Background Dickkopf 1 (DKK1) is associated with tumor progression. However, whether DKK1 influences the tumor response to programmed cell death protein 1 (PD-1) blockade in colorectal cancers (CRCs) with deficient mismatch repair (dMMR) or microsatellite instability (MSI) has never been clarified. Methods Tumor tissues from 80 patients with dMMR CRC were evaluated for DKK1 expression and immune status via immunohistochemistry. Serum DKK1 was measured in another set of 43 patients who received PD-1 blockade therapy. CT26 cells and dMMR CRC organoids were cocultured with T cells, and CT26-grafted BALB/c mice were also constructed. T-cell cytotoxicity was assessed by apoptosis assays and flow cytometry. The pathway through which DKK1 regulates CD8+ T cells was investigated using RNA sequencing, and chromatin immunoprecipitation and luciferase reporter assays were conducted to determine the downstream transcription factors of DKK1. Results Elevated DKK1 expression was associated with recurrence and decreased CD8+ T-cell infiltration in dMMR CRCs, and patients with high-serum DKK1 had a poor response to PD-1 blockade. RNA interference or neutralization of DKK1 in CRC cells enhanced CD8+ T-cell cytotoxicity, while DKK1 decreased T-bet expression and activated GSK3β in CD8+ T cells. In addition, E2F1, a downstream transcription factor of GSK3β, directly upregulated T-bet expression. In organoid models, the proportion of apoptotic cells was elevated after individual neutralization of PD-1 or DKK1 and was further increased on combined neutralization of PD-1 and DKK1. Conclusions DKK1 suppressed the antitumor immune reaction through the GSK3β/E2F1/T-bet axis in CD8+ T cells. Elevated serum DKK1 predicted poor tumor response to PD-1 blockade in dMMR/MSI CRCs, and DKK1 neutralization may restore sensitivity to PD-1 blockade.

β2-microglobulin (B2M) and Janus kinases 1 and 2 (JAK1/2) mutations have been suggested as genetic mechanisms of immune evasion for anti–programmed cell death protein 1 (PD-1) therapy. Whether B2M and JAK1/2 lose-of-function mutation can cause primary resistance to anti-PD-1 therapy in colorectal carcinoma (CRC) patients remains controversial. Here, we sought to compare the efficacy of anti-PD-1 therapy in DNA mismatch repair deficient/microsatellite instability–high CRC patients with or without B2M or JAK1/2 mutations. Thirty-Five CRC patients who received anti-PD-1 therapy were enrolled in this study. All tumor samples underwent next-generation sequencing. The clinical and molecular data from 110 CRC patients sequenced with the Memorial Sloan Kettering-Integrated Mutation Profiling of Actionable Cancer Targets (MSK-IMPACT) assay and accessed through cBioportal were also analyzed in this study. Of the 35 CRC patients from our center, 10 (28.6%) had a B2M loss-of-function mutation, and 8 (22.9%) had a JAK1/2 loss-of-function mutation. Compared with B2M wild-type CRCs, B2M-mutated CRCs did not show a higher frequency of resistance to anti-PD-1 therapy (P=0.71). There was even better response to anti-PD-1 therapy in patients with JAK1/2 mutation than in those without (P=0.015). Of the 110 CRC patients in the MSK-IMPACT datasets, 13 (11.8%) had a B2M mutation, and 15 (13.6%) had a JAK1/2 mutation. After analyzing the response to anti-PD-1 therapy in these 110 patients, we found similar results (P=0.438 and 0.071, respectively). Moreover, patients with B2M or JAK1/2 mutation had a lower tumor mutational burden score compared with those without. B2M and JAK1/2 loss-of-function mutations occur frequently in microsatellite instability–high CRC. Our study demonstrated that patients with CRC harboring B2M or JAK1/2 mutations should not be excluded from anti-PD-1 therapy.

