Hereditary prostate cancer in African American families: linkage analysis using markers that map to five candidate susceptibility loci

Review of prostate cancer genomic studies in Africa

Prostate cancer (PCa) is the second most commonly diagnosed in men worldwide and one of the most frequent cancers in men in Africa. The heterogeneity of this cancer fosters the need to identify potential genetic risk factors/biomarkers. Omics variations may significantly contribute to early diagnosis and personalized treatment. However, there are few genomic studies of this disease in African populations. This review sheds light on the status of genomics research on PCa in Africa and outlines the common variants identified thus far. The allele frequencies of the most significant SNPs in Afro-native, Afro-descendants, and European populations were compared. We advocate how these few but promising data will aid in understanding, better diagnosing, and precisely treating this cancer and the need for further collaborative research on the genomics of PCa in the African continent.

Role of Precision Oncology in Type II Endometrial and Prostate Cancers in the African Population: Global Cancer Genomics Disparities

Precision oncology can be defined as molecular profiling of tumors to identify targetable alterations. Emerging research reports the high mortality rates associated with type II endometrial cancer in black women and with prostate cancer in men of African ancestry. The lack of adequate genetic reference information from the African genome is one of the major obstacles in exploring the benefits of precision oncology in the African context. Whilst external factors such as the geography, environment, health-care access and socio-economic status may contribute greatly towards the disparities observed in type II endometrial and prostate cancers in black populations compared to Caucasians, the contribution of African ancestry to the contribution of genetics to the etiology of these cancers cannot be ignored. Non-coding RNAs (ncRNAs) continue to emerge as important regulators of gene expression and the key molecular pathways involved in tumorigenesis. Particular attention is focused on activated/repressed genes and associated pathways, while the redundant pathways (pathways that have the same outcome or activate the same downstream effectors) are often ignored. However, comprehensive evidence to understand the relationship between type II endometrial cancer, prostate cancer and African ancestry remains poorly understood. The sub-Saharan African (SSA) region has both the highest incidence and mortality of both type II endometrial and prostate cancers. Understanding how the entire transcriptomic landscape of these two reproductive cancers is regulated by ncRNAs in an African cohort may help elucidate the relationship between race and pathological disparities of these two diseases. This review focuses on global disparities in medicine, PCa and ECa. The role of precision oncology in PCa and ECa in the African population will also be discussed.

Prostate Cancer Genomics Research Disparities in Africa: Advancing Knowledge in Resource Constrained Settings

Prostate cancer disproportionately affects men of African descent and it is estimated that Africa will bear the highest disease burden in the next decade. Underlying genomic factors may contribute to prostate cancer disparities; however, it is unclear whether Africa has prioritised genomics research toward addressing these disparities. A Pubmed review was performed of publications spanning a 15-year period, with specific focus on prostate cancer genomics research that included samples from Africa and investigators in Africa. Data are presented on research publications from Africa relative to similar publications from different geographical regions, and more specifically, the extent of disparities and the contributions to prostate cancer knowledge as a result of genomics research that included African samples and African institutions. Limited publication output may reflect the infrastructure and funding challenges in Africa. Widespread cooperation should be fostered by sharing capacity and leveraging existing expertise to address the growing cancer burden facing the continent.

Genetic Contributions to Prostate Cancer Disparities in Men of West African Descent

Prostate cancer (PCa) is the second most frequently diagnosed malignancy and the second leading cause of death in men worldwide, after adjusting for age. According to the International Agency for Research on Cancer, continents such as North America and Europe report higher incidence of PCa; however, mortality rates are highest among men of African ancestry in the western, southern, and central regions of Africa and the Caribbean. The American Cancer Society reports, African Americans (AAs), in the United States, have a 1.7 increased incidence and 2.4 times higher mortality rate, compared to European American's (EAs). Hence, early population history in west Africa and the subsequent African Diaspora may play an important role in understanding the global disproportionate burden of PCa shared among Africans and other men of African descent. Nonetheless, disparities involved in diagnosis, treatment, and survival of PCa patients has also been correlated to socioeconomic status, education and access to healthcare. Although recent studies suggest equal PCa treatments yield equal outcomes among patients, data illuminates an unsettling reality of disparities in treatment and care in both, developed and developing countries, especially for men of African descent. Yet, even after adjusting for the effects of the aforementioned factors; racial disparities in mortality rates remain significant. This suggests that molecular and genomic factors may account for much of PCa disparities.

