Loss of heterozygosity in cervical carcinoma: subchromosomal localization of a putative tumor-suppressor gene to chromosome 11q22-q24

Identification of VWA5A as a novel biomarker for inhibiting metastasis in breast cancer by machine-learning based protein prioritization

Distant metastasis is the leading cause of death in breast cancer (BC). The timing of distant metastasis differs according to subtypes of BCs and there is a need for identification of biomarkers for the prediction of early and late metastasis. To identify biomarker candidates whose abundance level can discriminate metastasis types, we performed a high-throughput proteomics assay using tissue samples from BCs with no metastasis, late metastasis, and early metastasis, processed data with machine learning-based feature selection, and found that low VWA5A could be responsible for shorter duration of metastasis-free interval. Low expression of VWA5A gene in METABRIC cohort was associated with poor survival in BCs, especially in hormone receptor (HR)-positive BCs. In-vitro experiments confirmed tumor suppressive effect of VWA5A on BCs in HR+ and triple-negative BC cell lines. We found that expression of VWA5A can be assessed by immunohistochemistry (IHC) on archival tissue samples. Decreasing nuclear expression of VWA5A was significantly associated with advanced T stage and lymphatic invasion in consecutive BCs of all subtypes. We discovered lower expression of VWA5A as the potential biomarker for metastasis-prone BCs, and our results support the clinical utility of VWA5A IHC, as an adjunctive tools for prognostication of BCs.

Characterization of genomic changes in the cervical pre-cancerous lesions and tumors induced by different types of human papillomaviruses

Cervical carcinoma is the second most common malignancy among women in both incidence and mortality. Although much is known about the etiology and treatment of cervical cancer, the role of genetic alterations in the multistep pathway of cervical tumorigenesis is largely unknown. The aim of this study was to characterize the genomic changes in the cervical pre-cancerous lesions and tumors, induced by different types of human papillomaviruses. In this research was used the BlueGnome CytoChip oligo 2 × 105 K microarray for whole-genome oligo-array CGH. Microarray CGH analysis of 40 specimens was carried out-12 specimens from patients with early-stage squamous cell carcinomas; 19 specimens from patients with mild to moderate dysplasia and 9 with severe dysplasia. First we performed microarray CGH analysis of five DNA pools which contained the DNA from homogeneous groups of patients. The results revealed presence of micro chromosomal aberrations in chromosome region 14q11.2. According to the genome database these aberrations represent polymorphisms. Microarray analysis of DNA from 9 separate carcinoma lesions revealed a total of 26 aberrations in 14 chromosomes of nine patients. Our results showed the advantages of high-resolution chips in the clinical diagnosis of patients with cancerous and precancerous lesions caused by viral infection with HPV, but also highlight the need for extensive population studies revealing the molecular nature and clinical significance of different CNVs and the creation of detailed maps of variations in the Bulgarian population. This would facilitate extremely precise interpretation of specific genomic imbalances in the clinical aspect.

Expression of Serine Protease Matriptase in Renal Cell Carcinoma: Correlation of Tissue Microarray Immunohistochemical Expression Analysis Results with Clinicopathological Parameters

Serine protease matriptase (matriptase) cleaves and activates proteins implicated in the progression of cancer and represents a potential therapeutic target. Immunohistochemical analysis of matriptase was performed in tissue microarrays of 168 renal cell carcinomas (RCCs). All subtypes of RCC showed significant immunohistochemical expression of matriptase. In contrast, no expression occurred in areas of RCC with sarcomatous differentiation (SRCC) and in normal collecting tubules. The matriptase scores were significantly higher in papillary RCC (341) and clear cell RCC with granular cell differentiation (GRCC; 324) than in other histologic subtypes of RCC. In GRCC, matriptase scores were correlated with TNM staging and nuclear grading. Matriptase was overexpressed in all subtypes of RCC, and matriptase scores could distinguish between conventional clear cell RCC, GRCC, and SRCC.

Alterations of ATM and CADM1 in chromosomal 11q22.3-23.2 region are associated with the development of invasive cervical carcinoma

To understand the importance of chr11q22.3-23.2 region in the development of cervical cancer, we have studied the genetic and epigenetic alterations of the candidate genes ATM, PPP2R1B, SDHD and CADM1 in cervical intraepithelial neoplasia (CIN) and cervical carcinoma (CACX) samples. Our study revealed low expression and high alterations (methylation/deletion) (55-59%) of ATM and CADM1 genes along with poor patient outcome. The alterations of ATM and CADM1 are associated with the progression of tumor from CIN to Stage I/II, thus implying their role in early invasiveness. The two genes, PPP2R1B and SDHD, lying in between ATM and CADM1, have low frequency of alterations, and majority of the alterations are in CACX samples, indicating that their alterations might be associated with disease progression. Expressions (mRNA/protein) of the genes showed concordance with their molecular alterations. Significant co-alteration of ATM and CADM1 points to their synergic action for the development of CACX. Mutation is, however, a rare phenomenon for inactivation of ATM. Association between the alteration of ATM and CHEK1 and poor survival of the patients having co-alterations of ATM and CHEK1 points to the DNA damage response pathway disruption in development of CACX. Thus, our data suggest that inactivation of ATM-CHEK1-associated DNA damage response pathway and CADM1-associated signaling network might have an important role in the development of CACX.

Identification of human papillomavirus type 16 integration sites in high-grade precancerous cervical lesions

OBJECTIVES

Infection with oncogenic human papillomaviruses (HPV) is a prerequisite for the development of cervical cancer. In many cases of cervical cancer and all cervical cancer derived cell lines oncogenic HPV DNA is found to be integrated, indicating the importance of integration in disease development. In this study, 176 HPV 16 positive precancerous cervical lesions were analyzed for the physical state of viral genome to determine the sites of integration into a host cell DNA and to evaluate the incidence of the integration in different stages of cervical lesions.

METHODS

The detection of integrated papillomavirus sequences (DIPS) method in combination with the amplification by polymerase chain reaction (PCR) of E1/E2 region was used to identify the physical state of HPV 16 genome. The site of integration within a host cell genome was determined by sequencing of unusual sized DIPS amplicons.

RESULTS

The combined results of DIPS and E1/E2 PCR revealed the integration of HPV 16 DNA in 7.4% samples. The integration was found only in high grade cervical lesions indicating that it is a late event in disease progression. Sequencing of 11 DIPS amplicons revealed HPV DNA from 6 samples (54.5%) to be integrated in cellular genes (VMP1, PVRL1, CHERP, CEACAM5, AHR, MRF-2) and also 6 (54.5%) within the common fragile sites (CFS).

CONCLUSIONS

Although, the HPV integration is known to be a random event, this study indicates that HPV 16 integrates more than by chance within or close to CFSs. As most of the genes affected by HPV 16 integration can be linked with some aspects of tumor formation, this indicates that the site of HPV DNA integration might play a role in the rate and the nature of tumor development.

OPCML gene promoter methylation and gene expression in tumor and stroma cells of invasive cervical carcinoma

To investigate the CpG island methylation and the mRNA expression of OPCML gene in patients with cervical carcinoma, we collected tumor and stroma cells from 36 invasive cervical carcinoma samples and 16 normal cervical tissues as well as Hela cells. Methylation specific PCR was used to detect promoter CpG island methylation status, and fluorescence quantitative RT-PCR was used to detection of OPCML gene expression. Our data showed that OPCML gene promoter methylation may play an important role in the carcinogenesis of cervical carcinoma and OPCML gene may be a cervical carcinoma-associated candidate TSG (tumor suppressor gene).

Cancer risk in patients with constitutional chromosome deletions: a nationwide British cohort study

The finding of increased risks of specific cancers in individuals with constitutional deletions of chromosomes 11p and 13q led to the discovery of cancer predisposition genes at these locations, but there have been no systematic studies of cancer risks in patients with constitutional deletions, across the chromosome complement. Therefore, we assessed cancer incidence in comparison with national cancer incidence rates in a follow-up of 2561 patients with constitutional autosomal chromosome deletions diagnosed by microscopy or fluorescence in situ hybridisation in Britain during the period 1965-2002. Thirty cancers other than non-melanoma skin cancer occurred in the cohort (standardised incidence ratio (SIR)=2.4, 95% confidence interval (CI) 1.6-3.5). There were significantly increased risks of renal cancer in persons with 11p deletions (SIR=1869, 95% CI 751-3850; P=4 x 10(-21)), eye cancer with 13q deletions (SIR=1084, 95% CI 295-2775; P=2 x 10(-11)), and anogenital cancer with 11q deletions (SIR=305, 95% CI 63-890; P=3 x 10(-7)); all the three latter cancers were in the 11 subjects with 11q24 deletions. The results strongly suggest that in addition to suppressor genes relating to Wilms' tumour risk on 11p and retinoblastoma on 13q, there are suppressor genes around 11q24 that greatly affect anogenital cancer risk.

