Homologous recombination DNA repair defects in PALB2- associated breast cancers

Abstract: Mono-allelic germline pathogenic variants in the Partner And Localizer of BRCA2 (PALB2) gene predispose to a high-risk of breast cancer development, consistent with the role of PALB2 in homologous recombination (HR) DNA repair. Here, we sought to define the repertoire of somatic genetic alterations in PALB2-associated breast cancers (BCs), and whether PALB2-associated BCs display bi-allelic inactivation of PALB2 and/or genomic features of HR-deficiency (HRD). Twenty-four breast cancer patients with pathogenic PALB2 germline mutations were analyzed by whole-exome sequencing (WES, n = 16) or targeted capture massively parallel sequencing (410 cancer genes, n = 8). Somatic genetic alterations, loss of heterozygosity (LOH) of the PALB2 wild-type allele, large-scale state transitions (LSTs) and mutational signatures were defined. PALB2-associated BCs were found to be heterogeneous at the genetic level, with PIK3CA (29%), PALB2 (21%), TP53 (21%), and NOTCH3 (17%) being the genes most frequently affected by somatic mutations. Bi-allelic PALB2 inactivation was found in 16 of the 24 cases (67%), either through LOH (n = 11) or second somatic mutations (n = 5) of the wild-type allele. High LST scores were found in all 12 PALB2-associated BCs with bi-allelic PALB2 inactivation sequenced by WES, of which eight displayed the HRD-related mutational signature 3. In addition, bi-allelic inactivation of PALB2 was significantly associated with high LST scores. Our findings suggest that the identification of bi-allelic PALB2 inactivation in PALB2-associated BCs is required for the personalization of HR-directed therapies, such as platinum salts and/or PARP inhibitors, as the vast majority of PALB2-associated BCs without PALB2 bi-allelic inactivation lack genomic features of HRD

The FANCM:p.Arg658* truncating variant is associated with risk of triple-negative breast cancer

Abstract: Breast cancer is a common disease partially caused by genetic risk factors. Germline pathogenic variants in DNA repair genes BRCA1, BRCA2, PALB2, ATM, and CHEK2 are associated with breast cancer risk. FANCM, which encodes for a DNA translocase, has been proposed as a breast cancer predisposition gene, with greater effects for the ER-negative and triple-negative breast cancer (TNBC) subtypes. We tested the three recurrent protein-truncating variants FANCM:p.Arg658*, p.Gln1701*, and p.Arg1931* for association with breast cancer risk in 67,112 cases, 53,766 controls, and 26,662 carriers of pathogenic variants of BRCA1 or BRCA2. These three variants were also studied functionally by measuring survival and chromosome fragility in FANCM−/− patient-derived immortalized fibroblasts treated with diepoxybutane or olaparib. We observed that FANCM:p.Arg658* was associated with increased risk of ER-negative disease and TNBC (OR = 2.44, P = 0.034 and OR = 3.79; P = 0.009, respectively). In a country-restricted analysis, we confirmed the associations detected for FANCM:p.Arg658* and found that also FANCM:p.Arg1931* was associated with ER-negative breast cancer risk (OR = 1.96; P = 0.006). The functional results indicated that all three variants were deleterious affecting cell survival and chromosome stability with FANCM:p.Arg658* causing more severe phenotypes. In conclusion, we confirmed that the two rare FANCM deleterious variants p.Arg658* and p.Arg1931* are risk factors for ER-negative and TNBC subtypes. Overall our data suggest that the effect of truncating variants on breast cancer risk may depend on their position in the gene. Cell sensitivity to olaparib exposure, identifies a possible therapeutic option to treat FANCM-associated tumors

Characteristics of 15 high-risk breast cancer families selected for exome sequencing.

a<p>Breast cancer (BC), ovarian cancer (OC), bilat. (bilateral). Age of diagnosis shown in parentheses.</p>b<p>Other cancer types observed in family branch with apparent breast cancer risk (multiple cases shown in parentheses).</p

<i>FANCC</i> and <i>BLM</i> mutations identified in familial breast cancer pedigrees.

