Project description:Background & Aims: The metastatic process is complex and remains a major obstacle in the management of colorectal cancer (CRC). To gain a better insight into the biologic events driving the metastatic process we investigated genomic aberrations in a large cohort of matched CRC primaries and distant metastases from various sites. Methods: In total, 62 primary colorectal cancers, 62 matched normal specimens, and 68 matched metastases (from liver, lung, ovary, omentum, and distant lymph nodes) were analyzed by high resolution array comparative genomic hybridization (array CGH) for DNA copy number changes. Findings were validated using a publicly available dataset consisting of 21 primary tumors and matched liver metastases. Fluorescence in situ hybridization (FISH) was used to confirm some of the DNA copy number changes observed. Results: Overall patterns of DNA copy number aberrations were highly similar between primary tumors and their metastases, confirming clonality. Additional copy number aberrations in metastasis are rare and rather than recurrent they were sporadic for individual patients. The only recurrent differences between primary tumors and their metastases were two chromosomal regions, 6q21 and 8q24.21 encompassing the MYC oncogene, that coamplified in three metastases of two patients (3.2%). FISH analysis confirmed the high level co-amplification in the metastasis, which were not detected in their primary tumors. Conclusions: Primary CRC and their metastases show highly similar patterns of DNA copy number changes, additional copy number aberrations in metastasis are rare and recurrences exceptional. These observations are consistent with the hypothesis that the metastatic potential is predestined early in the development of the primary tumor. In total, 62 primary colorectal cancers, 62 matched normal specimens, and 68 matched metastases (liver, lung, ovarian, omentum and distant lymph nodes) were analyzed by high resolution array comparative genomic hybridization (array CGH).

Project description:Background: Liver metastasis is the major cause of death following a diagnosis of colorectal cancer (CRC) and is a major health burden. Most molecular studies of CRC have profiled primary tumor samples and not the metastasis samples. In this study, we compared the copy number profiles of matched primary and liver metastatic CRC to better understand how the genomic structure of primary CRC differs from the metastasis. This has important implications for whether it is justified to base therapeutic approaches solely on data from the primary tumour. Methods: Paired primary and metastatic tumours from 16 patients and their adjacent normal tissue samples were analyzed using Single-Nucleotide-Polymorphism (SNP) arrays to determine copy number alterations. Nine patients had a synchronous liver metastasis at the time of CRC diagnosis and 7 patients developed a liver metastasis metachronously. Genome-wide chromosomal copy number alterations were assessed, with particular attention to 189 genes known to be somatically altered in CRC and 25 genes that are clinically actionable in CRC. These data were analyzed with respect to the timing of primary and metastatic tissue resection and with exposure to chemotherapy. Results: The genomic divergence with the whole genome duplication correction applied the average percent copy number discordance across all pairs of samples was 22.02%. The pairs of tumour samples collected prior to treatment revealed a significantly higher copy number differences compared to previously treated liver metastasis samples (P=0.024). However, loss of heterozygosity (LOH) acquired in metastasis was significantly higher in previously treated liver metastasis samples compared to treatment naïve liver metastasis samples (P= 0.0064) and which included where KRAS mutation was present in the primary cancers but was not detectable in the metastatic sample following chemotherapy. With regard to 25 genes that are clinically actionable in CRC, amplification of the genes ERBB2, FGFR1, CDK8 or PIK3CA was observed in the metastatic tissue of 4 patients but not in the matched primary CRC. In these cases, knowledge of these metastatic specific alterations could have informed therapeutic decision making and may have improved patient outcome. Conclusion: Intra-patient genomic discrepancies observed between primary and metastatic tissue

Project description:Lymph-node (LN) metastases predict for high recurrence rates in breast cancer patients. Eradication of micro-metastatic tumor cells is the primary goal of adjuvant systemic treatment. Decisions regarding systemic treatment depend largely on primary tumor characteristics rather than on characteristics of their LN metastases. However, it remains unclear to what extent LN metastases, having already metastasized locally, resemble their primary breast tumors and as such will be eradicated by the systemic therapy chosen. In this study we investigated the genetic differences between primary breast cancers and their paired LN metastases using array comparative genomic hybridization analyses on a high resolution 720K Nimblegen platform. Thus far, no metastasis-specific genomic aberrations have been identified. We hypothesized that this is due to low-resolution platforms and lack of stratification on breast cancer subtypes (specifically, triple-negative (TN) versus luminal). Furthermore, we speculated that as TN tumours are known to be more genetically unstable, their LN metastases would show an increase in random copy number aberrations (CNAs). Therefore, we studied 10 primary TN breast tumour–LN pairs and 10 luminal pairs and found that all LN metastases clustered nearest to their matched tumour except for two. These two were explained by poor hybridization quality and, interestingly, the presence of two histological components in one tumour. We found no significantly altered CNAs between pairs in the whole group, nor when subdivided over subtypes; neither did we find a CNA increase in LN metastases compared to primary tumours within the TN subgroup, suggesting most CNAs are functional and not random. Our findings suggest a strong clonal relationship between primary breast tumours and its LN metastases and support the use of the primary tumor characteristics to guide adjuvant systemic chemotherapy in breast cancer patients, since primary tumors and their subsequent LN metastases seem remarkably similar, at least prior to treatment. The experiment contains 27 paired primary breast cancer samples with their lymph node metastases, analysed on a 135K whole genome CGH array

Project description:Lymph-node (LN) metastases predict for high recurrence rates in breast cancer patients. Eradication of micro-metastatic tumor cells is the primary goal of adjuvant systemic treatment. Decisions regarding systemic treatment depend largely on primary tumor characteristics rather than on characteristics of their LN metastases. However, it remains unclear to what extent LN metastases, having already metastasized locally, resemble their primary breast tumors and as such will be eradicated by the systemic therapy chosen. In this study we investigated the genetic differences between primary breast cancers and their paired LN metastases using array comparative genomic hybridization analyses on a high resolution 720K Nimblegen platform. Thus far, no metastasis-specific genomic aberrations have been identified. We hypothesized that this is due to low-resolution platforms and lack of stratification on breast cancer subtypes (specifically, triple-negative (TN) versus luminal). Furthermore, we speculated that as TN tumours are known to be more genetically unstable, their LN metastases would show an increase in random copy number aberrations (CNAs). Therefore, we studied 10 primary TN breast tumour–LN pairs and 10 luminal pairs and found that all LN metastases clustered nearest to their matched tumour except for two. These two were explained by poor hybridization quality and, interestingly, the presence of two histological components in one tumour. We found no significantly altered CNAs between pairs in the whole group, nor when subdivided over subtypes; neither did we find a CNA increase in LN metastases compared to primary tumours within the TN subgroup, suggesting most CNAs are functional and not random. Our findings suggest a strong clonal relationship between primary breast tumours and its LN metastases and support the use of the primary tumor characteristics to guide adjuvant systemic chemotherapy in breast cancer patients, since primary tumors and their subsequent LN metastases seem remarkably similar, at least prior to treatment.

Dataset Information

Chromosomal copy number aberrations in colorectal metastases resemble their primary counterparts and differences are typically non-recurrent.

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