The chemical composition, size, shape and surface characteristics of nanoparticles affect the way proteins bind to these particles, and this in turn influences the way in which nanoparticles interact ...with cells and tissues. Nanomaterials bound with proteins can result in physiological and pathological changes, including macrophage uptake, blood coagulation, protein aggregation and complement activation, but the mechanisms that lead to these changes remain poorly understood. Here, we show that negatively charged poly(acrylic acid)-conjugated gold nanoparticles bind to and induce unfolding of fibrinogen, which promotes interaction with the integrin receptor, Mac-1. Activation of this receptor increases the NF-κB signalling pathway, resulting in the release of inflammatory cytokines. However, not all nanoparticles that bind to fibrinogen demonstrated this effect. Our results show that the binding of certain nanoparticles to fibrinogen in plasma offers an alternative mechanism to the more commonly described role of oxidative stress in the inflammatory response to nanomaterials.
Over the past decade, nanoparticles (NPs) have been increasingly developed in various biomedical applications such as cell tracking, biosensing, contrast imaging, targeted drug delivery, and tissue ...engineering. Their versatility in design and function has made them an attractive, alternative choice in many biological and biomedical applications. Cellular responses to NPs, their uptake, and adverse biological effects caused by NPs are rapidly-growing research niches. However, NP excretion and its underlying mechanisms and cell signaling pathways are yet elusive. In this review, we present an overview of how NPs are handled intracellularly and how they are excreted from cells following the uptake. We also discuss how exocytosis of nanomaterials impacts both the therapeutic delivery of nanoscale objects and their nanotoxicology.
Display omitted
•An overview of how NPs are handled intracellularly and how they are excreted from cells following uptake•Discussion of how exocytosis of nanomaterials impacts both therapeutic delivery of nanoscale objects and nanotoxicology•A better understanding of exocytosis and related cellular functions and their dynamics
Tissue hypoxia in solid tumors is caused by several pathological changes associated with tumor growth, including altered microvasculature structure, increased diffusional distances, and ...tumor-associated anemia. As the oxygen tension decreases, tumor cells adapt to the limited oxygen supply. Previous studies have shown that such adaptation leads to an aggressive phenotype that is resistant to many anti-cancer therapies. Induction of hypoxia inducible factors (HIFs) mediates many proteomic and genomic changes associated with tumor hypoxia. In breast cancers, HIFs not only predict poor prognosis, but also promote metastasis and drug resistance. Several studies have proposed HIF-1α as a druggable target in drug-resistant breast cancers, leading to the synthesis and development of small molecule inhibitors. Disappointingly, however, none of these small molecule inhibitors have progressed to clinical use. In this review, we briefly discuss the role of HIF-1α in breast cancer drug resistance and summarize the current and future approaches to targeting this transcription factor in breast cancer treatment.
•Breast cancer treatments fail due to development of drug resistance.•Solid tumors display regions of hypoxia, which express hypoxia inducible factors.•Hypoxia inducible factors promote drug resistance in breast cancers.•Resistance occurs with conventional chemotherapy, targeted chemotherapy and endocrine therapy.•Drugs developed to target hypoxia inducible factors have potential in breast cancer treatment.
Human arylamine N-acetyltransferase 1 (NAT1) has been associated with cancer cell growth and invasion, but the underlying molecular mechanisms remain unknown. NAT1 is located on the short arm of ...chromosome 8 (8p21), a region that is commonly deleted in colon cancer. Previously, it was reported that HT-29 colon cancer cells, which have a large deletion at 8p21-22, show marked morphological changes, increased E-cadherin expression and altered cell-cell contact inhibition following down-regulation of NAT1 with shRNA. By contrast, no effects on growth were observed in HeLa cells. In the present study, cellular changes following knockout of NAT1 with CRISPR/Cas9 in HT-29 and HeLa cells were compared in the presence and absence of glucose. Cell growth decreased in both cell-lines during glucose starvation, but it was enhanced in HT-29 cells following NAT1 deletion. This was due to an increase in ROS production that induced cell apoptosis. Both ROS production and cell death were prevented by the glutathione precursor N-acetylcysteine. NAT1 knockout also resulted in a loss of the gain-of-function p53 protein in HT-29 cells. When p53 expression was inhibited with siRNA in parental HT-29 cells, ROS production and apoptosis increased to levels seen in the NAT1 knockout cells. The loss of p53 may explain the decreased colony formation and increased contact inhibition previously reported following NAT1 down-regulation in these cells. In conclusion, NAT1 is important in maintaining intracellular ROS, especially during glucose starvation, by stabilizing gain-of-function p53 in HT-29 cells. These results suggest that NAT1 may be a novel target to decrease intracellular gain-of -function p53.
