Wingless Pathway Research Articles

Regulation of Notch and Wingless signalling by phyllopod, a transcriptional target of the EGFR pathway

Spatial and temporal control of Notch and Wingless (Wg) pathways during development is regulated at multiple levels. Here, we present an analysis of Phyllopod as a coordinated regulator of these two critical signal transduction pathways. Phyl specifically helps traffic Notch and Wg pathway components within early endocytic vesicles, thereby controlling the amount of processed signal available for causing a transcriptional response within the nucleus. In Drosophila, the EGFR pathway transcriptionally activates phyl whose product then blocks Notch and Wg signalling pathways. This provides a mechanistic basis for an antagonistic relationship between receptor tyrosine kinase and Notch/Wg pathways during development. Furthermore, this study identifies a Phyl-regulated class of endosomal vesicles that specifically include components of Notch and Wg signalling.

Fasciclin 2, theDrosophilaorthologue of neural cell-adhesion molecule, inhibits EGF receptor signalling

Adhesion proteins not only control the degree to which cells adhere to each other but are increasingly recognised as regulators of intercellular signalling. Using genetic screening in Drosophila, we have identified Fasciclin 2 (Fas2), the Drosophila orthologue of neural cell adhesion molecule (NCAM), as a physiologically significant and specific inhibitor of epidermal growth factor receptor (EGFR) signalling in development. We find that loss of fas2 genetically interacts with multiple genetic conditions that perturb EGFR signalling. Fas2 is expressed in dynamic patterns during imaginal disc development, and in the eye we have shown that this depends on EGFR activity, implying participation in a negative-feedback loop. Loss of fas2 causes characteristic EGFR hyperactivity phenotypes in the eye, notum and wing, and also leads to downregulation of Yan, a transcriptional repressor targeted for degradation by EGFR activity. No significant genetic interactions were detected with the Notch, Wingless, Hedgehog or Dpp pathways, nor did Fas2 inhibit the FGF receptor or Torso, indicating specificity in the inhibitory role of Fas2 in EGFR signalling. Our results introduce a new regulatory interaction between an adhesion protein and a Drosophila signalling pathway and highlight the extent to which the EGFR pathway must be regulated at multiple levels.

Molecular pathways involved in hair follicle tumor formation: all about mammalian target of rapamycin?

Hair follicle tumors show a broad range of phenotypic variability and diverse histopathological characteristics. To date, different genes and signalling cascades have been implicated in the development and growth of these tumors including the sonic hedgehog, nuclear factor kappa-B and wingless pathway. While the former three have received ample attention, little is known about the possible role of mammalian target of rapamycin (mTOR) in trichofollicular tumorigenesis. Here, we delineate how mTOR can link the various signalling pathways, thereby proposing a unifying model for hair follicle tumor formation.

Presynaptic local signaling by a canonical wingless pathway regulates development of the Drosophila neuromuscular junction.

Wnt/wingless signaling contributes to the development of neuronal synapses, including the Drosophila neuromuscular junction. Loss of wg (wingless) function alters the number and structure of boutons at this model synapse. Examining Wnt/wingless signaling mechanisms, we find that a distinct pathway operates presynaptically in the motoneuron and can account for many of the effects of wingless at this synapse. This pathway includes the canonical elements arrow/LRP (low-density lipoprotein receptor-related protein), dishevelled, and the glycogen synthase kinase shaggy (GSK3) and regulates the formation of microtubule loops within synaptic boutons as well as the number of synaptic boutons. This pathway, however, appears to be independent of beta-catenin signaling and the transcriptional regulation that is most frequently downstream of these components. Instead, inhibition of shaggy is likely to act locally. This pathway thus provides a parallel mechanism to the postsynaptic activation of frizzled receptors and indicates that synaptic development results from the bidirectional influence of wingless on both presynaptic and postsynaptic structures via distinct intracellular pathways.

