Higher frequency of diploidy in young-onset microsatellite-stable colorectal cancer

Genomic landscape of diploid and aneuploid microsatellite stable early onset colorectal cancer

Although colorectal cancer (CRC) remains the second leading cause of cancer-related death in the United States, the overall incidence and mortality from the disease have declined in recent decades. In contrast, there has been a steady increase in the incidence of CRC in individuals under 50 years of age. Hereditary syndromes contribute disproportionately to early onset CRC (EOCRC). These include microsatellite instability high (MSI+) tumors arising in patients with Lynch Syndrome. However, most EOCRCs are not associated with familial syndromes or MSI+ genotypes. Comprehensive genomic profiling has provided the basis of improved more personalized treatments for older CRC patients. However, less is known about the basis of sporadic EOCRC. To define the genomic landscape of EOCRC we used DNA content flow sorting to isolate diploid and aneuploid tumor fractions from 21 non-hereditary cases. We then generated whole exome mutational profiles for each case and whole genome copy number, telomere length, and EGFR immunohistochemistry (IHC) analyses on subsets of samples. These results discriminate the molecular features of diploid and aneuploid EOCRC and provide a basis for larger population-based studies and the development of effective strategies to monitor and treat this emerging disease.

Early Onset Metastatic Colorectal Cancer: Current Insights and Clinical Management of a Rising Condition

Despite a recent overall decrease in colorectal cancer (CRC) incidence and mortality, there has been a significant rise in CRC diagnoses in young adults. Early onset colorectal cancer (EOCRC) is defined as CRC diagnosed before the age of 50. Possible predisposing conditions include not only genetic syndromes but also other risk factors, such as microbiome alteration, antibiotic exposure, obesity, diabetes mellitus, and inflammatory bowel disease. EOCRC tends to be diagnosed later than in the older counterpart because of a lack of awareness and the fact that screening for CRC usually starts at the age of 50. Furthermore, CRC in young adults seems to be related to unique molecular features and more aggressive clinical behavior. This paper aims to provide an in-depth review of this poorly understood subject, with a comprehensive review of the state of the art and considerations for future perspectives.

Early-Onset GI Cancers: Rising Trends, Genetic Risks, Novel Strategies, and Special Considerations

Cancers in young adults (commonly described as early-onset [EO] cancer) represent a group of malignancies that have unique and challenging biology and genetic, treatment, social, and psychological implications. Even more concerning is a rising trend of EO cancers in multiple tumor types. Research and investigation in EO cancers will help elucidate mechanisms of carcinogenesis, differences in biology and response to treatment, and the need for multidisciplinary care to ensure comprehensive treatment and support for young patients.

Patients with Early-Onset Colorectal Cancer Have an Increased Risk of Second Primary Malignancy

BACKGROUND

While overall colorectal cancer (CRC) rates in the USA are declining, the incidence of early-onset CRC (eoCRC) under age 50 is increasing. The aim of this study was to examine the risk of a second primary malignancy (SPM) in individuals with eoCRC, and how this risk compares to those with late-onset CRC (loCRC).

METHODS

We used data from the Surveillance, Epidemiology, and End Results Program database to examine the risk of SPM after a diagnosis of eoCRC. Standardized incidence ratios (SIR) were used to estimate the risk of SPM after eoCRC and loCRC in comparison with the risk of malignancy in the general population.

RESULTS

Compared to the general population, individuals with eoCRC, but not loCRC, had an increased lifetime risk of SPM (SIR 1.42, 95% CI 1.37-1.48 and SIR 1.00, 95% CI 0.99-1.02, respectively), and locations at highest risk were the small intestine, ureter, rectum, and colon. The risk of SPM after eoCRC was similar in men and women, but higher in non-whites compared to whites and higher in those with a lower area-level median household income. The risk of SPM following eoCRC was high in the first 5 years after diagnosis (SIR 2.44, 95% CI 2.24-2.66) and, in a birth cohort analysis, was found to be increasing over time.

CONCLUSIONS

Individuals with eoCRC have a lifetime risk of SPM nearly 50% higher than the general population. The risk of SPM is highest in the first 5 years after diagnosis and is increasing over time.

