Molecular cytogenetic definition of three distinct chromosome arm 14q deletion intervals in gastrointestinal stromal tumors

NDRG2 acts as a negative regulator of the progression of small-cell lung cancer through the modulation of the PTEN-AKT-mTOR signalling cascade

N-myc downstream-regulated gene 2 (NDRG2) has been recognised as a negative regulator of the progression of numerous tumours, yet its specific role in small-cell lung carcinoma (SCLC) is not fully understood. The purpose of the current study was to investigate the biological role and mechanism of NDRG2 in SCLC. Initial investigation using the Gene Expression Omnibus (GEO) dataset revealed marked downregulation of NDRG2 transcripts in SCLC. The decreased abundance of NDRG2 in SCLC was verified by examining clinical specimens. Increasing NDRG2 expression in SCLC cell lines caused significant changes in cell proliferation, cell cycle progression, colony formation, and chemosensitivity. NDRG2 overexpression decreased the levels of phosphorylated PTEN, AKT and mTOR. In PTEN-depleted SCLC cells, the upregulation of NDRG2 did not result in any noticeable impact on AKT or mTOR activation. Additionally, the reactivation of AKT reversed the antitumour effects of NDRG2 in SCLC cells. Notably, increasing NDRG2 expression retarded the growth of SCLC cell-derived xenografts in vivo. In conclusion, NDRG2 serves as an inhibitor of SCLC, and its cancer-inhibiting effects are achieved through the suppression of AKT/mTOR via the activation of PTEN. This work suggests that NDRG2 is a potential druggable target for SCLC treatment.

Dehydrogenase/reductase SDR family member 2 silencing sensitizes an oxaliplatin‑resistant cell line to oxaliplatin by inhibiting excision repair cross‑complementing group 1 protein expression

Oxaliplatin (Oxa)-based chemotherapy is widely used as the first-line treatment for colorectal cancer (CRC). However, Oxa-resistance is common for many postoperative CRC patients. To explore drug resistance in CRC, an Oxa-resistant cell line, HCT116/Oxa, was established from parental HCT116 cells. These Oxa-resistant cells exhibited characteristics of epithelial-mesenchymal transition (EMT) and a higher migratory capacity than parental cells. Protein profiles of HCT116/Oxa and HCT116 cells were compared using a tandem mass tag-based quantitative proteomics technique. The protein dehydrogenase/reductase SDR family member 2 (DHRS2) was revealed to be highly expressed in HCT116/Oxa cells. Silencing of DHRS2 in HCT116/Oxa cells effectively restored Oxa-sensitivity by suppressing the expression of excision repair cross-complementing group 1 protein via a p53-dependent pathway, and reversed the EMT phenotype. Overall, the suppression of DHRS2 expression may be a promising strategy for the prevention of Oxa-resistance in CRC.

DHRS2 mediates cell growth inhibition induced by Trichothecin in nasopharyngeal carcinoma

BACKGROUND

Cancer is fundamentally a deregulation of cell growth and proliferation. Cancer cells often have perturbed metabolism that leads to the alteration of metabolic intermediates. Dehydrogenase/reductase member 2 (DHRS2) belongs to short-chain alcohol dehydrogenase/reductase (SDR) superfamily, which is functionally involved in a number of intermediary metabolic processes and in the metabolism of lipid signaling molecules. DHRS2 displays closely association with the inhibition of cell proliferation, migration and quiescence in cancers.

METHODS

3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4- sulfophenyl)-2H-tetrazolium (MTS), 5-ethynyl-2'-deoxyuridine (EdU) and colony formation assays were applied to evaluate the proliferative ability of nasopharyngeal carcinoma (NPC) cells. We performed lipid metabolite profiling using gas chromatography coupled with mass spectrometry (GC/MS) to identify the proximal metabolite changes linked to DHRS2 overexpression. RNA sequencing technique combined with differentially expressed genes analysis was applied to identify the expression of genes responsible for the anti-tumor effect of trichothecin (TCN), a natural sesquiterpenoid compound isolated from an endophytic fungus.

RESULTS

Our current findings reveal that DHRS2 affects lipid metabolite profiling to induce cell cycle arrest and growth inhibition in NPC cells. Furthermore, we demonstrate that TCN is able to induce growth inhibition of NPC in vitro and in vivo by up-regulating DHRS2.