Paracrine inhibition of osteoblast differentiation induced by neuroblastoma cells

The aim of our study was to investigate whether the defective function of osteogenic cells induced by neuroblastoma might play a role in the development of skeletal metastases. This mechanism has been extensively demonstrated for multiple myeloma, in which the blockage of osteoblast differentiation has been ascribed to the inhibitors of canonical Wingless pathway (Wnt), namely Dickkopf 1 (Dkk1). Our purpose was to verify if neuroblastoma cells derived from bone marrow metastases (SH-SY5Y, LAN1) or primaries (NB100, CHP212) hamper the differentiation of mesenchymal stem cells (hMSCs) into osteoblasts in a paracrine manner, and to test whether this ability depends on Dkk1 activity. We found that all neuroblastoma cells increased the proliferation of hMSCs collected from pediatric-aged donors, with a corresponding decrease in osteoblast differentiation markers, including alkaline phosphatase (ALP), analyzed as gene expression, enzymatic activity and number of ALP-positive colony forming units, osteoprotegerin (OPG) release, OPG and osteocalcin gene-expression. Dkk1 mRNA and protein were detectable in all cell lines, and the use of neutralizing anti-Dkk1 antibody reversed the effects induced by SH-SY5Y cells. Taken together, our results confirm that neuroblastoma hinders osteoblastogenesis, and that Dkk1 release seems to play a crucial role in blocking the differentiation of osteoprogenitor cells, though the ability to promote osteoclast activation remains an essential requirement for the development of skeletal metastases. Finally, our findings suggest that strategies regulating Wnt signaling and Dkk1 activity could be considered for adjuvant therapies in neuroblastoma metastasizing to the skeleton.

Human homolog of NOTUM, overexpressed in hepatocellular carcinoma, is regulated transcriptionally by β‐catenin/TCF

The Drosophila Notum gene, which is regulated by the Wingless pathway, encodes a secreted hydrolase that modifies heparan sulfate proteoglycans. In comparative analysis of the gene expression profiles in primary human hepatocellular carcinomas (HCC) and normal organs, we observed that the human ortholog of Drosophila Notum was overexpressed markedly in a subset of HCC, but expressed rarely in adult normal tissues. Immunoblotting confirmed the overexpression of NOTUM protein in 12 of 40 primary HCC cases (30%). High levels of NOTUM protein were significantly associated with intracellular (nuclear or cytoplasmic) accumulation of beta-catenin protein: all 10 HCC with high intracellular beta-catenin also had high NOTUM expression, whereas only 2 of 30 cases (6.7%) without intracellular beta-catenin had high NOTUM expression (P < 0.00001). NOTUM expression in HepG2 cells was downregulated significantly by induction of a dominant-negative mutant of TCF4, a beta-catenin partner. In vivo binding of the beta-catenin/TCF complex to the NOTUM promoter was demonstrated by chromatin immunoprecipitation in HepG2 and SW480 cells, where canonical Wnt signaling is activated constitutively. These findings provide evidence that NOTUM is a novel target of beta-catenin/TCF4 and is upregulated in Wnt/beta-catenin signaling-activated HCC.

Functional screening identifies miR-315 as a potent activator of Wingless signaling.

The existence of vast regulatory networks mediated by microRNAs (miRNAs) suggests broad potential for miRNA dysfunction to contribute to disease. However, relatively few miRNA-target interactions are likely to make detectable contributions to phenotype, and effective strategies to identify these few interactions are currently wanting. We hypothesized that signaling cascades represent critical points of susceptibility to miRNA dysfunction, and we developed a strategy to test this theory by using quantitative cell-based screens. Here we report a screen for miRNAs that affect the Wingless (Wg) pathway, a conserved pathway that regulates growth and tissue specification. This process identified ectopic miR-315 as a potent and specific activator of Wg signaling, an activity that we corroborated in transgenic animals. This miR-315 activity was mediated by direct inhibition of Axin and Notum, which encode essential, negatively acting components of the Wg pathway. Genetic interaction tests substantiated both of these genes as key functional targets of miR-315. The ability of ectopic miR-315 to activate Wg signaling was not a trivial consequence of predicted miRNA-target relationships because other miRNAs with conserved sites in the Axin 3' UTR neither activated Wg outputs nor inhibited an Axin sensor. In summary, activity-based screening can selectively identify miRNAs whose deregulation can lead to interpretable phenotypic consequences.