Chromosomal gain of 3q and loss of 11q often associated with nodal metastasis in early stage cervical squamous cell carcinoma

BACKGROUND/PURPOSE

Cervical cancer remains a health problem among women worldwide. Delineation of genetic changes is critical to understanding the molecular basis of tumor progression, as well as for identifying genetic markers for early identification of patients at high risk for a poor outcome.

METHODS

To provide comparative genomic hybridization data for cervical squamous cell carcinoma in Taiwan, and to gain further insight into genetic markers associated with lymph node metastasis of this disease, we performed comparative genomic hybridization analysis of 30 consecutive cases of cervical squamous cell carcinoma (24 stage IB and 6 stage IIB).

RESULTS

The results disclosed that higher staged tumors or those with lymph node metastasis had more chromosomal imbalances. The commonly recurrent chromosomal imbalances were gains of 3q (46.7%), 1q (36.7%) and 8q (20.0%) and losses of 11q (36.7%), 3p (33.3%), 6q (23.3%), and 2q (20.0%). The frequencies of these chromosomal imbalances in stage IB and IIB tumors did not differ significantly. However, when compared with tumors without lymph node metastasis, the loss of 11q14-q22 (5/9 vs. 3/21, p = 0.019) and gains of 3q11-q22 and 3q26-qter (6/9 vs. 5/21, p = 0.026) were significantly more prevalent in tumors with lymph node metastasis.

CONCLUSION

The results suggest that certain tumor-associated genes residing on 3q and 11q warrant further investigation to elucidate their role in the progression of this disease.

Molecular biology of squamous cell carcinoma of the anus

BACKGROUND

Squamous cell carcinoma of the anal canal provides a model for studying the contribution of human papillomavirus (HPV) and human immunodeficiency virus (HIV) infection to the development of neoplasia. This paper reviews the existing literature relating to the molecular biology of anal squamous cell carcinoma and proposes a theory of pathogenesis.

METHODS

A Medline literature search was performed to identify English articles on the pathogenesis of squamous cell carcinoma of the anus; further articles were obtained from the references quoted in the literature initially reviewed.

RESULTS

HPV infection and subsequent HPV DNA integration are necessary, but not sufficient, to cause cancer progression. Loss of heterozygosity at 11q23 is the most consistent genomic change observed. Loss of heterozygosity at 17p, 18q and 5q is frequently observed in tumours of HIV-negative patients, but not in those of HIV-positive patients. Current data suggest that mutations in p53, DCC and APC tumour suppressor genes contribute to the stepwise progression of anal squamous cell carcinoma in immunocompetent individuals.

CONCLUSION

In comparison with immunocompetent individuals, HIV-positive patients have persistent HPV infection in the anal canal. In this population, microsatellite instability, rather than chromosomal instability, appears to be a preferred pathway for rapid progression towards invasive carcinoma.

HPV-mediated cervical carcinogenesis: concepts and clinical implications

Persistent infection with a high-risk human papillomavirus (hrHPV) is generally accepted as a necessary cause of cervical cancer. However, cervical cancer is a rare complication of an hrHPV infection since most such infections are transient, not even giving rise to cervical lesions. On average, it takes 12-15 years before a persistent hrHPV infection may ultimately, via consecutive premalignant stages (ie CIN lesions), lead to an overt cervical carcinoma. This argues that HPV-induced cervical carcinogenesis is multi-step in nature. In this review, the data from hrHPV-mediated in vitro transformation studies and those obtained from analysis of clinical specimens have been merged into a cervical cancer progression model. According to this model, a crucial decision maker in the early stages following infection involves individual susceptibility for certain HPV types depending on the genetic make-up of immune surveillance determinants. Once a CIN lesion has developed, altered transcriptional regulation of the viral E6/E7 oncogenes, resulting in genomic instability and distinguishing the process of cell transformation from a productive viral infection, probably provides the subsequent important step towards malignancy. The additional (epi)genetic alterations that subsequently accumulate in high-grade CIN lesions may result in overt malignancy via immortality and growth conditions that gradually become less sensitive to growth-modulating influences mediated by cytokines and cell-cell and cell-matrix adhesions. The potential implications of hrHPV testing and some other biomarkers deduced from this model for cervical screening and the clinical management of CIN disease are also discussed.

Increasing expression of serine protease matriptase in ovarian tumors: tissue microarray analysis of immunostaining score with clinicopathological parameters

Matriptase is a type II transmembrane serine protease expressed by cells of surface epithelial origin, including epithelial ovarian tumor cells. Matriptase cleaves and activates proteins implicated in the progression of cancer and represents a potential prognostic and therapeutic target. The aim of this study was to examine the expression of matriptase in ovarian tumors and to assign clinicopathological correlations. Immunohistochemical analysis of matriptase was performed in tissue microarrays of 164 ovarian neoplasms including 84 serous adenocarcinomas, 23 mucinous adenocarcinomas, 10 endometrioid adenocarcinomas, six yolk sac tumors, 12 clear cell carcinomas, six dysgerminomas, eight granulosa cell tumors, four transitional cell carcinomas, five fibromas, and six Brenner tumors. All ovarian tumors except the fibromas and Brenner tumors showed significant expression of matriptase. The matriptase scores were significantly higher in the tumors than in their nontumor counterparts (304+/-26 for serous adenocarcinoma; 361+/-28 for mucinous adenocarcinoma; 254+/-17 for endometrioid adenocarcinoma; 205+/-19 for yolk sac tumor; 162+/-16 for clear cell carcinoma; 109+/-11 for dysgerminoma; 105+/-9 for granulosa cell tumor; and 226+/-18 for transitional cell carcinoma). Matriptase scores in serous adenocarcinoma were correlated with TNM stage and FIGO stage. Our findings demonstrate for the first time that matriptase is overexpressed in many malignant ovarian tumors. It may be a novel biomarker for diagnosis and treatment of malignant ovarian tumors.

HPV-mediated transformation of the anogenital tract

Infection with high-risk human papillomavirus (HR-HPV) has been associated with intraepithelial neoplasia and carcinomas at various sites of the anogenital tract, including the cervix, vulva, vagina, penis and anus. Although HR-HPV is a necessary cause for cervical cancer, the majority of anal cancers and a subset of cancers at other genital sites, additional (epi)genetic events are required for malignant transformation. HPV-mediated transformation of human epithelial cells has been recognized as a multi-step process resulting from deregulated transcription of the viral oncogenes E6 and E7 in the proliferating cells. Interference of E6 and E7 with cell cycle regulators induces genetic instability, which drives the continuous selection of oncogenic alterations providing cells with a malignant phenotype. Early genetic events during cervical carcinogenesis associated with immortalization, include deletions at chromosomes 3p, 6 and 10p, whereas amongst others gain of chromosome 3q, loss of chromosome 11 and epigenetic alterations such as inactivation of the TSLC1 tumor suppressor gene represent later events associated with tumor invasion.

