A putative oncogenic role for MPP11 in head and neck squamous cell cancer

Genetic alterations of chromosome 7 are common in human cancer. Furthermore, previous studies have supported the presence of a gene important in a broad range of cancers at 7q22-31.1. There is evidence that supports an oncogenic function for this putative gene, as well as evidence that supports a tumor suppressive role. In this study, we used a cross-species candidate gene approach in combination with physical mapping to identify MPP11 as a candidate for the putative cancer-related activity at 7q22-31.1. We then analyzed primary head and neck squamous cell tumors (HNSCCs) for loss of heterozygosity/allelic imbalance (LOH/AI) at the MPP11 genomic locus. Thirty-eight percent of tumors examined displayed LOH/AI involving the MPP11 genomic locus. Mutation analysis of MPP11 in the latter samples did not identify any inactivating mutations. However, immunohistochemical staining of primary tumor sections and Western blot analysis of HNSCC cell lines revealed a tumor-specific high level of expression of MPP11p. Fluorescence in situ hybridization analysis done on the cell lines identified increased chromosome 7 copy number with a concomitant increase in MPP11 copy number. These results suggest an oncogenic role for MPP11 in HNSCC.

Two distinct regions of loss on chromosome arm 4q in primary head and neck squamous cell carcinoma

OBJECTIVE

To more clearly define the frequency and the regions of chromosome arm 4q loss in head and neck squamous cell carcinoma.

DESIGN

A retrospective microsatellite analysis of DNA from previously microdissected primary tumor samples.

SETTING

Academic medical center.

PATIENTS AND METHODS

One hundred primary tumor samples from patients with head and neck squamous cell carcinoma were analyzed for loss of heterozygosity on the long arm of chromosome 4. The Kaplan-Meier method was used to estimate survival for 97 patients for whom clinical data were available. The Cox proportional hazards model was used to compare survival, and logistic regression was used to search for associations between clinical tumor characteristics and 4q status.

RESULTS

Analysis of 33 polymorphic microsatellite markers identified 51 samples (51%) exhibiting loss of heterozygosity of 4q in at least 1 locus. Eighteen tumors revealed loss at all informative markers, indicating monosomy or complete deletion of 4q. Thirty-three tumors displayed partial loss of heterozygosity and delineated 2 minimal areas of loss at 4q2324 and 4q2829. Eleven tumors displayed loss solely at the 4q2324 region, 13 tumors displayed deletions confined to the 4q2829 region, and 9 tumors displayed selective loss at both regions. A separate analysis in a subset of 94 primary head and neck tumors was done to further delineate the minimal area of chromosomal loss at 4q2324. Analysis of 8 markers in this region allowed us to identify the smallest region of loss between markers D4S2986 and D4S1564 (a distance of 2 centimorgans). Review of the clinical records of 97 patients revealed no statistically significant association between 4q status and any clinical variable, including survival.

CONCLUSION

These results confirm a high frequency of chromosome arm 4q loss in primary head and neck squamous cell carcinoma and might demarcate 2 novel putative suppressor loci involved in progression of this carcinoma.

Alcohol consumption and cigarette smoking increase the frequency of p53 mutations in non-small cell lung cancer

Epidemiological studies have demonstrated a strong association between tobacco use and lung cancer; however, the genetic targets of these carcinogens and the role of other environmental agents in this process have yet to be defined. We examined the contribution of alcohol use and cigarette smoking top53 gene mutations in patients with non-small cell lung cancer. Mutations of the p53 gene were detected by sequence analysis in 105 patients with non-small cell lung cancer. Patient characteristics significantly associated with p53 gene mutations were determined using logistic regression. Mutations in the p53 gene were present in 53% of the patients (56 of 105). p53 mutations were more common in patients who used alcohol than in patients who consumed less than one drink per day (72 versus 39%; P = 0.003), and were detected more often smokers than nonsmokers (58% versus 10%, P = 0.02). Mutations in the p53 gene were present more often (P = 0.01) in alcohol drinkers who smoked cigarettes [76% (31 of 41)], than in nondrinkers (<1 drink per day) who smoked cigarettes [42% (20 of 48)] or in nondrinkers who did not smoke [14% (1 of 7)]. In conclusion, alcohol consumption and tobacco use are both associated with p53 mutations in non-small cell lung cancer. The link between exposure to both alcohol and tobacco and p53 mutations raises the possibility that alcohol may enhance the mutagenic effects of cigarette smoke in the lung.

