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Purpose: The aim of this study was to explore the gene expression pattern produced by the cancer-associated BRCA1 5083del19 founder mutation by using a microarray analysis. Such a mutation, identified in a subset of familial breast cancer patients, involves a deletion at the 3' end of the BRCA1 messenger leading, in the mature protein, to the ablation of the BRCT tandem domain., Experimental Design: We generated HeLa cells stably expressing both exogenous wild-type (HeLa/(wt)BRCA1), used as a control, and 5083del19 BRCA1 (HeLa/(5083del19)BRCA1) alleles; gene chips were then used to investigate any changes in the transcription profile induced by the 5083del19 BRCA1 mutant compared with controls., Results: Among the genes showing perturbation of their expression, periostin was found to be up-regulated in HeLa/(5083del19)BRCA1 cells to an extent of 72-fold versus HeLa/(pcDNA3.1/empty) and 76-fold versus HeLa/(wt)BRCA1 cells. This finding was validated both in vitro in breast cancer cell lines harboring mutations of BRCA1 and in vivo by immunohistochemistry of breast cancer specimens bearing the 5083del19 BRCA1 mutation as well as by Western blot analysis of sera obtained from patients and healthy carriers of the same mutation., Conclusions: Our results suggest that periostin overexpression, whose product is released from cells in the extracellular fluids, might be a potential marker for early cancer detection in a specific subset of hereditary breast carcinomas triggered by cancer-associated BRCA1 mutations that affect the BRCT tandem domain.

ARLTS1 is a newly characterized tumor suppressor gene located at chromosome 13q14.3 and involved in the pathogenesis of various types of tumors: two single-nucleotide polymorphisms, one of them responsible for protein truncation, were found statistically associated with familial malignancies, whereas DNA hypermethylation and genomic deletions have been identified as a mechanism of ARLTS1 down-regulation in sporadic cancers. We found that in a large portion of lung carcinomas (37%) and in all analyzed lung cancer cell lines, ARLTS1 is strongly down-regulated due to DNA methylation in its promoter region. After its restoration by adenoviral transduction, ARLTS1-negative A549 and H1299 cells underwent apoptosis and inhibition of cell growth. Furthermore, ARLTS1 reexpression significantly reduced the ability of A549 and H1299 to form tumors in nude mice. Finally, we identified approximately 650 transcripts differentially expressed after restoration of ARLTS1 expression in A549 cells, suggesting that various pathways involved in cell survival, proliferation, signaling, and development mediate the effects of wild-type ARLTS1 in a lung cancer system.

WWOX is a tumor suppressor that functions as a modular protein partner of transcription factors. WWOX contains two WW domains that mediate protein-protein interactions. In this report, we show that WWOX, via its first WW domain, specifically associates with the proline-rich motif of c-Jun proto-oncogene. Our data show that phosphorylation of c-Jun caused by overexpression of mitogen-activated protein kinase kinase kinase 1 (Mekk1), an upstream activator of c-Jun, enhances the interaction of c-Jun with WWOX. Furthermore, exposure of HaCaT keratinocytes to UVC radiation resulted in the association of endogenous WWOX and c-Jun. The WWOX-c-Jun complexes mainly occur in the cytoplasm. Expression of WWOX attenuates the ability of MEKK1 to increase the activity of a c-Jun-driven activating protein-1 (AP-1)-luciferase reporter plasmid. In contrast, a point mutation in the first WW domain of WWOX has no effect on transactivation of AP-1 when coexpressed with c-Jun protein. Our findings reveal a novel functional cross-talk between c-Jun transcription factor and WWOX tumor suppressor protein.

In preneoplastic lesions, the DNA damage checkpoint is induced and loss of heterozygosity at the FRA3B/FHIT common chromosome fragile region precedes or is coincident with activation of the checkpoint response in these early stages. Introduction of exogenous Fhit into cells in vitro led to modulation of expression of checkpoint proteins Hus1 and Chk1 at mid-S checkpoint, a modulation that led to induction of apoptosis in esophageal cancer cells but not in noncancerous primary cultures. Mutation of the conserved Fhit tyrosine 114 resulted in failure of this function, confirming the importance of this residue. The results suggest that the DNA damage-susceptible FRA3B/FHIT chromosome fragile region, paradoxically, encodes a protein that is necessary for protecting cells from accumulation of DNA damage through its role in modulation of checkpoint proteins, and inactivation of Fhit contributes to accumulation of abnormal checkpoint phenotypes in cancer development.

