Cancer stem cells (CSCs) comprise a subset of hierarchically organized, rare cancer cells with the ability to initiate cancer in xenografts of genetically modified murine models. CSCs are thought to ...be responsible for tumor onset, self-renewal/maintenance, mutation accumulation, and metastasis. The existence of CSCs could explain the high frequency of neoplasia relapse and resistance to all of currently available therapies, including chemotherapy. The phosphatidylinositol 3-kinase (PI3K)/Akt/mammalian target of rapamycin (mTOR) signaling pathway is a key regulator of physiological cell processes which include proliferation, differentiation, apoptosis, motility, metabolism, and autophagy. Nevertheless, aberrantly upregulated PI3K/Akt/mTOR signaling characterizes many types of cancers where it negatively influences prognosis. Several lines of evidence indicate that this signaling system plays a key role also in CSC biology. Of note, CSCs are more sensitive to pathway inhibition with small molecules when compared to healthy stem cells. This observation provides the proof-of-principle that functional differences in signaling transduction pathways between CSCs and healthy stem cells can be identified. Here, we review the evidence which links the signals deriving from the PI3K/Akt/mTOR network with CSC biology, both in hematological and solid tumors. We then highlight how therapeutic targeting of PI3K/Akt/mTOR signaling with small molecule inhibitors could improve cancer patient outcome, by eliminating CSCs.
We previously developed a calcium phosphate (CaP) calcifying solution that allows to deposit a uniform layer of nanocrystalline apatite on metallic implants in a few hours. In this work we modified ...the composition of the CaP solution by addition of Sr(2+), Mg(2+), and Mn(2+), in order to improve the biological performance of the implants. The results of the investigation performed on the coatings, as well as on the powders precipitated in the absence of the substrates, indicate that both Sr(2+) and Mg(2+) reduce the extent of precipitation, although they are quantitatively incorporated into the nanocrystalline apatitic phase. The inhibitory effect on deposition is much more evident for Mn(2+), which completely hinders the precipitation of apatite and yields just a small amount of amorphous phosphate relatively rich in manganese content. Human osteoblast-like MG-63 cells cultured on the different materials show that the Mg(2+) and Sr(2+) apatitic coatings promote proliferation and expression of collagen type I, with respect to bare Ti and to the thin layer of amorphous phosphate obtained in the presence of Mn(2+). However, the relatively high content of Mn(2+) in the phosphate has a remarkable beneficial effect on osteocalcin production, which is even greater than that observed for Sr(2+).
In vitro and in vivo behaviour of an injectable silk fibroin (SF) hydrogel was studied through osteoblast cultures and after implantation in critical-size defects of rabbit distal femurs. A ...commercial synthetic poly(
d,
l lactide-glycolide) copolymer was used as control material. In vitro biocompatibility was evaluated by measuring LDH release, cell proliferation (WST1), differentiation (ALP, OC), and synthetic activity (collagen I, TGF ß1, IL-6). Bone defect healing rate and quality of the newly formed bone inside the defects were determined in vivo by measuring trabecular bone volume
(BV/TV), trabecular thickness (Tb.Th), trabecular number (Tb.N), trabecular separation (Tb.Sp), mineral apposition rate (MAR) and bone formation rate (BFR/B.Pm). In vitro tests indicated that both materials significantly increased cell proliferation in comparison with the negative control. A significant increase in the TGF-
β1 level was found for SF hydrogel in comparison with the control material and negative control. Both materials promoted bone healing when used to fill critical size defects in rabbit femurs. The new-formed bone of the SF hydrogel treated defects showed significantly higher BV/TV, Tb.Th, MAR and BFR/B.Pm and lower Tb.Sp values in comparison with the control gel. At 12 weeks the re-grown bone of the SF hydrogel-treated defects appeared more similar to normal bone than that of the control synthetic polymeric material-treated defects, except for the Tb.N value that differed significantly from that of normal bone (
p<0.05). MAR and BFR/B.Pm presented significantly (
p<0.05) higher values for SF hydrogel-treated defects in comparison with controls treated with a synthetic polymeric material, confirming that SF hydrogel accelerated remodelling processes.
Abstract The direct synthesis of hydroxyapatite in the presence of bisphosphonates is quite difficult due to the great affinity for calcium of these compounds, which are widely used in the treatment ...of pathologies related to bone loss. We recently developed a new method which allowed to synthesize alendronate–hydroxyapatite composite nanocrystals with a bisphosphonate content up to about 7 wt%. Herein we report the results of an in vitro study aimed to investigate the effects of alendronate incorporation into hydroxyapatite on bone cells response. Osteoblast-like MG63 cells and human osteoclasts were cultured on nanocrystals at different alendronate content (3.9, 6.2, 7.1 wt%). MG63 cells cultured on the composite nanocrystals display normal morphology, good proliferation and increased values of the differentiation parameters. In particular, when cultured on composites at relatively high alendronate contents, osteoblasts display increased values of alkaline phosphatase activity (ALP), collagen type I, and osteocalcin production, as well as significant decrease of matrix metalloproteinases (MMP-1 and MMP-13) production, with respect both to the control and to pure hydroxyapatite nanocrystals. It follows that the presence of alendronate enhances osteoblast activation and extracellular matrix mineralization processes, without any abnormal collagen degradation. The osteoclast number on the composite nanocrystals decrease indicating that the bisphosphonate exerts its inhibitory effect on osteoclast proliferation even when incorporated into hydroxyapatite.
