Tau promotes oxidative stress-associated cycling neurons in S phase as a pro-survival mechanism: Possible implication for Alzheimer's disease

Multiple lines of evidence have linked oxidative stress, tau pathology and neuronal cell cycle re-activation to Alzheimer's disease (AD). While a prevailing idea is that oxidative stress-induced neuronal cell cycle reactivation acts as an upstream trigger for pathological tau phosphorylation, others have identified tau as an inducer of cell cycle abnormalities in both mitotic and postmitotic conditions. In addition, nuclear hypophosphorylated tau has been identified as a key player in the DNA damage response to oxidative stress. Whether and to what extent these observations are causally linked remains unclear. Using immunofluorescence, fluorescence-activated nucleus sorting and single-nucleus sequencing, we report an oxidative stress-associated accumulation of nuclear hypophosphorylated tau in a subpopulation of cycling neurons confined in S phase in AD brains, near amyloid plaques. Tau downregulation in murine neurons revealed an essential role for tau to promote cell cycle progression to S phase and prevent apoptosis in response to oxidative stress. Our results suggest that tau holds oxidative stress-associated cycling neurons in S phase to escape cell death. Together, this study proposes a tau-dependent protective effect of neuronal cell cycle reactivation in AD brains and challenges the current view that the neuronal cell cycle is an early mediator of tau pathology.

Revisiting the involvement of tau in complex neural network remodeling: analysis of the extracellular neuronal activity in organotypic brain slice co-cultures

Objective.Tau ablation has a protective effect in epilepsy due to inhibition of the hyperexcitability/hypersynchrony. Protection may also occur in transgenic models of Alzheimer's disease by reducing the epileptic activity and normalizing the excitation/inhibition imbalance. However, it is difficult to determine the exact functions of tau, because tau knockout (tau^KO) brain networks exhibit elusive phenotypes. In this study, we aimed to further explore the physiological role of tau using brain network remodeling.Approach.The effect of tau ablation was investigated in hippocampal-entorhinal slice co-cultures during network remodeling. We recorded the spontaneous extracellular neuronal activity over 2 weeks in single-slice cultures and co-cultures from control andtau^KOmice. We compared the burst activity and applied concepts and analytical tools intended for the analysis of the network synchrony and connectivity.Main results.Comparison of the control andtau^KOco-cultures revealed that tau ablation had an anti-synchrony effect on the hippocampal-entorhinal two-slice networks at late stages of culture, in line with the literature. Differences were also found between the single-slice and co-culture conditions, which indicated that tau ablation had differential effects at the sub-network scale. For instance, tau ablation was found to have an anti-synchrony effect on the co-cultured hippocampal slices throughout the culture, possibly due to a reduction in the excitation/inhibition ratio. Conversely, tau ablation led to increased synchrony in the entorhinal slices at early stages of the co-culture, possibly due to homogenization of the connectivity distribution.Significance.The new methodology presented here proved useful for investigating the role of tau in the remodeling of complex brain-derived neural networks. The results confirm previous findings and hypotheses concerning the effects of tau ablation on neural networks. Moreover, the results suggest, for the first time, that tau has multifaceted roles that vary in different brain sub-networks.

Extracellular vesicles: Major actors of heterogeneity in tau spreading among human tauopathies

Tauopathies are neurodegenerative diseases characterized by tau inclusions in brain cells. Seed-competent tau species have been suggested to spread from cell to cell in a stereotypical manner, indicating that this may involve a prion-like mechanism. Although the intercellular mechanisms of transfer are unclear, extracellular vesicles (EVs) could be potential shuttles. We assessed this in humans by preparing vesicles from fluids (brain-derived enriched EVs [BD-EVs]). These latter were isolated from different brain regions in various tauopathies, and their seeding potential was assessed in vitro and in vivo. We observed considerable heterogeneity among tauopathies and brain regions. The most striking evidence was coming mainly from Alzheimer's disease where the BD-EVs clearly contain pathological species that can induce tau lesions in vivo. The results support the hypothesis that BD-EVs participate in the prion-like propagation of tau pathology among tauopathies, and there may be implications for diagnostic and therapeutic strategies.