CONCLUSIONS

Our report suggests that activating DHRS2 to reprogram lipid homeostasis may be a target for the development of targeted therapies against NPC. Moreover, TCN could be exploited for therapeutic gain against NPC by targeting DHRS2 and it may also be developed as a tool to enhance understanding the biological function of DHRS2.

DHRS2 inhibits cell growth and motility in esophageal squamous cell carcinoma

Esophageal squamous cell carcinoma (ESCC) is highly prevailing in Asia and it is ranked in the most aggressive squamous cell carcinomas. High-frequency loss of heterozygosity occurred in chromosome 14q11.2 in many tumors including ESCC, suggesting that one or more tumor-suppressor genes might exist within this region. In this study, we identified the tumor-suppressing role of DHRS2 (short-chain dehydrogenase/reductase family, member 2) at 14q11.2 in ESCCs. Downregulation of DHRS2 occurred in 30.8% of primary ESCC tumor tissues vs paired non-tumorous tissues. DHRS2 downregulation was associated significantly with ESCC invasion, lymph nodes metastasis and clinical staging (P<0.001). Survival analysis revealed that DHRS2 downregulation was significantly associated with worse outcome of patients with ESCC. In vitro and in vivo studies indicated that both DHRS2 variants could suppress cell proliferation and cell motility. Moreover, we demonstrated that DHRS2 could reduce reactive oxygen species and decrease nicotinamide adenine dinucleotide phosphate (oxidized/reduced), increase p53 stability and decrease Rb phosphorylation; it also decreased p38 mitogen-activated protein kinase phosphorylation and matrix metalloproteinase 2. In summary, these findings demonstrated that DHRS2 had an important part in ESCC development and progression.

Genetic progression in gastrointestinal stromal tumors: mechanisms and molecular interventions

Gastrointestinal stromal tumors (GISTs) are the most common sarcomas in humans. Constitutively activating mutations in the KIT or PDGFRA receptor tyrosine kinases are the initiating oncogenic events. Most metastatic GISTs respond dramatically to therapies with KIT/PDGFRA inhibitors. Asymptomatic and mitotically-inactive KIT/PDGFRA-mutant "microGISTs" are found in one third of adults, but most of these small tumors never progress to malignancy, underscoring that a progression of oncogenic mutations is required. Recent studies have identified key genomic abnormalities in GIST progression. Novel insights into the genetic progression of GISTs are shedding new light on therapeutic innovations.

Chromosomal aberrations in primary PDGFRA-mutated gastrointestinal stromal tumors

Approximately 15% of gastrointestinal stromal tumors (GISTs) harbor mutations in the platelet-derived growth factor receptor α (PDGFRA) gene. Chromosomal aberrations play a crucial role in tumor progression and correlate with clinical behavior. Imbalances, particularly in PDGFRA-mutated GISTs, have not yet been evaluated in larger series. We analyzed 53 PDGFRA-mutated GISTs (including 2 with corresponding metastases) for chromosomal imbalances by conventional comparative genomic hybridization and compared them with a historical collective of 122 KIT-mutated GISTs. PDGFRA exon 18 mutations (91% of cases) and exon 12 mutations (9% of cases) correlated significantly with gastric and intestinal sites, respectively. The most common aberrations were identical to those found in KIT-mutated GISTs, with -14q in 70%, -1p in 28%, and -22q in 17% of cases. Overall, there were significantly fewer chromosomal aberrations compared with KIT-mutated GISTs, with a mean of 2.8 (0.6 gains, 2.1 losses) aberrations per tumor. There was a statistically significant association of more than 5 chromosomal imbalances with intermediate/high-risk categories. Regarding specific chromosomal aberrations, -9p, -13q, and -22q correlated with intermediate/high risk, and -1p and +8q with poorer survival, although progression occurred in only 2 cases. Altogether, PDGFRA-mutated GISTs display the same chromosomal aberrations as KIT-mutated GISTs, although they have a lower degree of chromosomal instability in line with their generally favorable outcome.

