Chan Zeng

Epidermal Growth Factor Receptor in Non–Small-Cell Lung Carcinomas: Correlation Between Gene Copy Number and Protein Expression and Impact on Prognosis

PURPOSE The epidermal growth factor receptor (EGFR) is frequently overexpressed in non-small-cell lung carcinoma (NSCLC), and EGFR inhibitors are promising new therapeutic agents. The molecular mechanisms responsible for EGFR overexpression are poorly understood. MATERIALS AND METHODS Gene copy number and protein status of EGFR were investigated in microarrayed tumors from 183 NSCLC patients, including squamous cell carcinoma (SCC; 89 patients) and non-SCC (94 patients) histologies. Protein expression was assessed by immunohistochemistry on a scale from 0 to 400 (percentage of positive cells x staining intensity). Gene and chromosome 7 copy numbers were identified by fluorescent in situ hybridization (FISH). RESULTS EGFR protein overexpression was observed in 62% of the NSCLC (25% scored 201 to 300; 37% scored 301 to 400), more frequently in SCC than non-SCC (82% v 44%; P <.001), and in 80% of the bronchioloalveolar carcinomas. The prevalent FISH patterns were balanced disomy (40%) and trisomy (38%) for EGFR gene and chromosome 7 (40%), whereas balanced polysomy was seen in 13% and gene amplification was seen in 9% of the patients. Gene copy number correlated with protein expression (r = 0.4; P <.001). EGFR overexpression or high gene copy numbers had no significant influence on prognosis. CONCLUSION EGFR overexpression is frequent in NSCLC, is most prominent in SCC, and correlates with increased gene copy number per cell. High gene copy numbers per cell showed a trend toward poor prognosis. It will be important to evaluate EGFR gene and EGFR protein status and signal protein expression to properly interpret future clinical trials using EGFR inhibitors.

Quantitative HOX expression in chromosomally defined subsets of acute myelogenous leukemia.

We used a degenerate RT-PCR screen and subsequent real-time quantitative RT-PCR assays to examine the expression of HOX and TALE-family genes in 34 cases of chromosomally defined AML for which outcome data were available. AMLs with favorable cytogenetic features were associated with low overall HOX gene expression whereas poor prognostic cases had high levels. Characteristically, multiple HOXA family members including HOXA3–HOXA10 were jointly overexpressed in conjunction with HOXB3, HOXB6, MEIS1 and PBX3. Higher levels of expression were also observed in the FAB subtype, AML-M1. Spearmann correlation coefficients indicated that the expression levels for many of these genes were highly inter-related. While we did not detect any significant correlations between HOX expression and complete response rates or age in this limited set of patients, there was a significant correlation between event-free survival and HOXA7 with a trend toward significance for HoxA9, HoxA4 and HoxA5. While patients with elevated HOX expression did worse, there were notable exceptions. Thus, although HOX overexpression and clinical resistance to chemotherapy often coincide, they are not inextricably linked. Our results indicate that quantitative HOX analysis has the potential to add new information to the management of patients with AML, especially where characteristic chromosomal alterations are lacking.

WNT7a induces E-cadherin in lung cancer cells.

E-cadherin loss in cancer is associated with de-differentiation, invasion, and metastasis. Drosophila DE-cadherin is regulated by Wnt/β-catenin signaling, although this has not been demonstrated in mammalian cells. We previously reported that expression of WNT7a, encoded on 3p25, was frequently downregulated in lung cancer, and that loss of E-cadherin or β-catenin was a poor prognostic feature. Here we show that WNT7a both activates E-cadherin expression via a β-catenin specific mechanism in lung cancer cells and is involved in a positive feedback loop. Li+, a GSK3β inhibitor, led to E-cadherin induction in an inositol-independent manner. Similarly, exposure to mWNT7a specifically induced free β-catenin and E-cadherin. Among known transcriptional suppressors of E-cadherin, ZEB1 was uniquely correlated with E-cadherin loss in lung cancer cell lines, and its inhibition by RNA interference resulted in E-cadherin induction. Pharmacologic reversal of E-cadherin and WNT7a losses was achieved with Li+, histone deacetylase inhibition, or in some cases only with combined inhibitors. Our findings provide support that E-cadherin induction by WNT/β-catenin signaling is an evolutionarily conserved pathway operative in lung cancer cells, and that loss of WNT7a expression may be important in lung cancer development or progression by its effects on E-cadherin.