Interleukin-9 upregulates mucus expression in the airways

Interleukin (IL)-9 has recently been shown to play an important role in allergic disease because its expression is strongly associated with the degree of airway responsiveness and the asthmatic-like phenotype. IL-9 is a pleiotropic cytokine that is active on many cell types involved in the allergic immune response. Mucus hypersecretion is a clinical feature of chronic airway diseases; however, the mechanisms underlying the induction of mucin are poorly understood. In this report, we show that IL-9 regulates the expression of a subset of mucin genes in lung cells both in vivo and in vitro. In vivo, the constitutive expression of IL-9 in transgenic mice results in elevated MUC2 and MUC5AC gene expression in airway epithelial cells and periodic acid-Schiff-positive staining (reflecting mucous glycogenates). Similar results were observed in C57BL/6J mice after IL-9 intratracheal instillation. In contrast, instillation of the T helper 1-associated cytokine interferon gamma failed to induce mucin production. In vitro, our studies showed that IL-9 also induces expression of MUC2 and MUC5AC in human primary lung cultures and in the human muccoepidermoid NCI-H292 cell line, indicating a direct effect of IL-9 on inducing mucin expression in these cells. Altogether, these results suggest that upregulation of mucin by IL-9 might contribute to the pathogenesis of human inflammatory airway disorders, such as asthma. These data extend the role of the biologic processes that IL-9 has on regulating the many clinical features of asthma and further supports the IL-9 pathway as a key mediator of the asthmatic response.

Frequent gain of the p40/p51/p63 gene locus in primary head and neck squamous cell carcinoma

We have identified a new human p53 homologue, p40 (p51/p63). This gene was mapped to the distal arm of 3q and was found to be essential for normal epithelial development. We used microsatellite and FISH analyses to search for genetic alterations of p40 in primary HNSCC. A more precise localization of p40 was completed using 6 known markers on 3q and a newly isolated microsatellite marker within the p40 gene. We also determined the genomic organization of the p40 gene using human YAC and BAC clones. Microsatellite analysis revealed that 14 of 26 (54%) primary HNSCC had allelic imbalance in at least 1 of the 7 microsatellite loci. However, FISH analysis with a p40 probe showed that a majority of HNSCC had an increased copy number of the locus regardless of allelic status. Thus, overrepresentation of the p40 locus may play an important role in the development of HNSCC.

AIS is an oncogene amplified in squamous cell carcinoma

We and others recently isolated a human p53 homologue (p40/p51/p63/p73L) and localized the gene to the distal long arm of chromosome 3. Here we sought to examine the role of p40/p73L, two variants lacking the N-terminal transactivation domain, in cancer. Fluorescent in situ hybridization (FISH) analysis revealed frequent amplification of this gene locus in primary squamous cell carcinoma of the lung and head and neck cancer cell lines. (We named this locus AIS for amplified in squamous cell carcinoma.) Furthermore, amplification of the AIS locus was accompanied by RNA and protein overexpression of a variant p68(AIS) lacking the terminal transactivation domain. Protein overexpression in primary lung tumors was limited to squamous cell carcinoma and tumors known to harbor a high frequency of p53 mutations. Overexpression of p40(AIS) in Rat 1a cells led to an increase in soft agar growth and tumor size in mice. Our results support the idea that AIS plays an oncogenic role in human cancer.

