Detection of microsatellite alterations in plasma DNA of non-small cell lung cancer patients: a prospect for early diagnosis.

A major problem in lung cancer is the lack of clinically useful tests for early diagnosis and screening of an asymptomatic population by non-invasive diagnostic procedures. Recent studies have demonstrated the possibility to detect genetic alterations in plasma or serum DNA from patients with various cancers. However, these data rely on small series of aggressive tumors with advanced-stage disease. To determine whether genetic changes in plasma are also detectable in patients with limited disease and thereby potentially useful for early detection, we looked for microsatellite instability (allele shift) and loss of heterozygosity in plasma DNA of 87 stage I-III non-small cell lung cancers and 14 controls. Combining two markers with a high rate of instability (D21S1245) and loss of heterozygosity (FHIT locus), a microsatellite alteration was observed in 49 of 87 (56%) non-small cell lung cancer tumors and in 35 of 87 (40%) plasma samples. Thirty of 49 (61%) of the cases showing tumor alterations also displayed a change in plasma DNA; in addition, 5 patients displayed alterations in plasma samples only. None of the control individuals had genetic changes in plasma. No association was found between the frequency of microsatellite alterations in plasma and tumor stage or histology. Of interest, plasma DNA abnormalities were detectable in 43% of pathological stage I cases and in 45% of tumors up to 2 cm in maximum diameter. These findings highlight new prospects for early tumor detection by noninvasive screening procedures based on the analysis of genetic changes in plasma.

Association between cigarette smoking and FHIT gene alterations in lung cancer.

Epidemiologic data have strongly indicated that cigarette smoking is linked to the development of lung cancer. However, little is known of the molecular targets of carcinogens contained in tobacco smoke. To identify genetic lesions characteristic of tobacco damage, we undertook a molecular analysis of microsatellite alterations within the FHIT gene and FRA3B, as well as at an independent locus on chromosome 10, D10S197, in lung tumors from heavy smokers and in tumors from never smokers. Loss of heterozygosity affecting at least one locus of the FHIT gene was observed in 41 of 51 tumors in the smokers group (80%) but in only 9 of 40 tumors in nonsmokers (22%). The comparison between the frequency of losses in FHIT in smokers and nonsmokers was statistically significant (P = 0.0001), whereas no difference in loss of heterozygosity rate was observed at D10S197 locus. These findings suggest that FHIT is a candidate molecular target of carcinogens contained in tobacco smoke.

Relevance of cytogenetic and fluorescent in situ hybridization analyses in the clinical assessment of soft tissue sarcoma.

Soft tissue sarcomas are a heterogeneous group of malignant tumors displaying a wide range of clinical presentations, morphological features, and biological behaviors. These characteristics and the recent development of differentiated treatment regimens for the different types of soft tissue sarcomas call for refined histological classification using additional ancillary approaches such as cytogenetic and molecular genetic analyses. We coupled classical cytogenetics and fluorescent in situ hybridization (FISH) on both metaphases and interphase nuclei to show the feasibility of this approach to characterize tumor type-specific chromosome rearrangements in soft tissue sarcomas of different histotype. In 35 cases analyzed, we detected the presence of specific chromosome rearrangements such as t(X;18) in synovial sarcoma (SS), t(12;16) in myxoid liposarcoma (MLS), t(11;22) in peripheral primitive neuroectodermal tumors (pPNET), t(2;13) in alveolar rhabdomyosarcoma (ARMS) and ring chromosomes in dermatofibrosarcoma protuberans (DFSP). In several cases, the presence of these cytogenetic rearrangements was of help for a differential diagnosis. The FISH analysis using painting probes not only confirmed the cytogenetic results but also allowed the identification of tumor-specific chromosome changes in those cases presenting low mitotic index or with poor quality chromosomes. Moreover, in the absence of analysable metaphases, FISH was successfully performed on interphase nuclei. Taken together, these results indicate both the diagnostic and clinical relevance of a molecular cytogenetic analysis in the study of soft tissue sarcomas.

Microsatellite alterations in bronchial and sputum specimens of lung cancer patients.

Early diagnosis of lung cancer based on conventional screening procedures has been unable thus far to decrease lung cancer mortality. We explored the possibility of using microsatellite instability in the detection and screening of early phases of lung carcinogenesis. We studied tumor, histopathologically normal bronchial mucosa, and cytological specimens of 51 lung cancer patients for the presence of clonal variations at microsatellite polymorphisms. Microsatellite alterations were found in tumor, normal bronchial mucosa and cytological specimens of 25 of 51 (49%) of the patients. The detection of microsatellite alterations in histopathologically normal bronchial specimens and cytological clinical samples with minimal atypia suggests a possible application of this genetic marker in early diagnosis of precancerous lesions and lung cancer.