Pharmacogenomics of selective serotonin reuptake inhibitor treatment for major depressive disorder: genome-wide associations and functional genomics.

A genome-wide association (GWA) study of treatment outcomes (response and remission) of selective serotonin reuptake inhibitors (SSRIs) was conducted using 529 subjects with major depressive disorder. While no SNP associations reached the genome-wide level of significance, 14 SNPs of interest were identified for functional analysis. The rs11144870 SNP in the riboflavin kinase (RFK) gene on chromosome 9 was associated with 8-week treatment response (odds ratio (OR)=0.42, P=1.04 × 10⁻6). The rs915120 SNP in the G protein-coupled receptor kinase 5 (GRK5) gene on chromosome 10 was associated with 8-week remission (OR=0.50, P=1.15 × 10⁻5). Both SNPs were shown to influence transcription by a reporter gene assay and to alter nuclear protein binding using an electrophoretic mobility shift assay. This report represents an example of joining functional genomics with traditional GWA study results derived from a GWA analysis of SSRI treatment outcomes. The goal of this analytical strategy is to provide insights into the potential relevance of biologically plausible observed associations.

Evidence for a prostate cancer susceptibility locus on the X chromosome.

Over 200,000 new prostate cancer cases are diagnosed in the United States each year, accounting for more than 35% of all cancer cases affecting men, and resulting in 40,000 deaths annually. Attempts to characterize genes predisposing to prostate cancer have been hampered by a high phenocopy rate, the late age of onset of the disease and, in the absence of distinguishing clinical features, the inability to stratify patients into subgroups relative to suspected genetic locus heterogeneity. We previously performed a genome-wide search for hereditary prostate cancer (HPC) genes, finding evidence of a prostate cancer susceptibility locus on chromosome 1 (termed HPC1; ref. 2). Here we present evidence for the location of a second prostate cancer susceptibility gene, which by heterogeneity estimates accounts for approximately 16% of HPC cases. This HPC locus resides on the X chromosome (Xq27-28), a finding consistent with results of previous population-based studies suggesting an X-linked mode of HPC inheritance. Linkage to Xq27-28 was observed in a combined study population of 360 prostate cancer families collected at four independent sites in North America, Finland and Sweden. A maximum two-point lod score of 4.60 was observed at DXS1113, theta=0.26, in the combined data set. Parametric multipoint and non-parametric analyses provided results consistent with the two-point analysis. Significant evidence for genetic locus heterogeneity was observed, with similar estimates of the proportion of linked families in each separate family collection. Genetic mapping of the locus represents an important initial step in the identification of an X-linked gene implicated in the aetiology of HPC.

Major histocompatibility complex class I-recognizing receptors are disease risk genes in rheumatoid arthritis.

Rheumatoid arthritis (RA) is a heterogeneous syndrome of which a subset of patients develops vascular inflammation. The genetic determinants that confer risk for rheumatoid vasculitis are not known, but patients with vascular complications are known to have an expansion of CD4(+)CD28(null) T cells, a cell population potentially involved in endothelial damage. CD4(+)CD28(null) T cell clones isolated from RA patients with vasculitis were found to express killer cell immunoglobulin-like receptors (KIRs) with the stimulatory KIR2DS2 often present in the absence of opposing inhibitory receptors with related specificities. To test the hypothesis that the KIR2DS2 gene is involved in the development of vasculitis, association studies were performed. The KIR2DS2 gene was significantly enriched among patients with rheumatoid vasculitis compared with normal individuals (odds ratio 5.56, P = 0.001) and patients with RA but no vasculitis (odds ratio 7.96, P = 0.001). Also, the distribution of human histocompatibility leukocyte antigen (HLA)-C, the putative ligand for KIRs, was significantly different in patients with rheumatoid vasculitis in comparison with the control populations. These data suggest that HLA class I-recognizing receptors and HLA class I genes are genetic risk determinants that modulate the pattern of RA expression. Specifically, KIR2DS2 in conjunction with the appropriate HLA-C ligand may have a role in vascular damage by regulating CD4(+)CD28(null) T cells.

Microsatellite instability in cancer of the proximal colon.

