Improved diagnostic value by combining plasma PON1 level with tumor biomarkers in Colorectal Cancer patients.

The incidence of colorectal cancer (CRC) ranks third among all cancers in China and improvements in screening for CRC have an important impact on prevention and control of the disease. Paraoxonase 1 (PON1) is a calcium ion-dependent hydrolase that is widely distributed in tissue. Its diagnostic value in colorectal cancer has been reported, but the diagnostic value of combining PON1 with carcinoembryonic antigen (CEA), carbohydrate antigen 19-9 (CA19-9), carbohydrate antigen 12-5 (CA12-5) in colorectal cancer has not been evaluated. Experiments were carried out in a total of 284 CRC patients and 90 healthy controls. The primary cohort was randomly divided into training and validation sets. The levels of PON1 in plasma of CRC patients were significantly lower than that in the healthy controls (P < 0.001). It showed excellent diagnostic value with the AUC reaching 0.750 for the training set and 0.742 for the validation set. Furthermore, combining PON1 with CEA, CA12-5, CA19-9 could better classify CRC patients (AUC rising from 0.821, 0.716, 0.712 to 0.875, 0.817 and 0.814, respectively, in the training set, from 0.818, 0.581, 0.593 to 0.854, 0.770, and 0.772 in the validation set). In conclusion, PON1 can serve as a diagnostic biomarker for CRC and raise the sensitivity and specificity when incorporated with traditional tumor biomarkers.

miR-448 targets IDO1 and regulates CD8+ T cell response in human colon cancer.

BACKGROUND: Indoleamine 2,3-dioxygenase 1 (IDO1) is a critical regulator of T cell function, contributing to immune tolerance. Upregulation of IDO1 has been found in many cancer types; however, the regulatory mechanisms and clinical significance of IDO1 in colon cancer are still unclear. Here, we investigated the role of dysregulated microRNA (miRNA) targeting IDO1 in the colon cancer microenvironment. METHODS: We elucidated IDO1 function by performing cell-based assays and establishing transplanted tumor models in BALB/c mice and BALB/c nude mice. We evaluated IDO1 protein expression by immunohistochemistry (IHC) in a tissue microarray (TMA) and analyzed IDO1 mRNA expression with The Cancer Genome Atlas (TCGA). We screened miRNAs targeting IDO1 by using a dual luciferase reporter assay. We tested the function of microRNA-448 (miR-448) by using western blotting (WB) and fluorescence-activated cell sorting (FACS). RESULTS: We demonstrated that stable IDO1 overexpression enhanced xenograft tumor growth in BALB/c mice but not in BALB/c nude mice. We also revealed the involvement of posttranscriptional regulation of IDO1 in colon cancer by observing IDO1 protein levels and mRNA levels. Furthermore, ectopic expression of miRNA mimics suggested that miR-448 could significantly downregulate IDO1 protein expression. Notably, we proved that miR-448 suppressed the apoptosis of CD8+ T cells by suppressing IDO1 enzyme function. CONCLUSION: Our findings indicated that IDO1 suppressed the CD8+ T cell response in colon cancer. miR-448, as a tumor-suppressive miRNA, enhanced the CD8+ T cell response by inhibiting IDO1 expression. The results provide a theoretical basis for the development of new immunotherapy for the treatment of colon cancer.

Exosomal transfer of p-STAT3 promotes acquired 5-FU resistance in colorectal cancer cells.

BACKGROUND: Acquired resistance remains a limitation of the clinical use of 5-fluorouracil (5-FU). Because exosomes, are important vesicles participating in intercellular communication, their contribution to the development of acquired 5-FU resistance needs to be elucidated. In this study, we aimed to examine the underlying mechanisms of exosomes from 5-FU resistant cells (RKO/R) in sustaining acquired 5-FU resistance in sensitive cells (RKO/P). METHODS: Exosomes from a 5-FU-resistant cell line (RKO/R) and its parental cell line RKO/P were isolated and co-cultured with 5-FU-sensitive cells. Real-time cellular analysis (RTCA) and FACS analysis were used to examine cell viability and apoptosis. Exosomal protein profiling was performed using shotgun proteomics. Inhibitors and siRNAs were applied to study the involvement of selected proteins in 5-FU resistance. The effect of exosomal p-STAT3 (Tyr705) on the caspase cascade was examined by western blotting (WB) and high content analysis. Xenograft models were established to determine whether exosomal p-STAT3 can induce 5-FU resistance in vivo. RESULTS: Our results indicated that exosomes from RKO/R cells significantly promoted cell survival during 5-FU treatment. Proteomics and WB analysis results indicated that GSTP1 and p-STAT3 (Tyr705) were enriched in exosomes from RKO/R cells. Inhibition of p-STAT3 re-sensitized RKO/P cells to 5-FU via caspase cascade. Furthermore, p-STAT3 packaged by exosomes from RKO/R cells increased resistance of tumor cells to 5-FU in vivo. CONCLUSIONS: Our results reveal a novel mechanism by which p-STAT3-containing exosomes contribute to acquired 5-FU resistance in CRC. This study suggests a new option for potentiating the 5-FU response and finding biomarkers for chemotherapy resistance.