Familial associations between cancer sites

Significant evidence for a heritable contribution to cancer predisposition: a review of cancer familiality by site

BACKGROUND/AIMS

Sound and rigorous well-established, and newly extended, methods for genetic epidemiological analysis were used to analyze population evidence for genetic contributions to risk for numerous common cancer sites in Utah. The Utah Population Database (UPDB) has provided important illumination of the familial contribution to cancer risk by cancer site.

METHODS

With over 15 years of new cancer data since the previous comprehensive familial cancer analysis, we tested for excess familial clustering using an expanded Genealogical Index of Familiality (dGIF) methodology that provides for a more informative, but conservative test for the existence of a genetic contribution to familial relatedness in cancer.

RESULTS

Some new cancer sites have been analyzed for the first time, having achieved sufficiently large sample size with additions to the UPDB. This new analysis has identified 6 cancer sites with significant evidence for a heritable contribution to risk, including lip, chronic lymphocytic leukemia, thyroid, lung, prostate, and melanoma.

CONCLUSIONS

Both environmentally and genetically-based familial clustering have clinical significance, and these results support increased surveillance for cancer of the same sites among close relatives of affected individuals for many more cancers than are typically considered.

Most lung and colon cancer susceptibility genes are pair-wise linked in mice, humans and rats

Genetic predisposition controlled by susceptibility quantitative trait loci (QTLs) contributes to a large proportion of common cancers. Studies of genetics of cancer susceptibility, however, did not address systematically the relationship between susceptibility to cancers in different organs. We present five sets of data on genetic architecture of colon and lung cancer susceptibility in mice, humans and rats. They collectively show that the majority of genes for colon and lung cancer susceptibility are linked pair-wise and are likely identical or related. Four CcS/Dem recombinant congenic strains, each differing from strain BALB/cHeA by a different small random subset of ±12.5% of genes received from strain STS/A, suggestively show either extreme susceptibility or extreme resistance for both colon and lung tumors, which is unlikely if the two tumors were controlled by independent susceptibility genes. Indeed, susceptibility to lung cancer (Sluc) loci underlying the extreme susceptibility or resistance of such CcS/Dem strains, mapped in 226 (CcS-10×CcS-19)F2 mice, co-localize with susceptibility to colon cancer (Scc) loci. Analysis of additional Sluc loci that were mapped in OcB/Dem strains and Scc loci in CcS/Dem strains, respectively, shows their widespread pair-wise co-localization (P = 0.0036). Finally, the majority of published human and rat colon cancer susceptibility genes map to chromosomal regions homologous to mouse Sluc loci. 12/12 mouse Scc loci, 9/11 human and 5/7 rat colon cancer susceptibility loci are close to a Sluc locus or its homologous site, forming 21 clusters of lung and colon cancer susceptibility genes from one, two or three species. Our data shows that cancer susceptibility QTLs can have much broader biological effects than presently appreciated. It also demonstrates the power of mouse genetics to predict human susceptibility genes. Comparison of molecular mechanisms of susceptibility genes that are organ-specific and those with trans-organ effects can provide a new dimension in understanding individual cancer susceptibility.

Complex genotype sarcomas display familial inheritance independent of known cancer predisposition syndromes

BACKGROUND

The low incidence of sarcomas in the general population makes heritable contribution to disease risk difficult to discern beyond highly penetrant Mendelian syndromes.

METHODS

The Utah Cancer Registry (UCR) and Utah Population Database were interrogated for sarcoma diagnostic codes grouped by genetic type, either complex genotype/karyotype sarcoma or balanced translocation-associated sarcoma. The genealogic index of familiality (GIF) was calculated and relative risks (RR) of disease estimated for first-, second-, and third-degree relatives of sarcoma probands. Cancer patterns in pedigrees of sarcoma probands were examined to rule out known hereditary cancer syndromes.