The Impact of African Ancestry on Prostate Cancer Disparities in the Era of Precision Medicine

Prostate cancer disproportionately affects men of African ancestry at nearly twice the rate of men of European ancestry despite the advancement of treatment strategies and prevention. In this review, we discuss the underlying causes of these disparities including genetics, environmental/behavioral, and social determinants of health while highlighting the implications and challenges that contribute to the stark underrepresentation of men of African ancestry in clinical trials and genetic research studies. Reducing prostate cancer disparities through the development of personalized medicine approaches based on genetics will require a holistic understanding of the complex interplay of non-genetic factors that disproportionately exacerbate the observed disparity between men of African and European ancestries.

Prostate Cancer Disparities by Race and Ethnicity: From Nucleotide to Neighborhood

Prostate cancer (CaP) incidence, morbidity, and mortality rates vary substantially by race and ethnicity, with African American men experiencing among the highest CaP rates in the world. The causes of these disparities are multifactorial and complex, and likely involve differences in access to screening and treatment, exposure to CaP risk factors, variation in genomic susceptibility, and other biological factors. To date, the proportion of CaP that can be explained by environmental exposures is small and differences in the role factors play by race or ethnicity is poorly understood. In the absence of additional data, it is likely that environmental factors do not contribute greatly to CaP disparities. In contrast, CaP has one of the highest heritabilities of all major cancers and many CaP susceptibility genes have been identified. Some CaP loci, including the risk loci found at chromosome 8q24, have consistent effects in all racial/ethnic groups studied to date. However, replication of many susceptibility loci across race or ethnicity remains limited. It is likely that inequities in health care access strongly influences CaP disparities. CaP is a disease with a complex multifactorial etiology, and therefore any approach attempting to address racial/ethnic disparities in CaP must consider the many sources that influence risk, outcomes, and disparities.

Prostate Cancer Genomics: Recent Advances and the Prevailing Underrepresentation from Racial and Ethnic Minorities

Prostate cancer (CaP) is the most commonly diagnosed non-cutaneous cancer and the second leading cause of male cancer deaths in the United States. Among African American (AA) men, CaP is the most prevalent malignancy, with disproportionately higher incidence and mortality rates. Even after discounting the influence of socioeconomic factors, the effect of molecular and genetic factors on racial disparity of CaP is evident. Earlier studies on the molecular basis for CaP disparity have focused on the influence of heritable mutations and single-nucleotide polymorphisms (SNPs). Most CaP susceptibility alleles identified based on genome-wide association studies (GWAS) were common, low-penetrance variants. Germline CaP-associated mutations that are highly penetrant, such as those found in HOXB13 and BRCA2, are usually rare. More recently, genomic studies enabled by Next-Gen Sequencing (NGS) technologies have focused on the identification of somatic mutations that contribute to CaP tumorigenesis. These studies confirmed the high prevalence of ERG gene fusions and PTEN deletions among Caucasian Americans and identified novel somatic alterations in SPOP and FOXA1 genes in early stages of CaP. Individuals with African ancestry and other minorities are often underrepresented in these large-scale genomic studies, which are performed primarily using tumors from men of European ancestry. The insufficient number of specimens from AA men and other minority populations, together with the heterogeneity in the molecular etiology of CaP across populations, challenge the generalizability of findings from these projects. Efforts to close this gap by sequencing larger numbers of tumor specimens from more diverse populations, although still at an early stage, have discovered distinct genomic alterations. These research findings can have a direct impact on the diagnosis of CaP, the stratification of patients for treatment, and can help to address the disparity in incidence and mortality of CaP. This review examines the progress of understanding in CaP genetics and genomics and highlight the need to increase the representation from minority populations.

