Background: It has been reported that KRAS mutations (and to a lesser extent KRAS mutations with the BRAF V600E mutation) negatively affect response to anti-epidermal growth factor receptor (EGFR) ...mAbs in metastatic colorectal cancer (mCRC) patients, while the biological impact of the EGFR pathway represented by PI3K/PTEN/AKT on anti-EGFR treatment is still not clear.
Patients and methods: We analysed formalin-fixed samples from a cohort of 32 mCRC patients treated with cetuximab by means of EGFR immunohistochemistry, EGFR and PTEN FISH analysis, and KRAS, BRAF, PI3KCA, and PTEN genomic sequencing.
Results: Ten (31%) of 32 patients showed a partial response to cetuximab and 22 (69%) did not nonresponder (NR). EGFR immunophenotype and FISH-based gene status did not predict an anti-EGFR mAb response, whereas KRAS mutations (24%) and PI3K pathway activation, by means of PI3KCA mutations (13%) or PTEN mutation (10%)/loss (13%), were significantly restricted to, respectively, 41% and 37% of NRs.
Conclusion: These findings suggested that KRAS mutations and PI3KCA/PTEN deregulation significantly correlate with resistance to cetuximab. In line with this, patients carrying KRAS mutations or with activated PI3K profiles can benefit from targeted treatments only by switching off molecules belonging to the downstream signalling of activated EGFR, such as mammalian target of rapamycin.
Summary EGFR overexpression in salivary gland carcinomas provides the rational for the investigation of anti-EGFR treatments in recurrent and/or metastatic salivary gland cancers (RMSGCs). The ...activity of cetuximab in terms of clinical benefit rate (CBR) defined as the occurrence of objective response (CR or PR) or stable disease (SD) for ⩾6 months was investigated. From April to December 2005, 30 patients 23 adenoid cystic carcinoma (ACC) and 7 non-ACC were treated with cetuximab at 400 mg/m2 /week followed by 250 mg/m2 /week until progression, major toxicity or voluntary discontinuation. EGFR expression and gene status were retrospectively analyzed by immunocytochemistry and fluorescence in situ hybridization, respectively. A median of 14 courses of cetuximab (range 5–54) were infused. Skin toxicity was the main adverse event. Cetuximab provides a CBR in 50% (95% CL, 31 to 69%) of cases. None tumor sample showed EGFR gene amplification and an increased EGFR copy number was observed in 12% of samples, all ACC. Skin rash ⩾G2, EGFR overexpression and EGFR copy number were not statistically correlated to CB. In RMSGCs further evaluations of EGFR targeting agents are advisable and should take place by appropriate tumor biological selection, differentiating ACC from non-ACC.
We have previously demonstrated that chordomas express activated platelet-derived growth factor receptor (PDGFRB) and that treatment with imatinib, which is capable of switching off the activation of ...various receptor tyrosine kinases (RTKs) including PDGFRB, benefits a number of patients. The aim of this study was to identify the possible presence of other activated RTKs and their downstream signaling effectors. Cryopreserved material from 22 naïve sporadic chordomas was investigated for the presence of activated RTKs and their cognate ligands and downstream signaling effectors by means of human phospho-RTK antibody arrays, Western blotting, and molecular analysis; immunohistochemistry and fluorescence in situ hybridization were used to analyze the corresponding formalin-fixed and paraffin-embedded samples. We detected activated PDGFRB, FLT3, and colony stimulating factor 1 receptor (CSF1R) of the PDGFR family and highly phosphorylated EGFR, HER2/neu, and (to a lesser extent) HER4 of the EGFR family. The detection of PDGFRB/PDGFB confirmed our previous data. The presence of activated EGFR was paralleled by the finding of high levels of epidermal growth factor (EGF) and transforming growth factor (TGF ) and PDGFB co-expression and PDGFRB co-immunoprecipitation. Of the downstream effectors, the PI3K/AKT and RAS/MAPK pathways were both activated, thus leading to the phosphorylation of mammalian target of rapamycin (mTOR) and 4E-BP1 among the regulators involved in translational control. Taken together, our results (i) provide a rationale for tailored treatments targeting upstream activated receptors, including the PDGFR and EGFR families; (ii) support the idea that a combination of upstream antagonists and mTOR inhibitors enhances the control of tumor growth; and (iii) indicate that the 4E-BP1/eIF4E pathway is a major regulator of protein synthesis in chordoma.
