Induction of programmed cell death in Kaposi's sarcoma cells by preparations of human chorionic gonadotropin

Extensive genomic deletions involving chromosome 10 are the most common genetic alteration in glioblastoma multiforme (GBM). To localize and examine the potential roles of two chromosome arm 10q tumor suppressor regions, we used two independent strategies: mapping of allelic deletions, and functional analysis of phenotypic suppression after transfer of chromosome 10 fragments. By allelic deletion analysis, the region of 10q surrounding the MMAC/PTEN locus was shown to be frequently lost in GBMs but maintained in most low-grade astrocytic tumors. An additional region at 10q25 containing the DMBT1 locus was lost in all grades of gliomas examined. The potential biological significance of these two regions was further assessed by examining microcell hybrids that contained various fragments of 10q. Somatic cell hybrid clones that retained the MMAC/PTEN locus have a less transformed phenotype with clones exhibiting an inability to grow in soft agarose. However, presence or absence of DMBT1 did not correlate with any in vitro phenotype assessed in our model system. These results support a model of molecular progression in gliomas in which the frequent deletion of 10q25-26 is an early event and is followed by the deletion of the MMAC/PTEN during the progression to high-grade GBMs.     

PTEN mutations in gliomas and glioneuronal tumors

Cytogenetic and loss of heterozygosity studies have suggested the presence of at least one tumor suppressor gene on chromosome 10 involved in the formation of high grade gliomas. Recently, the PTEN gene, also termed MMAC1 or TEP1, on chromosomal band 10q23 has been identified. Initial studies revealed mutations of PTEN in limited series of glioma cell lines and glioblastomas. In order to systematically evaluate the involvement of PTEN in gliomas, we have analysed the entire PTEN coding sequence by SSCP and direct sequencing in a series of 331 gliomas and glioneuronal tumors. PTEN mutations were detected in 20/142 glioblastomas, 1/7 giant cell glioblastomas, 1/2 gliosarcomas, 1/30 pilocytic astrocytomas and 2/22 oligodendrogliomas. No PTEN mutations were detected in 52 astrocytomas, 37 oligoastrocytomas, three subependymal giant cell astrocytomas, four pleomorphic xanthoastrocytomas, 15 ependymomas, 16 gangliogliomas and one dysembryoplastic neuroepithelial tumor. In addition, all tumors were examined for the presence of homozygous deletions of the PTEN gene; these were detected in 7 glioblastomas that did not have PTEN mutations. Therefore, PTEN mutations occur in approximately 20% of glioblastomas but are rare in lower grade gliomas. These findings confirm that PTEN is one of the chromosome 10 tumor suppressor genes involved in the development of glioblastomas.     

Allelic deletion analyses of MMAC/PTEN and DMBT1 loci in gliomas: relationship to prognostic significance

The frequency of loss of heterozygosity (LOH) around MMAC/PTEN and DMBT1 loci and survival analyses based on the LOH status were assessed in 110 patients with different histological groups of gliomas. Twenty-six of the patients had anaplastic oligodendrogliomas, 31 had anaplastic astrocytomas, and 53 had glioblastomas multiforme (GM). At the DMBT1 locus, LOH was observed very frequently in all three histological groups, with no significant difference in the frequency of LOH among the three histological groups. At the MMAC/PTEN locus, patients with GM exhibited a significantly increased frequency of LOH (72%) compared with patients with anaplastic astrocytomas (29%) or anaplastic oligodendrogliomas (31%) (P < 0.0001). Kaplan-Meier survival plots showed that patients with LOH at the MMAC/PTEN locus had a significantly worse prognosis than did patients without LOH at the MMAC/PTEN locus [hazard ratio (LOH versus non-LOH), 2.65; 95% confidence interval (CI), 1.69-4.46; P < 0.0001]. Cox proportional hazards regression analysis, adjusted for age at surgery and histological grades (GM and non-GM), showed that LOH at the MMAC/PTEN locus was a significant predictor of shorter survival [hazard ratio (LOH versus non-LOH), 2.01; 95% CI, 1.1-3.5; P = 0.018). Our analysis failed to indicate a similar association between the frequency of LOH at the DMBT1 locus and patient survival [hazard ratio (LOH versus non-LOH), 2; 95% CI, 0.37-3.13; P = 0.2]. These results suggest that the DMBT1 gene may be involved early in the oncogenesis of gliomas, whereas alterations in the MMAC/PTEN gene may be a late event in the oncogenesis related to progression of gliomas and provide a significant prognostic marker for patient survival.     

