SIRT2 regulates tumour hypoxia response by promoting HIF-1α hydroxylation

Hypoxia-inducible factor-1α (HIF-1α) is a transcription factor that has a central role in the regulation of tumour metabolism under hypoxic conditions. HIF-1α stimulates glycolytic energy production and promotes tumour growth. Sirtuins are NAD(+)-dependent protein deacetylases that regulate cellular metabolism in response to stress; however, their involvement in the hypoxic response remains unclear. In this study, it is shown that SIRT2-mediated deacetylation of HIF-1α regulates its stability in tumour cells. SIRT2 overexpression destabilized HIF-1α under hypoxic conditions, whereas HIF-1α protein levels were high in SIRT2-deficient cells. SIRT2 directly interacted with HIF-1α and deacetylated Lys709 of HIF-1α. Deacetylation of HIF-1α by SIRT2 resulted in increased binding affinity for prolyl hydroxylase 2, a key regulator of HIF-1α stability, and increased HIF-1α hydroxylation and ubiquitination. Moreover, a pharmacological agent that increased the intracellular NAD(+)/NADH ratio led to the degradation of HIF-1α by increasing SIRT2-mediated deacetylation and subsequent hydroxylation. These findings suggest that SIRT2-mediated HIF-1α deacetylation is critical for the destablization of HIF-1α and the hypoxic response of tumour cells.

Simplified staging laparotomy in FIGO stage 1 epithelial ovarian cancer: follow-up and outcomes in south Wales, U.K

We have conducted a retrospective analysis of FIGO stage 1 ovarian cancer patients in south Wales, who underwent a simplified staging laparotomy without routine nodal sampling and peritoneal biopsies. Patient records from January 2004 to December 2010 were analysed. A total of 116 patients were included in the final analysis. Adjuvant chemotherapy was offered to patients with risk factors for relapse (grade > 1, clear cell histology, or stage > Ia); overall, 89 patients (76.7%) received adjuvant single agent carboplatin (n = 54, 46.5%) or combination chemotherapy (n = 35, 30.2%). After a median follow up of 41 months (range 12-95), 18 patients have relapsed (15.5%), of these 17 had risk factors and 16 had received adjuvant chemotherapy. Eighteen patients have died, of whom 6 of non-cancer related causes without prior relapse. 5-year overall and relapse free survival were 80%. In conclusion, in situations where there are limited resources and operating time constraints, our data suggest that a simplified staging laparotomy approach may be a reasonable compromise in apparently early stage ovarian cancer: this may result in a more aggressive use of chemotherapy, but survival outcomes seem comparable to other series.

Increase in Salmonella enterica serovar Paratyphi A infections in Phnom Penh, Cambodia, January 2011 to August 2013

We report an increased number of Salmonella enterica Paratyphi A infections in adults in Cambodia. Between January 2011 and August 2013, 71 S. Paratyphi A isolates were recovered from blood cultures, representing a 44-fold increase compared to July 2007 to December 2010, while monthly numbers of cultures did not change. Infections with S. Typhi increased two-fold in the same period. Most cases came from the capital Phnom Penh. These findings warrant epidemiological investigation to support public health measures.

Resolution of adefovir-related nephrotoxicity by adefovir dose-reduction in patients with chronic hepatitis B

BACKGROUND

Chronic hepatitis B patients (CHB) treated with adefovir were followed up to evaluate nephrotoxicity and its outcome.

AIM

To assess the incidence of renal dysfunction during adefovir therapy in Asian patients and factors associated with it, and evaluate strategies to improve adefovir-related renal dysfunction and their impact on viral suppression.

METHODS

Chronic hepatitis B clinic patients from a tertiary hospital on adefovir treatment, with their clinical and laboratory parameters were extracted from the hospital electronic clinical database in an observational study design. Patients were excluded if they had liver/renal transplant, baseline renal impairment or were on dialysis. Adefovir-related renal dysfunction was defined as adefovir-related abnormal serum creatinine (ARASC) > 125 μmol/L (males), >90 μmol/L (females); adefovir-related abnormal GFR <60 mL/min; and adefovir-related increased serum creatinine >0.5 mg/dL, without other known causes of nephrotoxicity.

RESULTS

A total of 271/383 adefovir-treated patients were suitable for analysis and 33(12%) patients developed abnormal serum creatinine. Cumulative increase in proportion of patients with ARASC was 33.8% and GFR ≤60 mL/min was 38.3% by 6 years, while serum creatinine increase ≥0.5 mg/dL was 21.48% by 5 years. Using multivariate analysis, the only independent baseline predictor of ARASC was GFR ≤76.1 mL/min. Patients who had ARASC had similar levels of viral suppression to those who did not have ARASC. Those who had ARASC either continued adefovir (24%), switched therapy (24%) or had adefovir dose reduction (52%). ARASC resolved and GFR normalised in almost all patients after either switching therapy or reducing adefovir dose, with no difference between the two strategies (P = 0.737). Those with adefovir dose reduction had no significant increase in HBV DNA (P = 0.170).