Colorectal tumor DNA was examined for somatic instability at (CA)n repeats on human chromosomes 5q, 15q, 17p, and 18q. Differences between tumor and normal DNA were detected in 25 of the 90 (28 percent) tumors examined. This instability appeared as either a substantial change in repeat length (often heterogeneous in nature) or a minor change (typically two base pairs). Microsatellite instability was significantly correlated with the tumor's location in the proximal colon (P = 0.003), with increased patient survival (P = 0.02), and, inversely, with loss of heterozygosity for chromosomes 5q, 17p, and 18q. These data suggest that some colorectal cancers may arise through a mechanism that does not necessarily involve loss of heterozygosity.

SLC6A4 variation and citalopram response.

The influence of genetic variations in SLC6A4 (serotonin transporter gene) on citalopram treatment of depression using the Sequenced Treatment to Relieve Depression (STAR*D) sample was assessed. Of primary interest were three previously studied polymorphisms: 1) the VNTR variation of the second intron, 2) the indel promoter polymorphism (5HTTLPR or SERT), and 3) a single nucleotide polymorphism (SNP) rs25531. Additionally, SLC6A4 was resequenced to identify new SNPs for exploratory analyses. DNA from 1914 subjects in the STAR*D study were genotyped for the intron 2 VNTR region, the indel promoter polymorphism, and rs25531. Associations of these variants with remission of depressive symptoms were evaluated following citalopram treatment. In white non-Hispanic subjects, variations in the intron 2 VNTR (point-wise P = 0.041) and the indel promoter polymorphism (point-wise P = 0.039) were associated with remission following treatment with citalopram. The haplotype composed of the three candidate loci was also associated with remission, with a global p-value of 0.040 and a maximum statistic simulation p-value of 0.0031 for the S-a-12 haplotype, under a dominant model. One SNP identified through re-sequencing the SLC6A4 gene, Intron7-83-TC, showed point-wise evidence of association, which did not remain significant after correction for the number of SNPs evaluated in this exploratory analysis. No associations between these SLC6A4 variations and remission were found in the white Hispanic or black subjects. These findings suggest that multiple variations in the SLC6A4 gene are associated with remission in white non-Hispanic depressed adults treated with citalopram. The mechanism of action of these variants remains to be determined.

Novel pattern of P53 mutation in breast cancers from Austrian women.

Since mutagens produce an extraordinary diversity of mutational patterns, differential mutational exposures among populations are expected to produce different patterns of mutation. Classical epidemiological methods have been successful in implicating specific mutagens in cancers such as those of lung and skin in which one mutagen predominates. In breast cancer, however, no mutagens have been implicated in an unequivocal manner. In an attempt to facilitate epidemiological studies, we have been studying the pattern of p53 gene mutations in breast cancers from multiple populations with high and low breast cancer incidences. We previously reported that breast cancers from Midwest United States, predominantly rural Caucasian women, have a different pattern of p53 gene mutation from populations of Western European women. Herein, we analyze patterns of p53 mutations from Graz, Austria, another population with a high incidence of breast cancer. Among the 60 Austrian breast cancers analyzed, 14 (23%) have a p53 gene mutation in exons 5-9 or in adjacent splice junctions. Analysis of the patterns of mutation shows differences between the "Western European" profile and the Austrian and Midwest United States groups (P = 0.027 and 0.024, respectively). The Austrian pattern is characterized by a high frequency of A:T-->T:A transversions (P = 0.006). The presence of distinct patterns of mutation among the limited number of analyzed populations of Western European origin supports the idea that differential mutagenic exposure and/or genetic differences contribute to breast cancer mutagenesis among geographically distinct Caucasians of Western European origin.

Loss of heterozygosity suggests multiple genetic alterations in pheochromocytomas and medullary thyroid carcinomas.