Epidemiology and biology of early onset colorectal cancer

Colorectal cancer (CRC) is the third leading cause of cancer-related mortality in men or women in the United States. Average-risk screening that begins at age 50 years has reduced incidence and mortality of CRC in those over 50 years of age, whereas CRC incidence in those under age 50 years (early onset colorectal cancer (eoCRC)) has recently and dramatically increased. In this review, we summarize the recent literature including risk factors for eoCRC, differences in clinicopathologic presentation and outcomes in eoCRC, and emerging evidence regarding the molecular pathways that are altered in eoCRC compared to later onset CRC (loCRC). Epidemiologic studies of eoCRC show predominance in distal colon and rectum, and association with several modifiable risk factors, including diabetes, obesity, diet, sedentary time, alcohol consumption and smoking. Data regarding potential risk factors of prior antibiotic exposure and microbiome alterations or direct carcinogen exposure are still emerging. Aggressive clinicopathologic features of eoCRC at presentation may be due to delay in diagnosis or more aggressive tumor biology. EoCRC outcomes are similar to loCRC when matched for stage, but overall mortality is greater due to higher frequency of advanced disease at a younger presentation, with more life-years lost. There are only few molecular evaluations of eoCRC to date, with findings of potential increase in TP53 and CTNNB1 somatic mutation and decrease in APC, KRAS and BRAF somatic mutation, compared to loCRC. Other findings include LINE-1 hypomethylation, absence of microsatellite instability (MSI-H), presence of chromosomal instability (CIN) or microsatellite and chromosomal stability (MACS). These studies are only now emerging and have not yet identified a specific molecular signature defining eoCRC. Further research evaluating genetic and molecular differences as well as environmental triggers for eoCRCs should provide a clearer understanding to inform targeted screening for pre-symptomatic at-risk younger individuals.

The Prevalence of Pathogenic or Likely Pathogenic Germline Variants in a Nationwide Cohort of Young Colorectal Cancer Patients Using a Panel of 18 Genes Associated with Colorectal Cancer

INTRODUCTION

The prevalence of pathogenic or likely pathogenic germline variants (PGV) in colorectal cancer (CRC) in young patients is seen in approximately one in five patients, with the majority of cases having gene variants associated with Lynch syndrome (LS). The primary aim was to describe the prevalence of 18 genes, all associated with hereditary polyposis and CRC, in a nationwide population of young CRC (yCRC) patients, and outline disease characteristics in patients with or without germline variants.

METHODS

We screened 98 patients aged 18-40 with CRC diagnosed in 2010-2013 for variants in MSH2, MSH6, MLH1, PMS2, EPCAM, APC, MUTYH, SMAD4, BMPR1A, STK11, PTEN, POLE, POLD1, NTHL1, AXIN2, MSH3, GREM1 and RNF43 using Next Generation Sequencing. Comparisons between patients' characteristics in patients with PGV, and patients without germline variants (NPGV) were analyzed.

RESULTS

PGV were detected in twenty-four patients (24.5%), and twenty-one patients (21.1%) had variants in the mismatch repair (MMR) genes associated with LS. Variants in the APC and MUTYH genes were detected in 1% and 4%, respectively. Patients with NPGV had more advanced disease with adverse histopathological features.

CONCLUSION

PGV was detected in one in four yCRC patients, and one in five yCRC patients had disease causing variants in the mismatch repair genes associated with LS.

Early age onset colorectal cancer

The incidence and mortality associated with colorectal cancer (CRC) diagnosed in patients under the age of 50 have been steadily increasing. The exact etiology of these epidemiologic trends is unclear. This chapter will provide a comprehensive review on the topic of early age onset colorectal cancer (EAO-CRC), defined as colorectal cancer (CRC) diagnosed in patients under the age of 50. Topics reviewed will include the epidemiology of EAO-CRC around the world, clinical and pathological features of EAO-CRC in contrast to later age onset CRC (CRC diagnosed on those over the age of 50) and the observed molecular and somatic characteristics. This chapter will review the etiologies to EAO-CRC and the established, as well as proposed risk factors for disease. Evidence-based approaches to prevention, early detection, treatment and survivorship will be presented.

The genetic and epigenetic landscape of early-onset colorectal cancer

Colorectal cancer (CRC) in individuals under the age of 50 is a problem that is increasing in USA and around the world. In this review, we discuss the degree to which early-onset (EO)CRC may be due to unsuspected Lynch syndrome or other inherited germline variants that predispose to cancer, describe the known somatic genetic alterations in EO tumors and discuss alterations in DNA methylation. Approximately 20% of EOCRCs can be attributed to identifiable germline mutations in genes that cause familial cancer syndromes. A variety of other genetic/epigenetic alterations have also been reported. We conclude that this is a heterogeneous problem, that requires a comprehensive analysis of genetic/epigenetic signatures to better understand EOCRC. Various subsets of EOCRCs must be analyzed individually for clues regarding the etiologies and possible specific therapies for this disease.

