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从有长期吸烟嗜好的肺癌患者的手术标本（鳞状上皮癌）提取高分子量的癌细胞基因组DNA，对小鼠成纤维细胞（NIH／3T3）进行转染，获二轮转化细胞，发现二轮转化率是一轮的3倍．证实在转染过程中转化灶出现的多少，与所用DNA的量有关，二轮转化细胞可在软琼脂上培养存活，接种裸鼠（BALB／c）于注射部位长出肿瘤。表明该二轮转化细胞具有肿瘤细胞的特性，用32P标记的人Alu重复序列和ras癌基因家族探针分别与一轮、二轮转化细胞和裸鼠肿瘤细胞的DNA进行Southern印迹转移和分子杂交。结果在三者细胞的DNA中都见有与Alu杂交的阳性条带，从而证明在转染过程中人体特有的Alu重复序列已整合到转化细胞的基因组中，并确定了转化细胞中的转化基因之一的属性为Ha－ras癌基因，本工作提示吸烟可能是人体原癌基因（C－Ha－ras）活化和肺鳞癌发生的重要原因。
High-molecular-weight cancer cell genomic DNA was extracted from surgical specimens (squamous cell carcinoma) of lung cancer patients with long-term smoking liking, and mouse fibroblasts (NIH/3T3) were transfected to obtain second-round transformed cells, and two rounds were found. Conversion rate is 3 times in a round. The number of transforming foci in the transfection process was confirmed to correlate with the amount of DNA used. The second round of transformed cells can be cultured on soft agar and inoculated in nude mice (BALB/c) to grow tumors at the injection site. These two rounds of transformed cells showed the characteristics of tumor cells. Southern blotting and molecular hybridization with 32P-labeled human Alu repeats and ras oncogene family probes were performed with DNA from one, two rounds of transformed and nude mouse tumor cells, respectively. . As a result, a positive band that hybridized with Alu was found in the DNA of the three cells, thereby confirming that the unique Alu repeat sequence of the human body has been integrated into the genome of the transformed cell during transfection, and the transformed gene in the transformed cell was determined. One of the attributes is the Ha-ras oncogene. This work suggests that smoking may be an important cause of the activation of human proto-oncogene (C-Ha-ras) and lung squamous cell carcinoma.