Absence of the FANCM c.5101C>T mutation in BRCA1/2-negative triple-negative breast cancer patients from Pakistan.

Abstract

Breast cancer is the most common cancer among women worldwide. Approximately 5–10 % of breast cancers are hereditary, and caused by monoallelic germ line mutations in high-, moderate-, and low-penetrance breast cancer susceptibility genes. Several of these genes such as BRCA1, BRCA2, PALB2, BRIP1, and genes of the RAD51 family play an important role in maintenance of genomic stability and are functionally linked with homologous recombination-mediated DNA damage repair. Breast cancer susceptibility is connected with the Fanconi anemia (FA) pathway, since biallelic mutations in at least four genes, BRCA2 (FANCD1) [1], PALB2 (FANCN) [2], BRIP1 (FANCJ) [3], and RAD51C (FANCO) [4] have been shown to also cause FA. Recently, Kiiski and colleagues identified the FA complementation group M (FANCM) gene as a novel breast cancer susceptibility gene [5]. A nonsense mutation in exon 20, c.5101C[T (p.Q1701X), was identified by exome sequencing of germline DNA samples from 24 breast cancer patients from eleven BRCA1/2-negative Finnish breast cancer families. Further genotyping of a large sample set of breast or ovarian cancer cases and controls revealed a 3.5-fold increased frequency among triple-negative breast cancer (TNBC) cases and an approximately twofold increased mutation frequency among all breast cancer cases compared with controls. Given that deleterious mutations in other FA genes including FANCD1 (BRCA2) and FANCO (RAD51C) have previously been identified among TNBC patients from Pakistan [6, 7], we investigated whether the FANCM c.5101C[T mutation is associated with TNBC in Pakistan. Constitutional genomic DNA of 117 BRCA1/2-negative TNBC patients and 188 controls from Pakistan were screened for the FANCM c.5101C[T mutation. Of the TNBC cases, 75 were diagnosed with early-onset disease (B30 years of age), 37 belonged to families with C2 breast cancer cases, and five to breast–ovarian cancer families (Table 1). The median age of diagnosis was 28 years (range 18–67). Forty-four of the cases have been previously described [7]. Screening for the c.5101C[T mutation was performed using denaturing high-performance liquid chromatography (DHPLC) analyses followed by DNA sequencing of variant fragments. PCR primer sequences were as previously described [5]. DHPLC running conditions are available upon request. A positive mutation control was included in all DHPLC runs. The c.5101C[T mutation was not identified in any of the 117 TNBC cases and 188 controls implying that this mutation does not or rarely contributes to TNBC in this population. In line with our data, this mutation was also not detected in previous studies among 965 Icelandic unselected breast cancer patients including 92 BRCA1/2negative familial cases [5], 95 BRCA1/2-negative familial cases from Spain [8], and 3409 BRCA1/2-negative familial cases and 3896 controls from Italy, Netherland, Australia, and Spain [9]. The findings of these studies suggest that the c.5101C[T may be specific to the Finnish population. In the current study, we identified two other FANCM missense mutations. A mutation, c.4931G[A (p.R1644Q), & Muhammad U. Rashid usmanr@skm.org.pk