Jessica Pérez

DNA Copy Number Profiling Reveals Different Patterns of Chromosomal Instability Within Colorectal Cancer According to the Age of Onset

Chromosomal instability resulting in copy number alterations is a hallmark of colorectal cancer (CRC). However, few studies have attempted to characterize the chromosomal changes occurring in early‐onset CRC in order to compare them with those taking place within the more extensively studied late‐onset CRC subset. Our aim was to characterize the genomic profiles of these two groups of colorectal tumors and to compare them to each other. Array comparative genomic hybridization profiling of 146 colorectal tumors (60 early‐onset and 86 late‐onset) in combination with an unsupervised analysis was used to define common and specific copy number alterations. We found a number of important differences between the chromosomal instability profiles of each age subset. Thus, losses at 1p36, 1p12, 1q21, 9p13, 14q11, 16p13, and 16p12 were significantly more frequent in younger patients, whereas gains at 7q11 and 7q22 were more frequent in older patients. Moreover, the unsupervised analysis stratified the tumors into two clusters, each one of which was enriched in patients from one of the age subsets. Our findings confirm the existence of substantial differences between the chromosomal instability profiles of the two groups which are more important from a qualitative point of view. Further studies are needed to understand the clinicopathological implications of these dissimilarities.

Toward a Molecular Classification of Synchronous Colorectal Cancer: Clinical and Molecular Characterization

Background Two or more primary colorectal tumors coexisting at the time of diagnosis are considered to be synchronous tumors. It is estimated that synchronous colorectal cancer (SCRC) only accounts for 1.1% to 8.1% of all colorectal cancers (CRCs), and its molecular basis is still poorly understood. Patients and Methods We evaluated the microsatellite instability (MSI) and the CpG island methylator phenotype (CIMP) statuses in a series of 49 patients (98 tumors) diagnosed with sporadic SCRC at the 12 de Octubre University Hospital with the aim of improving the molecular characterization of this type of tumor. We considered Lynch syndrome, familial adenomatous polyposis, and MUTYH‐associated polyposis (MAP) as exclusion criteria. Results Molecular subgrouping on the basis of MSI and CIMP enabled us to define 4 groups that corresponded to the molecular classification proposed for single‐tumor CRC. We observed a significant predominance of MSI tumors at the right side regardless of the methylation pattern, and a significant prevalence of microsatellite‐stable tumors either at the left side or throughout the entire colon (P = .026). Furthermore, we defined some molecular features frequently observed in sporadic SCRC such as a low‐frequency of MSI (8.2%). We observed a high concordance in terms of MSI between simultaneous tumors (93.9%) and a lower concordance in terms of CIMP (51%) between such tumors. Conclusion Our findings support the hypothesis that SCRC involves an environmental rather than a genetic component in which various etiologic factors might modify tumor progression. Further studies are required to refine the molecular characterization of SCRC. Micro‐Abstract On the basis of microsatellite instability (MSI) and CpG island methylator phenotype, we performed a molecular subgrouping of 49 patients diagnosed with synchronous colorectal cancer (SCRC). Our results suggest that MSI is an infrequent feature in sporadic SCRC (8.2%) commonly related with the right side of the colon regardless of the methylation pattern.

Differential clinicopathological and molecular features within late-onset colorectal cancer according to tumor location

Background Since there is a predilection of some clinical and molecular features for a given tumor location, we assessed whether this can be confirmed in late-onset colorectal cancer (LOCRC). Results Right colon cancers showed features associated with sporadic Microsatellite Instability: predominance of female cases and BRAF mutations, and an important mucinous component. Left colon cancers developed a higher number of polyps and multiple primary CRCs, showed the strongest familial component, and had better prognosis. Rectal cancers showed a predominantly sporadic phenotype, with worse prognosis and a CpG Island Methylator Phenotype (CIMP)-High. No copy number alterations (CNAs) greater than or equal to 50% were observed in this LOCRC group, and the most recurrent alterations were losses at 5q13 and 14q11, and gains at 7q11, 7q21-q22, 19p13-p12, 19q13 and 20p11-q11. KRAS and PIK3CA were the only mutated genes showing differences according to the tumor location, mainly for right colon cancers. Materials and Methods We analyzed clinical and molecular characteristics of LOCRC at different tumor locations in order to determine if there are differential phenotypes related with the location in the colon. Conclusions Categorizing LOCRC according to tumor location appears to be an adequate first step to resolving the heterogeneity of this subset of CRC.