A molecular portrait of gastrointestinal stromal tumors: an integrative analysis of gene expression profiling and high-resolution genomic copy number

In addition to KIT and PDGFRA mutations, sequential accumulation of other genetic events is involved in the development and progression of gastrointestinal stromal tumors (GISTs). Until recently, the significance of these other alterations has not been thoroughly investigated. We report the first study that integrates gene expression profiling and high-resolution genomic copy number analyses in GIST. Fresh tissue specimens from 25 patients with GIST were collected, and gene expression profiling and high-resolution genomic copy number analyses were performed, using Affymetrix U133Plus and SNP array 6.0. We found that all 21 mutant GIST patients showed both macroscopic cytogenetic alterations and cryptic microdeletions or amplifications, whereas 75% (three of four) of wild-type patients with GIST did not show genomic imbalances. The most frequently observed chromosomal alterations in patients with mutant GIST included 14q complete or partial deletion (17 of 25), 1p deletion (14 of 25) and 22q deletion (10 of 25). Genetic targets of the chromosomal aberrations were selected by integrated analysis of copy number and gene expression data. We detected the involvement of known oncogenes and tumor suppressors including KRAS in chr 12p amplification and KIF1B, PPM1A, NF2 in chr 1p, 14q and 22p deletions, respectively. The genomic segment most frequently altered in mutated samples was the 14q23.1 region, which contains potentially novel tumor suppressors, including DAAM1, RTN1 and DACT1. siRNA-mediated RTN1 downregulation showed evidence for the potential role in GIST pathogenesis. The combination of gene expression profiling and high-resolution genomic copy number analysis offers a detailed molecular portrait of GISTs, providing an essential comprehensive knowledge necessary to guide the discovery of novel target genes involved in tumor development and progression.

Mitochondrial Hep27 is a c-Myb target gene that inhibits Mdm2 and stabilizes p53

The ever-expanding knowledge of the role of p53 in cellular metabolism, apoptosis, and cell cycle control has led to increasing interest in defining the stress response pathways that regulate Mdm2. In an effort to identify novel Mdm2 binding partners, we performed a large-scale immunoprecipitation of Mdm2 in the osteosarcoma U2OS cell line. One significant binding protein identified was Hep27, a member of the short-chain alcohol dehydrogenase/reductase (SDR) family of enzymes. Here, we demonstrate that the Hep27 preprotein contains an N-terminal mitochondrial targeting signal that is cleaved following mitochondrial import, resulting in mitochondrial matrix accumulation of mature Hep27. A fraction of the mitochondrial Hep27 translocates to the nucleus, where it binds to Mdm2 in the central domain, resulting in the attenuation of Mdm2-mediated p53 degradation. In addition, Hep27 is regulated at the transcriptional level by the proto-oncogene c-Myb and is required for c-Myb-induced p53 stabilization. Breast cancer gene expression analysis correlated estrogen receptor (ER) status with Hep27 expression and p53 function, providing a potential in vivo link between estrogen receptor signaling and p53 activity. Our data demonstrate a unique c-Myb-Hep27-Mdm2-p53 mitochondria-to-nucleus signaling pathway that may have functional significance for ER-positive breast cancers.

Array comparative genomic hybridization analysis of chromosomal imbalances and their target genes in gastrointestinal stromal tumors

Gastrointestinal stromal tumor (GIST) is the most common mesenchymal tumor of the gastrointestinal tract. The tumors characteristically harbor KIT or PDGFRA mutations, and mutant tumors respond to imatinib mesylate (Glivectrade mark). Chromosomal imbalances resulting in altered gene dosage are known to have a role in the molecular pathogenesis of these tumors, but the target genes remain to be identified. The present study aimed to identify some of these genes. In total, 35 GIST samples were screened for chromosomal imbalances by array-based comparative genomic hybridization. A cDNA array was used to define the minimal common overlapping areas of DNA copy number change. Eight confirmative, replicate hybridizations were performed using an oligonucleotide array. The most recurrent copy number losses were localized to 14q, 22q, and 1p. Gains were less common with 8q being the most recurrent. Two recurrent deleted regions of 14q were 14q11.2 harboring the PARP2, APEX1, and NDRG2 genes and 14q32.33 harboring SIVA. Additional target candidates were NF2 at chromosome 22, CDKN2A/2B at 9p, and ENO1 at 1p for copy number losses, and MYC at 8q for copy number gains. Array CGH proved to be an effective tool for the identification of chromosome regions involved in the development and progression of GISTs.