Purpose
Creatine belongs to a buffering system of cellular ATP level and has been reported to display direct antioxidant activity. Aim of this work was to investigate whether creatine treatment could ...ameliorate the antioxidant response of intestinal cells and limit the oxidative injury induced by anoxia and subsequent reoxygenation.
Methods
Jejunal and ileal tracts of rat intestine were everted and incubated in vitro under normoxic, anoxic and reoxygenation conditions in the absence and in the presence of 10 mM creatine. (Na
+
, K
+
)-ATPase, γ-GT and antioxidant enzymes activities were determined in mucosal homogenate, as well as malondialdehyde production and HSP70 expression.
Results
Both in jejunum and ileum, creatine treatment increases (Na
+
, K
+
)-ATPase activity; γ-GT is unaffected in jejunum but stimulated in ileum. In both tissues, creatine does not alter the antioxidant activities or malondialdehyde level. HSP70 expression is increased only in jejunum. Anoxic conditions stimulate antioxidant activities to a greater extent in jejunum compared to ileum; reoxygenation does not evoke further effects, but enhances malondialdehyde production in both tracts. The protective action of creatine, in reoxygenation, is more marked in jejunum as for its stimulation of antioxidant activities; however, in jejunum, a prooxidant action of creatine is suggested, since malondialdehyde production is enhanced by its presence; on the contrary in ileum, where HSP70 is overexpressed in reoxygenation, peroxidation level is significantly reduced.
Conclusions
The presence of creatine seems to potentiate the defensive response of both tissues, in jejunum by means of cell antioxidant equipment, in ileum by the involvement of HSP70.
Mounting evidence suggests that recurrence of resected head and neck squamous cell carcinomas (HNSCCs) is due to the outgrowth of unrecognized residual tumor cells as well as to the premalignant ...and/or precursor-field epithelial cells. We studied the impact of processes triggered by HNSCC surgery in stimulating both residual tumor cells demonstrated to overexpress epidermal growth factor receptor (EGFR), and premalignant cells surrounding the resected lesion.
EGFR expression/activation by immunohistochemistry/biochemistry and gene status by FISH were investigated in 23 primary HNSCCs and surrounding tissues. The ability to induce cell proliferation of wound healing drainages collected from 12 relapsed and 11 not relapsed patients was evaluated by a colorimetric assay in squamous cell carcinoma cell lines A431 (carrying EGFR amplification) and CAL27 (carrying three EGFR copies) in the presence/absence of EGFR therapeutic inhibitors.
Primary tumors showed intermediate/high EGFR expression (91%), EGFR phosphorylation and EGFR-positive FISH (35%). Normal, metaplastic and dysplastic epithelium surrounding the resected tumor displayed EGFR overexpression. EGFR activation and gene amplification were observed in normal and dysplastic epithelium, respectively. Each tested wound healing drainage induced the cells to proliferate and the proliferation was significantly higher in relapsed compared with not relapsed HNSCC patients (P = 0.02 and P = 0.03). Anti-EGFR treatments inhibited the drainage-induced proliferation, with the highest inhibitory efficiency by cetuximab on A431 cells, while CAL27 cell growth was more efficiently inhibited by tyrosine kinase inhibitors.
Surgery could favor the proliferation of cells showing EGFR overexpression/activation/amplification such as residual tumor cells and/or precursor-field epithelial cells already present after surgery. Treatment with anti-EGFR reagents inhibits wound-induced stimulation, according to the EGFR family status.
