Joanne Young

Morphology of sporadic colorectal cancer with DNA replication errors

Background—Up to 15% of colorectal cancers are characterised by DNA microsatellite instability (MIN), shown by the presence of DNA replication errors (RERs). Aims—To identify pathological features that are discriminating for colorectal cancer (CRC) showing extensive MIN. Subjects—A prospective series of 303 patients with CRC and no family history of either familial adenomatous polyposis or hereditary non-polyposis colorectal cancer. Methods—DNA was extracted from fresh tissue samples and the presence of MIN was studied at nine loci that included TGFβRII, IGFIIR, and BAX. The 61 cases showing RERs were compared with 63 RER negative cases with respect to a comprehensive set of clinical and pathological variables. Predictive utility of the variables was tested by decision tree analysis. Results—Twenty seven patients with CRC showed extensive RERs (three loci or more) (RER+) and 34 had limited RERs only (28 = one locus; 6 = two loci) (RER+/−), yielding a bimodal distribution. RER+ cancers differed from RER− and RER+/− cases. Tumour type (adenocarcinoma, mucinous carcinoma, and undifferentiated carcinoma) (p=0.001), tumour infiltrating lymphocytes (p=0.001), and anatomical site (p=0.001) were the most significant of the discriminating variables. Algorithms developed by decision tree analysis allowed cases to be assigned to RER+ versus RER− and +/− status with a global sensitivity of 81.5%, specificity of 96%, and overall accuracy of 93%. Conclusion—Pathological examination of CRC allows assignment of RER+ status; assignment is specific and relatively sensitive. Conversely RER− and RER+/− CRC are indistinguishable.

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.

Analysis of genetic and phenotypic heterogeneity in juvenile polyposis

BACKGROUND Juvenile polyposis syndrome (JPS) is characterised by gastrointestinal (GI) hamartomatous polyposis and an increased risk of GI malignancy. Juvenile polyps also occur in the Cowden (CS), Bannayan-Ruvalcaba-Riley (BRRS) and Gorlin (GS) syndromes. Diagnosing JPS can be problematic because it relies on exclusion of CS, BRRS, and GS. Germline mutations in the PTCH, PTENand DPC4 (SMAD4)genes can cause GS, CS/BRRS, and JPS, respectively. AIMS To examine the contribution of mutations in PTCH,PTEN, and DPC4(SMAD4) to JPS. METHODS Forty seven individuals from 15 families and nine apparently sporadic cases with JPS were screened for germline mutations inDPC4, PTEN, andPTCH. RESULTS No patient had a mutation in PTEN orPTCH. Five different germline mutations were detected in DPC4; three of these were deletions, one a single base substitution creating a stop codon, and one a missense change. None of these patients had distinguishing clinical features. CONCLUSIONS Mutations in PTEN and PTCHare unlikely to cause juvenile polyposis in the absence of clinical features indicative of CS, BRRS, or GS. A proportion of JPS patients harbour DPC4 mutations (21% in this study) but there remains uncharacterised genetic heterogeneity in JPS.

A transforming growth factor beta 1 receptor type II mutation in ulcerative colitis-associated neoplasms

BACKGROUND & AIMSnNumerous gastrointestinal tumors, notably sporadic and ulcerative colitis (UC)-associated colorectal carcinomas and dysplasias, gastric cancers, and esophageal carcinomas, manifest microsatellite instability. Recently, a transforming growth factor beta 1 type II receptor (TGF-beta 1RII) mutation in a coding microsatellite was described in colorectal carcinomas showing instability. One hundred thirty-eight human neoplasms (61 UC-associated, 35 gastric, 26 esophageal, and 16 sporadic colorectal) were evaluated for this TGF-beta 1RII mutation.nnnMETHODSnWhether instability was present at other chromosomal loci in these lesions was determined. In lesions manifesting or lacking instability, the TGF-beta 1RII coding region polydeoxyadenine (poly A) microsatellite tract was polymerase chain reaction amplified with 32P-labeled deoxycytidine triphosphate. Polymerase chain reaction products were electrophoresed on denaturing gels and exposed to radiographic film.nnnRESULTSnThree of 18 UC specimens with instability at other chromosomal loci (17%) showed TGF-beta 1RII poly A tract mutation, including 2 cancers and 1 dysplasia; moreover, 2% of UC specimens without instability (1 of 43) (1 cancer), 81% of unstable sporadic colorectal cancers (13 of 16), and none of the 61 stable or unstable gastric or esophageal cancers contained TGF-beta 1RII mutations.nnnCONCLUSIONSnMutational inactivation of the poly A microsatellite tract within TGF-beta 1RII occurs early and in a subset of unstable UC neoplasms and commonly in sporadic colorectal cancers but may be rare in unstable gastric and esophageal tumors.