A combinatorial enhancer recognized by Mad, TCF and Brinker first activates then represses dpp expression in the posterior spiracles of Drosophila

A previous genetic analysis of a reporter gene carrying a 375-bp region from a dpp intron (dppMX-lacZ) revealed that the Wingless and Dpp pathways are required to activate dpp expression in posterior spiracle formation. Here we report that within the dppMX region there is an enhancer with binding sites for TCF and Mad that are essential for activating dppMX expression in posterior spiracles. There is also a binding site for Brinker likely employed to repress dppMX expression. This combinatorial enhancer may be the first identified with the ability to integrate temporally distinct positive (TCF and Mad) and negative (Brinker) inputs in the same cells. Cuticle studies on a unique dpp mutant lacking this enhancer showed that it is required for viability and that the Filzkorper are U-shaped rather than straight. Together with gene expression data from these mutants and from brk mutants, our results suggest that there are two rounds of Dpp signaling in posterior spiracle development. The first round is associated with dorsal–ventral patterning and is necessary for designating the posterior spiracle field. The second is governed by the combinatorial enhancer and begins during germ band retraction. The second round appears necessary for proper spiracle internal morphology and fusion with the remainder of the tracheal system. Intriguingly, several aspects of dpp posterior spiracle expression and function are similar to demonstrated roles for Wnt and BMP signaling in proximal–distal outgrowth of the mammalian embryonic lung.

Eukaryotic initiation factor 6 selectively regulates Wnt signaling and β-catenin protein synthesis

Eukaryotic initiation factor 6 (eIF6), an essential protein important in ribosome biosynthesis and assembly, was identified as an interacting partner of the beta-catenin C terminus in the yeast two-hybrid assay. Independent studies identified Drosophila eIF6 (DeIF6) in a genetic screen designed to detect new genes involved in the regulation of the Wnt/Wg (wingless) pathway. Ectopic expression of DeIF6 in wing discs results in a Wg phenotype. Expression of eIF6 in adenomatous polyposis coli (APC)-mutant colon cancer cells, which express high levels of active beta-catenin, showed that eIF6 selectively inhibits the Wnt pathway at the level of beta-catenin protein independently of proteasomal degradation. Incorporation of radiolabeled amino acids into beta-catenin was selectively decreased in cells that overexpressed eIF6. A similar inverse relationship of the two proteins was observed in the APC(min/+) mouse intestine, in which beta-catenin levels are very high. Taken together these data reveal a link between eIF6 and Wnt signaling, perhaps at the level of ribosome recycling on beta-catenin mRNA.

TheDrosophilaHMG-domain proteins SoxNeuro and Dichaete direct trichome formation via the activation ofshavenbabyand the restriction of Wingless pathway activity

Trichomes are cytoplasmic extrusions of epidermal cells. The molecular mechanisms that govern the differentiation of trichome-producing cells are conserved across species as distantly related as mice and flies. Several signaling pathways converge onto the regulation of a conserved target gene, shavenbaby (svb, ovo), which, in turn, stimulates trichome formation. The Drosophila ventral epidermis consists of the segmental alternation of two cell types that produce either naked cuticle or trichomes called denticles. The binary choice to produce naked cuticle or denticles is affected by the transcriptional regulation of svb, which is sufficient to cell-autonomously direct denticle formation. The expression of svb is regulated by the opposing gradients of two signaling molecules--the epidermal growth factor receptor (Egfr) ligand Spitz (Spi), which activates svb expression, and Wingless (Wg), which represses it. It has remained unclear how these opposing signals are integrated to establish a distinct domain of svb expression. We show that the expression of the high mobility group (HMG)-domain protein SoxNeuro (SoxN) is activated by Spi, and repressed by Wg, signaling. SoxN is necessary and sufficient to cell-autonomously direct the expression of svb. The closely related protein Dichaete is co-regulated with SoxN and has a partially redundant function in the activation of svb expression. In addition, we show that SoxN and Dichaete function upstream of Wg and antagonize Wg pathway activity. This suggests that the expression of svb in a discreet domain is resolved at the level of SoxN and Dichaete.

Comparative Analysis of Two UDP-glucose Dehydrogenases in Pseudomonas aeruginosa PAO1

