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PALB2-mutation carriers not only have an increased risk for breast cancer (BC) but also for pancreatic cancer (PC). Thus far, PALB2 mutations have been mainly found in PC patients from families affected by both PC and BC. As it is well known that the prevalence of gene mutations varies between different populations, we studied the prevalence of PALB2 mutations in a Dutch cohort of non-BRCA1/2 familial PC (FPC) families and in non-BRCA1/2 familial BC (FBC) families with at least one PC case. Mutation analysis included direct sequencing and multiplex ligation-dependent probe amplification (MLPA) and was performed in a total of 64 patients from 56 distinct families (28 FPC families, 28 FBC families). In total, 31 patients (48%) originated from FPC families; 24 were FPC patients (77%), 6 had a personal history of BC (19%) and 1 was a suspected carrier (3.2%). The remaining 33 patients (52%) were all female BC patients of whom 31 (94%) had a family history of PC and 2 (6.1%) had a personal history of PC. In none of these 64 patients a PALB2 mutation was found. Therefore, PALB2 does not have a major causal role in familial clustering of PC and BC in non-BRCA1/2 families in the Dutch population.
Recently, it has become clear that the Fanconi gene FANCN/PALB2 (partner and localizer of BRCA2) should not only be considered as a susceptibility gene for breast cancer (BC)1 but also as a susceptibility gene for pancreatic cancer (PC).2 Mutations in this gene may be associated with familial clustering of PC and BC.1, 2, 3, 4, 5, 6, 7, 8, 9, 10
Previous studies have shown that PALB2-mutation-positive familial BC (FBC) patients were significantly more likely to have a relative with PC,5 and that nearly all PALB2-mutation positive familial PC (FPC) families were affected by at least one BC case.4
Given these findings and the fact that the prevalence of gene mutations varies between different populations, we aimed to determine the prevalence of PALB2 mutations in Dutch cohorts of non-BRCA1/2 FPC patients and of non-BRCA1/2 FBC patients with a personal or family history of PC.
The prevalence of germline mutations in PALB2 was investigated in Dutch non-BRCA1/2 FPC patients and non-BRCA1/2 FBC patients with a personal or family history of PC.
FPC families were defined as families with PC in either ≥2 first-degree relatives (FDRs), ≥3 relatives (FDR and second-degree relative (SDR)) or 2 SDRs of whom one was <50 years at diagnosis and did not meet diagnostic criteria of specific other cancer syndromes.11 These families were identified in the registries of the Clinical Genetic Centres of Amsterdam (Academic Medical Centre-University Medical Centre Amsterdam and Netherlands Cancer Institute), Rotterdam (Erasmus MC-University Medical Centre Rotterdam), and Groningen (University Medical Centre Groningen), consisting of a total of 40 FPC families. In 28 of these families, DNA was available for PALB2 mutation analysis. In families in which DNA was available of multiple family members affected by PC, PALB2 mutation analysis was performed in DNA of all cases. In families without available DNA from PC patients, mutation analysis was performed in family members affected by BC. In one family, mutation analysis was performed in a suspected carrier; this suspicion was based on the position of this individual in the pedigree; this specific case had a sibling with PC and a child with PC.
The FBC patients were taken from the registry from the Netherlands Cancer Institute and consisted of non-BRCA1/2 BC patients that fulfilled the Dutch clinical criteria for BRCA1 and BRCA2 mutation testing, which include (1) BC diagnosis at age <35 years, (2) bilateral BC of which one diagnosis at age <50 years, (3) at least two FDR with BC at an age <50 years, (4) at least three FDR or SDR with BC, and (5) one <50 years at diagnosis. From this registry, patients with a personal history of both BC and PC, and BC patients with a FDR or SDR with PC were selected. In families in which DNA was available of multiple affected family members, PALB2 mutation analysis was performed in all cases.
At the time of genetic counselling, patients had given written informed consent to use their DNA for the search for new cancer-susceptibility genes.