Point mutation and homozygous deletion of PTEN/MMAC1 in primary bladder cancers

A new tumor suppressor gene PTEN/MMAC1 was recently isolated at chromosome 10q23 and found to be inactivated by point mutation or homozygous deletion in glioma, prostate and breast cancer. PTEN/MMAC1 was also identified as the gene predisposing to Cowden disease, an autosomal dominant cancer predisposition syndrome associated with an increased risk of breast, skin and thyroid tumors and occasional cases of other cancers including bladder and renal cell carcinoma. We screened 345 urinary tract cancers by microsatellite analysis and found chromosome 10q to be deleted in 65 of 285 (23%) bladder and 15 of 60 (25%) renal cell cancers. We then screened the entire PTEN/MMAC1 coding region for mutation in 25 bladder and 15 renal cell primary tumors with deletion of chromosome 10q. Two somatic point mutations, a frameshift and a splicing variant, were found in the panel of bladder tumors while no mutation was observed in the renal cell carcinomas. To screen for homozygous deletion, we isolated two polymorphic microsatellite repeats from genomic BAC clones containing the PTEN/MMAC1 gene. Using these new informative markers, we identified apparent retention at the gene locus indicative of homozygous deletion of PTEN/MMAC1 in four of 65 bladder and 0 of 15 renal cell tumors with LOH through chromosome 10q. Identification of the second inactivation event in six bladder tumors with LOH of 10q implies that the PTEN/MMAC1 gene is occasionally involved in bladder tumorigenesis. However, the low frequency of biallelic inactivation suggests that either PTEN/MMAC1 is inactivated by other mechanisms or it is not the only target of chromosome 10q deletion in primary bladder and renal cell cancer.     

Loss of heterozygosity and mutational analysis of the PTEN/MMAC1 gene in synchronous endometrial and ovarian carcinomas

Mutations of the human putative protein tyrosine phosphatase (PTEN/MMAC1) gene at chromosome 10q23 have been found frequently in type I endometrial carcinomas. Endometrioid adenocarcinoma is the most frequent histology seen in patients with clinically determined synchronous endometrial and ovarian carcinomas. We report a high incidence of PTEN/MMAC1 mutations and 10q23 loss of heterozygosity (LOH) in patients with synchronous endometrial and ovarian carcinomas. Paraffin-embedded precision microdissected tumors were analyzed for 10 matched synchronous endometrial and ovarian cancers and 11 matched control metastatic endometrial cancers. Single-stranded conformation polymorphism analysis was used to screen for mutations in all tumors and corresponding normal lymphocyte DNA. LOH was determined using a panel of four microsatellite markers within the PTEN/MMAC1 locus. PTEN/MMAC1 mutations were found in 43% (9 of 21) of the endometrial cancers studied, similarly represented in the clinically synchronous group (5 of 10 or 50%) and the advanced metastatic group (4 of 11; 36%; P = 0.53). In two of the five cases of clinically synchronous cancers, identical or progressive PTEN mutations were found in both the endometrial and ovarian cancers, suggesting that the ovarian tumor is a metastasis from the endometrial primary. PTEN/MMAC1 mutations in the advanced endometrial cancers were similar in the corresponding metastases. In one case, the mutation was seen in only one of two metastatic lymph nodes. The LOH analysis demonstrated 55% LOH in at least one PTEN/MMAC1 marker. These findings suggest that the putative tumor suppressor gene PTEN/MMAC1 may be a viable molecular marker to differentiate synchronous versus metastatic disease in a subset of clinically synchronous endometrial and ovarian carcinomas.     

