Inhibition of DNA2 nuclease as a therapeutic strategy targeting replication stress in cancer cells

Replication stress is a characteristic feature of cancer cells, which is resulted from sustained proliferative signaling induced by activation of oncogenes or loss of tumor suppressors. In cancer cells, oncogene-induced replication stress manifests as replication-associated lesions, predominantly double-strand DNA breaks (DSBs). An essential mechanism utilized by cells to repair replication-associated DSBs is homologous recombination (HR). In order to overcome replication stress and survive, cancer cells often require enhanced HR repair capacity. Therefore, the key link between HR repair and cellular tolerance to replication-associated DSBs provides us with a mechanistic rationale for exploiting synthetic lethality between HR repair inhibition and replication stress. DNA2 nuclease is an evolutionarily conserved essential enzyme in replication and HR repair. Here we demonstrate that DNA2 is overexpressed in pancreatic cancers, one of the deadliest and more aggressive forms of human cancers, where mutations in the KRAS are present in 90–95% of cases. In addition, depletion of DNA2 significantly reduces pancreatic cancer cell survival and xenograft tumor growth, suggesting the therapeutic potential of DNA2 inhibition. Finally, we develop a robust high-throughput biochemistry assay to screen for inhibitors of the DNA2 nuclease activity. The top inhibitors were shown to be efficacious against both yeast Dna2 and human DNA2. Treatment of cancer cells with DNA2 inhibitors recapitulates phenotypes observed upon DNA2 depletion, including decreased DNA double strand break end resection and attenuation of HR repair. Similar to genetic ablation of DNA2, chemical inhibition of DNA2 selectively attenuates the growth of various cancer cells with oncogene-induced replication stress. Taken together, our findings open a new avenue to develop a new class of anticancer drugs by targeting druggable nuclease DNA2. We propose DNA2 inhibition as new strategy in cancer therapy by targeting replication stress, a molecular property of cancer cells that is acquired as a result of oncogene activation instead of targeting currently undruggable oncoprotein itself such as KRAS.

Anthropometric and biomechanical characteristics of body segments in persons with spinal cord injury

People with spinal cord injury (SCI) experience bone and muscle loss in their paralyzed limbs that is most rapid and severe in the first 3years after injury. Restoration of mechanical loading through therapeutic physical activity may potentially slow or reverse post-SCI bone loss, however, therapeutic targets cannot be developed without accurate biomechanical models. Obesity is prevalent among SCI population, and it alters body composition and further affects parameters of these models. Here, clinical whole body dual-energy X-ray absorptiometry data from people with acute (n=39) and chronic (n=61) SCI were analyzed to obtain anthropometric parameters including segment masses, center of mass location, and radius of gyration for both obese and non-obese individuals. Chronic SCI was associated with higher normalized trunk mass of 3.2%BW and smaller normalized leg mass of 1.8%BW in males, but no significant changes in segment centers of mass or radius of gyration. People with chronic SCI had 58.6% lean mass in the trunk, compared to 66.6% lean mass in those with acute SCI (p=0.01), with significant changes in all segments. Obesity was associated with an increase in trunk mass proportion of 3.1%BW, proximal shifts in thigh and upper arm center of mass, and changes to thigh and shank radius of gyration. The data presented here can be used to accurately represent the anthropometrics of SCI population in biomechanical studies, considering obesity and injury duration.

Wheelchair use and lipophilic statin medications may influence bone loss in chronic spinal cord injury: findings from the FRASCI-bone loss study

We identified a protective bone effect at the knee with lipophilic statin use in individuals with chronic spinal cord injury. Lipophilic statin users gained bone at the knee compared to non-users and wheelchair users lost bone compared to walkers. Ambulation and or statins may be effective osteogenic interventions in chronic spinal cord injury (SCI).

INTRODUCTION

SCI increases the risk of osteoporosis and low-impact fractures, particularly at the knee. However, during the chronic phase of SCI, the natural history and factors associated with longitudinal change in bone density remain poorly characterized. In this study, we prospectively assessed factors associated with change in bone density over a mean of 21 months in 152 men and women with chronic SCI.

METHODS

A mixed model procedure with repeated measures was used to assess predictors of change in bone mineral density (PROC MIXED) at the distal femur and proximal tibia. Factors with a p value of <0.10 in the univariate mixed models, as well as factors that were deemed clinically significant (gender, age, and walking status), were assessed in multivariable models. Factors with a p value of ≤0.05 were included in the final model.