UDP-glucose dehydrogenase (UGDH) catalyzes a two-step NAD(+)-dependent oxidation of UDP-glucose to produce UDP-glucuronic acid, which is a common substrate for the biosynthesis of exopolysaccharide. Searching the Pseudomonas aeruginosa PAO1 genome data base for a UGDH has helped identify two open reading frames, PA2022 and PA3559, which may encode a UGDH. To elucidate their enzymatic identity, the two genes were cloned and overexpressed in Escherichia coli, and the recombinant proteins were purified. Both the gene products are active as dimers and are capable of utilizing UDP-glucose as a substrate to generate UDP-glucuronic acid. The K(m) values of PA2022 and PA3559 for UDP-glucose are approximately 0.1 and 0.4 mM, whereas the K(m) values for NAD(+) are 0.5 and 2.0 mM, respectively. Compared with PA3559, PA2022 exhibits broader substrate specificity, utilizing TDP-glucose and UDP-N-acetylglucosamine with one-third the velocity of that with UDP-glucose. The PA2022 mutant and PA2022-PA3559 double mutant, but not the PA3559 mutant, are more susceptible to chloramphenicol, cefotaxime, and ampicillin. The PA3559 mutant, however, shows a reduced resistance to polymyxin B compared with wild type PAO1. Finally, real time PCR analysis indicates that PA3559 is expressed primarily in low concentrations of Mg(2+), which contrasts with the constitutive expression of PA2022. Although both the enzymes catalyze the same reaction, their enzymatic properties and gene expression profiles indicate that they play distinct physiological roles in P. aeruginosa, as reflected by different phenotypes displayed by the mutants.

Progesterone initiates Wnt-β-catenin signaling but estradiol is required for nuclear activation and synchronous proliferation of rat uterine stromal cells

Progesterone pretreatment of ovariectomized rat uteri increases the number of synchronously proliferating stromal cells in response to estradiol 17-beta. To identify the signals involved in stimulating synchronous proliferation, sexually mature ovariectomized rats were injected with progesterone (2 mg) for 3 consecutive days. Estradiol 17-beta (0.2 microg) was administered to initiate cell cycle entry. Uterine samples were removed at various times after hormone administration and changes in wingless (Wnt) pathway effectors and gene targets were identified by microarray. Progesterone pretreatment decreased glycogen synthase kinase-3beta (GSK-3beta) and increased expression of T-cell factor/lymphoid enhancer factor (TCF/LEF). GSK-3beta protein decreased markedly in the uterine stroma of progesterone-pretreated uteri with the concomitant appearance of beta-catenin in these stromal cells. Translocation of beta-catenin from the cytosol to the nuclei in progesterone-pretreated stromal cells was stimulated in response to estradiol. Beta-catenin binding to TCF/LEF increased (P<0.05) in progesterone-pretreated uteri in response to estradiol. Progesterone stimulated the expression of the Wnt target gene urokinase plasminogen activator receptor (uPA-R) in the periluminal uterine stromal cells. The expression of uPA-R increased in progesterone-pretreated stromal cells in response to estradiol administration. Together, the results indicate that progesterone initiates Wnt signaling in the uterine stroma by down-regulating GSK-3beta. However, nuclear translocation of beta-catenin and sufficient complex formation with TCF/LEF to activate stromal cell cycle entry requires estradiol. Stimulation of a uterine stromal cell line to proliferate and differentiate resulted in beta-catenin accumulation, suggesting that endocrine-dependent Wnt signaling controls proliferation and differentiation (decidualization).

Cytochrome c‐d regulates developmental apoptosis in the Drosophila retina

The role of cytochrome c (Cyt c) in caspase activation has largely been established from mammalian cell-culture studies, but much remains to be learned about its physiological relevance in situ. The role of Cyt c in invertebrates has been subject to considerable controversy. The Drosophila genome contains distinct cyt c genes: cyt c-p and cyt c-d. Loss of cyt c-p function causes embryonic lethality owing to a requirement of the gene for mitochondrial respiration. By contrast, cyt c-d mutants are viable but male sterile. Here, we show that cyt c-d regulates developmental apoptosis in the pupal eye. cyt c-d mutant retinas show a profound delay in the apoptosis of superfluous interommatidial cells and perimeter ommatidial cells. Furthermore, there is no apoptosis in mutant retinal tissues for the Drosophila homologues of apoptotic protease-activating factor 1 (Ark) and caspase 9 (Dronc). In addition, we found that cyt c-d--as with ark and dronc-regulates scutellar bristle number, which is known to depend on caspase activity. Collectively, our results indicate a role of Cyt c in caspase regulation of Drosophila somatic cells.

