Role In Cancer Predisposition Research Articles

FANCJ DNA helicase is recruited to the replisome by AND-1 to ensure genome stability

FANCJ, a DNA helicase linked to Fanconi anemia and frequently mutated in cancers, counteracts replication stress by dismantling unconventional DNA secondary structures (such as G-quadruplexes) that occur at the DNA replication fork in certain sequence contexts. However, how FANCJ is recruited to the replisome is unknown. Here, we report that FANCJ directly binds to AND-1 (the vertebrate ortholog of budding yeast Ctf4), a homo-trimeric protein adaptor that connects the CDC45/MCM2-7/GINS replicative DNA helicase with DNA polymerase α and several other factors at DNA replication forks. The interaction between FANCJ and AND-1 requires the integrity of an evolutionarily conserved Ctf4-interacting protein (CIP) box located between the FANCJ helicase motifs IV and V. Disruption of the CIP box significantly reduces FANCJ association with the replisome, causing enhanced DNA damage, decreased replication fork recovery and fork asymmetry in cells unchallenged or treated with Pyridostatin, a G-quadruplex-binder, or Mitomycin C, a DNA inter-strand cross-linking agent. Cancer-relevant FANCJ CIP box variants display reduced AND-1-binding and enhanced DNA damage, a finding that suggests their potential role in cancer predisposition.

Association of the interleukin-10 (IL-10) gene polymorphisms with ovarian cancer risk: a systematic review and meta-analysis

Background. Ovarian cancer is a cancer with high fatality due to its symptomless nature which leads to late diagnosis. Therefore, there is an urgent need to discover genetic markers which are related to predisposition to the disease. With anti-inflammatory cytokines playing a major role in cancer predisposition, the present systematic review and meta-analysis was undertaken to evaluate the association of the interleukin-10 (IL-10) gene polymorphisms with ovarian cancer risk. Material and methods. Online databases were searched for articles dating from June 2023 until inception for studies assessing the frequencies of IL-10 polymorphisms in ovarian cancer patients and controls. The odds ratios of the genotypes alongside with their respective 95% confidence intervals were calculated under three different genetic models. Results. A total of 5 records studying the IL-10-819 C>T and IL-10-1082 G>A polymorphisms were included in the quantitative analysis. The meta-analysis suggested that the IL-10-819 C>T polymorphism was significantly associated the risk of ovarian cancer under a dominant (CT + TT vs CC) inheritance model (OR = 2.67; 95% CI = [1.17,6.12]; p = 0.02). Conclusions. The meta-analysis suggested that the T allele of the IL-10-819 C>T is associated with increased risk of ovarian cancer, but there is no statistically significant association between the IL-10-1082 G>A polymorphism and ovarian cancer. Future studies are required to further verify these results.

Therapy-Related Myeloid Neoplasms: Predisposition and Clonal Evolution.

Therapy-related Myeloid Neoplasm (t-MN) represents one of the worst long-term consequences of cytotoxic therapy for primary tumors and autoimmune disease. Poor survival and refractoriness to current treatment strategies characterize affected patients from a clinical point of view. In our aging societies, where newer therapies and ameliorated cancer management protocols are improving the life expectancy of cancer patients, therapy-related Myeloid Neoplasms are an emerging problem. Although several research groups have contributed to characterizing the main risk factors in t-MN development, the multiplicity of primary tumors, in association with the different therapeutic strategies available and the new drugs in development, make interpreting the current data still complex. The main risk factors involved in t-MN pathogenesis can be subgrouped into patient-specific, inherited, and acquired predispositions. Although t-MN can occur at any age, the risk tends to increase with advancing age, and older patients, characterized by a higher number of comorbidities, are more likely to develop the disease. Thanks to the availability of deep sequencing techniques, germline variants have been reported in 15-20% of t-MN patients, highlighting their role in cancer predisposition. It is becoming increasingly evident that t-MN with driver gene mutations may arise in the background of Clonal Hematopoiesis of Indeterminate Potential (CHIP) under the positive selective pressure of chemo and/or radiation therapies. Although CHIP is generally considered benign, it has been associated with an increased risk of t-MN. In this context, the phenomenon of clonal evolution may be described as a dynamic process of expansion of preexisting clones, with or without acquisition of additional genetic alterations, that, by favoring the proliferation of more aggressive and/or resistant clones, may play a crucial role in the progression from preleukemic states to t-MN.