Fine mapping and evaluation of candidate genes for cervical cancer on 11q23

We previously showed that loss of heterozygosity (LOH) at 11q23 is a common genetic alteration in cervical cancer (CC) and that it correlates with extensive invasion of lymph-vascular spaces. In the current study, we looked for allelic loss in paired normal/tumor genomic DNA from 121 cervical tumors by using 20 well-mapped microsatellite markers on 11q. LOH at one or more loci was observed in 81 (66.9%) tumors. The deletion patterns in tumors are complex. However, at least three LOH islands could be defined between D11S614 and D11S4167. We also genotyped 11 CC cell lines and analyzed the results using the homozygosity mapping-of-deletions method. Five of the 11 cell lines showed continuous homozygosity that extended through 11q23.3-11q24.1. We used a candidate-gene approach to screen candidate tumor-suppressor genes (TSGs) that were localized in that region. Intragenic changes in the entire coding sequence of four candidate genes (RNF26, USP2, POU2F3, and TRIM29) in the region and a proposed TSG (PPP2R1B) centromeric to the region were evaluated. The expression status of USP2, POU2F3, TRIM29, and another proposed TSG that is telomeric to the region (BCSC1) also was examined. We identified previously described single-nucleotide polymorphisms (SNPs), several novel variants, and three rare SNPs in the five candidate genes. Decreased expression of POU2F3 and TRIM29 was found in some cervical tumors and CC cell lines. Our results indicate that a major region of LOH in cervical cancer exists within a 3.6-Mb stretch of DNA on 11q23.3-q24.1 and that somatic mutations in RNF26, USP2, TRIM29, POU2F3, or PPP2R1B probably are not important for cervical carcinogenesis.

Deletion in chromosome 11 and Bcl-1/Cyclin D1 alterations are independently associated with the development of uterine cervical carcinoma

PURPOSE

The aim of this study was to understand whether there is any association between specific deleted regions in chromosome 11 (chr.11) and alteration (amplification/rearrangement) of Bcl-1/Cyclin D1 locus, located at 11q13, in uterine cervical carcinoma (CA-CX).

METHODS

The deletion mapping of chr.11 was studied using 17 highly polymorphic microsatellite markers in 65 primary uterine cervical lesions. The Bcl-1/Cyclin D1 alterations were analyzed by Southern blot and/or polymerase chain reaction (PCR) method in respective cervical lesions.

RESULTS

Chr.11 deletion was found to be significantly associated with progression of CA-CX. High frequency (48-65%) of deletion was found in 11p15.5 (D1), 11q22.3-23.1(D2), and 11q23.3-24.1(D3) regions and significant association was seen among deletions in D2 and D3 regions. Bcl-1/Cyclin D1 locus alteration was observed in overall 27% cervical lesions. Co-amplification of Bcl-1/Cyclin D1 locus was seen in 10% samples. However, no association was found between the deleted regions and Bcl-1/Cyclin D1 locus alterations.

CONCLUSIONS

Our study suggests that there is no co-operativity between the deleted regions (D1- D3) in chr.11 and Bcl-1/Cyclin D1 alterations, but these alterations may provide cumulative effect in progression of the tumor. The D1-D3 regions may harbor candidate tumor suppressor gene(s) (TSGs) associated with the development of CA-CX.

Molecular biology of squamous cell carcinoma of the anus: a comparison of HIV-positive and HIV-negative patients

The molecular mechanisms involved in progression of squamous cell carcinoma of the anus (SCCA) are poorly elucidated, as well as the potential role of HIV infection. Loss of heterozygosity (LOH) is one of the mechanisms responsible for inactivation of tumor suppressor genes. We hypothesized that HIV-induced immunosuppression may contribute to an alternate molecular pathway in SCCA progression, through persistence of human papillomavirus infection within the anal canal. This study was undertaken to compare the molecular biology of SCCA in HIV-positive (HIV+) and HIV-negative (HIV-) patients. We retrieved tumor specimens from 18 HIV- and 10 HIV+ patients diagnosed with SCCA in two institutions. DNA from tumor and normal tissues was extracted and then amplified by polymerase chain reaction. LOH was investigated at 14 loci: three at 18q (DCC), two at 13q (Rb), three at 17p (p53), three at 11q, one at 2p, and two at 5q (APC). LOH was defined by a tumor DNA-to-normal tissue DNA ratio of >2. HIV+ patients were younger (36 +/- 7 years versus 53 +/- 13 years, P=0.001) and showed a trend toward tumors of larger size (3.7 +/- 1.6 cm versus 2.6 +/- 1.5 cm, P=0.09). The median CD4+ count in HIV+ patients at the time of diagnosis was 74 x 10(6)/L (range, 5-900). The overall frequency of LOH was 17.3% (41 LOH of 236 informative loci). Tumors in HIV- patients were more likely to present LOH than were tumors in HIV+ patients (24.1% versus 6.6%, P=0.0004). Differences between the two groups with regard to allelic losses were also observed at specific loci, such as 18q (41% [HIV-] versus 0% [HIV+], P=0.05), 17p (43% versus 10%, P=0.09), and 5q (33% versus 0%, P=0.12). Consistent LOH on chromosomes 17p, 18q, 5q, and 11q were observed in HIV- patients with SCCA. By contrast, allelic losses at 17p, 5q, and 18q seem to be rare in tumors of HIV+ individuals. These data suggest that immunosuppression may promote SCCA progression through an alternate pathway and that persistence of HPV infection within the anal canal may play a central role in this process.

Definition of a region of loss of heterozygosity at chromosome 11q23.3-25 in head and neck squamous cell carcinoma using laser capture microdissection technique

To date, loss of heterozygosity (LOH) studies on HNSCC have had limited success in identifying a confined region of loss on chromosome 11q partially due to the heterogeneous nature of tumor tissue examined. Additionally, little is known about the role of the 11q allelic deletion in HNSCC tumorigenesis and current reports are conflicting. The aim of this study was to better define LOH at distal 11q by using combination of a pure cell population procured by laser capture microdissection (LCM) and subsequent sensitive PCR amplification of polymorphic microsatellites. This study analyzed HNSCC for LOH using a panel of 5 microsatellite markers spanning 11q23-25. Thirty-four paired DNA samples from tumor and autologous normal tissue were harvested by LCM technique to ensure a pure cell population for PCR amplification. Approximately 2000 to 3000 cells were procured from each sample. Twenty-one of 34 cases (62%, P < 0.001) showed LOH on at least one of the loci examined. The highest frequency of LOH was found at the 11q23.3-25 segment, with 44% at marker D11S968 and 35% at marker D11S1316. A distinct novel region of frequent LOH at 11q23.3-25, defined by D11S1316 and D11S968, was identified. No allelic loss was found in any normal squamous tissue samples. To study LOH in HNSCC, combination of pure cell population procurement by LCM and sensitive PCR provides a more accurate approach than the conventional method using a bulk of heterogeneous tissue. A novel region of LOH at 11q23.3-25 was defined. LOH in this region may harbor putative tumor suppressor gene(s) critical for HNSCC. Furthermore, these allelic losses were not found in any non-neoplastic squamous tissue samples, clarifying prior discrepant data.

TSLC1 gene silencing in cervical cancer cell lines and cervical neoplasia

BACKGROUND

Cervical carcinogenesis is initiated by infection with high-risk (i.e., carcinogenic) human papillomavirus (HPV) types. The subsequent progression from premalignant cervical intraepithelial neoplasia (CIN) to invasive cancer is driven by both genetic and epigenetic processes. We assessed the role of the gene encoding the adhesion molecule tumor suppressor in lung cancer 1 (TSLC1) in this progression.

METHODS

We analyzed TSLC1 gene expression by real-time quantitative reverse transcription-polymerase chain reaction, promoter methylation by sodium bisulfite genomic DNA sequencing, and allelic loss by microsatellite analysis in primary keratinocytes, in four non-tumorigenic HPV-immortalized human keratinocyte cell lines, and in 11 human cervical cancer cell lines that were positive for a high-risk HPV DNA type and in normal cervical epithelial cells. We transfected cervical cancer SiHa cells that did not express TSLC1 mRNA with an expression vector containing the TSLC1 complementary DNA (cDNA) or an empty vector and analyzed transfectants for anchorage-independent growth and tumorigenicity in nude mice. We also examined TSLC1 promoter methylation in premalignant cervical lesions and in cervical carcinomas and smears. All statistical tests were two-sided.

