Novel drug resistance mechanisms and drug targets in BRAF-mutated peritoneal metastasis from colorectal cancer.

BACKGROUND: Patients with peritoneal metastasis from colorectal cancer (PM-CRC) have inferior prognosis and respond particularly poorly to chemotherapy. This study aims to identify the molecular explanation for the observed clinical behavior and suggest novel treatment strategies in PM-CRC. METHODS: Tumor samples (230) from a Norwegian national cohort undergoing surgery and hyperthermic intraperitoneal chemotherapy (HIPEC) with mitomycin C (MMC) for PM-CRC were subjected to targeted DNA sequencing, and associations with clinical data were analyzed. mRNA sequencing was conducted on a subset of 30 samples to compare gene expression in tumors harboring BRAF or KRAS mutations and wild-type tumors. RESULTS: BRAF mutations were detected in 27% of the patients, and the BRAF-mutated subgroup had inferior overall survival compared to wild-type cases (median 16 vs 36 months, respectively, p < 0.001). BRAF mutations were associated with RNF43/RSPO aberrations and low expression of negative Wnt regulators (ligand-dependent Wnt activation). Furthermore, BRAF mutations were associated with gene expression changes in transport solute carrier proteins (specifically SLC7A6) and drug metabolism enzymes (CES1 and CYP3A4) that could influence the efficacy of MMC and irinotecan, respectively. BRAF-mutated tumors additionally exhibited increased expression of members of the novel butyrophilin subfamily of immune checkpoint molecules (BTN1A1 and BTNL9). CONCLUSIONS: BRAF mutations were frequently detected and were associated with particularly poor survival in this cohort, possibly related to ligand-dependent Wnt activation and altered drug transport and metabolism that could confer resistance to MMC and irinotecan. Drugs that target ligand-dependent Wnt activation or the BTN immune checkpoints could represent two novel therapy approaches.

A comprehensive framework for analysis of microRNA sequencing data in metastatic colorectal cancer.

Although microRNAs (miRNAs) contribute to all hallmarks of cancer, miRNA dysregulation in metastasis remains poorly understood. The aim of this work was to reliably identify miRNAs associated with metastatic progression of colorectal cancer (CRC) using novel and previously published next-generation sequencing (NGS) datasets generated from 268 samples of primary (pCRC) and metastatic CRC (mCRC; liver, lung and peritoneal metastases) and tumor adjacent tissues. Differential expression analysis was performed using a meticulous bioinformatics pipeline, including only bona fide miRNAs, and utilizing miRNA-tailored quality control and processing. Five miRNAs were identified as up-regulated at multiple metastatic sites Mir-210_3p, Mir-191_5p, Mir-8-P1b_3p [mir-141-3p], Mir-1307_5p and Mir-155_5p. Several have previously been implicated in metastasis through involvement in epithelial-to-mesenchymal transition and hypoxia, while other identified miRNAs represent novel findings. The use of a publicly available pipeline facilitates reproducibility and allows new datasets to be added as they become available. The set of miRNAs identified here provides a reliable starting-point for further research into the role of miRNAs in metastatic progression.

T cell receptor repertoire sequencing reveals chemotherapy-driven clonal expansion in colorectal liver metastases.

BACKGROUND: Colorectal liver metastasis (CLM) is a leading cause of colorectal cancer mortality, and the response to immune checkpoint inhibition (ICI) in microsatellite-stable CRC has been disappointing. Administration of cytotoxic chemotherapy may cause increased density of tumor-infiltrating T cells, which has been associated with improved response to ICI. This study aimed to quantify and characterize T-cell infiltration in CLM using T-cell receptor (TCR) repertoire sequencing. Eighty-five resected CLMs from patients included in the Oslo CoMet study were subjected to TCR repertoire sequencing. Thirty-five and 15 patients had received neoadjuvant chemotherapy (NACT) within a short or long interval, respectively, prior to resection, while 35 patients had not been exposed to NACT. T-cell fractions were calculated, repertoire clonality was analyzed based on Hill evenness curves, and TCR sequence convergence was assessed using network analysis. RESULTS: Increased T-cell fractions (10.6% vs. 6.3%) were detected in CLMs exposed to NACT within a short interval prior to resection, while modestly increased clonality was observed in NACT-exposed tumors independently of the timing of NACT administration and surgery. While private clones made up >90% of detected clones, network connectivity analysis revealed that public clones contributed the majority of TCR sequence convergence. CONCLUSIONS: TCR repertoire sequencing can be used to quantify T-cell infiltration and clonality in clinical samples. This study provides evidence to support chemotherapy-driven T-cell clonal expansion in CLM in a clinical context.

Laparoscopic versus open liver resection in the posterosuperior segments: a sub-group analysis from the OSLO-COMET randomized controlled trial.

BACKGROUND: Laparoscopic liver resection in the posterosuperior segments is technically challenging. This study aimed to compare the perioperative outcomes for laparoscopic and open resection of colorectal liver metastases located in the posterosuperior segments. METHODS: This was a subgroup analysis of the OSLO-COMET randomized controlled trial, where 280 patients were randomly assigned to open or laparoscopic parenchyma-sparing liver resections of colorectal metastases. Patients with tumors in the posterosuperior segments were identified, and perioperative outcomes and health related quality of life (HRQoL) were compared. RESULTS: We identified a total of 136 patients, 62 in the laparoscopic and 74 in the open group. The postoperative complication rate was 26% in the laparoscopic and 31% in the open group. The blood loss was less in the open group (500 vs. 250 ml, P = 0.006), but the perioperative transfusion rate was similar. The operative time was similar, while postoperative hospital stay was shorter in the laparoscopic group (2 vs. 4 days, P < 0.001). HRQoL was significantly better after laparoscopy at 1 month. CONCLUSION: In patients undergoing laparoscopic or open liver resection of colorectal liver metastases in the posterosuperior segments, laparoscopic surgery was associated with shorter hospital stay and comparable perioperative outcomes.

RAS Mutation Clinical Risk Score to Predict Survival After Resection of Colorectal Liver Metastases.

OBJECTIVE: To determine the impact of RAS mutation status on the traditional clinical score (t-CS) to predict survival after resection of colorectal liver metastases (CLM). BACKGROUND: The t-CS relies on the following factors: primary tumor nodal status, disease-free interval, number and size of CLM, and carcinoembryonic antigen level. We hypothesized that the addition of RAS mutation status could create a modified clinical score (m-CS) that would outperform the t-CS. METHODS: Patients who underwent resection of CLM from 2005 through 2013 and had RAS mutation status and t-CS factors available were included. Multivariate analysis was used to identify prognostic factors to include in the m-CS. Log-rank survival analyses were used to compare the t-CS and the m-CS. The m-CS was validated in an international multicenter cohort of 608 patients. RESULTS: A total of 564 patients were eligible for analysis. RAS mutation was detected in 205 (36.3%) of patients. On multivariate analysis, RAS mutation was associated with poor overall survival, as were positive primary tumor lymph node status and diameter of the largest liver metastasis >50 mm. Each factor was assigned 1 point to produce a m-CS. The m-CS accurately stratified patients by overall and recurrence-free survival in both the initial patient series and validation cohort, whereas the t-CS did not. CONCLUSIONS: Modifying the t-CS by replacing disease-free interval, number of metastases, and CEA level with RAS mutation status produced an m-CS that outperformed the t-CS. The m-CS is therefore a simple validated tool that predicts survival after resection of CLM.