A randomized phase II study of concomitant CT (docetaxel±cisplatin) and (RT) in first-line treatment of locally advanced head and neck cancer (LAHNC)

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Background: 4 randomized trials demonstrated superiority of concomitant CT and radiotherapy (CRT) versus RT. Radiosensitizing effect of docetaxel showed in vitro, phase I recommended docetaxel dose as weekly 20 mg/m2 with concomitant RT. Methods: (pts) with inoperable LAHNC (T3/T4); PS < 2.RT in both arms was 70 Gy. In arm A, pts received 7 cycles of weekly Docetaxel 20 mg/m2 before RT and cisplatin 20 mg/m2 D1–3 every three weeks (3 cycles). In arm B, docetaxel alone at the same dose as in arm A.G-CSF secondary prophylaxis and ciprofloxacin recommended in both arms. Primary objective was WHO objective response rate (ORR). Statistical analysis: 2 steps according to a Simon plan authorized early interruption in case of insufficient efficacy. Results: 82 pts treated (Arms A/B:35/47); Arm A stopped in the first step. 47 pts treated in arm B. M/F (%) (83/17), median age 56.6 y, PS 0/1 (%) 54/46, T2/T3/T4 (%) 2/36/62, N0–1/N2/N3 (%) 30/55/15, primary site (%): buccal cavity (38), hypo-oropharynx (47), larynx (11). Median nbr of cycles 7 (3–7), 85% of pts completed planned CRT. ITT ORR: 89 % [75–96], median TTP 31.3 [19.3 –42.4], median OS 36.8 [21.2–49.5] months. Main grade 3–4 toxicities were mucositis (31.9%),skin toxicity (21.3%). Grade 3–4 hematological, GI and neurological toxicities were not observed. Conclusions: In this study, concomitant RT and weekly 20 mg/m2 docetaxel is effective and well tolerated in LAHNC. The docetaxel/cisplatin arm was prematurely discontinued for insufficient efficacy.

No significant financial relationships to disclose.

Impact of organization of colorectal cancer screening: Results of EDIFICE study

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Background: The EDIFICE study aimed to allow better understanding of population’s adhesion to the tests available for the 4 most frequent cancers: breast, colorectal, prostate and lung. In 1998 the French National Consensus Conference advocated for mass cancer screening (CS) using Hemoccult II. The departments are divided according to the existence or not of an organized program: this screening was organized in 22 departments (3 “scout” started in 1998, 9 “first wave” in 2003 and 12 “second wave” in 2004). Results are reported hereunder. Methods: This first nationwide observational study was carried out in France from January 18th to February 2nd, 2005 among a representative sample of 1504 subjects aged between 40 and 75 years and a representative sample of 600 general practitioners (GPs). Information about participating subjects included socio-demographic characteristics, attitude towards CS, and about GPs’ medical practice regarding CS. Results: Only 25% of the 970 subjects aged between 50 and 74 years had undergone a colorectal screening test. In the organized departments (OD), the rate of persons who self-report any colorectal cancer screening was 34% vs 20% in unorganized departments (UD) (OR=1.99, CI95% 1.47- 2.69, p<0.001). The rate of recent screening within a range of 2 years was 24% for OD vs 8% for UD (OR=3.35, CI95% 1.91- 5.88, p<0.01). The rate of “fear of the test and/or its results” was higher in OD: 11% versus 6% (OR=1.97, CI95% 1.11–3.49). The rate of GPs who advocated systematically for screening was 40%, 29%, 26% and 13% for scout, first wave, second wave OD and baseline UD respectively. Organization reduced the rate of screening based on colonoscopy alone from 69% persons in UD to 35% in the OD. Conclusions: The main result of this survey comparing data in the same frame of time, in the same country, is that organized programs for colorectal cancer impact of health outcomes.

No significant financial relationships to disclose.

Vinorelbine and ifosfamide for unresectable non-small cell lung cancer

PURPOSE

The study assessed the efficacy of combination therapy with vinorelbine and ifosfamide in patients with unresectable non-small cell lung cancer.

PATIENTS AND METHODS

Forty patients with non-small cell lung cancer whose tumour was unresectable by virtue of the extent of disease or severity of impairment of lung function and who were considered unsuitable for treatment with a cisplatin based treatment were entered onto the study. Thirty-four patients received two cycles of treatment and were considered to be evaluable for response. The treatment schedule consisted of vinorelbine (Navelbine, Pierre Fabre Medicament) 25 mg/m2 on days 1 and 8, and ifosfamide 2 g/m2 per day with mesna 0.5 g/m2 three times daily given on days 1 to 3; cycles were repeated every 21 days and treatment continued in responding patients until progression occurred.

RESULTS

Objective responses were observed in 12 patients (30%; CI95, 16-44) with one completed response (CR) and 11 partial response (PR).

CONCLUSION

This schedule achieves good levels of response without the use of cisplatin so it is suitable for patients whose performance status or concomitant medical condition precludes the use of platinum based chemotherapy.

