Blood, Vol. 95 No. 8 (April 15), 2000:
pp. 2728-2729
CORRESPONDENCE
 |
To the Editor: |
Nucleotide insertions and deletions within the homopolymeric runs
of adenines and thymidines of BCL10 cDNAs in normal
peripheral blood leukocytes
The BCL10 gene was isolated from the
breakpoint region of the t(1;14) in mucosa-associated lymphoid tissue
(MALT) lymphomas,1,2 and BCL10 was found to be a
cellular homologue of the equine herpesvirus-2 E10 gene because
both contain an amino-terminal caspase recruitment domain,
which is homologous to that seen in several apoptotic molecules.1,2 In functional assays, wild-type BCL10 was
found to induce apoptosis. It is noteworthy that BCL10 in
t(1;14)-bearing MALT lymphomas exhibits a variety of truncating
mutations,1,2 and that truncated BCL10 fails to induce
apoptosis and exhibits a transforming activity. Similar mutations were
also identified in a subset of follicular lymphoma (FCL) and other
tumor cell lines with a loss of heterozygosity in
chromosome 1p22.1 However, several recent studies,
including ours, have reported that BCL10 mutations are
rare in various human tumors, thus raising questions regarding
the pathological role of BCL10 as a tumor suppressor gene
in these tumors.3-9
Recently, Dyer et al suggested that at least some of the discrepancies
between their data and those reported by others can be ascribed to
their use of cDNA rather than genomic DNA.10 They found
that nucleotide insertions and deletions within homopolymeric runs of 8 adenines and 7 thymidines are common in BCL10 cDNAs. In
order to investigate whether BCL10 abnormalities occur at
the RNA level, we searched for somatic mutations in BCL10 cDNAs
by means of reverse transcription polymerase chain
reaction (RT-PCR) and sequencing analyses in 3 normal
peripheral blood leukocytes (PBLs) and 3 FCL samples. The pathological
diagnosis was established in accordance with the revised
European-American classification of lymphoid neoplasms (REAL). The
coding region of BCL10 cDNAs (702 bp) was amplified by using
Taq DNA polymerase with high fidelity and subcloned into the plasmid
vectors. The inserts of 5 independent BCL10 cDNA clones from
each of the normal PBLs or lymphoma samples were sequenced in both
directions using an ABI PRISM Dye Terminator Cycle Sequencing Ready
Reaction Kit (Perkin Elmer, Foster City, CA) on an ABI 373 DNA
automated sequencer (Applied Biosystems, Foster City, CA). The spectrum
of BCL10 cDNA abnormalities is summarized in the
Table. These include multiple point
mutations and nucleotide insertions or deletions within
homopolymeric runs of adenines and thymidines. The spectrum of multiple
BCL10 cDNA abnormalities is similar to those reported by others
in certain tumors.1,2,10 It is possible that some of these
multiple point mutations may be due to PCR or cloning artifacts. In our study, however, nucleotide insertions or deletions within homopolymeric runs, resulting in truncation of BCL10, were identified in the same 8 out of 15 clones both from normal PBLs and from FCL samples (Table).
The possibility that these truncation-type abnormalities are due to PCR
or cloning artifacts is minute, because only 4 out of 500 genomic DNA
sequences were found to exhibit such insertions or
deletions10 and our FCL samples exhibited an apparently
normal germ-line DNA.9 Finally, a novel 118 bp deletion in
exon 3 of BCL10 was identified in one FCL sample. It is not
clear if this alteration contributes to the pathogenesis of FCL, but in the light of the fact that only one clone carried such a deletion, it
is doubtful whether this deletion has any functional significance.
In summary, our results strongly suggest that BCL10 may
undergo a novel posttranscriptional RNA modification even in normal PBL cells and that BCL10 cDNA abnormalities are not
necessarily associated with the molecular pathogenesis of a wide
range of human tumors.
Hidenobu Takahashi
Yumiko Maeda
Masao Seto
Yoshitaka Hosokawa
Laboratory of Molecular Medicine, Aichi Cancer Center Research
Institute
Nagoya, Japan
| |
References |
1.
Willis TG, Jadayel DM, Du M-Q, et al.
Bcl10 is involved in t(1;14)(p22;q32) of MALT B-cell lymphoma and mutated in multiple tumor types.
Cell.
1999;96:35-45[Medline]
[Order article via Infotrieve].
2.
Zhang Q, Siebert R, Yan M, et al.
Inactivating mutations and overexpression of BCL10, caspase recruitment domain-containing gene, in MALT lymphoma with t(1;14)(p22;q32).
Nat Genet.
1999;22:63-68[Medline]
[Order article via Infotrieve].
3.
Fakruddin JM, Chaganti RSK, Murty VVVS.
Lack of BCL10 mutations in germ cell tumors and B cell lymphomas.
Cell.
1999;97:683-688[Medline]
[Order article via Infotrieve].
4.
Apostolou S, Rienzo AD, Murthy SS, Jhanwar SC, Testa JR.
Absence of BCL10 mutations in human malignant mesothelioma.
Cell.
1999;97:684-686[Medline]
[Order article via Infotrieve].
5.
Gill S, Broni J, Jefferies S, et al.
BCL10 is rarely mutated in human prostate, carcinoma, small-cell lung cancer, head and neck tumours, renal carcinomas.
Br J Cancer.
1999;80:1565-1568[Medline]
[Order article via Infotrieve].
6.
Stone JG, Rowan AJ, Tomlison IPM, Houlston RS.
Mutations in Bcl10 are very rare in colorectal cancer.
Br J Cancer.
1999;80:1569-1570[Medline]
[Order article via Infotrieve].
7.
Schothorst EM, Mohkamsing S, van Gurp RJHLM.
Oosterhuis JW, van der Saag PT, Looijenga LHJ. Lack of BCL10 mutations in testicular germ cell tumours and derived cell lines.
Br J Cancer.
1999;80:1571-1574[Medline]
[Order article via Infotrieve].
8.
Lambers AR, Gumbs C, Ali S, et al.
BCL10 is not a target for frequent mutation in human carcinomas.
Br J Cancer.
1999;80:1575-1576[Medline]
[Order article via Infotrieve].
9.
Takahashi H, Hosokawa Y, Suzuki R, Morishima Y, Nakamura S, Seto M.
Infrequent BCL10 mutations in B-cell non-Hodgkin's lymphomas.
Jpn J Cancer Res.
1999;90:1316-1320[Medline]
[Order article via Infotrieve].
10.
Dyer MJS, Price HP, Jadayel DM, et al.
In response to Fakruddin et al and Apostolou et al.
Cell.
1999;97:686.