The "extreme phenotype approach" applied to male breast cancer allows the identification of rare variants of ATR as potential breast cancer susceptibility alleles.

In oncogenetics, some patients could be considered as "extreme phenotypes", such as those with very early onset presentation or multiple primary malignancies, unusually high numbers of cancers of the same spectrum or rare cancer types in the same parental branch. For these cases, a genetic predisposition is very likely, but classical candidate gene panel analyses often and frustratingly remains negative. In the framework of the EX2TRICAN project, exploring unresolved extreme cancer phenotypes, we applied exome sequencing on rare familial cases with male breast cancer, identifying a novel pathogenic variant of ATR (p.Leu1808*). ATR has already been suspected as being a predisposing gene to breast cancer in women. We next identified 3 additional ATR variants in a cohort of both male and female with early onset and familial breast cancers (c.7762-2A>C; c.2078+1G>A; c.1A>G). Further molecular and cellular investigations showed impacts on transcripts for variants affecting splicing sites and reduction of ATR expression and phosphorylation of the ATR substrate CHEK1. This work further demonstrates the interest of an extended genetic analysis such as exome sequencing to identify very rare variants that can play a role in cancer predisposition in extreme phenotype cancer cases unexplained by classical cancer gene panels testing.

Impact on breast cancer susceptibility and clinicopathological traits of common genetic polymorphisms in TP53, MDM2 and ATM genes in Sardinian women.

Common variants of genes involved in DNA damage correction [tumor protein p53 (TP53), murine double 2 homolog oncoprotein (MDM2) and ataxia-telengiectasia mutated (ATM)] may serve a role in cancer predisposition. The purpose of the present study was to investigate the association of five variants in these genes with breast cancer risk and clinicopathological traits in a cohort of 261 women from northern Sardinia. Polymorphic variants in TP53 (rs17878362, rs1042522 and rs1625895), MDM2 (rs2279744) and ATM (rs1799757) were determined by PCR and TaqMan single nucleotide polymorphism assay in patients with breast cancer (n=136) and healthy controls (n=125). Association with clinicopathological (e.g., age at diagnosis, lymph node involvement, clinical stage) and lifestyle factors (e.g., smoking status, alcohol intake, contraceptive use) was also evaluated. TP53 rs17878362 and rs1625895 polymorphisms were associated with decreased risk of BC diagnosis in patients older than 50 years (codominant and recessive models) and post-menopause (recessive model). Furthermore, there was a significant association between lymph node status (positive vs. negative) and ATM rs1799757-delT in dominant and additive models and between MDM2 rs2279744-allele and use of oral contraceptives. This analysis suggested that TP53 rs17878362 and rs1625895 may affect age of onset of breast cancer and ATM rs1799757 and MDM2 rs2279744 may be associated with lymph node status and prolonged use of oral contraceptives, respectively.

Whole-Genome Profiles of Malay Colorectal Cancer Patients with Intact MMR Proteins.

Background: This study aimed to identify new genes associated with CRC in patients with normal mismatch repair (MMR) protein expression. Method: Whole-genome sequencing (WGS) was performed in seven early-age-onset Malay CRC patients. Potential germline genetic variants, including single-nucleotide variations and insertions and deletions (indels), were prioritized using functional and predictive algorithms. Results: An average of 3.2 million single-nucleotide variations (SNVs) and over 800 indels were identified. Three potential candidate variants in three genes—IFNE, PTCH2 and SEMA3D—which were predicted to affect protein function, were identified in three Malay CRC patients. In addition, 19 candidate genes—ANKDD1B, CENPM, CLDN5, MAGEB16, MAP3K14, MOB3C, MS4A12, MUC19, OR2L8, OR51Q1, OR51AR1, PDE4DIP, PKD1L3, PRIM2, PRM3, SEC22B, TPTE, USP29 and ZNF117—harbouring nonsense variants were prioritised. These genes are suggested to play a role in cancer predisposition and to be associated with cancer risk. Pathway enrichment analysis indicated significant enrichment in the olfactory signalling pathway. Conclusion: This study provides a new spectrum of insights into the potential genes, variants and pathways associated with CRC in Malay patients.

