Routine molecular screening of patients with colorectal adenocarcinoma for the Lynch syndrome identified mutations in patients and their family members that otherwise would not have been detected. These data suggest that the effectiveness of screening with immunohistochemical analysis of the mismatch-repair proteins would be similar to that of the more complex strategy of genotyping for microsatellite instability.

A B S T R A C T PurposeIdentifying individuals with Lynch syndrome (LS) is highly beneficial. However, it is unclear whether microsatellite instability (MSI) or immunohistochemistry (IHC) should be used as the screening test and whether screening should target all patients with colorectal cancer (CRC) or those in high-risk subgroups. Patients and MethodsMSI testing and IHC for the four mismatch repair proteins was performed on 500 tumors from unselected patients with CRC. If either MSI or IHC was abnormal, complete mutation analysis for the mismatch repair genes was performed. ResultsAmong the 500 patients, 18 patients (3.6%) had LS. All 18 patients detected with LS (100%) had MSI-high tumors; 17 (94%) of 18 patients with LS were correctly predicted by IHC. Of the 18 probands, only eight patients (44%) were diagnosed at age younger than 50 years, and only 13 patients (72%) met the revised Bethesda guidelines. When these results were added to data on 1,066 previously studied patients, the entire study cohort (N ϭ 1,566) showed an overall prevalence of 44 of 1,566 patients (2.8%; 95% CI, 2.1% to 3.8%) for LS. For each proband, on average, three additional family members carried MMR mutations. ConclusionOne of every 35 patients with CRC has LS, and each has at least three relatives with LS; all of whom can benefit from increased cancer surveillance. For screening, IHC is almost equally sensitive as MSI, but IHC is more readily available and helps to direct gene testing. Limiting tumor analysis to patients who fulfill Bethesda criteria would fail to identify 28% (or one in four) cases of LS.

Endometrial cancer is the most common cancer in women with Lynch syndrome. The identification of individuals with Lynch syndrome is desirable because they can benefit from increased cancer surveillance. The purpose of this study was to determine the feasibility and desirability of molecular screening for Lynch syndrome in all endometrial cancer patients. Unselected endometrial cancer patients (N = 543) were studied. All tumors underwent microsatellite instability (MSI) testing. Patients with MSI-positive tumors underwent testing for germ line mutations in MLH1, MSH2, MSH6, and PMS2. Of 543 tumors studied, 118 (21.7%) were MSI positive (98 of 118 MSI high and 20 of 118 MSI low). All 118 patients with MSI-positive tumors had mutation testing, and nine of them had deleterious germ line mutations (one MLH1, three MSH2, and five MSH6). In addition, one case with an MSI-negative tumor had abnormal MSH6 immunohistochemical staining and was subsequently found to have a mutation in MSH6. Immunohistochemical staining was consistent with the mutation result in all seven truncating mutation-positive cases but was not consistent in two of the three missense mutation cases. We conclude that in central Ohio, at least 1.8% (95% confidence interval, 0.9-3.5%) of newly diagnosed endometrial cancer patients had Lynch syndrome. Seven of the 10 Lynch syndrome patients did not meet any published criteria for hereditary nonpolyposis colorectal cancer, and six of them were diagnosed at age >50. Studying all endometrial cancer patients for Lynch syndrome using a combination of MSI and immunohistochemistry for molecular prescreening followed by gene sequencing and deletion analysis is feasible and may be desirable. (Cancer Res 2006; 66(15): 7810-7)

To determine whether TP53 gene dosage affects the transcriptional regulation of target genes, we performed oligonucleotide-array gene expression analysis by using human cells with wild-type p53 (p53 ؉/؉), or with one (p53 ؉/؊), or both (p53 ؊/؊) TP53 alleles disrupted by homologous recombination. We identified 35 genes whose expression is significantly correlated to the dosage of TP53. These genes are involved in a variety of cellular processes including signal transduction, cell adhesion, and transcription regulation. Several of them are involved in neurogenesis and neural crest migration, developmental processes in which p53 is known to play a role. Motif search analysis revealed that of the genes highly expressed in p53 ؉/؉ and ؉/؊ cells, several contain a putative p53 consensus binding site (bs), suggesting that they could be directly regulated by p53. Among those genes, we chose CSPG2 (which encodes versican) for further study because it contains a bona fide p53 bs in its first intron and its expression highly correlates with TP53 dosage. By using in vitro and in vivo assays, we showed CSPG2 to be directly transactivated by p53. In conclusion, we developed a strategy to demonstrate that many genes are affected by TP53 gene dosage for their expression. We report several candidate genes as potential downstream targets of p53 in nonstressed cells. Among them, CSPG2 is validated as being directly transactivated by p53. Our method provides a useful tool to elucidate additional mechanisms by which p53 exerts its functions.T he tumor suppressor protein p53 is a transcription factor involved in important cellular processes such as cell cycle checkpoint regulation, DNA damage response and repair, apoptosis and senescence (reviewed in ref. 1). The best characterized biochemical function of p53 is its sequence-specific transactivation activity. A consensus binding site (bs) has been defined and contains two copies of the 10 base pair motif RRRC(A͞T)(T͞ A)GYYY (R ϭ A or G; Y ϭ C or T) separated by 0-13 base pairs (2) and is found in the regulatory regions of target genes. Recent studies using global approaches to identify p53-regulated genes have identified numerous putative target genes that may be directly or indirectly regulated by p53 (3, 4). These studies have revealed heterogeneity of the gene expression changes induced by p53 overexpression or by p53 activation after genotoxic insults, in that the genes transcriptionally regulated by p53 vary depending on the cell type, inducing agent, and amount of p53 in the cells.p53 Ϫ/Ϫ mice develop tumors at a very early age and succumb by 10 months of age. Heterozygous mice (p53 ϩ/Ϫ) have a 50% chance of developing tumors by 18 months of age, and almost all are dead by 2 years of age (5). About half of the tumors that develop in p53 ϩ/Ϫ mice do not show loss of the wild-type (wt) allele (6, 7).The wt allele is retained and encodes a functional protein able to bind DNA and activate transcription of target genes (7). In humans, germ-line TP53 mutations account for 70-85% of ...