Signaling dynamics in coexisting monoclonal cell subpopulations unveil mechanisms of resistance to anti-cancer compounds.

BACKGROUND: Tumor heterogeneity is a main contributor of resistance to anti-cancer targeted agents though it has proven difficult to study. Unfortunately, model systems to functionally characterize and mechanistically study dynamic responses to treatment across coexisting subpopulations of cancer cells remain a missing need in oncology. METHODS: Using single cell cloning and expansion techniques, we established monoclonal cell subpopulations (MCPs) from a commercially available epidermal growth factor receptor (EGFR)-mutant non-small cell lung cancer cell line. We then used this model sensitivity to the EGFR inhibitor osimertinib across coexisting cell populations within the same tumor. Pathway-centered signaling dynamics associated with response to treatment and morphological characteristics of the MCPs were assessed using Reverse Phase Protein Microarray. Signaling nodes differentially activated in MCPs less sensitive to treatment were then pharmacologically inhibited to identify target signaling proteins putatively implicated in promoting drug resistance. RESULTS: MCPs demonstrated highly heterogeneous sensitivities to osimertinib. Cell viability after treatment increased > 20% compared to the parental line in selected MCPs, whereas viability decreased by 75% in other MCPs. Reduced treatment response was detected in MCPs with higher proliferation rates, EGFR L858R expression, activation of EGFR binding partners and downstream signaling molecules, and expression of epithelial-to-mesenchymal transition markers. Levels of activation of EGFR binding partners and MCPs' proliferation rates were also associated with response to c-MET and IGFR inhibitors. CONCLUSIONS: MCPs represent a suitable model system to characterize heterogeneous biomolecular behaviors in preclinical studies and identify and functionally test biological mechanisms associated with resistance to targeted therapeutics.

Surface temperatures are influenced by handling stress independently of corticosterone levels in wild king penguins (Aptenodytes patagonicus).

Assessing the physiological stress responses of wild animals opens a window for understanding how organisms cope with environmental challenges. Since stress response is associated with changes in body temperature, the use of body surface temperature through thermal imaging could help to measure acute and chronic stress responses non-invasively. We used thermal imaging, acute handling-stress protocol and an experimental manipulation of corticosterone (the main glucocorticoid hormone in birds) levels in breeding king penguins (Aptenodytes patagonicus), to assess: 1. The potential contribution of the Hypothalamo-Pituitary-Adrenal (HPA) axis in mediating chronic and acute stress-induced changes in adult surface temperature, 2. The influence of HPA axis manipulation on parental investment through thermal imaging of eggs and brooded chicks, and 3. The impact of parental treatment on offspring thermal's response to acute handling. Maximum eye temperature (Teye) increased and minimum beak temperature (Tbeak) decreased in response to handling stress in adults, but neither basal nor stress-induced surface temperatures were significantly affected by corticosterone implant. While egg temperature was not significantly influenced by parental treatment, we found a surprising pattern for chicks: chicks brooded by the (non-implanted) partner of corticosterone-implanted individuals exhibited higher surface temperature (both Teye and Tbeak) than those brooded by glucocorticoid-implanted or control parents. Chick's response to handling in terms of surface temperature was characterized by a drop in both Teye and Tbeak independently of parental treatment. We conclude that the HPA axis seems unlikely to play a major role in determining chronic or acute changes in surface temperature in king penguins. Changes in surface temperature may primarily be mediated by the Sympathetic-Adrenal-Medullary (SAM) axis in response to stressful situations. Our experiment did not reveal a direct impact of parental HPA axis manipulation on parental investment (egg or chick temperature), but a potential influence on the partner's brooding behaviour.

Rapid thermal immune acclimation in common musk turtles (Sternotherus odoratus).

As infectious diseases in ectothermic vertebrates increasingly threaten wild populations, understanding how host immune systems are affected by the environment is key to understanding the process of infection. In this study, we investigated how temperature change and simulated bacterial infection (via lipopolysaccharide [LPS] injection) interacted to regulate innate immunity, as measured by bactericidal ability (BA), phagocytosis rate, and heterophil:lymphocyte ratio (HLR) in common musk turtles (Sternotherus odoratus). We found that LPS stimulated an acute immune response, as measured by an increase in BA, phagocytosis rate, and HLR. When exposed to a 5 or 10°C temperature change for 48 hr, turtles rapidly acclimated to the new temperature by adjusting their immune output. This acclimation was compensatory as seen by elevated rates of immune output in colder animals and decreased rates of immune output in warmer animals. These results indicate that while temperature change may be a constraint on some animals, S. odoratus have the ability to rapidly adjust immunity to match environmental thermal demand. This rapid ability to adjust immunity may be related to the broad geographic distribution of musk turtles. Future research should focus on how immune acclimation in ectotherms varies both intraspecifically and interspecifically across regional scales and geographic distributions.