An oncogenetic tree model in gastrointestinal stromal tumours (GISTs) identifies different pathways of cytogenetic evolution with prognostic implications

To model the cytogenetic evolution in gastrointestinal stromal tumour (GIST), an oncogenetic tree model was reconstructed using comparative genomic hybridization data from 203 primary GISTs (116 gastric and 87 intestinal GISTs, including 151 newly analysed cases), with follow-up available in 173 cases (mean 40 months; maximum 133 months). The oncogenetic tree model identified three major cytogenetic pathways: one initiated by -14q, one by -1p, and another by -22q. The -14q pathway mainly characterized gastric tumours with predominantly stable karyotypes and more favourable clinical course. On the other hand, the -1p pathway was more characteristic of intestinal GISTs, with an increased capacity for cytogenetic complexity and more aggressive clinical course. Loss of 22q, more closely associated with -1p than -14q, appeared to initiate the critical transition to an unfavourable cytogenetic subpathway. This -22q pathway included accumulation of +8q, -9p, and -9q, which could all predict disease-free survival in addition to tumour site. Thus, insights into the cytogenetic evolution obtained from oncogenetic tree models may eventually help to gain a better understanding of the heterogeneous site-dependent biological behaviour of GISTs.

High incidence of microscopic gastrointestinal stromal tumors in the stomach

Gastrointestinal stromal tumors (GISTs) are rare mesenchymal neoplasms with an annual incidence of approximately 10 to 20 per 1 million cases. Although pathologists have often observed incidental small GISTs in the stomach resected from patients with gastric cancer, no report on the real incidence of gastric GISTs is available. In this study, 100 whole stomachs resected from patients with gastric cancer were sectioned at 5-mm intervals and hematoxylin and eosin-stained slides (a mean of 130 slides for each case) were examined for microscopic GISTs. KIT (CD117), CD34, and desmin expression of the incidental tumors was evaluated by immunohistochemistry, and genomic DNA extracted from formalin-fixed and paraffin-embedded tumor tissues was analyzed for c-kit gene mutations in exon 11. In 35 of the 100 whole stomachs, we found 50 microscopic GISTs, all of which were positive for KIT and/or CD34 and negative for desmin. Most microscopic GISTs (45/50, 90%) were located in the upper stomach. Two of the 25 (8%) microscopic GISTs had c-kit gene mutations. Fifty-one leiomyomas with positive expression for desmin were observed in 28 of the 100 stomachs. Both leiomyomas and GISTs were found in 12 stomachs. These results indicate that microscopic GISTs are common in the upper portion of the stomach. Considering the annual incidence of clinical GISTs, only few microscopic GISTs may grow into a clinical size with malignant potential. Further studies are required to clarify the genetic events responsible for the transformation of microscopic GISTs to clinical GISTs.

Array Comparative Genomic Hybridization Reveals Distinct DNA Copy Number Differences between Gastrointestinal Stromal Tumors and Leiomyosarcomas

Leiomyosarcomas are spindle cell tumors showing smooth muscle differentiation. Until recently, most gastrointestinal stromal tumors (GIST) were also classified as smooth muscle tumors, but now GISTs are recognized as a separate entity, defined as spindle cell and/or epithelioid tumors localized in the gastrointestinal tract. Using microarray-based comparative genomic hybridization (array CGH), we have created a detailed map of DNA copy number changes for 7 GISTs and 12 leiomyosarcomas. Considerable gains and losses of chromosomal segments were observed in both tumor types. The most frequent aberration observed in GISTs was loss of chromosomes 14 and 22, with minimal recurrent regions in 14q11.2-q32.33 (71% of the tumors) and 22q12.2-q13.31 (100%). In leiomyosarcomas, frequent loss of chromosome 10 and 13q was observed, with minimal recurrent regions in 10q21.3 (75%) and 13q14.2-q14.3 (75%). Recurrent high-level amplification of 17p13.1-p11.2 was detected in leiomyosarcomas. Expression profiling using cDNA microarrays revealed four candidate genes in this region with high expression (AURKB, SREBF1, MFAP4, and FLJ10847). Altered expression of AURKB and SREBF1 has been observed previously in other malignancies. Hierarchical clustering of all samples separated GISTs and leiomyosarcomas into two distinct clusters. Statistical analysis identified six chromosomal regions, 1p36.11-p13.1, 9q21.11-9q34.3, 14q11.2-q23.2, 14q31.3-q32.33, 15q24.3-q26.3, and 22q11.21-q13.31, which were significantly different in copy number between GISTs and leiomyosarcomas. Our results show the potential of using array comparative genomic hybridization to classify histologically similar tumors such as GISTs and leiomyosarcomas.

