Single-cell and bulk transcriptome sequencing identifies two epithelial tumor cell states and refines the consensus molecular classification of colorectal cancer.

The consensus molecular subtype (CMS) classification of colorectal cancer is based on bulk transcriptomics. The underlying epithelial cell diversity remains unclear. We analyzed 373,058 single-cell transcriptomes from 63 patients, focusing on 49,155 epithelial cells. We identified a pervasive genetic and transcriptomic dichotomy of malignant cells, based on distinct gene expression, DNA copy number and gene regulatory network. We recapitulated these subtypes in bulk transcriptomes from 3,614 patients. The two intrinsic subtypes, iCMS2 and iCMS3, refine CMS. iCMS3 comprises microsatellite unstable (MSI-H) cancers and one-third of microsatellite-stable (MSS) tumors. iCMS3 MSS cancers are transcriptomically more similar to MSI-H cancers than to other MSS cancers. CMS4 cancers had either iCMS2 or iCMS3 epithelium; the latter had the worst prognosis. We defined the intrinsic epithelial axis of colorectal cancer and propose a refined 'IMF' classification with five subtypes, combining intrinsic epithelial subtype (I), microsatellite instability status (M) and fibrosis (F).

Trends in the surgical management of rectal prolapse: An Asian experience.

BACKGROUND: Posterior compartment pelvic floor prolapse (PCPFP) leads to anatomical distortion and functional impairment. Definitive management involves surgery. Ventral mesh rectopexy (VMR) has gained increasing popularity in the West as it emerges as a durable approach. Existing literature and evidence on safety and efficacy of PCPFP surgery in the Asian population remains sparse. Our study aims to review our institution's experience in surgery for PCPFP. METHODS: All cases of PCPFP surgery in Singapore General Hospital between 2014 to 2019 were studied. RESULTS: Eighty-three patients had surgery performed for PCPFP, with the majority (83%) in the last 3 years. Median age was 63 years and 92% were female. Most patients (64%) had obstructive defecation symptoms, while the remaining had fecal incontinence, rectal bleeding, or anal discomfort. Main anatomical indication for surgery was external rectal prolapse (48%). Other indications were rectocele and/or rectal intussusception. The majority (66%) had abdominal rectopexy, while 28 underwent Delorme's procedure. Forty-five of the 50 VMRs were minimally invasive. Patients undergoing rectopexy were observed to be younger. Median length of stay was 3 days. Nine patients had early operative complications of which ileus was most common. Median length of follow-up was 12 months. The majority (93%) had initial symptom satisfaction. Eleven patients had anatomical recurrence with a median length of 9 months to development. There was no significant difference in outcomes between abdominal vs perineal approach, or laparoscopic vs robotic VMR. CONCLUSION: Surgery for PCPFP has gained acceptance in our Asian institution with good symptom improvement, alongside low morbidity and recurrence.

Bystander CD8+ T cells are abundant and phenotypically distinct in human tumour infiltrates.

Various forms of immunotherapy, such as checkpoint blockade immunotherapy, are proving to be effective at restoring T cell-mediated immune responses that can lead to marked and sustained clinical responses, but only in some patients and cancer types1-4. Patients and tumours may respond unpredictably to immunotherapy partly owing to heterogeneity of the immune composition and phenotypic profiles of tumour-infiltrating lymphocytes (TILs) within individual tumours and between patients5,6. Although there is evidence that tumour-mutation-derived neoantigen-specific T cells play a role in tumour control2,4,7-10, in most cases the antigen specificities of phenotypically diverse tumour-infiltrating T cells are largely unknown. Here we show that human lung and colorectal cancer CD8+ TILs can not only be specific for tumour antigens (for example, neoantigens), but also recognize a wide range of epitopes unrelated to cancer (such as those from Epstein-Barr virus, human cytomegalovirus or influenza virus). We found that these bystander CD8+ TILs have diverse phenotypes that overlap with tumour-specific cells, but lack CD39 expression. In colorectal and lung tumours, the absence of CD39 in CD8+ TILs defines populations that lack hallmarks of chronic antigen stimulation at the tumour site, supporting their classification as bystanders. Expression of CD39 varied markedly between patients, with some patients having predominantly CD39- CD8+ TILs. Furthermore, frequencies of CD39 expression among CD8+ TILs correlated with several important clinical parameters, such as the mutation status of lung tumour epidermal growth factor receptors. Our results demonstrate that not all tumour-infiltrating T cells are specific for tumour antigens, and suggest that measuring CD39 expression could be a straightforward way to quantify or isolate bystander T cells.