RESULTS

A total of 229 balanced translocation type and 1,161 complex genotype type sarcomas with at least three generations of ancestral genealogy data were identified in the UCR. There was no evidence for excess relatedness for the balanced translocation group by using the GIF test (P = 0.657) and no significantly elevated RRs. In the complex genotype group, we observed significantly elevated GIF (P = 0.03). Modest RRs corroborated the GIF analysis, in which excess relatedness existed in distant relationships. No recognized cancer syndromes were identified among high-risk pedigrees.

DISCUSSION

We identified strong familiality among complex genotype sarcomas, independent from known cancer predisposition syndromes. In the absence of significantly elevated RRs for close relatives, the high GIF argues for a strong genetic-rather than environmental-component to complex genotype sarcoma risk. We observed no significant familial risk of developing balanced translocation-associated sarcomas, but the sample was small.

IMPACT

There exists yet to be deciphered heritable risk for developing complex genotype sarcomas.

A heritable predisposition to pituitary tumors

Pituitary tumors are prevalent in the general population, with a frequency of nearly 1 in 5. The cause of most pituitary tumors remains unknown, although a genetic contribution is recognized for some. We analyzed the Utah Population Data Base (UPDB), a resource combining a computerized genealogy of the Utah population with a statewide tumor registry, to investigate familial clustering of pituitary tumors. We analyzed the genetic relationships among 741 individuals diagnosed with benign or malignant pituitary tumors who had Utah genealogy data. To test for evidence of genetic contribution to predisposition, we compared average relatedness between all pairs of individuals with pituitary tumors with the expected relatedness in this population. We also estimated relative risks (RRs) for pituitary tumors in close and distant relatives of cases by comparing observed and expected numbers of cases among relatives. Relative risks for first- and third-degree relatives were significantly elevated (RR = 2.83 and 1.63, respectively), while relative risk for second-degree relatives was not significantly different from 1.0 (RR = 0.83). The average pairwise relatedness of pituitary tumor cases was significantly higher than expected, even when close relationships were ignored. The significantly elevated risks to relatives as well as the significant excess distant relatedness observed in cases provide strong support for a genetic contribution to predisposition to pituitary tumors. Multiple high-risk pedigrees can be identified in the UPDB, and study of such pedigrees might allow identification of the gene(s) responsible for our observations. Recognizing genetic contribution to the disease may also help with counseling family members of affected individuals.

Familiality in brain tumors

BACKGROUND

Familiality in brain tumors is not definitively substantiated.

METHODS

We used the Utah Population Data Base (UPDB), a genealogy representing the Utah pioneers and their descendants, record-linked to statewide cancer records, to describe the familial nature of primary brain cancer. We examined the familial clustering of primary brain tumors, including subgroups defined by histologic type and age at diagnosis. The UPDB includes 1,401 primary brain tumor cases defined as astrocytoma or glioblastoma, all with at least three generations of genealogy data. We tested the hypothesis of excess relatedness of brain tumor cases using the Genealogical Index of Familiality method. We estimated relative risks for brain tumors in relatives using rates of brain tumors estimated internally.

RESULTS

Significant excess relatedness was observed for astrocytomas and glioblastomas considered as a group (n = 1,401), for astrocytomas considered separately (n = 744), but not for glioblastomas considered separately (n = 658). Significantly increased risks to first- and second-degree relatives for astrocytomas were identified for relatives of astrocytomas considered separately. Significantly increased risks to first-degree relatives, but not second degree, were observed for astrocytoma and glioblastoma cases considered together, and for glioblastoma cases considered separately.

CONCLUSIONS

This study provides strong evidence for a familial contribution to primary brain cancer risk. There is evidence that this familial aspect includes not only shared environment, but also a heritable component. Extended high-risk brain tumor pedigrees identified in the UPDB may provide the opportunity to identify predisposition genes responsible for familial brain tumors.