Disparate and Alarming Impact of Gastrointestinal Cancers in Young Adult Patients

BACKGROUND

The rise in the incidence of gastric cancer (GC) and colorectal cancer (CRC) in young adults (YA) remains unexplained. We aim to identify differences in these malignancies between YA and older patients.

PATIENTS AND METHODS

We retrospectively analyzed the California Cancer Registry for all GC and CRC cases from 2000 to 2012. Pearson's Chi square analysis and stepwise regression model with backward elimination were used to analyze differences in demographic, clinical, and histopathologic features, and log-rank test to compare survival between young (≤ 40 years) and older adults (41-90 years) with GC or CRC, separately.

RESULTS

We analyzed 19,368 cases of GC and 117,415 cases of CRC. YA accounted for 4.6% of GC (n = 883) and 2.8% of CRC (n = 3273) patients. Compared with older patients, YA were more likely to be Hispanic (P < 0.0001) and have poorly differentiated (P < 0.0001), higher histologic grade (P < 0.0001), and signet ring features (P < 0.0001). Synchronous peritoneal metastases were more common in YA patients (32.1% vs. 14.1% GC, 8.8% vs. 5.4% CRC, P < 0.0001). The 5-year overall survival (OS) of YA with CRC or GC was longer than that of older patients with the same stage of malignancy; except YA with stage I GC, who demonstrated poor OS and disease-specific survival (DSS) (65.1% and 67.9%, respectively) which were significantly worse than those of adults aged 41-49 years (70.7% and 76.2%, respectively) and 50-64 years (69.1% and 78.1%, respectively).

CONCLUSIONS

YA with GC or CRC have distinctly worse clinical and histopathologic features compared with older patients and are disproportionately of Hispanic ethnicity. These results contribute to improving understanding of younger versus older GI cancer patients.

Clinicopathological features and oncological outcomes of patients with young-onset rectal cancer

BACKGROUND

The incidence of rectal cancer among adults aged less than 50 years is rising. Survival data are limited and conflicting, and the oncological benefit of standard neoadjuvant and adjuvant therapies is unclear.

METHODS

Disease-specific outcomes of patients diagnosed with rectal cancer undergoing surgical resection with curative intent between 2006 and 2016 were analysed.

RESULTS

A total of 797 patients with rectal cancer were identified, of whom 685 had surgery with curative intent. Seventy patients were younger than 50 years and 615 were aged 50 years or more. Clinical stage did not differ between the two age groups. Patients aged less than 50 years were more likely to have microsatellite instability (9 versus 1·6 per cent; P = 0·003) and Lynch syndrome (7 versus 0 per cent; P < 0·001). Younger patients were also more likely to receive neoadjuvant chemoradiotherapy (67 versus 53·3 per cent; P = 0·003) and adjuvant chemotherapy (41 versus 24·2 per cent; P = 0·006). Five-year overall survival was better in those under 50 years old (80 versus 72 per cent; P = 0·013). The 5-year disease-free survival rate was 81 per cent in both age groups (P = 0·711). There were no significant differences in the development of locoregional recurrence or distant metastases.

CONCLUSION

Despite accessing more treatment, young patients have disease-specific outcomes comparable to those of their older counterparts.

Clinical and Genetic Characteristics of Colorectal Cancer in Persons under 50 Years of Age: A Review

BACKGROUND

The incidence of colorectal cancer (CRC) in persons under the age of 50 years (EOCRC) is increasing even as the incidence of CRC in persons over age 50 is decreasing. This has led to recommendations to lower the age of CRC screening to age 45. It is not clear whether EOCRC is identical to CRCs in older patients or whether there are distinctive features between the two groups.

AIMS AND METHODS

We reviewed the literature on the clinical and genetic aspects of EOCRC.

RESULTS

We found that there is an increased likelihood of a strong genetic basis for EOCRC, but that at least 80% of cases do not come from the known high-penetrance cancer syndromes. Early-onset CRCs tend to occur in the distal colon or rectum, are more likely to be detected due to cancer-related symptoms, appear to be increasing in whites more than non-whites on a population-wide analysis, and are more likely to present in an advanced stage of disease. There are some unique genetic features of EOCRC, including an increased proportion of tumors with LINE-1 hypomethylation, and combined chromosomal and microsatellite stability.

CONCLUSIONS

EOCRC deserves additional attention because of the high number of life years at risk with EOCRC, and the implications for earlier CRC screening. Additional focus is needed on determining whether some cases of EOCRC have a unique mechanistic basis.

