Gains of a gene due to DNA polyploidy versus amplification of the specific locus are distinct molecular alterations in tumors.
OBJECTIVE:
We quantified copy number gains of ALK gene due to unspecific polyploidy versus amplifications of the specific locus in a series of non-small cell lung cancers.
METHODS:
The locus specific ALK copy (LSI) number status was evaluated in 205 cases by FISH. Ratio LSI ALK copy number corrected for control probes CEP2, CEP3 and CEP17 (CEPs) was scored. Amplification of the specific ALK locus was defined when ratio set to ≥ 2 while polyploidy was interpreted when the increase in gene copy resulted < 2 in ratio (LSI/control CEPs).
RESULTS:
Twenty one cases (10.2%) showed ≥ 8 ALK signals, 68 cases(33.2%) 3-7 signals and 116 cases (56.6%) a mean of 2 signals. Only 2/21 cases of the cohort harboring ≥ 8 signals showed a ratio ≥ 2 after CEPs correction interpretable as amplified, showing numerous doubled fluorescent spots. All the remaining cases showed a mirrored number of fluorescent spots per each CEPs, interpretable as polyploidy.
CONCLUSION:
We detected a high prevalence of ALK gene copy number usually due to polyploidy rather than ALK locus amplification, the latter visible prevalently as double minutes.
KwakE.L., BangY.J., CamidgeD.R., et al., Anaplastic lymphoma kinase inhibition in non-small-cell lung cancer, N Engl J Med. 363 (2010), 1693-1703.
2.
CamidgeD.R., SkokanM., KiatsimkulP., et al., Native and rearranged ALK copy number and rearranged cell count in non-small cell lung cancer: implications for ALK inhibitor therapy, Cancer. 119 (2013), 3968-3975.
3.
CamidgeD.R., TheodoroM., MaxsonD.A., et al., Correlations between the percentage of tumor cells showing an anaplastic lymphoma kinase (ALK) gene rearrangement, ALK signal copy number, and response to crizotinib therapy in ALK fluorescence in situ hybridization-positive nonsmall cell lung cancer, Cancer. 118 (2012), 4486-4494.
4.
SalidoM., PijuanL., Martinez-AvilesL., et al., Increased ALK gene copy number and amplification are frequent in non-small cell lung cancer, J Thorac Oncol. 6 (2011), 21-27.
5.
DoebeleR.C., PillingA.B., AisnerD.L., et al., Mechanisms of resistance to crizotinib in patients with ALK gene rearranged non-small cell lung cancer, Clin Cancer Res. 18 (2012), 1472-1482.
6.
KatayamaR., KhanT.M., BenesC., et al., Therapeutic strategies to overcome crizotinib resistance in non-small cell lung cancers harboring the fusion oncogene EML4-ALK, Proc Natl Acad Sci U S A. 108 (2011), 7535-7540.
7.
KimS., KimT.M., KimD.W., et al., Heterogeneity of genetic changes associated with acquired crizotinib resistance in ALK-rearranged lung cancer, J Thorac Oncol. 8 (2013), 415-422.
8.
BorelF., LohezO.D., LacroixF.B., MargolisR.L., Multiple centrosomes arise from tetraploidy checkpoint failure and mitotic centrosome clusters in p53 and RB pocket protein-compromised cells, Proc Natl Acad Sci U S A. 99 (2002), 9819-9824.
9.
CowardJ., HardingA., Size Does Matter: Why Polyploid Tumor Cells are Critical Drug Targets in the War on Cancer, Front Oncol. 4 (2014), 123.
10.
GebhartE., BruderleinS., TulusanA.H., von MaillotK., BirkmannJ., Incidence of double minutes, cytogenetic equivalents of gene amplification, in human carcinoma cells, Int J Cancer. 34 (1984), 369-373.
11.
TravisW., BrambillaE., BurkeA., MarxA., NicholsonA., WHO Classification of Tumours of the Lung, Pleura, Thymus and Heart. Lyon: IARC Press; 2015.
TestaJ.R., SiegfriedJ.M., Chromosome abnormalities in human non-small cell lung cancer, Cancer Res. 52 (1992), 2702s-2706s.
14.
ShenH., GaoW., WuY.J., QiuH.R., ShuY.Q., Multicolor fluorescence in situ hybridization and comparative genomic hybridization reveal molecular events in lung adenocarcinomas and squamous cell lung carcinomas, Biomed Pharmacother. 63 (2009), 396-403.
15.
LukC., TsaoM.S., BayaniJ., ShepherdF., SquireJ.A., Molecular cytogenetic analysis of non-small cell lung carcinoma by spectral karyotyping and comparative genomic hybridization, Cancer Genet Cytogenet. 125 (2001), 87-99.
16.
TaguchiT., ZhouJ.Y., FederM., LitwinS., Klein-SzantoA.J., TestaJ.R., Detection of aneuploidy in interphase nuclei from non-small cell lung carcinomas by fluorescence in situ hybridization using chromosome-specific repetitive DNA probes, Cancer Genet Cytogenet. 89 (1996), 120-125.
17.
PelosiG., GaspariniP., CavazzaA., et al., Multiparametric molecular characterization of pulmonary sarcomatoid carcinoma reveals a nonrandom amplification of anaplastic lymphoma kinase (ALK) gene, Lung Cancer. 77 (2012), 507-514.
18.
GebhartE., Double minutes, cytogenetic equivalents of gene amplification, in human neoplasia-a review, Clin Transl Oncol. 7 (2005), 477-485.
19.
NielsenJ.L., WalshJ.T., DegenD.R., DrabekS.M., McGillJ.R., von HoffD.D., Evidence of gene amplification in the form of double minute chromosomes is frequently observed in lung cancer, Cancer Genet Cytogenet. 65 (1993), 120-124.
20.
BrunelliM., BriaE., NottegarA., et al., True 3q chromosomal amplification in squamous cell lung carcinoma by FISH and aCGH molecular analysis: impact on targeted drugs, PLoS One. 7 (2012), e49689.
21.
JiangL., YangH., HeP., et al., Improving Selection Criteria for ALK Inhibitor Therapy in Non-Small Cell Lung Cancer: A Pooled-Data Analysis on Diagnostic Operating Characteristics of Immunohistochemistry, Am J Surg Pathol. 40 (2016), 697-703.
22.
KimE.K., KimS., ALK gene copy number gain and immunohistochemical expression status using three antibodies in neuroblastoma, Pediatr Dev Pathol. (2016).
23.
CanuteG.W., LongoS.L., LongoJ.A., WinfieldJ.A., NevaldineB.H., HahnP.J., Hydroxyurea accelerates the loss of epidermal growth factor receptor genes amplified as double-minute chromosomes in human glioblastoma multiforme, Neurosurgery. 39 (1996), 976-983.
24.
YuanY., LiaoY.M., HsuehC.T., MirshahidiH.R., Novel targeted therapeutics: inhibitors of MDM2, ALK and PARP, J Hematol Oncol. 4 (2011), 16.