Evidence for a heritable predisposition to death due to influenza

Animal model studies and human epidemiological studies have shown that some infectious diseases develop primarily in individuals with an inherited predisposition. A heritable contribution to the development of severe influenza virus infection (i.e., that which results in death) has not previously been hypothesized or tested. Evidence for a heritable contribution to death due to influenza was examined using a resource consisting of a genealogy of the Utah population linked to death certificates in Utah over a period of 100 years. The relative risks of death due to influenza were estimated for the relatives of 4,855 individuals who died of influenza. Both close and distant relatives of individuals who died of influenza were shown to have a significantly increased risk of dying of influenza, consistent with a combination of shared exposure and genetic effects. These data provide strong support for a heritable contribution to predisposition to death due to influenza.

A genealogical assessment of heritable predisposition to asthma mortality

RATIONALE

Asthma is a multifactorial disease; genetic factors have been suggested but have not been well defined.

OBJECTIVES

This study examined evidence for a heritable component to asthma mortality using a unique data resource consisting of Utah death certificates linked to a genealogy of Utah.

METHODS

Cases were defined as individuals whose death certificate listed asthma as a cause of death in a registry of all Utah deaths since 1904 (n = 1,553). The genealogical index of familiality analysis was used to compare the average relatedness of asthma deaths to the expected relatedness in the Utah population. Relative risks for asthma death in relatives of individuals who died of asthma are provided for close and distant relatives.

MEASUREMENTS AND MAIN RESULTS

The genealogical index of familiality identified a significantly higher average relatedness in cases (P < 0.001), even when close relationships were ignored. In addition, a significantly increased risk of dying of asthma was observed in first-degree relatives of cases (relative risk = 1.69, P < 0.001) and in second-degree relatives of cases (relative risk = 1.34, P = 0.003).

CONCLUSIONS

These results support a heritable contribution to asthma mortality.

Family based studies and genetic epidemiology: theory and practice

Family based studies have underpinned many successes in uncovering the causes of monogenic and oligogenic diseases. Now research is focussing on the identification and characterisation of genes underlying common diseases and it is widely accepted that these studies will require large population based samples. Population based family study designs have the potential to facilitate the analysis of the effects of both genes and environment. These types of studies integrate the population based approaches of classic epidemiology and the methods enabling the analysis of correlations between relatives sharing both genes and environment. The extent to which such studies are feasible will depend upon population- and disease-specific factors. To review this topic, a symposium was held to present and discuss the costs, requirements and advantages of population based family study designs. This article summarises the features of the meeting held at The University of Sheffield, August 2006.

Utah family-based analysis: past, present and future

A unique genealogical resource linked to phenotype data was created in Utah over 30 years ago. Here we review the history and content of this resource. In addition, we review three current methodologies used in conjunction with this resource to define the heritable contribution to phenotypes and to identify predisposition genes responsible for these phenotypes. Example analyses and high-risk pedigrees are presented. Finally we briefly review ways this resource, or others like it, may expand in future.

A population-based assessment of the familial component of chronic kidney disease mortality

BACKGROUND/AIM

While the familial nature of chronic kidney disease (CKD) has been recognized, it has primarily been defined from studies of first-degree relatives of selected sets of cases. The goal of this study is an evaluation of the familial clustering of end-stage renal disease (ESRD) and CKD mortality using a population-based genealogy of Utah. This is the first population-based analysis of the familial component of ESRD and non-ESRD CKD.

METHODS

We have defined two distinct patient groups for this analysis, using individuals with death certificates in the Utah Population Database indicating ESRD (n = 192) and non-ESRD CKD (n = 335) as the cause of death. Two measures of familiality were used: (1) relative risk (RR) of CKD or ESRD death in relatives of cases and (2) an average relatedness statistic, i.e., the Genealogical Index of Familiality.

