Targeted Next-Generation Sequencing Identifies a Recurrent Mutation in <i>MCPH1</i> Associating with Hereditary Breast Cancer Susceptibility

<div><p>Breast cancer is strongly influenced by hereditary risk factors, a majority of which still remain unknown. Here, we performed a targeted next-generation sequencing of 796 genes implicated in DNA repair in 189 Finnish breast cancer cases with indication of hereditary disease susceptibility and focused the analysis on protein truncating mutations. A recurrent heterozygous mutation (c.904_916del, p.Arg304ValfsTer3) was identified in early DNA damage response gene, <i>MCPH1</i>, significantly associating with breast cancer susceptibility both in familial (5/145, 3.4%, <i>P</i> = 0.003, OR 8.3) and unselected cases (16/1150, 1.4%, <i>P</i> = 0.016, OR 3.3). A total of 21 mutation positive families were identified, of which one-third exhibited also brain tumors and/or sarcomas (<i>P</i> = 0.0007). Mutation carriers exhibited significant increase in genomic instability assessed by cytogenetic analysis for spontaneous chromosomal rearrangements in peripheral blood lymphocytes (<i>P</i> = 0.0007), suggesting an effect for MCPH1 haploinsufficiency on cancer susceptibility. Furthermore, 40% of the mutation carrier tumors exhibited loss of the wild-type allele. These findings collectively provide strong evidence for <i>MCHP1</i> being a novel breast cancer susceptibility gene, which warrants further investigations in other populations.</p></div

Examples of <i>MCPH1</i> mutation positive families (A-C).

<p>Patients with breast cancer are marked with black half circles. Other cancer types are marked with grey squares. The age at diagnosis, when known, is marked below the cancer type. Individuals genotyped for <i>MCPH1</i> c.904_916del are marked with either a plus (mutation positive) or a minus sign (mutation negative). A slashed pedigree symbol indicates a deceased individual. Triangle indicates the initially studied index patient (BR-0653, BR-0887 and BR-0154, respectively). Abbreviations: Bas: basalioma, Bt: brain tumor, Br: breast cancer, Col: colon cancer, Csu: cancer site unknown, Lar: laryngeal cancer, Ov: ovarian tumor, Pro: prostate cancer, Ut: uterine cancer, Vul: vulvar cancer.</p

Family history of cancers of <i>MCPH1</i> c.904_916del positive index cases^a.

<p>Family history of cancers of <i>MCPH1</i> c.904_916del positive index cases<a href="http://www.plosgenetics.org/article/info:doi/10.1371/journal.pgen.1005816#t002fn004" target="_blank">^a</a>.</p

Occurrence of chromosomal aberrations in blood lymphocyte metaphases of heterozygous <i>MCPH1</i> c.904_916del mutation carriers and healthy controls.

<p>Occurrence of chromosomal aberrations in blood lymphocyte metaphases of heterozygous <i>MCPH1</i> c.904_916del mutation carriers and healthy controls.</p

Frequency of <i>RAD52</i>, <i>HSD17B14</i> and <i>RAD51C</i> CNV carriers in the studied breast cancer cases and controls.

Frequency of RAD52, HSD17B14 and RAD51C CNV carriers in the studied breast cancer cases and controls.</p

Frequencies and ORs for the c.541C>T mutation among the different patient subgroups in the Helsinki, Tampere, Oulu, and Belarus series.

<p>Frequencies and ORs for the c.541C>T mutation among the different patient subgroups in the Helsinki, Tampere, Oulu, and Belarus series.</p

Variants identified in the screening of the <i>RAD51B</i> gene (RefSeq NM_133509.3).

<p>Variants identified in the screening of the <i>RAD51B</i> gene (RefSeq NM_133509.3).</p

Association of rs2046210 and rs12662670 with breast cancer.

<p>Results are presented overall and separately for Europeans and Asians. Pooled analyses adjusted for study only as well as adjusted for rs12662670 or rs2046210, respectively, in addition to study were performed.</p>a<p>P-value derived from the log-additive model.</p>b<p>Odds ratio per minor allele (A allele for rs2046210, G allele for rs12662670).</p>c<p>Odds ratio relative to the major allele homozygous (GT) genotype.</p

Association of rs12662670 with breast cancer in Europeans versus Asians.

<p>Association of rs12662670 with breast cancer in Europeans versus Asians.</p