Alain Latil

Predisposing Gene for Early-Onset Prostate Cancer, Localized on Chromosome 1q42.2-43

There is genetic predisposition associated with >=10% of all cancer of the prostate (CaP). By means of a genomewide search on a selection of 47 French and German families, parametric and nonparametric linkage (NPL) analysis allowed identification of a locus, on chromosome 1q42.2-43, carrying a putative predisposing gene for CaP (PCaP). The primary localization was confirmed with several markers, by use of three different genetic models. We obtained a maximum two-point LOD score of 2.7 with marker D1S2785. Multipoint parametric and NPL analysis yielded maximum HLOD and NPL scores of 2.2 and 3.1, respectively, with an associated P value of . 001. Homogeneity analysis with multipoint LOD scores gave an estimate of the proportion of families with linkage to this locus of 50%, with a likelihood ratio of 157/1 in favor of heterogeneity. Furthermore, the 9/47 families with early-onset CaP at age <60 years gave multipoint LOD and NPL scores of 3.31 and 3.32, respectively, with P = .001.

Prostate carcinoma risk and allelic variants of genes involved in androgen biosynthesis and metabolism pathways

Ethnicity, when it is used to mean shared genetic inheritance within a group, has become one of the most important factors in determining prostate carcinoma risk. Genetic polymorphisms were hypothesized to be the probable explanation for differences in risk among ethnic groups. The authors evaluated the association between polymorphisms in genes involved in the androgen biosynthesis and metabolism pathway and the risk of prostate carcinoma.

PTEN/MMAC1/TEP1 involvement in primary prostate cancers

The PTEN/MMAC1/TEP1 gene, located at 10q23.3, is a tumor suppressor gene responsible for the familial cancer syndromes Cowden disease and Bannayan-Zonana syndrome, and is commonly somatically mutated in several types of cancers. Mutations of the PTEN gene have been found in prostate cancer cell lines and LOH at 10q22-24 in prostate tumors have also been described with a high frequency. To determine the role of this gene in prostate tumorigenesis, we therefore analysed 22 primary tumors for loss of heterozygosity (LOH) within the 10q22-23 region such that tumors hemizygous at those loci may be examined for somatic PTEN mutations. Losses of heterozygosity of at least one locus was found in 12 (55%) of the 22 tumors DNAs. Among these, six tumors exhibited allele loss in the interval between D10S1765 and D10S541 wherein lies the PTEN gene. We searched the entire coding region of PTEN for somatic mutations in these six tumors. One somatic mutation (17%), a 1 bp deletion, was detected in exon 7 of the gene, in one tumor, indicating that somatic mutations of the PTEN gene may occur in primary prostate tumors.

Quantification of expression of netrins, slits and their receptors in human prostate tumors

Recently, DCC (Deleted in Colorectal Cancer) protein has been forwarded as a receptor for netrin. The Netrin/DCC complex is critical for axon guidance and cell migration. In the developing nervous system, netrin protein secreted by midline cells attracts commissural axons by activating the DCC receptor on growth cones. This attraction can be switched to repulsion or silenced completely, depending on the DCC binding partner. The potential suppressor function of DCC in prostate tumorigenesis, through a still unknown mechanism, prompted us to quantify the expression of several genes involved in this axon guidance pathway. The relative expression levels of DCC, NEO1, NTN1, NTN2L, NTN4, UNC5C, Slit1, Slit2, Slit3, Robo1 and Robo2 were simultaneous quantified in 48 tumors and 7 normal prostate tissues by using real‐time quantitative reverse transcriptase‐polymerase chain reaction (RT‐PCR). A reduction in DCC, NEO1, NTN1 and NTN4 expression was observed in prostate tumors, while many of the same prostate tumors over‐expressed either Slit genes or their receptors, Robo.

htert expression correlates with myc over-expression in human prostate cancer

Expression of the telomerase catalytic sub‐unit (htert) constitutes a key step in the development of human cancer. Although htert regulation is still unclear, several studies suggest that c‐myc may activate its expression. Prostate cancer is one of the most common malignancies among men in Western countries. Since de‐regulated expression of myc as well as telomerase activation may contribute to the pathogenicity of this cancer, we investigated this pathway in prostate tumorigenesis. For this purpose, myc‐ and htert‐mRNA expression was quantified in 33 sporadic prostate tumors using a real‐time quantitative PCR assay based on TaqMan methodology. myc over‐expression was observed in 19 (58%) of 33 tumors, whereas telomerase status evaluated by htert expression was observed in 22 (67%). There was no correlation between myc over‐expression or htert expression level and tumor stage or Gleason grade. A significant association (p = 0.0024) was found between myc over‐expression and elevated htert expression, indicating that the up‐regulation of telomerase activity often observed in prostate tumors might be conferred through transactivation of htert by myc. It is likely that the ability of c‐myc protein to stimulate expression of htert and thereby enhance telomerase activity represents an important step in prostate tumorigenesis. Int. J. Cancer (Pred. Oncol.) 89:172–176, 2000.