RESULTS

TSLC1 mRNA was strongly reduced, relative to levels in primary keratinocytes, or absent in 10 (91%) of 11 cervical carcinoma cell lines but in none (0%) of the four HPV-immortalized cell lines (difference = 91%, 95% confidence interval [CI] = 74% to 100%; P =.004). The TSLC1 promoter was hypermethylated, relative to normal foreskin and cervical epithelial cells, in nine (82%) of the 11 cervical carcinoma cell lines but in none (0%) of the four HPV-immortalized cell lines (difference = 82%, 95 CI = 59% to 100%; P =.01). Seven (88%, 95% CI = 47% to 100%) of the eight SiHa/TSLC1 transfectants displayed a marked reduction in anchorage-independent growth (i.e., 0-100 colonies per 5000 cells) compared with none of the four (0%, 95% CI = 0% to 60%) SiHa transfectants bearing the empty vector (i.e., SiHa/hygro transfectants; difference = 88%, 95% CI = 65% to 100%; P =.01) or untransfected SiHa cells. All seven mice (100%, 95% CI = 59% to 100%) injected with untransfected SiHa cells or SiHa/hygro transfectants displayed tumors of at least 50 mm(3) by 2-6 weeks after injection compared with none of eight mice (0%, 95% CI = 0% to 37%) injected with the SiHa/TSLC1 transfectants (difference = 100%, 95% CI = 68% to 100%; P<.001). We detected TSLC1 promoter hypermethylation in seven (35%, 95% CI = 15% to 59%) of 20 high-grade CIN lesions (i.e., CIN II and III) and in 30 (58%, 95% CI = 43% to 71%) of 52 cervical squamous cell carcinomas compared with none (0%, 95% CI = 0% to 34%) of nine normal cervical epithelial biopsy samples and none (0%, 95% CI = 0% to 22%) of 12 CIN I lesions (P<.001 for cervical squamous cell cancer versus normal epithelial biopsy samples plus CIN I lesions).

CONCLUSIONS

TSLC1 gene silencing via promoter hypermethylation is a frequent event in the progression from high-risk HPV-containing, high-grade CIN lesions to invasive cervical cancer.

Localization of deletion to a 300 Kb interval of chromosome 11q13 in cervical cancer

Previous molecular genetic studies on HeLa cell (a cervical cancer cell line) derived non-tumorigenic and tumorigenic hybrids have localized a tumor suppressor gene to the long arm of chromosome 11. Analysis of cervical cancer cell lines using chromosome 11 specific probes showed deletion and translocation of 11q13 sequences in five out of eight cell lines. Fluorescence in situ hybridization (FISH), using 11q13 specific probes, has shown interstitial deletion of 11q13 sequences in the HeLa cells. In order to determine whether 11q13 deletions occur in primary cervical tumors, we analysed 36 tumors using 20 different microsatellite and RFLP markers. Semi automated fluorescein based allelotyping was performed to identify loss of heterozygosity (LOH) in tumors. The results showed allelic loss in 17 (47%) tumors. Three different regions of loss, one near MEN1, the second near D11S913, and the third near INT2 locus were observed. The smallest region of deletion overlap at the D11S913 locus was localized to a 300 Kb distance between D11S4908 and D11S5023. Fluorescence in situ hybridization (FISH), using 11q13 specific cosmid and BAC (bacterial artificial chromosome) probes, confirmed allelic deletion in the tumors. PCR analysis further identified homozygous deletion of 11q13 sequences in a primary tumor, in HeLa cells and in two HeLa cell derived tumorigenic hybrid cell lines. The homozygous deletion in the cell lines was mapped to a 5.7 kb sequence of 11q13. We hypothesize therefore that a putative cervical cancer tumor suppressor gene exists within the 300 kb of chromosome 11q13.

Genetic aberrations detected by comparative genomic hybridisation in vulvar cancers

Squamous cell carcinoma of the vulva is a disease of significant clinical importance, which arises in the presence or absence of human papillomavirus. We used comparative genomic hybridisation to document non-random chromosomal gains and losses within human papillomavirus positive and negative vulvar cancers. Gain of 3q was significantly more common in human papillomavirus-positive cancers compared to human papillomavirus-negative cancers. The smallest area of gain was 3q22-25, a chromosome region which is frequently gained in other human papillomavirus-related cancers. Chromosome 8q was more commonly gained in human papillomavirus-negative compared to human papillomavirus-positive cancers. 8q21 was the smallest region of gain, which has been identified in other, non-human papillomavirus-related cancers. Chromosome arms 3p and 11q were lost in both categories of vulvar cancer. This study has demonstrated chromosome locations important in the development of vulvar squamous cell carcinoma. Additionally, taken together with previous studies of human papillomavirus-positive cancers of other anogenital sites, the data indicate that one or more oncogenes important in the development and progression of human papillomavirus-induced carcinomas are located on 3q. The different genetic changes seen in human papillomavirus-positive and negative vulvar squamous cell carcinomas support the clinicopathological data indicating that these are different cancer types.

Microsatellite alteration at chromosome 11 in primary human nasopharyngeal carcinoma in Taiwan

Nasopharyngeal carcinoma (NPC) is one of the common cancers in Taiwan but is rare in western countries. The development of NPC involves multiple genetic changes in tumorigenesis and progression of the disease. To better understand genetic alterations in chromosome 11 which occur in human (NPC), we examined tumor specimens and corresponding non-cancerous tissue from 30 cases of NPC, using five microsatellite polymorphic markers whose location has previously been defined. To determine the clinical characteristics of MSI(+) or LOH, we performed correlation analysis of the findings with clinicopathological parameters. Loss of heterozygosity (LOH) was identified in 18 (60%) of 30 cases on at least one of the five markers. A high frequency of LOH was found at the two loci: D11S912 (7/30, 23.33%) and D11S934 (6/30, 20.00%), both of which are located within 11q23-24. We also found that 14 specimens (14/30, 46.67%) exhibited microsatellite instability (MSI(+)). Five (5/30, 16.67%) specimens exhibited MSI(+) in the transformation growth factor beta receptor type II (TGF-beta RII) exon 3 which also exhibited on chromosome 11. LOH was found to be significantly correlated with the T (tumor size) value (P=0.022) of Ho's system. MSI(+) showed a significant correlation with the N (lymph node) value of the UICC system (P=0.031). Our results suggest that multiple putative tumor suppressor genes on chromosome 11 play a role in the development of NPC. MSI(+) expression showed a predisposition to occur in the late stage of NPC while LOH tended to occur in early stages of NPC. The behavior of mutated TGF-beta RII exon 3, which appeared to serve as a dysfunction brake during nasopharyngeal carcinogenesis, may be a target gene in the defected mismatch repair system.

Loss of heterozygosity on chromosomes 11 and 17 are markers of recurrence in TCC of the bladder

Approximately 2/3 of patients diagnosed with superficial transitional cell carcinoma of the urinary bladder (TCC) will recur within 2 years. Loss of chromosome 9 and loss of heterozygosity (LOH) at 9q34 in index TCCs identify a subset of patients at high risk of recurrence. This study explores genetic alterations on chromosomes 4, 8, 11 and 17 as predictors of recurrence. A total of 109 carcinomas were investigated at 26 loci. DNA was extracted from microdissected archival normal/tumour tissue and was analysed for loss of heterozygosity (LOH). Fluorescent PCR was performed and genotyping carried out on a Perkin Elmer ABI377 sequencer. LOH of D11S490 or D17S928 was significantly more frequent in index carcinomas of patients who experienced recurrence compared to those with no recurrence (P = 0.004 and 0.019 respectively). These results suggest that loss of these regions is associated with recurrence of TCC. Further investigation is required to identify genes in these regions, which might be responsible for driving recurrence in TCC of the urinary bladder.

Microcell-mediated transfer of chromosome 4 into HeLa cells suppresses telomerase activity

Telomerase activity can be detected in most human cancers and immortal cell lines. In contrast, the lack of telomerase activity in normal diploid fibroblasts has been correlated with progressive reduction of telomere lengths to critically short sizes followed by the cessation of cell division and the onset of senescence. Several investigators have provided evidence for the localization of a telomerase suppressor gene on chromosome 3. The aim of our study was to determine whether other chromosomes are involved in telomerase repression. Beside human chromosome 3 (serving as positive control), chromosomes 4, 6, and 11 were introduced into HeLa cells via microcell-mediated chromosome transfer. Telomerase activity from different hybrid cell lysates was determined at an early time point after fusion using a Telomerase ELISA kit. Strong repression of telomerase activity was only found in a subset of HeLa hybrids in which chromosome 3 or chromosome 4 had been introduced. Telomerase suppression induced by chromosome 3 or 4 transfer was paralleled by a high frequency (30% or 43%, respectively) of a senescent-like phenotype. Chromosomes 6 and 11, the functional loss of which is also implicated in cervical cancer, had no effect. These results indicate that normal human chromosomes 3 and 4 carry a gene or genes that suppress telomerase activity and induce cellular senescence in HeLa cells.

