Targeting PI3K/Akt/mTOR cascade: the medicinal potential, updated research highlights and challenges ahead

Nowadays, cancer treatment is moving away from conventional cytotoxic drugs to target-based agents. This is primarily attributed to some remarkable leaps made in deciphering the tumor-relevant signaling pathways. Among them, PI3K/Akt/mTOR cascade presently elicits a substantial amount of pharmaceutical interests owing to its intimate role in tumor initiation and progression. Additionally, its medicinal potential lies in some protein kinases along the cascade, embracing PI3K, Akt and mTOR, which regulate crucial cellular activities. During the pursuit of PI3K axis inhibitors, medicinal chemistry efforts have diverged into three separate directions for addressing the issues associated with pioneering PI3K axis inhibitors, including poor pharmacokinetic (PK) profiles, low kinase specificity and lack of multiple inhibitory activities. Distinguished from other reviews in the literature, this article will outline these issues in sequence and give an account of recent medicinal chemistry efforts along with updated strides in surmounting them. Particularly, some candidates developed upon these efforts will be highlighted for their design rationale, preclinical performance or clinical status. Rather than merely focus on stunning breakthroughs, the review will critically remind us of the underlying challenges in developing PI3K axis modulators to direct the future research in this field.

p53 suppresses carcinoma progression by inhibiting mTOR pathway activation

Genetic alterations in human cancers and murine models indicate that Rb and p53 have critical tumor suppressive functions in retinoblastoma, a tumor of neural origin, and neuroendocrine tumors including small cell lung cancer and medullary thyroid cancer (MTC). Rb inactivation is the initiating lesion in retinoblastoma and current models propose that induction of apoptosis is a key p53 tumor suppressive function. Genetic studies in mice, however, indicate that other undefined p53 tumor suppressive functions are operative in vivo. How p53 loss cooperates with Rb inactivation to promote carcinogenesis is also not fully understood. In the current study, genetically engineered mice were generated to determine the role of Rb and p53 in MTC pathogenesis and test the hypothesis that p53 suppresses carcinogenesis by inhibiting mTOR signaling. Conditional Rb ablation resulted in thyroid tumors mimicking human MTC, and additional p53 loss led to rapid tumor progression. p53 suppressed tumorigenesis by inhibiting cell cycle progression, but did not induce apoptosis. On the contrary, p53 loss led to increased apoptosis that had to be overcome for tumor progression. mTOR activity was markedly increased in p53 deficient tumors and rapamycin treatment suppressed tumor cell growth identifying mTOR inhibition as a critical p53 tumor suppressive function. Rapamycin treatment did not result in AKT/MAPK activation providing evidence that this feedback mechanism operative in other cancers is not a general response to mTORC1 inhibition. Together, these studies provide mechanistic links between genetic alterations and aberrant signaling pathways critical in carcinogenesis, and identify essential Rb and p53 tumor suppressive functions in vivo.

Two-center interferences in dielectronic transitions in H2(+) + He collisions

Molecular two-center interferences in a collision induced excitation of H2(+) projectile ions, with simultaneous ionization of helium target atoms, are investigated in a kinematically complete experiment. In the process under investigation, the helium atom is singly ionized and simultaneously the molecular hydrogen ion is dissociated. Different collision mechanisms are identified and interference fringes emerging from a correlated first-order mechanism and from an independent second-order process are observed.

Why do the [PhSiO1.5]8,10,12 cages self-brominate primarily in the ortho position? Modeling reveals a strong cage influence on the mechanism

(PhSiO_1.5)_8,10,12 cages are bulky, electron withdrawing like CF₃; yet self-brominate (60 °C), favoring ortho substitution: PhT₈ (≈85%), PhT₁₀ (≈75%) and PhT₁₂ (60%).

An in vivo study of hindfoot 3D kinetics in stage II posterior tibial tendon dysfunction (PTTD) flatfoot based on weight-bearing CT scan

OBJECTIVE

The objective of this study was to evaluate the rotation and translation of each joint in the hindfoot and compare the load response in healthy feet with that in stage II posterior tibial tendon dysfunction (PTTD) flatfoot by analysing the reconstructive three-dimensional (3D) computed tomography (CT) image data during simulated weight-bearing.

