The study investigates the abnormalities in the structure and expression of the retinoblastoma gene (Rb) in small cell lung cancer (SCLC) and pulmonary carcinoids. The Rb gene, located on chromosome 13q14, is a known tumor suppressor gene implicated in various cancers, including retinoblastoma. The researchers examined eight primary SCLC tumors and 50 lung cancer cell lines using Rb complementary DNA probes. Structural abnormalities in the Rb gene were found in 13% of primary SCLC tumors, 18% of SCLC cell lines, and 25% of pulmonary carcinoid lines, but not in other types of lung cancer. Messenger RNA (mRNA) expression of Rb was absent in 60% of SCLC lines and 75% of pulmonary carcinoid lines, while it was present in 90% of non-SCLC lung cancer lines and normal human lung. The findings suggest that the Rb gene may play a role in the pathogenesis of SCLC and pulmonary carcinoids, which are neuroendocrine tumors. The study also highlights the importance of chromosomal deletions in SCLC, particularly on chromosome 13q14, and the potential involvement of Rb in the development of these tumors.The study investigates the abnormalities in the structure and expression of the retinoblastoma gene (Rb) in small cell lung cancer (SCLC) and pulmonary carcinoids. The Rb gene, located on chromosome 13q14, is a known tumor suppressor gene implicated in various cancers, including retinoblastoma. The researchers examined eight primary SCLC tumors and 50 lung cancer cell lines using Rb complementary DNA probes. Structural abnormalities in the Rb gene were found in 13% of primary SCLC tumors, 18% of SCLC cell lines, and 25% of pulmonary carcinoid lines, but not in other types of lung cancer. Messenger RNA (mRNA) expression of Rb was absent in 60% of SCLC lines and 75% of pulmonary carcinoid lines, while it was present in 90% of non-SCLC lung cancer lines and normal human lung. The findings suggest that the Rb gene may play a role in the pathogenesis of SCLC and pulmonary carcinoids, which are neuroendocrine tumors. The study also highlights the importance of chromosomal deletions in SCLC, particularly on chromosome 13q14, and the potential involvement of Rb in the development of these tumors.