Border of Notch activity establishes a boundary between the two dorsal appendage tube cell types

Boundaries establish and maintain separate populations of cells critical for organ formation. We show that Notch signaling establishes the boundary between two types of post-mitotic epithelial cells, the Rhomboid- and the Broad-positive cells. These cells will undergo morphogenetic movements to generate the two sides of a simple organ, the dorsal appendage tube of the Drosophila egg chamber. The boundary forms due to a difference in Notch levels in adjacent cells. The Notch expression pattern mimics the boundary; Notch levels are high in Rhomboid cells and low in Broad cells. Notch − mutant clones generate an ectopic boundary: ectopic Rhomboid cells arise in Notch + cells adjacent to the Notch − mutant cells but not further away from the clonal border. Pangolin, a component of the Wingless pathway, is required for Broad expression and for rhomboid repression. We further show that Broad represses rhomboid cell autonomously. Our data provide a foundation for understanding how a single row of Rhomboid cells arises adjacent to the Broad cells in the dorsal appendage primordia. Generating a boundary by the Notch pathway might constitute an evolutionarily conserved first step during organ formation in many tissues.

Wingless signaling modulates cadherin-mediated cell adhesion inDrosophilaimaginal disc cells

Armadillo, the Drosophila homolog of beta-catenin, plays a crucial role in both the Wingless signal transduction pathway and cadherin-mediated cell-cell adhesion, raising the possibility that Wg signaling affects cell adhesion. Here, we use a tissue culture system that allows conditional activation of the Wingless signaling pathway and modulation of E-cadherin expression levels. We show that activation of the Wingless signaling pathway leads to the accumulation of hypophosphorylated Armadillo in the cytoplasm and in cellular processes, and to a concomitant reduction of membrane-associated Armadillo. Activation of the Wingless pathway causes a loss of E-cadherin from the cell surface, reduced cell adhesion and increased spreading of the cells on the substratum. After the initial loss of E-cadherin from the cell surface, E-cadherin gene expression is increased by Wingless. We suggest that Wingless signaling causes changes in Armadillo levels and subcellular localization that result in a transient reduction of cadherin-mediated cell adhesion, thus facilitating cell shape changes, division and movement of cells in epithelial tissues.

Nuclear trafficking of Drosophila Frizzled-2 during synapse development requires the PDZ protein dGRIP

The Wingless pathway plays an essential role during synapse development. Recent studies at Drosophila glutamatergic synapses suggest that Wingless is secreted by motor neuron terminals and binds to postsynaptic Drosophila Frizzled-2 (DFz2) receptors. DFz2 is, in turn, endocytosed and transported to the muscle perinuclear area, where it is cleaved, and the C-terminal fragment is imported into the nucleus, presumably to regulate transcription during synapse growth. Alterations in this pathway interfere with the formation of new synaptic boutons and lead to aberrant synaptic structures. Here, we show that the 7 PDZ protein dGRIP is necessary for the trafficking of DFz2 to the nucleus. dGRIP is localized to Golgi and trafficking vesicles, and dgrip mutants mimic the synaptic phenotypes observed in wg and dfz2 mutants. DFz2 and dGRIP colocalize in trafficking vesicles, and a severe decrease in dGRIP levels prevents the transport of endocytosed DFz2 receptors to the nucleus. Moreover, coimmunoprecipitation experiments in transfected cells and yeast two-hybrid assays suggest that the C terminus of DFz2 interacts directly with the PDZ domains 4 and 5. These results provide a mechanism by which DFz2 is transported from the postsynaptic membrane to the postsynaptic nucleus during synapse formation and implicate dGRIP as an essential molecule in the transport of this signal.

Independent roles of Drosophila Moesin in imaginal disc morphogenesis and hedgehog signalling

The three ERM proteins (Ezrin, Radixin and Moesin) form a conserved family required in many developmental processes involving regulation of the cytoskeleton. In general, the molecular function of ERM proteins is to link specific membrane proteins to the actin cytoskeleton. In Drosophila, loss of moesin ( moe) activity causes incorrect localisation of maternal determinants during oogenesis, failures in rhabdomere differentiation in the eye and alterations of epithelial integrity in the wing imaginal disc. Some aspects of Drosophila Moe are related to the activity of the small GTPase RhoA, because the reduction of RhoA activity corrects many phenotypes of moe mutant embryos and imaginal discs. We have analysed the phenotype of moesin loss-of-function alleles in the wing disc and adult wing, and studied the effects of reduced Moesin activity on signalling mediated by the Notch, Decapentaplegic, Wingless and Hedgehog pathways. We found that reductions in Moesin levels in the wing disc cause the formation of wing-tissue vesicles and large thickenings of the vein L3, corresponding to breakdowns of epithelial continuity in the wing base and modifications of Hedgehog signalling in the wing blade, respectively. We did not observe any effect on signalling pathways other than Hedgehog, indicating that the moe defects in epithelial integrity have not generalised effects on cell signalling. The effects of moe mutants on Hedgehog signalling depend on the correct gene-dose of rhoA, suggesting that the requirements for Moesin in disc morphogenesis and Hh signalling in the wing disc are mediated by its regulation of RhoA activity. The mechanism linking Moesin activity with RhoA function and Hedgehog signalling remains to be elucidated.