METHODS

CT scans of 15 healthy feet and 15 feet with stage II PTTD flatfoot were taken first in a non-weight-bearing condition, followed by a simulated full-body weight-bearing condition. The images of the hindfoot bones were reconstructed into 3D models. The 'twice registration' method in three planes was used to calculate the position of the talus relative to the calcaneus in the talocalcaneal joint, the navicular relative to the talus in talonavicular joint, and the cuboid relative to the calcaneus in the calcaneocuboid joint.

RESULTS

From non- to full-body-weight-bearing condition, the difference in the talus position relative to the calcaneus in the talocalcaneal joint was 0.6° more dorsiflexed (p = 0.032), 1.4° more everted (p = 0.026), 0.9 mm more anterior (p = 0.031) and 1.0 mm more proximal (p = 0.004) in stage II PTTD flatfoot compared with that in a healthy foot. The navicular position difference relative to the talus in the talonavicular joint was 3° more everted (p = 0.012), 1.3 mm more lateral (p = 0.024), 0.8 mm more anterior (p = 0.037) and 2.1 mm more proximal (p = 0.017). The cuboid position difference relative to the calcaneus in the calcaneocuboid joint did not change significantly in rotation and translation (all p ≥ 0.08).

CONCLUSION

Referring to a previous study regarding both the cadaveric foot and the live foot, joint instability occurred in the hindfoot in simulated weight-bearing condition in patients with stage II PTTD flatfoot. The method used in this study might be applied to clinical analysis of the aetiology and evolution of PTTD flatfoot, and may inform biomechanical analyses of the effects of foot surgery in the future. Cite this article: Bone Joint Res 2013;2:255-63.

Genetic diversity and relationships among accessions of five crested wheatgrass species (Poaceae: Agropyron) based on gliadin analysis

Agropyron Gaertn. is the most important genus in Triticeae (Poaceae), which includes many forage grasses with high economic value. The genetic diversity and relationships of 36 accessions from five crested wheatgrass species were analyzed by gliadin markers. A total of 54 product bands were detected after acid polyacrylamide gel electrophoresis (A-PAGE), of which 100% were polymorphic. The genetic similarity coefficient based on Nei-Li's method ranged from 0.065 to 0.755 with an average of 0.451. The Shannon diversity information index showed that there was a high level of genetic diversity among the accessions. An unweighted pair group method with arithmetic average (UPGMA) dendrogram was constructed based on the Nei-Li's genetic similarity coefficients, which showed the phylogenetic relationships among accessions of different species. Analysis of molecular variance (AMOVA) showed that the proportion of variance explained by inter- and intraspecific variance was 9.34 and 90.66%, respectively, which revealed that the genetic variations within species were higher than the variations among species. Based on pairwise genetic distances (ΦST) among species, the cluster analysis indicated that A. mongolicum had a low-affinity relationship with other species, while A. fragile showed a close relationship with A. cristatum ssp pectinatum. Finally, the implications of the results for the taxonomy of Agropyron were discussed.

White-matter microstructure in previously drug-naive patients with schizophrenia after 6 weeks of treatment

BACKGROUND

It is not clear whether the progressive changes in brain microstructural deficits documented in previous longitudinal magnetic resonance imaging (MRI) studies might be due to the disease process or to other factors such as medication. It is important to explore the longitudinal alterations in white-matter (WM) microstructure in antipsychotic-naive patients with first-episode schizophrenia during the very early phase of treatment when relatively 'free' from chronicity.

METHOD

Thirty-five patients with first-episode schizophrenia and 22 healthy volunteers were recruited. High-resolution diffusion tensor imaging (DTI) was obtained from participants at baseline and after 6 weeks of treatment. A 'difference map' for each individual was calculated from the 6-week follow-up fractional anisotropy (FA) of DTI minus the baseline FA. Differences in Positive and Negative Syndrome Scale (PANSS) scores and Global Assessment of Functioning (GAF) scores between baseline and 6 weeks were also evaluated and expressed as a 6-week/baseline ratio.

