LOH of the MEN1 gene in TSH-secreting pituitary adenomas
6. Landis C., Masters S.B., Spada A., Pace A.M.,
Bourne H.R., Vallar L.
(26, 27), may inhibit the transcription of the sec-
ond copy of the MEN1 gene. However, Prezant et
al. addressed this point by studying MEN1 mRNA
expression in pituitary tumors which was found to
be normal, and Asa et al. (28) demonstrated by
competitive reverse transcription-PCR that there
was a lack of menin down-regulation in the major-
ity of tumors with LOH on 11q13; 3) another
unidentified tumor suppressor gene may be locat-
ed at the MEN1 locus; 4) other factors (growth fac-
tors, oncogenes, tumor suppressor genes, hy-
pophysiotropic factors) different from MEN1 may
be altered.
However, over the past years several studies have
been performed, but they failed to identify intrinsic
genetic defects causing the initiation and the pro-
gression of TSH-omas. This issue remains still un-
explained probably because a complicate interac-
tion of factors and multiple steps is required for the
pathogenesis of these tumors. Our results con-
tribute to exclude menin as the unique gene re-
sponsible for such a complex process.
GTPase inhibiting mutations activate the alpha chain
of Gs and stimulate adenylyl cyclase in human pitu-
itary tumors.
Nature 1989, 340: 692-696.
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Two G protein oncogenes in human endocrine tu-
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ACKNOWLEDGMENTS
J. Clin. Endocrinol. Metab. 1996, 81: 1134-1140.
This work was partially supported by the current research from
Ospedale Maggiore IRCCS, Milan, and by MURST (9806243848),
Rome, Italy.
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Pit1/GHF-1 expression in pituitary adenomas. Fur-
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