Molecular mechanisms involving prostate cancer racial disparity

Prostate cancer (PCa) is the second leading cause of cancer-related deaths in the United States. The African (AA) descent has greater incidence and mortality rates of PCa as compared to Caucasian (CA) men. While socioeconomic differences across racial groups contribute to disparity in PCa, increasing evidence points that genetic and molecular alterations play important roles in racial disparities associated with PCa. In this review, we focus on genetic and molecular influences that contribute to racial disparity between AA and CA men including: androgen and estrogen receptor signaling pathways, growth factors, apoptotic proteins, genetic, genomic and epigenetic alterations. Future translational studies will identify prognostic and predictive biomarkers for AA PCa and assist in the development of new targeted-therapies specifically for AA men with PCa.

Prostate Cancer Genetics: Variation by Race, Ethnicity, and Geography

Prostate cancer rates vary substantially by race, ethnicity, and geography. These disparities can be explained by variation in access to screening and treatment, variation in exposure to prostate cancer risk factors, and variation in the underlying biology of prostate carcinogenesis (including genomic propensity of some groups to develop biologically aggressive disease). It is clear that access to screening and access to treatment are critical influencing factors of prostate cancer rates; yet, even among geographically diverse populations with similar access to care (eg, low- and medium-income countries), African descent men have higher prostate cancer rates and poorer prognosis. To date, the proportion of prostate cancer that can be explained by environmental exposures is small, and the effect of these factors across different racial, ethnic, or geographical populations is poorly understood. In contrast, prostate cancer has one of the highest heritabilities of all major cancers. Numerous genetic susceptibility markers have been identified from family-based studies, candidate gene association studies, and genome-wide association studies. Some prostate cancer loci, including the risk loci found at chromosome 8q24, have consistent effects in all groups studied to date. However, replication of many susceptibility loci across race, ethnicity, and geography remains limited, and additional studies in certain populations (particularly in men of African descent) are needed to better understand the underlying genetic basis of prostate cancer.

Molecular basis for prostate cancer racial disparities

Prostate cancer (PCa) remains the most common cancer in American men. African-American (AA) men continue to have higher PCa prevalence and mortality rates compared to men in other populations. In addition to socioeconomic factors and lifestyle differences, molecular alterations contribute to this discrepancy. We summarize molecular genetics research results interrelated with the biology of PCa racial disparity. Androgen and androgen receptor (AR) pathways have long been associated with prostate growth. Racial differences have also been found among variants of genes of the enzymes involved in androgen biosynthesis and metabolism. Growth factors and their receptors are a potential cause of the disparity in PCa. Recent molecular and biotechnological approaches in the field of proteomics and genomics will greatly aid the advancement of translational research on racial disparity in PCa, which may help, in finding new prognostic markers and novel therapeutic approaches for the treatment of PCa in AA.

Clinical Correlates of Autosomal Chromosomal Abnormalities in an Electronic Medical Record-Linked Genome-Wide Association Study: A Case Series

Although mosaic autosomal chromosomal abnormalities are being increasingly detected as part of high-density genotyping studies, the clinical correlates are unclear. From an electronic medical record (EMR)–based genome-wide association study (GWAS) of peripheral arterial disease, log-R-ratio and B-allele-frequency data were used to identify mosaic autosomal chromosomal abnormalities including copy number variation and loss of heterozygosity. The EMRs of patients with chromosomal abnormalities and those without chromosomal abnormalities were reviewed to compare clinical characteristics. Among 3336 study participants, 0.75% (n = 25, mean age = 74.8 ± 10.7 years, 64% men) had abnormal intensity plots indicative of autosomal chromosomal abnormalities. A hematologic malignancy was present in 8 patients (32%), of whom 4 also had a solid organ malignancy while 2 patients had a solid organ malignancy only. In 50 age- and sex-matched participants without chromosomal abnormalities, there was a lower rate of hematologic malignancies (2% vs 32%, P < .001) but not solid organ malignancies (20% vs 24%, P = .69). We also report the clinical characteristics of each patient with the observed chromosomal abnormalities. Interestingly, among 5 patients with 20q deletions, 4 had a myeloproliferative disorder while all 3 men in this group had prostate cancer. In summary, in a GWAS of 3336 adults, 0.75% had autosomal chromosomal abnormalities and nearly a third of them had hematologic malignancies. A potential novel association between 20q deletions, myeloproliferative disorders, and prostate cancer was also noted.