Abstract A36: Organoid models for deciphering roles of the evolving landscape of epigenetic heterogeneity during aging in cancer development

Abstract Background: Tumor initiation and development occur not necessarily by genetic changes alone, but in the context of the epigenome and cell microenvironment. Growing evidence indicate that cancer risk factors, such as aging and inflammation, may primarily modulate the epigenome, causing predisposition to cancer development by driver mutations. Thus, there is a need to study and model epigenetic changes preceding and associating with cancer development. We have developed ex vivo models for investigating the evolution and roles of DNA methylation changes during normal cell divisions and how these epigenetic changes play critical roles in early stages of tumor development. Results: We showed that spontaneous epigenetic changes, specifically promoter-DNA hypermethylation, have a very important role in tumor initiation by oncogenic driver mutations. We addressed the precursor role of aging-like spontaneous promoter-DNA hypermethylation in initiating tumorigenesis. Using mouse colon-derived organoids, we show promoter hypermethylation spontaneously arises in cells mimicking the human “aging-like” phenotype. The silenced genes activate the Wnt pathway, causing a stemlike state and differentiation defects. These changes render aged organoids profoundly more sensitive than young ones to transformation by BrafV600E producing the typical human proximal BRAFV600E-driven colon adenocarcinomas characterized by extensive, abnormal gene promoter CGI methylation or the methylator phenotype (CIMP). Conversely, CRISPR-mediated simultaneous inactivation of a panel of the silenced genes markedly sensitized to BrafV600E-induced transformation. We showed that “spontaneous” promoter hypermethylation, arising in an “aging-like” scenario, sufficiently affects genes with roles in negative regulation of Wnt pathway. Inactivation of these genes leads to increased stem cell state and defects in differentiation. Conclusion: Our studies tightly link aging-like epigenetic abnormalities to intestinal cell fate changes and predisposition to oncogene-driven colon tumorigenesis. The organoid-based model opens up an opportunity to study mechanisms underlying epigenetic heterogeneity arising during normal cellular processes and their role in cancer predisposition. Citation Format: Yong Tao, Byunghak Kang, Daniel Petkovich, Steve Baylin, Hariharan Easwaran. Organoid models for deciphering roles of the evolving landscape of epigenetic heterogeneity during aging in cancer development [abstract]. In: Proceedings of the AACR Special Conference on the Evolving Landscape of Cancer Modeling; 2020 Mar 2-5; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2020;80(11 Suppl):Abstract nr A36.

Genetic Polymorphisms of Glutathione S-Transferase and Risk of Acute Myeloid Leukemia: Case-Control Study and Meta-Analysis

Background: Acute myeloid leukemia (AML) is a complex disease that is linked to genetic and environmental factors. The gluthatione S-transferase (GST) is a family of enzymes that play a crucial role in the detoxification of carcinogens. These compounds could cause DNA damage, which might lead to the development of cancer. Interindividual inherited differences caused by the presence of single nucleotide polymorphisms (SNPs) in detoxification enzyme, could play a major role in cancer predisposition. The present study aimed to investigate the association between GST gene polymorphisms and AML risk. Methods: The GSTP1 genotype was determined by the PCR-RFLP and multiplex PCR for GSTT1 and GSTM1. Meta-analysis was conducted to evaluate the association between GST gene and the risk of AML. Results: We found that GSTT1 null genotype was significantly associated with the risk of AML. However, GSTM1 and GSTP1 polymorphisms did not influence the AML risk. Subjects carrying the GSTM1 Present, GSTT1 null and GSTP1 Ile / Val et Val /Val genotypes had a higher risk of developing AML. The results of meta-analysis showed a positive association between GSTM1 null, GSTT1 null and Ile105Val GSTP1 polymorphisms and AML risk in East Asians, Caucasians, and mixed populations, respectively. Conclusion: GST gene polymorphisms may be risk factors for acute myeloid leukemia.

Next generation sequencing of BRCA genes in glioblastoma multiform Egyptian patients: a pilot study

Background Germ line mutations of BRCA1 and BRCA2 were correlated with a variety of cancer Authors aimed to use next-generation sequencing (NGS) to detect BRCA1 and BRCA2 germ line mutations in glioblastoma multiform (GBM) Egyptian patients. Materials and methods Genomic DNA was extracted from six GBM cases, amplified using Ion AmpliSeq BRCA1 and BRCA2 panel. DNA libraries were pooled, barcoded and finally sequenced using Ion Torrent Personal Genome Machine sequencer. Results BRCA1 the previously reported rs1799966, rs1799950, rs16941 were found in five cases and they are in a linkage disequilibrium forming two distinct haplotypes, which might support their role in cancer predisposition. Out of the 18 reported variants in BRCA2, three denovo mutations were detected which leads to frame shift. Conclusion Further studies on large number of GBM patients and control cases to determine BRCA1 and BRCA2 germline mutations and haplotypes; diagnostic and prognostic role are encouraged.

