title: PIK3CA mutations are common in lobular carcinoma in situ, but are not a biomarker of progression.
abstract: Lobular carcinoma in situ (LCIS) is a non-invasive breast lesion that is typically found incidentally on biopsy and is often associated with invasive lobular carcinoma (ILC). LCIS is considered by some to be a risk factor for future breast cancer rather than a true precursor lesion. The aim of this study was to identify genetic changes that could be used as biomarkers of progression of LCIS to invasive disease using cases of pure LCIS and comparing their genetic profiles to LCIS which presented contemporaneously with associated ILC, on the hypothesis that the latter represents LCIS that has already progressed.
  
  
  
  Somatic copy number aberrations (SCNAs) were assessed by SNP array in three subgroups: pure LCIS, LCIS associated with ILC and the paired ILC. In addition exome sequencing was performed on seven fresh frozen samples of LCIS associated with ILC, to identify recurrent somatic mutations.
  
  
  
  The copy number profiles of pure LCIS and LCIS associated with ILC were almost identical. However, four SCNAs were more frequent in ILC than LCIS associated with ILC, including gain/amplification of CCND1. CCND1 protein over-expression assessed by immunohistochemical analysis in a second set of samples from 32 patients with pure LCIS and long-term follow up, was associated with invasive recurrence (P = 0.02, Fisher's exact test). Exome sequencing revealed that PIK3CA mutations were as frequent as CDH1 mutations in LCIS, but were not a useful biomarker of LCIS progression as they were as frequent in pure LCIS as in LCIS associated with ILC. We also observed heterogeneity of PIK3CA mutations and evidence of sub-clonal populations in LCIS irrespective of whether they were associated with ILC.
  
  
  
  Our data shows that pure LCIS and LCIS co-existing with ILC have very similar SCNA profiles, supporting the hypothesis that LCIS is a true precursor lesion. We have provided evidence that over-expression of CCND1 may identify a subgroup of patients with pure LCIS who are more likely to develop invasive disease, in contrast to PIK3CA mutations, which occur too early in lobular tumorigenesis to be informative.
authors.affiliation: Division of Cancer Studies, Guy's Hospital, King's College London, London, SE1 9RT, UK.
authors.forename: Vandna
authors.initials: V
authors.lastname: Shah
authors.affiliation: Division of Cancer Studies, Guy's Hospital, King's College London, London, SE1 9RT, UK.
authors.forename: Salpie
authors.initials: S
authors.lastname: Nowinski
authors.affiliation: Division of Cancer Studies, Guy's Hospital, King's College London, London, SE1 9RT, UK.
authors.forename: Dina
authors.initials: D
authors.lastname: Levi
authors.affiliation: Division of Cancer Studies, Guy's Hospital, King's College London, London, SE1 9RT, UK.
authors.forename: Irek
authors.initials: I
authors.lastname: Shinomiya
authors.affiliation: Division of Cancer Studies, Guy's Hospital, King's College London, London, SE1 9RT, UK.
authors.forename: Narda
authors.initials: N
authors.lastname: Kebaier Ep Chaabouni
authors.affiliation: Division of Cancer Studies, Guy's Hospital, King's College London, London, SE1 9RT, UK.
authors.forename: Cheryl
authors.initials: C
authors.lastname: Gillett
authors.affiliation: Breast Cancer Now Unit, Research Oncology & Cancer Epidemiology, Guy's Hospital, King's College London, London, SE1 9RT, UK.
authors.forename: Anita
authors.initials: A
authors.lastname: Grigoriadis
authors.affiliation: Evolution and Cancer laboratory, Centre for Tumour Biology, Barts Cancer Institute, Queen Mary University of London, London, UK.
authors.forename: Trevor A
authors.initials: TA
authors.lastname: Graham
authors.affiliation: Department of Oncology, UCLH Foundation Trust, London, NW1 2PG, UK.
authors.forename: Rebecca
authors.initials: R
authors.lastname: Roylance
authors.affiliation: Medical and Molecular Genetics, Guy's Hospital, King's College London, London, UK.
authors.forename: Michael A
authors.initials: MA
authors.lastname: Simpson
authors.affiliation: Division of Cancer Studies, Guy's Hospital, King's College London, London, SE1 9RT, UK.
authors.forename: Sarah E
authors.initials: SE
authors.lastname: Pinder
authors.affiliation: Division of Cancer Studies, Guy's Hospital, King's College London, London, SE1 9RT, UK. elinor.sawyer@kcl.ac.uk.
authors.forename: Elinor J
authors.initials: EJ
authors.lastname: Sawyer
mesh_terms: D000483:Alleles; D015415:Biomarkers; D000071960:Breast Carcinoma In Situ / Q000235:genetics* / Q000473:pathology*; D001943:Breast Neoplasms / Q000235:genetics* / Q000473:pathology*; D018275:Carcinoma, Lobular / Q000235:genetics* / Q000473:pathology*; D002874:Chromosome Mapping; D058534:Class I Phosphatidylinositol 3-Kinases; D056915:DNA Copy Number Variations; D004252:DNA Mutational Analysis; D018450:Disease Progression; D059472:Exome; D005260:Female; D005787:Gene Frequency; D018740:Genetic Heterogeneity; D005838:Genotype; D059014:High-Throughput Nucleotide Sequencing; D006801:Humans; D007150:Immunohistochemistry; D017404:In Situ Hybridization, Fluorescence; D018895:Microsatellite Repeats; D009154:Mutation; D019869:Phosphatidylinositol 3-Kinases / Q000235:genetics* / Q000378:metabolism; D020641:Polymorphism, Single Nucleotide
chemical_list: D015415:Biomarkers; D019869:Phosphatidylinositol 3-Kinases; D058534:Class I Phosphatidylinositol 3-Kinases; C484760:PIK3CA protein, human
keywords: CCND1; Heterogeneity; Lobular carcinoma in situ; PIK3CA; Somatic copy number aberrations