Clinical Correlates of Autosomal Chromosomal Abnormalities in an Electronic Medical Record-Linked Genome-Wide Association Study: A Case Series

Although mosaic autosomal chromosomal abnormalities are being increasingly detected as part of high-density genotyping studies, the clinical correlates are unclear. From an electronic medical record (EMR)-based genome-wide association study (GWAS) of peripheral arterial disease, log-R-ratio and B-allele-frequency data were used to identify mosaic autosomal chromosomal abnormalities including copy number variation and loss of heterozygosity. The EMRs of patients with chromosomal abnormalities and those without chromosomal abnormalities were reviewed to compare clinical characteristics. Among 3336 study participants, 0.75% (n = 25, mean age = 74.8 ± 10.7 years, 64% men) had abnormal intensity plots indicative of autosomal chromosomal abnormalities. A hematologic malignancy was present in 8 patients (32%), of whom 4 also had a solid organ malignancy while 2 patients had a solid organ malignancy only. In 50 age- and sex-matched participants without chromosomal abnormalities, there was a lower rate of hematologic malignancies (2% vs 32%, P < .001) but not solid organ malignancies (20% vs 24%, P = .69). We also report the clinical characteristics of each patient with the observed chromosomal abnormalities. Interestingly, among 5 patients with 20q deletions, 4 had a myeloproliferative disorder while all 3 men in this group had prostate cancer. In summary, in a GWAS of 3336 adults, 0.75% had autosomal chromosomal abnormalities and nearly a third of them had hematologic malignancies. A potential novel association between 20q deletions, myeloproliferative disorders, and prostate cancer was also noted.

Exclusion of the 750-kb genetically unstable region at Xq27 as a candidate locus for prostate malignancy in HPCX1-linked families

Several linkage studies provided evidence for the presence of the hereditary prostate cancer locus, HPCX1, at Xq27-q28. The strongest linkage peak of prostate cancer overlies a variable region of ~750 kb at Xq27 enriched by segmental duplications (SDs), suggesting that the predisposition to prostate cancer may be a genomic disorder caused by recombinational interaction between SDs. The large size of SDs and their sequence similarity make it difficult to examine this region for possible rearrangements using standard methods. To overcome this problem, direct isolation of a set of genomic segments by in vivo recombination in yeast (a TAR cloning technique) was used to perform a mutational analysis of the 750 kb region in X-linked families. We did not detect disease-specific rearrangements within this region. In addition, transcriptome and computational analyses were performed to search for nonannotated genes within the Xq27 region, which may be associated with genetic predisposition to prostate cancer. Two candidate genes were identified, one of which is a novel gene termed SPANXL that represents a highly diverged member of the SPANX gene family, and the previously described CDR1 gene that is expressed at a high level in both normal and malignant prostate cells, and mapped 210 kb of upstream the SPANX gene cluster. No disease-specific alterations were identified in these genes. Our results exclude the 750-kb genetically unstable region at Xq27 as a candidate locus for prostate malignancy. Adjacent regions appear to be the most likely candidates to identify the elusive HPCX1 locus.