Loss of heterozygosity (LOH) at specific loci may help localize tumor suppressor genes involved in the formation of various familial and sporadic tumors. In addition, the genetic loci for a number of familial tumor syndromes have been mapped by linkage analysis. To explore the possible role of tumor suppressor genes in endocrine tumors, we tested 41 pheochromocytomas (34 sporadic and 7 familial) and 11 medullary thyroid cancers (MTC) (10 sporadic and 1 familial) for LOH near a variety of potentially important genetic loci: (a) the multiple endocrine neoplasia type 2A (MEN 2A) locus on chromosome 10; (b) the von Hippel-Lindau locus on 3p; and (c) the p53 and neurofibromatosis 1 loci on 17. We also examined chromosomes 1p and 22q because previous studies in a small number of pheochromocytomas and MTCs suggested LOH in these regions. Background rates for LOH were assessed using several "random" probes. Finally, we examined a number of clinical and histologic characteristics of these tumors for possible correlations with specific genetic alterations. LOH in the region of the MEN 2A locus was uncommon (0% for MTCs, 5% for pheochromocytomas). However, we found significant allelic losses in pheochromocytomas on chromosomes 1p (42%), 3p (16%), 17p (24%), and 22q (31%). We also noted a correlation between LOH on 1p and urinary excretion of metanephrine by these patients (P = 0.02). LOH on 1p, 3p, and 17p also appeared to be associated with increased tumor volume. Analysis of the smaller number of MTCs demonstrated allelic losses on chromosomes 1p and 22q. Our results suggest that tumor formation and/or progression in pheochromocytomas and MTCs involves multiple genes, analogous with the model proposed for colon carcinoma.

Levamisole potentiation of fluorouracil antiproliferative activity mimicked by orthovanadate, an inhibitor of tyrosine phosphatase.

BACKGROUND: Levamisole is an effective antihelminthic drug with immunomodulatory and anticancer activities in model systems. Combined with fluorouracil (5-FU) as adjuvant treatment following resection of Dukes' stage C colon carcinomas, levamisole significantly reduces mortality. However, neither 5-FU nor levamisole alone has a significant effect on survival in this patient group. Previously, we noted that in vitro levamisole potentiated the antiproliferative activity of 5-FU. PURPOSE: Because levamisole is known to inhibit alkaline phosphatases and has been reported to inhibit dephosphorylation of some membrane phosphoproteins, we studied the effects of levamisole analogues and of chemically unrelated inhibitors of phosphatases for their ability to potentiate 5-FU inhibition of tumor cell line proliferation in vitro. METHODS: Human cancer cell lines were exposed to drugs alone or in combination with 5-FU. Antiproliferative activity was measured by determining the extent of reduction of colony formation by the cell lines in test plates compared with control plates. RESULTS: We found that potentiation of 5-FU cytotoxicity by levamisole and by p-hydroxytetramisole, a metabolite of levamisole, is mimicked by orthovanadate, an inhibitor of tyrosine phosphatases, but not by okadaic acid, an inhibitor of serine and threonine phosphatases, Furthermore, l-p-bromotetramisole, a synthetic analogue of levamisole that is 10-fold more potent in inhibition of alkaline phosphatase than levamisole, potentiates the antiproliferative activity of 5-FU to a greater extent than d-p-bromotetramisole, a stereoisomer of l-p-bromotetramisole with little antiphosphatase activity. CONCLUSION: Inhibition of tyrosine phosphatases may be responsible for the potentiation by levamisole of the inhibitory activity of 5-FU in vitro. IMPLICATIONS: Inhibition of dephosphorylation of regulatory phosphoproteins may be related to the therapeutic efficacy of the combination of levamisole and 5-FU in the adjuvant treatment of colon carcinoma and may underlie at least some of the multiple effects of levamisole on immune parameters.

Phase II study of ifosfamide-etoposide-mesna in adults with advanced nonosseous sarcomas.

Between April 1987 and July 1988, 44 adults with histologically proven, objectively assessable advanced nonosseous sarcomas were treated with 2.5 g of ifosfamide/m2, 100 mg of etoposide/m2, and 2.5 g of mesna/m2 (500 mg/m2 X 5) daily for 3 consecutive days every 4 weeks. This regimen was generally well tolerated as outpatient treatment. Because of the potential CNS effects of ifosfamide, we recommended that elderly patients, persons receiving high doses of opiates, and patients susceptible to the syndrome of vertigo, perspiration, and hypotension (without tachycardia) be hospitalized for treatment. At initial treatment, leukocyte count nadirs were less than 1,000/microL and platelet count nadirs were less than 100,000/microL in 38% and 15%, respectively, of the 39 patients for whom such data were available. Objective tumor regression occurred in approximately 16% (95% confidence interval, 7%-30%) of the 44 patients (six, partial responses; one, complete response). For the 44 patients, median time to disease progression was 2.3 months; median time to death was 9.4 months. While this regimen was effective in three of 20 patients who had been previously treated with a doxorubicin-based regimen, only one of the 12 patients whose tumors had been primarily refractory to the doxorubicin-based regimen experienced objective tumor regression on our ifosfamide-based regimen.

