Purpose:The epidermal growth factor receptor (EGFR) autocrine signaling pathway is involved in cancer development and progression. EGFR inhibitors such as C225 (cetuximab), a chimeric human-mouse anti-EGFR monoclonal antibody, and ZD1839 (gefitinib), a small molecule EGFR-selective tyrosine kinase inhibitor, are in advanced clinical development. The potential emergence of cancer cell resistance in EGFR-expressing cancers treated with EGFR inhibitors could determine lack of activity of these drugs in some cancer patients. Vascular endothelial growth factor (VEGF) is secreted by cancer cells and plays a key role in the regulation of tumor-induced endothelial cell proliferation and permeability. ZD6474 is a small molecule VEGF flk-1/KDR (VEGFR-2) tyrosine kinase inhibitor that also demonstrates inhibitory activity against EGFR tyrosine kinase.Experimental Design: The antitumor activity of ZD1839, C225, and ZD6474 was tested in athymic mice bearing human GEO colon cancer xenografts. GEO cell lines resistant to EGFR inhibitors were established from GEO xenografts growing in mice treated chronically with ZD1839 or C225. Expression of EGFR was evaluated by flow cytometry. Expression of various proteins involved in intracellular cell signaling was assessed by Western blotting. Tumor growth data were evaluated for statistical significance using the Student's t test. All Ps were two-sided.Results: Although chronic administration of optimal doses of C225 or ZD1839 efficiently blocked GEO tumor growth in the majority of mice, tumors slowly started to grow within 80 -90 days, despite continuous treatment. In contrast, continuous treatment of mice bearing established GEO xenografts with ZD6474 resulted in efficient tumor growth inhibition for the entire duration of dosing (up to 150 days). ZD6474 activity was also determined in mice pretreated with ZD1839 or C225. When GEO growth was apparent after 4 weeks of treatment with EGFR inhibitors, mice were either re-treated with EGFR inhibitors or treated with ZD6474. GEO tumor growth was blocked only in mice treated with ZD6474, whereas tumor progression was observed in mice re-treated with C225 or ZD1839. GEO tumors growing during treatment with C225 or with ZD1839 were established as cell lines (GEO-C225-RES and GEO-ZD1839-RES, respectively). Cell membrane-associated EGFR expression was only slightly reduced in these cell lines compared with parental GEO cells. Western blotting revealed no major change in the expression of the EGFR ligand transforming growth factor ␣ of bcl-2, bcl-xL, p53, p27, MDM-2, akt, activated phospho-akt, or mitogen-activated protein kinase. However, both GEO-C225-RES and GEO-ZD1839-RES cells exhibited a 5-10-fold increase in activated phospho-mitogen-activated protein kinase and in the expression of cyclooxygenase-2 and of VEGF compared with GEO cells. GEO-C225-RES and GEO-ZD1839-RES growth as xenografts in nude mice was not significantly affected by treatment with either C225 or ZD1839 but was efficiently inhibited by ZD6474.Conclusions: Long-t...

We have examined the possible mechanisms of resistance to the epidermal growth factor receptor (EGFR) inhibitors in tumor cells with variable levels of EGFR. ZD1839 (Iressa) is a small-molecular-weight, ATP-mimetic that specifically inhibits the EGFR tyrosine kinase. A431 cell growth was markedly inhibited by ZD1839 (IC 50 p0.1 lm) whereas the MDA-468 cells were relatively resistant (IC 50 >2 lm). Low doses of ZD1839 delayed cell cycle progression and induced apoptosis in A431 cells but not in MDA-468 cells. In both cell lines, 0.1 lm ZD1839 eliminated EGFR phosphorylation. However, the basal activity of the phosphatidylinositol-3 kinase (PI3 K) target Akt was eliminated in A431 but not in MDA-468 cells, implying that their Akt activity is independent of EGFR signals. A431 cells express PTEN/MMAC1/TEP, a phosphatase that can dephosphorylate position D3 of phosphatidylinositol-3,4,5 trisphosphate, the site that recruits the plecstrin-homology domain of Akt to the cell membrane. On the contrary, MDA-468 cells lack the phosphatase and tensin homolog (PTEN), potentially setting Akt activity at a high threshold that is unresponsive to EGFR inhibition alone. Therefore, we reintroduced (PTEN) by retroviral infection in MDA-468 cells. In MDA-468/PTEN but not in vector controls, treatment with ZD1839 inhibited P-Akt levels, induced relocalization of the Forkhead factor FKHRL1 to the cell nucleus, and increased FKHRL1-dependent transcriptional activity. ZD1839 induced a greater degree of apoptosis and cell cycle delay in PTEN-reconstituted than in control cells. These data suggest that loss of PTEN, by permitting a high level of Akt activity independent of receptor tyrosine kinase inputs, can temporally dissociate the inhibition of the EGFR with that of Akt induced by EGFR inhibitors. Thus, in EGFR-expressing tumor cells with concomitant amplification(s) of PI3K-Akt signaling, combined blockade of the EGFR tyrosine kinase and Akt should be considered as a therapeutic approach.