Women are at greater risk of developing osteoporosis (OP). However, in the past few years it has become more widely recognized that OP is a significant problem also in men although OP is frequently ...under-diagnosed and, consequently, under treated in men. Most guidelines, screening and fracture risk evaluation methods as well as pharmacologic agents have been developed for women and then adapted to men. Bone Mineral Density (BMD) measurement by Dual X-ray Absorptiometry (DEXA) is reported as T score and the capability of DEXA to diagnose OP and predict fracture risk is still debated. In addition, the use of female T score references for the diagnosis of OP in men is incorrect for the following reasons: 1) DXA definition was developed just for Caucasian women, 2) men and women display structural differences in terms of bone growth, catabolism and size; 3) aging men have more periosteal apposition, less cortical porosity and endocortical resorption than aging women; and 4) T scores results, both in man and in women, can be affected by the presence of co-morbidities and it is known that in men OP is often secondary.
From a biological point of view, OP is mainly due to increased osteoclastic activity leading to an imbalance in bone remodeling that favors resorption. However, some evidence suggests a more complex identity for osteoclasts (OCs) over and above their simple role of ‘bone eaters’. In our laboratory, we observed spontaneous OCs formation in vitro in peripheral blood mononuclear cells (PBMC) from OP patients (n.12 female patients and n.6 male patients; DXA T score-2.5 or less). Some researchers demonstrated OCs gender differences in bone resorption activity of female-derived versus male-derived OCs. Indeed, further data from our laboratory also showed gender differences in number of spontaneously differentiated OCs and differentiation time. Therefore, we hypothesized that it would be possible to perform OP screening and diagnosis observing and measuring PBMCs different ability to differentiate spontaneously into OCs in male and female patients. If this hypothesis will be confirmed, it will result in an effective and efficient strategy for OP screening, diagnosis, monitoring and fracture prevention, targeting health service resources on selected patients. However, our hypothesis must be tested in a properly designed clinical trial and several key issues still need to be addressed.
A map of landslide susceptibility is a necessary tool for proper planning and selection of sites for agriculture, infrastructure and other human developments. The Paonia–McClure Pass area of ...Colorado, USA, is well known for active mass movements. Large losses of property and risks to people highlight the need to accurately map susceptibility to shallow landslides and to identify safe locations for infrastructure and residential development.
We mapped 735 active mass movements and 17 factors about each one. The weights of evidence, frequency ratio of landslides, and fuzzy-logic method were used to create an optimum map of landslide susceptibility. Weights of the evidence were used to categorize continuous factor data, frequency ratios of shallow landslides were used to assign the membership values for the categories of the factors, and the fuzzy-logic method was used to integrate the membership values. Four models from the fuzzy-inference network of mapping susceptibility to shallow landslides were developed based on the combination of factors using five types of fuzzy operators. The first inference network model was comprised of the combination of factors, which are independent of each other. The second, third and the fourth inference network models were developed such that factors are not necessarily independent of each other. These models combine all dependent and independent factors, based on the expert's knowledge. Intermediate steps in the second, third and fourth models were developed by combining the fuzzy factors in the first step by fuzzy-OR, fuzzy-AND, and fuzzy-OR plus fuzzy-AND operations, respectively.
All models predicted similar percentages of observed shallow landslides with the fuzzy-gamma operation. Although the prediction capabilities of all the models are not significantly different, the fourth model is the best because it is the only model that accommodates the under-sampled and missed landslide data and the effect of increasing and decreasing gamma values. The first and third models create a problem if a category of a factor has a 0 membership value because of the absence or under-sampling of shallow landslides. The second model incurs the highest increasing effect of gamma values, and the third model incurs the highest decreasing effect of gamma values. The approaches described in this paper reduce the uncertainties associated with the categorization of continuous data, determination of fuzzy-membership values, and the combination of factors that causes shallow landslides.
Collagen was covalently linked to the surface of Titanium (Ti) by a surface modification process involving deposition of a thin film from hydrocarbon plasma followed by acrylic acid grafting. The ...composition and properties of surface-modified Ti were investigated by a number of surface sensitive techniques: XPS, ATR-IR, atomic force microscopy and AFM force–separation curves. In vitro tests were performed to check samples cytotoxicity and the behavior of osteoblast-like SaOS-2 cells. In vivo experiments involved 12 weeks implants in rabbit muscle as general biocompatibility assessment and 1-month implants in rabbit bone to evaluate the effect of surface modification on osteointegration rate. Results of XPS measurements show how surface chemistry is affected throughout each step of the surface modification process, finally leading to a complete and homogeneous collagen overlayer on top of the Ti samples. AFM data clearly display the modification of the surface topography and of the surface area of the samples as a consequence of the grafting and coupling process. AFM force–distance curves show that the interfacial structure responds by shrinking or swelling to variations of ionic force of the surrounding aqueous environment, suggesting that the aqueous interface of the biochemically modified Ti samples has enhanced degrees of freedom as compared to the inorganic surface of plain Ti. As to biological evaluations, the biochemically modified Ti samples are safe in terms of cytotoxicity and in vivo biocompatibility assessment. SaOS-2 cells growth rate is lower on collagen modified surfaces, and no significant difference is detected in terms of alkaline phosphatase production as compared to control Ti. Importantly, implants in rabbit femur show a significant increase of bone growth and bone-to-implant contact in the case of the collagen modified samples, confirming that biochemical modifications of Ti surface can enhance the rate of bone healing as compared to plain Ti.