The mechanism of the intestinal creatine absorption is not well understood. Previous studies have established the involvement of a CT1 carrier system in jejunal apical membrane. The current research ...was aimed at completing the picture of creatine absorption. To investigate the process supporting creatine exit from enterocyte, basolateral membrane vesicles isolated from rat jejunum were used. The presence of various symport and antiport mechanisms was searched and a NaCl-dependent electrogenic transport system for creatine was evidenced, which shares some functional and kinetic features with the apical CT1. However, Western blot and immunohistochemical experiments ruled out the presence of a CT1 transporter in the basolateral membrane. Further studies are required to identify the basolateral transport mechanism. However, in the in vivo conditions, the NaCl gradient is inwardly directed, therefore such a mechanism cannot energetically mediate the exit of creatine from the cell into the blood during the absorptive process, but rather it may drive creatine into the enterocyte. To shed more light on the creatine absorption process, a possible creatine movement through the paracellular pathway has been examined using the jejunal tract everted and incubated in vitro. A linear relationship between creatine transport and concentration was apparent both in the mucosa-to-serosa and serosa-to-mucosa directions and the difference between the two slopes suggests that paracellular creatine movement by solvent drag may account for transintestinal creatine absorption. As a matter of fact, when transepithelial water flux is reduced by means of a mucosal hypertonic solution, the opposite creatine fluxes tend to overlap. The findings of the present study suggest that paracellular creatine movement by solvent drag may account for transintestinal creatine absorption.
1 Observatoire Océanologique
Européen, Centre Scientifique de Monaco, MC-98000 Monaco,
Principality of Monaco; 2 Laboratoire de
Physiologie et Toxicologie Environnementales, Faculté des
Sciences, ...Université de Nice Sophia Antipolis, F-0608 Nice cedex,
France; and 3 Dipartimento Fisiologia e
Biochimica Generale, I-20100 Milano, Italy
Symbiotic
cnidarians absorb inorganic carbon from seawater to supply
intracellular dinoflagellates with CO 2 for their
photosynthesis. To determine the mechanism of inorganic carbon
transport by animal cells, we used plasma membrane vesicles prepared
from ectodermal cells isolated from tentacles of the sea anemone,
Anemonia viridis . H 14 CO 3 uptake in the
presence of an outward NaCl gradient or inward H + gradient,
showed no evidence for a Cl - or H + -
driven HCO 3 transport.
H 14 CO 3 and
36 Cl uptakes were stimulated by a
positive inside-membrane diffusion potential, suggesting the presence
of HCO 3 and Cl
conductances. A carbonic anhydrase (CA) activity was measured on plasma
membrane (4%) and in the cytoplasm of the ectodermal cells (96%) and
was sensitive to acetazolamide (IC 50 = 20 nM) and
ethoxyzolamide (IC 50 = 2.5 nM). A strong DIDS-sensitive
H + -ATPase activity was observed (IC 50 = 14 µM). This activity was also highly sensitive to vanadate and allyl
isothiocyanate, two inhibitors of P-type H + -ATPases.
Present data suggest that HCO 3
absorption by ectodermal cells is carried out by H +
secretion by H + -ATPase, resulting in the formation of
carbonic acid in the surrounding seawater, which is quickly dehydrated
into CO 2 by a membrane-bound CA. CO 2 then
diffuses passively into the cell where it is hydrated in
HCO 3 by a cytosolic CA.
symbiosis; anthozoan; sea anemone; HCO 3 transport; carbon-concentrating
mechanism
Although ergogenic effects and health benefits have been reported for creatine used as nutritional supplement, to date little is known about the mechanism of creatine absorption in the small ...intestine. Thus the current study was undertaken to elucidate the mechanism of creatine intake in rat jejunum with the use of well-purified brush border membrane vesicles, isolated from jejunal enterocyte. Creatine uptake was found markedly stimulated by inwardly directed Na(+) and Cl(- )gradients, potential-sensitive, strongly reduced by the substitution of Na(+) and Cl(-) with various cations and anions and positively affected by intravesicular K(+). Moreover, creatine uptake is: 1) significantly inhibited by creatine structural analogs, 2) abolished by low concentrations of 2-aminoethyl methanethiosulfonate hydrobromide (MTSEA), 3) saturable as a function of creatine concentration with an apparent Michaelis-Menten constant of 24.08 +/- 0.80 muM and a maximal velocity of 391.30 +/- 6.19 pmoles mg protein(-1) 30 s(-1). The transport is electrogenic since at least two Na(+) and one Cl(-) are required to transport one creatine molecule. Western blot analysis showed the same amount of creatine transport protein in the jejunal apical membrane when compared to ileum. Thus, these data demonstrate the existence of a Na(+)- and Cl(-)-dependent, membrane potential-sensitive, electrogenic carrier-mediated mechanism for creatine absorption in rat jejunal apical membrane vesicles, which is biochemically and pharmacologically similar to those observed in other tissues. However, in other cell types the stimulatory effect of intravesicular K(+) was never detected.
PDF