Early onset sporadic colorectal cancer: Worrisome trends and oncogenic features

Early onset colorectal cancers, defined as arising before 50 years of age, are a growing health hazard in western and eastern countries alike. The incidence of colon and rectal cancers in young individuals is projected to increase by as much as 90% and 140%, respectively, by 2030. Although several known cancer risk factors (e.g. smoking, alcohol, dietary habits) have been investigated, there is no single compelling explanation for this epidemiological trend. While some early onset colorectal cancers have been associated with germline mutations in cancer predisposition genes, genetic syndromes are implicated in only a fraction of these cancers (20%) and do not explain the rising incidence. Colorectal neoplasms develop through microsatellite instability or chromosomal instability pathways, with most of the early onset colorectal cancers exhibiting microsatellite stable phenotypes. Genome-wide hypomethylation is a feature of a subgroup of early onset cancers, which appears to be correlated with chromosomal instability and poor prognosis.

Metachronous colon polyps in younger versus older adults: a case-control study

BACKGROUND AND AIMS

The incidence of colorectal cancer in the United States has decreased substantially in individuals aged 50 and older. In contrast, it is increasing in young adults. The polyp characteristics on baseline and follow-up colonoscopy in young adults are not well characterized. We describe the polyp characteristics on baseline and follow-up colonoscopy in adults <40 years and determined factors associated with the occurrence of metachronous, advanced neoplasia or high-risk (HR) polyp features. We compared the occurrence of metachronous advanced neoplasia in young adults with those 50 years and older to assess whether postpolypectomy surveillance guidelines seem appropriate for polyp-bearing adults less than age 40 years.

METHODS

Patients <40 years of age with >1 polyp removed on colonoscopy followed by a postpolypectomy colonoscopy were eligible. The primary outcome was the occurrence of advanced neoplasia or HR polyp features on follow-up colonoscopy. Secondary endpoints included factors associated with metachronous advanced neoplasia in young adults. The occurrence of metachronous advanced neoplasia in young adults was compared with a cohort of patients aged 50 years and older.

RESULTS

Included were 128 patients with a mean age of 34.9 years; 124 patients (97%) had adenomas and 7% had sessile serrated polyps (SSPs). Advanced neoplasia was seen in 35% of patients at baseline. The median follow-up time was 33.6 months. Metachronous advanced neoplasia was identified in 7% of patients on follow-up colonoscopy. Baseline factors associated with metachronous advanced neoplasia included the presence of an SSP (hazard ratio, 7.8; 95% CI, 1.09-56.3; P = .041) with a trend in those with advanced neoplasia (hazard ratio, 3.4; 95% confidence interval, .89-12.8; P = .072). The occurrence of metachronous advanced neoplasia did not differ between the young and older cohorts (7% vs 12.2%, P = .58); however, young adults were less likely to have HR polyp features on follow-up (8.6% vs 20.3%, P = .008).

CONCLUSIONS

More than 1 in 3 adults <40 years old undergoing colonoscopy had advanced neoplasia on baseline colonoscopy. The occurrence of metachronous advanced neoplasia in young adults is similar to older adults and appears to be associated with the size, pathology, and number of baseline polyps. Our data suggest young polyp-bearing adults may undergo postpolypectomy colonoscopy at intervals currently recommended by national guidelines. Confirmation in larger studies is warranted.

Young patients with colorectal cancer have increased risk of second primary cancers

OBJECTIVE

Because the number of long-term survivors of colorectal cancer has increased, second primary cancer has become an important issue. However, previous studies were heterogeneous in design, and few data for Asia-Pacific area were available.

METHODS

This was a retrospective population-based study conducted using the national database of the Taiwan Cancer Registry. Patients who have histology-proven primary colon cancer and rectal cancer from 1995 to 2005 were enrolled in this study. All second primary cancer events had to be histology proven. The standardized incidence ratio of second primary cancer was used as an indicator. Standardized incidence ratio was counted as the number of observed second primary cancer divided by the expected number of cancer cases in the general population.

RESULTS

A total of 65 648 eligible index patients were enrolled, and 3810 second primary cancer events were identified. The standardized incidence ratio for all of the patients was 1.03 (95% confidence interval: 0.99-1.06), which implied that the risk of second primary cancer was not significantly elevated in the index patients compared with that of the general population. The standardized incidence ratio for the patients aged <50, 50-70 and >70 years was 2.52 (95% confidence interval: 2.28-2.78), 1.18 (95% confidence interval: 1.12-1.23) and 0.80 (95% confidence interval: 0.76-0.84), respectively. In young patients (aged <50 years), the standardized incidence ratio increase was statistically significant and persisted for over 10 years and this significantly increased across all subgroups. The small intestine, the large intestine, the female genital organs and the lungs were the most common sites of second primary cancer in young patients.