ARLTS1 is a tumor suppressor gene initially described as a low-penetrance cancer gene: a truncated Trp149Stop (MUT) polymorphism is associated with general familial cancer aggregation and, particularly, high-risk familial breast cancer. DNA hypermethylation has been identified as a mechanism of ARLTS1 expression down-regulation in lung carcinomas and B-cell chronic lymphocytic leukemia. We found that, in the majority of ovarian carcinomas (61.5%) and in a significant proportion of ovarian and breast cancer cell lines (45%), ARLTS1 is strongly down-regulated due to DNA methylation in its promoter region. After ARLTS1 restoration by adenoviral transduction, only the negative TOV-112 and the homozygously mutated (MUT) MCF7 cells, but not the OV-90 cells expressing a normal ARLTS1 product, underwent apoptosis and inhibition of cell growth. Furthermore, ARLTS1 reexpression significantly reduced the tumorigenic potential of TOV-112 in nude mice. On the contrary, the ARLTS1-MUT induced significantly lower levels of apoptosis in infected cells and reduced in vivo tumorigenesis only partially, supporting the hypothesis that Trp149Stop polymorphism is retained in the general population and predisposes to cancer because of a reduction, but not full loss, of normal ARLTS1 function.

Thyroid cancer is frequently associated with the oncogenic conversion of the RET receptor tyrosine kinase. RET gene rearrangements, which lead to the generation of chimeric RET/papillary thyroid carcinoma (PTC) oncogenes, occur in PTC, whereas RET point mutations occur in familial multiple endocrine neoplasia type 2 (MEN2) and sporadic medullary thyroid carcinomas (MTC). We showed previously that the expression of the receptor-type protein tyrosine phosphatase J (PTPRJ) is suppressed in neoplastically transformed follicular thyroid cells. We now report that PTPRJ coimmunoprecipitates with wild-type RET and with the MEN2A-associated RET(C634R) oncoprotein but not with the RET/PTC1 and RET-MEN2B isoforms. Using mutated forms of PTPRJ and RET-MEN2A, we show that the integrity of the respective catalytic domains is required for the PTPRJ/RET-MEN2A interaction. PTPRJ expression induces dephosphorylation of the RET(C634R) and, probably via an indirect mechanism, RET/PTC1 oncoproteins on two key RET autophosphorylation sites (Tyr1062 and Tyr905). This results in a significant decrease of RET-induced Shc and extracellular signal-regulated kinase 1/2 phosphorylation levels. In line with this finding, adoptive PTPRJ expression reduced the oncogenic activity of RET(C634R) in an in vitro focus formation assay of NIH3T3 cells. As expected from the coimmunoprecipitation results, the RET(M918T) oncoprotein, which is associated to MEN2B and sporadic MTC, was resistant to the dephosphorylating activity of PTPRJ. Taken together, these findings identify RET as a novel substrate of PTPRJ and suggest that PTPRJ expression levels may affect tumor phenotype associated with RET/PTC1 and RET(C634R) mutants. On the other hand, resistance to PTPRJ may be part of the mechanism of RET oncogenic conversion secondary to the M918T mutation.

Purpose: Expression of the FHIT protein is lost or reduced in most solid tumors and a significant fraction of hematopoietic malignancies. Adenovirus 5 (Ad5) virus or adeno-associated viral vectors have been used to study the tumor suppressor function of FHIT in solid tumors, but these tools have not been effective in leukemias. We have generated a chimeric FHIT-containing adenovirus composed of Ad5 and the group B adenovirus called F35 with which we have been able to efficiently infect hematopoietic cells., Experimental Design: Infection efficiency of Ad5/F35-FHIT and Ad5/F35-GFP viruses was tested in leukemia cell lines that lacked FHIT expression, and biological effects of successful infection were assessed. An acute myelogenous leukemia, a chronic myelogenous leukemia, and four acute lymphoblastic leukemia human cell lines were examined as well as two EBV-transformed B lymphoblastoid cell lines that expressed endogenous FHIT., Results: Two of four acute lymphoblastic leukemia cell lines, Jurkat and MV4;11, which were efficiently infected with Ad5/F35-FHIT, underwent growth suppression and massive induction of apoptosis without apparent activation of caspase-8 or caspase-2 and late activation of caspase-3. Treatment of infected cells with caspase-9 and caspase-3 inhibitors partially blocked FHIT-induced apoptosis. The two remaining infected acute lymphoblastic leukemia cell lines, Molt-3 and RS4;11, were apparently unaffected. Restoration of FHIT expression in the chronic myelogenous leukemia K562 cell line and the acute myelogenous leukemia KG1a cell line also induced apoptosis but at later time points than seen in the acute lymphoblastic leukemia Jurkat and MV4;11 cell lines. I.v. injection of Ad5/F35-FHIT-infected Jurkat cells resulted in abrogation of tumorigenicity in the NOD/SCID xenogeneic engraftment model., Conclusion: FHIT restoration in some FHIT-deficient leukemia cells induces both antiproliferative and proapoptotic effects involving the intrinsic caspase apoptotic pathway.

