Jeffrey Searle

Characterisation of a subtype of colorectal cancer combining features of the suppressor and mild mutator pathways

BACKGROUND: 10% of sporadic colorectal cancers are characterised by a low level of microsatellite instability (MSI-L). These are not thought to differ substantially from microsatelite-stable (MSS) cancers, but MSI-L and MSS cancers are distinguished clinicopathologically and in their spectrum of genetic alterations from cancers showing high level microsatellite instability (MSI-H). AIMS: To study the distribution of molecular alterations in a series of colorectal cancers stratified by DNA microsatellite instability. METHODS: A subset of an unselected series of colorectal cancers was grouped by the finding of DNA MSI at 0 loci (MSS) (n = 51), 1-2 loci (MSI-L) (n = 38) and 3-6 loci (MSI-H) (n = 25). The frequency of K-ras mutation, loss of heterozygosity (LOH) at 5q, 17p and 18q, and patterns of p53 and beta catenin immunohistochemistry was determined in the three groups. RESULTS: MSI-H cancers had a low frequency of K-ras mutation (7%), LOH on chromosomes 5q (0%), 17p (0%) and 18q (12.5%), and a normal pattern of immunostaining for p53 and beta catenin. MSI-L cancers differed from MSS cancers in terms of a higher frequency of K-ras mutation (54% v 27%) (p = 0.01) and lower frequency of 5q LOH (23% v 48%) (p = 0.047). Whereas aberrant beta catenin expression and 5q LOH were concordant (both present or both absent) in 57% of MSS cancers, concordance was observed in only 20% of MSI-L cancers (p = 0.01). CONCLUSIONS: MSI-L colorectal cancers are distinct from both MSI-H and MSS cancers. This subset combines features of the suppressor and mutator pathways, may be more dependent on K-ras than on the APC gene in the early stages of neoplastic evolution, and a proportion may be related histogenetically to the serrated (hyperplastic) polyp.

Hyperplastic Polyposis: Association With Colorectal Cancer

Hyperplastic polyposis is a loosely defined syndrome initially thought not to confer a clinically important predisposition to colorectal cancer. The aim of the current study was to examine the clinical, histologic, and molecular features of a prospective series of cases meeting a strict definition of the condition. Twelve patients were identified, seven of whom had developed colorectal cancer. Most polyps were hyperplastic, but 11 patients also had polyps containing dysplasia as either serrated adenomas, mixed polyps, or traditional adenomas. The mean percentage of dysplastic polyps in patients with cancer was 35%, and in patients without cancer, 11% (p < 0.05). Microsatellite instability (MSI) was present in 3 of 47 hyperplastic polyps and two of eight serrated adenomas. Kras was mutated in 8 of 47 hyperplastic polyps and two of eight serrated adenomas. No polyps showed loss of heterozygosity of chromosomes 5q, 1p, or 18q. Two of seven cancers showed a high level of MSI. It is concluded that hyperplastic polyposis is associated with a high risk of colorectal cancer. Hyperplastic polyps are the dominant type of polyp, but most cases have some dysplastic epithelium. A higher proportion of dysplastic polyps is associated with increased cancer risk. Clonal genetic changes are observed in some hyperplastic polyps and serrated adenomas.

Successive waves of apoptosis in the rat prostate after repeated withdrawal of testosterone stimulation

&NA; In rats with castration‐induced ventral prostatic atrophy, testosterone treatment resulted in reconstitution of the normal weight and histological structure of the gland within 10 d. Subsequent withdrawal of the hormone was followed by rapid involution, which was effected by a combination of extensive loss of epithelial cells by apoptosis and decrease in the size of the cells that remained. The wave of apoptotic deletion was similar to that accompanying the initial involution after castration, and in both cases the rate of apoptosis fell to very low levels by 20 d. Two further consecutive episodes of involution produced by sequential administration and withdrawal of testosterone were also accompanied by similar waves of apoptosis. The results provide quantitative evidence supporting suggestions that apoptosis may be of major kinetic significance in the involution of endocrine‐dependent glandular tissues. The majority of the epithelial cells remaining after the completion of involution were able to survive continuing androgen deprivation, but with renewed testosterone stimulation they repeatedly generated populations that once again responded to withdrawal with massive cellular death. The factors determining the selective susceptibility of individual cells in these populations clearly merit investigation.

The significance of cell death by apoptosis in hepatobiliary disease

Keywords: acidophilic body; apoptosis; cell death; Councilman body; hepatitis; piecemeal necrosis.

A novel mutation in ferroportin1 is associated with haemochromatosis in a Solomon Islands patient

Background: A severe form of iron overload with the clinicopathological features of haemochromatosis inherited in an autosomal dominant manner has been described in the Solomon Islands. The genetic basis of the disorder has not been identified. The disorder has similarities to type 4 haemochromatosis, which is caused by mutations in ferroportin1. Aims: The aims of this study were to identify the genetic basis of iron overload in a patient from the Solomon Islands. Patient and methods: Genomic DNA was isolated from peripheral blood leucocytes of a Solomon Islands man with severe iron overload. The entire coding region and splice sites of the ferroportin1 gene was sequenced. Results and conclusions: A novel missense mutation (431A>C; N144T) was identified in exon 5 of the ferroportin1 gene. A novel restriction endonuclease based assay which identifies both the N144T and N144H mutations was developed which will simplify the diagnosis and screening of patients for iron overload in the Solomon Islands and other populations. This is the first identified mutation associated with haemochromatosis in the Solomon Islands population.

Steatohepatitis Associated With Limb Lipodystrophy

Two patients who presented with steatohepatitis had acquired partial lipodystrophy. This association has not previously been well documented. A common pathophysiological mechanism in lipodystrophy, obesity-associated nonalcoholic steatohepatitis, and alcoholic liver disease is possible.

