Fhit modulation of the Akt-survivin pathway in lung cancer cells: Fhit-tyrosine 114 (Y114) is essential

Abstract

The Fhit tumor suppressor binds and hydrolyses diadenosine polyphosphates and the Fhit-substrate complex has been proposed as a proapoptotic effector, as determined by infection of susceptible cancer cells with adenoviruses carrying wild-type fragile histidine triad (FHIT) or catalytic site mutants. The highly conserved Fhit tyrosine 114 (Y114), within the unstructured loop C-terminal of the catalytic site, can be phosphorylated by Src family tyrosine kinases, although endogenous phospho-Fhit is rarely detected. To explore the importance of Y114 and identify Fhit-mediated signaling events, wild-type and Y114 mutant FHIT-expressing adenoviruses were introduced into two human lung cancer cell lines. Caspasedependent apoptosis was effectively induced only by wildtype but not Y114 mutant Fhit proteins. By expression profiling of FHIT versus mutant FHIT-infected cells, we found that survivin, an Inhibitor of Apoptosis Protein (IAP) family member, was significantly decreased by wildtype Fhit. In addition, Fhit inhibited activity of Akt, a key effector in the phosphatidylinositol 3-OH kinase (PI3K) pathway; loss of endogenous Fhit expression caused increased Akt activity in vitro and in vivo, and overexpression of constitutively active Akt inhibited Fhitinduced apoptosis. The results indicate that the Fhit Y114 residue plays a critical role in Fhit-induced apoptosis, occurring through inactivation of the PI3K-Akt-survivin signal pathway.

Protein Expression Profiling Identifies Cyclophilin A as a Molecular Target in Fhit-Mediated Tumor Suppression

“…Inactivation of the phosphatidylinositol 3-kinase/Akt/survivin pathway by Fhit is also implicated in Fhit-mediated apoptosis signaling (20). We assessed previously the Atr-Chk1 pathway in response to mitomycin C, UVC, and ionizing radiation in Fhit-positive and Fhit-negative cells and found that Fhitnegative cells are resistant to apoptosis induced by these genotoxic agents despite activation of the Atr-Chk1 pathway (12,13).…”

“…Cell Culture and Treatment H1299 human lung carcinoma cells (lacking Fhit expression) obtained from the American Type Culture Collection (Manassas, Adenoviruses carrying human recombinant wild-type (Ad-FHIT-wt) and Y114 mutant FHIT substituted with phenylalanine (Ad-FHIT-Y114F) were used in this study (14,20). Briefly, wild-type and mutant FHIT cDNA were cloned into the transfer vector pAdenoVator-CMV5-GFP (Qbiogene, Carlsbad, CA).…”

“…To identify pathways through which Fhit induces tumorsuppressing activity, we exploited the biological differences between wild-type and mutant FHIT adenoviruses (20). For analysis of the effects of recombinant Fhit proteins, H1299 human lung cancer cells were infected with Ad-FHIT-wt and Ad-FHIT-Y114F, respectively.…”

“…However, the mechanism through which Fhit induces cell cycle arrest and apoptosis in cancer cells requires further elucidation. Recently, to investigate the biological significance of the Fhit amino acid sequence DSIY 114 EEL, the consensus target of phosphorylation by Src tyrosine kinase family members (19), site-directed mutagenesis at Tyr 114 (Y114) and mRNA expressing profiling were done after adenovirus-mediated delivery of wild-type and mutant FHIT; it was shown that expression of survivin, a member of the inhibitor of apoptosis protein family, was decreased only by wild-type Fhit possibly as a result of inactivation of the phosphatidylinositol 3-kinase/Akt signaling pathway (20).…”

High throughput tissue microarray analysis of FHIT expression in diffuse large cell B-cell lymphoma from Saudi Arabia

“…43,44 Most recent, it has bee shown that FHIT modulates the Pi3k/AKT pathway by downregulation of the antiapoptotic survivin, an inhibitor of apoptosis protein (IAP) family member. 45 Our data indicate that inactivation of FHIT might be due to different reasons. A comparison of expression data as observed by immunohistochemistry and promotor hypermethylation did not show a significant association.…”