SUMMARYBackground: Although bowel ultrasound is a widely accepted diagnostic tool in bowel diseases, its value as the primary imaging procedure in patients with symptoms/signs suggestive of inflammatory bowel disorders is still unclear. Aim: To investigate the accuracy of bowel ultrasound compared with barium X-ray studies, computed tomography, endoscopy and bowel surgery in the initial assessment of inflammatory bowel disorders. Methods: Four hundred and eighty-seven patients hospitalized consecutively for symptoms or signs suggestive of a bowel disorder between December 1999 and March 2002 were initially enrolled in the study. All patients underwent bowel ultrasound as the first imaging procedure within 36 h of admission; radiographic evaluations, endoscopy and/or surgery were then performed as appropriate and the results of these investigations were used as the gold standard. Results: Three hundred and thirty-six patients had pathological findings of the bowel detectable at

Background/Aim: Although ultrasound (US) has proved to be useful in intestinal diseases, barium enteroclysis (BE) remains the gold standard technique for assessing patients with small bowel Crohn's disease (CD). The ingestion of anechoic non-absorbable solutions has been recently proposed in order to distend intestinal loops and improve small bowel visualisation. The authors' aim was to evaluate the accuracy of oral contrast US in finding CD lesions, assessing their extent within the bowel, and detecting luminal complications, compared with BE and ileocolonoscopy. Methods: 102 consecutive patients with proven CD, having undergone complete x ray and endoscopic evaluation, were enrolled in the study. Each US examination, before and after the ingestion of a polyethylene glycol (PEG) solution (500-800 ml), was performed independently by two sonographers unaware of the results of other diagnostic procedures. The accuracy of conventional and contrast enhanced US in detecting CD lesions and luminal complications, as well as the extent of bowel involvement, were determined. Interobserver agreement between sonographers with both US techniques was also estimated. Results: After oral contrast, satisfactory distension of the intestinal lumen was obtained in all patients, with a mean time to reach the terminal ileum of 31.4 (SD 10.9) minutes. Overall sensitivity of conventional and oral contrast US in detecting CD lesions were 91.4% and 96.1%, respectively. The correlation coefficient between US and x ray extent of ileal disease was r 1 = 0.83 (p,0.001) before and r 2 = 0.94 (p,0.001) after PEG ingestion; r 1 versus r 2 p,0.01. Sensitivity in detecting strictures was 74% for conventional US and 89% for contrast US. Overall interobserver agreement for bowel wall thickness and disease location within the small bowel was already good before but significantly improved after PEG ingestion. Conclusions: Oral contrast bowel US is comparable with BE in defining anatomic location and extension of CD and superior to conventional US in detecting luminal complications, as well as reducing interobserver variability between sonographers. It may be therefore regarded as the first imaging procedure in the diagnostic work up and follow up of small intestine CD.

Purpose: Although cetuximab, an anti-EGF receptor (EGFR) monoclonal antibody, is an effective treatment for patients with KRAS wild-type metastatic colorectal cancer (mCRC), its clinical use is limited by onset of resistance.Experimental Design: We characterized two colorectal cancer models to study the mechanisms of acquired resistance to cetuximab.Results: Following chronic treatment of nude mice bearing cetuximab-sensitive human GEO colon xenografts, cetuximab-resistant GEO (GEO-CR) cells were obtained. In GEO-CR cells, proliferation and survival signals were constitutively active despite EGFR inhibition by cetuximab treatment. Whole gene expression profiling identified a series of genes involved in the hepatocyte growth factor (HGF)-MET-dependent pathways, whichwere upregulated in GEO-CR cells.Furthermore,activated, phosphorylated MET was detected in GEO-CR cells. A second colorectal cancer cell line with acquired resistance to cetuximab was obtained (SW48-CR). Inhibition of MET expression by siRNA restored cetuximab sensitivity in GEO-CR and SW48-CR cells, whereas exogenousactivation ofMETbyHGFstimulationin cetuximab-sensitiveGEOandSW48cells inducedresistance to cetuximab. Treatment of GEO-CR and SW48-CR cells with PHA665752, a selective MET inhibitor, inhibited cell growth, proliferation, and survival signals and impaired cancer cell migration. Overexpression of TGF-a, a specific EGFR ligand, was involved in the acquisition of cetuximab resistance in GEO-CR and SW48-CR cells. In fact, TGF-a overexpression induced the EGFR-MET interaction, with subsequent MET phosphorylation and activation of MET downstream effectors in GEO-CR and SW48-CR cells.Conclusions: These results suggest that overexpression of TGF-a through induction of EGFR-MET interaction contributes to cetuximab resistance in colorectal cancer cells. The combined inhibition of EGFR and MET receptor could represent a strategy for preventing and/or overcoming cetuximab resistance in patients with colorectal cancer.