Loss of heterozygosity at 11q23.3 in vasculoinvasive and metastatic squamous cell carcinoma of the cervix

We have previously demonstrated a strong relationship between loss of heterozygosity (LOH) at chromosome 11q23.3 and the presence of extensive tumor plugs in lymphvascular spaces (LVS) in stage 1B cervical carcinoma, suggesting that genes at this locus may regulate vasculoinvasion. This study examined LOH at 11q23.3 in microdissected tumor plugs within LVS and in metastatic foci in lymph nodes (MFLN), as well as corresponding invasive tumor and adjacent cervical intraepithelial neoplasia (CIN) 3 in stage 1B squamous cell carcinoma. Of 49 invasive carcinomas, 38.8% had LOH at 11q23.3. Of 36 tumor plugs in LVS, 39% had LOH at 11q23.3. Twenty percent of 15 MFLN demonstrated LOH at 11q23.3. Patients with LOH at 11q23.3 are significantly more likely to have disease recurrence than patients without LOH at 11q23.3 (P =.02). Of 10 foci of CIN 3, none showed LOH at 11q23.3. Although unlikely to have an impact early in carcinogenesis, tumor-suppressor genes located in the region of 11q23.3 appear to be important in tumor progression, facilitating lymphvascular space invasion and, by inference, spread to lymph nodes in squamous cell carcinoma of the cervix.

Recessive oncogenes: current status

Cell growth is under the control of a variety of positive and negative signals. An imbalance of such signals results in deregulation of cell behavior. Recessive oncogenes or tumor suppressor genes, opposite to dominant oncogenes, encode important cellular proteins which could function as negative regulators of the cell cycle, i.e., cell cycle brakes. Inactivation of recessive oncogenes, by allelic deletion, loss of expression, mutation, or functional inactivation by interacting with oncogene products of DNA tumor viruses or with amplified cellular binding proteins, will lead to uncontrolled cell growth or tumor formation. Besides the classic suppressor genes such as the p53 and RB, a growing number of novel tumor suppressor genes have been identified in recent years. While some tumor suppressor genes have been found to be important for the development of a large number of human malignancies (e.g., the p53 gene), others are more tumor type-specific (e.g., the NF-1 gene). Many human cancer types showed abnormalities of multiple tumor suppressor genes, offering strong support to the concept that tumorigenesis and progression result from an accumulation of multiple genetic alterations. In this review, we will begin with an overview (gene, transcript, protein and mechanisms of action) of the tumor suppressor genes (the RB, p53, DCC, APC, MCC, WT1, VHL, MST1, and BRCA1 genes) identified to date and then discuss the specific involvement of tumor suppressor genes in human malignancies including prostate cancer. Various chromosomal regions which potentially may contain tumor suppressor genes also will be reviewed.

Altered expression of the ERM proteins in lung adenocarcinoma

Radixin is a member of the ERM (ezrin/radixin/moesin) protein family that is proposed to function as a membrane-cytoskeletal linker. Using differential display analysis, we have identified radixin as a gene down-regulated in primary lung adenocarcinoma. Real-time quantitative reverse transcription polymerase chain reaction confirmed that radixin mRNA was decreased, both in 10 early-stage bronchioloalveolar carcinomas and in 16 invasive lung adenocarcinomas, by 69% (p = 0.0002) and 82% (p < 0.0001), respectively, compared with 9 nontumor lung tissues. Similarly, moesin and ezrin mRNA levels were reduced in lung adenocarcinoma. Immunohistochemistry confirmed that cancer cells expressed very little radixin and moesin, whereas non-neoplastic alveolar and bronchiolar epithelial cells, and endothelial cells, including those within the tumor stroma, were consistently positive for these two proteins. Ezrin was localized in the apical surface of non-neoplastic bronchiolar and alveolar epithelial cells and, in contrast to radixin and moesin, the majority of tumor cells retained expression of ezrin. Localization of ezrin was altered in a significant proportion of tumor cells: whereas tumor cells forming lumina displayed membranous staining on the apical side, tumor cells with disorganized structures were either negative or diffusely positive for ezrin in the cytoplasm. Furthermore, a fraction of tumor cells invading the stroma in a scattered manner were strongly positive for ezrin. In conclusion, expression of radixin and moesin is down-regulated in lung adenocarcinoma, including early-stage bronchioloalveolar carcinoma. An intriguing implication of this finding is that these two genes may function as tumor suppressors in lung adenocarcinoma oncogenesis. Although structurally related to radixin and moesin, ezrin may have a distinct function in tumor-cell invasion.

Interstitial deletion of 11q13 sequences in HeLa cells

Previous cytogenetic and molecular genetic studies have shown that the HeLa (cervical carcinoma) cell line D98/AH-2 contains two apparently normal copies of chromosome 11 and additional 11q13-25 material translocated onto a chromosome 3 marker. To determine the 11q13 breakpoint, we performed fluorescence in situ hybridization (FISH) using 18 different 11q13 specific BAC (bacterial artificial chromosome) and cosmid probes spanning a 5.6 Mb interval. Markers localized to the multiple endocrine neoplasia type 1 (MEN1) gene (menin) were also included in the analysis. The FISH study identified an interstitial deletion between markers D11S449 and GSTP1, an interval of 2.3 Mb, in the marker chromosome. This deletion did not include the MEN1 gene. Because point mutations and methylations can inactivate the MEN1 gene, single stranded conformational polymorphism (SSCP) and Northern and Western blot analyses were performed with MEN1 specific probes and antibody. SSCP did not reveal mutations of the MEN1 gene in HeLa or in seven other cervical cancer cell lines. Northern and Western blot studies revealed normal levels of expression of this gene in the cervical cancer cell lines as well as in HeLa cell derived tumorigenic hybrids. Because deletions of tumor suppressor genes often occur in cancer progression, we hypothesize that the inactivation of a tumor suppressor gene other than MEN1, localized to the 2.3 Mb interval on 11q13, might play a role in the abnormal growth behavior of HeLa cells in vitro or in vivo.

Detailed deletion mapping at chromosome 11q23 in colorectal carcinoma

Loss of heterozygosity (LOH) is frequent at the chromosomal region 11q22-q23 in several types of tumours of diverse cell origin. Previous investigations of LOH at this chromosomal region in colorectal carcinoma have been contradictory in their findings, and have only included between 1-4 loci. In order to define any regions of LOH on 11q23, we investigated 16 loci between D11S940 and D11S934 on the long arm of chromosome 11 using microsatellite analysis. Of 57 colorectal carcinomas specimens, 36 (63.2%) demonstrated LOH at one or more marker, with the highest frequencies of LOH at D11S1340 (41.0%), located between 105.13-111.97 Mb from the centromere, and D11S924 (37.1%) and D11S4107 (40.5%), both located approximately 113 Mb from the centromere. No statistically significant associations between LOH and age-of-presentation or Dukes' stage were found. LOH was observed in colorectal tumours of all Dukes' stages, including Dukes' stages A and B, suggesting that the inactivation of a tumour suppressor gene(s) on 11q23 occurs in the early stages of colorectal carcinoma. These results confirm the presence of putative tumour suppressor gene(s) at chromosome 11q23, involved in the carcinogenesis of colorectal carcinoma, and will facilitate future identification of candidate genes.