An update on molecular genetics of gastrointestinal stromal tumours

Gastrointestinal stromal tumours (GISTs) are the most common primary mesenchymal tumours of the gastrointestinal tract. Most of them show activating mutations of the genes coding for KIT or platelet-derived growth factor receptor alpha (PDGFRalpha), two receptor tyrosine kinases (RTKs). The RTK inhibitor Imatinib (Gleevec, Novartis, Switzerland), induces regression of the tumour. The level of response to treatment, together with other clinicopathological parameters is related to the type and site of the activating mutation, thus suggesting that these tumours should be classified according to the molecular context. This is confirmed also by the phenomenon of the resistance to treatment, which arises because of different mechanisms (second mutation, amplification, activation of other RTKs) and can be fought only by specific RTK inhibitors, that are at present under development. RTK activation involves an homogeneous transduction pathway whose components (MAPK, AKT, PI3K, mTOR and RAS) are possible targets of new molecular treatment. A new paradigm of classification integrating the classic pathological criteria with the molecular changes will permit personalised prognosis and treatment.

[Gastrointestinal stromal tumors: definition, histological, immunohistochemical, and molecular features, and diagnostic strategy]

Gastrointestinal stromal tumors (GISTs) are the most frequent mesenchymal tumors of the gastrointestinal tract. Major advances in their definition and classification and the understanding of their molecular mechanisms have recently been made. These advances have resulted in the delineation of a treatment that has become a model of targeted therapy in oncology. GISTs are defined as tumors of the gastrointestinal tract, but also of the mesentery and peritoneum, constituted by a proliferation of usually spindle-shaped, rarely epithelioid cells, usually, but not consistently expressing the KIT protein. Most GISTs are associated with molecular abnormalities in two target genes: KIT (which encodes the KIT protein) and PDGFRA (which encodes the A chain of the PDGF receptor). The diagnosis of GIST relies on histological arguments (proliferation of spindle-shaped cells in 70% of cases, of epithelioid cells in 20%; histological variants are rare and sometimes misleading) and on immunohistochemical arguments (expression of KIT in 95%, usually associated with CD34 expression in 60%-70% of cases). The demonstration of mutations in target genes is required only in cases that are histologically suggestive but KIT-negative; beyond this indication, this is only undertaken in research protocols. The differential diagnosis of GIST includes the other mesenchymal tumors of the gastrointestinal tract, such as leiomyomas and leiomyosarcomas, and the digestive locations of some sarcomas; it relies on both histological and immunohistochemical arguments. The evaluation of the prognosis is essential. According to the current concept, every GIST carries a risk of malignancy, which may vary from very low to very high. Prognosis is based on a simple algorithm using two histoprognostic parameters, i.e., tumor size and mitotic index. The treatment of localized GIST is surgical resection, which must be complete; that of advanced or unresectable GIST is based on the use of a targeted therapy, imatinib, which is a pharmacological antagonist of the KIT protein. Proper understanding and utilisation of the diagnostic criteria and classification of GIST by pathologists are essential for good patient management.

Gastrointestinal stromal tumor (GIST) pathogenesis, familial GIST, and animal models

Once a poorly understood pathologic entity, gastrointestinal stromal tumor (GIST) has emerged in recent years as a distinct oncologic-molecular paradigm that is now a leading model for kinase-targeted therapies in Oncology. Most GISTs are KIT-expressing and KIT-signaling driven mesenchymal tumors, many of which have KIT-activating mutations. A small subset of GIST show activating mutations in PDGFRA, encoding for a related member of the type III receptor tyrosine kinase family. The revelation of KIT expression as a diagnostic signature of GIST has not only revolutionized the pathologic criteria in classifying GIST, but also shed light onto the histogenesis of these tumors. The similarities in KIT immunoreactivity and ultrastructural appearance between GISTs and the intestinal pacemaker, the interstitial cells of Cajal (ICC), suggested that GISTs derive from or differentiate toward the ICC lineage. KIT plays a significant role in proliferation, survival, and differentiation of hematopoietic stem cells, mast cells, melanocytes, and interstitial cells of Cajal; and activating KIT mutations have been identified in tumors affecting most of these cell lineages. The observation that KIT mutations may be inherited, as seen in familial GIST syndrome, was used to develop murine models harboring a germline gain-of-function mutation, as a model for studying of KIT oncogenic mechanisms. These murine models of human GIST promise to become powerful preclinical tools in elucidating oncogenic signaling mechanisms by using genetic approaches and targeted pharmacological intervention. As true animal models of human cancer, they provide superior information compared with the more commonly used xenografts and transgenic mouse models. This review summarizes the recent knowledge on the central role of KIT oncogenic activation and subsequent signal transduction in the pathogenesis of GIST. In addition, we provide an updated discussion on familial GIST syndrome in relationship to genotype-phenotype characteristics. A succinct description of the available murine models of human GIST is presented and their applicability in further understanding of the KIT oncogenic signaling, drug screening, and mechanisms of drug resistance is discussed. This is a US government work. There are no restrictions on its use.

