Mutation analysis of the PTEN/MMAC1 gene in lung cancer

Abstract

We studied PTEN/MMAC1, a newly discovered candidate tumor suppressor gene at 10q23.3, for mutations in lung cancer. One hundred and thirty-six lung cancer cell line DNAs (66 small cell lung cancers, SCLC, 61 non-small cell lung cancers, NSCLC, four mesotheliomas, ®ve extrapulmonary small cell cancers) were analysed for PTEN/MMAC1 homozygous deletions and ®ve (8%) SCLC lines showed homozygous deletions interrupting the PTEN/MMAC1 gene. Using single stranded conformation polymorphism (SSCP) analysis, we screened the PTEN/MMAC1 open reading frame of 53 lung cancer cell line cDNAs for point mutations and found that 3/35 SCLCs and 3/18 NSCLCs contained homozygous amino acid sequence altering mutations. Northern blot analysis revealed that expression of the PTEN/MMAC1 gene was considerably lower in all the tumor cell lines with point mutations while no expression was detected for cell lines with PTEN/MMAC1 homozygous deletions. Mutation analysis of 22 uncultured, microdissected, primary SCLC tumors and metastases showed two silent mutations, and two apparent homozygous deletions. We also discovered a processed pseudogene (PTEN2) which has 98.5% nt identity to PTEN/MMAC1, that needs to be accounted for in cDNA mutation analysis. Our ®ndings suggest that genetic abnormalities of the PTEN/MMAC1 gene are only involved in a relatively small subset of lung cancers.

H-REV107-1 Stimulates Growth in Non-Small Cell Lung Carcinomas via the Activation of Mitogenic Signaling

“…For instance, the pRB tumor suppressor is absent in 90% of SCLCs but only 10 to 15% of NSCLCs 43 ; PTEN is mutated in ϳ30% of SCLCs but only 5% of NSCLCs. 44,45 Similar to these observations, H-REV107-1 was expressed in NSCLCs and NSCLC cell lines but lost in most SCLC cell lines analyzed. This indicates a potentially different role of H-REV107-1 in these two types of lung cancer.…”

Evidence That Phosphatidylinositol 3-Kinase- and Mitogen-activated Protein Kinase Kinase-4/c-Jun NH2-terminal Kinase-dependent Pathways Cooperate to Maintain Lung Cancer Cell Survival

“…However, PI3K-dependent signaling is activated in cancer cells through mechanisms other than PTEN gene loss, as demonstrated in NSCLC cells, which typically have evidence of PI3K pathway activation and express wild-type PTEN (25)(26)(27)(28)(29)(30). Here we investigated the role of PI3K in the survival of a NSCLC cell line that expresses wild-type PTEN.…”

“…Proliferation and Survival-We investigated the effects of PI3K inhibition on the proliferation and viability of H1299 NSCLC cells, which have a wild-type PTEN gene (27). H1299 cells were transfected with recombinant adenoviruses that express PTEN (Ad5-PTEN) or ⌬p85 (Ad5-⌬p85), a p85␣ dominant-negative mutant lacking the inter-SH2 residues required for binding to the p110 catalytic domain (35).…”

“…Most nonsmall cell lung cancer (NSCLC) cell lines demonstrate hallmarks of PI3K pathway activation, such as phosphorylation of AKT and its downstream mediators, but have a wild-type PTEN gene (25)(26)(27)(28)(29)(30). Despite having wild-type PTEN, NSCLC cells undergo apoptosis in response to PI3K pathway inhibition (25).…”

Genetic alterations of multiple tumor suppressors and oncogenes in the carcinogenesis and progression of lung cancer

“…PTEN/MMAC1 (phosphatase and tensin homolog/ mutated in multiple advanced cancers 1) functions as a phosphoinositide 3-phosphatase that negatively regulates Phosphatidylinositol-3 kinase (PI3K)/AKT signaling, and has been suggested to be involved in the induction of anoikis and inhibition of cell migration (Yamada and Araki, 2001;Nadav and Katz, 2001). Although the chromosomal assignment of the PTEN/MMAC1 gene (10q23.3) coincides with a frequently deleted region in many malignancies including lung cancer, somatic mutations or homozygous deletions of the PTEN/MMAC1 gene are present in a relatively small subset of cell lines (*10%) and primary specimens (0*5%) of lung cancer (Forgacs et al, 1998;Yokomizo et al, 1998;Kohno et al, 1998;Cagle et al, 1997;Okami et al, 1998).…”