Association between human-Pneumocystis infection and small-cell lung carcinoma

• Published in: European journal of clinical investigation Vol. 34; no. 3; pp. 229 - 235
• Main Authors: De La Horra, C., Varela, J. M., Fernández-Alonso, J., Medrano, F. J., Respaldiza, N., Montes-Cano, M. A., Calderón, E. J.
• Format: Journal Article
• Language: English
• Published: Oxford, UK Blackwell Science Ltd 01.03.2004; Blackwell; Blackwell Publishing Ltd
• Subjects: Adult; Aged; Aged, 80 and over; Biological and medical sciences; Carcinoma, Non-Small-Cell Lung - microbiology; Carcinoma, Small Cell - microbiology; Carcinoma, Small Cell - secondary; DNA, Bacterial - analysis; Female; General aspects; Genes, Bacterial; Humans; Lung Neoplasms - microbiology; Male; Medical sciences; Middle Aged; Pathology; Pneumocystis; Pneumocystis carinii - genetics; Pneumocystis carinii - isolation & purification; Pneumology; Pneumonia, Pneumocystis - complications; small-cell lung carcinoma; Tumors of the respiratory system and mediastinum; Human; Lung disease; Respiratory disease; Bonchopulmonary small cell carcinoma; Malignant tumor; Fungi; Infection; Medicine; Association; Bronchus disease; Pneumocystis; Fungi Imperfecti; Thallophyta
• ISSN: 0014-2972; 1365-2362
• DOI: 10.1111/j.1365-2362.2004.01317.x

Background  Tobacco smoking is the most important but not the only risk factor in lung carcinoma. There is evidence that certain infections, which cause chronic inflammatory reactions, can also induce tumour development. It has recently been shown that patients with chronic pulmonary diseases present a high rate of subclinical Pneumocystis infection, and that the latter is able to induce inflammatory responses and alveolar cell alterations. The possible role of Pneumocystis infection in the development of lung neoplasms thus deserves consideration. Material and methods  Polymerase chain reaction has been used to analyze the presence of DNA of two independent loci of the Pneumocystis genome: the mitochondrial region (mtLSU rRNA) and the gene encoding for the dihydropteroate synthase enzyme, in paraffin‐embedded tissue blocks of 10 cases of small cell lung carcinoma (SCLC) and 10 cases of nonsmall cell lung carcinoma (NSCLC) with similar demographic and clinical characteristics. Five cases without lung pathology, and two cases of Pneumocystis pneumonia were also analyzed as controls. Results  DNA of the microorganism was found in all the cases of SCLC but in only two of the NSCLC, and in none of the controls without pulmonary disease – thus implying a statistically significant association (P < 0·0001) between subclinical Pneumocystis infection and SCLC. Conclusions  While the nature of this association is not clear, it nevertheless constitutes an important finding – either the infection is specifically facilitated by this tumour or induces the development of this type of neoplasm in combination with other factors.