Internalization is required for proper Wingless signaling in Drosophila melanogaster

The Wnt–Wingless (Wg) pathway regulates development through precisely controlled signaling. In this study, we show that intracellular trafficking regulates Wg signaling levels. In Drosophila melanogaster cells stimulated with Wg media, dynamin or Rab5 knockdown causes reduced Super8XTOPflash activity, suggesting that internalization and endosomal transport facilitate Wg signaling. In the wing, impaired dynamin function reduces Wg transcription. However, when Wg production is unaffected, extracellular Wg levels are increased. Despite this, target gene expression is reduced, indicating that internalization is also required for efficient Wg signaling in vivo. When endosomal transport is impaired, Wg signaling is similarly reduced. Conversely, the expression of Wg targets is enhanced by increased transport to endosomes or decreased hepatocyte growth factor–regulated tyrosine kinase substrate– mediated transport from endosomes. This increased signaling correlates with greater colocalized Wg, Arrow, and Dishevelled on endosomes. As these data indicate that endosomal transport promotes Wg signaling, our findings suggest that the regulation of endocytosis is a novel mechanism through which Wg signaling levels are determined.

Genomics Identifies Medulloblastoma Subgroups That Are Enriched for Specific Genetic Alterations

Traditional genetic approaches to identify gene mutations in cancer are expensive and laborious. Nonetheless, if we are to avoid rejecting effective molecular targeted therapies, we must test these drugs in patients whose tumors harbor mutations in the drug target. We hypothesized that gene expression profiling might be a more rapid and cost-effective method of identifying tumors that contain specific genetic abnormalities. Gene expression profiles of 46 samples of medulloblastoma were generated using the U133av2 Affymetrix oligonucleotide array and validated using real-time reverse transcriptase polymerase chain reaction (RT-PCR) and immunohistochemistry. Genetic abnormalities were confirmed using fluorescence in situ hybridization (FISH) and direct sequencing. Unsupervised analysis of gene expression profiles partitioned medulloblastomas into five distinct subgroups (subgroups A to E). Gene expression signatures that distinguished these subgroups predicted the presence of key molecular alterations that we subsequently confirmed by gene sequence analysis and FISH. Subgroup-specific abnormalities included mutations in the Wingless (WNT) pathway and deletion of chromosome 6 (subgroup B) and mutations in the Sonic Hedgehog (SHH) pathway (subgroup D). Real-time RT-PCR analysis of gene expression profiles was then used to predict accurately the presence of mutations in the WNT and SHH pathways in a separate group of 31 medulloblastomas. Genome-wide expression profiles can partition large tumor cohorts into subgroups that are enriched for specific genetic alterations. This approach may assist ultimately in the selection of patients for future clinical trials of molecular targeted therapies.

Future Directions in the Second-Line Treatment of Non–Small Cell Lung Cancer

Single-agent chemotherapy has shown limited activity as second-line treatment in metastatic non-small cell lung cancer (NSCLC), with short-lived responses and modest survival benefit over best supportive care or placebo. There are multiple ways to improve the poor outcome of patients whose disease progresses after first-line chemotherapy. First, individualizing second-line chemotherapy could optimize its effect; the discovery of dramatic responses and significant improvement in survival in patients with epidermal growth factor receptor (EGFR) gene mutations who are treated with EGFR tyrosine kinase inhibitors may lead to the application of other novel therapeutic approaches. Cancer vaccines, using autologous tumor cells genetically modified with granulocyte-macrophage colony-stimulating factor, constitute a new therapeutic option for patients with chemoresistant advanced NSCLC. Vaccines based on lymphocyte-defined tumor antigens, such as melanoma-associated antigen-3, toll-like receptor 9, and mucin 1, are also in the first stages of testing and have shown promising preliminary results. New approaches in gene therapy, including a p53-based method, are currently being investigated. The ultimate goal of gene therapy is to target cancerous stem cells, the importance of which is beginning to be recognized in NSCLC through the study of abnormalities in the wingless (Wnt) pathway. At the preclinical level, small interfering RNA sequences have been used successfully to neutralize multiple abnormal components of the Wnt pathway.