CONCLUSIONS

Young patients with colorectal cancer have an increased risk of developing second primary cancer.

Copy number variations are progressively associated with the pathogenesis of colorectal cancer in ulcerative colitis

AIM: To evaluate the association of known copy number variations (CNVs) in ulcerative colitis (UC) progressing to colorectal cancer.

METHODS: Microsatellite instability analysis using the National Cancer Institute’s panel of markers, and CNV association studies using Agilent 2 × 105 k arrays were done in tissue samples from four patient groups with UC: those at low risk (LR) or high risk of developing colorectal cancer, those with premalignant dysplastic lesions, and those with colitis-associated colorectal cancer (CAC). DNA from tissue samples of these groups were independently hybridized on arrays and analyzed. The data obtained were further subjected to downstream bioinformatics enrichment analysis to examine the correlation with CAC progression.

RESULTS: Microarray analysis highlighted a progressive increase in the total number of CNVs [LR (n = 178) vs CAC (n = 958), 5.3-fold], gains and losses [LR (n = 37 and 141) vs CAC (n = 495 and 463), 13.4- and 3.3-fold, respectively], size [LR (964.2 kb) vs CAC (10540 kb), 10.9-fold] and the number of genes in such regions [LR (n = 119) vs CAC (n = 455), 3.8-fold]. Chromosome-wise analysis of CNVs also showed an increase in the number of CNVs across each chromosome. There were 38 genes common to all four groups in the study; 13 of these were common to cancer genes from the Genetic Disease Association dataset. The gene set enrichment analysis and ontology analysis highlighted many cancer-associated genes. All the samples in the different groups were microsatellite stable.

CONCLUSION: Increasing numbers of CNVs are associated with the progression of UC to CAC, and warrant further detailed exploration.

Comprehensive molecular characterisation of hereditary non-polyposis colorectal tumours with mismatch repair proficiency

BACKGROUND

Hereditary non-polyposis colorectal cancer (CRC) without mismatch repair (MMR) defects occurs in almost half of high-risk CRC families, but its genetic cause(s) is(are) still unknown. We aimed to identify unique molecular features that differentiate hereditary from sporadic MMR-proficient colorectal tumours.

METHODS

Genomic alterations in 16 tumours from 14 Amsterdam I-II families were studied using the genome-wide copy number OncoScan™ FFPE microarray. Somatic mutation hotspots in BRAF, KRAS, PIK3CA and TP53 were analysed in 37 colorectal tumours from 26 families and in 99 sporadic MMR-proficient CRCs, using direct automated sequencing and KASPar genotyping assays. CpG methylation index was studied in 25 tumours from 19 families by methylation-specific multiplex ligation-dependent probe amplification (MS-MLPA).

RESULTS

Our findings indicate that hereditary MMR-proficient tumours have overlapping genomic profiles to those obtained in sporadic cases, both suggestive of high chromosomal instability, and no high CpG methylation index. Nevertheless, we identified a significant increase in the frequency of chromosome 2p and 2q gains, and of 10 q loss in Amsterdam I families, as well as low frequency of >2 Mb copy-neutral or -gained loss of heterozygosity (LOH). No statistically significant differences in the frequency of BRAF, KRAS, PIK3CA and TP53 mutations or in the gene mutation patterns were observed. However, TP53 mutations appeared almost twice more frequently in sporadic tumours.

CONCLUSIONS

Overall, hereditary MMR-proficient CRCs display similar molecular characteristics than their sporadic counterparts. However, the differences identified, such as the chromosome 2 gain, 10 q loss, or the under-representation of TP53 mutations, if validated in larger series, might be of relevance in the clinical setting and/or in the identification of germline defects underlying some of these familial cases.