Arylamine N-acetyltransferase 1 (NAT1) is a drug metabolizing enzyme that has been associated with cancer cell proliferation in vitro and with survival in vivo. NAT1 expression has been associated ...with the estrogen receptor and it has been proposed as a prognostic marker for estrogen receptor positive cancers. However, little is known about the distribution of NAT1 mRNA across an entire patient population or its effects on outcomes. To address this, gene expression data from breast cancer patient cohorts were investigated to identify sub-populations based on the level of NAT1 expression. Patient survival and drug response was examined to determine whether NAT1 mRNA levels influenced any of these parameters.
NAT1 expression showed a trimodal distribution in breast cancer samples (n = 1980) but not in tumor tissue from ovarian, prostate, cervical or colorectal cancers. In breast cancer, NAT1 mRNA in each sub-population correlated with a separate set of genes suggesting different mechanisms of NAT1 gene regulation. Kaplan-Meier plots showed significantly better survival in patients with highest NAT1 mRNA compared to those with intermediate or low expression. While NAT1 expression was elevated in estrogen receptor-positive patients, it did not appear to be dependent on estrogen receptor expression. Overall survival was analyzed in patients receiving no treatment, hormone therapy or chemotherapy. NAT1 expression correlated strongly with survival in the first 5 years in those patients receiving chemotherapy but did not influence survival in the other two groups. This suggests that low NAT1 expression is associated with chemo-resistance. The sensitivity of NAT1 mRNA levels as a single parameter to identify non-responders to chemotherapy was 0.58 at a log(2) < 6.5.
NAT1 mRNA can be used to segregate breast cancer patients into sub-populations that demonstrate different overall survival. Moreover, low NAT1 expression shows a distinct poor response to chemotherapy. Analysis of NAT1 expression may be useful for identifying specific individuals who would benefit from alternative therapy or drug combinations. However, additional information is required to increase the sensitivity of identifying non-responders.
There are two human arylamine
-acetyltransferases (NAT1 and NAT2) that have evolved separately and differ in their substrate specificity and tissue localization. In addition to its acetyltransferase ...activity, NAT1 can hydrolyze acetyl coenzyme A to coenzyme A in the presence of folate. Here, we show that NAT1 is rapidly inactivated at temperatures above 39 °C whereas NAT2 is more stable. NAT1 acetyltransferase activity is also rapidly lost in whole cells at a rate similar to that of recombinant protein, suggesting it is not protected by intracellular chaperones. By contrast, the hydrolase activity of NAT1 is resistant to heat-induced inactivation, in part because folate stabilizes the protein. Heat generated by mitochondria following the dissipation of the inner membrane potential was sufficient to inactivate NAT1 in whole cells. Within the physiological range of core body temperatures (36.5-37.5 °C), NAT1 acetyltransferase activity decreased by 30% while hydrolase activity increased by >50%. This study demonstrates the thermal regulation of NAT1, but not NAT2, and suggests that NAT1 may switch between an acetyltransferase and a hydrolase within a narrow temperature range in the presence of folate.
Molecular imaging is a technique for quantifying physiological changes in vivo using imaging probes, or beacons, which can be detected noninvasively. This field of study has advanced rapidly in ...recent years, in part due to the application of nanotechnology. The versatility of different imaging modalities has been significantly enhanced by innovative nanoparticle development. These nanoprobes can be used to image specific cells and tissues within a whole organism. Some of the nanoparticles under development may be useful to measure biological processes associated with human disease and help monitor how these change with treatment. This review highlights some of the recent advances in nanoparticles for molecular imaging. It also addresses issues that arise with the use of nanoparticles. Whereas much of the technology remains at an experimental stage, the potential for enhancing disease diagnosis and treatment is considerable.