Somatic mutations of the PTEN/MMAC1 gene in fifteen Japanese endometrial cancers: evidence for inactivation of both alleles

Loss of heterozygosity (LOH) of chromosome 10q is observed in approximately 40% of endometrial cancers. Mutations in PTEN/MMAC1, a gene recently isolated from the 10q23 region, are responsible for two dominantly inherited neoplastic syndromes, Cowden disease and Bannayan-Zonana syndrome. Somatic mutations of this gene have also been detected in sporadic cancers of the brain, prostate and breast. To investigate the potential role of this putative tumor suppressor gene in endometrial carcinogenesis as well, we examined 46 primary endometrial cancers for LOH at the 10q23 region, and for mutations in the entire coding region and exon-intron boundaries of the PTEN/MMAC1 gene. LOH was identified in half of the 38 informative cases, and subtle somatic mutations were detected in 15 tumors (33%). Our results suggest that of the genes studied so far in endometrial carcinomas, PTEN/MMAC1 is the most commonly mutated one, and that inactivation of both copies by allelic loss and/or mutation, a pattern that defines genes as "tumor suppressors," contributes to tumorigenesis in endometrial cancers.     

Identification of PTEN/MMAC1 alterations in uncultured melanomas and melanoma cell lines

A novel tumor suppressor gene, PTEN/MMAC1, has been recently shown to be mutated in gliomas, breast, prostate, kidney cancers and melanomas. Loss-of-heterozygosity studies in melanoma have suggested the presence of at least one chromosome 10q locus lost early in tumor progression. In this study, we screened 45 melanoma cell lines and 17 paired uncultured metastatic melanoma and peripheral blood specimens for PTEN/ MMAC1 alterations using PCR-SSCP and direct sequencing. We found nine melanoma cell lines with homozygous deletions (five with intragenic loss) and four cell lines with mutations (one nonsense and one frameshift; two intronic); from among our uncultured melanoma specimens, we found one tumor with a somatic 17 bp duplication in exon 7 leading to a premature stop codon and one tumor with a possible homozygous deletion. Furthermore, we have identified a novel intragenic polymorphism within intron 4 of PTEN/MMAC1. Taken together, these data suggest that PTEN/MMAC1 may be a chromosome 10q tumor suppressor important in melanoma tumor formation or progression.     

Mutation analysis of the PTEN/MMAC1 gene in lung cancer

We studied PTEN/MMAC1, a newly discovered candidate tumor suppressor gene at 10q23.3, for mutations in lung cancer. One hundred and thirty-six lung cancer cell line DNAs (66 small cell lung cancers, SCLC, 61 non-small cell lung cancers, NSCLC, four mesotheliomas, five extrapulmonary small cell cancers) were analysed for PTEN/MMAC1 homozygous deletions and five (8%) SCLC lines showed homozygous deletions interrupting the PTEN/MMAC1 gene. Using single stranded conformation polymorphism (SSCP) analysis, we screened the PTEN/MMAC1 open reading frame of 53 lung cancer cell line cDNAs for point mutations and found that 3/35 SCLCs and 3/18 NSCLCs contained homozygous amino acid sequence altering mutations. Northern blot analysis revealed that expression of the PTEN/MMAC1 gene was considerably lower in all the tumor cell lines with point mutations while no expression was detected for cell lines with PTEN/MMAC1 homozygous deletions. Mutation analysis of 22 uncultured, microdissected, primary SCLC tumors and metastases showed two silent mutations, and two apparent homozygous deletions. We also discovered a processed pseudogene (PTEN2) which has 98.5% nt identity to PTEN/MMAC1, that needs to be accounted for in cDNA mutation analysis. Our findings suggest that genetic abnormalities of the PTEN/MMAC1 gene are only involved in a relatively small subset of lung cancers.     

