KRAS and gastric cancer: To investigate the biological significance of KRAS amplification in gastric cancer, we used small interfering RNA (siRNA) to knock-down the expression of KRAS or KRAS neighboring genes in four gastric cancer cell lines, HSC45 (carrying amplification and mutation of KRAS), MKN1 (amplification but no mutation of KRAS), AGS (mutation but no amplification of KRAS) and NUGC4 (no amplification or mutation of KRAS).