Expression of Bcl-2 protein is decreased in colorectal adenocarcinomas with microsatellite instability

Bcl-2 is known to inhibit apoptosis and is thought to play a role in colorectal tumour development. Studies of the promoter region of bcl-2 have indicated the presence of a p53 responsive element which downregulates bcl-2 expression. Since p53 is commonly mutated in colorectal cancers, but rarely in those tumours showing microsatellite instability (MSI), the aim of this study was to examine the relationship of bcl-2 protein expression to MSI, as well as to other clinicopathological and molecular variables, in colorectal adenocarcinomas. Expression of bcl-2 was analysed by immunohistochemistry in 71 colorectal cancers which had been previously assigned to three classes depending upon their levels of MSI. MSI-high tumours demonstrated instability in three or more of six microsatellite markers tested, MSI-low tumours in one or two of six, and MSI-null in none of six. Bcl-2 expression in tumours was quantified independently by two pathologists and assigned to one of five categories, with respect to the number of cells which showed positive staining: 0, up to 5%; 1, 6 – 25%; 2, 26 – 50%; 3, 51 – 75%; and 4, ⩾76%. Bcl-2 negative tumours were defined as those with a score of 0. Bcl-2 protein expression was tested for association with clinicopathological stage, differentiation level, tumour site, age, sex, survival, evidence of p53 inactivation and MSI level. A significant association was found between bcl-2 expression and patient survival (P=0.012, Gehan Wilcoxon test). Further, a significant reciprocal relationship was found between bcl-2 expression and the presence of MSI (P=0.012, Wilcoxon rank sum test). We conclude that bcl-2 expressing colorectal cancers are more likely to be MSI-null, and to be associated with improved patient survival.

The Spontaneous Occurrence Of Apoptosis In Squamous Carcinomas Of The Uterine Cervix

Summary A distinctive type of individual ceil necrosis occurring in squamous carcinomas of the uterine cervix has been studied by light and electron microscopy. The first stage of the process involves condensation and fragmentation of scattered tumour cells with the production of compact, membrane‐bounded bodies in which organelles appear well preserved. These are then phagocytosed by either neoplastic epithelial cells or histiocytes, and are degraded by lysosomal hydrolases. The phenomenon is identical with shrinkage necrosis or apoptosis, which has been described in non‐neoplastic tissues under both physiological and pathological conditions, and in several other neoplasms. The findings indicate that cell loss by this means is often considerable in cervical carcinomas, and are consistent with the hypothesis that the spontaneous occurrence of apoptosis might largely account for the discrepancy known to exist between the rate of cell multiplication in malignant tumours and their rate of growth.

Analysis of loss of heterozygosity and KRAS2 mutations in ovarian neoplasms: Clinicopathological correlations

The molecular events that give rise to ovarian epithelial neoplasms are not well understood. In particular, it is not known whether adenocarcinomas arise from benign or low malignant potential (LMP) precursors. We have examined a large series of benign (25) and LMP (31) ovarian tumors for loss of heterozygosity (LOH) at multiple loci on 17 chromosomes. LOH was observed in benign tumors on chromosomes 6 (14%) and 9 (5%) and on the X chromosome (33%) only. LOH on these chromosomes was also detected in a small number of LMP neoplasms, suggesting that these may derive sometimes from benign precursors. In addition, we examined LOH in 93 adenocarcinomas. Analysis of associations between LOH events showed that LOH on chromosomes 5 and 17 (P = 0.0002) and on chromosomes 17 and 18 (P = 0.00007) were associated significantly with each other, which suggests that these may represent cooperative, progressive events. No novel significant associations were identified between LOH events and stage, grade, or histology, which would indicate the existence of genetic heterogeneity in ovarian neoplasms. KRAS2 mutations were detected more often in LMP neoplasms than in malignant tumors (P = 0.004) and were detected more often in Stage I/II malignant tumors than in Stage III/IV malignant tumors (P = 0.033), suggesting that LMP tumors with KRAS2 mutations are unlikely to progress to frank malignancy. Univariate (but not multivariate) survival analysis showed that LOH of chromosomes 11 (P = 0.039) and 17 (P = 0.04) was associated with a significantly worse prognosis. Replication of these novel findings is necessary, and the identification, isolation, and characterization of the critical genes affected by LOH will determine their importance in the pathogenesis of ovarian malignancies. Genes Chromosom. Cancer 18:75–83, 1997.

Exclusion of APC and MCC as the gene defect in one family with familial juvenile polyposis

BACKGROUND In familial juvenile polyposis, multiple juvenile polyps occur throughout the colon. The genetic defect has not been characterized. The risk of colon cancer is increased, although the magnitude of the increased risk is controversial. The hypothesis of this study was that the genetic defect is within a tumor suppressor gene, possibly one already known to be inactivated in colorectal neoplasia. METHODS Linkage analysis using the short tandem repeat polymorphism D5S346 was performed to determine if juvenile polyposis was linked to either APC (adenomatous polyposis coli) or MCC (mutated in colorectal carcinoma) genes within a single large family. RESULTS A family in which eight subjects have been affected by juvenile polyposis over three generations is described. Six affected subjects had colectomies in childhood, but the two who have so far survived beyond 35 years of age have developed adenocarcinoma of the jejunum. Within this family, linkage analysis excluded linkage of the juvenile polyposis trait to either APC or MCC. CONCLUSIONS In a family with juvenile polyposis with a clear predisposition to malignancy, including carcinoma of the jejunum, APC and MCC were not the defective genes causing the condition.