Altered response of a human squamous cell carcinoma cell line to 1, 25-dihydroxyvitamin D(3) after transfer of a normal chromosome 11

Previous work in our laboratory using functional assays for tumorigenicity identified a tumor suppressor element on human chromosome 11q for the cutaneous squamous cell carcinoma cell line A388.6TG.c2. In this report, we screened a variety of agents for differential effects on A388.6TG.c2 compared to a growth-suppressed chromosome 11 microcell hybrid of A388.6TG.c2. One of the agents, 1, 25-dihydroxyvitamin D(3) (1,25(OH)(2)D(3); calcitriol), exerted a growth-altering effect on A388.6TG.c2, which formed rounded cell clusters across the surface of the raft by Day 6 of treatment. In contrast, full-length chromosome 11 hybrids of A388.6TG.c2, as well as two other squamous cell carcinoma cell lines (FaDu and A431), when treated with 1,25(OH)(2)D(3), failed to demonstrate this cell-clumping phenotype. To pursue the hypothesis that the growth suppressor element is involved in altering the response to 1, 25(OH)(2)D(3), we tested microcell hybrids carrying t(X;11) chromosomes lacking large portions of 11q. Although these hybrids, like the parent A388.6TG.c2 cells, demonstrated extensive growth in organotypic cultures, they failed to form cell clusters with 1, 25(OH)(2)D(3) treatment. These results suggest that the chromosome 11 element that alters the response to 1,25(OH)(2)D(3) is distinct from the growth-suppressing element. An examination of differentiation marker expression revealed identical patterns of basal and suprabasal markers for A388.6TG.c2 and for a chromosome 11 hybrid with or without treatment with 1,25(OH)(2)D(3). Finally, characterization of candidate tumor suppressor gene PPP2R1B, which encodes for a subunit of protein phosphatase 2A (PP2A), showed seemingly insignificant alterations by cDNA sequence analysis. Collectively, the data suggest that human chromosome 11 contains two different tumor suppressor elements that may account for the two areas of loss of heterozygosity observed on the long arm of this chromosome.

Localization of multiple melanoma tumor-suppressor genes on chromosome 11 by use of homozygosity mapping-of-deletions analysis

Loss-of-heterozygosity (LOH) studies have implicated one or more chromosome 11 tumor-suppressor gene(s) in the development of cutaneous melanoma as well as a variety of other forms of human cancer. In the present study, we have identified multiple independent critical regions on this chromosome by use of homozygosity mapping of deletions (HOMOD) analysis. This method of analysis involved the use of highly polymorphic microsatellite markers and statistics to identify regions of hemizygous deletion in unmatched melanoma cell line DNAs. Regions of loss were defined by the presence of an extended region of homozygosity (ERH) at > or =5 adjacent markers and having a statistical probability of < or =.001. Significant ERHs were similar in nature to deletions identified by LOH analyses performed on uncultured melanomas, although a higher frequency of loss (24 [60%] of 40 vs. 16 [34%] of 47) was observed in the cell lines. Overall, six small regions of overlapping deletions (SROs) were identified on chromosome 11 flanked by the markers D11S1338/D11S907 (11p13-15.5 [SRO1]), D11S1344/D11S11385 (11p11.2 [SRO2]), D11S917/D11S1886 (11q21-22.3 [SRO3]), D11S927/D11S4094 (11q23 [SRO4]), AFM210ve3/D11S990 (11q24 [SRO5]), and D11S1351/D11S4123 (11q24-25 [SRO6]). We propose that HOMOD analysis can be used as an adjunct to LOH analysis in the localization of tumor-suppressor genes.

Comparison of the genetic alterations in two epithelial collision tumors of the uterine cervix. A report of two cases

In a minority of cervical carcinomas, a distinct adenocarcinoma and squamous cell carcinoma component can be recognized. These tumors are considered collision tumors; the differential diagnosis is adenosquamous carcinoma. To investigate whether the squamous and adenocarcinoma component are of multiclonal or monoclonal origin, we used loss of heterozygosity (LOH) as a method to establish clonality. Each tumor component of two tumors with a distinct adenocarcinoma and squamous cell carcinoma component were microdissected and the presence of LOH was studied for nine chromosomes, i.e., 1, 2, 3, 6, 11, 15, 17, 18, and X, which are known to contain frequent LOH in cervical cancer. The tumor of patient AK13 showed identical LOH in both the adenocarcinoma and squamous cell carcinoma tissue with various microsatellite markers on chromosomes 1, 2, 6, 18, and X. For markers on chromosomes 3 and 15, different LOH patterns were found in both components. The squamous epithelium showed LOH on chromosome 3, whereas the adenocarcinoma component had LOH on chromosome 15. For patient AK18 the LOH pattern on chromosomes 6p and 17 was the same in the adenocarcinoma and the squamous cell carcinoma component. The adenocarcinoma component showed additional LOH on chromosomes 6q and chromosome 11q. The tumor of patient AK18 showed common boundaries of LOH in both components on chromosome 17q, between markers D17S578 and D17S250. In conclusion, the squamous cell carcinoma and adenocarcinoma components in both tumors most likely have one cell of origin because many genetic alterations are the same in each component. The presence of genetic changes uniquely associated with one of the tumors favors a diversion of developmental pathways.

Microsatellite alterations on human chromosome 11 in in situ and invasive breast cancer: a microdissection microsatellite analysis and correlation with p53, ER (estrogen receptor), and PR (progesterone receptor) protein immunoreactivity

BACKGROUND AND OBJECTIVES

Microsatellite instability (MSI) has been documented in a subset of sporadic tumors. Loss of heterozygosity (LOH) on chromosome 11 loci in breast cancer is a frequent event. The purpose of the present study is to examine the incidence of microsatellite alterations in in situ and invasive human breast carcinoma and to clarify their significance in regulating the dynamics of cancer progression.

METHODS

Four highly polymorphic (CA)n repeat microsatellites were used to determine microsatellite alterations in ten ductal carcinoma in situ (DCIS) and 19 invasive ductal carcinoma (IDC). To investigate the expression of p53, ER (estrogen receptor), and PR (progesterone receptor) association with MSI, immunohistochemistry staining was applied.

RESULTS

MSI were detected in 20% (2/10) of DCIS and in 47.4% (9/19) of IDC. The frequency of MSI in IDC was significantly higher than that in DCIS (P < 0.001). Also, the MSI seemed to correlate with clinical stage (P = 0.0001) and tumor size (P = 0.004) but not histological grade or age. In addition, we found that 27% of the tumors showed LOH at 11q23.3-24 region between loci D11S934 and D11S912. Seven of nine MSI cases demonstrated low or no expression of p53. However, there was significantly reduced expression of PR, but not ER in MSI cases.

CONCLUSIONS

Our results suggest that breast cancer acquires the RER phenotype (replication-error phenotype) in the relatively late stages, and that the RER phenotype is associated with aggressiveness of IDC (infiltrative duct carcinoma). The result also implicated that mismatch repair failure can alter the expression of PR but not ER and p53.

Comparison of chromosome 3p deletions between cervical precancers synchronous with and without invasive cancer

Cervical cancers are considered to originate from a series of pre-malignant lesions (cervical intra-epithelial neoplasia, CIN). The mechanisms behind these events are unknown. In addition to HPV infection, deletions of chromosome 3p have been found to be a frequent event in cervical cancer and likely play an important role in the transition of CIN to invasive cancer. To classify the potential role of 3p deletions in early-stage cervical carcinogenesis, we analyzed LOH of 3p in cervical precancers. Thirty cases with single or multiple CIN lesions were selected for the study, including 20 cases without and 10 cases with synchronous invasive cancers. Allelic losses on 1 or more 3p loci were recorded in 33% (3/9) of CIN II and 36% (5/14) of CIN III lesions from 20 cases without co-existing invasive cancer, whereas an increasing percentage of LOH was observed in the 10 precancerous lesions synchronous with invasive cancer, with 71% (5/7) CIN II and 76% (13/17) CIN III lesions. This result implies that 3p deletions have selective roles in early transition of pre-malignancy to invasive cancer. Comparing the LOH patterns between the 2 groups, genetic deletions in cases with invasive cancers involved extensive regions of 3p but were more localized in precancer cases without concomitant invasive cancer. Two interstitial regions, 3p22-21.3 around marker D3S1260 and 3p21.1 around markers D3S1289 and D3S1076, were most frequently deleted in both groups, suggesting that these 2 regions are novel tumor-suppressor loci which may play a role in early transition of cervical precancer to invasive cancer. Identical LOH patterns between multiple CIN lesions and synchronous invasive cancer in the same case suggests that different cervical precancers and invasive cancer are genetically linked and most likely originate from a single precursor cell.