RESULTS

We found no association between bone loss and traditional osteoporosis risk factors, including age, gender, body composition, or vitamin D level or status (normal or deficient). In both crude and fully adjusted models, wheelchair users lost bone compared to walkers. Similarly, statin users gained bone compared to nonusers.

CONCLUSIONS

The statin finding is supported by reports in the general population where statin use has been associated with a reduction in bone loss and fracture risk. Our results suggest that both walking and statins may be effective osteogenic therapies to mitigate bone loss and prevent osteoporosis in chronic SCI. Our findings also suggest that loss of mechanical loading and/or neuronal factors contribute more to disuse osteoporosis than traditional osteoporosis risk factors.

Hepatitis C-specific effector and regulatory CD4 T-cell responses are associated with the outcomes of primary infection

Clearance of primary hepatitis C virus (HCV) infection has been associated with strong and broadly targeted cellular immune responses. This study aimed to characterize HCV-specific CD4+ effector and regulatory T-cell numbers and cytokine production during primary infection. Antigen-specific CD4+ T-cell responses were investigated in a longitudinal cohort of subjects from pre-infection to postoutcome, including subjects who cleared [n=12] or became chronically infected [n=17]. A cross-sectional cohort with previously cleared, or chronic infection [n=15 for each], was also studied. Peripheral blood mononuclear cells were incubated with HCV antigens and surface stained for T-effector (CD4+CD25^high CD134+CD39-) and T-regulatory (CD4+CD25^high CD134+CD39+) markers, and culture supernatants assayed for cytokine production. Contrary to expectations, the breadth and magnitude of the HCV-specific CD4+ T-cell responses were higher in subjects who became chronically infected. Subjects who cleared the virus had HCV-specific CD4+ T-cell responses dominated by effector T cells and produced higher levels of IFN-γ, in contrast to HCV-specific CD4+ T-cell responses dominated by regulatory T cells and more IL-10 production in those who became chronically infected. Better understanding of the role of antigen-specific CD4+ T-cell responses in primary HCV will further define pathogenesis and help guide development of a preventative vaccine.

Reduction of chronic hepatitis B-related hepatocellular carcinoma with anti-viral therapy, including low risk patients

BACKGROUND

Anti-viral therapy in chronic hepatitis B (CHB) is associated with a reduced risk of hepatocellular carcinoma (HCC) primary described in patients with cirrhosis.

AIM

To examine the effects of treatment on HCC incidence in CHB with and without cirrhosis, after adjustment for background risks.

METHODS

A total of 2255 CHB patients from a US cohort (973 received anti-viral therapy) and 3653 patients from the community-based Taiwanese REVEAL-HBV study, none of whom received treatment. We used Cox proportional hazard models to calculate the risk of developing HCC after adjustment with the previously validated REACH-B risk score.

RESULTS

We found 273 incident cases of HCC. After adjustment, therapy lowered the risk of HCC development in the US treated cohort when compared to the US untreated cohort (HR 0.31; 95% CI: 0.15-0.66; P = 0.002). HCC risk reduction was also confirmed when compared to the REVEAL cohort (HR 0.22; 95% CI: 0.12-0.40; P < 0.001). Each REACH-B point was associated with a 53% increased risk of HCC (HR 1.53; 95% CI 1.46-1.59; P < 0.001). We found a significant statistical reduction in HCC incidence with therapy regardless of gender, age, cirrhosis status, HBeAg serology, alanine aminotransferase level, REACH-B score or treatment medication. Therapy was beneficial to those with mildly- to moderately elevated HBV DNA levels (>2000 IU/mL) and of even greater benefit to those with levels >200 000 IU/mL.

CONCLUSION

After adjustment for background risk, anti-viral therapy was associated with a significant reduction in HCC incidence in both community and real-life clinical cohorts, including in those patients previously thought to be at low risk.

Antiphospholipid antibodies in primary Sjögren’s syndrome: prevalence and clinical significance in a series of 74 patients

The aim of this study is to determine prevalence, clinical significance of antiphospholipidantibodies (aPL) including anticardiolipin antibodies (aCL), anti-b2GP1 and lupus anticoagulant (LA) in a cohort of 74 patients with primary Sjögren’s syndrome (pSS) according to revised European criteria. aPL were found in 25 (34%) patients; IgG in 23 (12 had low titres, six moderate titres and five high titres) and IgM in five (three and two had respectively moderate and high titres). Eight (11%) patients were found to have LA; anti-b2GP1 antibodies were detected only in three (4%) patients. Only two patients with LA, aPL and b2GP1 had recurrent venous thrombosis. One patient with moderate titres of aPL exhibited recurrent spontaneous foetal losses. Peripheral neuropathies without cryoglobulinemia were more frequent in the aPL group. Other systemic involvements of pSS were the same in both groups with or without aPL. Patients with aPL have more concurrentimmunological diseases such as thyroiditis and primary biliary cirrhosis and a higher prevalence of hypergammaglobulinemia (P < 0.05). Even if aPL prevalence reached 30% in pSS, titres were usually low, with a close correlation with hypergammaglobulinemia but not with antiphospholipid syndrome, which is related to positivity of both LA and aPL.