RESULTS

The RR for dying with ESRD among the first-degree relatives of individuals dying with ESRD is estimated to be 10.1 (p = 0.0007, 95% confidence interval CI 2.76-25.95), but is not significantly elevated among second-degree relatives. The RR for dying with non-ESRD CKD among first- and second-degree relatives of individuals dying with non-ESRD CKD was 3.89 (p = 0.0051, 95% CI 1.43-8.46) and 3.11 (p = 0.04, 95% CI 0.85-7.95), respectively. The Genealogical Index of Familiality statistic demonstrated that the individuals dying with ESRD are significantly more related than expected in this population (p = 0.013); significant excess relatedness was also observed for individuals dying with non-ESRD CKD (p = 0.006), suggesting a familial component for both, with evidence for common environmental and genetic effects.

CONCLUSION

The results of this analysis of individuals dying with ESRD and non-ESRD CKD supports a significant and independent familial component to both conditions, suggesting a heritable factor playing a role.

Epidemiology informing clinical practice: from bills of mortality to population laboratories

The earliest observations on population patterns of disease and how they might inform medical practice probably occurred during the 17th century, and they continue to the present day, with increasing relevance to nutritional and infectious diseases, and cancer and other chronic diseases. Chronic-disease methods grew out of infectious-disease epidemiology, in which both field and laboratory methods are used. In diseases where intermediate biology was not initially observable (particularly cancer), record-based and interview-based epidemiology revealed some key exposures (e.g. smoking and radiation). With measurable intermediates (e.g. blood lipids), cardiovascular epidemiology also yielded inferences on causal pathways. Important changes that are remaking the field of epidemiology and will ultimately influence all aspects of medical practice include the following: high-throughput genotyping, allowing genetic and gene-environment causes of disease to be identified; high-throughput proteomics, which should allow the development of early-detection methods; new tools for the measurement of exposures; and a molecular basis for disease taxonomy. These new methods will allow a much better understanding of both the etiology and the intermediate stages of disease; however, new methods do not obviate the necessity for good study design, especially the need to be clear on the difference between observation and experiment. The greatest opportunities to inform medical practice come from the application of new methods to large-scale human observational studies, which include genetics, environment, early-detection markers, molecular classification of outcome, and treatment data. Improved molecular classification of disease will allow smaller, focused clinical trials to be undertaken and, ultimately, the tailoring of treatment to the biological profile of patient and disease.

Lobular breast cancer: excess familiality observed in the Utah Population Database

Family history of breast cancer (BC) is a strong predictor for developing female BC. Whether this excess familiality differs within morphological BC subgroups remains unclear. We assessed the risk of lobular breast cancer (LOB) and any BC among relatives of probands with LOB. We used the Utah Population Database (UPDB) to estimate familial relative risks (FRR) as well as average relatedness, using the genealogical index of familiality (GIF) statistic. The UPDB, a population-based resource, links genealogical data from over 2 million individuals to the Utah Cancer Registry. Consistent with other studies, analysis of all BC cases showed significantly increased risk of BC to relatives (first-degree relative [FDR]: FRR = 1.83, 95% confidence interval [CI] = 1.75-1.90). Morphology-specific risks showed that relatives of LOB probands had an increased risk of LOB (FDR: FRR = 4.51, 95% CI = 2.79-6.89) and an increased risk of any BC (FDR: FRR = 2.47, 95% CI = 2.12-2.85); both measures were significantly greater than the all BC FRR estimates, and surpassed even generalized early-onset BC risk. GIF analyses corroborated the FRR results and indicated that the excess relatedness of LOB cases extended to third-degree relatives. Our findings suggest that LOB has a heritable component and may represent a genetically homogeneous form of BC. Pedigrees with excess LOB may be useful in isolating additional BC predisposition genes. Relatives of women with LOB are at higher risk for BC than relatives of other BC subtypes; a more rigorous BC screening regime may be warranted for these individuals.

Population-based risk assessment for other cancers in relatives of hereditary prostate cancer (HPC) cases

BACKGROUND

To identify associations of other cancers with hereditary prostate cancer (HPC) we estimated relative risks (RRs) of 36 different cancers in relatives of prostate cancer cases in the Utah Population Data Base (UPDB), which combines genealogical and cancer data for Utah.