Analysis of PTEN and the 10q23 region in primary prostate carcinomas

Deletions involving chromosome 10q23 occur frequently in prostatic carcinomas. Recently, a novel tumour suppressor gene, PTEN, mapping to this interval, has been identified. Mutation or deletion of PTEN has been observed in a proportion of prostate cancer cell lines; however, primary prostate carcinomas have not been studied. We have investigated the involvement of PTEN in primary prostatic adenocarcinomas using a panel of 51 matched normal and prostate tumour DNAs. We first determined the proportion of tumours with allele loss at loci in 10q23 which span the region containing the PTEN gene. Our results show that LOH involving 10q23 is common in primary prostate carcinomas. Twenty-five of 51 (49%) tumours showed loss of heterozygosity (LOH) over the region spanning the PTEN locus. We next directly analysed the PTEN gene for mutations of the coding region using single strand conformation polymorphism (SSCP) and sequence analyses. Of those tumours with LOH, only a single tumour was found to carry a missense mutation in PTEN. No mutations in PTEN were identified in tumours without LOH. Our results suggest either that mutation of PTEN is a late event in prostate tumorigenesis, or that another tumour suppressor gene important in prostate cancer may lie close to PTEN in 10q23.     

PTEN (MMAC1) mutations are frequent in primary glioblastomas (de novo) but not in secondary glioblastomas

Loss of heterozygosity (LOH) on chromosome 10 is the most frequent genetic alteration associated with the evolution of malignant astrocytic tumors and it may involve several loci. The tumor suppressor gene PTEN (MMAC1) on chromosome 10q23 is mutated in approximately 30% of glioblastomas (WHO Grade IV). In this study, we assessed the frequency of PTEN mutations in primary glioblastomas, which developed clinically de novo, and in secondary glioblastomas, which evolved from low-grade (WHO Grade II) or anaplastic astrocytomas (WHO Grade III). Nine of 28 (32%) primary glioblastomas contained a PTEN mutation and an additional case showed a homozygous PTEN deletion. This indicates that after overexpression/amplification of the EGF receptor, loss of PTEN function is the most common alteration in primary glioblastomas. In this series, 5 of 28 (18%) primary glioblastomas showed both a PTEN mutation and EGFR amplification. In contrast, only 1 of 25 (4%) secondary glioblastomas contained a PTEN mutation, and none of them showed a homozygous PTEN deletion. The secondary glioblastoma with a PTEN mutation developed from an anaplastic astrocytoma that already carried the mutation. The observation that secondary glioblastomas have a p53 mutation as a genetic hallmark but rarely contain a PTEN mutation supports the concept that primary and secondary glioblastomas develop differently on a genetic level.     

Somatic deletions and mutations in the Cowden disease gene, PTEN, in sporadic thyroid tumors

The majority of familial medullary thyroid neoplasms are associated with germ-line mutations of the RET proto-oncogene, yet very little is known about the mechanisms involved in the pathogenesis of familial and sporadic nonmedullary thyroid tumors. A subset of thyroid tumors have loss of heterozygosity of chromosome 10q22-23, a region harboring the gene responsible for Cowden disease, an autosomal dominant hamartoma syndrome associated with thyroid and breast tumors. PTEN/MMAC1/TEP1 codes for a dual-specificity phosphatase and is likely a tumor suppressor gene. We sought to determine the PTEN status in a series of epithelial thyroid neoplasms. We studied 95 sporadic thyroid tumors, of which 39 were papillary thyroid carcinomas (PTCs), 12 were follicular carcinomas, 9 were anaplastic carcinomas, 5 were Hürthle cell carcinomas, 21 were nonfunctioning follicular adenomas, and 9 were Hürthle cell adenomas. Direct sequencing of PCR-amplified products was performed for all nine exons of PTEN. Two polymorphic markers, one located in intron 8 and another, a dinucleotide repeat marker, AFMa086wg9, located within intron 2, were analyzed in paired blood-tumor DNA samples to assess hemizygous deletions of PTEN. We found a somatic frameshift mutation in one PTC, which was expected to generate a premature stop codon 2 amino acids downstream. Twenty-six % of informative benign tumors (four follicular adenomas and three Hürthle cell adenomas) and only 3 of 49 (6.1%) informative malignant tumors (one PTC, one follicular carcinoma, and one anaplastic carcinoma) showed evidence of hemizygous deletion of PTEN (P = 0.046). We conclude that a subset of thyroid tumors have somatic deletions of the PTEN gene, predominantly the benign forms, and that small intragenic mutations of PTEN are infrequent in thyroid tumors. We speculate that other mechanisms of PTEN inactivation, rather than small intragenic mutations, might occur in the hemizygously deleted samples and act as the "Knudson second hit." Alternatively, other tumor suppressor genes mapping to chromosome 10q22-23 could be the actual targets for such deletions and thus represent the various hits in the pathway of multistep carcinogenesis.     