Microsatellite instability at selected tetranucleotide repeats is associated with p53 mutations in non-small cell lung cancer

Microsatellite alterations are useful clonal markers for the early detection of cancer. An increase in microsatellite instability has been observed at certain tetranucleotide repeat markers (AAAGn) in lung, head and neck, and bladder cancer. However, the genetic mechanism underlying these elevated microsatellite alterations at selected tetranucleotide repeat (EMAST) tumors is still unknown. The p53 gene plays an important role in maintaining genome integrity by repairing damaged DNA. Therefore, we tested 88 non-small cell lung cancers with a panel of 13 microsatellite markers previously shown to exhibit frequent instability and also performed p53 sequence analysis in these tumors. Thirty-one of these 88 cancers (35%) demonstrated a novel allele [EMAST(+)] in > or =1 of these 13 microsatellite markers. p53 mutations were detected in 50 of 88 (57%) cancers and were significantly (P = 0.001) more common in EMAST(+) tumors (25 of 31; 81%) than in EMAST(-) tumors (25 of 57; 44%). Among squamous cell cancers, p53 mutations were detected significantly (P = 0.04) more frequently in EMAST(+) tumors (17 of 19; 89%) than in EMAST(-) tumors (10 of 18; 55%). Similarly, among primary adenocarcinomas, p53 mutations were present in 67% of the EMAST(+) tumors and in 35% of EMAST(-) adenocarcinomas. None of the 31 EMAST(+) tumors demonstrated high frequency microsatellite instability when examined with a reference panel of five mono- and dinucleotide markers. Primary lung cancers with microsatellite alterations at selected tetranucleotide repeats have a high frequency of p53 mutations and do not display a phenotype consistent with defects in mismatch repair.

An overview on the isolation and analysis of circulating tumor DNA in plasma and serum

Molecular biology has brought about a new dimension to our understanding and analysis of human cancer. Diagnosis and prognosis of cancer have increasingly benefited from the use of molecular markers and molecular approaches. Although the description of circulating tumor DNA in the blood has a long history, the clinical implications of its presence require a large body of well-controlled and stringently performed large research and clinical tests. This chapter has provided an overview of the essential elements for the preparation and analysis of circulating DNA in the plasma or serum. We hope that the basic approaches and tips summarized here will serve as a foundation for the rigorous and comprehensive molecular analysis of circulating nucleic acids in the years to come.

Facile detection of mitochondrial DNA mutations in tumors and bodily fluids

Examination of human bladder, head and neck, and lung primary tumors revealed a high frequency of mitochondrial DNA (mtDNA) mutations. The majority of these somatic mutations were homoplasmic in nature, indicating that the mutant mtDNA became dominant in tumor cells. The mutated mtDNA was readily detectable in paired bodily fluids from each type of cancer and was 19 to 220 times as abundant as mutated nuclear p53 DNA. By virtue of their clonal nature and high copy number, mitochondrial mutations may provide a powerful molecular marker for noninvasive detection of cancer.

Gene promoter hypermethylation in tumors and serum of head and neck cancer patients

Promoter hypermethylation is an important pathway for repression of gene transcription in cancer cells. We analyzed aberrant DNA methylation at four genes in primary tumors from 95 head and neck cancer patients and then used the presence of this methylation as a marker for cancer cell detection in serum DNA. These four genes were tested by methylation-specific PCR and included: p16 (CDKN2A), O6-methylguanine-DNA-methyltransferase, glutathione S-transferase P1, and death-associated protein kinase (DAP-kinase). Fifty-five % (52 of 95) of the primary tumors displayed promoter hypermethylation in at least one of the genes studied: 27% (26/95) at p16, 33% (31 of 95) at O6-methylguanine-DNA-methyltransferase; and 18% (17 of 92) at DAP-kinase. No promoter hypermethylation was observed at the glutathione S-transferase P1 gene promoter. We detected a statistically significant correlation between the presence of DAP-kinase gene promoter hypermethylation and lymph node involvement (P = 0.014) and advanced disease stage (P = 0.016). In 50 patients with paired serum available for epigenetic analysis, the same methylation pattern was detected in the corresponding serum DNA of 21 (42%) cases. Among the patients with methylated serum DNA, 5 developed distant metastasis compared with the occurrence of metastasis in only 1 patient negative for serum promoter hypermethylation (P = 0.056). Promoter hypermethylation of key genes in critical pathways is common in head and neck cancer and represents a promising serum marker for monitoring affected patients.

