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Aims —Loss of heterozygosity (LOH) at specific chromosomal regions strongly suggests the existence of tumour suppressor genes at the relevant segment. Frequent LOH on chromosome 5q has been reported in a wide variety of human tumours, including those of the lung. The aim of this study was to screen for LOH and to clarify the location of putative tumour suppressor genes on chromosome 5 implicated in the genesis and/or development of non-small cell lung carcinoma. Methods —Thirty three patients with advanced non-small cell lung carcinoma were screened for LOH with a panel of 21 microsatellite DNA markers spanning the entire chromosome 5, using semi-automated fluorochrome based methodology. Results —Twenty of the non-small cell lung carcinoma samples displayed LOH for one or more informative locus. LOH involving only 5q was found in 10 of 14 of the informative samples. Deletions involving 5p only were not present in the samples under study. There was no evidence of microsatellite instability in any of the analysed loci. These results indicate the presence of five distinct segments displaying high frequencies of deletion on chromosome 5, namely: 5q11.2–q12.2, 5q15 (D5S644 locus), 5q22.3–q23.1, 5q31.1, and 5q35.3. Eight of 14 samples had simultaneous interstitial deletions in at least two different regions. Moreover, concomitant deletion of three and four distinct regions was displayed in three of 14 and two of 14, respectively, of the informative samples. Conclusion —Allelic deletion on chromosome 5 is a frequent event in patients with non-small cell lung carcinoma. These results suggest the involvement of these five regions, either independently or simultaneously, in both lung squamous cell carcinoma and lung adenocarcinoma.

Aims—To investigate the possible role of mutations in the transforming growth factor β receptor type II gene (TGFBRII) in ovarian cancer and its relation to microsatellite instability (MSI), 43 sporadic ovarian tumours were analysed for mutations over the entire coding region of the TGFBRII gene. Methods—Mutational analysis was performed using the polymerase chain reaction (PCR), single strand conformation polymorphism (SSCP) gel analysis, and direct sequencing. MSI analysis included both mononucleotide and dinucleotide microsatellite markers used for radiolabelling and gene scanning. Results—No pathogenic mutations were detected, although sequencing of the polyadenine (poly A) tract in exon 3 using conventional techniques revealed a spurious frameshift mutation that was not present in the same samples analysed using a proofreading Taq polymerase. MSI analysis demonstrated an MSI negative phenotype in 40 of the 43 tumours. None of the three MSI positive tumours demonstrated MSI for mononucleotide markers only. Conclusions—These findings suggest that: (1) MSI (both conventional and mononucleotide) is infrequent in ovarian cancer and (2) inactivation of the MSH2, MLH1, and MSH6 mismatch repair genes and TGFBR2 gene mutations do not play a major role in ovarian cancer tumorigenesis. The spurious TGFBR2 frameshift mutations detected by sequencing after conventional PCR underline the importance of confirming putative mutations in repetitive sequences by alternative methods.