The increasing incidence of young-onset colorectal cancer: a call to action

In the United States, colorectal cancer (CRC) is the third most common and second most lethal cancer. More than one-tenth of CRC cases (11% of colon cancers and 18% of rectal cancers) have a young onset (ie, occurring in individuals younger than 50 years). The CRC incidence and mortality rates are decreasing among all age groups older than 50 years, yet increasing in younger individuals for whom screening use is limited and key symptoms may go unrecognized. Familial syndromes account for approximately 20% of young-onset CRCs, and the remainder are typically microsatellite stable cancers, which are more commonly diploid than similar tumors in older individuals. Young-onset CRCs are more likely to occur in the distal colon or rectum, be poorly differentiated, have mucinous and signet ring features, and present at advanced stages. Yet, stage-specific survival in patients with young-onset CRC is comparable to that of patients with later-onset cancer. Primary care physicians have an important opportunity to identify high-risk young individuals for screening and to promptly evaluate CRC symptoms. Risk modification, targeted screening, and prophylactic surgery may benefit individuals with a predisposing hereditary syndrome or condition (eg, inflammatory bowel disease) or a family history of CRC or advanced adenomatous polyps. When apparently average-risk young adults present with CRC-like symptoms (eg, unexplained persistent rectal bleeding, anemia, and abdominal pain), endoscopic work-ups can expedite diagnosis. Early screening in high-risk individuals and thorough diagnostic work-ups in symptomatic young adults may improve young-onset CRC trends.

Correlation of chromosomal instability, telomere length and telomere maintenance in microsatellite stable rectal cancer: a molecular subclass of rectal cancer

Introduction

Colorectal cancer (CRC) tumor DNA is characterized by chromosomal damage termed chromosomal instability (CIN) and excessively shortened telomeres. Up to 80% of CRC is microsatellite stable (MSS) and is historically considered to be chromosomally unstable (CIN+). However, tumor phenotyping depicts some MSS CRC with little or no genetic changes, thus being chromosomally stable (CIN-). MSS CIN- tumors have not been assessed for telomere attrition.

Experimental Design

MSS rectal cancers from patients ≤50 years old with Stage II (B2 or higher) or Stage III disease were assessed for CIN, telomere length and telomere maintenance mechanism (telomerase activation [TA]; alternative lengthening of telomeres [ALT]). Relative telomere length was measured by qPCR in somatic epithelial and cancer DNA. TA was measured with the TRAPeze assay, and tumors were evaluated for the presence of C-circles indicative of ALT. p53 mutation status was assessed in all available samples. DNA copy number changes were evaluated with Spectral Genomics aCGH.

Results

Tumors were classified as chromosomally stable (CIN-) and chromosomally instable (CIN+) by degree of DNA copy number changes. CIN- tumors (35%; n=6) had fewer copy number changes (<17% of their clones with DNA copy number changes) than CIN+ tumors (65%; n=13) which had high levels of copy number changes in 20% to 49% of clones. Telomere lengths were longer in CIN- compared to CIN+ tumors (p=0.0066) and in those in which telomerase was not activated (p=0.004). Tumors exhibiting activation of telomerase had shorter tumor telomeres (p=0.0040); and tended to be CIN+ (p=0.0949).

Conclusions

MSS rectal cancer appears to represent a heterogeneous group of tumors that may be categorized both on the basis of CIN status and telomere maintenance mechanism. MSS CIN- rectal cancers appear to have longer telomeres than those of MSS CIN+ rectal cancers and to utilize ALT rather than activation of telomerase.

Evidence for possible non-canonical pathway(s) driven early-onset colorectal cancer in India

Two genetic instability pathways viz. chromosomal instability, driven primarily by APC mutation induced deregulated Wnt signaling, and microsatellite instability (MSI) caused by mismatch repair (MMR) inactivation, together account for >90% of late-onset colorectal cancer (CRC). Our understanding of early-onset sporadic CRC is however comparatively limited. In addition, most seminal studies have been performed in the western population and analyses of tumorigenesis pathway(s) causing CRC in developing nations have been rare. We performed a comparative analysis of early and late-onset CRC from India with respect to common genetic aberrations including Wnt, KRAS, and p53 (constituting the classical CRC progression sequence) in addition to MSI. Our results revealed the absence of Wnt and MSI in a significant proportion of early-onset as against late-onset CRC in India. In addition, KRAS mutation frequency was significantly lower in early-onset CRC indicating that a significant proportion of CRC in India may follow tumorigenesis pathways distinct from the classical CRC progression sequence. Our study has therefore revealed the possible existence of non-canonical tumorigenesis pathways in early-onset CRC in India.

A high degree of LINE-1 hypomethylation is a unique feature of early-onset colorectal cancer

OBJECTIVE

Early-onset colorectal cancer (CRC) represents a clinically distinct form of CRC that is often associated with a poor prognosis. Methylation levels of genomic repeats such as LINE-1 elements have been recognized as independent factors for increased cancer-related mortality. The methylation status of LINE-1 elements in early-onset CRC has not been analyzed previously.

