Specific repression of mutant K-RAS by 10-23 DNAzyme: Sensitizing cancer cell to anti-cancer therapies

Point mutations of the Ras family are frequently found in human cancers at a prevalence rate of 30%. The most common mutation K-Ras(G12V), required for tumor proliferation, survival, and metastasis due to its constitutively active GTPase activity, has provided an ideal target for cancer therapy. 10-23 DNAzyme, an oligodeoxyribonucleotide-based ribonuclease consisting of a 15-nucleotide catalytical domain flanked by two target-specific complementary arms, has been shown to effectively cleave the target mRNA at purine-pyrimidine dinucleotide. Taking advantage of this specific property, 10-23 DNAzyme was designed to cleave mRNA of K-Ras(G12V)(GGU → GUU) at the GU dinucleotide while left the wild-type (WT) K-Ras mRNA intact. The K-Ras(G12V)-specific 10-23 DNAzyme was able to reduce K-Ras(G12V) at both mRNA and protein levels in SW480 cell carrying homozygous K-Ras(G12V). No effect was observed on the WT K-Ras in HEK cells. Although K-Ras(G12V)-specific DNAzymes alone did not inhibit proliferation of SW480 or HEK cells, pre-treatment of this DNAzyme sensitized the K-Ras(G12V) mutant cells to anti-cancer agents such as doxorubicin and radiation. These results offer a potential of using allele-specific 10-23 DNAzyme in combination with other cancer therapies to achieve better effectiveness on cancer treatment.     

Inhibition of a mitotic motor protein: where, how, and conformational consequences

We report here the first inhibitor-bound structure of a mitotic motor protein. The 1.9 A resolution structure of the motor domain of KSP, bound with the small molecule monastrol and Mg2+ x ADP, reveals that monastrol confers inhibition by "induced-fitting" onto the protein some 12 A away from the catalytic center of the enzyme, resulting in the creation of a previously non-existing binding pocket. The structure provides new insights into the biochemical and mechanical mechanisms of the mitotic motor domain. Inhibition of KSP provides a novel mechanism to arrest mitotic spindle formation, a target of several approved and investigative anti-cancer agents. The structural information gleaned from this novel pocket offers a new angle for the design of anti-mitotic agents.     

Emerging power of proteomics for delineation of intrinsic tumor subtypes and resistance mechanisms to anti-cancer therapies

Introduction: Despite extreme genetic heterogeneity, tumors often show similar alterations in the expression, stability, and activation of proteins important in oncogenic signaling pathways. Thus, classifying tumor samples according to shared proteomic features may help facilitate the identification of cancer subtypes predictive of therapeutic responses and prognostic for patient outcomes. Meanwhile, understanding mechanisms of intrinsic and acquired resistance to anti-cancer therapies at the protein level may prove crucial to devising reversal strategies.

Areas covered: Herein, we review recent advances in quantitative proteomic technology and their applications in studies to identify intrinsic tumor subtypes of various tumors, to illuminate mechanistic aspects of pharmacological and oncogenic adaptations, and to highlight interaction targets for anti-cancer compounds and cancer-addicted proteins.

Expert commentary: Quantitative proteomic technologies are being successfully employed to classify tumor samples into distinct intrinsic subtypes, to improve existing DNA/RNA based classification methods, and to evaluate the activation status of key signaling pathways.     

Microtubules,microtubule-interfering agents and apoptosis

Microtubules are dynamic polymers that play crucial roles in a large number of cellular functions. Their pivotal role in mitosis makes them a target for the development of anticancer drugs. Microtubule-damaging agents suppress microtubule dynamics, leading to disruption of the mitotic spindle in dividing cells, cell cycle arrest at M phase, and late apoptosis. A better understanding of the processes coupling microtubule damage to the onset of apoptosis will reveal sites of potential intervention in cancer chemotherapy. Inhibition of microtubule dynamics induces persistent modification of biological processes (M arrest) and signaling pathways (mitotic spindle assembly checkpoint activation, Bcl-2 phosphorylation, c-Jun NH₂-terminal kinase activation), which ultimately lead to apoptosis through the accumulation of signals that finally reach the threshold for the onset of apoptosis or through diminishing the threshold for engagement of cell death. Microtubules serve also as scaffolds for signaling molecules that regulate apoptosis, such as Bim and survivin, and their release from microtubules affect the activities of these apoptosis regulators. Thus, sustained modification of signaling routes and changes in the scaffolding properties of microtubules seem to constitute two major processes in the apoptotic response induced by microtubule-interfering agents.     