We report an increased response rate without changes in QoL and a similar overall survival, time to progression, and time to treatment failure for the GC when compared with the MIC regimen in the treatment of advanced NSCLC.

Background and aim: Despite the fact that bowel ultrasound (US) has recently been proved to be useful in the assessment of bowel diseases, uncertainty persists as to its diagnostic role in patients with complicated Crohn's disease (CD). Therefore, we have prospectively investigated the accuracy of US compared with x ray procedures and intraoperative findings in detecting small bowel strictures complicating CD as well as its reliability in assessing disease extent and location within the bowel. Methods: A series of 296 consecutive patients with proven CD admitted to L Sacco University Hospital between 1997 and 1999, having undergone complete radiographic evaluation (including small bowel x ray, colonoscopy, or double contrast barium enema), were enrolled in the study. Bowel US was performed in each patient by two experienced operators unaware of the results of other diagnostic procedures. The accuracy of US in detecting strictures compared with x ray studies was determined separately in two different groups of patients: 211 patients treated conservatively (non-operative CD) and 85 patients who were candidates for surgery for CD complications or unresponsiveness to medical therapy (operative CD). Results: Overall sensitivity and specificity of US in assessing the anatomical distribution of CD were 93% and 97%, respectively. The extent of ileal disease measured at US correlated well with that determined by x ray (r=0.52, p<0.001) in medically treated patients as well as with that measured intraoperatively in surgical patients (r=0.64, p<0.001). One or more stenoses were detected in 75 patients (35.5%) at small bowel enteroclysis in the non-operative CD group compared with 70 (82%) in the operative CD series. Sensitivity, specificity, and positive predictive values of bowel US in the detection of strictures were 79%, 98%, and 95% in non-operative CD patients and 90%, 100%, and 100% in operative CD cases, respectively. Conclusions: In experienced hands, bowel US is an accurate technique for assessing CD extent and location and is very helpful in detecting small bowel strictures, especially in very severe cases that are candidates for surgery. The use of bowel US is therefore justified as a primary investigation in CD patients in whom complications are suspected.

Purpose: Resistance to tyrosine kinase inhibitors (TKI) of EGF receptor (EGFR) is often related to activation of other signaling pathways and evolution through a mesenchymal phenotype.Experimental Design: Because the Hedgehog (Hh) pathway has emerged as an important mediator of epithelial-to-mesenchymal transition (EMT), we studied the activation of Hh signaling in models of EGFR-TKIs intrinsic or acquired resistance from both EGFR-mutated and wild-type (WT) non-small cell lung cancer (NSCLC) cell lines.Results: Activation of the Hh pathway was found in both models of EGFR-mutated and EGFR-WT NSCLC cell line resistant to EGFRTKIs. In EGFR-mutated HCC827-GR cells, we found SMO (the Hh receptor) gene amplification, MET activation, and the functional interaction of these two signaling pathways. In HCC827-GR cells, inhibition of SMO or downregulation of GLI1 (the most important Hh-induced transcription factor) expression in combination with MET inhibition exerted significant antitumor activity.In EGFR-WT NSCLC cell lines resistant to EGFR inhibitors, the combined inhibition of SMO and EGFR exerted a strong antiproliferative activity with a complete inhibition of PI3K/Akt and MAPK phosphorylation. In addition, the inhibition of SMO by the use of LDE225 sensitizes EGFR-WT NSCLC cells to standard chemotherapy.Conclusions:This result supports the role of the Hh pathway in mediating resistance to anti-EGFR-TKIs through the induction of EMT and suggests new opportunities to design new treatment strategies in lung cancer.