancer in relation to HPV infection during cervical carcinogenesis. Established cervical cancer cell lines and prospectively-collected cervical precancer and cancer tissues were analyzed for the HPV positivity and evaluated for STAT3 expression and its phosphorylation by immunoblotting and immunohistochemistry whereas STAT3-specific DNA binding activity was examined by gel-shift assays.ResultsAnalysis of 120 tissues from cervical precancer and cancer lesions or from normal cervix revealed differentially high levels of constitutively active STAT3 in cervical precancer and cancer lesions, whereas it was absent in normal controls. Similarly, a high level of constitutively active STAT3 expression was observed in HPV-positive cervical cancer cell lines when compared to that of HPV-negative cells. Expression and activity of STAT3 were found to change as a function of severity of cervical lesions from precancer to cancer. Expression of active pSTAT3 was specifically high in cervical precancer and cancer lesions found positive for HPV16. Interestingly, site-specific accumulation of STAT3 was observed in basal and suprabasal layers of HPV16-positive early precancer lesions which is indicative of possible involvement of STAT3 in establishment of HPV infection. In HPV16-positive cases, STAT3 expression and activity were distinctively higher in poorly-differentiated lesions with advanced histopathological grades.ConclusionWe demonstrate that in the presence of HPV16, STAT3 is aberrantly-expressed and constitutively-activated in cervical cancer which increases as the lesion progresses thus indicating its potential role in progression of HPV16-mediated cervical carcinogenesis.

Seroprevalence of HBsAg in antenatal women was found to be 0.9%. HBe-antigen and HBV DNA positivity was associated with a higher chance of vertical transmission.

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Signal transducer and activator of transcription 3 (STAT3) is an oncogenic transcription factor constitutively active and aberrantly expressed in cervical cancer. However, the functional role of STAT3 in regulation of HPV's viral oncogene expression and downstream events associated with cervical carcinogenesis is not known. Our present study performed on HPV16-positive cervical cancer cell lines (SiHa and CaSki) and primary tumor tissues revealed a strong positive correlation of constitutively active STAT3 with expression of HPV16 E6 and E7 oncoproteins and a negative association with levels of p53 and pRB. Pharmacologic targeting of STAT3 expression in cervical cancer cell lines either by STAT3-specific siRNA or blocking its tyrosine phosphorylation by AG490 or curcumin led to dose-dependent accumulation of p53 and pRb in cervical cancer cells. Interestingly, the suppression of STAT3 expression or activation was associated with the gradual loss of HPV16 E6 and E7 expression and was accompanied by loss of cell viability. The viability loss was specifically high in HPV16-positive cells as compared to HPV negative C33a cells. These findings substantiate the regulatory role of STAT3 in HPV16-mediated cervical carcinogenesis. Leads obtained from the present study provide a strong rationale for developing novel STAT3-based approaches for therapeutic interventions against HPV infection to control cervical cancer.

Microhomology-mediated end joining (MMEJ), an error-prone pathway for DNA double-strand break (DSB) repair, is implicated in genomic rearrangement and oncogenic transformation; however, its contribution to repair of radiation-induced DSBs has not been characterized. We used recircularization of a linearized plasmid with 3΄-P-blocked termini, mimicking those at X-ray-induced strand breaks, to recapitulate DSB repair via MMEJ or nonhomologous end-joining (NHEJ). Sequence analysis of the circularized plasmids allowed measurement of relative activity of MMEJ versus NHEJ. While we predictably observed NHEJ to be the predominant pathway for DSB repair in our assay, MMEJ was significantly enhanced in preirradiated cells, independent of their radiation-induced arrest in the G2/M phase. MMEJ activation was dependent on XRCC1 phosphorylation by casein kinase 2 (CK2), enhancing XRCC1's interaction with the end resection enzymes MRE11 and CtIP. Both endonuclease and exonuclease activities of MRE11 were required for MMEJ, as has been observed for homology-directed DSB repair (HDR). Furthermore, the XRCC1 co-immunoprecipitate complex (IP) displayed MMEJ activity in vitro, which was significantly elevated after irradiation. Our studies thus suggest that radiation-mediated enhancement of MMEJ in cells surviving radiation therapy may contribute to their radioresistance and could be therapeutically targeted.

Aberrantly expressed survivin and STAT3 signaling have emerged as major determinants of chemoresistance in gastric cancer. We evaluated effects of potent herbal derivatives curcumin, berberine, and quercetin on STAT3 signaling, survivin expression, and response to 5-fluorouracil (5-FU) treatment in gastric cancer cells (AGS). Cytotoxic and inhibitory effects of berberine, curcumin, and quercetin alone or in combination with 5-FU were examined by MTT assay, and their effect on survivin, STAT3, and the phosphorylated active STAT3 (pSTAT3) expression was examined by western blotting. Effect of these herbal derivatives on STAT3 DNA binding activity was measured by electrophoretic mobility shift assay. Curcumin, berberine, and quercetin effectively downregulated pSTAT3 levels, survivin expression, and gastric cancer cells viability in a dose-dependent manner (with corresponding IC50 values of 40.3μM, 29.2μM and 37.5μM, respectively). Berberine was more effective in inhibiting survivin expression as compared to other herbal agents. 5-FU in combination with berberine or curcumin showed a synergistic inhibition of survivin and STAT3 level resulting in enhanced cell death in gastric cancer cells. Overall, our data suggest use of berberine and curcumin as adjunct therapeutics to overcome chemoresistance during treatment of gastric malignancies.

Background Bryophyllum pinnata ( B. pinnata ) is a common medicinal plant used in traditional medicine of India and of other countries for curing various infections, bowel diseases, healing wounds and other ailments. However, its anticancer properties are poorly defined. In view of broad spectrum therapeutic potential of B. pinnata we designed a study to examine anti-cancer and anti-Human Papillomavirus (HPV) activities in its leaf extracts and tried to isolate its active principle. Methods A chloroform extract derived from a bulk of botanically well-characterized pulverized B . pinnata leaves was separated using column chromatography with step- gradient of petroleum ether and ethyl acetate. Fractions were characterized for phyto-chemical compounds by TLC, HPTLC and NMR and Biological activity of the fractions were examined by MTT-based cell viability assay, Electrophoretic Mobility Shift Assay, Northern blotting and assay of apoptosis related proteins by immunoblotting in human cervical cancer cells. Results Results showed presence of growth inhibitory activity in the crude leaf extracts with IC 50 at 552 μg/ml which resolved to fraction F4 (Petroleum Ether: Ethyl Acetate:: 50:50) and showed IC 50 at 91 μg/ml. Investigations of anti-viral activity of the extract and its fraction revealed a specific anti-HPV activity on cervical cancer cells as evidenced by downregulation of constitutively active AP1 specific DNA binding activity and suppression of oncogenic c-Fos and c-Jun expression which was accompanied by inhibition of HPV18 transcription. In addition to inhibiting growth, fraction F4 strongly induced apoptosis as evidenced by an increased expression of the pro-apoptotic protein Bax, suppression of the anti-apoptotic molecules Bcl-2, and activation of caspase-3 and cleavage of PARP-1. Phytochemical analysis of fraction F4 by HPTLC and NMR indicated presence of activity that resembled Bryophyllin A. Conclusions Our study therefore demonstrates presence of anticancer and anti-HPV an activity in B . pinnata leaves that can be further exploited as a potential anticancer, anti-HPV therapeutic for treatment of HPV infection and cervical cancer.