title: Mapping of actionable mutations to histological subtype domains in lung adenocarcinoma: implications for precision medicine.
abstract: Precision medicine depends on the accurate identification of actionable mutations in a tumor sample. It is unknown how heterogeneous the distribution of such mutations can be in a tumor. Morphological (i.e. histopathological) heterogeneity is well described in lung adenocarcinoma and has been specifically recognized in the most recent official clinico-pathological classification. The most predominant subtype present is now used to classify each lung adenocarcinoma. No molecular profile exists to explain the intratumoral differences in lung adenocarcinoma morphology, despite the consistently observed association between specific predominant subtypes and poorer survival. Given a recent proposal stratifying lung adenocarcinoma into subtypes of differing metastatic potential, we questioned the assumption that major mutations are present uniformly throughout tumors; especially those showing discrete different subtypes. We selected formalin-fixed paraffin embedded lung adenocarcinoma specimens that showed discrete areas of different subtypes, extracted subtype DNA samples from those areas and screened for mutations in hotspot regions of the EGFR, KRAS and BRAF genes using high resolution melting. Sanger sequencing was used to confirm all identified mutations. Chromogenic in situ hybridization (CISH) was used to identify mutant allele specific imbalances in tumors with EGFR mutations. Interestingly, we found that KRAS and BRAF mutations could be confined to morphological domains of higher grade. On the other hand, EGFR mutations were found through all histological subtypes in each tumor consistent with the driver status of this mutation. Intratumoral heterogeneity has major implications for tumorigenesis, chemoresistance and the role of histopathology in molecular screening for precision medicine. This study not only confirms that intratumoral mutational heterogeneity does occur, but also that it is associated with morphologically distinct regions in some tumors. From a practical perspective, small biopsies may not adequately represent a tumor's full mutational profile, particularly for later arising but prognostically important mutations such as those in the KRAS and BRAF genes.
authors.affiliation: University of Melbourne Department of Surgery, St Vincent's Hospital Melbourne, Victoria, Australia.
authors.forename: Gavin M
authors.initials: GM
authors.lastname: Wright
authors.forename: Hongdo
authors.initials: H
authors.lastname: Do
authors.forename: Jonathan
authors.initials: J
authors.lastname: Weiss
authors.forename: Naveed Z
authors.initials: NZ
authors.lastname: Alam
authors.forename: Vivek
authors.initials: V
authors.lastname: Rathi
authors.forename: Marzena
authors.initials: M
authors.lastname: Walkiewicz
authors.forename: Thomas
authors.initials: T
authors.lastname: John
authors.forename: Prudence A
authors.initials: PA
authors.lastname: Russell
authors.affiliation: Translational Genomics and Epigenomics Laboratory Ludwig Institute for Cancer Research Olivia Newton-John Cancer and Wellness Centre Heidelberg, Victoria, Australia.
authors.forename: Alexander
authors.initials: A
authors.lastname: Dobrovic
mesh_terms: D000230:Adenocarcinoma / Q000235:genetics* / Q000473:pathology*; D001483:Base Sequence; D004252:DNA Mutational Analysis; D006801:Humans; D017403:In Situ Hybridization; D008175:Lung Neoplasms / Q000235:genetics* / Q000473:pathology*; D008969:Molecular Sequence Data; D009154:Mutation; D016133:Polymerase Chain Reaction; D057285:Precision Medicine; D011518:Proto-Oncogene Proteins / Q000235:genetics*; D048493:Proto-Oncogene Proteins B-raf / Q000235:genetics*; D016283:Proto-Oncogene Proteins p21(ras); D018631:ras Proteins / Q000235:genetics*
chemical_list: C117307:KRAS protein, human; D011518:Proto-Oncogene Proteins; C482119:BRAF protein, human; D048493:Proto-Oncogene Proteins B-raf; D016283:Proto-Oncogene Proteins p21(ras); D018631:ras Proteins
references.citation: Lung Cancer. 2005 Oct;50(1):1-8
references.pmid: 15950315
references.citation: J Clin Invest. 2011 Oct;121(10):3810-8
references.pmid: 21965338
references.citation: J Clin Oncol. 2011 Aug 1;29(22):2972-7
references.pmid: 21730270
references.citation: Nature. 2012 Jun 28;486(7404):537-40
references.pmid: 22722843
references.citation: J Thorac Oncol. 2013 Apr;8(4):461-8
references.pmid: 23486266
references.citation: J Clin Oncol. 2012 May 1;30(13):1438-46
references.pmid: 22393100
references.citation: J Thorac Oncol. 2011 Feb;6(2):244-85
references.pmid: 21252716
references.citation: Hum Pathol. 1999 Dec;30(12):1459-63
references.pmid: 10667424
references.citation: Histopathology. 2011 Dec;59(6):1081-9
references.pmid: 22175888
references.citation: BMC Cancer. 2011 Mar 07;11:93
references.pmid: 21385341
references.citation: J Thorac Oncol. 2010 Jul;5(7):964-9
references.pmid: 20512074
references.citation: Int J Cancer. 2008 Dec 1;123(11):2480-6
references.pmid: 18785203
references.citation: J Thorac Oncol. 2011 Sep;6(9):1496-504
references.pmid: 21642859
references.citation: Cancer Res. 2012 Oct 1;72(19):4875-82
references.pmid: 23002210
references.citation: Am J Surg Pathol. 2008 Jun;32(6):810-27
references.pmid: 18391747
references.citation: Am J Surg Pathol. 2010 Aug;34(8):1155-62
references.pmid: 20551825
references.citation: Hum Pathol. 2001 Jun;32(6):583-9
references.pmid: 11431712
references.citation: Mod Pathol. 2007 Jul;20(7):729-33
references.pmid: 17464318
references.citation: Med Mol Morphol. 2013 Jun;46(2):114-21
references.pmid: 23471758
references.citation: J Pathol. 2007 Jul;212(3):287-94
references.pmid: 17534846
references.citation: Am J Clin Pathol. 2011 May;135(5):783-9
references.pmid: 21502435
references.citation: Lancet Oncol. 2013 Jan;14(1):38-47
references.pmid: 23200175
references.citation: N Engl J Med. 2012 Mar 8;366(10):883-892
references.pmid: 22397650
references.citation: Am J Surg Pathol. 1994 Dec;18(12):1224-32
references.pmid: 7977945
references.citation: BMC Cancer. 2008 May 21;8:142
references.pmid: 18495026
references.citation: Cell. 1990 Jun 1;61(5):759-67
references.pmid: 2188735
references.citation: Mod Pathol. 2011 May;24(5):729-38
references.pmid: 21336262
references.citation: Clin Lung Cancer. 2006 Jul;8(1):30-8
references.pmid: 16870043
references.citation: Am J Pathol. 1994 Feb;144(2):303-9
references.pmid: 8311114
references.citation: Mod Pathol. 2004 May;17(5):538-46
references.pmid: 14990969
references.citation: Oncotarget. 2012 May;3(5):546-58
references.pmid: 22643842
references.citation: J Thorac Oncol. 2012 Feb;7(2):323-30
references.pmid: 22237264
references.citation: Sci Transl Med. 2013 Oct 30;5(209):209ra153
references.pmid: 24174329
references.citation: Mod Pathol. 2007 Sep;20(9):967-73
references.pmid: 17618248
references.citation: Pathol Int. 2000 Jan;50(1):52-6
references.pmid: 10692178
references.citation: Cancer Res. 1994 Nov 15;54(22):5811-5
references.pmid: 7954406