In a portion of patients with DNA mismatch repair-deficient (dMMR)/microsatellite instability-high (MSI-H) rectal cancer, clinical complete response (cCR) could be achieved after anti-programmed cell death protein 1 (anti-PD-1) immunotherapy. However, no data are available concerning the safety of omitting surgery and adopting immunotherapy as a curative-intent treatment for these patients. We retrospectively collected a series of patients with dMMR/MSI-H rectal adenocarcinoma who had cCR after receiving anti-PD-1 immunotherapy and adopted immunotherapy as curative-intent treatment from six institutions. Survival outcomes were analysed using the Kaplan-Meier method. Nineteen patients were included with a median age of 48 (range 19-63). One patient was diagnosed with stage I disease, four with stage II disease and fourteen with stage III disease. Sixteen patients received anti-PD-1 immunotherapy as the first line of therapy, and eleven patients were treated with single-agent anti-PD-1 antibodies. The median time from the start of treatment to cCR was 3.8 (range 0.7-6.5) months. During a median follow-up of 17.1 (range 3.1-33.5) months since achieving cCR, no local or distant relapse was observed. Two-year local recurrence-free survival, distant metastasis-free survival, disease free-survival and overall survival for the whole cohort were 100%, 100%, 100% and 100%, respectively. For patients with dMMR/MSI-H locally advanced rectal cancer who achieved cCR during anti-PD-1 immunotherapy, adopting immunotherapy as curative-intent treatment might be an alternative option. Longer follow-up and larger cohorts are warranted to verify this innovative treatment approach.

Purpose Universal germline testing in patients with colorectal cancer (CRC) with a multigene panel can detect various hereditary cancer syndromes. This study was performed to understand how to choose a testing panel and whether the result would affect clinical management. Methods We prospectively enrolled 486 eligible patients with CRC, including all patients with CRC diagnosed under age 70 years and patients with CRC diagnosed over 70 years with hereditary risk features between November 2017 and January 2018. All participants received germline testing for various hereditary cancer syndromes. Results The prevalence of germline pathogenic variants (PVs) in cancer susceptibility genes was 7.8% (38/486), including 25 PVs in genes with high-risk CRC susceptibility (the minimal testing set) and 13 PVs in genes with moderate-risk CRC susceptibility or increased cancer risk other than CRC (the additional testing set). All the clinically relevant PVs were found in patients diagnosed under age 70 years. Among them, 11 patients would not have been diagnosed if testing reserved to present guidelines. Most (36/38) of the patients with PVs benefited from enhanced surveillance and tailored treatment. PVs in genes from the minimal testing set were found in all age groups, while patients carried PVs in genes from the additional testing set were older than 40 years. Conclusion Universal germline testing for cancer susceptibility genes should be recommended among all patients with CRC diagnosed under age 70 years. A broad panel including genes from the additional testing set might be considered for patients with CRC older than 40 years to clarify inheritance risks. Trial registration number NCT03365986.

Background: A comprehensive investigation into immune cell infiltration provides more accurate and reliable prognostic information for patients with colorectal liver oligometastases (CLO) after liver metastasectomy. Methods: Simultaneous detection of the immune constituents CD3⁺, CD8⁺, Foxp3⁺ T, and α-SMA⁺ cells in the liver oligometastasis of 133 patients was conducted using a four-colour immunohistochemical multiplex technique. Immune cells were quantified, and tumour-infiltrating lymphocyte (TIL) ratios were subsequently calculated. Correlation analysis was performed using Pearson’s correlation. Recurrence-free survival (RFS) and overall survival (OS) for TIL ratios were analysed using the Kaplan–Meier method and Cox regression models. Results: Significantly fewer CD3⁺, CD8⁺, and Foxp3⁺ T cells were observed in the intratumoural region than in the peritumoural region of liver metastases. CD3⁺, CD8⁺, Foxp3⁺ T, and α-SMA⁺ cells showed significantly positive correlations with each other both in the intratumoural and peritumoural regions of liver metastases. Only the CD8/CD3 TIL ratio demonstrated a positive correlation between intratumoural and peritumoural regions of liver metastases (r = 0.541, p < 0.001). Patients with high intratumoural CD8/CD3 ratios had significantly longer 3-year RFS (59.0% vs. 47.4%, p = 0.035) and 3-year OS rates (83.3% vs. 65.8%, p = 0.007) than those with low intratumoural CD8/CD3 ratios. Multivariate analyses revealed that the intratumoural CD8/CD3 ratio was independently associated with RFS (HR = 0.593; 95% CI = 0.357–0.985; p = 0.043) and OS (HR = 0.391; 95% CI = 0.193–0.794; p = 0.009). Conclusion: These findings offer a better understanding of the prognostic value of immune cell infiltration on liver oligometastasis from colorectal cancer.