[Treatment of advanced kidney cancer using recombinant erythropoietin]

OBJECTIVES

Study of the antitumour effects of erythropoietin on metastatic renal cell carcinoma.

METHODS

After giving their informed consent, 20 patients with histologically proven metastatic renal cell carcinoma received subcutaneous recombinant erythropoietin three times a day at a dose of 150 IU/kg when haemoglobin was less than or equal to 12 g/dL or 75 IU/kg when haemoglobin was higher than 12 g/dL. Treatment was continued for a minimum of 8 weeks before reassessment and was continued thereafter, except in the case of progression or excessive toxicity. A staging assessment was performed every 8 weeks and the response was assessed on the basis of WHO criteria. A clinical and laboratory assessment was performed every two months to evaluate toxicity, graded according to the WHO scale. All but one of the patients had received immunotherapy or chemotherapy prior to inclusion in the study.

RESULTS

One complete response (> 12 months), one partial response (8 months), two minor responses, 10 cases of stabilisation and 6 cases of progression were observed. 15 patients received treatment at full doses. In 5 patients, the duration of treatment was reduced before the 8 weeks initially defined because of tumour progression in one patient and because of haemoglobin persistently greater than 15 g/dL in 4 other patients. Adverse effects consisted of 1 case of moderate headache, 2 cases of transient bone pain, and 1 case of transient hypertension.

CONCLUSION

Erythropoietin exerts a moderate antitumour effect which needs to be confirmed by a phase II trial of first-line treatment in selected patients.

[Induction chemotherapy followed by concomitant combined radiotherapy and chemotherapy in stage III non-small cell bronchial carcinoma]

PURPOSE

To determine the efficacy and safety of induction chemotherapy followed by concomitant chemoradiotherapy in the treatment of stage III non-small cell lung cancer and whether the response to induction chemotherapy can predict the response to subsequent chemoradiotherapy and survival.

MATERIALS AND METHODS

Between December 1987 and June 1993, 46 patients with previously untreated stage III non-small cell lung cancer received every 21 days induction chemotherapy (ICT) including three cycles of 5-fluorouracil (600 mg/m2/d in short infusion from d1 to d5), cisplatin (15 mg/m2/d from d1 to d5), etoposide (50 mg/m2/d from d1 to d5) and hydroxyurea (1,500 mg/d from d1 to d5). The first 21 patients also received bleomycin (3 mg/m2/d from d1 to d5). All patients received concomitant chemotherapy and had chest radiotherapy (CCRT). Patients received irradiation (65 Gy/33-6 fractions/7 weeks) on d25 after the third cycle of chemotherapy. Concomitant chemotherapy was composed of cisplatin (20 mg/m2) and 5-fluorouracil (500 mg/m2) that were administered each Monday and Thursday during radiotherapy. Maintenance chemotherapy consisted of thiotepa (10 mg/m2) and methotrexate (10 mg/m2) that were administered every 2 weeks for 6 months.

RESULTS

Pulmonary toxicity was observed in four out of 21 patients who had received bleomycin and subsequently developed pulmonary fibrosis, leading to death for two of them. ICT alone produced five complete responses (11%) and 13 partial responses (28%). The combination of chemotherapy and radiotherapy led to 19 complete responses (41%) and 14 partial responses (30%). Eighteen of the 18 responders (100%) to ICT responded to subsequent CCRT, of whom 13 (72%) became complete responders. Fifteen of the 28 non-responders to ICT (53%) responded to CCRT, six of them being complete responders (21%) (P < 0.001). The median overall survival rate was 17 months when considering all patients, 25 months in patients responding to ICT and 13 months in non-responders. The 2-year survival rates were 28, 55 and 11%, respectively (P < 0.05). ICT did not influence the rate of subsequent metastatic events. However, locoregional reprogression was lower in responders to ICT. The number of metastatic events was not significantly related to response to ICT. By contrast, the rate of local failure was higher when there was resistance to ICT (75% versus 39%). Out of the 19 complete responders to CCRT (13 responders to ICT and six non-responders to ICT), four developed secondary locoregional reprogression (21%) and six developed metastatic disease (31%). In complete responders to CCRT, the rate of locoregional failure was 15% in responders to ICT (2/13) and 33% (2/6) in non-responders to ICT. Four out of the 13 responders to CCRT after response to ICT (31%) and two out of the six complete responders to CCRT developed metastatic disease after non-response to ICT.

CONCLUSION

There is a statistically significant relationship not only between the response to ICT and the response to CCRT, but also between the response to ICT and the local outcome and survival.