Role of inherited defects of MYH in the development of sporadic colorectal cancer

Biallelic germ‐line variants of the 8‐hydroxyguanine repair gene MYH have been associated with multiple colorectal adenomas that display somatic G:C→T:A transversions in APC. However, the effect of single germ‐line variants has not been widely studied. To examine the relationship between monoallelic MYH variants and susceptibility to sporadic colorectal cancer (CRC), 92 cases of sporadic CRC, 19 cases of familial CRC not meeting the Bethesda guidelines, 17 cases with multiple adenomas, and 53 normal blood donors were screened for 8 potentially pathogenic germ‐line MYH variants. Loss of heterozygosity (LOH) at 1p adjacent to the MYH locus, microsatellite instability (MSI) status, and somatic mutations in KRAS2 and APC were analyzed in sporadic cancers. Neither homozygote nor compound heterozygote MYH variants were observed in the germ‐line of any subjects with sporadic CRC. There was no difference in the incidence of monoallelic variants between this group (20 of 92, 22%) and cancer‐free controls (14 of 53, 26%). However, the presence of monoallelic germ‐line MYH variants was negatively associated with an MSI‐high (MSI‐H) tumor phenotype, with an incidence of only 1 of 23 (4%) MSI‐H CRCs as contrasted with 19 of 69 (28%) non‐MSI‐H (P = 0.02). Further, 4 of 5 tumors with 1p LOH contained monoallelic MYH variants compared with 15 of 53 without 1p LOH (P = 0.04) and the normal population (P = 0.03). The presence of G:C→T:A transversions in KRAS2 or APC was significantly more common in single MYH variant tumors (9 of 12) than in MYH wild‐type tumors (11 of 33; P = 0.02). These results suggest that single germ‐line variants of MYH may influence genetic pathways in CRC.

Mutation of hMSH3 and hMSH6 mismatch repair genes in genetically unstable human colorectal and gastric carcinomas

Mutations within microsatellite sequences, consisting of additions or deletions of repeat units, are known as the replication/repair error positive (RER +) phenotype or micorsatellite instability (MI). Microsatellite instability has been demonstrated in hereditary and sporadic colorectal carcinomas and is usually observed in noncoding regions of genomic DNA. However, relatively few coding region targets of MI have been identified thus far. Using PCR, we amplified regions encompassing (A)8 and (C)8 microsatellite tracts within hMSH3 and hMSH6 from 31 RER+ sporadic colorectal tumors, 8 hereditary colon cancers, 23 RER+ gastric carcinomas, and 32 RER‐ gastric tumors. Mutations were found in 11 (36%) of 31 sporadic colon carcinomas, 4 (50%) of 8 hereditary colorectal cancers, and 5 (22%) of 23 RER+ gastric carcinomas, but in only 2 (6%) of 32 RER‐gastric carcinomas. These frameshift mutations cause premature stop codons downstream that are predicted to abolish normal protein function. Our results and those of others suggest that DNA mismatch repair genes, such as hMSH3 and hMSH6, are targets for the mutagenic activity of upstream mismatch repair gene mutations and that this enhanced genomic instability may accelerate the accumulation of mutations in RER+ tumors. Hum Mutat 10:474–478, 1997.

Quality Assessment and Correlation of Microsatellite Instability and Immunohistochemical Markers among Population- and Clinic-Based Colorectal Tumors: Results from the Colon Cancer Family Registry

The detection of defective mismatch repair (MMR), as assessed by the presence of tumor microsatellite instability (MSI) and/or loss of MMR protein expression by IHC, has been useful for risk assessment, prognosis, and prediction of treatment in patients with colorectal cancer. We analyzed tumors for the presence of defective MMR from 5927 Colorectal Cancer Family Registry patients recruited at six international consortium sites. We evaluated the appropriate percentage instability cutoff used to distinguish the three MSI phenotypes [ie, stable (MSS), low instability (MSI-L), and high instability (MSI-H)]; the sensitivity, specificity, and performance characteristics of individual markers; and the concordance between MSI and IHC phenotypes. Guided by the results of the IHC testing, our findings indicate that the distinction between an MSI-H phenotype from a low-instability or MSS phenotype can best be accomplished by using a cutoff of 30% or greater of the markers showing instability. The sensitivity and specificity of the mononucleotide markers were higher than those of the dinucleotide markers. Specifically, BAT26 and BAT25 had the highest sensitivity (94%) and specificity (98%), and the use of mononucleotide markers alone identified 97% of the MSI-H cases correctly. As expected, the presence of MSI-H correlated with an older age of diagnosis, the presence of tumor in the proximal colon, and female sex.

Rising incidence of early‐onset colorectal cancer in Australia over two decades: Report and review

The average age at diagnosis for colorectal cancer (CRC) in Australia is 69, and the age‐specific incidence rises rapidly after age 50 years. The incidence has stabilized or is declining in older age groups in Australia during recent decades, possibly related to the increased uptake of screening and high‐risk surveillance. In the same time frame, a rising incidence of CRC in younger adults has been well‐documented in the United States. This rise in incidence in the young has not been reported from other countries that share long‐term exposure to westernised urban lifestyles. Using data from the Australian Institute of Health and Welfare, we examined trends in national incidence rates for CRC under age 50 years and observed that rates in people under age 40 years have been rising for the last two decades. We further performed a review of the literature regarding CRC in young adults to outline the extent of current understanding, explore potential risk factors such as obesity, alcohol, and sedentary lifestyles, and to identify the questions remaining to be addressed. Although absolute numbers might not justify a population screening approach, the dispersal of young adults with CRC across the primary health‐care system decreases probability of their recognition. Patient and physician awareness, aided by stool and emerging blood‐screening tests and risk profiling tools, have the potential to aid in identification of those young adults who would most benefit from a colonoscopy through early detection of CRCs or by removal of advanced polyps.