PCAP is the major known prostate cancer predisposing locus in families from south and west Europe

To date four prostate cancer predisposing loci have been mapped: HPC1 (Hereditary Prostate Cancer 1) on 1q24-25, PCaP (Predisposing for Cancer Prostate) on 1q42.2-43, CAPB (Cancer Prostate and Brain) on 1p36, and HPCX on Xq27-28. We examined evidence for linkage to those loci in 64 families from south and west Europe. Genotyping of three (six for PCaP) markers encompassing the candidate regions were performed on 221 individuals including 159 affected patients. The resulting data were analysed using both parametric and non parametric linkage methods. No significant evidence of linkage to HPC1, CAPB, or HPCX was found either in the whole population or when pedigrees were stratified according to criteria specific to each locus. By contrast, results in favour of linkage to PCaP locus were observed with maximum multipoint NPL and HLOD scores of 2.8 (P = 0.0026) and 2.65 respectively. Homogeneity analysis performed with multipoint LOD scores gave an estimated proportion of families with linkage to this locus up to 50%. Particularly, families with an earlier age at diagnosis (⩽65-years-old) contributed significantly to the evidence of linkage with a maximum multipoint NPL score of 2.03 (P = 0.024). Those results suggest that PCaP is the most frequent known locus predisposing to hereditary prostate cancer cases from families from south and west Europe.

Loss of heterozygosity at chromosome arm 13q and RB1 status in human prostate cancer.

Aberrations of the long arm of chromosome 13 are common in prostate cancer and were initially attributed to alterations of the RB1 gene in band q14 of the chromosome. However, prostate tumors generally yield normal p110RB1 nuclear staining despite loss of heterozygosity (LOH) at the RB1 locus. Our previous analysis of chromosome arm 13q showed allelic loss in 41% of primary prostate tumors. To refine our knowledge of 13q, we extended our previous LOH study by using more polymorphic markers to analyze more prostate tumors. Sixty human prostate carcinomas were screened for allelic loss on 13q by using 13 13q-specific markers. LOH on the long arm of chromosome 13 was found in 39 (65%) of the 60 tumors. Furthermore, 33 of these 39 tumors had evidence of allelic loss involving a region of 13q14 containing RB1. Because immunohistochemical assessment of pRb expression is controversial in prostate tumors, we used a quantitative reverse transcription polymerase chain reaction (RT-PCR) method to determine whether RB1 is the target tumor suppressor gene in this region. RB1 mRNA steady-state levels were determined in 12 prostate tumors preselected on the basis of presumed deletion at the RB1 locus and four prostate tumors without LOH at the RB1 locus; five normal prostate specimens were used as controls. One of the 12 assessable prostate tumors with presumed LOH at RB1 showed a corresponding decreased in RB1 mRNA expression, whereas none of the four tumors without LOH at RB1 locus showed such a decrease. This study, based on another technical approach, confirms that RB1 is not the main target of the observed LOH at 13q14.3, and raises the possibility that another tumor suppressor gene in this region plays a key role in prostate cancer.

Extensive analysis of the 7q31 region in human prostate tumors supports TES as the best candidate tumor suppressor gene.

Loss of heterozygosity (LOH) on chromosome arm 7q31 is found in many prostate tumors. Such alterations are generally associated with inactivation of tumor suppressor genes. It has been shown previously that the main region of LOH at 7q31 spans the interval between the D7S486 and D7S2460 microsatellite loci, which contains several candidate tumor suppressor genes (TSG) such as TES, CAV2, CAV1, MET, CAPZA2, ST7 and WNT2. We tested 41 human sporadic prostate tumors for 7q31 LOH by using 5 polymorphic markers overlapping the critical region and used a real‐time reverse transcriptase‐polymerase chain reaction (RT‐PCR) assay to study the expression of the 7 candidate TSGs located in this genomic region. We found that CAV1, CAV2, MET and TES mRNA expression was lower in prostate tumors than in normal prostate tissues. Our immunohistochemical results and previously published data on the compartmental expression of these messenger RNAs in stromal and epithelial cells suggest that TES is the best candidate tumor suppressor gene at 7q31.

Association study of polymorphisms in the human estrogen receptor alpha gene and prostate cancer risk

OBJECTIVES Prostate cancer is a very common hormone-related malignancy in Western countries. It is initially dependent on androgen stimulation but in vitro growth of prostate cancer cells are also dependent on estrogen. Our goal was to elucidate if some polymorphisms of estrogen receptor alpha gene might be associated with the risk of prostate cancer. METHODS Using DHPLC techniques, each coding exon of the estrogen receptor alpha gene was screened for new polymorphisms in germline DNA from 96 healthy controls and 96 sporadic prostate cancer cases. Identified polymorphisms were then genotyped and their distribution compared between the two populations. RESULTS Thirteen polymorphisms were identified. A difference was found in the distribution of one newly identified polymorphism, namely a GGGA repeat located in the first intron of the gene. The common wild type genotype consisted of two alleles with five GGGA repetitions (5/5 genotype). Indeed this 5/5 genotype was found in 294/296 controls (99.3%) and 285/294 patients (96.9%; OR, 4.6; 95% CI, 0.99-21.67). Among the nine patients with a different genotype, one was 4/5, seven were 5/6 and one was 6/6. CONCLUSION These results suggest that variants of the GGGA polymorphism from the estrogen receptor alpha gene may be associated with an increased risk of developing prostate cancer.

Expression and mutational analysis of the MADR2/smad2 gene in human prostate cancer

Loss of heterozygosity (LOH) on chromosome arm 18q is common in sporadic prostate cancer and may be involved in cancer development through inactivation of tumor‐suppressor genes (TSG). Recent identification, at 18q21.1, of MADR2/Smad2, a key component in transforming growth factor β (TGFβ)‐family signaling pathways, led us to investigate the role of this gene in prostate tumorigenesis.