The presence of germline mutations in PALB2 was evaluated by direct sequencing of the entire coding region and by sequencing intron–exon boundaries on genomic DNA isolated from whole blood. Primer pairs that were used have been previously described.12
The presence of large genomic deletions in PALB2 was analysed by MLPA using the MLPA P057 kit of MRC-Holland (Amsterdam, The Netherlands) as previously described.13 As a positive control, genomic DNA from the previously described PALB2 FA patient EUFA1341 was included in the analysis.12
PALB2 mutation analysis was performed in a total of 64 patients from 56 distinct families (28 FPC families, 28 FBC families; Table 1). In total, 31 patients (48%) originated from FPC families; 24 were FPC patients (77%), 6 had a personal history of BC (19%) and 1 was a suspected carrier (3.2%). The remaining 33 patients (52%) were all female BC patients of whom 31 (94%) had a family history of PC and 2 (6.1%) had a personal history of PC.
The 28 FPC families had a total of 70 affected patients with PC of which 57 (81%) were confirmed by medical (n=11) or pathology reports (n=46) (Table 2). The mean age at time of PC diagnosis was 61 years (SD±11.5). In total, 38 of the PC patients (54%) were male. Ten FPC families (36%) had at least three family members diagnosed with PC. Fourteen FPC families (50%) were affected by BC. Among the 33 tested patients from 28 FBC families, the mean age at BC diagnosis was 42 years (SD±9.5). The total number of PC cases was 29, of which 24 (83%) were confirmed by medical (n=13) or pathology report (n=11). The mean age at PC diagnosis was 70 years (SD±10.9) and 41% (n=12) of all PC cases were male.
In none of these cases was a PALB2 mutation found by direct sequencing and MLPA.
Our data provide further evidence that there is a limited causal role for PALB2 mutations in both FPC and FBC, as we did not identify any PALB2 mutations in our Dutch cohort of 28 FPC families and 28 FBC families affected with at least one case of PC.
Since the recent recognition of PALB2 as BC- and PC-susceptibility gene,1, 2 a number of studies have been carried out to investigate the role of PALB2 in different patient populations. Our results are in line with the results of these previous reports in which no PALB2 mutations,9, 14 or low prevalence of PALB2 mutations,2, 4, 7, 8, 10 were found. It should be mentioned that the relatively small sample size could be a possible explanation for that no mutation carrier was identified in the current study. Even if a larger sample size might have detected sporadic cases, its results do show that the role of PALB2 in this particular setting is insignificant. When combining our data with the previously published data, PALB2 is involved in only 2.3% (7/306, range 0–3.7%, 95% CI 0.6–40%) of all FPC families and in 1.6% (5/306, range 0–4.8%, 95% CI 0.21–31%) of all FBC families with PC cases (Table 3).
Although PALB2 is involved in the clustering of both PC and BC, it explains only a small fraction of the clustering, and it is therefore crucial that future research is directed towards identifying the gene(s) that are involved in the development of both FPC and FBC. Knowledge of additional PC- and BC-susceptibility genes will be helpful in the counselling of family members from FPC and FBC families, as this will improve our ability to identify individuals at increased risk of developing PC and BC. Furthermore, it will have implications on the effectiveness of screening which will be highest when only directed towards individuals at risk.
In conclusion, our results provide further evidence for the low prevalence of PALB2 mutations among non-BRCA1/2 FPC families and FBC families with PC cases. Therefore, routine analysis of this gene in these families is not warranted. Future research should be directed towards specifying subtypes of FPC/FBC families in which PALB2 analysis is useful towards identifying other gene(s) involved in the development of PC and BC.
On behalf of the Dutch Research Group of Pancreatic Cancer Surveillance in High-Risk Individuals (in alphabetical order): Amsterdam Medical Center: Cora M Aalfs, Marcel GW Dijkgraaf, Paul Fockens, Dirk J Gouma, Jeanin E van Hooft, C Yung Nio, Theo AM van Os, Ellen MA Smets. Erasmus Medical Center: Katharina Biermann, Marco J Bruno, Henny van Duijl, Casper HJ van Eijck, Femme Harinck, Nanda Krak, Jan-Werner Poley, Anja Wagner. The Netherlands Cancer Institute-Antoni van Leeuwenhoek Hospital: Eveline MA Bleiker, Annemieke Cats, Irma Kluijt, Anja van Rens, Grace Sidharta, Senno Verhoef. University Medical Center Groningen: Hendrik M van Dullemen, Rolf H Sijmons.
The authors declare no conflict of interest.