Durability of Hepatitis B e Antigen Seroconversion in Chronic Hepatitis B Patients Treated with Entecavir or Tenofovir

INTRODUCTION

Loss of HBeAg and development of anti-HBe (seroconversion) is seen as a milestone and endpoint in the treatment of HBeAg-positive patients with chronic hepatitis B (CHB). Among patients treated with nucleos(t)ide analogs (NA), recurrent viremia is common after discontinuation of therapy. Entecavir (ETV) and tenofovir (TDF) are highly potent NA. The durability of virological response and HBeAg seroconversion in patients treated with these agents is not well studied.

METHODS

We retrospectively studied the outcomes of 54 HBeAg-positive CHB patients who were treated with either ETV (n = 30) or TDF (23) or both (n = 1) that achieved virological response and underwent seroconversion and consolidation therapy before cessation of treatment.

RESULTS

Only 4 (7%) patients had sustained virological, serological, and biochemical remission. Thirteen patients (24%) continued to have HBV DNA levels below 2000 IU/mL and normal alanine aminotransferase activity (ALT). Thirty-seven patients (69%) developed HBV DNA >2000 IU/mL, with 20 having elevated ALT. Among these 37 patients, 23 (62%) remained HBeAg negative/anti-HBe positive, 12 (32%) became HBeAg positive, and 2 (5%) were HBeAg and anti-HBe negative. Duration of consolidation therapy did not correlate with low versus high level of virological relapse.

CONCLUSIONS

Durability of HBeAg seroconversion associated with ETV or TDF was not superior to that reported in patients treated with less potent NA. Our results, aggregated with others, suggest HBeAg seroconversion should not be considered as a treatment endpoint for most HBeAg-positive patients treated with NA. Future updates of treatment guidelines should reconsider HBeAg seroconversion as an endpoint to therapy.

Dysregulated protease activated receptor 1 (PAR1) promotes metastatic phenotype in breast cancer through HMGA2

As the majority of patients with basal-like breast carcinoma present with invasive, metastatic disease that do not respond to available therapies, it is essential to identify new therapeutic targets that impact invasion and metastasis. Protease-activated receptor 1 (PAR1), a G-protein coupled receptor has been shown to act as an oncogene, but underlying mechanisms are not well understood. Here, we show that ectopic expression of functionally active PAR1 in MCF-7 cells induced a hormone-refractory, invasive phenotype representative of advanced basal-like breast carcinoma that readily formed metastatic lesions in lungs of mice. PAR1 was found to globally upregulate mesenchymal markers, including vimentin, a direct target of PAR1, and downregulate the epithelial markers including E-cadherin, as well as estrogen receptor. In contrast, non-signaling PAR1 mutant receptor did not lead to an invasive, hormone refractory phenotype. PAR1 expression increased spheroid formation and the level of stemness markers and self-renewal capacity in human breast cancer cells. We identified HMGA2 (high mobility group A2) as an important regulator of PAR1-mediated invasion. Inhibition of PAR1 signaling suppresses HMGA2-driven invasion in breast cancer cells. HMGA2 gene and protein are highly expressed in metastatic breast cancer cells. Overall, our results show that PAR1/HMGA2 pathway may present a novel therapeutic target.

All-fiber bidirectional optical parametric oscillator for precision sensing

We present the design and operation of an all-fiber, synchronously pumped, bidirectional optical parametric oscillator (OPO) for precision sensing applications. The fiber-based OPO (FOPO) generates two frequency combs with identical repetition rates but different carrier offset frequencies. A narrow beatnote was observed with full-width at half-maximum (FWHM) linewidth of <10  Hz when the two frequency combs were overlapped on a photodetector. The all-fiber design removes the need for free-space alignment and adjustment. In addition, an external delay line to overlap the two pulse trains in time on the detector is not needed since our unique design provides automatic delay compensation. We expect the novel FOPO to find important applications in precision measurements including rotation sensing with ultra-large sensing area and sensitivity.