Inactivation of the INK4A/ARF locus frequently coexists with TP53 mutations in non-small cell lung cancer

Inactivation of the P16 (INK4A)/retinoblastoma (RB) or TP53 biochemical pathway is frequent event in most human cancers. Recent evidence has shown that P14ARF binds to MDM2 leading to an increased availability of wild type TP53 protein. Functional studies also support a putative tumor suppressor gene function for p14ARF suggesting that p14ARF or p53 inactivation may be functionally equivalent in tumorigenesis. To study the relative contribution of each pathway in tumorigenesis, we analysed and compared alterations of the p16, p14ARF and p53 genes in 38 primary non-small cell lung cancers (NSCLCs) (19 adenocarcinomas and 19 squamous carcinoma). The p16 tumor suppressor gene was inactivated in 22 of 38 (58%) tumors. Twelve of these samples (31%) had homozygous deletions by microsatellite analysis; eight of them (21%) had p16 promoter hypermethylation detected by Methylation Specific PCR (MSP) and the remaining two (5%) harbored a point mutation in exon 2 by sequence analysis. The absence of P16 protein in every case was confirmed by immunohistochemistry. Fourteen of the 22 tumors with p16 inactivation also inactivated the p14ARF gene (12 with homozygous deletions extending into INK4a/ARF and two with exon 2 mutations). Mutations of p53 were found in 18 (47%) of the tumors and nine of them (50%) harbored p14ARF inactivation. Thus, an inverse correlation was not found between p14ARF and p53 genetic alterations (P=0.18; Fisher Exact Test). Our data confirm that the p16 gene is frequently inactivated in NSCLC. Assuming that 9p deletion occurs first, the common occurrence of p53 and p14ARF alterations suggests that p14ARF inactivation is not functionally equivalent to abrogation of the TP53 pathway by p53 mutation.

Molecular detection of neoplastic cells in lymph nodes of metastatic colorectal cancer patients predicts recurrence

Disseminated disease, especially to the liver, constitutes the major risk of recurrence for colorectal cancer patients. However, successful resection can still be achieved in 25-35% of colorectal cancer patients with isolated metastases. To evaluate the clinical value of occult micrometastatic disease detection in lymph nodes, we tested genetic (K-ras and p53 gene mutations) and epigenetic (p16 promoter hypermethylation) molecular markers in the perihepatic lymph nodes from colorectal cancer patients with isolated liver metastases. DNA was extracted from 21 paraffin-embedded liver metastases and 80 lymph nodes from 21 colorectal cancer patients. K-ras and p53 gene mutations were identified in DNA from liver metastases by PCR amplification followed by cycle sequencing. A sensitive oligonucleotide-mediated mismatch ligation assay was used to search for the presence of K-ras and p53 mutations to detect occult disease in 68 lymph nodes from tumors positive for these gene mutations. Promoter hypermethylation at the p16 tumor suppressor gene was examined in both liver lesions and lymph nodes by methylation-specific PCR. Sixteen of the 21 (76%) liver metastases harbored either gene point mutations or p16 promoter hypermethylation. Twelve of the 68 lymph nodes were positive for tumor cells by molecular evaluation and negative for tumor cells by histopathology and cytokeratin immunohistochemistry, whereas none were positive for tumor cells by histopathology or negative for tumor cells by molecular analysis (P = 0.0005, McNemar's test). Moreover, in three patients with lymph nodes that were histologically negative at all sites, molecular screening detected tumor DNA at one or more lymph nodes. Survival analysis showed a median survival of 1056 days for patients without evidence of lymph node involvement by molecular analysis and 165 days for patients with positive lymph nodes by this approach (P = 0.0005). These results indicate that lymph node metastasis screening in colorectal cancer patients by molecular-based techniques increases the sensitivity of tumor cell detection and can be a good predictor of recurrence in colorectal cancer patients with resectable liver metastases.