Chromosomal Numerical Abnormality Profiles of Gastrointestinal Stromal Tumors

BACKGROUND

Biological variations in and the heterogeneity of gastrointestinal stromal tumors (GISTs) are well known, but chromosomal numerical abnormality (CNA) has not been fully examined especially in this context. The aim of this study is to test CNA as a possible biological predictor of biological behavior of GISTs.

METHOD

We applied microwave-assisted FISH protocol to pathological archives of GIST tumors displaying different clinical features to characterize the CNA profile of these tumors. A panel of 18 centromere enumeration probes (CEP) and 24 bacterial artificial chromosome (BAC) or P1-derived artificial chromosome (PAC) probes containing genes like Aurora kinases (AURKs) and other candidate genes involved in human carcinogenesis were used. CNA profiles, histopathological risk categorization and Ki-67 labeling indexes of 23 primary and/or metastatic GIST tumors of 12 subjects (both primary and metastatic in 7 subjects) were compared between primary GIST with and without metastases, and between metastatic and primary portions in 7 individuals.

RESULTS

CNA in the primary sites was more extensive in the GISTs with recurrence and metastasis than in those without, especially as to the loss of chromosome 20 and genomic imbalance of AURKA-containing BAC probe on 20q in the cases with metastasis. The consistent loss of one allele of chromosome 14q was also noted. Interestingly, both primary and metastatic tumors in identical individuals had similar CNA profiles.

CONCLUSION

The extent of CNA differed between GISTS with and without recurrence or metastasis; thus, FISH analysis of specimens from the primary sites may predict the biological behavior of this tumor.

Cutaneous aneurysmal fibrous histiocytoma with a t(12;19)(p12;q13) as the sole cytogenetic anomaly

We report a case of a 39-year-old woman with a recurrent aneurysmal fibrous histiocytoma of the right lower leg. Cytogenetic analysis of the tumor specimen disclosed a 46,XX,t(12;19)(p12;q13) karyotype. Multicolor fluorescence in situ hybridization (M-FISH), followed by conventional FISH analysis, confirmed the reciprocal translocation as the sole cytogenetic anomaly, and allowed for the positioning of chromosomes 12 and 19 breakpoints proximal to the BCL3 gene and between ETV6 and PIK3C2G gene loci, respectively. Our case highlights the importance of distinguishing this recurrent but benign lesion from similarly appearing malignant skin tumors. Cytogenetic analysis may contribute to the diagnosis of this uncommon but distinctive clinicopathological entity.

Array CGH analysis in primary gastrointestinal stromal tumors: Cytogenetic profile correlates with anatomic site and tumor aggressiveness, irrespective of mutational status

Gastrointestinal stromal tumors (GISTs) comprise a biologically diverse group of neoplasms with respect to activating mutations in either KIT or PDGFRA, histology, anatomical site of origin, and clinical aggressiveness. In this study, we applied the high resolution array-based comparative genomic hybridization (array-CGH) technology to 66 primary GISTs (40 gastric and 26 nongastric, 48 with KIT and 18 with PDGFRA mutations) for identification of novel high-level alterations and for characterization of genotype-related genomic changes. All cases had genomic imbalances with the highest occurrence of 14q (73%), 1p (62%), 22q (59%), 15q (38%), and 13q (29%) losses. Our data indicate that loss of chromosome 14 and/or 22 is an early change in GIST tumorigenesis irrespective of tumor genotype. Furthermore, DNA copy number changes showed a site dependent pattern. These included lower incidence of losses at 14q (87% vs. 35%), and higher frequency of losses at 1p (45% vs. 85%) and 15q (17% vs. 69%) in nongastric versus gastric site (P<0.001 for all). However, in the multivariate analysis with adjustment to tumor risk stratification, only the 14q loss site-dependent pattern of distribution retained its significance. These findings suggest that loss of 14q is a relatively less frequent genetic event in the development of nongastric GISTs, the lack of which is most likely substituted by the accumulation of 1p/15q and other changes. The novel minimal overlapping regions of deletion at 1p (1p36.32-1p35.2, 1p34.1, and 1p22.1-1p21.3), 13q (13q14.11-q14.2 and 13q32.3-q33.1), and 15q23 were delineated, which point to chromosomal regions that may harbor genes relevant to the development of these neoplasms.