Disruption of the MMAC1/PTEN gene by deletion or mutation is a frequent event in malignant melanoma

The MMAC1/PTEN gene, located at 10q23.3, is a candidate tumor suppressor commonly mutated in glioma. We have studied the pattern of deletion, mutation, and expression of MMAC1/PTEN in 35 unrelated melanoma cell lines. Nine (26%) of the cell lines showed partial or complete homozygous deletion of the MMAC1/PTEN gene, and another six (17%) harbored a mutation in combination with loss of the second allele. Mutations could also be demonstrated in uncultured tumor specimens from which the cell lines had been established, and cell lines derived from two different metastases from one individual carried the same missense mutation. Collectively, these findings suggest that disruption of MMAC1/PTEN by allelic loss or mutation may contribute to the pathogenesis or neoplastic evolution in a large proportion of malignant melanomas.     

Frequent inactivation of PTEN in prostate cancer cell lines and xenografts

Loss of chromosome 10q is a frequently observed genetic defect in prostate cancer. Recently, the PTEN/MMAC1 tumor suppressor gene was identified and mapped to chromosome 10q23.3. We studied PTEN structure and expression in 4 in vitro cell lines and 11 in vivo xenografts derived from six primary and nine metastatic human prostate cancers. DNA samples were allelotyped for eight polymorphic markers within and surrounding the PTEN gene. Additionally, the nine PTEN exons were tested for deletions. In five samples (PC3, PC133, PCEW, PC295, and PC324), homozygous deletions of the PTEN gene or parts of the gene were detected. PC295 contained a small homozygous deletion encompassing PTEN exon 5. In two DNAs (PC82 and PC346), nonsense mutations were found, and in two (LNCaP and PC374), frame-shift mutations were found. Missense mutations were not detected. PTEN mRNA expression was clearly observed in all cell lines and xenografts without large homozygous deletions, showing that PTEN down-regulation is not an important mechanism of PTEN inactivation. The high frequency (60%) of PTEN mutations and deletions indicates a significant role of this tumor suppressor gene in the pathogenesis of prostate cancer.     

PTEN/MMAC1 mutations in endometrial cancers

Endometrial carcinomas represent the most common gynecological cancer in the United States, yet the molecular genetic events that underlie the development of these tumors remain obscure. Chromosome 10 is implicated in the pathogenesis of endometrial carcinoma based on loss of heterozygosity (LOH), comparative genomic hybridization, and cytogenetics. Recently, a potential tumor suppressor gene, PTEN/MMAC1, with homology to dual-specificity phosphatases and to the cytoskeletal proteins tensin and auxillin was identified on chromosome 10. This gene is mutated in several types of advanced tumors that display frequent LOH on chromosome 10, most notably glioblastomas. Additionally, germ-line mutations of PTEN/MMAC1 are responsible for several familial neoplastic disorders, including Cowden disease and Bannayan-Zonana syndrome. Because this locus is included in the region of LOH in many endometrial carcinomas, we examined 70 endometrial carcinomas for alterations in PTEN/MMAC1. Somatic mutations were detected in 24 cases (34%) including 21 cases that resulted in premature truncation of the protein, 2 tumors with missense alterations in the conserved phosphatase domain, and 1 tumor with a large insertion. These data indicate that PTEN/MMAC1 is more commonly mutated than any other known gene in endometrial cancers.     

