Loss of heterozygosity in endometrial carcinoma.

Inactivation of a tumor suppressor gene typically occurs in two steps, thus fulfilling Knudson hypothesis. One "hit" is frequently a point mutation or a small deletion. The other alteration is usually a large genomic loss of part of a gene, or even part of a chromosome, or the whole chromosome. However, it is not clear which of these two events occurs first. Loss of heterozygosity (LOH) analysis allows the identification of one of the 2 hits. Although microsatellite polymerase chain reaction is the technique most frequently used to assess LOH, other different approaches can also be used. The LOH can also be assessed by restriction fragment length polymorphism analysis, single strand conformation polymorphism analysis, oligonucleotide microarrays capable to simultaneously determine the genotype of thousands of single-nucleotide polymorphism (single-nucleotide polymorphism arrays), comparative genomic hybridization, multiplex amplification and probe hybridization, and multiplex ligation-dependent probe amplification. In this article, the authors review the results obtained with molecular analysis of LOH in the understanding of development and progression of endometrial carcinoma. Particular attention is given to: (1) the presence of widespread LOH in nonendometrioid carcinoma, probably reflecting the existence of chromosomal instability; and (2) specific LOH patterns associated with some clinicopathologic features.

Nuclear factor-kappaB activation is associated with somatic and germ line RET mutations in medullary thyroid carcinoma.

The nuclear factor-kappaB (NF-kappaB) family of transcription factors regulates a wide variety of cellular processes including cell growth, differentiation, and apoptosis. NF-kappaB has been shown to be activated through several signaling pathways that involve growth factor receptors. The aim of the study was to assess the immunohistochemical expression of members of the NF-kappaB family and the putative targets of NF-kappaB in a series of medullary thyroid carcinomas (MTCs), in correlation with RET mutational status. A tissue microarray was constructed from paraffin-embedded blocks of 48 MTCs (13 familial, 35 sporadic) previously evaluated for germ line and somatic RET mutations. Immunohistochemical evaluation included members of the NF-kappaB (p50, p65, p52, c-Rel, RelB) family, as well as putative targets of NF-kappaB such as Flip, Bcl-xL, and cyclin D1. Nuclear immunostaining for members of NF-kappaB was frequent in MTCs (p50, 19%; p65, 68%; p52, 86.6%; c-Rel, 75%; RelB, 36%). MTCs with germ line or somatic RET mutations (29 cases) showed NF-kappaB nuclear translocation (particularly of p65, P = .035) more frequently than MTCs without RET mutations (19 cases). Immunostaining for putative targets of NF-kappaB showed a significant statistical association between p65 and Bcl-xL (P = .024). In addition, Bcl-xL expression was statistically higher in the tumors with exon 16 RET mutation in comparison with those with exon 10 and 11 RET mutations or wild-type RET (P = .002). Moreover, the significance of RETsignaling in NF-kappaB activation was evaluated in the RET-mutated TT cell line. TT cells were infected with lentiviruses carrying short hairpin RNA to knock down RET expression, and NF-kappaB activity was assessed by luciferase reporter assays. Silencing of RET in the TT cell line produced a significant decrease in NF-kappaB activation and reduction in ERK1/2. The results suggest that the NF-kappaB is frequently activated in MTCs. The results also support the hypothesis that RET activation by somatic or germ line mutations may be responsible for NF-kappaB activation in MTCs.