Controlled trial of megestrol acetate for the treatment of cancer anorexia and cachexia.

Preliminary information has suggested that megestrol acetate leads to appetite stimulation and nonfluid weight gain in patients with breast cancer, other cancers, and AIDS. Pursuant to this, we developed a randomized, double-blind, placebo-controlled trial of megestrol acetate in patients with cancer-associated anorexia and cachexia. We randomly assigned 133 eligible patients to receive 800 mg of megestrol acetate per day or a placebo. Patients assigned to megestrol acetate more frequently reported improved appetite (P = .003) and food intake (P = .009) when compared with patients receiving the placebo. A weight gain of 15 lb or more over baseline was seen in 11 of 67 (16%) patients receiving megestrol acetate compared with one of 66 (2%) given the placebo (P = .003). Patients receiving megestrol acetate reported significantly less nausea (13% vs. 38%; P = .001) and emesis (8% vs. 25%, P = .009). No clinically or statistically significant toxic reactions were ascribed to megestrol acetate, with the exception of mild edema. This study convincingly demonstrated that megestrol acetate can stimulate appetite and food intake in patients with anorexia and cachexia associated with cancer, leading to significant weight gain in a proportion of such patients.

Efficacy of bilateral prophylactic mastectomy in BRCA1 and BRCA2 gene mutation carriers.

BACKGROUND: In women with a family history of breast cancer, bilateral prophylactic mastectomy is associated with a decreased risk of subsequent breast cancer of approximately 90%. We examined the association between bilateral prophylactic mastectomy and breast cancer risk in women at high risk for breast cancer who also had mutations in BRCA1 and BRCA2 genes. METHODS: We obtained blood samples from 176 of the 214 high-risk women who participated in our previous retrospective cohort study of bilateral prophylactic mastectomy. We used conformation-sensitive gel electrophoresis and direct sequence analysis of the blood specimens to identify women with mutations in BRCA1 and BRCA2. The carriers' probabilities of developing breast cancer were estimated from two different penetrance models. RESULTS: We identified 26 women with an alteration in BRCA1 or BRCA2. Eighteen of the mutations were considered to be deleterious and eight to be of uncertain clinical significance. None of the 26 women has developed breast cancer after a median of 13.4 years of follow-up (range, 5.8-28.5 years). Three of the 214 women are known to have developed a breast cancer after prophylactic mastectomy. For two of these women, BRCA1 and BRCA2 screening was negative, and no blood specimen was available for the third. Estimations of the effectiveness of prophylactic mastectomy were performed, considering this woman as both a mutation carrier and a noncarrier. These calculations predicted that six to nine breast cancers should have developed among the mutation carriers, which translates into a risk reduction, after bilateral prophylactic mastectomy, of 89.5%-100% (95% confidence interval = 41.4% to 100%). CONCLUSIONS: Prophylactic mastectomy is associated with a substantial reduction in the incidence of subsequent breast cancer not only in women identified as being at high risk on the basis of a family history of breast cancer but also in known BRCA1 or BRCA2 mutation carriers.

Microsatellite instability and 8p allelic imbalance in stage B2 and C colorectal cancers.

BACKGROUND: Microsatellite instability (MSI) and allelic imbalance involving chromosome arms 5q, 8p, 17p, and 18q are genetic alterations commonly found in colorectal cancer. We investigated whether the presence or absence of these genetic alterations would allow stratification of patients with Astler-Coller stage B2 or C colorectal cancer into favorable and unfavorable prognostic groups. METHODS: Tumors from 508 patients were evaluated for MSI and allelic imbalance by use of 11 microsatellite markers located on chromosome arms 5q, 8p, 15q, 17p, and 18q. Genetic alterations involving each of these markers were examined for associations with survival and disease recurrence. All P values are two-sided. RESULTS: In univariate analyses, high MSI (MSI-H), i.e., MSI at 30% or more of the loci examined, was associated with improved survival (P =.02) and time to recurrence (P =.01). The group of patients whose tumors exhibited allelic imbalance at chromosome 8p had decreased survival (P =.02) and time to recurrence (P =.004). No statistically significant associations with survival or time to recurrence were observed for markers on chromosome arms 5q, 15q, 17p, or 18q. In multivariate analyses, MSI-H was an independent predictor of improved survival (hazard ratio [HR] = 0.51; 95% confidence interval [CI] = 0.31-0.82; P =.006) and time to recurrence (HR = 0.42; 95% CI = 0.24-0.74; P =.003), and 8p allelic imbalance was an independent predictor of decreased survival (HR = 1.89; 95% CI = 1.25-2.83; P =. 002) and time to recurrence (HR = 2.07; 95% CI = 1.32-3.25; P =.002). CONCLUSIONS: Patients whose tumors exhibited MSI-H had a favorable prognosis, whereas those with 8p allelic imbalance had a poor prognosis; both alterations served as independent prognostic factors. To our knowledge, this is the first report of an association between 8p allelic imbalance and survival in patients with colorectal cancer.