Gastrointestinal stromal tumor: 5 years later

There is now considerable interest in gastrointestinal stromal tumor (GIST) because it can be treated effectively with a targeted molecular agent. The majority of GISTs contain an activating mutation in the KIT protooncogene or, occasionally, in the platelet-derived growth factor-alpha (PDGFRA) gene. Five years ago, imatinib mesylate, a specific molecular inhibitor of the protein products of these 2 genes, was applied to metastatic GIST. Approximately 80% of patients with metastatic GIST benefit from imatinib, although acquired resistance to the agent may develop. For patients with primary GIST, surgery remains the treatment of choice, and whether outcome is improved by adjuvant imatinib is currently under broad investigation. A combination of imatinib therapy and surgery also may be effective in a subset of patients with metastatic or unresectable primary GIST. In this review, the authors summarize the new multimodality approach to GIST. The integration of surgery and molecular therapy in GIST will serve as a prototype for the management of other solid tumors for which targeted agents become available.

Cloning, expression and chromosomal assignment of human pleckstrin 2

We report the isolation of human pleckstrin 2 cDNA. The cDNA contains a 1059 bp open reading frame encoding a polypeptide of 353 amino acid residues. The deduced amino acid sequence indicates that pleckstrin 2 contains two pleckstrin homology domains and a DEP (dishvelled, egl-10, and pleckstrin) domain and had a 95% identity with the sequence of mouse pleckstrin 2. Northern blot and a reverse transcription-coupled polymerase chain reaction analysis revealed that pleckstrin 2 mRNA is widely expressed in a variety of cell lines. The chromosomal location of the mouse pleckstrin 2 gene was on the D3 band of chromosome 12, as determined by fluorescence in situ hybridization and the human pleckstrin 2 gene was mapped to chromosome 14q24.1 by a bioinformatics analysis.

Patterns of gene amplification in gastrointestinal stromal tumors (GIST)

Gastrointestinal stromal tumors (GIST) are the most common primary mesenchymal tumors of the gastrointestinal tract (GIT). They represent a wide clinico-pathological spectrum of tumors. No single histological or clinical parameter can predict the prognosis while the response to therapy is related to the type of KIT or PDGFRA mutation. Cytogenetic and CGH studies have identified frequent gross chromosomal aberrations but the target genes of these changes are unknown. To determine whether known oncogenes take part in genomic rearrangements and to investigate the potential clinical significance of their amplifications, nine known oncogenes (CMYC, MDM2, GLI1, CDK4, HER2, EGFR1, CCND1, FGF3, EMS) were analyzed by fluorescent in situ hybridization (FISH) on a tissue microarray (TMA) containing 94 primary GIST. Clinical follow-up information was available for 57 of these patients. Amplification was found for CMYC in three of 90 (3.3%), for MDM2 in five of 94 (5.3%), for EGFR1 in five of 94 (5.3%), and for CCND1 in seven of 79 (8.9%) evaluable cases. No amplifications were seen for HER2, GLI1, CDK4, FGF3, and EMS. Amplifications of MDM2 and CCND1 were associated with clinical and histological malignancy. In conclusion, our data show that gene amplification does occur in a subset of GIST. Identification of MDM2/CCND1 amplification may represent another molecular feature that could help in the evaluation of the behavior of GISTs.

Monochromosome transfer provides functional evidence for growth-suppressive genes on chromosome 14 in nasopharyngeal carcinoma

In many cancers, including nasopharyngeal carcinoma (NPC), extensive and multiple regions of allelic loss occur on chromosome 14. However, to date no functionally conclusive tumor suppressor genes have yet been identified on this chromosome. Through use of the monochromosome transfer technique, this study provides functional evidence for the importance of two discrete regions of chromosome 14. A newly established A9 mouse donor cell line containing an intact copy of chromosome 14 was used for transfer of this intact chromosome into the NPC HONE1 cell line. Twelve independently established microcell hybrids demonstrated uniform loss of specific chromosome 14 loci from both endogenous and exogenous alleles. By microsatellite typing and fluorescence in situ hybridization with BAC probes, the two critical regions were localized to 14q11.2-13.1 and 14q32.1. Selective elimination of these regions during hybrid selection was strongly associated with both hybrid survival and tumor growth in vivo. This functional evidence now narrows down the candidate areas for further studies and suggests that at least two hitherto unidentified growth-related genes localized on two critical regions of chromosome arm 14q play an important role in tumorigenesis.