The WW domain-containing oxidoreductase, WWOX, is a tumor suppressor that is deleted or altered in several cancer types. We recently showed that WWOX interacts with p73 and AP-2gamma and suppresses their transcriptional activity. Yes-associated protein (YAP), also containing WW domains, was shown to associate with p73 and enhance its transcriptional activity. In addition, YAP interacts with ErbB-4 receptor tyrosine kinase and acts as transcriptional coactivator of the COOH-terminal fragment (CTF) of ErbB-4. Stimulation of ErbB-4-expressing cells with 12-O-tetradecanoylphorbol-13-acetate (TPA) results in the proteolytic cleavage of its cytoplasmic domain and translocation of this domain to the nucleus. Here we report that WWOX physically associates with the full-length ErbB-4 via its first WW domain. Coexpression of WWOX and ErbB-4 in HeLa cells followed by treatment with TPA results in the retention of ErbB-4 in the cytoplasm. Moreover, in MCF-7 breast carcinoma cells, expressing high levels of endogenous WWOX, endogenous ErbB-4 is also retained in the cytoplasm. In addition, our results show that interaction of WWOX and ErbB-4 suppresses transcriptional coactivation of CTF by YAP in a dose-dependent manner. A mutant form of WWOX lacking interaction with ErbB-4 has no effect on this coactivation of ErbB-4. Furthermore, WWOX is able to inhibit coactivation of p73 by YAP. In summary, our data indicate that WWOX antagonizes the function of YAP by competing for interaction with ErbB-4 and other targets and thus affect its transcriptional activity.

Purpose: WW domain-containing oxidoreductase (WWOX) is a tumor suppressor gene that maps to the common fragile site FRA16D on chromosome 16q23.3-24.1. To investigate the role of the WWOX gene in the development of gastric carcinoma, we examined a large series of primary adenocarcinomas and nine gastric cancer cell lines for the expression of Wwox., Experimental Design: Loss of heterozygosity, reverse-transcription-PCR, and immunohistochemistry were used to assess the role of WWOX in stomach cancer. A total of 81 primary gastric adenocarcinoma were analyzed., Results: Loss of heterozygosity was observed in 31% of the cases and loss of Wwox protein expression was found in 65% of gastric adenocarcinoma primary specimens and 33% of gastric cancer cell lines. In addition, we found a high correlation between Wwox and Fhit protein expression., Conclusions: Our results indicate that alterations of the WWOX gene may be involved quite frequently in gastric tumorigenesis. Our data could be used in future studies to develop diagnostic and targeted therapy of stomach cancer.

Purpose: WWOX (WW domain containing oxidoreductase) is a tumor suppressor gene that maps to the common fragile site FRA16D. We showed previously that WWOX is frequently altered in human lung and esophageal cancers. The purpose of this study was to delineate more precisely the role of WWOX in pancreatic carcinogenesis., Experimental Design: We analyzed 15 paired pancreatic adenocarcinoma samples and 9 pancreatic cancer cell lines for WWOX alterations. Colony assay and cell cycle analysis were also performed to evaluate the role of the WWOX as a tumor suppressor gene., Results: Loss of heterozygosity at the WWOX locus was observed in 4 primary tumors (27%). Methylation analysis showed that site-specific promoter hypermethylation was detected in 2 cell lines (22%) and treatment with the demethylating agent 5-aza-2'-deoxycytidine demonstrated an increase in the expression of WWOX. In addition, 2 primary tumor samples (13%) showed promoter hypermethylation including the position of site-specific methylation. Transcripts missing WWOX exons were detected in 4 cell lines (44%) and in 2 tumor samples (13%). Real-time reverse transcription PCR revealed a significant reduction of WWOX expression in all of the cell lines and in 6 primary tumors (40%). Western blot analysis showed a significant reduction of the WWOX protein in all of the cell lines. Furthermore, transfection with WWOX inhibited colony formation of pancreatic cancer cell lines by triggering apoptosis., Conclusion: These results indicate that the WWOX gene may play an important role in pancreatic tumor development.