Tumor necrosis factor-alpha allelic frequency and chromosome 6 allelic imbalance in patients with colorectal cancer.

The human tumor necrosis factor (TNF) locus is located on chromosome 6p21.3 and contains at least five polymorphic microsatellites. In this study, we compared the allelic frequencies derived from 50 normal controls to 64 patients with colorectal cancer at one of these loci, TNF alpha. No differences in allelic frequencies were observed between these two groups (P = 0.47). However, sequencing of the TNF alpha PCR product revealed two populations of TNF alpha alleles; alleles with the expected DNA sequence (i.e., the expected number of AC/GT repeats) and alleles that contained 8-bp deletions adjacent to the microsatellite repeat. In addition, we also examined paired normal and tumor DNA from the colorectal cancer group for microsatellite alterations at the TNF alpha locus, including allelic loss of heterozygosity and microsatellite instability. Of the 64 tumors examined, 13 (20%) demonstrated microsatellite instability, and 14 (42%) of 33 informative cases demonstrated allelic imbalance. Analysis of 10 additional chromosome 6 loci for allelic loss showed that 23 (47%) of 49 informative cases exhibited allelic imbalance with at least one chromosome 6p marker, 23 (47%) of 49 with at least one 6q marker, and 29 (59%) of 49 with at least one marker on chromosome 6. Examination of tumors for the minimal region of deletion overlap suggests the presence of tumor suppressor genes on both 6p and 6q.

Microsatellite instability in Muir-Torre syndrome.

Muir-Torre syndrome (MTS) is characterized by the presence of at least one sebaceous tumor and at least one visceral malignancy. Although a wide range of internal malignancies have been reported, the most frequently observed internal neoplasm is colorectal carcinoma. MTS and hereditary nonpolyposis colorectal carcinoma (HNPCC) share many clinical and pathological characteristics and thus may share similar genetic mechanisms of tumorigenesis. Recently, microsatellite instability (MIN) has been reported in tumor tissue from patients with HNPCC. In order to determine if tumors from MTS patients might also show MIN, we examined DNA extracted from paraffin-embedded tissues for the presence of MIN at (CA)n repeats on chromosomes 5q, 15q, 17p, and 18q. Data was obtained on 13 patients, 9 of which had at least one colorectal tumor. Of these, six demonstrated widespread MIN in all sebaceous and colorectal tumors examined, as well as in a transitional cell carcinoma of the renal pelvis, a prostatic adenocarcinoma and a keratoacanthoma. Overall, patients with MIN differed from patients without MIN in several respects, the most important of which include: (a) uniform presence and early onset of colorectal cancer (average age, 40 versus 70 years); (b) prolonged survival following diagnosis of visceral malignancy (median survival, 32 versus 11 years); and (c) a greater number of visceral and skin tumors. These data suggests that patients with MTS may be composed of at least two subgroups, each demonstrating different genetic, pathological and clinical features. Furthermore, the subgroup demonstrating MIN may share similar genetic mechanisms of tumorigenesis with patients having HNPCC, supporting the notion that these syndromes are allelic.

BRCA1 and BRCA2 have a limited role in familial prostate cancer.

Epidemiological studies have suggested that the breast cancer susceptibility genes, BRCA1 and BRCA2, may be involved in the development of prostate cancer. Several studies have screened prostate cancer populations for the presence of BRCA1 and BRCA2 mutations, with few mutations identified. In this study, 22 high-risk prostate cancer families (at least three cases of prostate cancer) were screened by conformation-sensitive gel electrophoresis (CSGE) for mutations in BRCA1 and BRCA2. To maximize the chance of finding mutations in these two genes, families were also selected for the presence of at least two cases of breast and/or ovarian cancer. We identified one previously reported BRCA2 missense mutation and two previously unreported BRCA2 intron polymorphisms. No BRCA1 or BRCA2 truncating mutations were detected. Thus, BRCA1 and BRCA2 appear to have a limited role in familial prostate cancer, and families with both prostate and breast cancer may result from mutations in other predisposition genes.