Familial Cancer Variant Prioritization Pipeline version 2 (FCVPPv2) applied to a papillary thyroid cancer family

Whole-genome sequencing methods in familial cancer are useful to unravel rare clinically important cancer predisposing variants. Here, we present improvements in our pedigree-based familial cancer variant prioritization pipeline referred as FCVPPv2, including 12 tools for evaluating deleteriousness and 5 intolerance scores for missense variants. This pipeline is also capable of assessing non-coding regions by combining FANTOM5 data with sets of tools like Bedtools, ChromHMM, Miranda, SNPnexus and Targetscan. We tested this pipeline in a family with history of a papillary thyroid cancer. Only one variant causing an amino acid change G573R (dbSNP ID rs145736623, NM_019609.4:exon11:c.G1717A:p.G573R) in the carboxypeptidase gene CPXM1 survived our pipeline. This variant is located in a highly conserved region across vertebrates in the peptidase_M14 domain (Pfam ID PF00246). The CPXM1 gene may be involved in adipogenesis and extracellular matrix remodelling and it has been suggested to be a tumour suppressor in breast cancer. However, the presence of the variant in the ExAC database suggests it to be a rare polymorphism or a low-penetrance risk allele. Overall, our pipeline is a comprehensive approach for prediction of predisposing variants for high-risk cancer families, for which a functional characterization is a crucial step to confirm their role in cancer predisposition.

Abstract LB-232: Inherited determinants of early recurrent somatic mutations in prostate cancer

Abstract Background: Prostate cancer (PCa) is a clinically heterogeneous hormone regulated disease with a strong genetic component and characterized by distinct molecular subclasses. Since hormone levels and related transcription factors vary during individual’s lifetime, we hypothesized that inherited variants within regulatory elements of the human genome might act as facilitators of specific early somatic events in PCa in age/hormone dependent manner. Methods: We developed a computational approach to nominate heritable facilitators of somatic genomic events in the context of the Androgen Receptor (AR) signaling. Germline variants within functionally active regions of the genome (N=21,364) defined as per ENCODE data were ranked by the so called Trigger Score, which quantifies the fraction of the transcriptome putatively modulated by each variant leveraging individuals’ genotypes and transcript levels from a cohort of human benign prostate tissues. Results: We identified 300 polymorphic regulatory elements that associate with DNA repair and hormone regulated transcript levels. In a cohort of 539 PCa and more than 3,000 controls, a variant on 7p14.3 strongly associated with an early recurrent prostate cancer specific somatic mutation in the Speckle-Type POZ protein (SPOP) gene (OR=5.54, P=1.22e-08). Integrated computational analysis suggested a broad transcriptional regulatory impact of the variant. In vitro luciferase assay in PC-3 cells demonstrated allele-specific enhancer activity of the locus that is concomitantly modulated by AR and by CCAAT/Enhancer Binding Protein beta (CEBPB). ChIP assays experiments showed AR and CEBPB binding to the locus. Upon deletion of the genomic locus via CRISPR-Cas9 followed by transcriptome sequencing, we observed differential transcript levels along chromosome 7 between edited versus control cells, but not in edited versus edited or control versus control, and nominated genes that were also predicted to physically interact with the 7p14.3 locus by previously generated Hi-C data from prostate cells. Conclusions: Our study suggests a relevant role in cancer predisposition of non-coding variants that lead to allele specific transactivation with age dependent and tissue specific effect manifesting in early somatic genomic events. Citation Format: Alessandro Romanel, Sonia Iolanda Garritano, Blerta Stringa, Mirjam Blattner, Davide Dalfovo, Dimple Chakravarty, Kellie Cotter, Priyanka Dhingra, Paola Gasperini, Olivier Elemento, Andrea Sboner, Alberto Inga, Ekta Khurana, MarK Rubin, Francesca Demichelis. Inherited determinants of early recurrent somatic mutations in prostate cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr LB-232. doi:10.1158/1538-7445.AM2017-LB-232

Age is not a predictor of prognosis in metastatic cutaneous squamous cell carcinoma of the head and neck.