The WW domain containing oxidoreductase (WWOX) gene was recently identified as a candidate tumor suppressor gene at a common fragile site, FRA16D. Because the fragile histidine triad (FHIT) gene, a tumor suppressor gene encompassing the most active, common fragile site FRA3B, is frequently deleted in various cancers, we evaluated the expression of WWOX and FHIT in 74 cases of primary hematopoietic neoplasias and 20 leukemia cell lines. Aberration or absence of WWOX transcripts was detected in 51% of the primary cases and 55% of cell lines, and three WWOX nucleotide variants were detected among the leukemia cell lines. FHIT expression was absent or altered in 36% of the primary cases and 15% of cell lines. The occurrence of aberrant FHIT reverse transcription-PCR products correlated significantly with the occurrence of WWOX alterations. Wild-type transcripts of both genes were expressed in normal hematopoiesis along with a small fraction of short transcripts. A DNA blot study showed that WWOX and FHIT genes were deleted in 2 of 18 cases with primary acute leukemias; both genes were not expressed in the 2 cases. Furthermore, treatment of cells with a demethylating or histone acetylating agent in culture resulted in increased expression of WWOX and FHIT mRNA in leukemia cells. Conclusions are that WWOX expression is frequently altered or absent in hematopoietic disorders, often in association with FHIT alterations, and that alterations of these fragile genes may result not only from genomic deletions but also from epigenetic modifications associated with expression of fragility.

Promoter hypermethylation is an alternative way to inactivate tumor suppressor genes in cancer. Alterations of chromosome 3p are frequently involved in many types of cancer, including esophageal squamous cell carcinoma. Here, we investigated the methylation status and loss of heterozygosity (LOH) of 3p tumor suppressor genes. We examined the promoter methylation status of von Hippel-Lindau disease (VHL), retinoic acid receptor beta (RAR-beta), RAS association domain family 1A (RASSF1A), and fragile histidine triad (FHIT) genes in 22 esophageal squamous cell carcinoma cell lines and 47 primary tumors and corresponding noncancerous tissues by a methylation-specific PCR. In addition, we analyzed 47 paired samples for LOH at eight loci on chromosome 3p. Hypermethylation in VHL, RAR-beta, RASSF1A, and FHIT was detected in 36, 73, 73, and 50% of tumor cell lines, respectively. In primary tumors, hypermethylation in VHL, RAR-beta, RASSF1A, and FHIT was detected in 13, 55, 51, and 45%, respectively. In corresponding noncancerous tissues, hypermethylation in RAR-beta and FHIT was frequently detected in 38 and 30%, respectively, whereas no VHL hypermethylation and only 4% of RASSF1A hypermethylation were detected. Furthermore, in clinical stages I and II, hypermethylation in RAR-beta (67%) and FHIT (78%) was frequently detected, whereas no VHL hypermethylation and 11% of RASSF1A hypermethylation were detected. On the other hand, the correlation between FHIT hypermethylation and LOH at FHIT region was statistically significant (P = 0.008). Our findings suggest that hypermethylation of the RAR-beta and FHIT may play an important role in the early stage of esophageal squamous cell carcinogenesis. In addition, FHIT may be inactivated in accordance with the two-hit inactivation model, involving deletion of one allele and hypermethylation of the other.

The aim of this study was to evaluate the promoter methylation status and loss of heterozygosity (LOH) of the SEMA3B in non-small cell lung cancers (NSCLCs). We analyzed the methylation status of semaphorin 3B (SEMA3B) promoter and LOH at 3p21.3 in eight NSCLC cell lines and 27 primary tumors. Hypermethylation of SEMA3B was found in 50% of the cell lines and 41% of the primary tumors studied. The presence of hypermethylation was statistically associated with loss of SEMA3B expression in both cell lines (P = 0.02) and primary tumors (P < 0.01). There was no correlation between SEMA3B and tumor stage. On the other hand, the correlation between SEMA3B methylation status and LOH at 3p21.3 was significant (P = 0.02). Notably, 7 of 8 tumors with both hypermethylation and LOH of SEMA3B showed the absence of the expression. Treatment with 5-AZAC restored SEMA3B expression in NSCLC cell line. These results indicate that SEMA3B gene alterations may play a important role in the malignant transformation of NSCLC via a two-hit mechanism, including epigenetic changes and allelic loss, for tumor suppressor gene inactivation.