Expression of p53 and 17p allelic loss in colorectal carcinoma.

Mutations in the p53 gene are the most common genetic changes in cancer thus far. Many p53 mutations result in a protein product having a prolonged half-life compared to wild-type p53. The mutant protein is frequently detectable immunohistochemically, whereas the wild-type p53 present in normal cells is not. We examined 90 colorectal carcinomas for increased expression of p53 using 3 p53 specific monoclonal antibodies, PAb1801, PAb421, and PAb240. Overall, 70% of the colorectal carcinomas stained for p53. Each tumor's DNA was also assessed for loss of heterozygosity on chromosome 17p, the location of the p53 gene. Of those tumors that reacted with the anti-p53 antibodies, 76% showed loss on chromosome 17p. Tumors with loss of heterozygosity on 17p generally stained with all 3 antibodies, whereas those without loss tended to stain with just one antibody, typically PAb240. Fifteen tumors were examined for the presence of specific p53 mutations. A total of 10 mutations were found, 6 were missense and 2 were deletions, and all but one of the tumors with missense mutations stained for p53.

Allelic imbalance and microsatellite instability in prostatic adenocarcinoma.

Although prostate cancer is one of the most common malignancies of males in Western countries, relatively little is known about the molecular mechanisms involved in tumor initiation and progression. Allelic loss studies have suggested the involvement of multiple tumor suppressor genes (TSGs), but few detailed studies of all chromosomes have been performed. In an effort to localize and identify candidate TSGs, we performed allelic imbalance (AI) studies on 55 prostate cancers, using 135 polymorphic microsatellite markers. For the entire chromosome. AI ranged from a low of 0% on chromosomes 14 and 20 to a high of 71% on chromosome 8. Chromosomal regions demonstrating at least twice the background frequency of AI (ranging from 20 to 69%) included 5q, 6q, 7q, 8p, 13, l6q, l8q, and 21. In addition, AI was examined for association with a number of clinicopathological parameters. AI on chromosomes 7 and 16 were each associated with greater age at diagnosis (P = 0.009 and 0.001, respectively), and AI on chromosomes 10, 16, and 18 was associated with aneuploidy/tetraploidy (P = 0.037, 0.013, and 0.054, respectively). Furthermore, AI on chromosome 5 was associated with a higher pathological stage (P = 0.021) and on chromosome 8 and 16 with a higher Gleason score (P = 0.027 and 0.041, respectively). No tumor exhibited a phenotype of widespread microsatellite instability. These results indicate that there likely exist multiple sites harboring candidate TSG in prostate cancer, some of which may have important clinical implications, and which argue against widespread microsatellite instability.

Reduced COX-2 protein in colorectal cancer with defective mismatch repair.

Most colorectal adenomas and carcinomas arise in the setting of chromosomal instability characterized by progressive loss of heterozygosity. In contrast, approximately 15-20% of colorectal neoplasms arise through a distinct genetic pathway characterized by microsatellite instability (MSI) associated with frequent loss of expression of one of the DNA mismatch repair enzymes, most often hMLH1 or hMSH2. These distinct genetic pathways are reflected by differences in tumor histopathology, distribution in the colon, prognosis, and dwell time required for progression from adenoma to carcinoma. To determine whether these two groups of tumors differ in their expression of cyclooxygenase-2 (COX-2), a putative chemopreventative target, immunostaining for this protein was performed in colorectal cancers categorized by the presence (n = 41) and absence (n = 66) of defective mismatch repair. Defective mismatch repair was defined by the presence of tumor microsatellite instability (MSI-H, > or =40% of markers demonstrating instability) and by the absence of protein expression for either hMLH1 or hMSH2. Overall, our results showed that low or absent COX-2 staining was significantly more common among tumors with defective mismatch repair (P = 0.001). Other features predictive of low COX-2 staining included marked tumor infiltrating lymphocytosis, and solid/cribiform or signet ring histological patterns. These observations indicate that colorectal cancers with molecular and phenotypic characteristics of defective DNA mismatch repair express lower levels of COX-2. The clinical implications of this biological distinction remain unknown but should be considered when assessing the efficacy of COX-2 inhibitors for chemoprevention in patients whose tumors may arise in the setting of defective DNA mismatch repair.