RESULTS

Compared to healthy controls, there was a significant decrease in absolute FA of WM around the bilateral anterior cingulate gyrus and the right anterior corona radiata of the frontal lobe in first-episode drug-naive patients with schizophrenia following 6 weeks of treatment. Clinical symptoms improved during this period but the change in FA did not correlate with the changes in clinical symptoms or the dose of antipsychotic medication.

CONCLUSIONS

During the early phase of treatment, there is an acute reduction in WM FA that may be due to the effects of antipsychotic medications. However, it is not possible to entirely exclude the effects of underlying progression of illness.

Bendless modulates JNK-mediated cell death and migration in Drosophila

The TNF-JNK pathway is a highly conserved signaling pathway that regulates a wide spectrum of biological processes including cell death and migration. To further delineate this pathway, we carried out a genetic screen for dominant modifiers of the cell death phenotype triggered by ectopic expression of Eiger (Egr), the Drosophila TNF ortholog. Here we show that Bendless (Ben), an E2 ubiquitin-conjugating enzyme, modulates Egr-induced JNK activation and cell death through dTRAF2. Furthermore, Ben physically interacts with dTRAF2 and regulates Egr-induced dTRAF2 polyubiquitination. Finally, Ben is required for JNK-dependent tumor progression, cell migration, oxidative stress resistance and longevity. Our results indicate that Ben constitutes an essential component of the evolutionarily conserved TNF-JNK pathway that modulates cell death and invasion, tumor progression, stress response and lifespan in metazoans.

A sensitive and specific nanoparticle-assisted PCR assay for rapid detection of porcine parvovirus

A novel nanoparticle-assisted polymerase chain reaction (nanoPCR) assay to detect porcine parvovirus (PPV) is described here. Primers for this assay were designed based on the conserved region of the nonstructural protein 1 (NS1) gene of PPV, which encodes one of the nonstructural proteins. The sensitivity of the PPV nanoPCR assay was measured by using diluted recombinant plasmids in which the PPV NS1 gene had been inserted. The detection limit was 5.6 × 10(1) copies μl(-1) for the PPV nanoPCR assay vs 5.6 × 10(3) copies μl(-1) for conventional PCR assay. The results showed that the sensitivity of PPV nanoPCR assay was 100 times higher than that of conventional PCR assay. The PPV nanoPCR assay produced 142-bp product as expected when amplifying PPV DNA, while produced nothing when amplifying the DNA or cDNA of the following viruses: swine encephalomyocarditis virus, classical swine fever virus, porcine pseudorabies virus, porcine reproductive and respiratory syndrome virus, porcine teschovirus and porcine circovirus type II. PPV was detected in 108 of 109 clinical swine samples from Heilongjiang, Jilin and Henan provinces using the nanoPCR assay, and the results were confirmed by sequencing.

SIGNIFICANCE AND IMPACT OF THE STUDY

Nanoparticle-assisted polymerase chain reaction (nanoPCR) assay is an improved PCR. NanoPCR is highly sensitive and specific because the nanofluids formed in the nanobuffer have high thermal conductivity, which reduces the time required to reach the target temperature. It is more sensitive than conventional PCR, and it could detect the cases earlier than conventional PCR. This report describes the first application of the highly efficient nanoPCR technology for the detection of porcine parvovirus (PPV). The PPV nanoPCR assay will be useful for the detection and study of PPV and will also be applicable to improve the detection of other viruses.

Src42A modulates tumor invasion and cell death via Ben/dUev1a-mediated JNK activation in Drosophila

Loss of the cell polarity gene could cooperate with oncogenic Ras to drive tumor growth and invasion, which critically depends on the c-Jun N-terminal Kinase (JNK) signaling pathway in Drosophila. By performing a genetic screen, we have identified Src42A, the ortholog of mammalian Src, as a key modulator of both Ras^V12/lgl^−/− triggered tumor invasion and loss of cell polarity gene-induced cell migration. Our genetic study further demonstrated that the Bendless (Ben)/dUev1a ubiquitin E2 complex is an essential regulator of Src42A-induced, JNK-mediated cell migration. Furthermore, we showed that ectopic Ben/dUev1a expression induced invasive cell migration along with increased MMP1 production in wing disc epithelia. Moreover, Ben/dUev1a could cooperate with Ras^V12 to promote tumor overgrowth and invasion. In addition, we found that the Ben/dUev1a complex is required for ectopic Src42A-triggered cell death and endogenous Src42A-dependent thorax closure. Our data not only provide a mechanistic insight into the role of Src in development and disease but also propose a potential oncogenic function for Ubc13 and Uev1a, the mammalian homologs of Ben and dUev1a.