Purpose: The RAS association domain family 1A (RASSF1A) gene, a candidate tumor suppressor gene, is frequently inactivated by hypermethylation of its promoter region in several human cancers. The aim of this study was to evaluate the promoter methylation status of the RASSF1A in esophageal squamous cell carcinoma., Experimental Design: We analyzed the methylation status of RASSF1A promoter by methylation-specific PCR in 23 esophageal squamous cell carcinoma cell lines and 48 primary tumors., Results: Hypermethylation of RASSF1A was found in 74% of cell lines and 52% of primary tumors. The presence of hypermethylation was statistically associated with loss of RASSF1A mRNA expression in both cell lines (P = 0.007) and primary tumors (P = 0.003). There was a statistically significant correlation between the presence of hypermethylation and tumor stage (P = 0.009)., Conclusions: Our findings suggest that epigenetic silencing of RASSF1A gene expression by promoter hypermethylation could play an important role in primary esophageal squamous cell carcinogenesis.

The fragile histidine triad (FHIT) gene at chromosome 3p14.2 is a tumor suppressor gene that is altered mainly by deletion in a large fraction of human tumors, including breast cancers. To evaluate the potential of FHIT gene therapy in this type of cancer, we have studied the biological effects of adenoviral FHIT transduction (Ad-FHIT) in breast cancer cell lines. The results showed that, after FHIT restoration in BT-549, MDA-MB-436, and HCC1806 cells, they underwent apoptosis by activation of the intrinsic pathway. In all three cell lines infected with Ad-FHIT, we have found activation of caspase-2, which is required for permeabilization of mitochondria, release of cytochrome c, and apoptosis. Furthermore, Fhit overexpression produces alteration in cell cycling properties, as well as reduction of the tumorigenic potential in nude mice.

WWOX (WW domain containing oxidoreductase), a putative tumor suppressor gene that maps to the common fragile site FRA16D on chromosome 16q23.3-24.1, is altered in breast, esophageal, and ovarian cancer. Because the FRA3B/FHIT locus at 3p14.2 is a preferential target for genetic changes caused by tobacco smoke, we intended to evaluate the status of the FRA16D/WWOX gene in non-small cell lung cancer; we have analyzed 27 paired normal and tumor lung tissues and 8 lung cancer cell lines for WWOX alterations by reverse transcriptase-PCR, loss of heterozygosity, and mutation analysis. Transcripts missing WWOX exons were detected in 7 primary tumors (7 of 27; 25.9%) and 5 of 8 cell lines. In addition, loss of heterozygosity at the WWOX locus was observed in 10 primary tumors (10 of 27; 37.0%). We conclude that WWOX alterations occur in a significant fraction of lung cancers and may contribute to the pathogenesis of non-small cell lung cancer.

We demonstrated previously that rat tyrosine phosphatase r-PTPeta expression was suppressed in rat and human thyroid neoplastic cells, and that restoration of r-PTPeta expression reverted the malignant phenotype. To investigate the potential of this gene for cancer therapy, we generated an adenovirus carrying the r-PTPeta cDNA (Ad-r-PTPeta). This virus infected human thyroid carcinoma cells and overexpressed the r-PTPeta protein. Overexpression of r-PTPeta significantly inhibited the growth of four thyroid carcinoma cell lines. Cell growth inhibition was associated with down-regulation of extracellular signal-regulated kinase 1/2 activity, with increased levels of the cell-cycle inhibitor p27(kip1) protein and with dephosphorylation of PLCgamma1, a substrate of DEP-1, the human homologue of r-PTPeta. Finally, the growth of xenograft tumors induced in athymic mice by anaplastic thyroid carcinoma ARO cells transduced with the Ad-r-PTPeta virus was drastically reduced. These data suggest that gene therapy based on restoration of PTPeta function has potential in the treatment of human thyroid malignant neoplasias.

The WWOX (WW domain containing oxidoreductase) gene was recently identified as a candidate tumor suppressor gene at 16q23.3-24.1, a chromosome region that spans the common fragile site FRA16D. To evaluate the potential role of the WWOX gene in esophageal squamous cell carcinomas, we examined 36 tumors for genetic alterations of the WWOX gene. Loss of heterozygosity (LOH) at the WWOX locus was observed in 14 (39%) tumors. A tumor-specific missense mutation was found in one tumor, and LOH analysis had shown that the other allele was missing. Furthermore, we detected aberrant WWOX gene transcripts with absence of exons 6-8 in two tumors, and complete absence of transcript in one tumor. These results indicate that alteration and inactivation of the WWOX gene may play a role in esophageal squamous cell carcinogenesis.