Androgen receptor molecular biology and potential targets in prostate cancer

The androgen receptor (AR) is a key transcriptional regulator and therapeutic target in prostate cancer. During androgen deprivation therapy to treat metastatic prostate cancer, surviving cells acquire increased AR signaling through a variety of mechanisms, one of which is enhanced interactions with AR coactivators. One recently identified AR-specific coregulator expressed only in human and nonhuman primates is the melanoma antigen gene protein-A11 (MAGE-11). MAGE-11 increases AR transcriptional activity through direct interactions with AR and other coactivators, and its levels increase during prostate cancer progression to castration-recurrent growth. The MAGE-11 gene is located at Xq28 on the human X chromosome as part of an X-linked MAGE gene family of cancer-testis antigens. MAGE-11 stabilizes AR when androgen levels are low, and functions in a transcriptional hub to promote AR-mediated gene activation. The evolutionary development and organization of the MAGE-11 gene within the cancer-testis antigen family suggests that MAGE-11 provides a gain-of-function to AR among primates in both normal physiology and cancer, and may serve as a therapeutic target in the treatment of advanced prostate cancer.

Contribution of HPC1 (RNASEL) and HPCX variants to prostate cancer in a founder population

BACKGROUND

Prostate cancer is a genetically complex disease with locus and disease heterogeneity. The RNASEL gene and HPCX locus have been implicated in hereditary prostate cancer; however, their contributions to sporadic forms of this malignancy remain uncertain.

METHODS

Associations of prostate cancer with two variants in the RNASEL gene (a founder mutation, 471delAAAG, and a non-synonymous SNP, rs486907), and with five microsatellite markers in the HPCX locus, were examined in 979 cases and 1,251 controls of Ashkenazi Jewish descent. Odds ratios (ORs) and 95% confidence intervals (CIs) were estimated using logistic regression models.

RESULTS

There was an inverse association between RNASEL rs486907 and prostate cancer in younger men (<65 years) and those with a first-degree relative with prostate cancer; men with AA genotype had ORs of 0.64 and 0.47 (both P < 0.05), respectively, in comparison to men with GG genotype. Within the HPCX region, there were positive associations for allele 135 of bG82i1.1 marker (OR = 1.77, P = 0.01) and allele 188 of DXS1205 (OR = 1.65, P = 0.02). In addition, allele 248 of marker D33 was inversely associated (OR = 0.65, P = 0.05) with Gleason score ≥7 tumors.

CONCLUSIONS

Results suggest that variants in RNASEL contribute to susceptibility to early onset and familial forms of prostate cancer, whereas HPCX variants are associated with prostate cancer risk and tumor aggressiveness. The observation that a mutation predicted to completely inactivate RNASEL protein was not associated with prostate cancer, but that a missense variant was associated, suggests that the effect is due to either partial inactivation of the protein, and/or acquisition of a new protein activity.

X-linked tumor suppressors: perplexing inheritance, a unique therapeutic opportunity

Unlike autosomal genes, the majority of X-linked genes are subject to dosage compensation. As a result, female tissues comprise cells exclusively expressing X-linked genes from one or other parent. The implication of having only one allele of active X-linked genes in cancer pathogenesis, i.e. somatic single-hit inactivation and dominant inheritance, has not been extensively explored. Recent studies have identified FOXP3 and WTX as two X-linked tumor suppressor genes that are somatically inactivated by single genetic hits. Because the predicted dominant inheritance of cancer risk has not been demonstrated in humans, we will discuss the possible conditions that might prevent such dominant inheritance. We also argue that the existence of a genetically intact allele in cancer cells in women, together with apparent abnormal X inactivation in cancer cells, might provide an opportunity to selectively reactivate tumor suppressor genes for cancer therapy.

