nt signals are distributed over fewer peaks. In cases with poor DNA quality, this is also immediately apparent from much lower or even missing peaks. Although not used in this work, it is possible to repeat the mutation assay with a single probe when one doubts the result, further info for instance when the presumed mutant peak is very small. For analysis of all the mutations by sequencing one would have to perform independent PCRs for the 7 exons, followed by 14 bi-directional sequencing reactions. In the mutation assays two multiplex PCRs for 3 and 4 exons, respectively, are followed by two multiplex detection assays and two electrophoresis runs on the sequencer. Besides being considerably cheaper (�7 compared to �60), less DNA is needed and the assays are less labor intensive.

We conclude that these assays provide a simple and inexpensive companion diagnostic for the selection of CRC patients for anti-EGFR therapy. The assays may also be of use for selection of patients with ERBB2 positive breast cancer or non-small cell lung cancer carrying EGFR mutations. Supporting Information Table S1 Primer sequences for multiplex PCR. (0.02 MB XLS) Click here for additional data file.(19K, xls) Table S2 Overview of the probes used and indication of the peak color that correlates with each mutation. (0.02 MB XLS) Click here for additional data file.(22K, xls) Table S3 Detailed overview of the results of sequencing and mutation assays. (0.06 MB XLS) Click here for additional data file.(58K, xls) Table S4 Costs: Mutation Assays vs. Sequencing (Bi-directional). (0.02 MB XLS) Click here for additional data file.

(23K, xls) Acknowledgments We thank Ms. Claudia Knoll and Ms. Andrea Kosel for excellent technical assistance. Footnotes Competing Interests: The authors have declared that no competing interests exist. Funding: This work was supported by a research grant by the German Research Foundation (DFG) to AH. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.
Gastric cancer is the second most common cause of death from cancer in the world (Yuasa, 2003). The 5-year survival rate remains poor for this type of cancer (Wu et al, 1996, 1997; Lin et al, 1999). Only two survival-influencing factors, the depth of invasion and the presence of regional lymph node involvement, are commonly used in prognosis (Wu et al, 1996, 1997; Lin et al, 1999).

Compared with other more extensively investigated cancers, such as breast, prostate and colon carcinomas, the molecular mechanisms involved in the transformation and progression of gastric cancer are poorly characterised. The histology of gastric carcinomas is conventionally classified into differentiated Drug_discovery and undifferentiated types. The intestinal type is a well-differentiated tumour characterised by cohesive neoplastic cells forming gland-like tubular structures, and the diffuse type is a poorly differentiated tumour resulting in individual cells infiltrating and t