Fronto-parietal white matter microstructural deficits are linked to performance IQ in a first-episode schizophrenia Han Chinese sample

BACKGROUND

Evidence shows that cognitive deficits and white matter (WM) dysconnectivity can independently be associated with clinical manifestations in schizophrenia. It is important to explore this triadic relationship in order to investigate whether the triplet could serve as potential extended endophenotypes of schizophrenia.

METHOD

Diffusion tensor images and clinical performances were evaluated in 122 individuals with first-episode schizophrenia and 122 age- and gender-matched controls. In addition, 65 of 122 of the patient group and 40 of 122 controls were measured using intelligence quotient (IQ) testing.

RESULTS

The schizophrenia group showed lower fractional anisotropy (FA) values than controls in the right cerebral frontal lobar sub-gyral (RFSG) WM. The schizophrenia group also showed a significant positive correlation between FA in the RFSG and performance IQ (PIQ) ; in turn, their PIQ score showed a significant negative correlation with negative syndromes.

CONCLUSIONS

Overall, these findings support the hypothesis that WM deficits may be a core deficit that contributes to cognitive deficits as well as to negative symptoms.

A risk score for predicting post-traumatic stress disorder in adults in a Chinese earthquake area

OBJECTIVES

This study aimed to identify risk factors for post-traumatic stress disorder (PTSD) and develop a risk score model for predicting PTSD in adults in a Chinese earthquake area.

METHODS

Questionnaires covering demographic information, earthquake experience and social support were administered to subjects experiencing a major earthquake. The PTSD Checklist-Civilian Version questionnaire was used for PTSD diagnosis. Subjects were randomly assigned to training (70%) or validation (30%) subsets. A risk score model for predicting PTSD risk was established, based on logistic regression of PTSD risk factors that were significant on univariate analysis of the training data.

RESULTS

In total, 9556 subjects completed questionnaires; PTSD prevalence was 4.5%. Divorced or widowed status, various adverse earthquake events and low levels of social support were identified as risk factors for PTSD. When tested in the validation dataset, the risk score model had good discriminative power and a good fit between predicted and observed values.

CONCLUSIONS

The risk score shows an acceptable predictive value and may be useful for early prediction of PTSD, in Chinese earthquake areas.

Overexpression of 4EBP1, p70S6K, Akt1 or Akt2 differentially promotes Coxsackievirus B3-induced apoptosis in HeLa cells