In vivo molecular imaging using nanoparticles promises to revolutionize diagnosis and treatment of human diseases, but some practical limitations still need to be resolved.
Nanoparticles rapidly interact with the proteins present in biological fluids, such as blood. The proteins that are adsorbed onto the surface potentially dictate the biokinetics of the nanomaterials ...and their fate in vivo. Using nanoparticles with different sizes and surface characteristics, studies have reported the effects of physicochemical properties on the composition of adsorbed plasma proteins. However, to date, few studies have been conducted focusing on the nanoparticles that are commonly exposed to the general public, such as the metal oxides. Using previously established ultracentrifugation approaches, two-dimensional gel electrophoresis and mass spectrometry, the current study investigated the binding of human plasma proteins to commercially available titanium dioxide, silicon dioxide and zinc oxide nanoparticles. We found that, despite these particles having similar surface charges in buffer, they bound different plasma proteins. For TiO2, the shape of the nanoparticles was also an important determinant of protein binding. Agglomeration in water was observed for all of the nanoparticles and both TiO2 and ZnO further agglomerated in biological media. This led to an increase in the amount and number of different proteins bound to these nanoparticles. Proteins with important biological functions were identified, including immunoglobulins, lipoproteins, acute-phase proteins and proteins involved in complement pathways and coagulation. These results provide important insights into which human plasma proteins bind to particular metal oxide nanoparticles. Because protein absorption to nanoparticles may determine their interaction with cells and tissues in vivo, understanding how and why plasma proteins are adsorbed to these particles may be important for understanding their biological responses.
Display omitted
Human arylamine N-acetyltransferase 1 (NAT1) encodes a drug-metabolising enzyme that plays a role in chemical-associated cancer risk, cancer cell survival and mitochondrial function. ...Its expression and protein activity are regulated by transcriptional, translational, and post-translational processes, including microRNAs such as miR-1290. Several studies have shown the presence of multiple polyadenylation sites in the NAT1 gene. However, their role in NAT1 expression is poorly understood. Here, we have investigated the genetic sequence of the NAT1 gene in human cell lines, peripheral blood mononuclear cells and breast tumour tissue. We identified five potential polyadenylation signals, two of which carry known single nucleotide polymorphism that affect site usage. Cells that are homozygous for adenine at base 1642, the most distal polyadenylation site, use this site whereas those homozygous for cytosine at base 1642 could not. We also found that the presence of adenine at base 1642 is associated with the NAT1*10 haplotype. Because the putative binding site for miR-1290 is located between the last two polyadenylation sites, we hypothesised that cells that do not use the most distal site will be unaffected by miR-1290. However, this was not the case. NAT1 activity was positively correlated with miR-1290, and induction of miR-1290 in SH-SY5Y cells was associated with induction, not inhibition, of NAT1 activity. The use of PolyA1264 or PolyA1642 did not alter NAT1 activity following ectopic expression of a miR-1290 mimic. These results suggest that the role of miR-1290 in the regulation of NAT1 activity is more complex than previously reported.
Drug resistance continues to be a major barrier to the delivery of curative therapies in cancer. Historically, drug resistance has been associated with over‐expression of drug transporters, changes ...in drug kinetics or amplification of drug targets. However, the emergence of resistance in patients treated with new‐targeted therapies has provided new insight into the complexities underlying cancer drug resistance. Recent data now implicate intratumoural heterogeneity as a major driver of drug resistance. Single cell sequencing studies that identified multiple genetically distinct variants within human tumours clearly demonstrate the heterogeneous nature of human tumours. The major contributors to intratumoural heterogeneity are (i) genetic variation, (ii) stochastic processes, (iii) the microenvironment and (iv) cell and tissue plasticity. Each of these factors impacts on drug sensitivity. To deliver curative therapies to patients, modification of current therapeutic strategies to include methods that estimate intratumoural heterogeneity and plasticity will be essential.
PDF