Molecular mechanisms involving prostate cancer racial disparity

African American (AA) men with prostate cancer (PCa) have worse disease, with a higher incidence, younger age and more advanced disease at diagnosis, and a worse prognosis, compared to Caucasian (CA) men. In addition to socioeconomic factors and lifestyle differences, molecular alterations contribute to this discrepancy. In this review, we summarize molecular genetics research results interrelated with the biology of PCa racial disparity. Androgen and androgen receptor (AR) pathways have long been associated with prostate growth. Racial differences have also been found among variants of the genes of the enzymes involved in androgen biosynthesis and metabolism, such as SRD5A2, CYP17, and CYP3A4. The levels of expression and CAG repeat length of AR also show racial divergence and may be critical molecular alterations for racial disparity. Growth factors and their receptors, which promote cancer cell growth, are another potential cause of the disparity; both EGFR and EPHB2, two of the most studied receptors, show interethnic differences. Differences have also been found among genes regulating cell apoptosis, such as BCL2, which is increased in PCa in the AA population. Recent developments in genetics, proteomics, and genomics, among other molecular biotechnologies, will greatly aid the advancement of translational research on PCa racial disparity, hopefully culminating in the discovery of novel mechanisms of disease, in addition to prognostic markers and novel therapeutic approaches.

A haplotype at chromosome Xq27.2 confers susceptibility to prostate cancer

We conducted an association study to identify risk variants for familial prostate cancer within the HPCX locus at Xq27 among Americans of Northern European descent. We investigated a total of 507 familial prostate cancer probands and 507 age-matched controls without a personal or family history of prostate cancer. The study population was subdivided into a set of training subjects to explore genetic variation of the locus potentially impacting risk of prostate cancer, and an independent set of test subjects to confirm the association and to assign significance, addressing multiple comparisons. We identified a 22.9 kb haplotype nominally associated with prostate cancer among training subjects (292 cases, 292 controls; chi(2) = 5.08, P = 0.020), that was confirmed among test subjects (215 cases, 215 controls; chi(2) = 3.73, P = 0.040). The haplotype predisposed to prostate cancer with an odds ratio of 3.41 (95% CI 1.04-11.17, P = 0.034) among test subjects. The haplotype extending from rs5907859 to rs1493189 is concordant with a prior study of the region within the Finnish founder population, and warrants further independent investigation.

Recruitment strategies and comparison of prostate cancer-specific clinical data on African-American and Caucasian males with and without family history

Prostate cancer is the most common cancer in men in the United States. This is a complex disease with high heterogeneity and the exact causes are unknown in population-specific samples. Family history is a primary risk factor irrespective of race. Identifying prostate cancer families with multiple affected cancer cases is challenging. Herein we document recruitment techniques and present prostate cancer clinical factors described in a cohort of African Americans and Caucasians with or without a strong family history. A total of 521 prostate cancer patients (241 African Americans and 280 Caucasians) were identified using a novel cooperative methodology involving a combination of treating physicians and tumor registries. Higher prostate-specific antigen (PSA, P=0.0269) was found in familial cases as compared to sporadic cases in African-American men. In addition, PSA values for familial cases were higher (P=0.0093) in African-American as compared to Caucasian men. No differences were detected in Gleason score values in either race, regardless of family history. These findings remained the same after adjustment was made for age at diagnosis. In conclusion, methodologies for cohort acquisition, and clinical characteristics, are described for men with and without a family history of prostate cancer using both Caucasian and African-American populations.

Constitutional polymorphisms of prostate cancer: prognostic and diagnostic implications

Prostate cancer is the most common cancer diagnosis in men. While often perceived as a slow, indolent malignancy, prostate cancer trails only lung cancer among cancer-related mortality in men. Current diagnosis and treatment algorithms are plagued by overdiagnosis of non-lethal indolent prostate cancer with no proven means to predict, detect, and prevent aggressive lethal prostate cancer in men most at risk. These challenges are particularly concerning for African-American men who demonstrate increased rates of prostate cancer incidence and mortality when compared to other ethnic groups. With the completion of the human genome project, technology and techniques now exist to differentiate cancer from normal tissues based on the expression patterns of thousands of genes assessed simultaneously on a single microarray gene 'chip'. This platform has greatly improved our understanding of genes that regulate tumor behavior once cancer is established. Microarrays can also be utilized in patients without cancer to determine which patients are at high risk for tumor development and in need of rational prevention strategies. Constitutional single nucleotide polymorphisms (SNPs) are one source of genetic variation and may serve as a means to identify these high-risk individuals. SNPs are single nucleotide base pair changes within a gene which occur in one percent or more of the population. SNPs can contribute to a disease state by altering the function of a protein encoded by a gene without affecting gene expression. This review will examine the current understanding of constitutional SNPs associated with prostate cancer carcinogenesis, highlight two current diagnostic array platforms and discuss implications for future prevention and screening programs.