Our previous studies have shown that the inhibition of phosphatidylinositol 3-kinase (PI3K) or mTOR complex 1 can obviously promote the Coxsackievirus B3 (CVB3)-induced apoptosis of HeLa cells by regulating the expression of proapoptotic factors. To further illustrate it, Homo sapiens eIF4E-binding protein 1 (4EBP1), p70S6 kinase (p70S6K), Akt1 and Akt2 were transfected to HeLa cells, respectively. And then, we established the stable transfected cell lines. Next, after CVB3 infection, apoptosis in different groups was determined by flow cytometry; the expressions of Bim, Bax, caspase-9 and caspase-3 were examined by real-time fluorescence quantitative PCR and western blot analysis; the expression of CVB3 mRNA and viral capsid protein VP1 were also analyzed by real-time fluorescence quantitative PCR, western blot analysis and immunofluorescence, respectively. At the meantime, CVB3 replication was observed by transmission electron microscope. We found that CVB3-induced cytopathic effect and apoptosis in transfected groups were more obvious than that in controls. Unexpectedly, apoptosis rate in Akt1 group was higher than others at the early stage after viral infection and decreased with the viral-infected time increasing, which was opposite to other groups. Compared with controls, the expression of CVB3 mRNA was increased at 3, 6, 12 and 24 h postinfection (p. i.) in all groups. At the meantime, VP1 expression in 4EBP1 group was higher than control during the process of infection, while the expressions in the other groups were change dynamically. Moreover, overexpression of 4EBP1 did not affect the mRNA expressions of Bim, Bax, caspase-9 and caspase-3; while protein expressions of Bim and Bax were decreased, the self-cleavages of caspase-9 and caspase-3 were stimulated. Meanwhile, overexpression of p70S6K blocked the CVB3-induced Bim, Bax and caspase-9 expressions but promoted the self-cleavage of caspase-9. In the Akt1 group, it is noteworthy that the expressions of Bim protein were higher than controls at 3 and 6 h p. i. but lower at 24 h p. i., and the expression of Bax protein were higher at 6 and 24 h p. i., while their mRNA expressions were all decreased. Furthermore, overexpression of Akt1 stimulated the procaspase-9 and procaspase-3 expression but blocked their self-cleavages. Overexpression of Akt2, however, had little effect on Bim, Bax and caspase-3, while prevented caspase-9 from self-cleavage at the late stage of CVB3 infection. As stated above, our results demonstrated that overexpression of 4EBP1, p70S6K, Akt1 or Akt2 could promote the CVB3-induced apoptosis in diverse degree via different mediating ways in viral replication and proapoptotic factors in BcL-2 and caspase families. As 4EBP1, p70S6K and Akt are the important substrates of PI3K and mammalian target of rapamycin (mTOR), we further illustrated the role of PI3K/Akt/mTOR signaling pathway in the process of CVB3-induced apoptosis.

Butyrate promotes the recovering of intestinal wound healing through its positive effect on the tight junctions

Postweaning diarrhea is one of the most common causes of morbidity and mortality in weanling piglets. Feeding sodium butyrate to weanling piglets decreased the incidence of diarrhea, but the mechanism has not been fully elucidated. The present study was to evaluate the effect of sodium butyrate on diarrhea in relation to wound healing of intestinal barrier using IPEC-J2 cell model. Cultured cells were scratched to induce wound and then were treated with 4 mM sodium butyrate. The results showed that supplementation of the cells with sodium butyrate significantly promoted the process of wound healing, indicating the protective effects of butyrate on the intestinal mucosa. Butyrate treatment enhanced mRNA expression of the intestinal mucosal tight junction proteins occludin and zonula occluden protein-1 (P < 0.05), which suggested that the promotion of wound healing by butyrate is related to the maintenance of the function of the intestinal barrier. In addition, in the butyrate-treated group, intestinal total superoxide dismutase and glutathione peroxidase (P < 0.05), two of the main antioxidant enzymes, as well as glutathione (P < 0.05), one of the nonenzymatic antioxidant components, were enhanced whereas the malondialdehyde level, a marker of free radical mediated lipid peroxidation injury, was decreased (P < 0.05) compared with the control group. Collectively, these results indicate that dietary sodium butyrate might, at least partly, play an important role in recovering the intestinal tight junctions having a positive effect on maintaining the gut integrity.

Anthropometric measures and epithelial ovarian cancer risk among Chinese women: results from the Shanghai Women's Health Study

Background:

Studies of anthropometric measures and ovarian cancer risk have predominantly included women of European descent with mixed findings.

Methods:

Data from the prospective Shanghai Women's Health Study (SWHS) were used to evaluate associations between anthropometric measures and risk of epithelial ovarian cancer (EOC). Hazard ratios (HRs) and 95% confidence intervals (CIs) were estimated by Cox proportional hazards regression.

Results:

A total of 152 EOC cases occurred among 70 258 women. Increasing quartiles of weight, hip circumference, and weight gain during adulthood were associated with significantly increased EOC risks. Body mass index (BMI) was also associated; overweight (25⩽BMI<29.99) and obese women (BMI⩾30.0) had significantly increased risks (HR: 1.49, 95% CI: 1.05, 2.13, and HR: 2.42, 95% CI: 1.37, 4.28, respectively). No significant associations were observed for height, waist circumference, waist-to-hip ratio (WHR), and waist-to-height ratio (WHER).

Conclusion:

Results from this large prospective study of Chinese women support the hypothesis that general adiposity contributes to the aetiology of ovarian cancer.