PGP9.5 as a candidate tumor marker for non-small-cell lung cancer

PGP9.5 is a neurospecific peptide that functions to remove ubiquitin from ubiquitinated proteins and prevents them from targeted degradation by proteasomes. Using the serial analysis of gene expression method (SAGE), we observed that the PGP9.5 transcript was highly expressed in primary lung cancers and lung cancer cell lines but was not detectable in the normal lung. Here we examined the expression of PGP9.5 protein in normal lung epithelium, lung tumor cell lines, and 98 resected primary non-small-cell lung carcinomas (NSCLCs). We found PGP9.5 reactivity in normal lung in a pattern compatible with K-cells of the diffuse neuroendocrine system. However, the PGP9.5 was present in both small-cell lung cancer (SCLC) and NSCLC cell lines (22/24) independent of neuronal differentiation. In primary NSCLCs, 54% (53/98) of the cases had positive PGP9.5 staining, and the expression of protein was strongly associated with pathological stage of the cancer. It was present in 44% (29/66) of stage I NSCLCs and in 75% (24/32) of stage II and IIIA NSCLCs (p = 0.0032). These results suggest that the increased expression of PGP9.5 is specifically associated with lung cancer development and may serve as a potential marker for the detection of lung cancer.

A novel nonsense mutation in CACNA1A causes episodic ataxia and hemiplegia

OBJECTIVE

To identify the disease-causing mutation and to characterize penetrance and phenotypic variability in a large pedigree with episodic ataxia type 2 (EA-2) previously linked to chromosome 19.

BACKGROUND

Mutations in the CACNA1A gene on chromosome 19 encoding a calcium channel subunit cause EA-2, which is characterized by recurrent attacks of imbalance with interictal eye movement abnormalities.

METHODS

The authors used single-strand conformation polymorphism (SSCP) analysis to screen for point mutations, and direct sequencing to identify mutations in CACNA1A. Allele-specific oligonucleotides were designed to detect the presence of the diseased allele in members of their pedigree as well as in normal control subjects.

RESULTS

Reassessment of members of the pedigree revealed two notable clinical features. Diffuse weakness during attacks of ataxia was a prominent complaint. Two affected individuals had had episodic hemiplegia, one with typical migraine headaches. SSCP analysis revealed aberrant bands in exon 29 in affected members but not in normal control subjects. Direct sequencing of exon 29 identified a C-to-T change at position 4914 of the coding sequence of CACNA1A, predicting an early stop code at codon 1547. Two asymptomatic mutation carriers demonstrated the incomplete penetrance of this mutation.

CONCLUSIONS

A nonsense mutation in CACNA1A causes episodic ataxia and complaint of weakness, and may be associated with hemiplegia.

Rapid p53 sequence analysis in primary lung cancer using an oligonucleotide probe array

The p53 gene was sequenced in 100 primary human lung cancers by using direct dideoxynucleotide cycle sequencing and compared with sequence analysis by using the p53 GeneChip assay. Differences in sequence analysis between the two techniques were further evaluated to determine the accuracy and limitations of each method. p53 mutations were either detected by using both techniques or, if only detected by one technique, were confirmed by using mutation-specific oligonucleotide hybridization. Dideoxynucleotide sequencing of the conserved regions of the p53 gene (exons 5-9) detected 76% of the mutations within this region of the gene. The GeneChip p53 assay detected 81% of all (exons 2-11) mutations, including 80% of the mutations within the conserved regions of the gene. The GeneChip assay detected 46 of 52 missense mutations (88%), but 0 of 5 frameshift mutations. The specificity of direct sequencing and of the p53 GeneChip assay at detecting p53 mutations were 100% and 98%, respectively. The GeneChip p53 assay is a rapid and reasonably accurate approach for detecting p53 mutations; however, neither direct sequencing nor the p53 GeneChip are infallible at p53 mutation detection.