Pathology and diagnostic criteria of gastrointestinal stromal tumors (GISTs): a review

Gastrointestinal stromal tumor (GIST) is the designation for the specific c-kit expressing and Kit-signaling driven mesenchymal tumors, many of which have Kit-activating mutations. The specific identification of GIST has become increasingly important because a Kit-selective tyrosine kinase inhibitor, imatinib (Glivec, formerly known as STI571, Novartis Pharma AG, Basel, Switzerland), has shown promise as an effective adjuvant therapy treatment. GISTs are the most common mesenchymal tumors of the gastrointestinal (GI) tract. We estimate the frequency of malignant GISTs as 20% to 30% of the frequency of all soft-tissue sarcomas, but small benign tumors, often found incidentally during unrelated surgery or autopsy, are probably much more common. Older adults are most at risk for GIST; very rarely, GIST occurs in children and young adults (sometimes connected with Carney's triad), or on a familial basis. GISTs have been documented in all parts of the GI tract. A great majority of them occur in the stomach (60% to 70%) and small intestine (25% to 35%), with rare occurrence in the colon and rectum (5%), esophagus (<2%) and appendix. Some GISTs are primary in the omentum, mesentery or retroperitoneum, and are unrelated to the tubular GI tract. GISTs can be histologically identified as highly cellular spindle cell or epithelioid mesenchymal tumors, and morphology is somewhat site-dependent. However, common to all these tumors is expression of Kit (CD117 antigen), which is a major diagnostic criterion. Few other Kit-positive mesenchymal tumors of the GI tract are likely to be confused with GISTs; exceptions are metastatic melanoma and related tumors and malignant vascular tumors. Additional diagnostic criteria include common positivity for CD34 (70%), variable expression of smooth muscle actins (20% to 30%) and S100 protein (10%) and almost uniform negativity for desmin (only 2% to 4% of GISTs are positive). Although the prediction of malignancy in this tumor group is notoriously difficult, tumors that have mitotic activity counts exceeding 5 per 50 high power fields (HPF) or those larger than 5 cm have a high frequency of intra-abdominal recurrence and liver metastasis. In contrast, tumors smaller than 2 cm and those with mitotic activity counts <5 per 50 HPF are likely to be benign. These diagnostic criteria leave an inevitable gray area in the separation of benign and malignant tumors. Kit-activating mutations can be detected in at least 60% to 70% of GIST cases. Most of the mutations, in-frame deletions of several codons, are located in the juxtamembrane domain (exon 11) of the gene. Less commonly, mutations have been detected in the extracellular domain (exon 9), and tyrosine kinase domains (exons 13 and 17). Functional analysis of the different c-kit mutations and their impact on the response to tyrosine kinase inhibitors are under intense investigation.

The complexity of KIT gene mutations and chromosome rearrangements and their clinical correlation in gastrointestinal stromal (pacemaker cell) tumors

Gastrointestinal stromal (pacemaker cell) tumors (GIST/GIPACTs) are frequently associated with activating KIT mutations, primarily of exon 11 and rarely of exons 9 and 13, as well as certain chromosome rearrangements. Reports regarding the frequency and prognostic significance of KIT mutations are conflicting and few cases have been completely sequenced. Furthermore, there are few detailed analyses of chromosome alterations in GIST/GIPACTs. In a detailed analysis of 14 GIST/GIPACTs from 12 patients, we found a wider spectrum of KIT mutations than previously reported, including 11 different in-frame mutations involving exons 11, 14, and 15. No mutations were detected in four malignant tumors. The shorter (GNNK-) KIT isoform was preferentially expressed. Cytogenetic and spectral karyotype analyses of 10 tumors revealed clonal abnormalities in eight tumors; the most common were terminal 1p deletions and losses of chromosomes 14 and/or 22. Neither KIT mutation status nor chromosome aberrations correlated with tumor phenotype or clinical behavior in our series. Collectively, these findings indicate that the role of KIT mutations and chromosomal rearrangements in the pathogenesis of GIST/GIPACTs are more complex than previously recognized.