Cellular and Tumor Radiosensitivity is Correlated to Epidermal Growth Factor Receptor Protein Expression Level in Tumors Without EGFR Amplification
ABSTRACT There is conflicting evidence for whether the expression of epidermal growth factor receptor in human tumors can be used as a marker of radioresponse. Therefore, this association was studied in a systematic manner using squamous cell carcinoma (SCC) cell lines grown as cell cultures and xenografts.
The study was performed with 24 tumor cell lines of different tumor types, including 10 SCC lines, which were also investigated as xenografts on nude mice. Egfr gene dose and the length of CA-repeats in intron 1 were determined by polymerase chain reaction, protein expression in vitro by Western blot and in vivo by enzyme-linked immunosorbent assay, and radiosensitivity in vitro by colony formation. Data were correlated with previously published tumor control dose 50% data after fractionated irradiation of xenografts of the 10 SCC.
EGFR protein expression varies considerably, with most tumor cell lines showing moderate and only few showing pronounced upregulation. EGFR upregulation could only be attributed to massive gene amplification in the latter. In the case of little or no amplification, in vitro EGFR expression correlated with both cellular and tumor radioresponse. In vivo EGFR expression did not show this correlation.
Local tumor control after the fractionated irradiation of tumors with little or no gene amplification seems to be dependent on in vitro EGFR via its effect on cellular radiosensitivity.
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ABSTRACT: Epidermal growth factor receptor (EGFR) overexpression is associated with poor prognosis in head and neck squamous cell carcinoma (HNSCC). Despite intensive biomarker studies, a consensual method for assessing EGFR protein expression is still lacking. Here we set out to compare three EGFR detection methods in tumor specimens from HNSCC patients. Tumors were prospectively excised from a series of 79 high-risk HNSCC patients enrolled in a GORTEC-sponsored clinical trial. EGFR expression was determined using a ligand-binding assay on membranes, Western blotting (WB) on membranes and total homogenates, and immunohistochemistry (IHC) on tissue microarrays. In addition, phosphorylated EGFR (pEGFR) was measured by WB on membranes. Distributions and ranges of tumor EGFR expression were method dependent. Moderate positive correlations (Spearman coefficient r ≈ 0.50) were observed between EGFR expression measured by the binding assay and WB or IHC. pEGFR levels positively and significantly correlated with total EGFR expression measured by WB or ligand binding, but not by IHC. The highest correlation (r = 0.85) was observed between EGFR and pEGFR levels, both measured by WB on membranes. Interestingly, the fraction of phosphorylated receptor (pEGFR/EGFR both measured by WB on membranes) significantly declined with increasing tumor EGFR expression, by all assessment methods used. This study shows significant correlations between EGFR detection methods. The observed relationships between EGFR and pEGFR indicate that high-throughput pEGFR/EGFR analyses merit further investigations and consideration for routine use in patient samples.Clinical Cancer Research 03/2012; 18(5):1313-22. DOI:10.1158/1078-0432.CCR-11-2339
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ABSTRACT: MicroRNA (miRNA) influences carcinogenesis at multiple stages and it can effectively control tumor radiosensitivity by affecting DNA damage repair, cell cycle checkpoint, apoptosis, radio-related signal transduction pathways and tumor microenvironment. MiRNA also efficiently modulates tumor radiosensitivity at multiple levels by blocking the two essential non-homologous end-joining repair and homologous recombination repair pathways in the DNA damage response. It interferes with four radio-related pathways in ionizing radiation, including the PI3-K/Akt, NF-κB, MAPK and TGFβ signaling pathways. Moreover, the regulatory effect of miRNA in radiosensitivity can be enhanced when interacting with various key molecules, including H2AX, BRCA1, ATM, DNA-PK, RAD51, Chk1, Cdc25A, p53, PLK1, HIF-1 and VEGF, which are involved in these processes. Therefore, thoroughly understanding the mechanism of miRNA in tumor radiosensitivity could assist in finding novel targets to improve the radiotherapeutic effects and provide new clinical perspectives and insights for developing effective cancer treatments.Carcinogenesis 07/2012; 33(11). DOI:10.1093/carcin/bgs235
- Strahlentherapie und Onkologie 08/2012; 188. DOI:10.1007/s00066-012-0204-2