DESIGN

We analyzed 343 CRC tissues and 32 normal colonic mucosa samples, including 2 independent cohorts of CRC diagnosed ≤ 50 years old (n=188), a group of sporadic CRC >50 years (MSS n=89; MSI n=46), and a group of Lynch syndrome CRCs (n=20). Tumor mismatch repair protein expression, microsatellite instability status, LINE-1 and MLH1 methylation, somatic BRAF V600E mutation, and germline MUTYH mutations were evaluated.

RESULTS

Mean LINE-1 methylation levels (± SD) in the five study groups were early-onset CRC, 56.6% (8.6); sporadic MSI, 67.1% (5.5); sporadic MSS, 65.1% (6.3); Lynch syndrome, 66.3% (4.5) and normal mucosa, 76.5% (1.5). Early-onset CRC had significantly lower LINE-1 methylation than any other group (p<0.0001). Compared to patients with <65% LINE-1 methylation in tumors, those with ≥ 65% LINE-1 methylation had significantly better overall survival (p=0.026, log rank test).

CONCLUSIONS

LINE-1 hypomethylation constitutes a potentially important feature of early-onset CRC, and suggests a distinct molecular subtype. Further studies are needed to assess the potential of LINE-1 methylation status as a prognostic biomarker for young people with CRC.

Technologies supporting analytical cytology: clinical, research and drug discovery applications

The tools and techniques developed for analytical cytology have become invaluable in expanding the development of cancer screening programs and biomarker discovery for personalized medicine. Detecting cellular, molecular, and functional changes of diseased tissue as defined by quantitative analytical methodologies has enhanced the field of medical diagnostics and prognostics. The focus of this review is to outline applications and recent technical advances in flow cytometry, laser scanning cytometry, image cytometry, and quantitative image analysis, as they pertain to clinical, research, and drug discovery applications.

MSH6 and MUTYH deficiency is a frequent event in early-onset colorectal cancer

PURPOSE

Early-onset colorectal cancer (CRC) is suggestive of a hereditary predisposition. Lynch syndrome is the most frequent CRC hereditary cause. The MUTYH gene has also been related to hereditary CRC. A systematic characterization of these two diseases has not been reported previously in this population.

EXPERIMENTAL DESIGN

We studied a retrospectively collected series of 140 patients ≤50 years old diagnosed with nonpolyposis CRC. Demographic, clinical, and familial features were obtained. Mismatch repair (MMR) deficiency was determined by microsatellite instability (MSI) analysis, and immunostaining for MLH1, MSH2, MSH6, and PMS2 proteins. Germline MMR mutations were evaluated in all MMR-deficient cases. Tumor samples with loss of MLH1 or MSH2 protein expression were analyzed for somatic methylation. Germline MUTYH mutations were evaluated in all cases. BRAF V600E and KRAS somatic mutational status was also determined.

RESULTS

Fifteen tumors (11.4%) were MSI, and 20 (14.3%) showed loss of protein expression (7 for MLH1/PMS2, 2 for isolated MLH1, 3 for MSH2/MSH6, 7 for isolated MSH6, and 1 for MSH6/PMS2). We identified 11 (7.8%) germline MMR mutations, 4 in MLH1, 1 in MSH2, and 6 in MSH6. Methylation analysis revealed one case with somatic MLH1 methylation. Biallelic MUTYH mutations were detected in four (2.8%) cases. KRAS and BRAF V600E mutations were present in 39 (27.9%) and 5 (3.6%) cases, respectively.

CONCLUSIONS

Loss of MSH6 expression is the predominant cause of MMR deficiency in early-onset CRC. Our findings prompt the inclusion of MSH6 and MUTYH screening as part of the genetic counseling of these patients and their relatives.

[Early-onset colorectal carcinoma study]

Early-onset colorectal carcinoma (before the age of 45 years) are a distinct clinical group characterized by frequent distal location, poor cellular differentiation and aggressive evolution. A systematic study of early-onset cancers without familial predisposition in the context of the CIT program of "la Ligue Nationale Contre le Cancer" has been set up to characterize molecular mechanisms of carcinogenesis of these tumors. Preliminary results of transcriptome analysis show different gene-expression profiles among age. The next step will consist in validating a molecular signature specific for early-onset carcinoma. Genomic profile does not differ from that observed in late-onset colon cancers.