Epidermal growth factor receptor and cyclin D1 are independently amplified and overexpressed in esophageal squamous cell carcinoma

PurposeTo assess the status of EGFR, HER-2, and CCND1 at the gene and protein levels in esophageal squamous cell carcinoma.MethodsDual-color FISH assays were performed using DNA probes for EGFR/CEP 7, HER-2/CEP 17, and CCND1/CEP 11. The respective proteins, furthermore, was assessed in IHC assays and correlated with patient and tumor characteristics.ResultsFrom 55 ESCCs, 8 (15%) tumors showed gene amplification and 20 (36%) had gene overrepresentation (balanced gene and chromosome 7 polysomy) for EGFR. High-level protein expression was frequent (49%), positively correlated with gene copy numbers (kappa=0.4), and associated with well-differentiated histology (p=0.02). For HER-2, gene amplification was detected in a single tumor (2%) and protein overexpression was rare (9%). CCND1 gene was amplified in 23 (42%) tumors; likewise, CCND1 protein overexpression was common (58%) and prevailed in gene overrepresentation or amplification. Only 1 patient showed gene amplification for both EGFR and CCND1. Survival was not associated with EGFR or CCND1 gene/protein status, whereas negative patients for HER-2 protein had a better survival than positive patients (p=0.04).ConclusionsFrequent overexpression and gene amplification of EGFR and CCND1 make these molecules and their pathways potential therapeutic targets for ESCC. In addition, EGFR and CCND1 appeared to be independently altered suggesting alternative mechanisms for pathway activation. Therapeutic agents targeting these molecules are urged to be tested in clinical trials and comprehensive biological analyses should be included to properly interpret the outcome.

Baseline Gene Expression Predicts Sensitivity to Gefitinib in Non–Small Cell Lung Cancer Cell Lines

Tyrosine kinase inhibitors (TKI) of the epidermal growth factor receptor (EGFR) produce objective responses in a minority of patients with advanced-stage non–small cell lung cancer (NSCLC), and about half of all treated patients progress within 6 weeks of instituting therapy. Because the target of these agents is known, it should be possible to develop biological predictors of response, but EGFR protein levels have not been proven useful as a predictor of TKI response in patients and the mechanism of primary resistance is unclear. We used microarray gene expression profiling to uncover a pattern of gene expression associated with sensitivity to EGFR-TKIs by comparing NSCLC cell lines that were either highly sensitive or highly resistant to gefitinib. This sensitivity-associated expression profile was used to predict gefitinib sensitivity in a panel of NSCLC cell lines with known gene expression profiles but unknown gefitinib sensitivity. Gefitinib sensitivity was then determined for members of this test panel, and the microarray-based sensitivity prediction was correct in eight of nine NSCLC cell lines. Gene and protein expression differences were confirmed with a combination of quantitative reverse transcription-PCR, flow cytometry, and immunohistochemistry. This gene expression pattern related to gefitinib sensitivity was independent from sensitivity associated with EGFR mutations. Several genes associated with sensitivity encode proteins involved in HER pathway signaling or pathways that interrelate to the HER signaling pathway. Some of these genes could be targets of pharmacologic interventions to overcome primary resistance. (Mol Cancer Res 2006;4(8):521–8)

Antitumor activity of the epidermal growth factor receptor (EGFR) tyrosine kinase inhibitor gefitinib (ZD1839, Iressa) in non-small cell lung cancer cell lines correlates with gene copy number and EGFR mutations but not EGFR protein levels.

Purpose: Recognition that the epidermal growth factor receptor (EGFR) was a therapeutic target in non–small cell lung cancer (NSCLC) and other cancers led to development of the small-molecule receptor tyrosine kinase inhibitors gefitinib and erlotinib. Clinical trials established that EGFR tyrosine kinase inhibitors produced objective responses in a minority of NSCLC patients. We examined the sensitivity of 23 NSCLC lines with wild-type or mutated EGFR to gefitinib to determine genes/proteins related to sensitivity, including EGFR and HER2 cell surface expression, phosphorylated EGFR expression, EGFR gene copy number, and EGFR mutational status. Downstream cell cycle and signaling events were compared with growth-inhibitory effects. Experimental Design: We determined gefitinib sensitivity by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assays, EGFR expression by fluorescence-activated cell sorting and immunohistochemistry, phosphorylated EGFR by Western blotting, EGFR gene copy number by fluorescence in situ hybridization, and EGFR mutation by sequencing. The cellular effects of gefitinib on cell cycle were determined by flow cytometry and the molecular effects of gefitinib EGFR inhibition on downstream signal proteins by Western blotting. Gefitinib in vivo effects were evaluated in athymic nude mice bearing sensitive and resistant NSCLC xenografts. Results: There was a significant correlation between EGFR gene copy number, EGFR gene mutations, and gefitinib sensitivity. EGFR protein was necessary but not sufficient for predicting sensitivity. Gefitinib-sensitive lines showed a G1 cell cycle arrest and inactivation of downstream signaling proteins; resistant cell lines had no changes. The in vivo effects mirrored the in vitro effects. Conclusions: This panel of NSCLC lines characterized for gefitinib response was used to identify predictive molecular markers of response to gefitinib. Several of these have subsequently been shown to identify NSCLC patients likely to benefit from gefitinib therapy.

HOX expression patterns identify a common signature for favorable AML.