Metastatic cutaneous squamous cell carcinoma of the head and neck (cHNSCC) is more common in older patients. It is postulated that the age-related decline in immunity plays a role in cancer predisposition and prognosis. We aimed to investigate the effect of age on outcomes in cHNSCC and compare these with the outcomes of patients with cHNSCC and known immunosuppression. Patients with metastatic cHNSCC treated with curative intent were identified from a prospectively collated database of head and neck cancers at the Sydney Head and Neck Cancer Institute. Patients with cHNSCC with known immunosuppression provided a comparison group for analysis of disease-specific outcomes. The study cohort includes 418 immunocompetent patients with metastatic cHNSCC (median age: 73 years (interquartile range: 65-81 years)) and the control cohort includes 24 patients with metastatic cHNSCC and immunosuppression (median age: 51 years (interquartile range: 42-62 years)). Increasing age was not associated with poorer disease-free or disease-specific survival. Patients in older age groups (70 years and over) had better disease-specific outcomes than patients with long-term immunosuppression. Patterns of disease failure did not differ between different age groups. The number of positive nodes and extra-capsular spread were the only significant prognostic variables in multivariable analysis. In the context of metastatic cHNSCC, age should not be considered as a marker of poor prognosis. Age should not be considered a surrogate marker of immune function considering the poorer outcomes seen in patients with immunosuppression. Older patients with metastatic cHNSCC should be considered candidates for standard treatment if otherwise medically fit.

Whole-exome sequencing identifies rare pathogenic variants in new predisposition genes for familial colorectal cancer.

Purpose:Colorectal cancer is an important cause of mortality in the developed world. Hereditary forms are due to germ-line mutations in APC, MUTYH, and the mismatch repair genes, but many cases present familial aggregation but an unknown inherited cause. The hypothesis of rare high-penetrance mutations in new genes is a likely explanation for the underlying predisposition in some of these familial cases.Methods:Exome sequencing was performed in 43 patients with colorectal cancer from 29 families with strong disease aggregation without mutations in known hereditary colorectal cancer genes. Data analysis selected only very rare variants (0–0.1%), producing a putative loss of function and located in genes with a role compatible with cancer. Variants in genes previously involved in hereditary colorectal cancer or nearby previous colorectal cancer genome-wide association study hits were also chosen.Results:Twenty-eight final candidate variants were selected and validated by Sanger sequencing. Correct family segregation and somatic studies were used to categorize the most interesting variants in CDKN1B, XRCC4, EPHX1, NFKBIZ, SMARCA4, and BARD1.Conclusion:We identified new potential colorectal cancer predisposition variants in genes that have a role in cancer predisposition and are involved in DNA repair and the cell cycle, which supports their putative involvement in germ-line predisposition to this neoplasm.

UMD-MLH1/MSH2/MSH6 databases: description and analysis of genetic variations in French Lynch syndrome families

Lynch syndrome is an autosomal dominant disease caused by germ line heterozygous mutations mainly involving the MSH2, MLH1 and MSH6 genes that belong to the DNA MisMatch Repair (MMR) genes family. The French network counting the 16 licensed laboratories involved in Lynch syndrome genetic testing developed three locus-specific databases with the UMD® software (www.umd.be/MLH1/, www.umd.be/MSH2/ and www.umd.be/MSH6/) that presently contain a total of 7047 sequence variations including 707 distinct variations of a priori unknown functional significance (VUS) that were identified through complete mutation screening or targeted predictive testing. Mutation carriers are at high risk for developing early-onset colorectal and endometrial adenocarcinomas. Consensus clinical guidelines have been proposed, allowing the efficient detection of curable lesions. The major challenge of genetic testing is to reliably classify the genomic variations in those patients who seek genetic counseling. Combining the interactive tools of the software, the relevant published data and mainly original information produced by the French MisMatch Repair network, the UMD-MLH1/MSH2/MSH6 databases provide interpretation data for the 707 VUS that were classified according to the IARC 5-Class system. These public databases are regularly updated to improve the classification of all registered VUS, exploring their role in cancer pre-disposition based on structural and functional approaches.