Biomarkers and molecular epidemiology and chemoprevention of oral carcinogenesis

Chemopreventives are chemicals that prevent the formation of cancers such as oral cancer. They can take the form of nutrients or synthetic molecules, and their fundamental characteristic is that they do not produce disease processes that would result in debilitating symptoms. Current evidence indicates that they function by modifying the oxidative state of transforming cells. Biomarkers can take the form of genetic and molecular indicators, which characterize the function of chemopreventives and cancer processes such as oral carcinogenesis. Biomarkers cannot provide all the required information for risk assessment or possible activity of the chemopreventives. Other methods, such as epidemiological analyses and techniques, must be used to enhance our understanding of the risk for oral cancer in human populations. One common epidemiologic method, the questionnaire, helps to determine the use and carcinogenic potential of tobacco and alcohol during oral carcinogenesis. Genetic and molecular changes in human patient populations may result in a reduction in the number and function of tumor suppressor genes. If these changes are to be assessed, the tissues (e.g., buccal mucosa) must be accessible and harvested in a reliable and consistent manner for the acquisition of DNA, mRNA, and protein. Oral tissues provide sufficient quantities of these molecules and, under stringent conditions, the quality required for the isolation of these molecular constituents. In conjunction with epidemiologic techniques, various genotypic polymorphisms, such as glutathione-S-transferase (GSTM1) or cytochrome P450 (CYP450A1), have indicated a loss in carcinogen detoxification or the processing of internal growth control signals. Biomarkers are composed of a large diverse group of genetic and molecular structures. Some of these biomarkers are indicators for programmed cell death (PCD), while others describe malignant tumor growth. Many of these classes of molecules are oxidative-responsive (e.g., tumor suppressor p53, Bcl-2, growth factors, immune-derived proteins, and death-inducing molecules) and induce PCD by triggering a cascade of cysteine proteases and regulators (e.g., caspases, death receptors). This pathway results in cell-cycle alterations and DNA fragmentation. It is hoped that a detailed knowledge of the processes involved in malignant transformation will better define the biomarker-screening tools for oral cancer. These tools will enhance our ability to predict the incidence of cancer, detect early malignant change, and quantitate chemoprevention during oral carcinogenesis. Chemopreventives such as the retinoids have already demonstrated their ability to suppress potential malignant changes in pre-malignant oral leukoplakias and decrease the incidence of second head-and-neck cancer primaries. It is our hope that this review will increase investigators' interest in developing new screening and detection systems for oral cancer.

Low frequency of alterations of the alpha (PPP2R1A) and beta (PPP2R1B) isoforms of the subunit A of the serine-threonine phosphatase 2A in human neoplasms

The phosphatase 2A (PP2A) is one of the major cellular serine-threonine phosphatases. It was recently shown that the gene encoding for the beta isoform of its subunit A, PPP2R1B, is altered in human lung and colorectal carcinomas, suggesting a role in human tumorigenesis. Here, we report the detection of mutations in breast, lung carcinomas and melanomas in the genes of both alpha (PPP2R1A) and beta isoforms. Mutations affecting PPP2R1B were found in four breast carcinomas, while mutations in PPP2R1A were found in carcinomas of the breast and of the lung and in one melanoma. Most of the mutations affecting PPP2R1B were exons deletions, suggesting abnormal splicing. These splicing abnormalities were detected in tumor samples in the absence of the normal splicing product, and were not found in several normal controls. In one case, a homozygous deletion present in tumor DNA, and not in the matched normal control was demonstrated. Mutations affecting the PPP2R1A gene were nucleotide substitutions changing highly conserved amino acids and one frame-shift. Although the frequency of alterations is low, the inclusion of both isoforms of subunit A in the genes mutated in human cancer and the addition of breast cancer to the list of neoplasms in which PPP2R1B is altered, strengthen the potential role of PP2A in human tumorogenesis.

Mutation analysis of the putative tumor suppressor gene PTEN/MMAC1 in cervical cancer

OBJECTIVE

PTEN/MMAC1, a candidate tumor suppressor gene located at chromosome 10q23.3, was recently identified and found to be homozygously deleted or mutated in several different types of human tumors. The aim of this study is to determine whether PTEN/MMAC1 is a target for 10q loss of heterozygosity in cervical cancer.

METHOD

We examined 50 primary cervical carcinoma specimens using a PCR-based assay followed by SSCP and direct sequencing. The genomic DNA was also confirmed by Southern blot analysis.

RESULTS

All specimens except one, which has a 7-base deletion, showed a negative result. Among them, 30 randomly selected cases and their paired noncancerous tissue were further screened using nested RT-PCR. Six of 30 cervical cancerous tissues had aberrant transcripts. However, 4 of the matched noncancerous tissues also had aberrant transcripts. Southern blot analysis of the entire genomic DNA did not reveal any evidence of gene alteration.

CONCLUSIONS

Sequence abnormalities in the PTEN/MMAC1 gene were only detected in 1 of 50 cervical cancers analyzed indicating that aberrant PTEN/MMAC1 function is an uncommon event in the development of cervix cancers. However, similar to studies with the TSG101 gene, screening for aberrant transcripts of PTEN/MMAC1 with nested RT-PCR may detect transcripts, which, although they vary from the normal size, may not be related to oncogenesis as they are also frequently found in normal tissues of the same patient.

A 2-Mb sequence-ready contig map and a novel immunoglobulin superfamily gene IGSF4 in the LOH region of chromosome 11q23.2

Human chromosome 11q23.2 has been proposed to contain a tumor suppressor gene(s) whose deletion has been associated with cancer of the lung and breast and with neuroblastoma. To analyze the genomic structure and to isolate a candidate tumor suppressor gene from this region, we constructed a 2-Mb sequence-ready contig map using bacteriophage P1 (P1), bacterial artificial chromosome (BAC), and P1-derived artificial chromosome (PAC). The map comprises a contig of 24 overlapping P1, BAC, and PAC clones. To isolate gene fragments from the region, we performed direct cDNA library screening, exon trapping, EST mapping, and genomic sequencing using the P1, BAC, and PAC clones. Sequence analysis of 5 clones, which spans 23% (458,738 bp) of the region, and extensive gene scanning along the entire region revealed that the region is extraordinarily scarce in genes, but we identified one ubiquitously expressed novel gene and one testis-specific gene fragment. The novel gene, which we call IGSF4 (immunoglobulin superfamily 4), is transcribed into a 1.6- or 4.4-kb RNA encoding a 442-amino-acid protein. It shares strong homology with mouse IGSF-B12 and cell adhesion molecules NCAM1 and NCAM2 within their Ig-like C2-type domains. The IGSF4 gene, a novel gene that is shown to be located in the common loss of heterozygosity region, possesses a number of interesting features and may be good candidate for a tumor suppressor gene.

Evidence that Leydig cells in Sertoli-Leydig cell tumors have a reactive rather than a neoplastic profile

BACKGROUND

Leydig cells are a variable and an inconstant feature of Sertoli-Leydig cell tumors (SLCT). Controversy exists regarding their neoplastic versus reactive nature, and their molecular biologic profile is unknown.

METHODS

Six SLCT and one pure Leydig cell tumor were studied. Mitotic counts and immunohistochemistry for Ki-67 were performed in all cases. Leydig cells, neoplastic tissues, and normal nonneoplastic tissues were microdissected. DNA extracts of these samples were assessed for loss of heterozygosity (LOH) by polymerase chain reaction amplification with ten polymorphic DNA markers that have shown high rates of LOH in a variety of human tumors. Three SLCT and the Leydig cell tumor were assessed for clonality by examining the DNA methylation pattern at a polymorphic site on the androgen receptor gene.

RESULTS

Leydig cells in SLCT had a low mitotic count (0-1/50 high-power fields [HPF]) compared with the neoplastic stroma (median, 40/50 HPF). Ki-67 was positive in < 2% of Leydig cells in all SLCT, compared with a median of 7% in the neoplastic stroma. Clonality analysis confirmed the monoclonality of the neoplastic cells in the Leydig cell tumor. However, the Leydig cells from three SLCT were polyclonal, whereas the monoclonal nature of the neoplastic Sertoli tubules was confirmed in one of these cases and that of mucinous heterologous elements in another case. The Leydig cell tumor showed LOH at four of the eight loci evaluated. Leydig cells from five SLCT were evaluated: one showed LOH at one locus, two showed LOH at two loci, and the remaining two showed no LOH.