METHODS

We utilized known genetic relationships between prostate cancer cases and their relatives with cancer, combined with age- and sex-specific cancer rates calculated internally from the UPDB, to estimate RRs for cancer in relatives of prostate cancer cases.

RESULTS

Multiple other cancers were observed in excess in both first- and second-degree relatives of HPC cases including colon cancer, non-Hodgkins lymphoma, multiple myeloma, rectal cancer, cancer of the gallbladder, and melanoma (skin).

CONCLUSIONS

This analysis supports the existence of heritable prostate cancer syndromes that include other cancers. We hypothesize that the study of homogeneous pedigrees co-segregating prostate cancer and another cancer could allow more straightforward localization and identification of the gene(s) responsible.

A cohort study of cancer risk in relation to family histories of cancer in the Utah population database

BACKGROUND

It is well known that genetic variability affects the risk of many cancers, but details of the patterning of inherited cancer risk across different sites and age groups still are not well quantified.

METHODS

The authors conducted a nested case-control study of the familial risk of 40 cancers based on a cohort of 662,515 individuals from the Utah Population Database. From 1 to 10 controls selected from the cohort were matched individually on gender, birth year, and birthplace to each cancer case; and familial standardized incidence ratios (FSIR) were calculated for both cases and controls. Conditional logistic regression was used to estimate relative risks and population-attributable risks (PARs) of cancer in relation to FSIR. Relative risks of cancer in first-degree through fifth-degree relatives of cases, compared with controls, were calculated using the proportional hazards methods. All analyses were adjusted for spouse affection status and Latter Day Saints church affiliation.

RESULTS

Thirty-five of 40 cancers exhibited positive associations between risk and FSIR, and 21 of those associations were statistically significant. PAR estimates were strikingly high for prostate carcinoma (57%), breast carcinoma (39%), colon carcinoma (32%), lip carcinoma (31%), chronic lymphocytic leukemia (35%), and melanoma (32%). Both the proportion and the number of all cancers attributable to family history peaked at 32% in the group ages 65-84 years and remained high in the group age >/= 85 years.

CONCLUSIONS

A substantial portion of cancer risk was attributable to familial factors. The patterns of familial cancer recurrence among distant relatives suggested that simple genetic mechanisms may explain much of the familiality of cancer.

Cancer as a complex phenotype: pattern of cancer distribution within and beyond the nuclear family

BACKGROUND

The contribution of low-penetrant susceptibility variants to cancer is not clear. With the aim of searching for genetic factors that contribute to cancer at one or more sites in the body, we have analyzed familial aggregation of cancer in extended families based on all cancer cases diagnosed in Iceland over almost half a century.

METHODS AND FINDINGS

We have estimated risk ratios (RRs) of cancer for first- and up to fifth-degree relatives both within and between all types of cancers diagnosed in Iceland from 1955 to 2002 by linking patient information from the Icelandic Cancer Registry to an extensive genealogical database, containing all living Icelanders and most of their ancestors since the settlement of Iceland. We evaluated the significance of the familial clustering for each relationship separately, all relationships combined (first- to fifth-degree relatives) and for close (first- and second-degree) and distant (third- to fifth-degree) relatives. Most cancer sites demonstrate a significantly increased RR for the same cancer, beyond the nuclear family. Significantly increased familial clustering between different cancer sites is also documented in both close and distant relatives. Some of these associations have been suggested previously but others not.

CONCLUSION

We conclude that genetic factors are involved in the etiology of many cancers and that these factors are in some cases shared by different cancer sites. However, a significantly increased RR conferred upon mates of patients with cancer at some sites indicates that shared environment or nonrandom mating for certain risk factors also play a role in the familial clustering of cancer. Our results indicate that cancer is a complex, often non-site-specific disease for which increased risk extends beyond the nuclear family.