Effect of a Punica granatum enriched diet on immunocompetence in Rhinella marina.

Direct ingestion of plant materials has been shown to have immunomodulatory effects on a variety of herbivores. Studies have also shown that compounds ingested indirectly by predators through prey items can affect the general physiology of the ingesting organism. Relatively little data exists, however, concerning the modulation of a predator's immune system via compounds obtained indirectly through prey. In this study, we sought to determine if the immune-stimulating properties of Punica granatum (pomegranate) could be conveyed from a prey organism, Acheta domestica, to a predator, Rhinella marina, through diet specialization. Experimental crickets were fed a diet of agar supplemented with 10 mg/mL of lyophilized, powdered, whole pomegranate while control crickets were fed unadulterated agar. Experimental toads consumed a diet consisting of crickets fed the pomegranate-enriched diet, while control toads consumed a diet consisting of crickets fed the standard agar diet. Blood samples were taken weekly and leukocyte profiles and neutrophil phagocytic activity were determined for all toads over an 8-week period. Complement activity was measured at 6 weeks. Toads fed the pomegranate-enriched diet showed altered leukocyte profiles as evidenced by an increase in circulating eosinophil number and a decrease in the number of circulating lymphocytes, monocytes, and basophils as compared to controls, indicating an immunomodulatory effect of the pomegranate-enhanced diet. These results suggest that pomegranate-derived immunomodulatory compounds can be transferred from prey to predator, and suggests that the flora in the environment where insectivores forage could have a significant effect on the physiology of the animal.

Hand hygiene knowledge of college students.

An observational study was conducted to evaluate hygiene habits of students with fields of study, gender, and understanding of hygiene at a university in Alabama. One hundred students were randomly observed in ten restrooms on campus to determine whether or not students washed their hands. The study was divided into an observational stage, a quiz to ascertain student's knowledge of hygiene and the spread of pathogens, and a survey of self-reported illness rates. Females had a tendency to wash their hands more often than males while visiting the bathroom (p = 0.02, chi2 = 11.6). Science majors were more likely to wash their hands than non-science majors (p < or = 0.001, chi2 = 5.2). Females (p < or = 0.0001, df = 98, F = 21.5) and science majors (p < or = 0.0001, df = 98, F = 81.4) scored significantly higher on the survey than males and nonscience majors, and that those observed not washing their hands reported being sick more often than those observed washing their hands (chi2 = 155.0, df= 3, p < 0.001, Fisher's exact p < 0.001).

Reproductive parameters in female yellow-blotched map turtles (Graptemys flavimaculata) from a historically contaminated site vs. a reference site.

Graptemys flavimaculata, the yellow-blotched map turtle, is a long-lived, threatened, species, endemic to the Pascagoula River drainage in Mississippi. During the 1980s, one branch of the drainage (i.e. the Leaf River) was impacted by effluent from a wood pulp processing plant known to contain endocrine disrupters. A decade later, we examined seasonal reproductive parameters (i.e. monthly plasma estradiol-17beta (E(2)), testosterone (T), vitellogenin (VTG) and follicular development) in adult female turtles from historically polluted and reference sites in the drainage to determine if legacy exposure to pollution impacts reproduction . We found no seasonal patterns in E(2) or T and these patterns did not differ between sites. However, E(2) differed significantly among ovarian stages for the reference, but not pollutant exposed females. A significantly greater percentage of reference site females were able to produce a second clutch than females from the historically polluted site (50% and 17%). Additionally, there was a significant positive correlation between E(2) with VTG levels for reference, but not pollutant exposed females. Body and yolk tissue contaminant analysis indicated that exposure to pollutants is presently minimal and unlikely the cause of the reproductive differences observed between sites; instead, differences are potentially due to exposure history.

Accumulation and depuration of trace metals in southern toads, Bufo terrestris, exposed to coal combustion waste.

Accumulation and depuration of metals by an organism are underrepresented in the literature. We collected southern toads (Bufo terrestris) from coal by-product (ash)-contaminated and uncontaminated sites to examine metal concentrations over time. Toads were placed in four exposure regimes, then sacrificed periodically over a 5-month period, and whole-body metal levels were measured. Toads exposed to ash accumulated significant concentrations of metals. Metal concentrations changed throughout the experiment, and profiles of accumulation and depuration differed depending on the metal and exposure regime. Ash-exposed toads exhibited elevated levels of 11 of 18 metals measured. Increases ranged from 47.5% for Pb to more than 5000% for As. Eight of 18 metals did not change in control toads, while 10 of 18 metals decreased in toads removed from ash, ranging from -25% for Co to -96% for Tl. Seven metals that decreased in toads removed from ash did not change in control toads.