<p>Males and females are represented by squares and circles, respectively. Arrows indicate individuals who underwent whole exome sequencing (families 1–3) or were the index case in subsequent mutation analysis (<i>FANCC</i> p.Asp23fs, p.Leu554Pro and p.Arg185Gln and <i>BLM</i> p.Arg899* families). Cancer-affected individuals are represented with the following symbols: breast cancer, top right quadrant filled in; bilateral breast cancer, top half; ovarian cancer, bottom left quadrant; or other cancers as indicated, centre circle. Mutation status is indicated with either the family specific mutation or wildtype (wt) under each tested individual. Age at cancer diagnosis or year of birth (b.) where known is shown for all mutation carriers. Breast cancer (BC), ovarian cancer (OC), acute leukaemia (AL), colorectal cancer (CRC), haematological malignancy (type unspecified) (Haem.), kidney cancer (KC), liver cancer (LivC), melanoma (Mel.), pancreatic cancer (PaC), prostate cancer (PrC), skin non-melanoma (Non-mel.) stomach cancer (SC), testicular cancer (TestC). Mutations indicated in parentheses indicate untested obligate carriers. Family 2 contains an individual (indicated by #) for whom mutation status is inferred assuming that non-paternity or gonadal mosaicism have not occurred.</p

Homologous recombination DNA repair defects in PALB2-associated breast cancers

Mono-allelic germline pathogenic variants in the Partner And Localizer of BRCA2 (PALB2) gene predispose to a high-risk of breast cancer development, consistent with the role of PALB2 in homologous recombination (HR) DNA repair. Here, we sought to define the repertoire of somatic genetic alterations in PALB2-associated breast cancers (BCs), and whether PALB2-associated BCs display bi-allelic inactivation of PALB2 and/or genomic features of HR-deficiency (HRD). Twenty-four breast cancer patients with pathogenic PALB2 germline mutations were analyzed by whole-exome sequencing (WES, n = 16) or targeted capture massively parallel sequencing (410 cancer genes, n = 8). Somatic genetic alterations, loss of heterozygosity (LOH) of the PALB2 wild-type allele, large-scale state transitions (LSTs) and mutational signatures were defined. PALB2-associated BCs were found to be heterogeneous at the genetic level, with PIK3CA (29%), PALB2 (21%), TP53 (21%), and NOTCH3 (17%) being the genes most frequently affected by somatic mutations. Bi-allelic PALB2 inactivation was found in 16 of the 24 cases (67%), either through LOH (n = 11) or second somatic mutations (n = 5) of the wild-type allele. High LST scores were found in all 12 PALB2-associated BCs with bi-allelic PALB2 inactivation sequenced by WES, of which eight displayed the HRD-related mutational signature 3. In addition, bi-allelic inactivation of PALB2 was significantly associated with high LST scores. Our findings suggest that the identification of bi-allelic PALB2 inactivation in PALB2-associated BCs is required for the personalization of HR-directed therapies, such as platinum salts and/or PARP inhibitors, as the vast majority of PALB2-associated BCs without PALB2 bi-allelic inactivation lack genomic features of HRD

Publisher Correction: Homologous recombination DNA repair defects in PALB2-associated breast cancers (npj Breast Cancer, (2019), 5, 1, (23), 10.1038/s41523-019-0115-9)

In the original version of this paper, the link to the data record in the Data Availability Statement was incorrectly listed as https:// doi.org/10.6084/m9.figshare.8138912.44. The link has been corrected to https://doi.org/10.6084/m9.figshare.8138912. This has been corrected in the HTML and PDF versions of this article

Publisher correction: Homologous recombination DNA repair defects in PALB2-associated breast cancers

Original article published in "npj Breast Cancer, (2019), 5, 1, (23), 10.1038/s41523-019-0115-9"In the original version of this paper, the link to the data record in the Data Availability Statement was incorrectly listed as https:// doi.org/10.6084/m9.figshare.8138912.44. The link has been corrected to https://doi.org/10.6084/m9.figshare.8138912. This has been corrected in the HTML and PDF versions of this article.</p

Publisher Correction: Homologous recombination DNA repair defects in PALB2 -associated breast cancers

An amendment to this paper has been published and can be accessed via a link at the top of the paper