Competition between Na⁺ and Rb⁺ in the minor groove of DNA

The competition between Na⁺ and Rb⁺ ions in the minor groove of a synthetic B-DNA dodecamer d (CGCGAATTCGCG) is studied using molecular dynamics simulations as the ratio of these two ions changing from 9:1 to 1:9 with the DNA merged into the solvent of water molecule at 298 K. When the concentration of Rb⁺ ions increases, from minority to majority, Na⁺ ions are gradually released from the A tract, and the binding sites in the minor groove are occupied by Rb⁺ ions, extending from the A tract to the whole minor groove. Comparing Na⁺ with Rb⁺ ions, the conformation of the minor groove is influenced strongly by Na⁺ ions.

Effects of various salinities on Na(+)-K(+)-ATPase, Hsp70 and Hsp90 expression profiles in juvenile mitten crabs, Eriocheir sinensis

Eriocheir sinensis is a euryhaline crab migrating from sea to freshwater habitats during the juvenile stage. We used quantitative real-time polymerase chain reaction (qRT-PCR) to investigate the gene expression profile of Na(+)-K(+)-ATPase, Hsp70 (heat shock protein 70) and Hsp90 in megalopa exposed to salinities of 0, 2, 5, 10, and 15 parts per thousand. Both low and high salinities markedly stimulated expression of Na(+)-K(+)-ATPase, Hsp70 and Hsp90 genes of Chinese mitten crab megalopa; salinity had different effects on Na(+)-K(+)-ATPase, Hsp70 and Hsp90 levels depending on the duration of salinity stress, implying that Na(+)-K(+)-ATPase, Hsp70 and Hsp90 may play an important role in salinity tolerance in this crab species.

Tensile plasticity in metallic glasses with pronounced β relaxations

Metallic glasses are commonly brittle, as they generally fail catastrophically under uniaxial tension. Here we show pronounced macroscopic tensile plasticity achieved in a La-based metallic glass which possesses strong β relaxations and nanoscale heterogeneous structures. We demonstrate that the β relaxation is closely correlated with the activation of the structural units of plastic deformations and global plasticity, and the transition from brittle to ductile in tension and the activation of the β relaxations follow a similar time-temperature scaling relationship. The results have implications for understanding the mechanisms of plastic deformation and structural origin of β relaxations as well as for solving the brittleness in metallic glasses.

P1-17-10: Cabozantinib (XL184) in Patients with Metastatic Breast Cancer: Results from a Phase 2 Randomized Discontinuation Trial

Background: Cabozantinib is an oral, potent inhibitor of MET and VEGFR2. MET overexpression has been observed in metastatic breast cancer (MBC). High levels of VEGF and its receptors are associated with poor prognosis in patients (pts) with breast cancer. Simultaneous targeting of the MET and VEGF signaling pathways with cabozantinib may therefore be a promising treatment strategy. Results of a phase 2 randomized discontinuation trial (RDT) with single-agent cabozantinib have demonstrated clinical activity in a broad range of tumor types. In addition to observed effects on soft tissue lesions, cabozantinib has also been associated with effects on bone metastases as exhibited by partial or complete bone scan resolution, pain relief and/or reduction of narcotic use.

Methods: MBC pts (ER [+], triple [-] or inflammatory subtype) with progressive and measurable disease received single-agent cabozantinib at 100 mg qd PO over a 12 week (wk) lead-in period. Up to 4 prior treatment regimens (hormonal excluded) for MBC were allowed. Tumor response was assessed every 6 wks per mRECIST 1.0. Treatment beyond wk 12 was based on response: pts with partial response (PR) continued with open-label cabozantinib, those with stable disease (SD) were randomized to cabozantinib vs. placebo, and those with progressive disease were discontinued. The primary endpoint was objective response rate (ORR) in the lead-in period, and progression free survival in the randomized period. Post-hoc evaluations of bone scans were conducted.

Results: 20 MBC pts were enrolled with a median age of 55 years (range: 31–71).19 pts had invasive ductal carcinoma (1 pt with inflammatory MBC), and 1 pt had invasive lobular carcinoma. 75% of pts were ER/PR [+]; 15% were HER2/neu [+]. 85% of pts had visceral disease including 65% with liver metastases; 70% had bone disease. The median number of prior regimens was 3; 45% received prior anti-VEGF therapy. Most common related adverse events ≥ Grade 3 were fatigue/asthenia, 20%; and hand-foot syndrome, 20%. Dose reductions and permanent discontinuations for AEs occurred in 35% and 15% of pts, respectively.

Soft tissue effects: At wk 12, ORR per RECIST was 10% and overall disease control rate (PR+SD) was 45%. Notably, tumor shrinkage was observed in 15/16 pts (94%) with ≥1 post-baseline tumor assessment.

Bone effects: 2/3 pts evaluable by bone scan at baseline had partial resolution of lesions and one pt had SD on follow-up bone scans as early as Wk 6. Out of 7 pts receiving narcotics for bone pain, 3 pts reported improved pain and 2 pts had decreased narcotic use, per investigator. The majority of pts analyzed had declines in plasma CTx, an osteoclast marker. Additional enrollment and further bone marker analyses are ongoing.

Conclusions: Cabozantinib exhibits clinical activity in pts with MBC regardless of receptor and prior treatment status as reflected by high rate of tumor regression and effects on bone metastases. Cabozantinib is generally well tolerated and the safety profile is comparable to that seen with other tyrosine kinase inhibitors.

Citation Information: Cancer Res 2011;71(24 Suppl):Abstract nr P1-17-10.

Chronic treatment with a glucagon receptor antagonist lowers glucose and moderately raises circulating glucagon and glucagon-like peptide 1 without severe alpha cell hypertrophy in diet-induced obese mice

AIMS/HYPOTHESIS

Antagonism of the glucagon receptor (GCGR) represents a potential approach for treating diabetes. Cpd-A, a potent and selective GCGR antagonist (GRA) was studied in preclinical models to assess its effects on alpha cells.

METHODS

Studies were conducted with Cpd-A to examine the effects on glucose-lowering efficacy, its effects in combination with a dipeptidyl peptidase-4 (DPP-4) inhibitor, and the extent and reversibility of alpha cell hypertrophy associated with GCGR antagonism in mouse models.

RESULTS

Chronic treatment with Cpd-A resulted in effective and sustained glucose lowering in mouse models in which endogenous murine Gcgr was replaced with human GCGR (hGCGR). Treatment with Cpd-A also led to stable, moderate elevations in both glucagon and glucagon-like peptide 1 (GLP-1) levels, which were completely reversible and not associated with a hyperglycaemic overshoot following termination of treatment. When combined with a DPP-4 inhibitor, Cpd-A led to additional improvement of glycaemic control correlated with elevated active GLP-1 levels after glucose challenge. In contrast to Gcgr-knockout mice in which alpha cell hypertrophy was detected, chronic treatment with Cpd-A in obese hGCGR mice did not result in gross morphological changes in pancreatic tissue.

CONCLUSIONS/INTERPRETATION

A GRA lowered glucose effectively in diabetic models without significant alpha cell hypertrophy during or following chronic treatment. Treatment with a GRA may represent an effective approach for glycaemic control in patients with type 2 diabetes, which could be further enhanced when combined with DPP-4 inhibitors.