Cyclin D1 amplification is independent of p16 inactivation in head and neck squamous cell carcinoma

Progression through the G1 phase of the cell cycle is mediated by phosphorylation of the retinoblastoma protein (pRb) resulting in the release of essential transcription factors such as E2F-1. The phosphorylation of pRb is regulated positively by cyclin D1/CDK4 and negatively by CDK inhibitors, such as p16 (CDKN2/MTS-1/INK4A). The p16/cyclin D1/Rb pathway plays a critical role in tumorigenesis and many tumor types display a high frequency of inactivation of at least one component of this pathway. In order to determine the overall contribution of these three components to progression of head and neck squamous cell carcinoma (HNSCC), we examined p16 inactivation, cyclin D1 amplification, and pRb expression in 23 primary HNSCC tumors and five cell lines. p16 inactivation was detected in 19/23 (83%) primary tumors by detailed genetic analysis and was confirmed by immunohistochemistry (IHC). Absence of Rb protein expression indicative of pRb inactivation was identified in 2/23 (9%) tumors. In this set of tumors, there was a perfect inverse correlation between p16 and pRb inactivation. Using fluorescence in situ hybridization (FISH) cyclin D1 amplification was identified in 4/5 (80%) cell lines and 4/11 (36%) primary tumors. However, 2/4 cell lines and all four primary tumors with cyclin D1 amplification contained a concomitant alteration of p16. Therefore 21/ 23 (91%) of primary HNSCC contained at least one alteration in the p16/cyclin D1/Rb pathway. Although p16 and Rb alteration are apparently exclusive, cyclin D1 amplification occurs concomitantly with the loss of p16 suggesting an additional role for this amplification in HNSCC.

Calcium channelopathies in the central nervous system

The recent discovery that familial hemiplegic migraine, episodic ataxia type 2, and spinocerebellar ataxia type 6 are allelic disorders caused by different mutations in CACNA1A, a calcium-channel-encoding gene, adds to a growing list of channelopathies causing paroxysmal neurologic disturbance and progressive neurodegeneration. Calcium channelopathies in the central nervous system provide a model to study the important roles that calcium channels play in neuronal function.

Mutation analysis of hBUB1 in aneuploid HNSCC and lung cancer cell lines

Aneuploidy is frequently observed in many types of human cancer cells, suggesting that mutations of genes required for chromosomal stability may occur in human tumors. The BUB gene is a component of the mitotic checkpoint in budding yeast that delays anaphase in the presence of spindle damage thus increasing the probability of successful delivery of a euploid genome to each daughter cell. Recently, human homologues of the BUB gene were identified and mutant alleles of hBUB1 were detected in two colorectal tumor cell lines. Transfection of one mutant allele led to dominant disruption of the mitotic checkpoint control in a euploid cell, suggesting that aneuploidy in some tumors could be due to defects in the mitotic checkpoint. We analyzed the entire coding sequence of hBUB1 for mutation in 31 head and neck squamous cell carcinoma (HNSCC) and lung cancer cell lines, most with severe aneuploidy. We found expression of the hBUB1 gene in all cell lines and only a single nucleotide substitution in one cell line without a resultant change in amino acid sequence. Our study demonstrates that hBUB1 is rarely a target for genetic alterations in tumors of the respiratory tract.

Molecular detection of tumor cells in bronchoalveolar lavage fluid from patients with early stage lung cancer

BACKGROUND

Conventional cytologic analysis of sputum is an insensitive test for the diagnosis of non-small-cell lung cancer (NSCLC). We have recently demonstrated that polymerase chain reaction (PCR)-based molecular methods are more sensitive than cytologic analysis in diagnosing bladder cancer. In this study, we examined whether molecular assays could identify cancer cells in bronchoalveolar lavage (BAL) fluid.