Redefining synchronous colorectal cancers based on tumor clonality: Clonality and synchronous colorectal cancer

To analyze the possible clonal origin of a part of Synchronous colorectal cancer (SCRC), we studied 104 paired‐SCRCs from 52 consecutive patients without hereditary forms of CRC. We used a Single‐Nucleotide Polymorphism array to characterize the genomic profiles, and subsequently used a statistical application to define them according to clonality within the same individual. We categorized the ensuing groups according to colonic location to identify differential phenotypes. The SCRC Monoclonal group (M) (19 cases) was divided into Monosegmental (MM) and Pancolonic (MP) groups. The SCRC Polyclonal group (P) (33 cases) was also divided into Monosegmental (PM) and Pancolonic (PP), the first exhibiting preference for left colon. The MM group showed a high rate of mucinous tumors, the lowest mean‐number of tumors and associated‐polyps, and the worst prognosis. The MP group included the largest mean‐number of associated‐polyps, best prognosis and familial cancer component. The PM group seemed to be a “frontier” group. Finally, the PP group also exhibited a mucin component, the highest mean‐number of tumors (4.6) compared with the mean‐number of polyps (7.7), poor prognosis and sporadic cases. Most relevant differential genomic regions within M groups were gains on 1q24 and 8q24, and deletions on 1p21 and 1p23 for MM, while within P were the gains on 7q36 and deletions on 1p36 for PM. The statistical application employed seems to define clonality more accurately in SCRC ‐more likely to be polyclonal in origin‐, and together with the tumor locations, helped us to configure a classification with prognostic and clinical value.

Comment on ‘Distinct clinical outcomes of two CIMP-positive colorectal cancer subtypes based on a revised CIMP classification system’

Comment on ‘Distinct clinical outcomes of two CIMP-positive colorectal cancer subtypes based on a revised CIMP classification system’

NOMO-1 gene is deleted in early-onset colorectal cancer

To characterize clinical features of a recurrent alteration in 16p13.12-p13.11 in Colorectal Cancer (CRC), mainly in Early-onset subgroup (EOCRC), and to assess the status of NOMO1, a gene located in that region, we analyzed differential clinicopathological, familial and molecular features of CRC subsets with and without alterations in the 16p13.12-p13.11, in global and EOCRC groups. We confirmed the region by fluorescence in-situ hybridization, and Quantitative Real-Time PCR analyzed the status of NOMO1 in different age-of-onset and Microsatellite Instability (MSI)-status CRC subsets. Both age-of-onset subsets were subsequently extended to further confirm NOMO1 gene changes. 16p13.12-p13.11 alterations were observed in 23.3% of CRCs, and was detected more frequently in EOCRC (33.3%) than in late-onset CRC (16.3%). The group with deletion in 16p showed a higher frequency of females and left-colon locations; a better prognosis; and higher Chromosomal Instability. Within the primary EOCRC population, 34 out of 34 of tumours showed a homozygous deletion in NOMO1, while in the late-onset population only 2 of the 17 tumours (11.7%) showed it. In the extended group, we found 61 out of 75 EOCRC patients (81.3%) with homozygous deletion and 7 patients (9.3%) with heterozygous deletion of NOMO1; moreover, in the new 50 late-onset patients, the proportions of deletions decreased. Microsatellite-Stable (MSS) EOCRC showed a very high proportion of homozygous loss of NOMO1 (54 of 59 cases, 91.5%), while the deletion was observed in only 7 out of 16 MSI cases. Deletion of NOMO1 is a molecular marker predominantly associated with EOCRC, particularly MSS subtypes.

Unsupervised Analysis of Array Comparative Genomic Hybridization Data from Early-Onset Colorectal Cancer Reveals Equivalence with Molecular Classification and Phenotypes

AIM: To investigate whether chromosomal instability (CIN) is associated with tumor phenotypes and/or with global genomic status based on MSI (microsatellite instability) and CIMP (CpG island methylator phenotype) in early-onset colorectal cancer (EOCRC). METHODS: Taking as a starting point our previous work in which tumors from 60 EOCRC cases (≤45 years at the time of diagnosis) were analyzed by array comparative genomic hybridization (aCGH), in the present study we performed an unsupervised hierarchical clustering analysis of those aCGH data in order to unveil possible associations between the CIN profile and the clinical features of the tumors. In addition, we evaluated the MSI and the CIMP statuses of the samples with the aim of investigating a possible relationship between copy number alterations (CNAs) and the MSI/CIMP condition in EOCRC. RESULTS: Based on the similarity of the CNAs detected, the unsupervised analysis stratified samples into two main clusters (A, B) and four secondary clusters (A1, A2, B3, B4). The different subgroups showed a certain correspondence with the molecular classification of colorectal cancer (CRC), which enabled us to outline an algorithm to categorize tumors according to their CIMP status. Interestingly, each subcluster showed some distinctive clinicopathological features. But more interestingly, the CIN of each subcluster mainly affected particular chromosomes, allowing us to define chromosomal regions more specifically affected depending on the CIMP/MSI status of the samples. CONCLUSIONS: Our findings may provide a basis for a new form of classifying EOCRC according to the genomic status of the tumors.

Comment on 'Wild-type APC prediction of poor prognosis in microsatellite-stable proximal colorectal cancer differs according to the age of onset'.

Comment on ‘Wild-type APC prediction of poor prognosis in microsatellite-stable proximal colorectal cancer differs according to the age of onset’