Individualised multiplexed circulating tumour DNA assays for monitoring of tumour presence in patients after colorectal cancer surgery.

Circulating tumour DNA (ctDNA) has the potential to be a specific biomarker for the monitoring of tumours in patients with colorectal cancer (CRC). Here, our aim was to develop a personalised surveillance strategy to monitor the clinical course of CRC after surgery. We developed patient-specific ctDNA assays based on multiplexed detection of somatic mutations identified from patient primary tumours, and applied them to detect ctDNA in 44 CRC patients, analysing a total of 260 plasma samples. We found that ctDNA detection correlated with clinical events - it is detectable in pre-operative but not post-operative plasma, and also in patients with recurrent CRC. We also detected ctDNA in 11 out of 15 cases at or before clinical or radiological recurrence of CRC, indicating the potential of our assay for early detection of metastasis. We further present data from a patient with multiple primary cancers to demonstrate the specificity of our assays to distinguish between CRC recurrence and a second primary cancer. Our approach can complement current methods for surveillance of CRC by adding an individualised biological component, allowing us not only to point to the presence of residual or recurrent disease, but also attribute it to the original cancer.

Risk Factors for Recurrence After Laparoscopic Ventral Rectopexy.

BACKGROUND: Laparoscopic ventral rectopexy effectively treats posterior compartment prolapse. However, recurrence after laparoscopic ventral rectopexy is poorly understood. OBJECTIVE: This study aimed to evaluate factors contributing to recurrence after laparoscopic ventral rectopexy. DESIGN: A retrospective cohort analysis was performed of patients who underwent laparoscopic ventral rectopexy between June 2008 and June 2014. Patients presenting with full-thickness rectal prolapse were compared against the rest. Cox proportional hazards regression was used to determine predictors for recurrence. Operative findings of redo cases were evaluated. SETTINGS: This study was conducted under the supervision of a single pelvic floor surgeon. PATIENTS: A total of 231 patients with a median follow-up of 47 months were included. MAIN OUTCOME MEASURES: Clinicopathological risk factors and technical failures contributing to recurrence were analyzed. RESULTS: The overall recurrence rate was 11.7% (n = 27). Twenty-five recurrences occurred in patients with full-thickness rectal prolapse, of which 16 were full-thickness recurrences (14.2% (16/113)). Multivariate analyses showed predictors for recurrence to be prolonged pudendal nerve terminal motor latency (HR = 5.57 (95% CI, 1.13 - 27.42); p = 0.04) and the use of synthetic mesh as compared with biologic grafts (HR = 4.24 (95% CI, 1.27-14.20); p = 0.02). Age >70 years and poorer preoperative continence were also associated with recurrence on univariate analysis. Technical failures contributing to recurrence included mesh detachment from the sacral promontory and inadequate midrectal mesh fixation. LIMITATIONS: Modifications to the operative technique were made throughout the study period. A postoperative defecating proctogram was not routinely performed. CONCLUSIONS: Recurrence after laparoscopic ventral rectopexy is multifactorial, and risk factors are both clinical and technical. The use of biologic grafts was associated with lower recurrence as compared with synthetic mesh. Patients with full-thickness rectal prolapse who are elderly, have poorer baseline continence, and have prolonged pudendal nerve terminal motor latency are at increased risk of recurrence.