Ontogeny of rat chondrocyte proliferation： studies in embryo, adult and osteoarthritic （OA） cartilage

The aim of this work was to study the ontogeny of chondrocyte cell division using embryo, adult and osteoarthritic(OA) cartilage. We searched for mitosis phases and performed a comparative evaluation of mitotic index, basic fibroblast growth factor b (FGFb), transforming growth factor β1 (TGF-β1) receptors, cyclin dependent kinase (CDK 1)and Cyclin-B expression in fetal, neonate, 3, 5, 8 weeks old rats and experimental OA. Our results showed that mitosis phases were observed in all normal cartilage studied, although, we found a decrease in mitotic index in relation to tissue development. No mitosis was detected in OA cartilage. We also found a statistical significant reduction in cell number in OA cartilage, compared with the normal tissue. Furthermore, FGFb and TGF-β1 receptors diminished in relation to tissue development, and were very scarce in experimental OA. Western blot assays showed CDK-1 expression in all cases, including human-OA cartilage. Similar results were observed for Cyclin-B, except for 8 weeks, when it was notexpressed. Our results suggest that cell division seems to be scarce, if not absent within the OA cartilage studied.Nevertheless, the existence of factors essential for cell division leaves open the question concerning chondrocyte proliferation in OA cartilage, which is likely to be present in the early stages of the disease.     

Role of proteins of the macroglobulin family in regulation of tumor growth

Proteins of the macroglobulin family are an ancient and evolutionarily conservative link of the immune system, which is actively involved in both inhibition of tumor growth cells and proliferation of tumor cells. Two basically different binding sites and a great conformational plasticity of all representatives of the macroglobulin family, as well as the presence of two to four representatives of the family in the blood of most species allow them to transport diverse substances and exert various regulatory influences on both the tumor and the entire organism. For example, the capacity of macroglobulins for binding hydrolases makes it possible to inhibit enzyme mediated tumor invasion. At the same time, an excess of macroglobulin/hydrolase complexes can activate apoptosis. The tumor is able of using macroglobulins, especially pregnancy-associated proteins, for its own protection. Specifically, pregnancy-associated α₂-glycoprotein, which is actively produced by human tumor cells, blocks the his to compatibility complex antigens. On the contrary, the capacity of binding zinc stimulates the thymulin-dependent activation of natural killer cells. Nevertheless, the actively growing tumor expresses many receptors to macroglobulins, which are the main carriers of some cytokines and growth factors essential for proliferation.     

Epidemic modelling: Aspects where stochasticity matters

Epidemic models are always simplifications of real world epidemics. Which real world features to include, and which simplifications to make, depend both on the disease of interest and on the purpose of the modelling. In the present paper we discuss some such purposes for which a stochastic model is preferable to a deterministic counterpart. The two main examples illustrate the importance of allowing the infectious and latent periods to be random when focus lies on the probability of a large epidemic outbreak and/or on the initial speed, or growth rate, of the epidemic. A consequence of the latter is that estimation of the basic reproduction number R₀ is sensitive to assumptions about the distributions of the infectious and latent periods when using data from the early stages of an outbreak, which we illustrate with data from the H1N1 influenza A pandemic. Some further examples are also discussed as are some practical consequences related to these stochastic aspects.     

Plants in a crowded stand regulate their height growth so as to maintain similar heights to neighbours even when they have potential advantages in height growth

Background and Aims

Although being tall is advantageous in light competition, plant height growth is often similar among dominant plants in crowded stands (height convergence). Previous theoretical studies have suggested that plants should not overtop neighbours because greater allocation to supporting tissues is necessary in taller plants, which in turn lowers leaf mass fraction and thus carbon gain. However, this model assumes that a competitor has the same potential of height growth as their neighbours, which does not necessarily account for the fact that height convergence occurs even among individuals with various biomass.

Methods

Stands of individually potted plants of Chenopodium album were established, where target plants were lifted to overtop neighbours or lowered to be overtopped. Lifted plants were expected to keep overtopping because they intercept more light without increased allocation to stems, or to regulate their height to similar levels of neighbours, saving biomass allocation to the supporting organ. Lowered plants were expected to be suppressed due to the low light availability or to increase height growth so as to have similar height to the neighbours.

Key Results

Lifted plants reduced height growth in spite of the fact that they received higher irradiance than others. Lowered plants, on the other hand, increased the rate of stem elongation despite the reduced irradiance. Consequently, lifted and lowered plants converged to the same height. In contrast to the expectation, lifted plants did not increase allocation to leaf mass despite the decreased stem length. Rather, they allocated more biomass to roots, which might contribute to improvement of mechanical stability or water status. It is suggested that decreased leaf mass fraction is not the sole cost of overtopping neighbours. Wind blowing, which may enhance transpiration and drag force, might constrain growth of overtopping plants.

Conclusions

The results show that plants in crowded stands regulate their height growth to maintain similar height to neighbours even when they have potential advantages in height growth. This might contribute to avoidance of stresses caused by wind blowing.     

The anti-cancer properties of heparin and its derivatives: a review and prospect

ABSTRACT

Heparin, including unfractionated heparin (UFH), low-molecular-weight heparin (LMWH) and heparin derivatives, are commonly used in venous thromboembolism treatment and reportedly have beneficial effects on cancer survival. Heparin can affect the proliferation, adhesion, angiogenesis, migration and invasion of cancer cells via multiple mechanisms. The main mechanisms involve inhibition of heparanase, P-/L-selectin, angiogenesis, and interference with the CXCL12-CXCR4 axis. Here we summarize the current experimental evidence regarding the anti-cancer role of heparin and its derivatives, and conclude that there is evidence to support heparin’s role in inhibiting cancer progression, making it a promising anti-cancer agent.