Deregulated HOX expression, by chromosomal translocations and myeloid-lymphoid leukemia (MLL) rearrangements, is causal in some types of leukemia. Using real-time reverse transcription-PCR, we examined the expression of 43 clustered HOX, polycomb, MLL and FLT3 genes in 119 newly diagnosed adult acute myeloid leukemias (AMLs) selected from all major cytogenetic groups. Downregulated HOX expression was a consistent feature of favorable AMLs and, among these cases, inv(16) cases had a distinct expression profile. Using a 17-gene predictor in 44 additional samples, we observed a 94.7% specificity for classifying favorable vs intermediate/unfavorable cytogenetic groups. Among other AMLs, HOX overexpression was associated with nucleophosmin (NPM) mutations and we also identified a phenotypically similar subset with wt-NPM. In many unfavorable and other intermediate cytogenetic AMLs, HOX levels resembled those in normal CD34+ cells, except that the homogeneity characteristic of normal samples was not present. We also observed that HOXA9 levels were significantly inversely correlated with survival and that BMI-1 was overexpressed in cases with 11q23 rearrangements, suggesting that p19ARF suppression may be involved in MLL-associated leukemia. These results underscore the close relationship between HOX expression patterns and certain forms of AML and emphasize the need to determine whether these differences play a role in the disease process.

Chromosomal abnormalities in non-small cell lung carcinomas and in bronchial epithelia of high-risk smokers detected by multi-target interphase fluorescence in situ hybridization.

Human lung carcinogenesis is accompanied by complex chromosomal changes that may be detected in interphase cells by fluorescence in situ hybridization (FISH) assay using recently developed multitarget DNA probes. Touch preparations of 20 non-small cell lung carcinomas, sputum specimens from 3 patients with lung cancer and from 11 ex-smokers without lung cancer, and cultured benign bronchial epithelium of 42 high-risk smokers, 9 of whom had concurrent invasive carcinoma, were tested using a four-color FISH probe (LAVysion) targeting centromere 6, 5p15.2, 7p12 (EGFR), and 8q24 (MYC). Significantly high frequencies of abnormal cells were found in each of the 20 NSCLC (100%) and in the 3 sputum specimens from lung cancer patients. None of the cytologically normal sputa contained FISH abnormalities. Cultured bronchial epithelial cells from 11 of 42 patients (26%) were abnormal for at least one probe. Abnormal FISH patterns had no association with gender, presence of tumor or histology. Multicolor FISH can readily detect chromosomal abnormalities in imprints and sputa from lung carcinomas. Chromosomal aneusomy is also frequent in bronchial epithelial cells from long-term smokers. The prognostic significance of the multicolor LAVysion FISH probe set should be validated in a controlled clinical trial.

The TRC8 hereditary kidney cancer gene suppresses growth and functions with VHL in a common pathway

VHL is part of an SCF related E3-ubiquitin ligase complex with ‘gatekeeper’ function in renal carcinoma. However, no mutations have been identified in VHL interacting proteins in wild type VHL tumors. We previously reported that the TRC8 gene was interrupted by a t(3;8) translocation in a family with hereditary renal and non-medullary thyroid cancer. TRC8 encodes a multi-membrane spanning protein containing a RING-H2 finger with in vitro ubiquitin ligase activity. We isolated the Drosophila homologue, DTrc8, and studied its function by genetic manipulations and a yeast 2-hybrid screen. Human and Drosophila TRC8 proteins localize to the endoplasmic reticulum. Loss of either DTrc8 or DVhl resulted in an identical ventral midline defect. Direct interaction between DTrc8 and DVhl was confirmed by GST-pulldown and co-immunoprecipitation experiments. CSN-5/JAB1 is a component of the COP9 signalosome, recently shown to regulate SCF function. We found that DTrc8 physically interacts with CSN-5 and that human JAB1 localization is dependent on VHL mutant status. Lastly, overexpression of DTrc8 inhibited growth consistent with its presumed role as a tumor suppressor gene. Thus, VHL, TRC8, and JAB1 appear to be linked both physically and functionally and all three may participate in the development of kidney cancer.

Hox expression in AML identifies a distinct subset of patients with intermediate cytogenetics

We previously reported that favorable and poor prognostic chromosomal rearrangements in acute myeloid leukemia (AML) were associated with distinct levels of HOX expression. We have now analyzed HOX expression in 50 independent adult AML patients (median age=62 years), together with FLT3 and FLT3-ligand mRNA levels, and FLT3 mutation determination. By cluster analysis, we could divide AMLs into cases with low, intermediate and high HOX expression. Cases with high expression were uniquely restricted to a subset of AMLs with intermediate cytogenetics (P=0.0174). This subset has significantly higher levels of FLT3 expression and appears to have an increase of FLT3 mutations (44%), while CEBPα mutations were infrequent (6%). FLT3 mRNA levels were correlated with the expression of multiple HOX genes, whereas FLT3 mutations were correlated with HOXB3. In some cases, FLT3 was expressed at levels equivalent to GAPDH in the absence of genomic amplification. We propose that high HOX expression may be characteristically associated with a distinct biologic subset of AML. The apparent global upregulation of HOX expression could be due to growth-factor signaling or, alternatively, these patterns may reflect a particular stage of differentiation of the leukemic cells.