The Association of Tumor Microsatellite Instability Phenotype with Family History of Colorectal Cancer

Family history is a strong predictor of colorectal cancer risk; however, a diagnosis of colorectal cancer among first-degree relatives has not been systematically investigated as a function of the colorectal cancer molecular subtypes related to tumor microsatellite instability (MSI) status. We investigated whether the observable familial colorectal cancer risks differed according to tumor MSI subtypes, stratified as MSI-High (>30% instability), MSI-Low (<30% instability), and MSS (no instability). Data from 3,143 population-based colorectal cancer cases from five institutions were assessed for family history according to the Amsterdam criteria and the Bethesda guidelines, age at diagnosis, sex, tumor location, and MSI status. The distribution of patient characteristics by MSI status was compared using polytomous logistic regression. Overall, 2.8% colorectal cancer cases met the Amsterdam criteria and 37% met the Bethesda guidelines. There were 14% MSI-High, 13% MSI-Low, and 73% MSS colorectal cancers. MSI-High (P < 0.0001) and MSI-Low tumors (P = 0.01) were more proximally located than MSS tumors. MSI-High tumors were more common among females (P < 0.001). The highest proportion of MSI-High tumors occurred in cases <40 years of age whereas the age-dependent distribution of MSI-Low tumors was unchanged. MSI-High tumors showed a statistically significant association with increasing numbers of first-degree relatives with colorectal cancer (P = 0.002); this association disappeared, however, when MSI-High cases meeting Amsterdam criteria were removed from the analysis. MSI-Low tumors did not show a similar association with family history of colorectal cancer. Familial risk associated with MSI-High tumors is primarily driven by the Amsterdam-criteria patients. MSI-Low tumors may represent a distinct subtype of colorectal cancer with respect to certain epidemiologic variables studied here. (Cancer Epidemiol Biomarkers Prev 2009;18(3):967–75)

Female Hormonal Factors and the Risk of Endometrial Cancer in Lynch Syndrome

IMPORTANCEnApart from hysterectomy, there is no consensus recommendation for reducing endometrial cancer risk for women with a mismatch repair gene mutation (Lynch syndrome).nnnOBJECTIVEnTo investigate the association between hormonal factors and endometrial cancer risk in Lynch syndrome.nnnDESIGN, SETTING, AND PARTICIPANTSnA retrospective cohort study included 1128 women with a mismatch repair gene mutation identified from the Colon Cancer Family Registry. Data were analyzed with a weighted cohort approach. Participants were recruited between 1997 and 2012 from centers across the United States, Australia, Canada, and New Zealand.nnnEXPOSURESnAge at menarche, first and last live birth, and menopause; number of live births; hormonal contraceptive use; and postmenopausal hormone use.nnnMAIN OUTCOMES AND MEASURESnSelf-reported diagnosis of endometrial cancer.nnnRESULTSnEndometrial cancer was diagnosed in 133 women (incidence rate per 100 person-years, 0.29; 95% CI, 0.24 to 0.34). Endometrial cancer was diagnosed in 11% (nu2009=u200970) of women with age at menarche greater than or equal to 13 years compared with 12.6% (nu2009=u200957) of women with age at menarche less than 13 years (incidence rate per 100 person-years, 0.27 vs 0.31; rate difference, -0.04 [95% CI, -0.15 to 0.05]; hazard ratio per year, 0.85 [95% CI, 0.73 to 0.99]; Pu2009=u2009.04). Endometrial cancer was diagnosed in 10.8% (nu2009=u200988) of parous women compared with 14.4% (nu2009=u200940) of nulliparous women (incidence rate per 100 person-years, 0.25 vs 0.43; rate difference, -0.18 [95% CI, -0.32 to -0.04]; hazard ratio, 0.21 [95% CI, 0.10 to 0.42]; Pu2009<u2009.001). Endometrial cancer was diagnosed in 8.7% (nu2009=u200970) of women who used hormonal contraceptives greater than or equal to 1 year compared with 19.2% (nu2009=u200957) of women who used contraceptives less than 1 year (incidence rate per 100 person-years, 0.22 vs 0.45; rate difference, -0.23 [95% CI, -0.36 to -0.11]; hazard ratio, 0.39 [95% CI, 0.23 to 0.64]; Pu2009<u2009.001). There was no statistically significant association between endometrial cancer and age at first and last live birth, age at menopause, and postmenopausal hormone use.nnnCONCLUSIONS AND RELEVANCEnFor women with a mismatch repair gene mutation, some endogenous and exogenous hormonal factors were associated with a lower risk of endometrial cancer. These directions and strengths of associations were similar to those for the general population. If replicated, these findings suggest that women with a mismatch repair gene mutation may be counseled like the general population in regard to hormonal influences on endometrial cancer risk.