Mutual influence of plasmid profile and growth temperature on the lipid composition of Yersinia pseudotuberculosis bacteria

Glioblastoma multiforme (GBM) is the most malignant glial brain tumor in humans. The fact that deleted copies of chromosome 10 are observed frequently in primary GBM tumors supports the hypothesis that one or more tumor suppressor genes located on chromosome 10 occupy crucial growth control checkpoints for glial cells. Deletion mapping in primary GBM tumors using the loss of heterozygosity (LOH) test has implicated the 10q24-10qter region as one possible site for a gene. We report here on the molecular cytogenetic analysis of chromosome 10 abnormalities in a human GBM cell line, JBSA. LOH testing showed that JBSA cells were hemizygous for chromosome 10. Molecular cytogenetic analysis showed that the undeleted homologue was involved in a reciprocal translocation t(7;10)(p21;q22). The translocation breakpoint on chromosome 10 lay within band q22 between D10S19 and D10S4. The fact that JBSA cells lack one homologue of chromosome 10 and carry a translocation breakpoint on the remaining one, proximal to the smallest region of overlap reported in primary tumor deletions, suggests that 10q22 may be another possible site for a tumor suppressor gene involved in GBM.     

Mutation and expression analysis of the putative prostate tumour-suppressor gene PTEN

The chromosomal region 10q23-24 is frequently deleted in a number of tumour types, including prostate adenocarcinoma and glioma. A candidate tumour-suppressor gene at 10q23.3, designated PTENor MMAC1, with putative actin-binding and tyrosine phosphatase domains has recently been described. Mutations in PTEN have been identified in cell lines derived from gliomas, melanomas and prostate tumours and from a number of tumour specimens derived from glial, breast, endometrial and kidney tissue. Germline mutations in PTEN appear to be responsible for Cowden disease. We identified five PTEN mutations in 37 primary prostatic tumours analysed and found that 70% of tumours showed loss or alteration of at least one PTEN allele, supporting the evidence for PTEN involvement in prostate tumour progression. We raised antisera to a peptide from PTEN and showed that reactivity occurs in numerous small cytoplasmic organelles and that the protein is commonly expressed in a variety of cell types. Northern blot analysis revealed multiple RNA species; some arise as a result of alternative polyadenylation sites, but others may be due to alternative splicing.     

Simplified guide for precise implant placement: a technical note

Loss of heterozygosity (LOH) at chromosome band 10q23 occurs frequently in a wide variety of human tumors. A recently identified candidate tumor suppressor gene, PTEN located on 10q23, is mutated in multiple advanced cancers. To explore whether PTEN is associated with human squamous cell carcinoma of the head and neck (SCCHN), DNAs from both normal muscle and tumor tissue in 19 SCCHN were used for detecting LOH at chromosome 10q23 and mutational analysis of PTEN by direct polymerase chain reaction (PCR)-DNA sequencing. LOH at 10q23 was identified in 6/15 SCCHN. Mutation of PTEN was identified in 3/19 SCCHN. Of these 3 patients, 2 had stage IV disease; the third patient, with recurrent, metastatic and stage III disease, showed a 36 bp germline heterozygous deletion within intron 7. Furthermore, a missense mutation at codon 501 (TCT --> TTT: Ser --> Phe) in exon 8 was also found in tumor from the same patient. Our results suggest that PTEN may play a role in the genesis of some SCCHNs.     

A novel gene, LGI1, from 10q24 is rearranged and downregulated in malignant brain tumors

Loss of heterozygosity for 10q23-26 is seen in over 80% of glioblastoma multiforme tumors. We have used a positional cloning strategy to isolate a novel gene, LGI1 (Leucine-rich gene-Glioma Inactivated), which is rearranged as a result of the t(10;19)(q24;q13) balanced translocation in the T98G glioblastoma cell line lacking any normal chromosome 10. Rearrangement of the LGI1 gene was also detected in the A172 glioblastoma cell line and several glioblastoma tumors. These rearrangements lead to a complete absence of LGI1 expression in glioblastoma cells. The LGI1 gene encodes a protein with a calculated molecular mass of 60 kD and contains 3.5 leucine-rich repeats (LRR) with conserved flanking sequences. In the LRR domain, LGI1 has the highest homology with a number of transmembrane and extracellular proteins which function as receptors and adhesion proteins. LGI1 is predominantly expressed in neural tissues, especially in brain; its expression is reduced in low grade brain tumors and it is significantly reduced or absent in malignant gliomas. Its localization to the 10q24 region, and rearrangements or inactivation in malignant brain tumors, suggest that LGI1 is a candidate tumor suppressor gene involved in progression of glial tumors.