Agarose gel showing α7 nicotinic acetylcholine receptor expression in tissue samples from lung cancer patients. cDNA was amplified by PCR using the human α7 primers. 1) large cell carcinoma; 2) carcinoid; 3–5) squamous cell carcinomas; 6–8) adenocarcinomas; 9) adenocarcinoma/carcinoid. For all gene expression experiments, negative control reactions were performed and found to be negative. The bands were consistent with the expected size, 335 bp. M-100 bp DNA ladder.