Plasma large Tenascin-C spliced variant as a possible biomarker for the prediction of hepatic recurrence in colorectal cancer

Postoperative elevation in the plasma CCL2 level is a predictive biomarker of colorectal cancer recurrence

PURPOSE

There is currently no adequate biomarker for predicting colorectal cancer (CRC) recurrence. Chemokine (C-C motif) ligand 2 (CCL2) induces macrophages and fibroblasts to occupy metastatic niches in distant organs. The purpose of this study was to examine CCL2 as a potential predictive biomarker for CRC recurrence.

METHODS

Plasma samples (n = 402) were collected from 80 stage II/III/IV CRC cases and the relationship between CCL2 profiles and recurrence was investigated. The tumor immune response genes associated with CCL2 mRNA expression in a subgroup of 8 stage I/II CRC cases with 12 recurrent sites and The Cancer Genome Atlas database were also analyzed retrospectively.

RESULTS

Sixteen stage II/III/IV postoperative recurrent CRC cases experienced a significant increase in plasma CCL2 levels 6 months after surgery and continuously increased even after R0-1 resection. The 6-month postoperative CCL2 levels in recurrent cases of ≥ 1 year were significantly higher than in non-recurrent cases and recurrent cases of < 1 year. The CCL2 level in the primary tumor cases significantly correlated with the cytolytic activity, thus indicating a tumor immune response from the CD163-expressing macrophages.

CONCLUSION

Plasma CCL2 was found to be a predictive biomarker of postoperative CRC recurrence. CCL2 in metastatic sites derives from metastatic niches that surpass the host immune response.

Tenascin-C: Form versus function

Tenascin-C is a large, multimodular, extracellular matrix glycoprotein that exhibits a very restricted pattern of expression but an enormously diverse range of functions. Here, we discuss the importance of deciphering the expression pattern of, and effects mediated by, different forms of this molecule in order to fully understand tenascin-C biology. We focus on both post transcriptional and post translational events such as splicing, glycosylation, assembly into a 3D matrix and proteolytic cleavage, highlighting how these modifications are key to defining tenascin-C function.

Splicing factor SRSF6 promotes hyperplasia of sensitized skin

Many biological processes involve gene-expression regulation by alternative splicing. Here, we identify the splicing factor SRSF6 as a regulator of wound healing and tissue homeostasis in skin. We show that SRSF6 is a proto-oncogene that is frequently overexpressed in human skin cancer. Overexpressing it in transgenic mice induces hyperplasia of sensitized skin and promotes aberrant alternative splicing. We identify 139 target genes of SRSF6 in skin, and show that this SR protein binds to alternative exons of the extracellular-matrix protein tenascin C pre-mRNA, promoting the expression of isoforms characteristic of invasive and metastatic cancer in a cell-type-independent manner. SRSF6 overexpression additionally results in depletion of Lgr6+ stem cells, and excessive keratinocyte proliferation and response to injury. Furthermore, the effects of SRSF6 in wound healing assayed in vitro depend on the TNC isoforms. Thus, abnormal SR-protein expression can perturb tissue homeostasis.

Tenascin-W, a new marker of cancer stroma, is elevated in sera of colon and breast cancer patients

Tenascins are extracellular matrix proteins present during the development of organisms as well as in pathological conditions. Tenascin-W, the fourth and last member of the tenascin family remains the least well-characterized one. Our study aimed to evaluate the potential significance of tenascin-W as cancer biomarker by monitoring its presence in the serum of colorectal and breast cancer patients and its expression in colorectal tumor tissues. To measure serum tenascin-W levels, a sensitive sandwich-ELISA was established. Mean tenascin-W concentration in sera of patients with nonmetastatic colorectal cancer at time of diagnosis was highly increased compared to that of healthy volunteers. A similar tendency was observed for tenascin-C in the same patient cohort. However, the increase was much more striking for tenascin-W. We also detected elevated tenascin-W levels in sera of breast cancer patients. Furthermore, we could show a prominent expression of tenascin-W in extracts from colorectal tumor tissues by immunoblot analysis, whereas tenascin-W was not detectable in the corresponding normal colon mucosa. To confirm the western blot results, we performed immunohistochemistry of frozen sections of the same patients as well as of an additional, independently chosen collection of colorectal cancer tissues. In all cases, similarly to tenascin-C, tenascin-W was detected in the tumor stroma. Our results reveal a clear association between elevated levels of tenascin-W and the presence of cancer. These results warrant further studies to evaluate the potential value of serum and tissue tenascin-W levels as diagnostic, prognostic or monitoring biomarker in colorectal, breast and possibly other solid cancers.