Microsatellite instability in colorectal cancer: different mutator phenotypes and the principal involvement of hMLH1.

Recent studies have demonstrated the presence of microsatellite instability (MSI) in tumors from patients with hereditary nonpolyposis colorectal cancer and in a large number of sporadic tumors. To further characterize the type of alterations at these loci and their frequency of involvement in colon cancer, we studied DNA extracted from paraffin-embedded tissue from 508 patients using 11 microsatellites localized to chromosomes 5, 8, 15, 17, and 18. Overall, MSI at each locus varied in character and frequency and was observed with at least one marker in 191 cases (37.6%). Based on the number of markers displaying instability per tumor, three groups of patients were defined: those with <30% of the markers showing instability (MSI-L,, n = 109, 21.5%); those with > or = 30% (MSI-H, n = 82, 16.1%); and those showing no instability (MSS, n = 317, 62.4%). These groups were tested for correlations with a number of clinical and pathological parameters, including age, sex, stage, ploidy status, and site of tumor. Comparing across the three groups and verified by pair-wise comparisons, the MSI-H group was associated with tumor site (proximal colon, P = 0.001), sex (females, P = 0.005), stage (Dukes' B, P = 0.01), and ploidy status (diploid, P = 0.03). No significant differences were noted between the MSI-L and MSS group for any of the parameters tested. An additional 188 consecutive surgical colorectal cancer cases were examined for the presence of MSI and for the immunohistochemical expression of hMLH1 and hMSH2 proteins. Of this group, 129 (68.6%) were classified as MSS, 17 (9.0%) as MSI-L, and 42 (22.3%) as MSI-H. None of the MSS and none of the MSI-L tumors had altered expression of either hMLH1 or hMSH2. However, the majority of MSI-H (40 of 42, 95%) cases demonstrated absence of staining for these proteins. The most frequently altered protein was hMLH1, occurring in 95% of the tumors with altered expression. Cumulatively, these data suggest that the tumor phenotype MSI-H is distinct from tumor phenotypes MSI-L and MSS, with no apparent differences between MSI-L and MSS. Furthermore, altered hMLH1 protein expression appears to be responsible for the mutator phenotype in the vast majority of MSI-H tumors.

Role of HPC2/ELAC2 in hereditary prostate cancer.

The HPC2/ELAC2 gene on chromosome 17p was recently identified as a candidate gene for hereditary prostate cancer (HPC). To confirm these findings, we screened 300 prostate cancer patients (2 affected members/family) from 150 families with HPC for potential germ-line mutations using conformation-sensitive gel electrophoresis, followed by direct sequence analysis. The minimum criteria for our families with HPC was the presence of 3 affected men with prostate cancer. A total of 23 variants were identified, including 13 intronic and 10 exonic changes. Of the 10 exonic changes, 1 truncating mutation was identified, a Glu216Stop nonsense mutation. This nonsense variant was found in 2 of 3 affected men in a single family. The remaining nine alterations included five missense, three silent, and one variant in the 3' untranslated region. To additionally test for potential associations of polymorphic variants and increased risk for disease, we genotyped two common polymorphisms, Ser217Leu and Ala541Thr, in 446 prostate cancer patients from 164 families with HPC and 502 population-based controls. The frequency of the Leu217 variant was similar for patients (32.3%) and controls (31.8%), as was the frequency of the Thr541 variant (5.4% among patients versus 5.2% among controls). In contrast to previous reports, we found no association of the joint effects of Leu271 and Thr541 (odds ratio, 1.04; 95% confidence interval, 0.57-1.89). Overall, our results did not reveal any association between these two common polymorphisms and the risk for HPC. The finding of a nonsense mutation in the HPC2/ELAC2 gene confirms its potential role in genetic susceptibility to prostate cancer. However, our data also suggest that germ-line mutations of the HPC2/ELAC2 are rare in HPC and that the variants Leu217 and Thr541 do not appear to influence the risk for HPC. Cumulatively, these results suggest that alterations within the HPC2/ELAC2 gene play a limited role in genetic susceptibility to HPC.