Comparative analysis of Xenopus tropicalis hepcidin I and hepcidin II genes.

Hepcidin is an antimicrobial peptide and an iron-regulatory hormone that is conserved in fish, amphibians, and mammalians. Here we report the genomic and biochemical characterization of two amphibian hepcidins (tHEP1 and tHEP2) from the Western clawed frog (Xenopus tropicalis). Similar to fish and mammalian hepcidins, both tHEP1 and tHEP2 genes contain three exons and two introns. The predicted mature tHEP1 and tHEP2 hepcidins are a 25 amino acid peptide and a 24 amino acid peptide, respectively. Both tHEP1 and tHEP2 are strongly expressed in the liver and kidney, with detectable expression in the heart. In addition, tHEP2 is also moderately expressed in the stomach and testis. The expression of tHEP2 (but not tHEP1) in the liver is strongly induced by iron overloading, while the expression of tHEP1 (but not tHEP2) in the liver is significantly inhibited by corticosterone. Genomic analysis of the promoter regions of these two frog hepcidin genes indicates that transcription regulation factors NF-kappaB and C/EBPbeta may be involved in hepcidin regulation by iron. Hence, X. tropicalis is a useful model for the study of molecular evolution, transcriptional regulation, and structure-activity relationships of vertebrate hepcidins.

Characterization and quantification of corticosteroid-binding globulin in a southern toad, Bufo terrestris, exposed to coal-combustion-waste.

Corticosteroid-binding globulin (CBG) is a plasma protein that binds corticosterone and may regulate access of hormone to tissues. The role of CBG during a stress response is not clear. At least two hypotheses have been proposed: 1) CBG levels may increase in response to a stressor, thereby decreasing the amount of circulating free corticosterone, or 2) CBG levels may decline, making corticosterone available for its role in increased metabolic needs during stress. In this study, southern toads, Bufo terrestris, were exposed to a chronic pollutant (coal-combustion-waste), to determine changes in CBG and free corticosterone levels. Since toads exposed to chronic pollutants in previous studies did not exhibit the predicted changes in metabolic rate and mass, but did experience a significant elevation in total corticosterone, we hypothesized that CBG would likewise increase and thus, mitigate the effects of a chronic (i.e. 2 months) pollutant stressor. To conduct this study, we first characterized the properties of CBG in southern toads. Toad CBG has a K(d)=20.6+/-1.0 nM and a B(max)=332.2+/-5.1 nmol/L plasma. The rank order potencies for steroid inhibition of tritiated corticosterone are: dihydrotestosterone > corticosterone >> progesterone=testosterone >>> estrogen=dexamethasone. After characterization, we monitored the changes in CBG, total corticosterone, and free corticosterone in male toads that were exposed to either coal-combustion-waste or control conditions. CBG increased in all groups throughout the experiment. Total corticosterone, on the other hand, was only significantly elevated at four weeks of exposure to coal-combustion-waste. The increase in CBG did not parallel the increase in total corticosterone; as a result, free corticosterone levels were not buffered by CBG, but showed a peak at four weeks similar to total corticosterone. This finding indicates that, in this species, CBG may not provide a protective mechanism during long-term pollution exposure.

Metabolic measures of male southern toads (Bufo terrestris) exposed to coal combustion waste.

Southern toads (Bufo terrestris) are found in coal fly ash collection basins associated with coal-burning electrical power plants. These basins contain large amounts of trace metals and organisms found in these basins are known to accumulate large quantities of metals. Studies on a variety of organisms exposed to trace metals found that they experience a significant increase in standard metabolic rate. We experimentally exposed southern toads to metal-contaminated sediment and food and measured changes in standard and exercise metabolic rates as well as changes in body, liver and muscle mass, blood glucose, and corticosterone. We found that toads exposed to trace metal contamination gained significantly less mass (18.3 %) than control toads (31.3%) when food was limited and experienced significantly decreased RQ after exercise. However, contaminated toads did not experience changes in standard (x control = 0.114 +/- 0.016 mL O2 g(-1) h(-1); x (ash)=0.109 +/- 0.013 mL O2 g(-1) h(-1), p = 0.08) or exercise metabolic rates (x control = 0.53 +/- 0.06 mL O2 g(-1) h(-1); x ash =0.44 +/- 0.04 mL O2 g(-1) h(-1), p = 0.47) plasma glucose levels (p = 0.6), and hepatic or muscle percentage indices (p > 0.2 in all cases) whether food was limited or not.