CONCLUSIONS

The demonstration that Leydig cells from SLCT are polyclonal strongly suggests that they are nonneoplastic in nature. This is supported by a low proliferation fraction and a lower fraction of LOH compared with the truly neoplastic Leydig cells.

Genetic alterations during the progression of squamous cell carcinomas of the uterine cervix

Most cervical carcinomas appear to arise from cervical intraepithelial neoplasia (CIN) lesions. In addition to infection with high-risk human papilloma viruses, which is indicative of an increased risk of progression, alterations of oncogenes and tumor suppressor genes play a role. Genetic studies of CIN lesions, primary cervical carcinoma, and metastases may shed light on the relative importance of various genetic alterations involved in the progression of CIN to invasive carcinoma. We examined tumor material from 10 patients with squamous cell carcinoma of the uterine cervix and synchronous CIN lesions and lymph node metastases. The CIN component, invasive carcinoma, and lymph node metastases were analyzed separately for loss of heterozygosity (LOH) on the following loci: VHL (3p21), HLA region (6p22-23), PGL (11q 22-24), E6 associated protein (15q11-13), TP53 (17p13), DCC (18q21.1), and chromosomes 1, 2, 4, 9, 20, and X. Using immunohistochemistry, the expression of the EGF receptor, ERBB2, and TP53 was determined. In CIN lesions, frequent LOH was found at chromosome arms 3p, 6p, and 11q. Primary invasive carcinoma showed additional LOH at chromosome arms 6q, 17p, and 18q. In lymph node metastases, an additional locus on the X chromosome displayed LOH. All carcinomas and synchronous lesions but one showed high expression levels of the EGF receptor. TP53 staining, when present, was found in all synchronous lesions. Focal staining of ERBB2 was found in one CIN lesion, two invasive carcinomas, and four metastases. The molecular alterations accumulated in a fashion that paralleled the progression of the tumors. These results indicate that cervical tumorigenesis occurs in a stepwise fashion, including infection and integration of oncogenic HPV and several specific genetic alterations. Genes Chromosomes Cancer 26:346-354, 1999.

High incidence of cancer in a family segregating a mutation of the ATM gene: possible role of ATM heterozygosity in cancer

ATM mutations predispose cells to malignancy by promoting chromosomal instability. We have identified a family with multiple cancers that segregates a mutant allele of ATM, IVS61+2insTA, which causes skipping of exon 61 in the mRNA, as well as a previously undescribed polymorphism, IVS61+104C(54):T(46). The mutation was inherited by two sisters, one who developed breast cancer at age 39 and the second at age 44, from their mother, who developed kidney cancer at age 67. Molecular studies were undertaken to determine the role of the ATM gene in the development of cancer in this family. Studies of irradiated lymphocytes from both sisters revealed elevated numbers of chromatid breaks, typical of A-T heterozygotes. Studies on lymphoblastoid cell lines established from these individuals revealed abnormal p53 induction and apoptosis after DNA damage. Loss of heterozygosity (LOH) in the ATM region of chromosome 11q23.1 showed that the normal ATM allele was lost in the breast tumor of the older sister. LOH was not seen at the BRCA1 or BRCA2 loci. BRCA2 is not likely to be a cancer-predisposing gene in this family because each sister inherited different chromosomes 13 from each parent. The sisters share their maternal BRCA1 allele, although no mutation in this gene was detected in the family. Our findings suggest that haploinsufficiency at ATM may promote tumorigenesis, even though LOH at the locus supports a more classic two-hit tumor suppressor gene model.

DNA copy number losses in human neoplasms

This review summarizes reports of recurrent DNA sequence copy number losses in human neoplasms detected by comparative genomic hybridization. Recurrent losses that affect each of the chromosome arms in 73 tumor types are tabulated from 169 reports. The tables are available online at http://www.amjpathol.org and http://www. helsinki.fi/ approximately lglvwww/CMG.html. The genes relevant to the lost regions are discussed for each of the chromosomes. The review is supplemented also by a list of known and putative tumor suppressor genes and DNA repair genes (see Table 1, online). Losses are found in all chromosome arms, but they seem to be relatively rare at 1q, 2p, 3q, 5p, 6p, 7p, 7q, 8q, 12p, and 20q. Losses and their minimal common overlapping areas that were present in a great proportion of the 73 tumor entities reported in Table 2 (see online) are (in descending order of frequency): 9p23-p24 (48%), 13q21 (47%), 6q16 (44%), 6q26-q27 (44%), 8p23 (37%), 18q22-q23 (37%), 17p12-p13 (34%), 1p36.1 (34%), 11q23 (33%), 1p22 (32%), 4q32-qter (31%), 14q22-q23 (25%), 10q23 (25%), 10q25-qter (25%),15q21 (23%), 16q22 (23%), 5q21 (23%), 3p12-p14 (22%), 22q12 (22%), Xp21 (21%), Xq21 (21%), and 10p12 (20%). The frequency of losses at chromosomes 7 and 20 was less than 10% in all tumors. The chromosomal regions in which the most frequent losses are found implicate locations of essential tumor suppressor genes and DNA repair genes that may be involved in the pathogenesis of several tumor types.

Identification of amplified genes in a patient with acute myeloid leukemia and double minute chromosomes

A case of acute myeloid leukemia (M2) with double minute chromosomes and complex karyotypic abnormalities was analyzed cytogenetically and molecularly. Comparative genomic hybridization (CGH) showed that the 8q24 region that contains the MYC oncogene was not amplified. Instead, amplification of chromosomal regions 11q23-->qter and 9p11-->pter was identified. Southern blot analysis confirmed the CGH findings and showed that the ETS1, FLI1, SRPR, NFRKB, and KCNJ5 genes located at 11q23-->24 were amplified, whereas the MLL at 11q23 was not amplified. Additionally, the IFN beta 1 and CDKN2A genes at 9p were amplified, but to a lesser degree. This is the first example of a case of acute myeloid leukemia with double minute chromosomes that has not involved amplification of either the MYC or the MLL genes.

Genomic structure of the human PLZF gene

The human PLZF (promyelocytic leukaemia zinc finger) gene encodes a Krüppel-like zinc finger protein, which was identified via the reciprocal translocation t(11;17)(q23;q21) fusing it to the retinoic acid receptor alpha (RARalpha) gene in promyelocytic leukaemia. To determine its complete genomic organisation, we constructed a cosmid-map fully containing the hPLZF gene. The gene has seven exons, including a novel 5' untranslated exon, varying in size from 87 to 1358bp and spans at least 120kb. Flanking intronic sequences were identified and all splice acceptor and donor sites conformed to the gt/ag rule. Five polymorphic markers could be fine located in its vicinity. These data will facilitate mutation analysis of hPLZF in t(11;17) leukaemia cases, as well as assist mapping and loss-of-heterozygosity analysis. Here we have tested hPLZF as a possible candidate for the PGL1 locus involved in hereditary head and neck paragangliomas. However, mutation analysis revealed no aberration in 12 paraganglioma patients from different families.

The molecular genetics of cervical carcinoma

In the pathogenesis of cervical carcinoma there are three major components, two of them related to the role of human papillomaviruses (HPV). First, the effect of viral E6 and E7 proteins. Second, the integration of viral DNA in chromosomal regions associated with well known tumour phenotypes. Some of these viral integrations occur recurrently at specific chromosomal locations, such as 8q24 and 12q15, both harbouring HPV18 and HPV16. And third, there are other recurrent genetic alterations not linked to HPV. Recurrent losses of heterozygosity (LOH) have been detected in chromosome regions 3p14-22, 4p16, 5p15, 6p21-22, 11q23, 17p13.3 without effect on p53, 18q12-22 and 19q13, all of them suggesting the alteration of putative tumour suppressor genes not yet identified. Recurrent amplification has been mapped to 3q+ arm, with the common region in 3q24-28 in 90% of invasive carcinomas. The mutator phenotype, microsatellite instability, plays a minor role and is detected in only 7% of cervical carcinomas. The development of cervical carcinoma requires the sequential occurrence and selection of several genetic alterations. The identification of the specific genes involved, and their correlation with specific tumour properties and stages could improve the understanding and perhaps the management of cervical carcinoma.