Telomere length, oxidative damage, antioxidants and breast cancer risk

Telomeres play a critical role in maintaining the integrity and stability of the genome, and are susceptible to oxidative damage after telomere shortening to a critical length. In the present study, we explored the role of white blood cell DNA telomere length on breast cancer risk, and examined whether urinary 15-F(2)-isoprostanes (15-F(2t)-IsoP) and 8-oxo-7,8-dihydrodeoxyguanosine (8-oxodG) or dietary antioxidant intake modified the relationship between telomere length and breast cancer risk. A population-based case-control study-the Long Island Breast Cancer Study Project-was conducted among 1,067 cases and 1,110 controls. Telomere length was assessed by quantitative PCR. Overall, the mean levels of telomere length (T/S ratio), 15-F(2t)-IsoP and 8-oxodG were not significantly different between cases and controls. Among premenopausal women only, carrying shorter telomeres (Q3 and Q4), as compared with the longest (Q1), was associated with significantly increased breast cancer risk. Age-adjusted OR and 95% CI were 1.71 (1.10-2.67) and 1.61 (1.05-2.45). The 5-F(2t)-IsoP and 8-oxodG biomarkers did not modify the telomere-breast cancer association. A moderate increase in breast cancer risk was observed among women with the shortest telomeres (Q4) and lower dietary and supplemental intake of beta-carotene, vitamin C or E intake [OR (95% CI) = 1.48 (1.08-2.03), 1.39 (1.01-1.92) and 1.57 (1.14-2.18), respectively], although the trend test exhibited statistical significance only within the lower vitamin E intake subgroup (p(trend) = 0.01). These results provided the strongest evidence to date that breast cancer risk may be affected by telomere length among premenopausal women or women with low dietary intake of antioxidants or antioxidant supplements.

Chromosomal instability in near-diploid colorectal cancer: a link between numbers and structure

Chromosomal instability (CIN) plays a crucial role in tumor development and occurs mainly as the consequence of either missegregation of normal chromosomes (MSG) or structural rearrangement (SR). However, little is known about the respective chromosomal targets of MSG and SR and the way these processes combined within tumors to generate CIN. To address these questions, we karyotyped a consecutive series of 96 near-diploid colorectal cancers (CRCs) and distinguished chromosomal changes generated by either MSG or SR in tumor cells. Eighty-three tumors (86%) presented with chromosomal abnormalities that contained both MSGs and SRs to varying degrees whereas all 13 others (14%) showed normal karyotype. Using a maximum likelihood statistical method, chromosomes affected by MSG or SR and likely to represent changes that are selected for during tumor progression were found to be different and mostly mutually exclusive. MSGs and SRs were not randomly associated within tumors, delineating two major pathways of chromosome alterations that consisted of either chromosome gains by MSG or chromosomal losses by both MSG and SR. CRCs showing microsatellite instability (MSI) presented with either normal karyotype or chromosome gains whereas MSS (microsatellite stable) CRCs exhibited a combination of the two pathways. Taken together, these data provide new insights into the respective involvement of MSG and SR in near-diploid colorectal cancers, showing how these processes target distinct portions of the genome and result in specific patterns of chromosomal changes according to MSI status.

Is early-onset microsatellite and chromosomally stable colorectal cancer a hallmark of a genetic susceptibility syndrome?

Most colorectal cancers show either microsatellite or chromosomal instability. A subset of colorectal cancers, especially those diagnosed at young age, is known to show neither of these forms of genetic instability and thus might have a distinct pathogenesis. Colorectal cancers diagnosed at young age are suggestive for hereditary predisposition. We investigate whether such early-onset microsatellite and chromosomally stable colorectal cancers are a hallmark of a genetic susceptibility syndrome. The ploidy status of microsatellite stable (familial) colorectal cancers of patients diagnosed before age 50 (n = 127) was analyzed in relation to the histopathological characteristics and family history. As a control the ploidy status of sporadic colorectal cancer, with normal staining of mismatch repair proteins, diagnosed at the age of 69 years or above (n = 70) was determined. A diploid DNA content was used as a marker for chromosomal stability. Within the group of patients with (familial) early onset microsatellite stable colorectal cancer the chromosomally stable tumors did not differ from chromosomally unstable tumors with respect to mean age at diagnosis, fulfillment of Amsterdam criteria or pathological characteristics. Segregation analysis did not reveal any family with microsatellite and chromosomally stable colorectal cancer in 2 relatives. The prevalence of microsatellite and chromosomally stable colorectal cancer was not significantly different for the early and late onset group (28 and 21%, respectively). We find no evidence that early-onset microsatellite and chromosomally stable colorectal cancer is a hallmark of a hereditary colorectal cancer syndrome.