Colorectal cancer (CRC) is 3rd most commonly diagnosed cancer in males and the second in females. PD-1/PD-L1 axis, as an immune checkpoint, is up-regulated in many tumors and their microenvironment. However, the prognostic value of PD-1/PD-L1 in CRC remains unclear. The Cancer Genome Atlas (TCGA) database (N = 356) and Fudan University Shanghai Cancer Center (FUSCC) cohort of patients (N = 276) were adopted to analyze the prognostic value of PD-L1 in colorectal tumor cells (TCs) and of PD-1 in tumor infiltrating cells (TILs) for CRC. Subgroup analyses were conducted in FUSCC cohort according to patients’ status of mismatch repair. In TCGA cohort, the cut-off values of PD-1 and PD-L1 expression were determined by X-tile program, which were 4.40 and 2.92, respectively. Kaplan-Meier analysis indicated that higher PD-1 and PD-L1 expressions correlated with better OS (P = 0.032 and P = 0.002, respectively). In FUSCC cohort, expressions of PD-1 on TILs and PD-L1 on TCs were analyzed separately by immunohistochemistry (IHC) staining based on a TMA sample (N = 276) and revealed that both TILs-PD-1 and TCs-PD-L1 were associated with OS (P = 0.006 and P = 0.002, respectively) and DFS (P = 0.025 and P = 0.004, respectively) of CRC patients. Multivariate Cox regression analysis indicated TILs-PD-1 was an independent prognostic factor both for OS and DFS of CRC patients (P < 0.05). Subgroup analyses showed that TILs-PD-1 was an independent prognostic factor for both OS and DFS in CRC patients in MSS-proficient subgroup (P < 0.05), while neither of them correlated with OS or DFS in MSS-deficient subgroup (P > 0.05). Higher expressions of PD-1 and PD-L1 correlates with better prognosis of CRC patients. TILs-PD-1 is an independent prognostic factor for OS and DFS of CRC patients, especially for MMR-proficient subgroup.

Background: Oxaliplatin is one of the most widely used chemotherapy drugs for colorectal cancer (CRC). Resistance to oxaliplatin threatens the prognosis of CRC. Since previous studies have aroused interest in fatty acid metabolism in cancer, in this study, we determined whether fatty acid biosynthesis and the related regulating mechanism contribute to oxaliplatin resistance in CRC. Methods: The effect of the fatty acid synthase (FASN) and its inhibitor Orlistat was characterized in Gene Expression Omnibus (GEO) databases, oxaliplatin-resistant cell lines, and xenografts. MRNA-seq and analysis identified related pathway changes after the application of Orlistat, which was verified by Western blotting. Results: By leveraging the GEO databases, FASN and closely related gene signatures were identified as being correlated with the response to oxaliplatin-based chemotherapy and poor prognosis. Additionally, FASN-upregulated expression promoted oxaliplatin resistance in CRC cell lines. We then applied Orlistat, a typical FASN inhibitor, in cell culture and xenograft models of oxaliplatin-resistant CRC, which attenuated the resistance to oxaliplatin. Additionally, the combination of the FASN inhibitor and oxaliplatin significantly increased cell cycle arrest and facilitated apoptosis, partly due to the diminished phosphorylation of the MAPK/ERK and PI3K/AKT pathways. In vivo studies showed that inhibiting fatty acid biosynthesis with Orlistat restrained the growth of xenograft tumors and increased the responsiveness to oxaliplatin. Conclusions: Our study revealed that FASN enhanced resistance to oxaliplatin in CRC. The inhibition of FASN could rescue the response to oxaliplatin by regulating MAPK/ERK and PI3K/AKT pathways.

Background: Low expression of FOXE1, a member of Forkhead box (FOX) transcription factor family that plays vital roles in cancers, contributes to poor prognosis of colorectal cancer (CRC) patients. However, the underlying mechanism remains unclear. Materials and methods: The effects of FOXE1 on the growth of colon cancer cells and the expression of glycolytic enzymes were investigated in vitro and in vivo. Molecular biological experiments were used to reveal the underlying mechanisms of altered aerobic glycolysis. CRC tissue specimens were used to determine the clinical association of ectopic metabolism caused by dysregulated FOXE1. Results: FOXE1 is highly expressed in normal colon tissues compared with cancer tissues and low expression of FOXE1 is significantly associated with poor prognosis of CRC patients. Silencing FOXE1 in CRC cell lines dramatically enhanced cell proliferation and colony formation and promoted glucose consumption and lactate production, while enforced expression of FOXE1 manifested the opposite effects. Mechanistically, FOXE1 bound directly to the promoter region of HK2 and negatively regulated its transcription. Furthermore, the expression of FOXE1 in CRC tissues was negatively correlated with that of HK2. Conclusion: FOXE1 functions as a critical tumor suppressor in regulating tumor growth and glycolysis via suppressing HK2 in CRC.

The effect of adjuvant radiotherapy on the survival outcomes of patients with mucinous rectal cancer remains unclear. This study evaluated the 5-year cause specific survival (CSS) of patients with mucinous rectal cancer after surgery to determine whether adjuvant radiotherapy conferred a survival benefit. An analysis of the Surveillance, Epidemiology, and End Results (SEER)-registered database was conducted of patients presenting with mucinous rectal cancer between 2004 and 2011. The primary endpoint was 5-year CSS; univariate and multivariate analyses were performed using Cox proportional hazards regression models. A total of 574 patients were included for analysis with 248 patients in postoperative radiotherapy group and 326 patients in surgery alone group. Preliminary analysis demonstrated that adjuvant radiotherapy was not associated with CSS (χ 2 = 0.560, P = 0.454). Subgroup analysis indicated that postoperative radiotherapy group had survival advantage in stage II rectal cancer (93.3% vs. 76.6%, χ 2 = 4.654, P = 0.031), but not in stage III rectal cancer (67.5% vs. 64.7%, χ 2 = 0.186, P = 0.666). Multivariate analysis demonstrated that postoperative radiotherapy group had a reduced risk of death on survival (HR 0.346; 95%CI 0.129-0.927, P = 0.035) Postoperative radiotherapy is an independent factor for improvement in CSS in patients with stage II rectal mucinous adenocarcinoma, and it should be routinely recommended in these patients. But for stage III patients, considering the losing of CSS advantage and potential radiotherapy toxicity, postoperative radiotherapy should be recommended with great caution.