CASE REPORTS in HAEMATOLOGY (Paper co-edited with the European LeukemiaNet)

Amplification of the MET/7q31 gene in a patient with myelodysplastic syndrome

Written	2016-06	Brandon S. Twardy, Deborah Schloff, Anwar N. Mohamed
		Cytogenetics Laboratory, Pathology Department, Wayne State University School of Medicine and Detroit Medical Center, Detroit MI, USA

Clinics

Age and sex :	52 year(s) old male patient.
Previous History :	no preleukemia
	no previous malignant disease
	no inborn condition of note

Organomegaly : no hepatomegaly ; no splenomegaly ; no enlarged lymph nodes ; no central nervous system involvement

Blood

WBC : 1.7 x 109/L ; Hb : 11.3 g/dL ; platelets : 50 x 109/L; blasts : Peripheral % (blood smear showed pancytopenia with 1 circulating myeloblasts.).

Bone marrow : Bone marrow biopsy was hypercellular (90%) with dysmegakaryopoiesis, dysgranulopiesis, markedly increased erythrogenesis with dysplastic features, and 10% myeloblasts with no Auer rods. No metastatic tumor or granuloma

Cyto pathology classification

Phenotype : Findings were consistent with myelodysplastic syndrome, best classified as refractory anemia with excess blasts (RAEB-2)

Immunophenotype : Flow cytometric analysis of the bone marrow aspirate detected 5% myeloblasts with dim expression of CD45. Blasts were positive for CD13, CD33, CD34, CD117, CD38, and HLA-DR. Erythroid precursors constituted 55% of the gated cells and were positive for CD36 and glycophorin A.

Rearranged Ig Tcr : t

Electron microscopy : Not performed

Precise diagnosis : Myelodysplastic syndrome, RAEB-2

Survival

Date of diagnosis: 01-2015

Treatment : In January 2015, the patient received high dose Ara-C chemotherapy followed by multiple doses of Vidaza. In December 2015, he underwent allogeneic peripheral blood stem cell transplant from a matched-unrelated female donor.

Complete remission : None

Treatment related death : +

Status : Dead

Survival : 15 month(s)

Karyotype

Sample : Bone marrow aspirate ; culture time : 24 h, ours unstimulated culture; 48 hours with 10% conditioned media ; banding : G- banding

Results : clone 2 46,XY,del(5)(q13q33),add(20)(q11.2)[3]

Other molecular cytogenetics results : Fluorescence in situ hybridization (FISH) was performed on the pellet from the harvested bone marrow specimen using the MDS panel DNA probes that included D5S23:D5S721/5p15.2, EGR1/5q31, D7Z1/CEP-7, D7S486/7q31, D8Z2/CEP-8, and D20S108/20q12. Results of FISH revealed an amplification the D7S486 /7q31 region in approximately 60% of cells (>6 copies per nucleus), and deletions of EGR1/5q and 20q12 in 10% of cells. In addition, we investigated the status of MET as a candidate oncogene for the amplified 7q31 region. Accordingly, the LSI MET SpectrumRed probe along with CEP-7 SpectrumGreen as a control were hybridized on the same specimen. The LSI MET probe is approximately 456 kb and contains the entire MET gene on chromosome 7q31.2. The hybridization revealed amplification of the MET gene with only 2 signals/copies for the control CEP-7 (Figure 2). All FISH probes were purchased from Abbott Molecular, Downers Grove IL, USA.

Figure 1: G-banded karyotype at time of diagnosis showing multiple abnormalities including a ring chromosome, and other unbalanced aberrations

Figure 2: FISH with LSI MET SepectrumRed probe showing multiple red signals for MET while two green signals for centromere 7, On metaphase cells the red signals hybridized to the ring chromosome.

Comments

Gene amplification in leukemia is relatively rare, mostly reported for the MLL and CMYC oncogenes. However, MET amplification has not been reported in leukemia. Here, we report the first case of MDS with MET amplification in the form of a ring chromosome. The patient was a 52-year-old male who initially presented with shortness of breath and fatigue during the latter part of December 2014. A CBC was performed at this time and revealed marked leukopenia, anemia, and thrombocytopenia. Upon arrival to our facility, assessment of bone marrow biopsy and aspirate revealed dysplastic changes consistent with the diagnosis of myelodysplastic syndrome (MDS), classified as RAEB-2. Chromosomal analysis at that time revealed at least two unrelated clones; the dominant clone presented with multiple unbalanced chromosomal rearrangements, and extreme karyotypic heterogeneity. However, the most notable chromosomal aberrations were additional genetic material on chromosomes 7q, 16p and 19p, a large ring that appeared to be derived from chromosome 7, and an inversion of Xp. Clone 2, was a minor clone and showed 5q and 20q deletions, the classic abnormalities for MDS. FISH demonstrated deletions of EGR1/5q31 and 20q12 in 8-12% of cells, but unexpectedly amplification of the 7q31 region was noticed in 60% of cells. The FISH probe, D7S486/7q31, spans a region of 306kb, which contains several tumor suppressor genes such as MDFIC, TES, CAV1. The closest candidate oncogene to D7S486 region at 7q31 is the MET gene. Therefore, MET/7q31.2 probe was hybridized to the same specimen that confirmed an amplification of MET oncogene. In metaphase cells, the amplified signals are located on the ring chromosome which lacks a centromere 7 signal (Figure 2). The MET gene encodes a tyrosine kinase receptor for the hepatocyte growth factor (HGF). Whereas the physiological expression of MET is essential for wound healing and embryonic development, aberrant overexpression of MET results in up-regulation of cell proliferation, motility, migration, invasion, and survival. MET MET activating mutations and gene amplification have been identified in a variety of solid tumors including, gastric, pharynx, colon, lung, and breast cancer. Further studies have shown that inhibition of MET signaling pathways has led to inhibition of growth, migration and invasion. For these reasons MET has become a valuable target for cancer therapy and several drugs targeting MET and its ligand HGF are being evaluated in clinical trials in various cancers. The MET gene is also overexpressed in hematological malignancies. The most recent studies on multiple myeloma showed that the HGF/MET pathway is constitutively active in plasma cells of myeloma patients and it confers multidrug resistance. These findings were also true for acute myeloid leukemia (AML). Studies of samples taken from AML patients and cell lines revealed that MET is activated in leukemic cells as a result of aberrant autocrine signaling by HGF, and inhibition of this autocrine activation loop would inhibit the growth and survival of these cells. Other genes of significance within the region of chromosome 7q31 include MDFIC, TFEC, TES, CAV-1, CAV-2, and ST7. These genes have been implicated in various malignancies but their role has not yet been fully elucidated. TES, CAV-1, CAV-2, and ST7 are considered candidate tumor suppressors implicated in numerous malignancies. MDFIC, also known as HIC, is frequently deleted in myeloid malignancies. TFEC is a member of the microphthalmia family of transcription factors whose dysregulation may have a role in renal cell carcinoma, melanoma, and sarcoma. Despite aggressive therapy, our patient never achieved remission, and he died from disease progression shortly after transplant. The complex karyotype as well as MET amplification certainly contributes to the dismal sequence of the disease. Therapeutic agents targeting the MET pathway may help improve patient survival.

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Citation

This paper should be referenced as such :

Twardy BS, Schloff D, Mohamed AN

Amplification of the MET/7q31 gene in a patient with myelodysplastic syndrome

Atlas Genet Cytogenet Oncol Haematol. in press

On line version : http://AtlasGeneticsOncology.org/Reports/METampTwardyID100086.html

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indexed on : Fri Jun 30 11:26:28 CEST 2017

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