Germline Alterations of the RNASEL Gene, a Candidate HPC1 Gene at 1q25, in Patients and Families with Prostate Cancer

The RNASEL gene (2',5'-oligoisoadenylate-synthetase dependent) encodes a ribonuclease that mediates the antiviral and apoptotic activities of interferons. The RNASEL gene maps to the hereditary-prostate-cancer (HPC)-predisposition locus at 1q24-q25 (HPC1) and was recently shown to harbor truncating mutations in two families with linkage to HPC1. Here, we screened for RNASEL germline mutations in 66 Finnish patients with HPC, and we determined the frequency of the changes in the index patients from 116 families with HPC, in 492 patients with unselected prostate cancer (PRCA), in 223 patients with benign prostatic hyperplasia (BPH), and in 566 controls. A truncating mutation, E265X, was found in 5 (4.3%) of the 116 patients from families with HPC. This was significantly higher (odds ratio [OR] =4.56; P=.04) than the frequency of E265X in controls (1.8%). The highest mutation frequency (9.5%) was found in patients from families with four or more affected members. Possible segregation was detected only in a single family. However, the median age at disease onset for E265X carriers was 11 years less than that for noncarriers in the same families. In addition, of the four missense variants found, R462Q showed an association with HPC (OR=1.96; P=.07). None of the variants showed any differences between controls and either patients with BPH or patients with PRCA. We conclude that, although RNASEL mutations do not explain disease segregation in Finnish families with HPC, the variants are enriched in families with HPC that include more than two affected members and may also be associated with the age at disease onset. This suggests a possible modifying role in cancer predisposition. The impact that the RNASEL sequence variants have on PRCA burden at the population level seems small but deserves further study.

Increased Levels of Mutagen-Induced Chromosome Breakage in Down Syndrome Children with Malignancy

Even though an association between Down syndrome (DS) and malignancies has been established, the mechanism behind this is still unclear. We therefore investigated constitutional chromosomal abnormalities and bleomycin-induced chromosome sensitivity in 12 DS children, 8 DS children with malignancies, and 10 normal controls to explore whether these factors play any role in cancer predisposition. Trisomy 21 was the only constitutional cytogenetic abnormality observed in all the DS children. But there was significant variation between the patients and controls with regard to bleomycin sensitivity. Compared to the normal controls, all the DS patients expressed significantly higher chromosomal breaks per cell (b/c) values indicating sensitivity to bleomycin. Furthermore, DS children with malignancies demonstrated significantly higher b/c values than DS children without malignancies. These results permit us to assume that DS children showing mutagen hypersensitivity may be having defective DNA repair competence and hence may be predisposed to malignancies.

Genetic Testing for Cancer Risk Assessment: A Review

Both environmental factors and an inherited predisposition influence carcinogenesis. The direct role of inheritance in the development of cancer is evident in familial cancer syndromes. These syndromes predispose to cancer through the inheritance of a mutation in a single gene in affected carriers. While many inherited cancer syndromes are rare, an inherited predisposition is directly responsible for 5%-10% of all colon and breast cancers. Complex multigenic inheritance plays an important role in cancer predisposition for the population at large. The identification of genes responsible for an inherited predisposition to colon and breast cancer syndromes has directed public attention to genetic testing for susceptibility to cancer. Assays are currently available to determine individual susceptibility to specific cancers. Cancer genetic testing is currently a time-consuming and complex procedure which requires expertise in its application, interpretation, and follow-up strategic planning. This review discusses cancer genetics and its application to individual and family cancer risk assessment with particular emphasis on breast and colon cancer.

Familial cancer syndromes and clusters.

The study of rare families in which a variety of cancers occur, usually at an early age and with patterns consistent with a common hereditary mechanism, has contributed much to our understanding of the process of carcinogenesis. So far, genes identified as having a role in cancer predisposition in these families have also been important in the histogenesis of sporadic cancers. In the two most clearly defined cancer family syndromes, the Li-Fraumeni syndrome and Lynch syndrome II, the genes involved predispose to diverse but specific constellations of cancers. Genes associated with site-specific familial cancer clusters may also give rise to increased susceptibility to other cancers, and site-specific clusters may represent one end of a spectrum. A consistent feature of familial cancer syndromes is the variable expression within and between families. A challenge for the future will be to determine other factors which may interact with the principal genes involved, giving rise to this variability.