Mutational analysis of SPANX genes in families with X-linked prostate cancer

BACKGROUND

Previous genetic linkage studies identified a locus for susceptibility to prostate cancer called HPCX at Xq27. The candidate region contains two clusters of SPANX genes. The first cluster called SPANX-A/D includes SPANX-A1, SPANX-A2, SPANX-B, SPANX-C, and SPANX-D; the second cluster called SPANX-N includes SPANX-N1, SPANX-N2, SPANX-N3, and SPANX-N4. The SPANX genes encode cancer-testis (CT) specific antigens. Previous studies identified SPANX-B and SPANX-D variants produced by gene conversion events, none of which are associated with X-linked prostate cancer.

METHODS

In this study we applied transformation-associated recombination cloning (TAR) in yeast to analyze sequence variations in SPANX-A1, SPANX-A2, and SPANX-C genes that are resided within large chromosomal duplications. A SPANX-N1/N4 cluster was analyzed by a routine PCR analysis.

RESULTS

None of the sequence variations in the coding regions of these genes is associated with susceptibility to prostate cancer.

CONCLUSIONS

Therefore, genetic variation in the SPANX genes is not the actual target variants explaining HPCX. However, it is possible that they play a modifying role in susceptibility to prostate cancer through complex recombinational interaction.

Genome-wide linkage of 77 families from the African American Hereditary Prostate Cancer study (AAHPC)

BACKGROUND

The African American Hereditary Prostate Cancer (AAHPC) Study was designed to recruit families with early-onset disease fulfilling criteria of >or=4 affected.

METHODS

We present a approximately 10 cM genome-wide linkage (GWL) analysis on 77 families including 254 affected and 274 unaffected genotyped.

RESULTS

Linkage analysis revealed three chromosomal regions with GENEHUNTER multipoint HLOD scores >or=1.3 for all 77 families at 11q22, 17p11, and Xq21. One family yielded genome-wide significant evidence of linkage (LOD = 3.5) to the 17p11 region with seven other families >or=2.3 in this region. Twenty-nine families with no-male-to-male (MM) transmission gave a peak HLOD of 1.62 (alpha = 0.33) at the Xq21 locus. Two novel peaks >or=0.91 for the 16 families with '>6 affected' occurred at 2p21 and 22q12.

CONCLUSIONS

These chromosomal regions in the genome warrant further follow-up based on the hypothesis of multiple susceptibility genes with modest effects, or several major genes segregating in small subsets of families.

Molecular biology of prostate-cancer pathogenesis

PURPOSE OF REVIEW

The genetic and molecular basis of prostate-cancer pathogenesis is reviewed.

RECENT FINDINGS

Several genetic loci have been found that are associated with hereditary predisposition to prostate cancer, but they account for a small fraction of all cases. A number of suppressor genes have been identified that are activated by either complete or partial genetic loss in sporadic prostate cancer. Chromosomal translocation results in transcriptional activation of truncated ETS transcription factors ERG and ETV1, the first candidates for dominant oncogenes for prostate cancer. Lastly, the androgen receptor is active throughout the course of prostate cancer and, in androgen-independent prostate cancer, takes on the role of a dominant oncogene as the target of gene amplification, overexpression, and the activation of mutations.

SUMMARY

Genetic lesions responsible for familial and sporadic prostate cancer are being revealed and they suggest that prostate cancer often initiates owing to an increased susceptibility to oxidative damage; it then progresses by affecting transcription factors, the PI3 kinase pathway, and other growth stimulatory pathways. The final common pathway after androgen ablation appears to be activation of androgen receptor.