CONCLUSIONS

Adefovir-related renal dysfunction occurred in a significant number of adefovir-treated patients, but reduction of the dose led to renal improvement without compromising treatment efficacy.

Lupus nephritis: a 15-year multi-centre experience in the UK

OBJECTIVES

Our aim was to audit the outcome of lupus nephritis (LN) at three East Midlands centres.

METHODS

We undertook a retrospective review of all biopsy-proven LN types III-V 1995-2010.

RESULTS

In total, 61 patients with LN were identified, with a median follow-up of 68 months. LN was present at the time of systemic lupus erythematosus (SLE) diagnosis in 20 patients. The median time from SLE diagnosis to the first LN episode was 5.3 years. Some 35 patients received IV cyclophosphamide and 17 received mycophenolate mofetil (MMF) as induction therapy; 81.8% of those treated with cyclophosphamide and 81.3% with MMF had at least 'improved' according to the ACR-response criteria 6 months from induction; 33.3% and 37.5%, respectively, had a 'complete' response. MMF and azathioprine were the most frequently used maintenance therapy. We found that 32.8% experienced a flare after a mean post-induction time of 3.5 years, irrespective of the maintenance therapy used, and 43.8% of partial responders flared compared with 4.8% of complete responders. End-stage renal failure developed in 8.2%.

CONCLUSIONS

Overall, outcomes (response, flare-rate, end-stage renal failure) were comparable with European clinical studies. Partial responders are more likely to flare compared with complete responders. The results highlight that LN can occur, and flare, after many years of SLE, emphasizing the importance of continued vigilance for LN in all patients.

Abstract P5-20-07: Phase II Trial of Dasatinib in Combination With Weekly Paclitaxel for Patients with Metastatic Breast Carcinoma

Background: Src kinase plays an important role in proliferation, survival, angiogenesis and metastasis in several malignancies including breast cancer. Therefore, inhibition of Src and other tyrosine kinases (TKs) represents a novel therapeutic approach. Dasatinib is a potent inhibitor of 5 oncogenic TKs, inhibits VEGF-stimulated proliferation, has potent bone anti-resorptive activity and selectively inhibits basal-type breast cancer growth. Preclinically, the combination of dasatinib and paclitaxel had superior antitumor activity to either agent alone. In a previous phase I study, we determined that, in combination with weekly paclitaxel, the optimum dose of dasatinib was 120mg. Of note, 4/9 (44%) patients treated at or above this dasatinib dose level had objective tumor response. We now present results from the phase II trial of this combination.

Methods: Patients with MBC, ECOG PS 0–1, normal hepatic, renal, marrow function were eligible. Patients had measurable, HER2-negative metastatic breast cancer (MBC), ≤2 prior therapies for MBC. Treatment consisted of weekly paclitaxel 80 mg/m2 IV 3/4 weeks + Dasatinib 120mg orally daily. Response was assessed by RECIST after every 8 weeks of therapy. Simon's two-stage optimal design was used to test the null hypothesis of a 15% response rate (RR) against the alternative of a 30% RR. In stage I, planned enrollment was 23 patients based on Type I and Type II errors of 10%. If 4 or more responses are observed, enrollment will be extended to 55 patients. Exploratory correlative biomarkers of clinical benefit include Src phosphorylation (p-Src) in peripheral blood mononuclear cells, plasma levels of VEGFR2 and collagen Type IV, circulating tumor cells (CTCs) and tumor gene expression profiling.

Results: 21 patients (19 females, 2 male) have enrolled; median age 48 (range 30–79). Patients received a median of 1 prior therapy for MBC (range 0–2). 6 patients are not assessable for response: 1 has received &lt;8 weeks treatment, 5 came off study for toxicity (2 hypersensitivity reaction to paclitaxel, 1 infection, 1 diarrhea/nausea, 1 bleeding likely related to anticoagulation). Among the 15 patients assessable for response, best response to date is as follows: 2 (13%) patients partial response, 11 (73%) patients stable disease (SD) and 2 (13%) patients progression of disease. Of patients with SD, 6/11 (55%) continue on treatment after median of 2 months (range 2–10) and 5/11 (45%) patients have come off study after median of 10 months (range 3–21). Most toxicities have been hematological and low grade. Diarrhea and neuropathy have generally been low grade and no new toxicities related to the combination have occurred since expansion into the phase II. Potential biomarkers of clinical benefit including, p-Src, VEGFR2, collagen Type IV, and CTCs will be presented.

Conclusion: Data from this phase II has demonstrated preliminary evidence of activity for weekly paclitaxel and dasatinib 120mg in patients with MBC. These findings are consistent with data from this dose level in the earlier phase I study. Predictive biomarkers of clinical benefit are under investigation.

Citation Information: Cancer Res 2012;72(24 Suppl):Abstract nr P5-20-07.