METHODS

Tumor-specific oncogene mutations, CpG-island methylation status, and microsatellite alterations in the DNA of cells in BAL fluid from 50 consecutive patients with resectable (stages I through IIIa) NSCLC were assessed by use of four PCR-based techniques.

RESULTS

Of 50 tumors, 28 contained a p53 mutation, and the identical mutation was detected with a plaque hybridization assay in the BAL fluid of 39% (11 of 28) of the corresponding patients. Eight of 19 adenocarcinomas contained a K-ras mutation, and the identical mutation was detected with a mutation ligation assay in the BAL fluid of 50% (four of eight) of the corresponding patients. The p16 gene was methylated in 19 of 50 tumors, and methylated p16 alleles were detected in the BAL fluid of 63% (12 of 19) of the corresponding patients. Microsatellite instability in at least one marker was detected with a panel of 15 markers frequently altered in NSCLC in 23 of 50 tumors; the identical alteration was detected in the BAL fluid of 14% (three of 22) of the corresponding patients. When all four techniques were used, mutations or microsatellite instability was detected in the paired BAL fluid of 23 (53%) of the 43 patients with tumors carrying a genetic alteration.

CONCLUSION

Although still limited by sensitivity, molecular diagnostic strategies can detect the presence of neoplastic cells in the proximal airway of patients with surgically resectable NSCLC.

Serial analysis of gene expression in non-small cell lung cancer

We used the serial analysis of gene expression (SAGE) method to systematically analyze transcripts present in non-small cell lung cancer. Over 226,000 SAGE tags were sequence analyzed from two independent primary lung cancers and two normal human bronchial/tracheal epithelial cell cultures. A total of 226,000 SAGE tags were sequence identified, representing 43,254 unique transcripts. Comparison of the tags present in the tumor with those identified in the normal tissue revealed 175 transcript tags that were overrepresented in the normal tissue and 142 tags that were overexpressed in the tumor by 10-fold or more. Northern hybridization was performed on 15 of the most abundantly expressed tags identified in the tumors. These tags were derived from either a known gene or a matched expressed sequence tag clone. The transcripts for 3 of the 15 genes, PGP 9.5, B-myb, and human mutT, were abundantly expressed in primary lung cancers (10 of 18, 15 of 18, and 6 of 12 tumors, respectively). In contrast, the presence of PGP9.5 and B-myb was much less frequent in primary tumors derived from other tissue origins. These results suggest that at least a portion of the transcripts identified by SAGE are frequently associated with lung cancer, and that their overexpression may contribute to lung tumorigenesis. The identification and further characterization of genes generated by SAGE should provide potential new targets for the diagnosis, prognosis, and therapy of lung cancer.

Somatic mutations of the PTEN tumor suppressor gene in sporadic follicular thyroid tumors

The PTEN (MMAC1/TEP1) tumor suppressor gene was recently isolated and mapped to human chromosome band 10q23. Homozygous deletions and mutations of PTEN were observed in cell lines and sporadic cancers of the breast, kidney, and central nervous system. Germline mutations in PTEN were recently found in Cowden disease, an autosomal dominant inherited syndrome, previously mapped to chromosome bands 10q22-23. This disease is associated with a wide variety of malignancies and hamartomas of ectodermal, mesodermal, and endodermal origin. The most common neoplasms in Cowden disease patients arise in the breast, skin, and thyroid (follicular subtype). To determine the involvement of PTEN in sporadic follicular thyroid tumors, we first analyzed sporadic follicular adenomas and carcinomas for deletions of the PTEN gene. Loss of heterozygosity was found in 7/26 (27%) follicular carcinomas and 2/27 (7%) follicular adenomas, one of which was a small hemizygous deletion (approximately 3 cm). Sequence analysis of the entire PTEN coding region revealed two mutations in carcinomas with 10q loss. Our findings suggest that the PTEN tumor suppressor gene is occasionally inactivated in sporadic follicular thyroid tumors.