The genetics of the amyloidoses: interactions with immunity and inflammation

Historically, the amyloidoses have been associated with inflammation and the immune response. From Virchow's original description in human pathologic inflammatory states through their identification in horses used to produce antitoxin to their frequent occurrence in the course of multiple myeloma and a somewhat abortive designation as 'gammaloid', the disorders were felt to have an inflammatory origin. These presumptive associations antedated the availability of a reliable method for tissue extraction that would allow chemical analysis of the major deposited molecules. With the identification of the multiple precursors and the realization that most were not intrinsic elements of immune/inflammatory pathways, the investigative emphasis shifted to the analysis of the biophysical events involved in aggregation and fibril formation. As more in vivo models and better tools for examination of tissues have become available, it appears as if inflammation may participate as both a response to, and an amplifier of, the effects of the fibrillar aggregates. Hence, while only a limited number of amyloid protein precursors are involved in immunity and inflammation per se, host defense, in its broadest sense, is likely to be involved in the clinically relevant amyloidoses. Further it now appears that harnessing the immune response in an appropriate fashion may be able to play a role in treatment.

A common nonsense mutation in EphB2 is associated with prostate cancer risk in African American men with a positive family history

BACKGROUND

The EphB2 gene was recently implicated as a prostate cancer (PC) tumour suppressor gene, with somatic inactivating mutations occurring in approximately 10% of sporadic tumours. We evaluated the contribution of EphB2 to inherited PC susceptibility in African Americans (AA) by screening the gene for germline polymorphisms.

METHODS

Direct sequencing of the coding region of EphB2 was performed on 72 probands from the African American Hereditary Prostate Cancer Study (AAHPC). A case-control association analysis was then carried out using the AAHPC probands and an additional 183 cases of sporadic PC compared with 329 healthy AA male controls. In addition, we performed an ancestry adjusted association study where we adjusted for individual ancestry among all subjects, in order to rule out a spurious association due to population stratification.

RESULTS

Ten coding sequence variants were identified, including the K1019X (3055A-->T) nonsense mutation which was present in 15.3% of the AAHPC probands but only 1.7% of 231 European American (EA) control samples. We observed that the 3055A-->T mutation significantly increased risk for prostate cancer over twofold (Fisher's two sided test, p = 0.003). The T allele was significantly more common among AAHPC probands (15.3%) than among healthy AA male controls (5.2%) (odds ratio 3.31; 95% confidence interval 1.5 to 7.4; p = 0.008). The ancestry adjusted analyses confirmed the association.

CONCLUSIONS

Our data show that the K1019X mutation in the EphB2 gene differs in frequency between AA and EA, is associated with increased risk for PC in AA men with a positive family history, and may be an important genetic risk factor for prostate cancer in AA.

Dynamic structure of the SPANX gene cluster mapped to the prostate cancer susceptibility locus HPCX at Xq27

Genetic linkage studies indicate that germline variations in a gene or genes on chromosome Xq27-28 are implicated in prostate carcinogenesis. The linkage peak of prostate cancer overlies a region of approximately 750 kb containing five SPANX genes (SPANX-A1, -A2, -B, -C, and -D) encoding sperm proteins associated with the nucleus; their expression was also detected in a variety of cancers. SPANX genes are >95% identical and reside within large segmental duplications (SDs) with a high level of similarity, which confounds mutational analysis of this gene family by routine PCR methods. In this work, we applied transformation-associated recombination cloning (TAR) in yeast to characterize individual SPANX genes from prostate cancer patients showing linkage to Xq27-28 and unaffected controls. Analysis of genomic TAR clones revealed a dynamic nature of the replicated region of linkage. Both frequent gene deletion/duplication and homology-based sequence transfer events were identified within the region and were presumably caused by recombinational interactions between SDs harboring the SPANX genes. These interactions contribute to diversity of the SPANX coding regions in humans. We speculate that the predisposition to prostate cancer in X-linked families is an example of a genomic disease caused by a specific architecture of the SPANX gene cluster.