Exome and immune cell score analyses reveal great variation within synchronous primary colorectal cancers

A clinico-pathological and molecular analysis reveals differences between solitary (early and late-onset) and synchronous rectal cancer

Rectal cancer (RC) appears to behave differently compared with colon cancer. We aimed to analyze existence of different subtypes of RC depending on distinct features (age of onset and the presence of synchronous primary malignant neoplasms). We compared the clinicopathological, familial and molecular features of three different populations diagnosed with RC (early-onset RC [EORC], late-onset RC, and synchronous RC [SRC]). Eighty-five RCs were identified and were evaluated according to their microsatellite instability, CpG Island Methylator Phenotype (CIMP) and chromosomal instability, as assessed by Next Generation Sequencing and microarray-based comparative genomic hybridization approaches. The results were subjected to cluster analysis. SRCs displayed the most specific characteristics including a trend for the development of multiple malignant neoplasms, a greater proportion of CIMP-High tumors (75%) and more frequent genomic alterations. These findings were confirmed by a clustering analysis that stratified RCs according to their genomic alterations. We also found that EORCs exhibited their own features including an important familial cancer component and a remarkable rate of mutations in TP53 (53%). Together, heterogeneity in RC characteristics by age of disease-onset and SRC warrants further study to optimize tailored prevention, detection and intervention strategies-particularly among young adults.

Copy neutral loss of heterozygosity (cnLOH) patterns in synchronous colorectal cancer

Copy neutral loss of heterozygosity (cnLOH) is a common event in several human malignancies-positing this as a mechanism of carcinogenesis. However, the role of cnLOH in synchronous colorectal cancer (SCRC), a unique CRC subtype, is not well understood. The aim of this study was to establish a cnLOH profile of SCRC using a single-nucleotide polymorphism array (SNP-A), and to explore associations between cnLOH and the genomic landscape of frequently mutated genes in SCRC. Among 74 paired SCRC cases, the most frequently altered regions were 16p11.2-p11.1 (59.5%) and 11p11.2-p11.12 (28.4%). Notably, the 6q11.21-q11.22 region altered by cnLOH was uniquely associated with polyclonal SCRCs (p = 0.038). Together, our analysis suggests that inactivation of tumor suppressor genes and cnLOH are rare events among SCRC cases. This study defines distinct patterns of cnLOH in SCRC, and provides initial evidence of a role for cnLOH in SCRC etiology.

Personalised mapping of tumour development in synchronous colorectal cancer patients

Synchronous colorectal cancers (syCRCs) are two or more primary tumours identified simultaneously in a patient. Previous studies report high inter-tumour heterogeneity between syCRCs, suggesting independent origin and different treatment response, making their management particularly challenging, with no specific guidelines currently in place. Here, we performed in-depth bioinformatic analyses of genomic and transcriptomic data of a total of eleven syCRCs and one metachronous CRC collected from three patients. We found mixed microsatellite status between and within patients. Overlap of mutations between synchronous tumours was consistently low (<0.5%) and heterogeneity of driver events across syCRCs was high in all patients. Microbial analysis revealed the presence of Fusobacterium nucleatum species in patients with MSI tumours, while quantification of tumour immune infiltration showed varying immune responses between syCRCs. Our results suggest high heterogeneity of syCRCs within patients but find clinically actionable biomarkers that help predict responses to currently available targeted therapies. Our study highlights the importance of personalised genome and transcriptome sequencing of all synchronous lesions to aid therapy decision and improve management of syCRC patients.

53BP1 expression and immunoscore are associated with the efficacy of neoadjuvant chemoradiotherapy for rectal cancer

PURPOSE

Considering the effects of P53 binding protein 1 (53BP1) expression and T lymphocyte infiltration density on tumor radiosensitivity, we investigated the relation of 53BP1 expression and immunoscore based on T lymphocyte infiltration density with the efficacy of neoadjuvant chemoradiotherapy (CRT) for rectal cancer.

METHODS

Fifty-five patients with rectal cancer receiving neoadjuvant CRT followed by surgery were enrolled. The 53BP1 expression level and the density of CD3⁺, CD8⁺, and CD45RO⁺ T lymphocytes in the tumor tissues were examined by immunohistochemistry, and the relation of these findings to the rates of tumor regression, disease-free survival (DFS), and overall survival (OS) was analyzed.

RESULTS

The levels of 53BP1 and the CD3/CD8 immunoscore were closely correlated with the response to CRT (p < 0.05), with an area under the receiver operating characteristic curve for CRT efficacy prediction of 0.626 and 0.717, respectively. Further survival analysis revealed that high 53BP1 expression effectively prolonged 2‑year DFS compared with low 53BP1 expression (87.5% [95%CI 77.3-97.7] vs. 53.3% [95%CI 28.1-78.6]; p < 0.05), while the effect of immunoscore on survival was restricted by the expression status of 53BP1. Cox multivariate analysis confirmed 53BP1 as an independent prognostic factor in DFS.

CONCLUSION

The pretreatment levels of 53BP1 and the immunoscore based on CD3⁺/CD8⁺ T cell infiltration density in tumor tissues are effective predictors for the CRT response, and 53BP1 has a more pronounced impact on prognosis.